Posted on by Matt Williams

Stars Are The Universe’s Neat Freaks

The Andromeda Galaxy, viewed using conventional optics and IR. Credit: Kitt Peak National Observatory

Imagine, if you will, that the Universe was once a much dirtier place than it is today. Imagine also that what we see around us, a relatively clean and unobscured Universe, is the result of billions of years of stars behaving like giant celestial Roombas, cleaning up the space around them in preparation for our arrival. According to a set of recently published catalogues, which detail the latest findings from the ESA’s Herschel Space Observatory, this description is actually quite fitting.

These catalogues represents the work of an international team of over 100 astronomers who have spent the past seven years analyzing the infrared images taken by the Herschel Astrophysical Terahertz Large Area Survey (Herschel-ATLAS). Presented earlier this week at the National Astronomy Meeting in Nottingham, this catalogue revealed that 1 billion years after the Big Bang, the Universe looked much different than it does today.

In order to put this research into context, it is important to understand the important of infrared astronomy. Prior to the deployment of missions like Herschel (which was launched in 2009), astronomers were unable to see a good portion of the light emitted by stars and galaxies. With roughly half of this light being absorbed by interstellar dust grains, research into the birth and lives of galaxies was difficult.

But thanks to surveys like Herschel ATLAS – as well NASA’s Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE) – astronomers have been able to account for this missing energy. And what they have seen (especially from this latest survey) has been quite remarkable, presenting a Universe that is far denser than previously expected.

Artist's impression of the Herschel Space Telescope. Credit: ESA/AOES Medialab/NASA/ESA/STScI
Artist’s impression of the Herschel Space Telescope. Credit: ESA/AOES Medialab/NASA/ESA/STScI

Professor Haley Gomez of Cardiff University presented this catalogue during the third day of the National Astronomy Meeting (which ran from June 27th to July 1st). As she told Universe Today via email:

“The Herschel survey is the largest one of the sky in these special infrared light. Because of this we see rare objects that we might not see in a smaller patch of sky, but also we now see hundreds of thousands of dusty galaxies, compared to the few hundred we saw in previous telescopes. So this is a massive improvement in terms of knowing what kinds of galaxies there are. Some of these are so covered in dust we might never had seen them using visible light telescopes. Because of the unprecedented large area we have with this Herschel survey, we see a huge variety in the type of objects too, from nearby dusty star forming clouds, to nearby dusty galaxies like Andromeda, to galaxies that shone their infrared light more than 12 billion years ago.  We can also use this survey to understand the structure of galaxies in the universe – the so-called cosmic web in a way we’ve never been able to do in the far infrared.”

The images they showed gave all those present a glimpse of the unseen stars and galaxies that have existed over the last 12 billion years of cosmic history. In sum,  over half-a-million far-infrared sources have been spotted by the Herschel-ATLAS survey. Many of these sources were galaxies that are nearby and similar to our own, and which are detectable using using conventional telescopes.

The others were much more distant, their light taking billions of years to reach us, and were obscured by concentrations of cosmic dust. The most distant of these galaxies were roughly 12 billion light-years away, which means that they appeared as they would have 12 billion years ago.

Herschel fig2smallAn illustration of the time reach of the Herschel ATLAS and the kinds of objects it has discovered. Credit: Herschel-ATLAS/ESA/ALMA/ NRAO
Herschel fig2smallAn illustration of the time reach of the Herschel ATLAS and the kinds of objects it has discovered. Credit: Herschel-ATLAS/ESA/ALMA/ NRAO

Ergo, astronomers now know that 12 billion years ago (i.e. shortly after the Big Bang)., stars and galaxies were much dustier than they are now. They further concluded that the evolution of our galaxies since shortly after the Big Bang has essentially been a major clean-up effort, as stars gradually absorbed the dust that obscured their light, thus making it the more “visible” place it is today.

The data released by the survey includes several maps and additional files which were described in an article produced by Dr. Elisabetta Valiante and a research team from Cardiff University – titled “The Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts“. As Dr. Valiante told Universe Today via email:

“Gas and dust are the main components of stars: they collapse to form stars and they are ejected at the end of stars’ life. The interesting thing that has been discovered thanks to the Herschel data is that the two phenomena are not in equilibrium. We knew this was true 10 billion years ago, but we expected, according to the current models, that some equilibrium was reached at more recent times. Instead, the amount of dust in galaxies 5 billion years ago was much larger than the amount we see in galaxies today: this was unexpected.”

Until recently, such a survey would have been impossible due to the fact that many of these infrared sources would have  been invisible to astronomers. The reason for this, which was revealed by the survey, was that these galaxies were so dusty that they would have been virtually impossible to detect with conventional optics. What’s more, their light would have been gravitationally magnified by intervening galaxies.

"This dazzling infrared image from NASA's Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. In visible-light pictures, this region cannot be seen at all because dust lying between Earth and the galactic center blocks our view. Credit: NASA/JPL-Caltech
Infrared images (like the one captured by NASA’s Spitzer Space Telescope here) show countless stars and galaxies that are obscured in visible-light by cosmic dust. Credit: NASA/JPL-Caltech

The huge size of the survey has also meant that changes that have occurred in galaxies – relatively recent in cosmic history – can be studied for the first time. For instance, the survey showed that even only one billion years in the past, a small fraction of the age of the universe, galaxies were forming stars at a faster rate and contained more dust than they do today.

Dr. Nathan Bourne – from the University of Edinburgh – is the lead author of another other paper describing the catalogues. As he told Universe Today via email:

“We can think of galaxies as big recycling machines. When they form, they accrete gas (mostly hydrogen and helium, with traces of lithium and a couple of other elements) from the universe around them, and they turn it into stars. As time goes on, the stars pump this gas back out into the galaxy, into the interstellar medium. Due to the nuclear processes within the stars, the gas is now enriched by heavy elements (what we call metals, though they include both metals and non-metals), and some of these form microscopic solid particles of dust, as a sort of by-product.

“But there are still stars forming, and the next generations of stars recycle this interstellar material, and now that it contains heavy elements and dust, things are a bit different, and planets can also form around the new stars, from accumulations of this heavy material. So, if you look at the big picture, when the first galaxies started forming within the first billion years after the Big Bang, they began using up the gas around them, and then while they are active they fill their interstellar medium up with gas and dust, but by the end of a galaxy’s lifecycle, it has used up all this gas and dust, and you could say that it has cleaned itself.”

The catalogues and maps of the hidden universe are a triumph for the Herschel team. Despite the fact that the last information obtained by the Herschel observatory was back in 2013, the maps and catalogues produced from its years of service have become vital to astronomers. In addition to showing the Universe’s hidden energy, they are also laying the groundwork for future research.

. Credit: NASA/JPL-Caltech/UCLA (top), NASA/DIRBE Team/COBE/ (bottom)
IR images of the entire sky take by the WISE All-Sky Data Release (top), and a projection of the IR sky created by images taken by the COBE spacecraft (bottom). Credit: NASA/JPL-Caltech/UCLA (top), NASA/DIRBE Team/COBE/ (bottom)

“Now we need to explain why there is dust where we did not expect to find it.” said Valiante. “And to explain this, we need to change our theories about how the Universe evolves. Our data poses a challenge we have accepted, but we haven’t overcome it yet!”

“[W]e understand a lot more about how galaxies evolve,” added Bourne, “about when most of the stars formed, what happens to the gas and dust as galaxies evolve, and how rapidly the star-forming activity in the Universe as a whole has faded in the latter half of the Universe’s history. It’s fair to say that this understanding comes from having a whole suite of different types of instruments studying different aspects of galaxies in complementary ways, but Herschel has certainly contributed a major part of that effort and will have a lasting legacy.”

Ensuring Herschel’s lasting legacy is one of the main aims of the Herschel Extragalactic Project (HELP) program, which is overseen by the EU Research Executive Agency. Other projects they oversee include the Herschel Multi-tiered Extragalactic Survey (HerMES), which also released survey data late last month. All of this has left a lasting mark on the field of astronomy, despite the fact that Herschel is no longer in operation. As Professor Gomez said of the Herschel Observatory’s enduring contributions:

“The Herschel Space Observatory stopped taking data in 2013, yet our understanding of the dusty universe is really only just starting with the release of large surveys and galaxy catalogues in recent months. Ultimately, once astronomers have gone through all the valuable data, Herschel will have provided a view of the infrared universe covering 1000 square degrees of the sky.”

The implications of these findings are also likely to have a far-reaching effect, ranging from cosmology and astronomy, to perhaps shedding some light on that tricky Fermi paradox. Could it be intelligent life that emerged billions of years ago didn’t venture to other star systems because they couldn’t see them? Just a thought…

Further Reading: Royal Astronomical Society, ESA

Posted on by Matt Williams

The Juno Mission

NASA's Juno spacecraft launched on August 6, 2011 and should arrive at Jupiter on July 4, 2016. Credit: NASA / JPL

Ever since Galileo first observed it through a telescope in 1610, Jupiter and its system of moons have fascinated humanity. And while many spacecraft have visited the system in the past forty years, the majority of these missions were flybys. With the exception of the Galileo space probe, the visits of these spacecraft to the Jupiter system were one of several intended objectives, taking place before they made their way deeper into the Solar System.

Having launched on August 5th, 2011, NASA’s Juno spacecraft has a different purpose in mind. Using a suite of scientific instruments, Juno will study Jupiter’s atmosphere, magnetic environment, weather patterns, and shed light on the history of its formation. In essence, it will be the first probe since the Galileo mission to orbit Jupiter, where it will spend the next two years sending information about the gas giant back to Earth.

If successful, Juno will prove to be the only other long-term mission to Jupiter. However, compared to Galileo – which spent seven years in orbit around the gas giant – Juno’s mission is planned to last for just two years. However, its improved suite of instruments are expected to provide a wealth of information in that time. And barring any mission extensions, its targeted impact on the surface of Jupiter will take place in February of 2018.

Juno will repeatedly dive between the planet and its intense belts of charged particle radiation, coming only 5,000 kilometers (about 3,000 miles) from the cloud tops at closest approach. (NASA/JPL-Caltech)
Juno will dive between the planet and its intense belts of charged particle radiation, coming  within 5,000 kilometers (about 3,000 miles) from the cloud tops. Credit: NASA/JPL-Caltech

Background:

As part of the NASA’s New Frontiers program, the Juno mission is one of several medium-sized missions intended to explore the various bodies of the Solar System. It is currently one of three probes that NASA is operating, or in the process of building. The other two are the New Horizons probe (which flew by Pluto in 2015) and OSIRIS-REx, which is expected to fly to asteroid 101955 Bennu in 2020 and bring samples back to Earth.

During a 2003 decadal survey – titled “New Frontiers in the Solar System: An Integrated Exploration Strategy” – The National Research Council discussed destinations that would serve as the source for the first competition for the New Frontiers program. A Jupiter orbiter was identified as a scientific priority, which it was hoped would address several unanswered questions pertaining to the gas giant.

These included whether or not Jupiter had a central core (the research of which would help establish how the planet was formed), the water content of Jupiter’s atmosphere, how its weather systems can remain stable, and what the nature of the magnetic field and plasma surrounding Jupiter are. In 2005, Juno was selected for the New Frontiers program alongside New Horizons and OSIRIS-REx.

Though it was originally intended to launch in 2009, NASA budget restrictions forced a delay until August of 2011. The probe was named in honor of the Roman goddess Juno, the wife of Jupiter (the Roman equivalent of Zeus) who was able to peer through a veil of clouds that Jupiter drew around himself. The name was previously a backronym which stood for JUpiter Near-polar Orbiter as well.

Mission Profile:

The Juno mission was created for the specific purpose of studying Jupiter for the sake of learning more about the formation of the Solar System. For some time, astronomers have understood that Jupiter played an important role in the development Solar System. Like the other gas giants, it was assembled during the early stages, before our Sun had the chance to absorb or blow away the light gases in the huge cloud from which they were born.

As such, Jupiter’s composition could tell us much about the early Solar System. Similarly, the gas giants are believed to have played a major role in the process of planet formation because their huge masses allowed them to shape the orbits of other objects – planets, asteroids and comets – in their planetary systems.

However, for astronomers and planetary scientists, much still remains unknown about this massive gas giant. For instance, Jupiter’s interior structure and composition, as well as what drives its magnetic field, are still the subject of theory. Because Jupiter formed at the same time as the Sun, their chemical compositions should be similar, but research has shown that Jupiter has more heavy elements than our Sun (such as carbon and nitrogen).

In addition, there are some unanswered questions about when and where the planet formed. While it may have formed in its current orbit, some evidence suggests that it could have formed farther from the sun before migrating inward. All of these questions, it is hoped, are things the Juno mission will answer.

Technician's install Juno's titanium vault. (Image Credit: NASA/JPL-Caltech/LMSS)
Technician’s install Juno’s titanium vault. (Image Credit: NASA/JPL-Caltech/LMSS)

Having launched on August 5th, 2011, the Juno spacecraft spent the next five years in space, and will reach Jupiter on July 4th, 2018. Once in orbit, it will spend the next two years orbiting the planet a total of 37 times from pole to pole, using its scientific instruments to probe beneath the gas giant’s obscuring cloud cover.

Instrumentation:

The Juno spacecraft comes equipped with a scientific suite of 8 instruments that will allow it to study Jupiter’s atmosphere, magnetic and gravitational field, weather patterns, its internal structure, and its formational history. They include:

  • Gravity Science: Using radio waves and measuring them for Doppler effect, this instrument will measure the distribution of mass inside Jupiter to create a gravity map. Small variations in gravity along the orbital path of the probe will induce small changes in velocity. The principle investigators of this instrument are John Anderson of NASA’s Jet Propulsion Laboratory and Luciano Iess of the Sapienza University of Rome.
  • JunoCam: This visible light/telescope is the spacecraft’s only imaging device. Intended for public outreach and education, it will provide breathtaking pictures of Jupiter and the Solar System, but will operate for only seven orbits around Jupiter (due to the effect Jupiter’s radiation and magnetic field have on instruments). The PI for this instrument is Michael C. Malin, of Malin Space Science Systems
  • Jovian Auroral Distribution Experiment (JADE): Using three energetic particle detectors, the JADE instrument will measure the angular distribution, energy, and velocity vector of low energy ions and electrons in the auroras of Jupiter. The PI is David McComas of the Southwest Research Institute (SwRI).
  • Jovian Energetic Particle Detector Instrument (JEDI): Like JADE, JEDI will measure the angular distribution and the velocity vector of ions and electrons, but at high-energy and in the magnetosphere of Jupiter. The PI is Barry Mauk of NASA’s Applied Physics Laboratory.
Juno spacecraft and its science instruments. Image credit: NASA/JPL
Juno spacecraft and its science instruments. Credit: NASA/JPL
  • Jovian Infrared Aural Mapper (JIRAM): Operating in the near-infrared, this spectrometer will be responsible for mapping the upper layers of Jupiter’s atmosphere. By measuring the heat that is radiated outward, it will determine how water-rich clouds can float beneath the surface. It will also be able to assess the distribution of methane, water vapor, ammonia and phosphine in Jupiter’s atmosphere. Angioletta Coradini of the Italian National Institute for Astrophysics is the PI on this instrument.
  • Magnetometer: This instrument will be used to map Jupiter’s magnetic field, determine the dynamics of the planet’s interior and determine the three-dimensional structure of the polar magnetosphere. Jack Connemey of NASA’s Goddard Space Flight Center is the instrument’s PI.
  • Microwave Radiometer: The MR instrument will perform measurements of the electromagnetic waves that pass through the Jovian atmosphere, measuring the abundance of water and ammonia in its deep layers. In so doing, it will obtain a temperature profile at various levels and determine how deep the atmospheric circulation of Jupiter is. The PI for this instrument is Mike Janssen of the JPL.
  • Radio and Plasma Wave Sensor (RPWS): This RPWS will measure the radio and plasma spectra in Jupiter’s auroral region. In the process, it will identify the regions of auroral currents that define the planet’s radio emissions and accelerate its auroral particles. William Kurth of the University of Iowa is the PI.
  • Ultraviolet Imaging Spectrograph (UVS): The UVS will record the wavelength, position and arrival time of detected ultraviolet photons, providing spectral images of the UV auroral emissions in the polar magnetosphere. G. Randall Gladstone of the SwRI is the PI.

In addition to its scientific suite, the Juno spacecraft also carries a commemorative plaque dedicated to Galileo Galilei. The plaque was provided by the Italian Space Agency and depicts a portrait of Galileo, as well as script that had been composed by Galileo himself on the occasion that he observed Jupiter’s four largest moons (known today as the Galilean Moons).

The Galileo plague aboard the Juno spacecraft. Credit: NASA/JPL-Caltech/KSC
The Galileo plague aboard the Juno spacecraft. Credit: NASA/JPL-Caltech/KSC

The text, written in Italian and transcribed from Galileo’s own handwriting, translates as:

“On the 11th it was in this formation, and the star closest to Jupiter was half the size than the other and very close to the other so that during the previous nights all of the three observed stars looked of the same dimension and among them equally afar; so that it is evident that around Jupiter there are three moving stars invisible till this time to everyone.”

The spacecraft also carries three Lego figurines representing Galileo, the Roman god Jupiter and his wife Juno. The figure of Juno holds a magnifying glass as a sign of her searching for the truth, Jupiter holds a lightning bolt, and the figure of Galileo Galilei holds his famous telescope. Lego made these figurines out of aluminum (instead of the usual plastic) to ensure they would survive the extreme conditions of space flight.

Launch:

The Juno mission launched from Cape Canaveral Air Force Station on August 5th, 2011, atop an Atlas V rocket. After approximately 1 minute and 33 seconds, the five Solid Rocket Boosters (SRBs) reached burnout and then fell away. After 4 minutes and 26 seconds after liftoff, the Atlas V main engine cut off, followed 16 seconds later by the separation of the Centaur upper stage rocket.

After a burn that lasted for 6 minutes, the Centaur was put into its initial parking orbit. It coasted for approximately 30 minutes before its engine conducted a second firing which lasted for 9 minutes, putting the spacecraft on an Earth escape trajectory. About 54 minutes after launch, the spacecraft separated from the Centaur and began to extend its solar panels.

A year after launch, between August and September 2012, the Juno spacecraft successfully conducted two Deep Space Maneuvers designed to correct its trajectory. The first maneuver (DSM-1) occurred on August 30th, 2012, with the main engine firing for approximately 30 minutes and altering its velocity by about 388 m/s (1396.8 km/h; 867 mph).

The second maneuver (DSM-2), which had a similar duration and resulted in a similar velocity change, took place on September 14th. The two firings occurred when the probe was about 480 million km (298 million miles) from Earth, and altered the spacecraft’s speed and its Jupiter-bound trajectory, setting the stage for a gravity assist from its flyby of Earth.

Earth Flyby:

Juno’s Earth flyby took place on October 9th, 2013, after the spacecraft completed one elliptical orbit around the Sun. During its closest approach, the probe was at an altitude of about 560 kilometers (348 miles). The Earth flyby boosted Juno’s velocity by 3,900 m/s (14162 km/h; 8,800 mph) and placed the spacecraft on its final flight path for Jupiter.

During the flyby, Juno’s Magnetic Field Investigation (MAG) instrument managed to capture some low-resolution images of the Earth and Moon. These images were taken while the Juno probe was about 966,000 km (600,000 mi) away from Earth – about three times the Earth-moon separation. They were later combined by technicians at NASA’s JPL to create the video shown above.

The Earth flyby was also used as a rehearsal by the Juno science team to test some of the spacecraft’s instruments and to practice certain procedures that will be used once the probe arrives at Jupiter.

Rendezvous With Jupiter:

The Juno spacecraft reached the Jupiter system and established polar orbit around the gas giant on July 4th, 2016. It’s orbit will be highly elliptical and will take it close to the poles – within 4,300 km (2,672 mi) – before reaching beyond the orbit of Callisto, the most distant of Jupiter’s large moons (at an average distance of 1,882,700 km or 1,169,855.5 mi).

This orbit will allow the spacecraft to avoid long-term contact with Jupiter’s radiation belts, while still allowing it to perform close-up surveys of Jupiter’s polar atmosphere, magnetosphere and gravitational field. The spacecraft will spend the next two years orbiting Jupiter a total of 37 times, with each orbit taking 14 days.

Already, the probe has performed measurements of Jupiter’s magnetic field. This began on June 24th when Juno crossed the bow shock just outside Jupiter’s magnetosphere, followed by it’s transit into the lower density of the Jovian magnetosphere on June 25. Having made the transition from an environment characterized by solar wind to one dominated by Jupiter’s magnetosphere, the ship’s instruments revealed some interesting information about the sudden change in particle density.

The probe entered its polar elliptical orbit on July 4th after completing a 35-minute-long firing of the main engine, known as Jupiter Orbital Insertion (or JOI). As the probe approached Jupiter from above its north pole, it was afforded a view of the Jovian system, which it took a final picture of before commencing JOI.

On July 10th, the Juno probe transmitted its first imagery from orbit after powering back up its suite of scientific instruments. The images were taken when the spacecraft was 4.3 million km (2.7 million mi) from Jupiter and on the outbound leg of its initial 53.5-day capture orbit. The color image shows atmospheric features on Jupiter, including the famous Great Red Spot, and three of the massive planet’s four largest moons – Io, Europa and Ganymede, from left to right in the image.

While the mission team had hoped to reduce Juno’s orbital period to 14 days, thus allowing for it to conduct a total of 37 perijoves before mission’s end. However, due to a malfunction with the probe’s helium valves, the firing was delayed. NASA has since announced that it will not conduct this engine firing, and that the probe will conduct a total perijoves in total before the end of its mission.

End of Mission:

The Juno mission is set to conclude in February of 2018, after completing 12 orbits of Jupiter. At this point, and barring any mission extensions, the probe will be de-orbited to burn up in Jupiter’s outer atmosphere. As with the Galileo spacecraft, this is meant be to avoid any possibility of impact and biological contamination with one of Jupiter’s moons.

The mission is managed by the JPL, and its principal investigator is Scott Bolton of the Southwest Research Institute. NASA’s Launch Services Program, located at the Kennedy Space Center in Florida, is responsible for managing launch services for the probe. The Juno mission is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Ala.

As of the writing of this article, the Juno mission is one day, four hours and fifty-five minutes away from its historic arrival with Jupiter. Check out NASA’s Juno mission page to get up-to-date information on the mission, and stay tuned to Universe Today for updates!

We have written many interesting articles about Jupiter here at Universe today. Here’s Juno Blasts off on Science Trek to Discover Jupiter’s Genesis, Jupiter Bound Juno snaps Dazzling Gallery of Planet Earth Portraits, Understanding Juno’s Orbit: An Interview with NASA’s Scott Bolton, NASA’s Juno probe Gets Gravity Speed Boost during Earth Flyby But Enters ‘Safe Mode.

Astronomy cast also has relevant episodes on the subject. Here’s Episode 59: Jupiter, and Episode 232: Galileo Spacecraft,

For more information, check out NASA’s Juno mission page, and the Southwest Research Institute’s Juno page.

Posted on by Matt Williams

The Dutch Are Going To The Moon With The Chinese

Radio image of the night sky. Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.

One of the defining characteristics of the New Space era is partnerships. Whether it is between the private and public sector, different space agencies, or different institutions across the world, collaboration has become the cornerstone to success. Consider the recent agreement between the Netherlands Space Office (NSO) and the Chinese National Space Agency (CNSA) that was announced earlier this week.

In an agreement made possible by the Memorandum of Understanding (MoU) signed in 2015 between the Netherlands and China, a Dutch-built radio antenna will travel to the Moon aboard the Chinese Chang’e 4 satellite, which is scheduled to launch in 2018. Once the lunar exploration mission reaches the Moon, it will deposit the radio antenna on the far side, where it will begin to provide scientists with fascinating new views of the Universe.

The radio antenna itself is also the result of collaboration, between scientists from Radboud University, the Netherlands Institute for Radio Astronomy (ASTRON) and the small satellite company Innovative Solutions in Space (ISIS). After years of research and development, these three organizations have produced an instrument which they hope will usher in a new era of radio astronomy.

The satellite rotates around a fixed point behind the moon – the second Lagrange, or L2, point in the Earth-moon system. This point is located 65,000 kilometres from the moon.. Credit: ru.nl
Diagram showing how the Chang’e 4 satellite will rotate around a fixed point behind the moon – the second Lagrange, or L2, point in the Earth-moon system. Credit: ru.nl

Essentially, radio astronomy involves the study of celestial objects – ranging from stars and galaxies to pulsars, quasars, masers and the Cosmic Microwave Background (CMB) – at radio frequencies. Using radio antennas, radio telescopes, and radio interferometers, this method allows for the study of objects that might otherwise be invisible or hidden in other parts of the electromagnetic spectrum.

One drawback of radio astronomy is the potential for interference. Since only certain wavelengths can pass through the Earth’s atmosphere, and local radio wave sources can throw off readings, radio antennas are usually located in remote areas of the world. A good example of this is the Very-Long Baseline Array (VLBA) located across the US, and the Square Kilometer Array (SKA) under construction in Australia and South Africa.

One other solution is to place radio antennas in space, where they will not be subject to interference or local radio sources. The antenna being produced by Radbound, ASTRON and ISIS is being delivered to the far side of the Moon for just this reason. As the latest space-based radio antenna to be deployed, it will be able to search the cosmos in ways Earth-based arrays cannot, looking for vital clues to the origins of the universe.

As Heino Falke – a professor of Astroparticle Physics and Radio Astronomy at Radboud – explained in a University press release, the deployment of this radio antenna on the far side of the Moon will be an historic achievement:

“Radio astronomers study the universe using radio waves, light coming from stars and planets, for example, which is not visible with the naked eye. We can receive almost all celestial radio wave frequencies here on Earth. We cannot detect radio waves below 30 MHz, however, as these are blocked by our atmosphere. It is these frequencies in particular that contain information about the early universe, which is why we want to measure them.”

The planned Square Kilometer Array will be the world's largest radio telescope when it begins operations in 2018 Swinburne Astronomy Productions for SKA Project Development Office
The planned Square Kilometer Array will be the world’s largest radio telescope when it begins operations in 2018. Credit: SKA Project Development Office/SAP

As it stands, very little is known about this part of the electromagnetic spectrum. As a result, the Dutch radio antenna could be the first to provide information on the development of the earliest structures in the Universe. It is also the first instrument to be sent into space as part of a Chinese space mission.

Alongside Heino Falcke, Marc Klein Wolt – the director of the Radboud Radio Lab – is one of the scientific advisors for the project. For years, he and Falcke have been working towards the deployment of this radio antenna, and have high hopes for the project. As Professor Wolt said about the scientific package he is helping to create:

“The instrument we are developing will be a precursor to a future radio telescope in space. We will ultimately need such a facility to map the early universe and to provide information on the development of the earliest structures in it, like stars and galaxies.”

Together with engineers from ASTRON and ISIS, the Dutch team has accumulated a great deal of expertise from their years working on other radio astronomy projects, which includes experience working on the Low Frequency Array (LOFAR) and the development of the Square Kilometre Array, all of which is being put to work on this new project.

A radio antenna on the far side of the Moon will enable deep space surveys that were never before possible. Credit: NASA Goddard
A radio antenna on the far side of the Moon will enable deep space surveys that were never before possible. Credit: NASA Goddard

Other tasks that this antenna will perform include monitoring space for solar storms, which are known to have a significant impact on telecommunications here on Earth. With a radio antenna on the far side of the Moon, astronomers will be able to better predict such events and prepare for them in advance.

Another benefit will be the ability to measure strong radio pulses from gas giants like Jupiter and Saturn, which will help us to learn more about their rotational speed. Combined with the recent ESO efforts to map Jupiter at IR frequencies, and the data that is already arriving from the Juno mission, this data is likely to lead to some major breakthroughs in our understanding of this mysterious planet.

Last, but certainly not least, the Dutch team wants to create the first map of the early Universe using low-frequency radio data. This map is expected to take shape after two years, once the Moon has completed a few full rotations around the Earth and computer analysis can be completed.

It is also expected that such a map will provide scientists with additional evidence that confirms the Standard Model of Big Bang cosmology (aka. the Lambda CDM model). As with other projects currently in the works, the results are likely to be exciting and groundbreaking!

Further Reading: Radbound University

Posted on by Matt Williams

Behold The Distant Universe!

An image of a small section (0.4%) of the UDS field - showing a series of very distant galaxies as they appeared 9 billion years ago. Credit: Omar Almaini, University of Nottingham

This past Monday (June 27th), the National Astronomy Meeting – which is hosted by the Royal Astronomy Society – kicked off at the University of Nottingham in the UK. As one of the largest professional conferences in Europe (with over 500 scientists in attendance), this annual meeting is an opportunity for astronomers and scientists from a variety of fields to present that latest in their research.

And of the many presentations made so far, one of the most exciting came from a research team from the University of Nottingham’s School of Physics and Astronomy, which presented the latest near-infrared images obtained by the Ultra Deep Survey (UDS). In addition to being a spectacular series of pictures, they also happened to be the deepest view of the Universe to date.

The UDS survey, which began in 2005, is one of the five projects that make up the UKIRT’s Infrared Deep Sky Survey (UKIDSS). For the sake of their survey, the UDS team relies on the Wide Field Camera (WFCAM) on the United Kingdom Infrared Telescope in Mauna Kea, Hawaii. At 3.8-metres in diameter, the UKIRT is the world’s second largest telescope dedicated to infrared astronomy.

As Professor Omar Almaini, the head of the University of Nottingham research team, explained to Universe Today via email:

“The UDS is by far the deepest near-infrared survey over such a large, contiguous area (0.8 sq degrees). There is only one other similar survey, which is known as UltraVISTA. It covers a larger area (1.5 sq degree) but is not quite so deep. Together the UDS and UltraVISTA should revolutionize studies of the high-redshift Universe over the next few years.”
An optical/IR image taken by the UDS survey. Credit: nottingham.ac.uk
An optical/IR image taken with the United Kingdom Infrared Telescope as part of the UDS. Credit: nottingham.ac.uk

Ultimately, the goal of UDS is shed light on how and when galaxies form, and to chart their evolution over the course of the last 13 billion years (roughly 820 million years after the Big Bang). For over a decade, the UDS has been observing the same patch of sky repeatedly, relying on optical and infrared imaging to ensure that the light of distant objects (which is redshifted due to the profound distances involved) can be captured.

“Stars emit most of their radiation at optical wavelengths, which is redshifted to the near-infrared at high redshift,” said Almaini. “Near-infrared surveys therefore provide the least biased census of galaxies in the early Universe and the best measurements of the stellar mass. Deep optical surveys will only detect galaxies that are bright in the rest-frame ultraviolet, so they are biased against galaxies that are obscured by dust, or those that have stopped forming stars.”

In total, the project has accumulated more than 1000 hours of exposure time, detecting over two hundred and fifty thousand galaxies – several hundred of which were observed within the first billion years after the Big Bang. The final images, which were released yesterday and presented at the National Astronomy Meeting, showed an area four times the size of the full Moon, and at an unprecedented depth.

Data previously released by the UDS project has already led to several scientific advances. These include studies of the earliest galaxies in the Universe after the Big Bang, measurements on the build-up of galaxies over time, and studies of the large-scale distribution of galaxies to measure the influence of dark matter.

New research suggests that Dark Matter may exist in clumps distributed throughout our universe. Credit: Max-Planck Institute for Astrophysics
Research into the USD images is inspiring scientific research, which includes studies into dark matter. Credit: Max-Planck Institute for Astrophysics

With this latest release, many more are anticipated, with astronomers around the world spending the next few years studying the early stages of galaxy formation and evolution. As Almaini put it:

“With the UDS (and UltraVISTA) we now have the ability to study large samples of galaxies in the distant Universe, rather than just a handful. With thousands of galaxies at each epoch we can perform detailed comparisons of the evolving galaxy populations, and we can also study their large-scale structure to understand how they trace the underlying cosmic web of dark matter. With large samples we can also look for rare but important populations, such as those in transition.”

“A key aim is to understand why many massive galaxies abruptly stop forming stars around 10 billion years ago, and also how they transform from disk-like systems into elliptical galaxies. We have recently identified a few hundred examples of galaxies in the process of transformation at early times, which we are actively studying to understand what is driving the rapid changes.”

Along with the subject of galaxy surveys and large scale structure, “galaxy formation and evolution” and “galaxy surveys and large scale structure” were two of the 2016 National Astronomy Meeting’s main themes. Naturally, the UDS release fit neatly into both categories. The others themes included the Sun, stars and planetary science, gravitational waves, modified gravity, archeoastronomy, astrochemistry, and education and outreach.

The Meeting will run until tomorrow (Friday, July 1st), and also included a presentations on the latest infrared images of Jupiter, which were taken by the ESO in preparation for the Juno spacecraft’s arrival on July 4th.

Further Reading: Royal Astronomical Society

Posted on by Matt Williams

Very Large Telescope Images Of Jupiter Prepare Us For Juno Arrival

In preparation for the arrival of Juno, the ESO's released stunning IR images of Jupiter, taken by the VLT. Credit: ESO
In preparation for the arrival of Juno, the ESO's released stunning IR images of Jupiter, taken by the VLT. Credit: ESO

Launching back in 2011, NASA’s Juno mission has spent the past five years traversing the gulf that lies between Earth and Jupiter. When it arrives (in just a few days time!), it will be the second long-term mission to the gas giant in history. And in the process, it will obtain information about its composition, weather patterns, magnetic and gravitational fields, and history of formation.

With just days to go before this historic rendezvous takes place, the European Southern Observatory is taking the opportunity to release some spectacular infrared images of Jupiter. Taken with the Very Large Telescope (VLT), these images are part of a campaign to create high-resolutions maps of the planet, and provide a preview of the work that Juno will be doing in the coming months.

Using the VTL Imager and Spectrometer for mid-Infrared (VISIR) instrument, the ESO team – led by Dr. Leigh Fletcher of the University of Leicester – hopes that their efforts to map the planet will improve our understanding of Jupiter’s atmosphere. Naturally, with the upcoming arrival of Juno, some may wonder if these efforts are necessary.

The Very Large Telescoping Interferometer firing it's adaptive optics laser. Credit: ESO/G. Hüdepohl
Using images obtained by the Very Large Telescope, an ESO team managed to obtain detailed IR images of Jupiter’s atmosphere. Credit: ESO/G. Hüdepohl

After all, ground-based telescopes like the VLT are forced to contend with limitations that space-based probes are not. These include interference from our constantly-shifting atmosphere, not to mention the distances between Earth and the object in question. But in truth, the Juno mission and ground-based campaigns like these are often highly complimentary.

For one, in the past few months, while Juno was nearing in on its destination, Jupiter’s atmosphere has undergone some significant shifts. Mapping these is important to Juno‘s upcoming arrival, at which point it will be attempting to peer beneath Jupiter’s thick clouds to discern what is going on beneath. In short, the more we know about Jupiter’s shifting atmosphere, the easier it will be to interpret the Juno data.

As Dr. Fletcher described the significance of his team’s efforts:

“These maps will help set the scene for what Juno will witness in the coming months. Observations at different wavelengths across the infrared spectrum allow us to piece together a three-dimensional picture of how energy and material are transported upwards through the atmosphere.”

Like all ground-based efforts, the ESO campaign – which has involved the use of several telescopes based in Hawaii and Chile, as well as contributions from amateur astronomers around the world – faced some serious challenges (like the aforementioned interference). However, the team used a technique known as “lucky imaging” to take the breathtaking snapshots of Jupiter’s turbulent atmosphere.

This view compares a lucky imaging view of Jupiter from VISIR (left) at infrared wavelengths with a very sharp amateur image in visible light from about the same time (right). Credit: ESO/L.N. Fletcher/Damian Peach
This view compares a lucky imaging view of Jupiter from VISIR (left) at infrared wavelengths with a very sharp amateur image in visible light from about the same time (right). Credit: ESO/L.N. Fletcher/Damian Peach

What this comes down to is taking many sequences of images with very short exposures, thus producing thousands of individual frames. The lucky frames, those where the image are least affected by the atmosphere’s turbulence, are then selected while the rest discarded. These selected frames are aligned and combined to produce final pictures, like the one shown above.

In addition to providing information that would be of use to the Juno mission, the ESO’s campaign has value that extends beyond the space-based mission. As Glenn Orton, the leader of ESO’s ground-based campaign, explained, observations like these are valuable because they help to advance our understanding of planets as a whole, and provide opportunities for astronomers from all over the world to collaborate.

“The combined efforts of an international team of amateur and professional astronomers have provided us with an incredibly rich dataset over the past eight months,” he said. “Together with the new results from Juno, the VISIR dataset in particular will allow researchers to characterize Jupiter’s global thermal structure, cloud cover and distribution of gaseous species.”

The Juno probe will be arriving at Jupiter this coming Monday, July 4th. Once there, it will spend the next two years orbiting the gas giant, sending information back to Earth that will help to advance our understanding of not only Jupiter, but the history of the Solar System as well.

Further Reading: ESO

Posted on by Matt Williams

Professor Stephen Hawking Intends To Map The Known Universe

In honor of Dr. Stephen Hawking, the COSMOS center will be creating the most detailed 3D mapping effort of the Universe to date. Credit: BBC, Illus.: T.Reyes

Back in 1997, a team of leading scientists and cosmologists came together to establish the COSMOS supercomputing center at Cambridge University. Under the auspices of famed physicist Stephen Hawking, this facility and its supercomputer are dedicated to the research of cosmology, astrophysics and particle physics – ultimately, for the purpose of unlocking the deeper mysteries of the Universe.

Yesterday, in what was themed as a “tribute to Stephen Hawking”, the COSMOS center announced that it will be embarking on what is perhaps the boldest experiment in cosmological mapping. Essentially, they intend to create the most detailed 3D map of the early universe to date, plotting the position of billions of cosmic structures including supernovas, black holes, and galaxies.

This map will be created using the facility’s supercomputer, located in Cambridge’s Department of Applied Mathematics and Theoretical Physics. Currently, it is the largest shared-memory computer in Europe, boasting 1,856 Intel Xeon E5 processor cores, 31 Intel Many Integrated Core (MIC) co-processors, and 14.5 terabytes of globally shared memory.

The COSMOS IX supercomputer. Credit: cosmos.damtp.cam.ac.uk
The COSMOS IX supercomputer. Credit: cosmos.damtp.cam.ac.uk

The 3D will also rely on data obtained by two previous surveys – the ESA’s Planck satellite and the Dark Energy Survey. From the former, the COSMOS team will use the detailed images of the Cosmic Microwave Background (CMB) – the radiation leftover by the Big Ban – that were released in 2013. These images of the oldest light in the cosmos allowed physicists to refine their estimates for the age of the Universe (13.82 billion years) and its rate of expansion.

This information will be combined with data from the Dark Energy Survey which shows the expansion of the Universe over the course of the last 10 billion years. From all of this, the COSMOS team will compare the early distribution of matter in the Universe with its subsequent expansion to see how the two link up.

While cosmological simulations that looked at the evolution and large-scale structure of the Universe have been performed in the past – such as the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project and the survey performed by the Institute for the Physics and Mathematics of the Universe at Tokyo University – this will be the first time where scientists compare data the early Universe to its evolution since.

The project is also expected to receive a boost from the deployment of the ESA’s Euclid probe, which is scheduled for launch in 2020. This mission will measure the shapes and redshifts of galaxies (looking 10 billion years into the past), thereby helping scientists to understand the geometry of the “dark Universe” – i.e. how dark matter and dark energy influence it as a whole.

Artist impression of the Euclid probe, which is set to launch in 2020. Credit: ESA
Artist impression of the Euclid probe, which is set to launch in 2020. Credit: ESA

The plans for the COSMOS center’s 3D map are will be unveiled at the Starmus science conference, which will be taking place from July 2nd to 27th, 2016, in Tenerife – the largest of the Canary Islands, located off the coast of Spain. At this conference, Hawking will be discussing the details of the COSMOS project.

In addition to being the man who brought the COSMOS team together, the theme of the project – “Beyond the Horizon – Tribute to Stephen Hawking” – was selected because of Hawking’s long-standing commitment to physics and cosmology. “Hawking is a great theorist but he always wants to test his theories against observations,” said Prof. Shellard in a Cambridge press release. “What will emerge is a 3D map of the universe with the positions of billions of galaxies.”

Hawking will also present the first ever Stephen Hawking Medal for Science Communication, an award established by Hawking that will be bestowed on those who help promote science to the public through media – i.e. cinema, music, writing and art. Other speakers who will attending the event include Neil deGrasse Tyson, Chris Hadfield, Martin Rees, Adam Riess, Rusty Schweickart, Eric Betzig, Neil Turok, and Kip Thorne.

Professor Hawking, flanked by , announcing the launch of the Stephen Hawking Medal for Science Communication, Dec. 16th, 2015. Credit:
Professor Hawking and colleagues from the Royal Society announcing the launch of the Stephen Hawking Medal for Science Communication, Dec. 16th, 2015. Credit: starmus.com

Naturally, it is hoped that the creation of this 3D map will confirm current cosmological theories, which include the current age of the Universe and whether or not the Standard Model of cosmology – aka. the Lambda Cold Dark Matter (CDM) model – is in fact the correct one. As Hawking is surely hoping, this could bring us one step closer to a Theory of Everything!

Further Reading: Cambridge News

Posted on by Matt Williams

Good News, Martian Colonists Can Eat All the Radishes They Want

Screenshot from the The Martian, showing character Mark Watney tend to his Martian potato crop. Credit: Twentieth Century Fox Film Corporation

When your stated purpose is to send settlers to Mars by 2026, you’re sure to encounter a lot of skepticism. And that is exactly what Dutch entrepreneur Bas Lansdorp has been dealing with ever since he first went public with MarsOne in 2012. In fact, in the past four years, everything from the project’s schedule, technical and financial feasibility, and ethics have been criticized by scientists, engineers and people in the aerospace industry.

However, Lansdorp and his organization have persevered, stating that they intend to overcome all the challenges in sending people on a one-way trip to the Red Planet. And in their most recent statement, MarsOne has announced that they have addressed the all-important issue of what their settlers will eat. In an experiment that feels like it was ripped from the The Martian, MarsOne has completed testing different types of crops in simulated Martian soil, to see which ones could grow on Mars.

Located in the Dutch town of Nergena, MarsOne maintains a glasshouse complex where they have been conducting experiments. These experiments took place in 2013 and 2015, and involved Martian and Lunar soil simulants provided by NASA, along with Earth soil as a control group.

Artist's impression of a Martian greenhouse. Credit: NASA/Human Systems Engineering and Development Division
A conceptual rendering of a Martian greenhouse. Credit: NASA/Human Systems Engineering and Development Division

Using these, a team of ecologists and crop scientists from the Wageningen University & Research Center have been testing different kinds of seeds to see which ones will grow in a Lunar and Martian environment. These have included rye, radishes, garden cress and pea seed. And earlier this year, they added a crop of tomatoes and potatoes to the mix.

As Dr. Wieger Wamelink, the ecologist who led the experiments, told Universe Today via email:

“We started our first experiment in 2013 (published in Plos One in 2014) to investigate if it was possible to grow plants in Mars and moon soil simulants. We assume that plants will be grown indoors, because of the very harsh circumstances on both Mars and moon, very cold, no or almost no atmosphere and way to much cosmic radiation. That first experiment only had a few crops and mostly wild plants and clovers (for nitrogen binding from the atmosphere to manure the soil).”

After confirming that the seeds would germinate in the simulated soil after the first year, they then tested to see if the seeds from that harvest would germinate in the same soil to create another harvest. What they found was quite encouraging. In all four cases, the seeds managed to germinate nicely in both Martian and Lunar soil.

Researchers at Wageningen University in the Netherlands have harvested tomatoes and other vegetables grown in simulated Martian soil. Image: regan76 CC BY 2.0
Researchers at Wageningen University in the Netherlands have harvested tomatoes and other vegetables grown in simulated Martian soil. Credit: regan76 CC BY 2.0

“Our expectation were very low,” said Wamelink, “so we were very surprised that on the Mars soil simulant plants grew rather well and even better than on our nutrient poor control earth soil. There were also problems, the biggest that it was very difficult to keep the soil moist and that though on Mars soil simulant there was growth it was not very good, i.e. the amount of biomass formed was low.”

And while they didn’t grow as well as the control group, which was grown in Earth soil, they did managed to produce time and again. This was intrinsic to the entire process, in order to make sure that any crops grown on Mars would have a full life-cycle. Being able to grow crops, replant seeds, and grow more would eliminate the need to bring new seeds for every crop cycle, thus ensuring that Martian colonists could be self-sufficient when it came to food.

In 2015, they conducted their second experiment. This time around, after planting the seeds in the simulated soil, they added organic matter to simulate the addition of organic waste from a previous crop cycle. And on every Friday, when the experiments were running, they added nutrient solution to mimic the nutrients derived from fecal matter and urine (definite echoes of The Martian there!).

Once again, the results were encouraging. Once again, the crops grew, and the addition or organic matter improved the soil’s water-holding capacity. Wamelink and his team were able to harvest from many of the ten crops they had used in the experiment, procuring another batch of radishes, tomatoes and peas. The only crop that did poorly was the batch of spinach they had added.

This year, the team’s experiments were focused on the issue of food safety. As any ecologist knows, plants naturally absorb minerals from their surrounding environment. And tests have shown that soils obtained from the Moon and Mars show concentrations of heavy metals and toxins  – such as arsenic, cadmium, copper, lead, and iron (which is what gives Mars its reddish appearance). As Wamelink described the process:

“Again we have ten crops, but slightly different crops from last year; we included green beans and potatoes (best food still and Mark Watney also seems to love potatoes). Also repeated was the addition of organic matter, to mimic the addition of the plant parts that are not eaten from a previous growth cycle. Also new is the addition of liquid manure, to mimic the addition of human faeces… We know that both Mars and moon soil simulants contain heavy metals, like led, copper, mercury and chrome. The plants do not care about this, however when they end up in the eaten parts then they could poison the humans that eat them. There we have to test if it is safe to eat them.”

And again, the results were encouraging. In all cases, the crops showed that the concentrations of metals they contained were within human tolerances and therefore safe to eat. In some cases, the metal concentrations were even lower than that found those grown using potting soil.

“We now tested four species we harvested last year as a preliminary investigation and it shows that luckily there are no harmful quantities present in the fruits, so it is safe to eat them,” said Wamelink. “We will continue these analyses, because for the FDA they have to be analysed in fresh fruits and vegetables, where we did the analyses on dried material. Moreover we will also look at the content of large molecules, like vitamins, flavonoids (for the taste) and alkaloids (for toxic components).”

However, the Wageningen UR team hopes to test all ten of the crops they have grown in order to make sure that everything grown in Martian soil will be safe to eat. Towards this end, Wageningen UR has set up a crowdfunding campaign to finance their ongoing experiments. With public backing, they hope to show that future generations will be able to be self-sufficient on Mars, and not have to worry about things like arsenic and lead poisoning.

As an incentive, donors will receive a variety of potential gifts, which include samples of the soil simulant used for the experiment. But the top prize, a a dinner based on the harvest, is being offered to people contributing €500 ($555.90 USD) or more. In what is being called the first “Martian meal” this dinner will take place once the experiment is complete and will of course include Martian potatoes!

Looking ahead, Wamelink and his associates also hope to experiment crops that do not rely on a seed-to-harvest cycle, and are not harvested annually.These include fruit trees so that they might be able to grow apples, cherries, and strawberries in Martian soil. In addition, Wamelink has expressed interest in cultivating lupin seeds as a means of replacing meat in the Martian diet.

And when it comes right down to it, neither MarsOne or the Wageningen UR team are alone in wanting to see what can be grown on Mars or other planets. For years, NASA has also been engaged in their own tests to see which crops can be cultivated on Mars. And with the help of the Lima-based International Potato Center, their latest experiment involves cultivating potatoes in samples of Peruvian soil.

Artist's concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One
Artist’s concept of a Martian astronaut standing outside the Mars One habitat. Credit: Bryan Versteeg/Mars One

For hundreds of years, the Andean people have been cultivating potatoes in the region. And given the arid conditions, NASA believes it will serve as a good facsimile for Mars. But perhaps the greatest draw is the fact cultivating potatoes in a simulated Martian environment immediately calls to mind Matt Damon in The Martian. In short, it’s a spectacular PR move that NASA, looking to drum up support for its “Journey to Mars“, cannot resist!

Naturally, experiments such as these are not just for the sake of meeting the challenges posed by MarsOne’s plan for one-way crewed missions to Mars. Alongside the efforts of NASA and others, they are part of a much larger effort to address the challenges posed by the renewed era of space exploration we find ourselves embarking on.

With multiple space agencies and private corporations (like SpaceX) hoping to put buts back on the Moon and Mars, and to establish permanent bases on these planets and even in the outer Solar System, knowing what it will take for future generations of colonists and explorers to sustain themselves is just good planning.

Further Reading: Mars Exchange

Posted on by Matt Williams

A Star Is About To Go 2.5% The Speed Of Light Past A Black Hole

Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way. Credit: ESO

Since it was first discovered in 1974, astronomers have been dying to get a better look at the Supermassive Black Hole (SBH) at the center of our galaxy. Known as Sagittarius A*, scientists have only been able to gauge the position and mass of this SBH by measuring the effect it has on the stars that orbit it. But so far, more detailed observations have eluded them, thanks in part to all the gas and dust that obscures it.

Luckily, the European Southern Observatory (ESO) recently began work with the GRAVITY interferometer, the latest component in their Very Large Telescope (VLT). Using this instrument, which combines near-infrared imaging, adaptive-optics, and vastly improved resolution and accuracy, they have managed to capture images of the stars orbiting Sagittarius A*. And what they have observed was quite fascinating.

One of the primary purposes of GRAVITY is to study the gravitational field around Sagittarius A* in order to make precise measurements of the stars that orbit it. In so doing, the GRAVITY team – which consists of astronomers from the ESO, the Max Planck Institute, and multiple European research institutes – will be able to test Einstein’s theory of General Relativity like never before.

The core of the Milky Way. Credit: NASA/JPL-Caltech/S. Stolovy (SSC/Caltech)
Spitzer image of the core of the Milky Way Galaxy. Credit: NASA/JPL-Caltech/S. Stolovy (SSC/Caltech)

In what was the first observation conducted using the new instrument, the GRAVITY team used its powerful interferometric imaging capabilities to study S2, a faint star which orbits Sagittarius A* with a period of only 16 years. This test demonstrated the effectiveness of the GRAVITY instrument – which is 15 times more sensitive than the individual 8.2-metre Unit Telescopes the VLT currently relies on.

This was an historic accomplishment, as a clear view of the center of our galaxy is something that has eluded astronomers in the past. As GRAVITY’s lead scientist, Frank Eisenhauer – from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany – explained to Universe Today via email:

“First, the Galactic Center is hidden behind a huge amount of interstellar dust, and it is practically invisible at optical wavelengths. The stars are only observable in the infrared, so we first had to develop the necessary technology and instruments for that. Second, there are so many stars concentrated in the Galactic Center that a normal telescope is not sharp enough to resolve them. It was only in the late 1990′ and in the beginning of this century when we learned to sharpen the images with the help of speckle interferometry and adaptive optics to see the stars and observe their dance around the central black hole.”

But more than that, the observation of S2 was very well timed. In 2018, the star will be at the closest point in its orbit to the Sagittarius A*  – just 17 light-hours from it. As you can see from the video below, it is at this point that S2 will be moving much faster than at any other point in its orbit (the orbit of S2 is highlighted in red and the position of the central black hole is marked with a red cross).

When it makes its closest approach, S2 will accelerate to speeds of almost 30 million km per hour, which is 2.5% the speed of light. Another opportunity to view this star reach such high speeds will not come again for another 16 years – in 2034. And having shown just how sensitive the instrument is already, the GRAVITY team expects to be able make very precise measurements of the star’s position.

In fact, they anticipate that the level of accuracy will be comparable to that of measuring the positions of objects on the surface of the Moon, right down to the centimeter-scale. As such, they will be able to determine whether the motion of the star as it orbits the black hole are consistent with Einstein’s theories of general relativity.

“[I]t is not the speed itself to cause the general relativistic effects,” explained Eisenhauer, “but the strong gravitation around the black hole. But the very  high orbital speed is a direct consequence and measure of the gravitation, so we refer to it in the press release because the comparison with the speed of light and the ISS illustrates so nicely the extreme conditions.

Artist's impression of the influence gravity has on space time. Credit: space.com
Artist’s impression of the influence gravity has on space-time. Credit: space.com

As recent simulations of the expansion of galaxies in the Universe have shown, Einstein’s theories are still holding up after many decades. However, these tests will offer hard evidence, obtained through direct observation. A star traveling at a portion of the speed of light around a supermassive black hole at the center of our galaxy will certainly prove to be a fitting test.

And Eisenhauer and his colleagues expect to see some very interesting things. “We hope to see a “kick” in the orbit.” he said. “The general relativistic effects increase very strongly when you approach the black hole, and when the star swings by, these effects will slightly change the direction of the
orbit.”

While those of us here at Earth will not be able to “star gaze” on this occasion and see R2 whipping past Sagittarius A*, we will still be privy to all the results. And then, we just might see if Einstein really was correct when he proposed what is still the predominant theory of gravitation in physics, over a century later.

Further Reading: eso.org

Posted on by Matt Williams

What are the Different Masses of the Planets?

Planets and other objects in our Solar System. Credit: NASA.

It is a well known fact that the planets of the Solar System vary considerably in terms of size. For instance, the planets of the inner Solar System are smaller and denser than the gas/ice giants of the outer Solar System. And in some cases, planets can actually be smaller than the largest moons. But a planet’s size is not necessarily proportional to its mass. In the end, how massive a planet is has more to do with its composition and density.

So while a planet like Mercury may be smaller in size than Jupiter’s moon Ganymede or Saturn’s moon Titan, it is more than twice as massive than they are. And while Jupiter is 318 times as massive as Earth, its composition and density mean that it is only 11.21 times Earth’s size. Let’s go over the planet’s one by one and see just how massive they are, shall we?

Mercury:

Mercury is the Solar System’s smallest planet, with an average diameter of 4879 km (3031.67 mi). It is also one of its densest at 5.427 g/cm3, which is second only to Earth. As a terrestrial planet, it is composed of silicate rock and minerals and is differentiated between an iron core and a silicate mantle and crust. But unlike its peers (Venus, Earth and Mars), it has an abnormally large metallic core relative to its crust and mantle.

All told, Mercury’s mass is approximately 0.330 x 1024 kg, which works out to 330,000,000 trillion metric tons (or the equivalent of 0.055 Earths). Combined with its density and size, Mercury has a surface gravity of 3.7 m/s² (or 0.38 g).

Internal structure of Mercury: 1. Crust: 100–300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius. Credit: MASA/JPL
Internal structure of Mercury: 1. Crust: 100–300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius. Credit: MASA/JPL

Venus:

Venus, otherwise known as “Earth’s Sister Planet”, is so-named because of its similarities in composition, size, and mass to our own. Like Earth, Mercury and Mars, it is a terrestrial planet, and hence quite dense. In fact, with a density of 5.243 g/cm³, it is the third densest planet in the Solar System (behind Earth and Mercury). Its average radius is roughly 6,050 km (3759.3 mi), which is the equivalent of 0.95 Earths.

And when it comes to mass, the planet weighs in at a hefty 4.87 x 1024 kg, or 4,870,000,000 trillion metric tons. Not surprisingly, this is the equivalent of 0.815 Earths, making it the second most massive terrestrial planet in the Solar System. Combined with its density and size, this means that Venus also has comparable gravity to Earth – roughly 8.87 m/s², or 0.9 g.

Earth:

Like the other planets of the inner Solar System, Earth is also a terrestrial planet, composed of metals and silicate rocks differentiated between an iron core and a silicate mantle and crust. Of the terrestrial planets, it is the largest and densest, with an average radius of 6,371.0 km (3,958.8 mi) and a mean of density of 5.514 g/cm3.

The Earth's layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com

And at 5.97 x 1024 kg (which works out to 5,970,000,000,000 trillion metric tons) Earth is the most massive of all the terrestrial planets. Combined with its size and density, Earth experiences the surface gravity that we are all familiar with – 9.8 m/s², or 1 g.

Mars:

Mars is the third largest terrestrial planet, and the second smallest planet in our Solar System. Like the others, it is composed of metals and silicate rocks that are differentiated between a iron core and a silicate mantle and crust. But while it is roughly half the size of Earth (with a mean diameter of 6792 km, or 4220.35 mi), it is only one-tenth as massive.

In short, Mars has a mass of 0.642 x1024 kg, which works out to 642,000,000 trillion metric tons, or roughly 0.11 the mass of Earth. Combined with its size and density – 3.9335 g/cm³ (which is roughly 0.71 times that of Earth’s) – Mars has a surface gravity of 3.711 m/s² (or 0.376 g).

Jupiter:

Jupiter is the largest planet in the Solar System. With a mean diameter of 142,984 km, it is big enough to fit all the other planets (except Saturn) inside itself, and big enough to fit Earth 11.8 times over. But with a mass of 1898 x 1024 kg (or 1,898,000,000,000 trillion metric tons), Jupiter is more massive than all the other planets in the Solar System combined – 2.5 times more massive, to be exact.

upiter's structure and composition. (Image Credit: Kelvinsong CC by S.A. 3.0)
Jupiter’s structure and composition. (Image Credit: Kelvinsong CC by S.A. 3.0)

However, as a gas giant, it has a lower overall density than the terrestrial planets. It’s mean density is 1.326 g/cm, but this increases considerably the further one ventures towards the core. And though Jupiter does not have a true surface, if one were to position themselves within its atmosphere where the pressure is the same as Earth’s at sea level (1 bar), they would experience a gravitational pull of 24.79 m/s2 (2.528 g).

Saturn:

Saturn is the second largest of the gas giants; with a mean diameter of 120,536 km, it is just slightly smaller than Jupiter. However, it is significantly less massive than its Jovian cousin, with a mass of 569 x 1024 kg (or 569,000,000,000 trillion metric tons). Still, this makes Saturn the second most-massive planet in the Solar System, with 95 times the mass of Earth.

Much like Jupiter, Saturn has a low mean density due to its composition. In fact, with an average density of 0.687 g/cm³, Saturn is the only planet in the Solar System that is less dense than water (1 g/cm³).  But of course, like all gas giants, its density increases considerably the further one ventures towards the core. Combined with its size and mass, Saturn has a “surface” gravity that is just slightly higher than Earth’s – 10.44 m/s², or 1.065 g.

Diagram of Saturn's interior. Credit: Kelvinsong/Wikipedia Commons
Diagram of Saturn’s interior. Credit: Kelvinsong/Wikipedia Commons

Uranus:

With a mean diameter of 51,118 km, Uranus is the third largest planet in the Solar System. But with a mass of 86.8 x 1024 kg (86,800,000,000 trillion metric tons) it is the fourth most massive – which is 14.5 times the mass of Earth. This is due to its mean density of 1.271 g/cm3, which is about three quarters of what Neptune’s is. Between its size, mass, and density, Uranus’ gravity works out to 8.69 m/s2, which is 0.886 g.

Neptune:

Neptune is significantly larger than Earth; at 49,528 km, it is about four times Earth’s size. And with a mass of 102 x 1024 kg (or 102,000,000,000 trillion metric tons) it is also more massive – about 17 times more to be exact. This makes Neptune the third most massive planet in the Solar System; while its density is the greatest of any gas giant (1.638 g/cm3). Combined, this works out to a “surface” gravity of 11.15 m/s2 (1.14 g).

As you can see, the planets of the Solar System range considerably in terms of mass. But when you factor in their variations in density, you can see how a planets mass is not always proportionate to its size. In short, while some planets may be a few times larger than others, they are can have many, many times more mass.

We have written many interesting articles about the planets here at Universe. For instance, here’s Interesting Facts About the Solar System, What are the Colors of the Planets?, What are the Signs of the Planets?, How Dense are the Planets?, and What are the Diameters of the Planets?.

For more information, check out Nine Planets overview of the Solar System, NASA’s Solar System Exploration, and use this site to find out what you would weigh on other planets.

Astronomy Cast has episodes on all of the planets. Here’s Episode 49: Mercury to start!

Posted on by Matt Williams

Centaurs Keep Their Rings From Greedy Gas Giants

Artist's impression of what the rings of the asteroid Chariklo would look like from the small body's surface. The rings' discovery was a first for an asteroid. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)

When we think of ring systems, what naturally comes to mind are planets like Saturn. It’s beautiful rings are certainly the most well known, but they are not the only planet in our Solar System to have them. As the Voyager missions demonstrated, every planet in the outer Solar System – from Jupiter to Neptune – has its own system of rings. And in recent years, astronomers have discovered that even certain minor planets – like the Centaur asteroids 10199 Chariklo and 2006 Chiron – have them too.

This was a rather surprising find, since these objects have such chaotic orbits. Given that their paths through the Solar System are frequently altered by the powerful gravity of gas giants, astronomers have naturally wondered how a minor planet could retain a system of rings. But thanks to a team of researchers from the Sao Paulo State University in Brazil, we may be close to answering that question.

In a study titled “The Rings of Chariklo Under Close Encounters With The Giant Planets“, which appeared recently in The Astrophysical Journal, they explained how they constructed a model of the Solar System that incorporated 729 simulated objects. All of these objects were the same size as Chariklo and had their own system of rings. They then went about the process of examining how interacting with gas giant effected them.

Artist's impression of rings around the asteroid Chariklo. This was the first asteroid where rings were discovered. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)
Artist’s impression of rings around the Centaur Chariklo, the first asteroid where rings were discovered. Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)

To break it down, Centaurs are a population of objects within our Solar System that behave as both comets and asteroids (hence why they are named after the hybrid beasts of Greek mythology). 10199 Chariklo is the largest known member of the Centaur population, a possible former Trans-Neptunian Object (TNO) which currently orbits between Saturn and Uranus.

The rings around this asteroid were first noticed in 2013 when the asteroid underwent a stellar occultation. This revealed a system of two rings, with a radius of 391 and 405 km and widths of about 7 km 3 km, respectively. The absorption features of the rings showed that they were partially composed of water ice. In this respect, they were much like the rings of Jupiter, Saturn, Uranus and the other gas giants, which are composed largely of water ice and dust.

This was followed by findings made in 2015 that indicated that 2006 Chiron – another major Centaur – could have a ring of its own. This led to further speculation that there might be many minor planets in our Solar System that have a system of rings. Naturally, this was a bit perplexing to astronomers, since rings are fragile structures that were thought to be exclusive to the gas giants of our System.

As Professor Othon Winter, the lead researcher of the Sao Paulo team, told Universe Today via email:

“At first it was a surprise to find a Centaur with rings, since the Centaurs have chaotic orbits wandering between the giant planets and having frequent close encounters with them. However, we have shown that in most of the cases the ring system can survive all the close encounters with the giant planets. Therefore,  Centaurs with rings might be much more common than we thought before.”

Arist's impression of Chiron and its possible ring. Credit: dailygalaxy.com
Artist’s impression of Chiron, showing a possible ring system. Credit: dailygalaxy.com

For the sake of their study, Winter and his colleagues considered the orbits of 729 simulated clones of Chariklo as they orbited the Sun over the course of 100 million years. From this, Winter and his colleagues found that each Centaur averaged about 150 close encounters with a gas giant, within one Hill radius of the planet in question. As Winter described it:

“The study was made in two steps. First we considered a set of more than 700 clones of Chariklo. The clones had initial trajectories that were slightly different from Chariklo for statistical purposes (since we are dealing with chaotic trajectories) and computationally simulated their orbital evolution forward in time (to see their future) and also backward in time (to see their past). During these simulations we archived the information of all the close encounters (many thousands) they had with each of the giant planets.”

“In the second step, we performed simulations of each one of the close encounters found in the first step, but now including a disk of particles around Chariklo  (representing the ring particles). Then, at the end of each simulation we analyzed what happened to the particles. Which ones were removed from Chariklo  (escaping its gravitational field)? Which ones were strongly disturbed (still orbiting around Chariklo)? Which ones did not suffer any significant effect?”

In the end, the simulations showed that in 90 percent of the cases, the rings of the Centaurs survived their close encounters with gas giants, whereas they were disturbed in 4 percent of cases, and were stripped away only 3 percent of the time. Thus, they concluded that if there is an efficient mechanism that creates the rings, then it is strong enough to let Centaurs keep them.

Due to their dual nature, astronomers refer to asteroids that behave as both comets and asteroids as Centaurs. Credit: jpl.nasa.gov
Due to their dual nature, the name Centaur has stuck when referring to objects that act as both comets and asteroids. Credit: jpl.nasa.gov

More than that, their research would seem to indicate that what was considered unique to certain planetary bodies may actually be more commonplace. “It reveals that our Solar System is complex not just as whole or for large bodies,” said Winter, “but even small bodies may show complex structures and even more complex temporal evolution.”

The next step for the research team is to study ring formation, which could show that they in fact picking them up from the gas giants themselves. But regardless of where they come from, its becoming increasingly clear that Centaurs like 10199 Chariklo are not alone. What’s more, they aren’t giving up their rings anytime soon!

Further Reading: iopscience.iop.org