Posted on by Matt Williams

What is the International Space Station?

The International Space Station orbiting Earth. Credit: NASA

After the historic Apollo Missions, which saw humans set foot on another celestial body for the first time in history, NASA and the Russian Space Agency (Roscosmos) began to shift their priorities away from pioneering space exploration and began to focus on developing long-term capabilities in space. In the ensuing decades (from the 1970s to 1990s), both agencies began to build and deploy space stations, each one bigger and more complex than the last.

The latest and greatest of these is the International Space Station (ISS), a scientific facility that resides in Low-Earth Orbit around our planet. This space station is the largest and most sophisticated orbiting research facility ever built and is so large that it can actually be seen with the naked eye. Central to its mission is the idea of fostering international cooperation for the sake of advancing science and space exploration.

Origin:

Planning for the ISS began in the 1980s and was based in part on the successes of Russia’s Mir space station, NASA’s Skylab, and the Space Shuttle Program. This station, it was hoped, would allow for the future utilization of  low-Earth Orbit and its resources, and serve as an intermediate base for renewed exploration efforts to the Moon, mission to Mars, and beyond.

The Mir space station hangs above the Earth in 1995 (photo taken by the mission crew of the Space Shuttle Atlantis, STS-71). Credit: NASA

In May of 1982, NASA established the Space Station task force, which was charged with creating a conceptual framework for such a space station. In the end, the ISS plan that emerged was a culmination of several different plans for a space station – which included NASA’s Freedom and the Soviet’s Mir-2 concepts, as well as Japan’s Kibo laboratory, and the European Space Agency’s Columbus laboratory.

The Freedom concept called for a modular space station to be deployed to orbit, where it would serve as the counterpart to the Soviet Salyut and Mir space stations. That same year, NASA approached the Japanese Aerospace and Exploration Agency (JAXA) to participate in the program with the creation of the Kibo, also known as the Japanese Experiment Module.

The Canadian Space Agency was similarly approached in 1982 and was asked to provide robotic support for the station. Thanks to the success of the Canadarm, which was an integral part of the Space Shuttle Program, the CSA agreed to develop robotic components that would assist with docking, perform maintenance, and assist astronauts with spacewalks.

In 1984, the ESA was invited to participate in the construction of the station with the creation of the Columbus laboratory – a research and experimental lab specializing in materials science. The construction of both the Kibo and Columbus modules was approved in 1985. As the most ambitious space program in either agency’s history, the development of these laboratories was seen as central to Europe and Japan’s emerging space capability.

Skylab, America’s First manned Space Station. Photo taken by departing Skylab 4 crew in Feb. 1974. Credit: NASA

In 1993, American Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin announced that they would be pooling the resources intended to create Freedom and Mir-2. Instead of two separate space stations, the programs would be working collaboratively to create a single space station – which was later named the International Space Station.

Construction:

Construction of the ISS was made possible with the support of multiple federal space agencies, which included NASA, Roscosmos, JAXA, the CSA, and members of the ESA – specifically Belgium, Denmark, France, Spain, Italy, Germany, the Netherlands, Norway, Switzerland, and Sweden. The Brazilian Space Agency (AEB) also contributed to the construction effort.

The orbital construction of the space station began in 1998 after the participating nations signed the Space Station Intergovernmental Agreement (IGA), which established a legal framework that stressed cooperation based on international law. The participating space agencies also signed the Four Memoranda of Understandings (MoUs), which laid out their responsibilities in the design, development, and use of the station.

The assembly process began in 1998 with the deployment of the ‘Zarya’ (“Sunrise” in Russian) Control Module, or Functional Cargo Block. Built by the Russians with funding from the US, this module was designed to provide the station’s initial propulsion and power. The pressurized module – which weighed over 19,300 kg (42,600 pounds) – was launched aboard a Russian Proton rocket in November 1998.

On Dec. 4th, the second component – the ‘Unity’ Node – was placed into orbit by the Space Shuttle Endeavour (STS-88), along with two pressurized mating adapters. This node was one of three – Harmony and Tranquility being the other two – that would form the ISS’ main hull. On Sunday, Dec. 6th, it was mated to Zarya by the STS-88 crew inside the shuttle’s payload bay.

The next installments came in the year 2000, with the deployment of the Zvezda Service Module (the first habitation module) and multiple supply missions conducted by the Space Shuttle Atlantis.  The Space Shuttle Discovery (STS-92) also delivered the station’s third pressurized mating adapted and a Ku-band antenna in October. By the end of the month, the first Expedition crew was launched aboard a Soyuz rocket, which arrived on Nov. 2nd.

In 2001, the ‘Destiny’ Laboratory Module and the ‘Pirs’ Docking Compartment were delivered. The modular racks that are part of Destiny were also shipped using the Raffaello Multi-Purpose Logistic Modules (MPLM) aboard the Space Shuttle Endeavour and put into place using the Canadarm2 robotic arm. In 2002, additional racks, truss segments, solar arrays, and the Mobile Base System for the Station’s Mobile Servicing System were all delivered.

In 2007, the European Harmony module was installed, which allowed for the addition of the Columbus and Kibo laboratories – both of which were added in 2008. Between 2009 and 2011, construction was finalized with the addition of the Russian Mini-Research Module-1 and -2 (MRM1 and MRM2), the ‘Tranquility’ Node, the Cupola Observation Module, the Leonardo Permanent Multipurpose Module, and the Robonaut 2 technology suite.

The structure of the ISS (exploded in this diagram) showing the various components and how they are assembled together. Credit: NASA

No additional modules or components were added until 2016 when Bigelow Aerospace installed their experimental Bigelow Expandable Activity Module (BEAM). All told, it took 13 years to construct the space station, an estimated $100 billion and required more than 100 rocket and Space Shuttle launches, and 160 spacewalks.

As of the penning of this article, the station has been continuously occupied for a period of 16 years and 74 days since the arrival of Expedition 1 on November 2nd, 2000. This is the longest continuous human presence in low Earth orbit, having surpassed Mir’s record of 9 years and 357 days.

Purpose and Aims:

The main purpose of the ISS is fourfold: conducting scientific research, furthering space exploration, facilitating education and outreach, and fostering international cooperation. These goals are backed by NASA, the Russian Federal Space Agency (Roscomos), the Japanese Aerospace Exploration Agency (JAXA), the Canadian Space Agency (CSA), and the European Space Agency (ESA), with additional support from other nations and institutions.

As far as scientific research goes, the ISS provides a unique environment to conduct experiments under microgravity conditions. Whereas crewed spacecraft provide a limited platform that is only deployed to space for a limited amount of time, the ISS allows for long-term studies that can last for years (or even decades).

Many different and continuous projects are being conducted aboard the ISS, which are made possible with the support of a full-time crew of six astronauts, and a continuity of visiting vehicles (which also allows for resupply and crew rotations). Scientists on Earth have access to their data and are able to communicate with the science teams through a number of channels.

The many fields of research conducted aboard the ISS include astrobiology, astronomy, human research, life sciences, physical sciences, space weather, and meteorology. In the case of space weather and meteorology, the ISS is in a unique position to study these phenomena because of its position in LEO. Here, it has a short orbital period, allowing it to witness weather across the entire globe many times in a single day.

It is also exposed to things like cosmic rays, solar wind, charged subatomic particles, and other phenomena that characterize a space environment. Medical research aboard the ISS is largely focused on the long-term effects of microgravity on living organisms – particularly its effects on bone density, muscle degeneration, and organ function – which is intrinsic to long-range space exploration missions.

The ISS also conducts research that is beneficial to space exploration systems. Its location in LEO also allows for the testing of spacecraft systems that are required for long-range missions. It also provides an environment where astronauts can gain vital experience in terms of operations, maintenance, and repair services – which are similarly crucial for long-term missions (such as missions to the Moon and Mars).

The ISS also provides opportunities for education thanks to participation in experiments, where students are able to design experiments and watch as ISS crews carry them out. ISS astronauts are also able to engage classrooms through video links, radio communications, email, and educational videos/web episodes. Various space agencies also maintain educational materials for download based on ISS experiments and operations.

Educational and cultural outreach also fall within the ISS’ mandate. These activities are conducted with the help and support of the participating federal space agencies and are designed to encourage education and career training in the STEM (Science, Technical, Engineering, Math) fields.

One of the best-known examples of this is the educational videos created by Chris Hadfield – the Canadian astronaut who served as the commander of Expedition 35 aboard the ISS – which chronicled the everyday activities of ISS astronauts. He also directed a great deal of attention to ISS activities thanks to his musical collaboration with the Barenaked Ladies and Wexford Gleeks – titled “I.S.S. (Is Somebody Singing)” (shown above).

His video, a cover of David Bowie’s “Space Oddity”, also earned him widespread acclaim. Along with drawing additional attention to the ISS and its crew operations, it was also a major feat since it was the only music video ever to be filmed in space!

Operations Aboard the ISS:

As noted, the ISS is facilitated by rotating crews and regular launches that transport supplies, experiments, and equipment to the station. These take the form of both crewed and uncrewed vehicles, depending on the nature of the mission. Crews are generally transported aboard Russian Progress spacecraft, which are launched via Soyuz rockets from the Baikonur Cosmodrome in Kazakhstan.

Roscosmos has conducted a total of 60 trips to the ISS using Progress spacecraft, while 40 separate launches were conducted using Soyuz rockets. Some 35 flights were also made to the station using the now-retired NASA Space Shuttles, which transported crew, experiments, and supplies. The ESA and JAXA have both conducted 5 cargo transfer missions, using the Automated Transfer Vehicle (ATV) and the H-II Transfer Vehicle (HTV), respectively.

In more recent years, private aerospace companies like SpaceX and Orbital ATK have been contracted to provide resupply missions to the ISS, which they have done using their Dragon and Cygnus spacecraft. Additional spacecraft, such as SpaceX’s Crew Dragon spacecraft, are expected to provide crew transportation in the future.

Alongside the development of reusable first-stage rockets, these efforts are being carried out in part to restore domestic launch capability to the US. Since 2014, tensions between the Russian Federation and the US have led to growing concerns over the future of Russian-American cooperation with programs like the ISS.

Crew activities consist of conducting experiments and research considered vital to space exploration. These activities are scheduled from 06:00 to 21:30 hours UTC (Universal Coordinated Time), with breaks being taken for breakfast, lunch, dinner, and regular crew conferences. Every crew member has their own quarters (which includes a tethered sleeping bag), two of which are located in the Zvezda Module and four more installed in Harmony.

During “night hours”, the windows are covered to give the impression of darkness. This is essential since the station experiences 16 sunrises and sunsets a day. Two exercise periods of 1 hour each are scheduled every day to ensure that the risks of muscle atrophy and bone loss are minimized. The exercise equipment includes two treadmills, the Advanced Resistive Exercise Device (ARED) for simulated weight training, and a stationary bicycle.

Hygiene is maintained thanks to water jets and soap dispensed from tubes, as well as wet wipes, rinseless shampoo, and edible toothpaste. Sanitation is provided by two space toilets – both of Russian design – aboard the Zvezda and Tranquility Modules. Similar to what was available aboard the Space Shuttle, astronauts fasten themselves to the toilet seat and the removal of waste is accomplished with a vacuum suction hole.

Liquid waste is transferred to the Water Recovery System, where it is converted back into drinking water (yes, astronauts drink their own urine, after a fashion!). Solid waste is collected in individual bags that are stored in an aluminum container, which are then transferred to the docked spacecraft for disposal.

Food aboard the station consists mainly of freeze-dried meals in vacuum-sealed plastic bags. Canned goods are available, but are limited due to their weight (which makes them more expensive to transport). Fresh fruit and vegetables are brought during resupply missions, and a large array of spices and condiments are used to ensure that food is flavorful – which is important since one of the effects of microgravity is a diminished sense of taste.

To prevent spillage, drinks and soups are contained in packets and consumed with a straw. Solid food is eaten with a knife and fork, which are attached to a tray with magnets to prevent them from floating away, while drinks are provided in dehydrated powder form and then mixed with water. Any food or crumbs that floats away must be collected to prevent them from clogging the air filters and other equipment.

Hazards:

Life aboard the station also carries with it a high degree of risk. These come in the form of radiation, the long-term effects of microgravity on the human physique, the psychological effects of being in space (i.e. stress and sleep disturbances), and the danger of collision with space debris.

In terms of radiation, objects within the Low-Earth Orbit environment are partially protected from solar radiation and cosmic rays by the Earth’s magnetosphere. However, without the protection of the Earth’s atmosphere, astronauts are still exposed to about 1 millisievert a day, which is the equivalent of what a person on Earth is exposed to during the course of a year.

As a result, astronauts are at higher risk for developing cancer, suffering DNA and chromosomal damage, and diminished immune system function. Hence why protective shielding and drugs are a must aboard the station, as well as protocols for limiting exposure. For instance, during solar flare activity, crews are able to seek shelter in the more heavily shielded Russian Orbital Segment of the station.

As already noted, the effects of microgravity also take a toll on muscle tissues and bone density. According to a 2001 study conducted by NASA’s Human Research Program (HRP) – which researched the effects on an astronaut Scott Kelly’s body after he spent a year aboard the ISS – bone density loss occurs at a rate of over 1% per month.

Similarly, a report by the Johnson Space Center – titled “Muscle Atrophy” – stated that astronauts experience up to a 20% loss of muscle mass on spaceflights lasting just five to 11 days. In addition, more recent studies have indicated that the long-term effects of being in space also include diminished organ function, decreased metabolism, and reduced eyesight.

Because of this, astronauts exercise regularly in order to minimize muscle and bone loss, and their nutritional regimen is designed to make sure they the appropriate nutrients to maintain proper organ function. Beyond that, the long-term health effects, and additional strategies to combat them, are still being investigated.

But perhaps the greatest hazard comes in the form of orbiting junk – aka. space debris. At present, there are over 500,000 pieces of debris that are being tracked by NASA and other agencies as they orbit the Earth. An estimated 20,000 of these are larger than a softball, while the remainder are about the size of a pebble. All told, there are likely to be many millions of pieces of debris in orbit, but most are so small they can’t be tracked.

These objects can travel at speeds of up to 28,163 km/h (17,500 mph), while the ISS orbits the Earth at a speed of 27,600 km/h (17,200 mph). As a result, a collision with one of these objects could be catastrophic to the ISS. The station is naturally shielded to withstand impacts from tiny bits of debris and well as micro-meteoroids – and this shielding is divided between the Russian Orbital Segment and the US Orbital Segment.

On the USOS, the shielding consists of a thin aluminum sheet that is held apart from the hull. This sheet causes objects to shatter into a cloud, thereby dispersing the kinetic energy of the impact before it reaches the main hull. On the ROS, shielding takes the form of a carbon plastic honeycomb screen, an aluminum honeycomb screen, and glass cloth, all of which are spaced over the hull.

The ROS’ shielding is less likely to be punctured, hence why the crew moves to the ROS whenever a more serious threat presents itself. But when faced with the possibility of an impact from a larger object that is being tracked, the station performs what is known as a Debris Avoidance Manoeuvre (DAM). In this event, the thrusters on the Russian Orbital Segment fire in order to alter the station’s orbital altitude, thus avoiding the debris.

Future of the ISS:

Given its reliance on international cooperation, there have been concerns in recent years – in response to growing tensions between Russia, the United States, and NATO – about the future of the International Space Station. However, for the time being, operations aboard the station are secure, thanks to commitments made by all of the major partners.

In January of 2014, the Obama Administration announced that it would be extending funding for the US portion of the station until 2024. Roscosmos has endorsed this extension but has also voiced approval for a plan that would use elements of the Russian Orbital Segment to construct a new Russian space station.

Known as the Orbital Piloted Assembly and Experiment Complex (OPSEK), the proposed station would serve as an assembly platform for crewed spacecraft traveling to the Moon, Mars, and the outer Solar System. There have also been tentative announcements made by Russian officials about a possible collaborative effort to build a future replacement for the ISS. However, NASA has yet to confirm these plans.

In April of 2015, the Canadian government approved a budget that included funding to ensure the CSA’s participation with the ISS through 2024. In December of 2015, JAXA and NASA announced their plans for a new cooperative framework for the International Space Station (ISS), which included Japan extending its participation until 2024. As of December 2016, the ESA has also committed to extending its mission to 2024.

The ISS represents one of the greatest collaborative and international efforts in history, not to mention one of the greatest scientific undertakings. In addition to providing a location for crucial scientific experiments that cannot be conducted here on Earth, it is also conducting research that will help humanity make its next great leaps in space – i.e. mission to Mars and beyond!

On top of all that, it has been a source of inspiration for countless millions who dream of going to space someday! Who knows what great undertakings the ISS will allow for before it is finally decommissioned – most likely decades from now?

We have written many interesting articles about the ISS here at Universe Today. Here’s International Space Station Achieves 15 Years of Continuous Human Presence in Orbit, Beginner’s Guide to Seeing the International Space Station, Take a Virtual 3-D Spacewalk Outside the International Space Station, International Space Station Viewing, and Space Station Pictures.

For more information, check out the NASA Reference Guide to the ISS and this article about the 10th anniversary of the space station.

Astronomy Cast also has relevant episodes on the subject. Here’s Questions: An Unlocked Moon, Energy Into Black Holes, and the Space Station’s Orbit, and Episode 298: Space Stations, Part 3 – International Space Station.

Sources:

Posted on by Matt Williams

Exploding Binary Stars Will Light Up the Sky in 2022

Artist’s impression of the VFTS 352 star system, the hottest and most massive double star system to date where the two components are in contact and sharing material. Credit: ESO/L. Calçada

Stellar collisions are an amazingly rare thing. According to our best estimates, such events only occur in our galaxy (within globular clusters) once every 10,000 years. It’s only been recently, thanks to ongoing improvements in instrumentation and technology, that astronomers have been able to observe such mergers taking place. As of yet, no one has ever witnessed this phenomena in action – but that may be about to change!

According to study from a team of researchers from Calvin College in Grand Rapids, Michigan, a binary star system that will likely merge and explode in 2022. This is an historic find, since it will allow astronomers to witness a stellar merger and explosion for the first time in history. What’s more, they claim, this explosion will be visible with the naked-eye to observers here on Earth.

The findings were presented last week at the 229th Meeting of the American Astronomical Society (AAS). In a presentation titled “A Precise Prediction of a Stellar Merger and Red Nova Outburst“, Professor Lawrence Molnar and his team shared findings that indicate how this binary pair will merge in about six years time. This event, they claim, will cause an outburst of light so bright that it will become the brightest object in the night sky.

Professor Lawrence Molnar of the Calvin College’s Dept. of Physics and Astronomy. He predicts KIC 9832227 will collide and explode in 2022. Credit: calvin.edu

This binary star system, which is known as KIC 9832227, is one that Prof. Molnar and his colleagues – which includes students from the Apache Point Observatory and the University of Wyoming – have been monitoring since 2013. His interest in the star was piqued during a conference in 2013 when Karen Kinemuchi (an astronomers with the Apache Point Observatory) presented findings about brightness changes in the star.

This led to questions about the nature of this star system – specifically, whether it was a pulsar or a binary pair. After conducting their own observations using the Calvin observatory, Prof. Molnar and his colleagues concluded that the star was a  contact binary – a class of binary star where the two stars are close enough to share an atmosphere. This brought to mind similar research in the past about another binary star system known as V1309 Scorpii.

This binary pair also had a shared atmosphere; and over time, their orbital period kept decreasing until (in 2008) they unexpectedly collided and exploded. Believing that KIC 9832227 would undergo a similar fate, they began conducting tests to see if the star system was exhibiting the same behavior. The first step was to make spectroscopic observations to see if their observations could be explained by the presence of a companion star.

As Cara Alexander, a Calvin College student and one of the co-authors on the team’s research paper, explained in a college press release:

“We had to rule out the possibility of a third star. That would have been a pedestrian, boring explanation. I was processing data from two telescopes and obtained images that showed a signature of our star and no sign of a third star. Then we knew we were looking at the right thing. It took most of the summer to analyze the data, but it was so exciting. To be a part of this research, I don’t know any other place where I would get an opportunity like that; Calvin is an amazing place.”

Diagram showing the summer constellations of Cygnus and Lyra and the position of KIC 9832227 (shown with a red circle). Credit: calvin.edu

The next step was to measure the pair’s orbital period, to see it was in fact getting shorter over time – which would indicate that the stars were moving closer to each other. By 2015, Prof. Molnar and his team determined that the stars would eventually collide, resulting in a kind of stellar explosion known as a “Red Nova”. Initially, they estimated this would take place between 2018 and 2020, but have since placed the date at 2022.

In addition, they predict that the burst of light it will cause will be bright enough to be seen from Earth. The star will be visible as part of the constellation Cygnus, and it appear as an addition star in the familiar Northern Cross star pattern (see above). This is an historic case, since no astronomer has ever been able to accurately predict when and where a stellar collision would take place in the past.

What’s more, this discovery is immensely significant because it represents a break with the traditional discovery process. Not only have small research institutions and universities not been the ones to take the lead on these sorts of discoveries in the past, but student-and-teacher teams have also not been the ones who got to make them. As Molnar explained it:

“Most big scientific projects are done in enormous groups with thousands of people and billions of dollars. This project is just the opposite. It’s been done using a small telescope, with one professor and a few students looking for something that is not likely. Nobody has ever predicted a nova explosion before. Why pay someone to do something that almost certainly won’t succeed? It’s a high-risk proposal. But at Calvin it’s only my risk, and I can use my work on interesting, open-ended questions to bring extra excitement into my classroom. Some projects still have an advantage when you don’t have as much time or money.”

The model Prof. Molnar and his team constructed of the double star system KIC 9832227, which is a contact binary (i.e. two stars that are touching). Credit: calvin.edu.

Over the course of the next year, Molnar and his colleagues will be monitoring KIC 9832227 carefully, and in multiple wavelengths. This will be done with the help of the NROA’s Very Large Array (VLA), NASA’s Infrared Telescope Facility at Mauna Kea, and the ESA’s XMM-Newton spacecraft. These observatories will study the star’s radio, infrared and X-ray emissions, respectively.

Molnar also expects that amateur astronomers will be able to monitor the pair’s orbital timing and variations in brightness. And if he and his team’s predictions are correct, every student and stargazer in the northern hemisphere – not to mention people who just happen to be out for a walk – will be privy to the amazing light show. This is sure to be a once-in-a-lifetime event, so stay tuned for more information!

Interestingly enough, this historic discovery is also the subject of a documentary film. Titled “Luminous“, the documentary – which is directed by Sam Smartt, a Calvin professor of communication arts and sciences – chronicles the process that led Prof. Molnar and his team to make this unprecedented discovery. The documentary will also include footage of the Red Nova as it happens in 2022, and is expected to be released sometime in 2023.

Check out the trailer below:

Further Reading: Calvin College, Science Mag

Posted on by Matt Williams

Hubble Spots Possible Exocomets in Nearby Star System

Artist's impression of comets plunging into the star HD 172555, which was observed using the Hubble Space Telescope. Credit: hubblesite.org

The Hubble Space Telescope is a workhorse which, despite its advanced years, keeps on producing valuable scientific data. In addition to determining the rate at which the Universe is expanding, spotting very distant galaxies, and probing the early history of the Universe, it has also observed some truly interesting things happening in nearby star systems.

For example, Hubble recently spotted some unusual activity in HD 172555, a star system located about 95 light-years from Earth. Here, Hubble obtained spectral information that indicated the presence of comets that appeared to be falling into the star. This could prove useful to scientists who are looking to understand how comets behaved during the early history of the Solar System.

These findings were presented at the 229th Meeting of the American Astronomical Society (AAS), which has been taking place this past week in Grapevine, Texas. During the course of the presentation, Dr. Carol Grady of Eureka Scientific Inc. and NASA’s Goddard Space Flight Center, shared Hubble data that hinted at the presence of infalling comets, a finding which could bolster theories about what is known as “gravitational stirring”.

Artist’s concept of a collision that is believed to have taken place in the HD 172555 star system between a moon-sized object and a Mercury-sized planet. Credit: NASA/JPL-Caltech

Basically, this theory states that the presence of a Jupiter-size planet in a star system will lead to comets being deflected by its massive gravity, thus sending them into the star. This phenomena is associated with younger stars, and is believed to have taken place in our own Solar System billions of years ago – which also led to number of comets being diverted towards Earth.

The detection of infalling comets in this system (and the way it bolsters the theory of gravitational stirring) is of imminence significant, since it is believed that it was this very mechanism that transported water to Earth when it was quite young. By observing how comets behave around young stars like HD 172555, which is estimated to be around 40 million years old, astronomers are able to see just how this mechanism could work.

As Carol Grady explained in a Hubble press release:

“Seeing these sun-grazing comets in our solar system and in three extrasolar systems means that this activity may be common in young star systems. This activity at its peak represents a star’s active teenage years. Watching these events gives us insight into what probably went on in the early days of our solar system, when comets were pelting the inner solar system bodies, including Earth. In fact, these star-grazing comets may make life possible, because they carry water and other life-forming elements, such as carbon, to terrestrial planets.”

And while exocomets are far too small to be observed directly, the research team – which included members from the European Space Agency, the Kapteyn Institute, NASA Goddard Space Flight Center, and the University of Colorado – were able to discern their presence in 2015 using data obtained by Hubble’s Space Telescope Imaging Spectrograph (STIS) and the Cosmic Origins Spectrograph (COS).

Artist’s concept of circumstellar disk of debris, which the HD 172555 star system is known to have. Credit: NASA

Over the course of six days of observation, Hubble’s instruments detected silicon and carbon gas in the ultraviolet wavelength. The source of these gases also appeared to be moving at a speed of over 579,360 km (360,000 mph) across the face of the star. The only viable explanation for this was that they were spotting trails of gas as they evaporated from comets as they made their way across the system’s debris disk and closer to the star.

This is not the first time that exocomets have been seen transiting HD 172555. In 2004 and 2011, similar detections were made by the European Southern Observatory’s High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. On those occasions, HARPS detected spectra that indicated the presence of calcium, which was seen as evidence that comet-like objects were falling into the star.

Dr. Grady and her team followed up on this by conducting their own spectral analysis of the system. By viewing HD 172555 and its debris disk in ultraviolet light, they were able to discern the presence of silicon and carbon. This was made easier thanks to the fact that HD 172555’s debris disk is viewed close to edge-on, which gives the telescope a clear view of any comet activity taking place within it.

Dr. Grady admits that there are still some uncertainties with their study. For instance, it is not entirely clear whether the objects they observed were comets or asteroids. Though the behavior is consistent with comets, more data on their particular compositions will be needed before they can be sure.

But in the meantime, it is compelling evidence for how comets behaved during the early history of the Solar System. And it may lend weight to the debate about how water originated on Earth, which is also central to determining how and where life may emerge in other parts of the Universe.

Further Reading: Hubble Space Telescope

Posted on by Matt Williams

What is Low Earth Orbit?

Artist's impression of debris in low Earth orbit. Credit: ESA

Beginning in the 1950s with the Sputnik, Vostok and Mercury programs, human beings began to “slip the surly bonds of Earth”. And for a time, all of our missions were what is known as Low-Earth Orbit (LEO). Over time, with the Apollo missions and deep space missions involving robotic spacecraft (like the Voyager missions), we began to venture beyond, reaching the Moon and other planets of the Solar System.

But by and large, the vast majority of missions to space over the years – be they crewed or uncrewed – have been to Low-Earth Orbit. It is here that the Earth’s vast array of communications, navigation and military satellites reside. And it is here that the International Space Station (ISS) conducts its operations, which is also where the majority of crewed missions today go. So just what is LEO and why are we so intent on sending things there? Continue reading “What is Low Earth Orbit?”

Posted on by Matt Williams

Could Garnet Planets be Habitable?

A new study based on data from Sloan Digital Sky Survey (SDSS) shows how certain exoplanets are dominated by minerals like olivine and garnet. Credit: NASA

The hunt for exoplanet has revealed some very interesting things about our Universe. In addition to the many gas giants and “Super-Jupiters” discovered by mission like Kepler, there have also been the many exoplanet candidate that comparable in size and structure to Earth. But while these bodies may be terrestrial (i.e. composed of minerals and rocky material) this does not mean that they are “Earth-like”.

For example, what kind of minerals go into a rocky planet? And what could these particular compositions mean for the planet’s geological activity, which is intrinsic to planetary evolution? According to new study produced by a team of astronomers and geophysicists, the composition of an exoplanet depends on the chemical composition of its star – which can have serious implications for its habitability.

The findings of this study were presented at the 229th Meeting of the American Astronomical Society (AAS), which will be taking place from Jan. 3rd to Jan. 7th. During an afternoon presentation – titled “Between a Rock and a Hard Place: Can Garnet Planets Be Habitable?” – Johanna Teske (an astronomer from the Carnegie Institute of Science)  showed how different types of stars can produce vastly different types of planets.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), which collects spectrographic information on distant stars. Credit: astronomy.as.virginia.edu

Using the Apache Point Observatory Galactic Evolution Experiment (APOGEE), which is part of the Sloan Digital Sky Survey (SDSS) Telescope at Apache Point Observatory, they examined spectrographic information obtained from 90 star systems – which were also observed by the Kepler Mission. These systems are of particular interest to exoplanet hunters because they have been shown to contain rocky planets.

As Teske explained during the course of the presentation, this information could help scientists to place further constraints on what it takes for a planet to be habitable. “[O]ur study combines new observations of stars with new models of planetary interiors,” she said. “We want to better understand the diversity of small, rocky exoplanet composition and structure — how likely are they to have plate tectonics or magnetic fields?”

Focusing on two star systems in particular – Kepler 102 and Kepler 407 – Teske demonstrated how the composition of a planet has a great deal to do with the composition of its star. Whereas Kepler 102 has five known planets, Kepler 407, has two different planets – one gaseous and the other terrestrial. And while Kepler 102 is quite similar to our Sun (slightly less luminous), Kepler 407 has close to the same mass (but a lot more silicon).

In order to understand what consequences these differences could have for planetary formation, the SDSS team turned to a team of geophysicists. Led by Cayman Unterborn from Arizona State University, this team ran computer models to see what kinds of planets each system would have. As Unterborn explained:

“We took the star compositions found by APOGEE and modeled how the elements condensed into planets in our models. We found that the planet around Kepler 407, which we called ‘Janet,” would likely be rich in the mineral garnet. The planet around Kepler 102, which we called ‘Olive,’ is probably rich in olivine, like Earth.”

Artist rendition of interior compositions of planets around the stars Kepler 102 and Kepler 407. Credit: Robin Dienel/Carnegie DTM

This difference would have considerable impact on planetary tectonics. For one, garnet is lot more rigid than olivine, which would mean “Janet” would experience less in the way of long-term plate tectonics. This in turn would mean that processes that are believed to be essential to life on Earth – like volcanic activity, atmospheric recycling, and mineral exchanges between the crust and mantle – would be less common.

This raises additional questions about the habitability of “Earth-like” planets in other star systems. In addition to being rocky and having strong magnetic fields and viable atmospheres, it seems that exoplanets also need to have the right mix of minerals in order to support life – life as we know it, at any rate. What’s more, this kind of research also helps us to understand how life came to emerge on Earth in the first place.

Looking forward, the research team hopes to extend their study to include all the 200,000 stars surveyed by APOGEE to see which could host terrestrial planets. This will allow astronomers to determine the mineral composition of more rocky worlds, thus helping them to determine which rocky exoplanets are “Earth-like”, and which are just “Earth-sized”.

Further Reading: SDSS

Posted on by Matt Williams

Chandra Spots Two Cosmic Heavy-Hitters at Once

Composite view of the collision between galaxy clusters Abell 3411 and Abell 3412 . Credit: X-ray: NASA/CXC/SAO/R. van Weeren et al./NAOJ/Subaru

This week, the 229th Meeting of the American Astronomical Society (AAS) kicked off in Grapevine, Texas. Between Monday and Friday (January 3rd to January 7th), attendees will be hearing presentations by researchers and scientists from several different fields as they share the latest discoveries in astronomy and Earth science.

One of the highlights so far this week was a presentation from NASA’s Chandra X-ray Observatory, which took place on the morning of Wednesday, January 5th. In the course of the presentation, an international research team showed some stunning images of two of the most powerful cosmic forces seen together for the first time – a supermassive black hole and two massive galaxy clusters colliding.

The galaxy clusters are known as Abell 3411 and Abell 3412, which are located about two billion light years from Earth. Both of these clusters are quite massive, each possessing the equivalent of about a quadrillion times the mass of our Sun. Needless to say, the collision of these objects produced quite the shockwave, which included the release of hot gas and energetic particles.

X-ray image of the collision between Abell 3411 and Abell 3412. Credit: NASA/CXC/SAO/R. van Weeren et al.

This was made all the more impressive thanks to the presence of a supermassive black hole (SMBH) at the center of one of the galaxy clusters. As the team described in their paper – titled “The Case for Electron Re-Acceleration at Galaxy Cluster Shocks” – the galactic collision produced a nebulous outburst of x-rays (shown above), which were produced when hot clouds of gas from one cluster plowed through the hot gas clouds of the other.

Meanwhile, the inflowing gas was accelerated outward into a jet-like stream, thanks to the powerful electromagnetic fields of the SMBH. These particles were accelerated even further when they got swept up by the shock waves produced by the collision of the galactic clusters and their massive gas clouds. These streams were detected thanks to the burst of radio waves they released as a result.

By seeing these two major events happening at the same time in the same place, the research team effectively witnessed a cosmic “double whammy”. As Felipe Andrade-Santos of the Harvard-Smithsonian Center for Astrophysics (CfA), and co-author of the paper, described it in a Chandra press release:

“It’s almost like launching a rocket into low-Earth orbit and then getting shot out of the Solar System by a second rocket blast. These particles are among the most energetic particles observed in the Universe, thanks to the double injection of energy.”

Image of radio waves produce by the collision between Abell 3411 and Abell 3412. Credit: NASA/CXC/SAO/R. van Weeren et al.

Relying on data obtained from the Chandra X-ray Observatory, the Giant Metrewave Radio Telescope (GMRT) in India, the Karl G. Jansky Very Large Array, the Keck Observatory, and Japan’s Subaru Telescope, the team was able to capture this event in the optical, x-ray, and radio wave wavelengths. This not only led to some stunning images, but shed some light on a long-standing mystery in galaxy research.

In the past, astronomers have detected radio emissions coming from Abell 3411 and Abell 3412 using the GMRT. But the origins of these emissions, which reached for millions of light years, was the subject of speculation and debate. Relying on the data they obtained, the research team was able to determine that they are the result of energetic particles (produced by the clouds of hot gas colliding) being further accelerated by galactic shock waves.

Or as co-author William Dawson, of the Lawrence Livermore National Lab in Livermore, California, put it:

“This result shows that a remarkable combination of powerful events generate these particle acceleration factories, which are the largest and most powerful in the Universe. It is a bit poetic that it took a combination of the world’s biggest observatories to understand this.”

Many interesting finds have been shared since the 229th Meeting of the AAS began – like the hunt for the source of a Fast Radio Burst – and many more are expected before it wraps up at the end of the week. These will include the latest results from the Sloan Digital Sky Survey (SDSS), and new and exciting research on black holes, exoplanets, and other astronomical phenomena.

And be sure to check out this podcast from Chandra as well, which talks about the collision between Abell 3411 and 3412 and the cosmic forces it unleashed.

Further Reading: Chandra X-ray Observatory

Posted on by Matt Williams

NASA Announces Missions to Explore Early Solar System

An artist’s conception of the Lucy spacecraft (left) flying by the Trojan Eurybates, and Psyche (Right) Psyche, the first mission to the metal world 16 Psyche. Credits: SwRI and SSL/Peter Rubin

It’s a New Year, with new challenges and new opportunities! And NASA, looking to kick things off, has announced the two new missions that will be launching in the coming decade. These robotic missions, named Lucy and Psyche, are intended to help us understand the history of the early Solar System, and will deploy starting in 2021 and 2023, respectively.

While Lucy’s mission is to explore one of Jupiter’s Trojan asteroids, Psyche will explore a metal asteroid known as 16 Psyche. And between the two of them, it is hoped that they will answer some enduring questions about planetary formation and how the Solar System came to be. More than that, these mission represent historic firsts for NASA and human space exploration.

NASA’s Discovery Program, of which Lucy and Psyche are part, was created in 1992 to compliment their larger “flagship” programs. By bringing scientists and engineers together to design missions, the Discovery Program’s focus has been to maximize scientific research by creating many smaller missions that have shorter development periods and require less in the way of operational resources.

Artist’s concept of the Lucy spacecraft flying by Eurybates, one of the six diverse and scientifically important Trojans it will study. Credit: SwRI

The Lucy mission is scheduled to launch in October of 2021, and is expected to arrive at its first destination (a Main Belt asteroid) in 2025. It will then set course for Jupiter’s Trojans, a group of asteroids that are trapped by Jupiter’s gravity and share its orbit. These asteroids are thought to be relics of the early Solar System; and between 2027 and 2033, Lucy will study six of them.

In addition to being the first mission to explore Jupiter’s Trojan population, Lucy is also of historic importance because of the number of asteroids it will visit. Throughout the course of its mission, it is will investigate six Trojans, which is the total number of Main Belt asteroids that have been studied to date. The nature of these six asteroids is also expected to tell us much about the early history of the Solar System.

As Harold F. Levison – the principal investigator of the Lucy mission from the Southwest Research Institute (SwRI) in Boulder, Colorado – explained during a NASA call-in briefing:

“One of the surprising aspects of this population is their diversity. If we look at them through telescopes on the Earth, we see that they are very different from one other in their color, in their spectra. And so, we believe that’s telling us something about how the Solar System formed and evolved… This diversity in these objects, we believe, are due to the fact that they actually formed in very different regions of the Solar System, with very different physical characteristics. And something occurred in the history of the Solar System where these objects started off at very different distances, but during the formation and evolution of the Solar System, they got moved around and placed in these stable reservoirs near Jupiter’s orbit.”

Illustration of the Lucy spacecraft’s orbit around Jupiter, which will allow it to study its Trojan population. Credit: SwRI

The six Trojans that Lucy is intended investigate were selected because the diversity of their physical characteristics show that they are from different locations throughout the Solar System. As Levison put it, “These small bodies really are the fossils of planet formation, and that’s why we named Lucy after the human ancestor known as Lucy.”

In addition, Lucy will build on the success of missions like New Horizons and OSIRIS-REx., which includes using updated versions of instruments they used to explore Pluto, the Kuiper Belt, and the asteroid Bennu -i.e. the RALPH and LORRI instruments and the OTES instrument. In addition, several members of the New Horizons and OSIRIS-REx science teams will be lending their expertise to the Lucy mission.

Similarly, the Psyche mission will of be immense scientific value since it will visit the only metal asteroid known to exist. This asteroid measures about 210 km (130 mi) in diameter and is believed to be composed entirely of iron and nickel. In this respect, it is similar to Earth’s metallic core, as well as the cores of every terrestrial planet in the Solar System.

It is for this reason why scientists believe it may be the exposed core of a Mars-sized planet. According to this theory, 16 Psyche experienced several major collisions during the early history of the Solar System, which caused it to shed its rocky mantle. The robotic probe will launch in 2023 and is expected to arrive by 2030 – after receiving an Earth gravity-assist maneuver in 2024 and a Mars flyby in 2025.

By measuring its composition, magnetic field, and mapping its surface features, Lucy’s science team hopes to learn more about the history of planetary formation. As Lindy Elkins-Tanton – the Principal Investigator of Psyche and the Director of the School of Earth and Space Exploration at Arizona State University – said during the NASA call-in briefing:

“Humankind has visited rocky worlds and icy worlds and worlds made of gas. But we have never seen a metal world. Psyche has never been visited or had a picture taken that was more than a point of light. And so, its appearance remains a mystery. This mission will be true exploration and discovery. We think that Psyche is the metal core of a small planet that was destroyed in the high-energy, high-speed, first one-one-hundredth of the age of our Solar System. By visiting Psyche we can literally visit a planetary core the only way humanity can… Psyche let’s us visit inner space by visiting outer space.”

Not only are planetary cores thought to be where magnetic fields originate (which are necessary for the emergence of life), but they are entirely inaccessible to us. The very edge of Earth’s outer core is roughly 2,890 km (1790 mi) from our planet’s surface. But the deepest humanity has ever dug has been to a depth of 12 km (7.5 mi), which took place at the Kola Superdeep Borehole, in Russia.

In addition, within the Earth’s core, temperature and pressure conditions are estimated to reach 5700 K (5400 °C; 9752 °F) and 330 to 360 gigapascals (over three million times normal air pressure). This makes exploring the core of our planet (or any other planet in the Solar System, for that matter) completely impractical. Hence why a robotic mission to a world like Pysche is such an opportunity.

And since Psyche is the only rounded body of metal that is known to exist in the Solar System, the asteroid is as improbably as it is unique. And since no missions have ever taken place to explore its surface, and no pictures exist that can tell us what its surface features would look like, the Psyche mission is sure to shed some serious light on what a metal world looks like.

“What do we think it might look like?” asked Tanton. “Does it have surface sulfur lava flows on its surface? Is it covered with towering cliffs created when solidifying metal shrank and the exterior of the body broke into fault? Is its surface a combination of iron metal and green mineral crystal as iron meteorites are? And what does an impact crater in metal look like? Could its edges or its metal flashes become frozen in the cold of space before they fell back on the surface. We don’t know.”

Jim Green, NASA’s Planetary Science Director, expressed enthusiasm for the Discovery 13 and 14 missions in a recent NASA press release:

“These are true missions of discovery that integrate into NASA’s larger strategy of investigating how the solar system formed and evolved. We’ve explored terrestrial planets, gas giants, and a range of other bodies orbiting the sun. Lucy will observe primitive remnants from farther out in the solar system, while Psyche will directly observe the interior of a planetary body. These additional pieces of the puzzle will help us understand how the sun and its family of planets formed, changed over time, and became places where life could develop and be sustained – and what the future may hold.”

Lucy and Psyche were chosen from five finalists that were selected for further development back in September 2015. These in turn were chosen from 27 mission concepts that were submitted back in November of 2014. Examples of past and present Discovery missions include the Kepler space probe, the Dawn spacecraft, the Mars Pathfinder, and the InSight lander (which is scheduled to launch in 2018).

Further Reading: NASA

Posted on by Matt Williams

What is the Closest Galaxy to the Milky Way?

Image showing nearly 50,000 galaxies in the nearby universe detected by the Two Micron All Sky Survey (2MASS) in infrared light. Credit: 2MASS/ T. H. Jarrett/J. Carpenter/R. Hurt

Scientists have known for some time that the Milky Way Galaxy is not alone in the Universe. In addition to our galaxy being part of the Local Group – a collection of 54 galaxies and dwarf galaxies – we are also part of the larger formation known as the Virgo Supercluster. So you could say the Milky Way has a lot of neighbors.

Of these, most people consider the Andromeda Galaxy to be our closest galactic cohabitant. But in truth, Andromeda is the closest spiral galaxy, and not the closest galaxy by a long shot. This distinction falls to a formation that is actually within the Milky Way itself, a dwarf galaxy that we’ve only known about for a little over a decade.

Closest Galaxy:

At present, the closet known galaxy to the Milky Way is the Canis Major Dwarf Galaxy – aka. the Canis Major Overdensity. This stellar formation is about 42,000 light years from the galactic center, and a mere 25,000 light years from our Solar System. This puts it closer to us than the center of our own galaxy, which is 30,000 light years away from the Solar System.

Illustration of the Canis Dwarf Dwarf Galaxy, Credit: R. Ibata (Strasbourg Observatory, ULP) et al./2MASS/NASA
Illustration of the Canis Dwarf Galaxy and its associated tidal (shown in red) in relation to our Milky Way. Credit: R. Ibata (Strasbourg Observatory, ULP) et al./2MASS/NASA

Characteristics:

The Canis Major Dwarf Galaxy Dwarf Galaxy is believed to contain one billion stars in all, a relatively high-percentage of which are in the Red Giant Branch phase of their lifetimes. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to our location in the Milky Way.

In addition to the dwarf galaxy itself, a long filament of stars is visible trailing behind it. This complex, ringlike structure – which is sometimes referred to as the Monoceros Ring – wraps around the galaxy three times. The stream was first discovered in the early 21st century by astronomers conducting the Sloan Digital Sky Survey (SDSS).

It was in the course of investigating this ring of stars, and a closely spaced group of globular clusters similar to those associated with the Sagittarius Dwarf Elliptical Galaxy, that the Canis Major Dwarf Galaxy was first discovered. The current theory is that this galaxy was accreted (or swallowed up) by the Milky Way Galaxy.

Other globular clusters that orbit the center of our Milky Way as a satellite – i.e. NGC 1851, NGC 1904, NGC 2298 and NGC 2808 – are thought to have been part of the Canis Major Dwarf Galaxy before its accretion. It also has associated open clusters, which are thought to have formed as a result of the dwarf galaxy’s gravity perturbing material in the galactic disk and stimulating star formation.

Images of a few examples of merging galaxies taken by the Hubble Space Telescope. Credit: NASA/ESA/STScI/A. Evans/NRAO/Caltech

Discovery:

Prior to its discovery, astronomers believed that the Sagittarius Dwarf Galaxy was the closest galactic formation to our own. At 70,000 light years from Earth, this galaxy was determined in 1994 to be closer to us than the Large Magellanic Cloud (LMC), the irregular dwarf galaxy that is located 180,000 light years from Earth, and which previously held the title of the closest galaxy to the Milky Way.

All of that changed in 2003 when The Canis Major Dwarf Galaxy was discovered by the Two Micron All-Sky Survey (2MASS). This collaborative astronomical mission, which took place between 1997 and 2001, relied on data obtained by the Mt. Hopkins Observatory in Arizona (for the Northern Hemisphere) and the Cerro Tololo Inter-American Observatory in Chile (for the southern hemisphere).

From this data, astronomers were able to conduct a survey of 70% of the sky, detecting about 5,700 celestial sources of infrared radiation. Infrared astronomy takes advantage of advances in astronomy that see more of the Universe, since infrared light is not blocked by gas and dust to the same extent as visible light.

Because of this technique, the astronomers were able to detect a very significant over-density of class M giant stars in a part of the sky occupied by the Canis Major constellation, along with several other related structures composed of this type of star, two of which form broad, faint arcs (as seen in the image close to the top).

An artist depicts the incredibly powerful flare that erupted from the red dwarf star EV Lacertae. Credit: Casey Reed/NASA
An artist depicts the incredibly powerful flare that erupted from the red dwarf star EV Lacertae. Credit: Casey Reed/NASA

The prevalence of M-class stars is what made the formation easy to detect. These cool, “Red Dwarfs” are not very luminous compared to other classes of stars, and cannot even be seen with the naked eye. However, they shine very brightly in the infrared, and appeared in great numbers.

The discovery of this galaxy, and subsequent analysis of the stars associated with it, has provided some support for the current theory that galaxies may grow in size by swallowing their smaller neighbors. The Milky Way became the size it is now by eating up other galaxies like Canis Major, and it continues to do so today. And since stars from the Canis Major Dwarf Galaxy are technically already part of the Milky Way, it is by definition the nearest galaxy to us.

As already noted, it was the Sagittarius Dwarf Elliptical Galaxy that held the position of closest galaxy to our own prior to 2003. At 75,000 light years away. This dwarf galaxy, which consists of four globular clusters that measure some 10,000 light-years in diameter, was discovered in 1994. Prior to that, the Large Magellanic Cloud was thought to be our closest neighbor.

The Andromeda Galaxy (M31) is the closest spiral galaxy to us, and though it’s gravitationally bound to the Milky Way, it’s not the closest galaxy by far – being 2 million light years away. Andromeda is currently approaching our galaxy at a speed of about 110 kilometers per second. In roughly 4 billion years, the Andromeda Galaxy is expected to merge with out own, forming a single, super-galaxy.

Future of the Canis Major Dwarf Galaxy:

Astronomers also believe that the Canis Major Dwarf Galaxy is in the process of being pulled apart by the gravitational field of the more massive Milky Way Galaxy. The main body of the galaxy is already extremely degraded, a process which will continue as it travels around and through our Galaxy.

In time, the accretion process will likely culminate with the Canis Major Dwarf Galaxy merging entirely with the Milky Way, thus depositing its 1 billion stars to the 200 t0 400 billion that are already part of our galaxy.

We have written many interesting articles on galaxies here at Universe Today. Here’s Closest Galaxy Discovered, How did the Milky Way Form?, How Many Galaxies are there in the Universe?, What is the Milky Way Collision, Spiral Galaxies Could eat Dwarfs all over the Universe and The Canis Major Constellation.

For more information, check out this article from the Spitzer Space Telescope‘s website about the galaxies that are closest to the Milky Way Galaxy. And here is a video by the same author on the subject.

Astronomy Cast has some interesting episodes on the subject. Here’s Episode 97: Galaxies and Episode 99: The Milky Way.

Sources:

Posted on by Matt Williams

What is an Ice Age?

Artist's impression of ice age Earth at glacial maximum. Credit: Wikipedia Commons/Ittiz

Scientists have known for some time that the Earth goes through cycles of climatic change. Owing to changes in Earth’s orbit, geological factors, and/or changes in Solar output, Earth occasionally experiences significant reductions in its surface and atmospheric temperatures. This results in long-term periods of glaciation, or what is more colloquially known as an “ice age”.

These periods are characterized by the growth and expansion of ice sheets across the Earth’s surface, which occurs every few million years. By definition we are still in the last great ice age – which began during the late Pliocene epoch (ca. 2.58 million years ago) – and are currently in an interglacial period, characterized by the retreat of glaciers.

Definition:

While the term “ice age” is sometime used liberally to refer to cold periods in Earth’s history, this tends to belie the complexity of glacial periods. The most accurate definition would be that ice ages are periods when ice sheets and glaciers expand across the planet, which correspond to significant drops in global temperatures and can last for millions of years.

The Antarctic ice sheet, which expanded during the last ice age. Credit: Wikipedia Commons/Stephen Hudson

During an ice age, there are significant temperature differences between the equator and the poles, and temperatures at deep-sea levels have also been shown to drop. This allows for large glaciers (comparable to continents) to expand, covering much of the surface area of the planet. Since the Pre-Cambrian Era (ca. 600 million years ago), ice ages have occurred at widely space intervals about about 200 million years.

History of Study:

The first scientist to theorize about past glacial periods was the 18th century Swiss engineer and geographer Pierre Martel. In 1742, while visiting an Alpine valley, he wrote about the dispersal of large rocks in erratic formations, which the locals attributed to the glaciers having once extended much further. Similar explanations began to emerge in the ensuing decades for similar patterns of boulder distribution in other parts of he world.

From the middle of the 18th century onward, European scholars increasingly began to contemplate ice as a means of transporting rocky material. This included the presence of boulders in coastal areas in the Baltic states and the Scandinavian peninsula. However, it was Danish-Norwegian geologist Jens Esmark (1762–1839) who first argued the existence of a sequence of world wide ice ages.

This theory was detailed in a paper he published in 1824, in which he proposed that changes in Earth’s climate (which were due to changes in its orbit) were responsible. This was followed in 1832 by German geologist and forestry professor Albrecht Reinhard Bernhardi speculating about how the polar ice caps may have once reached as far as the temperate zones of the world.

Overlook of the Grinnell Glacier in Glacier National Park, Montana. Credit: USGS

At this same time, German botanist Karl Friedrich Schimper and Swiss-American biologist Louis Agassiz began independently developing their own theory about global glaciation, which led toSchimper coining the term “ice age” in 1837. By the late 19th century, ice age theory gradually began to gain widespread acceptance over the notion that the Earth cooled gradually from its original, molten state.

By the 20th century, Serbian polymath Milutin Milankovic developed his concept of Milankovic cycles, which linked long-term climate changes to periodic changes in the Earth’s orbit around the Sun. This offered a demonstrable explanation for ice ages, and allowed scientists to make predictions about when significant changes in Earth’s climate might occur again.

Evidence for Ice Ages:

There are three forms of evidence for ice age theory, which range from the geological and the chemical to the paleontological (i.e. the fossil record). Each has its particular benefits and drawbacks, and has helped scientists to develop a general understanding of the effect ice ages have had on geological record for the past few billion years.

Geological: Geological evidence includes rock scouring and scratching, carved valleys, the formation of peculiar types of ridges, and the deposition of unconsolidated material (moraines) and large rocks in erratic formations.  While this sort of evidence is what led to ice age theory in the first place, it remains temperamental.

For one, successive glaciation periods have different effects on a region, which tends to distort or erase geological evidence over time. In addition, geological evidence is difficult to date exactly, causing problems when it comes to getting an accurate assessment of how long glacial and interglacial periods have lasted.

Horseshoe-shaped lateral moraines at the margin of the Penny Ice Cap on Baffin Island, Nunavut, Canada. Lateral moraines are accumulations of debris along the sides of a glacier formed by material falling from the valley wall. Credit: NASA/Michael Studinger

Chemical: This consists largely of variations in the ratios of isotopes in fossils discovered in sediment and rock samples. For more recent glacial periods, ice cores are used to construct a global temperature record, largely from the presence of heavier isotopes (which lead to higher evaporation temperatures). They often contain bubbles of air as well, which are examined to assess the composition of the atmosphere at the time.

Limitations arise from various factors, however. Foremost among these are isotope ratios, which can have a confounding effect on accurate dating. But as far as the most recent glacial and interglacial periods are concerned (i.e. during the past few million years), ice core and ocean sediment core samples remain the most trusted form of evidence.

Paleontological: This evidence consists of changes in the geographical distribution of fossils. Basically, organisms that thrive in warmer conditions become extinct during glacial periods (or become highly restricted in lower latitudes), while cold-adapted organisms thrive in these same latitudes. Ergo, reduced amounts of fossils in higher latitudes is an indication of the spread of glacial ice sheets.

This evidence can also be difficult to interpret because it requires that the fossils be relevant to the geological period under study. It also requires that sediments over wide ranges of latitudes and long periods of time show a distinct correlation (due to changes in the Earth’s crust over time). In addition, there are many ancient organisms that have shown the ability to survive changes in conditions for millions of years.

As a result, scientists rely on a combined approach and multiple lines of evidence wherever possible.

Ice ages are characterized by a drop in average global temperatures, resulting in the expansion of ice sheets globally. Credit: NASA

Causes of Ice Ages:

The scientific consensus is that several factors contribute to the onset of ice ages. These include changes in Earth’s orbit around the Sun, the motion of tectonic plates, variations in Solar output, changes in atmospheric composition, volcanic activity, and even the impact of large meteorites. Many of these are interrelated, and the exact role that each play is subject to debate.

Earth’s Orbit: Essentially, Earth’s orbit around the Sun is subject to cyclic variations over time, a phenomenon also known as Milankovic (or Milankovitch) cycles. These are characterized by changing distances from the Sun, the precession of the Earth’s axis, and the changing tilt of the Earth’s axis – all of which result in a redistribution of the sunlight received by the Earth.

The most compelling evidence for Milankovic orbital forcing corresponds closely to the most recent (and studied) period in Earth’s history (circa. during the last 400,000 years). During this period, the timing of glacial and interglacial periods are so close to changes in Milankovic orbital forcing periods that it is the most widely accepted explanation for the last ice age.

Tectonic Plates: The geological record shows an apparent correlation between the onset of ice ages and the positions of the Earth’s continents. During these periods, they were in positions which disrupted or blocked the flow of warm water to the poles, thus allowing ice sheets to form.

The Earth’s Tectonic Plates. Credit: msnucleus.org

This in turn increased the Earth’s albedo, which reduces the amount of solar energy absorbed by the Earth’s atmosphere and crust. This resulted in a positive feedback loop, where the advance of ice sheets further increased the Earth’s albedo and allowed for more cooling and more glaciation. This would continue until the onset of a greenhouse effect ended the period of glaciation.

Based on past ice-ages, three configurations have been identified that could lead to an ice age – a continent sitting atop the Earth’s pole (as Antarctica does today); a polar sea being land-locked (as the Arctic Ocean is today); and a super continent covering most of the equator (as Rodinia did during the Cryogenian period).

In addition, some scientists believe that the Himalayan mountain chain – which formed 70 million years ago – has played a major role in the most recent ice age. By increasing the Earth’s total rainfall, it has also increased the rate at which CO² has been removed from the atmosphere (thereby decreasing the greenhouse effect). Its existence has also paralleled the long-term decrease in Earth’s average temperature over the past 40 million years.

Atmospheric Composition: There is evidence that levels of greenhouse gases fall with the advance of ice sheets and rise with their retreat. According to the “Snowball Earth” hypothesis – in which ice completely or very nearly covered the planet at least once in the past – the ice age of the late Proterozoic was ended by an increase in CO² levels in the atmosphere, which was attributed to volcanic eruptions.

Image of the Harding Ice Field on Alaska’s Kenai Peninsula. Credit: US Fish and Wildlife Service

However, there are those who suggest that increased levels of carbon dioxide may have served as a feedback mechanism, rather than the cause. For example, in 2009, an international team of scientists produced a study – titled “The Last Glacial Maximum” – that indicated that an increase in solar irradiance (i.e. energy absorbed from the Sun) provided the initial change, whereas greenhouse gases accounted for the magnitude of change.

Major Ice Ages:

Scientists have determined that at least five major ice ages took place in Earth’s history. These include the Huronian, Cryogenian, Andean-Saharan, Karoo, and the Qauternary ice ages. The Huronian Ice Age is dated to the early Protzerozoic Eon, roughly 2.4 to 2.1 billion years ago, based on geological evidence observed to the north and north-east of Lake Huron (and correlated to deposits found in Michigan and Western Australia).

The Cryogenian Ice Age lasted from roughly 850 to 630 million years ago, and was perhaps the most severe in Earth’s history. It is believed that during this period, the glacial ice sheets reached the equator, thus leading to a “Snowball Earth” scenario. It is also believed that ended due to a sudden increase in volcanic activity that triggered a greenhouse effect, though (as noted) this is subject to debate.

The Andean-Saharan Ice Age occurred during the Late Ordovician and the Silurian period (roughly 460 to 420 million years ago). As the name suggests, the evidence here is based on geological samples take from the Tassili n’Ajjer mountain range in the western Sahara, and correlated by evidence obtained from the Andean mountain chain in South America (as well as the Arabian peninsula and the south Amazon basin).

Floating ice at the calving front of Greenland’s Kangerdlugssuaq glacier, photographed in 2011 during Operation IceBridge. Credit: NASA/Michael Studinger

The Karoo Ice Age is attributed to the evolution of land plants during the onset of the Devonian period (ca. 360 to 260 million years ago) which caused a long-term increase in planetary oxygen levels and a reduction in CO² levels – leading to global cooling. It is named after sedimentary deposits that were discovered in the Karoo region of South Africa, with correlating evidence found in Argentina.

The current ice age, known as the Pliocene-Quaternary glaciation, started about 2.58 million years ago during the late Pliocene, when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has experienced several glacial and interglacial periods, where ice sheets advance and retreat on time scales of 40,000 to 100,000 years.

The Earth is currently in an interglacial period, and the last glacial period ended about 10,000 years ago. What remains of the continental ice sheets that once stretched across the globe are now restricted to Greenland and Antarctic, as well as smaller glaciers – like the one that covers Baffin Island.

Anthropogenic Climate Change:

The exact role played by all the mechanisms that ice ages are attributed to – i.e. orbital forcing, solar forcing, geological and volcanic activity – are not yet entirely understood. However, given the role of carbon dioxide and other greenhouse gas emissions, there has been a great deal of concern in recent decades what long-term effects human activity will have on the planet.

For instance, in at least two major ice ages, the Cryogenian and Karoo Ice Ages, increases and decreases in atmospheric greenhouse gases are believed to have played a major role. In all other cases, where orbital forcing is believed to be the primary cause of an ice age ending, increased greenhouse gas emissions were still responsible for the negative feedback that led to even greater increases in temperature.

The addition of CO2 by human activity has also played a direct role in climatic changes taking place around the world. Currently, the burning of fossil fuels by humans constitutes the largest source of emissions of carbon dioxide (about 90%) worldwide, which is one of the main greenhouse gases that allows radiative forcing (aka. the Greenhouse Effect) to take place.

In 2013, the National Oceanic and Atmospheric Administration announced that CO² levels in the upper atmosphere reached 400 parts per million (ppm) for the first time since measurements began in the 19th century. Based on the current rate at which emissions are growing, NASA estimates that carbon levels could reach between 550 to 800 ppm in the coming century.

If the former scenario is the case, NASA anticipates a rise of 2.5 °C (4.5 °F) in average global temperatures, which would be sustainable. However, should the latter scenario prove to be the case, global temperatures will rise by an average of 4.5 °C (8 °F), which would make life untenable for many parts of the planet. For this reason, alternatives are being sought out for development and widespread commercial adoption.

What’s more, according to a 2012 research study published in Nature Geoscience – titled “Determining the natural length of the current interglacial” – human emissions of CO² are also expected to defer the next ice age. Using data on Earth’s orbit to calculate the length of interglacial periods, the research team concluded that the next ice (expected in 1500 years) would require atmospheric CO² levels to remain beneath around 240?ppm.

Learning more about the longer ice ages as well the shorter glacial periods that have taken place in Earth’s past is important step towards understanding how Earth’s climate changes over time. This is especially important as scientists seek to determine how much of modern climate change is man-made, and what possible counter-measures can be developed.

We have written many articles about the Ice Age for Universe Today. Here’s New Study Reveals Little Ice Age Driven by Volcanism, Did a Killer Asteroid Drive the Planet into an Ice Age?, Was There a Slushball Earth?, and Is Mars Coming out of an Ice Age?

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth and Episode 308: Climate Change.

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Posted on by Matt Williams

How Do Wind Turbines Work?

In Denmark, wind power accounts for 28% of electrical production and is cheaper than coal power. Credit: denmark.dk

Perhaps you’ve seen them while driving through the countryside. Or maybe you saw them just off the coast, looming large on the horizon with their spinning blades. Then again, you may have seen them on someone’s roof, or as part of a small-scale urban operation. Regardless of the location, wind turbines and wind power are becoming an increasingly common feature in the modern world.

Much of this has to do with the threat of Climate Change, air pollution, and the desire to wean humanity off its dependence on fossil fuels. And when it comes to alternative and renewable energy, wind power is expected to occupy the second-largest share of the market in the future (after solar). But just how exactly do wind turbines work?

Description:

Air turbines are devices that turn the kinetic energy of wind and changes in air flow into electrical energy. In general, they consist of the following components: a rotor, a generator, and a structural support component (which can take the form of either a tower, a rotor yaw mechanism, or both).

NASA’s Ames Research Center and the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) testing a research wind turbine in the world’s largest wind tunnel in April of 2000. Credit: NASA

A rotor consists of the blades that capture the wind’s energy and a shaft, which converts the wind energy to low-speed rotational energy. The generator – which is connected to the shaft – converts the slow rotation to high into electrical energy using a series of magnets and a conductor (which usually consists of coiled copper wire).

When the magnets rotate around with the copper wire, its produces a difference in electrical potential, creating voltage and an electric current. Lastly, there is the structural support component, which ensures that the turbine either stands at a high enough altitudes to optimally capture changes in wind pressure, and/or face in the direction of wind flow.

Types of Wind Turbines:

At present, there are two main types of wind turbines – Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). As the name would imply, horizontal wind turbines have a main rotor shaft and electrical generator at the top of a tower, with the blades pointed into the wind. The turbine is usually positioned upwind of its supporting tower, since the tower is likely to produce turbulence behind it.

Vertical axis turbines (once again, as the name implies) have the main rotor shaft arranged vertically. Typically, these are smaller in nature, and do not need to be pointed in the direction of the wind in order to rotate. They are thereby being able to take advantage of wind that is variable in terms of direction.

A Darrieus wind turbine, located in Martigny, Switzerland. Credit: Wikipedia Commons/Lysippos

In general, horizontal axis wind turbines are considered more efficient and can produce more power. While the vertical model generates less electricity it can be placed at lower elevations and needs less in the way of components (particularly a yaw mechanism). Wind turbines can also be divided into three general groups based on their design, which includes the Towered, Savonius, and Darrieus models.

The towered model is the most conventional form of HAWT, consisting of a tower (as the name would suggest) and a series of long blades that sit ahead of (and parallel to) the tower. The Savonis is a VAWT model that relies on contoured blades (scoops) to capture wind and spin. They are generally low-efficiency, but have the benefit of being self-starting. These sorts of turbines are often part of rooftop wind operations or mounted on sea vessels.

The Darrieus model, also known as an “Eggbeater” turbine, is named after the French inventor who pioneered the design – Georges Darrieus. This VAWT model employs a series of vertical blades that sit parallel to the vertical support. They are generally low efficiency, require an additional rotor to start turning, produce high-torque, and place high stress on the tower. Hence, they are considered unreliable as designs go.

History of Development:

Wind power has been used for thousands of years to push sails, power windmills, or to generate pressure for water pumps. The earliest known examples come from Central Asia, where windmills used in ancient Persia (Iran) have been dated to between 500 – 900 CE. The technology began to appear in Europe during the Middle Ages, and became a common feature by the 16th century.

The first automatically operated wind turbine, built in Cleveland in 1887 by Charles F. Brush. Credit: Wikipedia Commons

By the 19th century, with the development of electrical power, the first wind turbines capable of generating electricity were built. The first was installed in 1887 by Scottish academic James Blyth to light his holiday home in Marykirk, Scotland. In 1888, American inventor Charles F. Brush built the first automated wind turbine to power his home in Cleveland, Ohio.

By the early 20th century, wind turbines began to become a common means of powering homes in remote areas (such as farmsteads). In 1941, the first megawatt-class wind turbine was installed in Vermont and attached to the local utility grid. In 1951, the UK installed its first utility-grid connected wind turbine in the Orkney Islands.

By the 1970s, research and development into wind turbine technology advanced considerably thanks to the OPEC crisis and protests against nuclear power. In the ensuing decades, associations and lobbyists dedicated to alternative energy began to emerge in western European nations and the United States. By the final decade of the 20th century, similar efforts emerged in India and China due to growing air pollution and rising demand for clean energy.

Wind Power:

Compared to other forms of renewable energy, wind power is considered very reliable and steady, as wind is consistent from year to year and does not diminish during peak hours of demand. Initially, the construction of wind farms was a costly venture. But thanks to recent improvements, wind power has begun to set peak prices in wholesale energy markets worldwide and cut into the revenues and profits of the fossil fuel industry.

Cross-section of a vertical wind turbine. Credit: energy.gov

According to a report issued by the Department of Energy in March of 2015, the growth of wind power in the United States could lead to even more highly skilled jobs in many categories. Titled “Wind Vision: A New Era for Wind Power in the United States”, the document indicates that by 2050, the industry could account for as much as 35% of the US’ electrical production.

In addition, in 2014, the Global Wind Energy Council and Greenpeace International came together to publish a report titled “Global Wind Energy Outlook 2014”. This report stated that worldwide, wind power could provide as much as 25 to 30% of global electricity by 2050. At the time of the report’s writing, commercial installations in more than 90 countries had a total capacity of 318 gigawatts (GW), providing about 3.1% of global supply.

This represents a nearly sixteen-fold increase in the rate of adoption since the year 2000, when wind power accounted for less than 0.2%. Another way to look at it would be to say that the market share of wind power has doubled four times in less than 15 years. This places it second only to solar power, which doubled seven times over in the same period, but still trails wind in terms of its overall market share (at about 1% by 2014).

An offshore wind farm located off the coast of Belgium. Credit: Wikipedia Commons/Hans Hillewaert

In terms of its disadvantages, one consistently raised issue is the effect wind turbines have on local wildlife, and the disturbance their presence has on the local landscape. However, these concerns have often been shown to be inflated by special interest groups and lobbyists seeking to discredit wind power and other renewable energy sources.

For instance, a 2009 study released by the National Renewable Energy Laboratory determined that less than 1 acre per megawatt is disturbed permanently by the construction of large-scale wind farms, and less than 3.5 acres per megawatt are disturbed temporarily. The same study concluded that the impacts are relatively low on bird and bat wildlife, and that the same conclusions hold true for offshore platforms.

All over the world, governments and local communities are looking to wind power in order to meet their energy needs. In an age of rising fuel prices, growing concerns over Climate Change, and improving technology, this is hardly surprising. At its current rate of adoption, it is likely to be one of the largest sources of energy by mid-century.

And be sure to enjoy this video about wind turbines, courtesy of NASA’s Lewis Research Center:

We have written many interesting articles on wind turbines and wind power here at Universe Today. Here’s What is Alternative Energy?, What are Fossil Fuels?, What are the Different Types of Renewable Energy?, Wind Power on the Ocean (with Help from Space), and Could the World Run on Solar and Wind Power?

For more information, check out How Stuff Works’s article about the history and mechanics of wind power and NASA’s Greenspace page.

Astronomy Cast also has some episodes that are relevant to the subject. Here’s Episode 51: Earth and Episode 308: Climate Change.

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