An artist's illustration of the Cassini probe's Grand Finale. Image: NASA/JPL/CalTech
In 1997, the NASA/ESA Cassini-Huygens mission launched from Earth and began its long journey towards the Saturn system. In 2004, the Cassini orbiter arrived around Saturn and would spend the next thirteen years studying the gas giant, its rings, and its system of Moons. On September 15th, 2017, the mission ended when the probe entered Saturn’s upper atmosphere and burned up.
This was known as Cassini’s “Grand Finale“, which began with the probe plunging into the unexplored region that lies between Saturn’s atmosphere and its rings and culminated with live coverage of it entering the atmosphere. In honor of the mission and NASA’s outstanding coverage of its final months, NASA was recently nominated for an Emmy Award by The Academy of Television Arts & Sciences.
The award is in the category of Outstanding Original Interactive Program, which recognizes the JPL’s multi-month digital campaign that celebrated the mission’s science and engineering accomplishments – which included news, web, education, television and social media efforts. It is also a nod to the agency’s success in communicating why the spacecraft concluded its mission in the skies of Saturn.
Essentially, the spacecraft was intentionally destroyed in Saturn’s atmosphere to prevent the possibility of it contaminating any of Saturn’s moons. Throughout the thirteen years it spent studying the Saturn system, Cassini found compelling evidence for the possible existence of life on Titan and in Enceladus’ interior ocean. In addition, scientists have speculated that there may be interior oceans within Rhea and Dione.
In this respect, Cassini ended its mission the same way the Galileo probe did in 2003. After spending 8 years studying Jupiter and its system the moons, the probe crashed into the gas giant’s upper atmosphere in order to prevent any possible contamination of Europa or Ganymede, which are also thought to have an interior oceans that could support life.
The “Grand Finale” campaign began on April 26th, 2017, and continued until the craft entered Saturn’s atmosphere on Sept. 15th, 2017, with the spacecraft sending back science to the very last second. The campaign utilized several different forms of media, was interactive, and was very comprehensive, providing regular updates and vital information about the mission.
“The multi-faceted campaign included regular updates on Twitter, Facebook, Snapchat, Instagram and the Cassini mission website; multiple live social, web and TV broadcasts during which reporter and public questions were answered; a dramatic short film to communicate the mission’s story and preview its endgame; multiple 360-degree videos, including NASA’s first 360-degree livestream of a mission event from inside JPL mission control; an interactive press kit; a steady drumbeat of articles to keep fans updated with news and features about the people behind the mission; state-standards aligned educational materials; a celebration of art by amateur space enthusiasts; and software to provide real-time tracking of the spacecraft, down to its final transmission to Earth.”
The short film, titled “For Your Consideration: The NASA Cassini Grand Finale“, showcases the missions many accomplishments, pays tribute to all those who made it happen and who helped inform the public and communicate the importance of the mission.
The Primetime Emmys will be awarded be on September 17th in Los Angeles. The Creative Arts Emmys, which includes interactive awards, will be presented during a separate ceremony on Saturday, Sept. 15th, at the Microsoft Theatre in Los Angeles. Other contenders include Back to the Moon, a Google Spotlight Stories App; Blade Runner 2049: Memory Lab, Coco VR, and Spiderman Homecoming, three Oculus VR experiences.
And be sure to check out the videos, FYC: NASA Cassini Grand Finale, below:
Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser
On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Originally though to be a comet, follow-up observations conducted by the European Southern Observatory (ESO) and others confirmed that ‘Oumuamua was actually a rocky body that had originated outside of our Solar System.
Since that time, multiple studies have been conducted to learn more about this interstellar visitor, and some missions have even been proposed to go and study it up close. However, the most recent study of ‘Oumuamua, conducted by a team of international scientists, has determined that based on the way it left our Solar System, ‘Oumuamua is likely to be a comet after all.
As noted, when it was first discovered – roughly a month after it made its closest approach to the Sun – scientists believed ‘Oumuamua was an interstellar comet. However, follow-up observations showed no evidence of gaseous emissions or a dusty environment around the body (i.e. a comet tail), thus leading to it being classified as a rocky interstellar asteroid.
This was followed by a team of international researchers conducting a study that showed how ‘Oumuamua was more icy that previously thought. Using the ESO’s Very Large Telescope in Chile and the William Herschel Telescope in La Palma, the team was able to obtain spectra from sunlight reflected off of ‘Oumuamua within 48 hours of the discovery. This revealed vital information about the composition of the object, and pointed towards it being icy rather than rocky.
The presence of an outer-layer of carbon rich material also explained why it did not experience outgassing as it neared the Sun. Following these initial observations, Marco Micheli and his team continued to conduct high-precision measurements of ‘Oumuamua and its position using ground-based facilities and the NASA/ESA Hubble Space Telescope.
By January, Hubble was able to snap some final images before the object became too faint to observe as it sped away from the Sun on its way to leaving the Solar System. To their surprise, they noted that the object was increasing its velocity deviating from the trajectory it would be following if only the gravity of the Sun and the planets were influencing its course.
Oumuamua as it appeared using the William Herschel Telescope on the night of October 29. Queen’s University Belfast/William Herschel Telescope
In short, they discovered that ‘Oumuamua was not slowing down as expected, and as of June 1st, 2018, was traveling at a speed of roughly 114,000 km/h (70,800 mph). The most likely explanation, according to the team, is that ‘Oumuamua is venting material from its surface due to solar heating (aka. outgassing). The release of this material would give ‘Oumuamua the steady push it needed to achieve this velocity.
As Davide Farnocchia, a researcher from NASA’s Jet Propulsion Laboratory and a co-author on the paper, explained in a recent ESA press release:
“We tested many possible alternatives and the most plausible one is that ’Oumuamua must be a comet, and that gasses emanating from its surface were causing the tiny variations in its trajectory.”
Moreover, the release of gas pressure would also explain how ‘Oumuamua is veering off course since outgassing has been known to have the effect of perturbing the comet’s path. Naturally, there are still some mysteries that still need to be solved about this body. For one, the team still has not detected any dusty material or chemical signatures that typically characterize a comet.
As such, the team concluded that ‘Oumuamua must have been releasing only a very small amount of dust, or perhaps was releasing more pure gas without much dust. In either case, ‘Oumuamua is estimated to be a very small object, measuring about 400 meters (1312 ft) long. In the end, the hypothesized outgassing of ‘Oumuamua remains a mystery, much like its origin.
Artist’s impression of the interstellar object, ‘Oumuamua, experiencing outgassing as it leaves our Solar System. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser
In fact, the team originally performed the Hubble observations on ‘Oumuamua in the hopes of determining its exact path, which they would then use to trace the object back to its parent star system. These new results mean this will be more challenging than originally thought. As Olivier Hainaut, a researcher from the European Southern Observatory and a co-author on the study, explained:
“It was extremely surprising that `Oumuamua first appeared as an asteroid, given that we expect interstellar comets should be far more abundant, so we have at least solved that particular puzzle. It is still a tiny and weird object, but our results certainly lean towards it being a comet and not an asteroid after all.”
Detlef Koschny, another co-author on the study, is responsible for Near-Earth Object activities under ESA’s Space Situational Awareness program. As he explained, the study of ‘Oumuamua has provided astronomers with the opportunity to improve asteroid detection methods, which could play a vital role in the study of Near-Earth Asteroids and determining if they post a risk.
“Interstellar visitors like these are scientifically fascinating, but extremely rare,” he said. “Near-Earth objects originating from within our Solar System are much more common and because these could pose an impact risk, we are working to improve our ability to scan the sky every night with telescopes such as our Optical Ground Station that contributed to this fascinating discovery.”
Since ‘Oumuamua’s arrival, scientists have determined that there may be thousands of interstellar asteroids currently in our Solar System, the largest of which would be tens of km in radius. Similarly, another study was conducted that revealed the presence of an interstellar asteroid (2015 BZ509) that – unlike ‘Oumuamua, which was an interloper to out system – was captured by Jupiter’s gravity and has since remained in a stable orbit.
This latest study is also timely given the fact that June 30th is global “Asteroid Day”, an annual event designed to raise awareness about asteroids and what can be done to protect Earth from a possible impact. In honor of this event, the ESA co-hosted a live webcast with the European Southern Observatory to discuss the latest science news and research on asteroids. To watch a replay of the webcast, go to the ESA’s Asteroid Day webpage.
Cryvolcanism at Enceladus, a moon of Satury. This Cassini narrow-angle camera image looks across the south pole of Enceladus and its geysers of material. Credit: NASA/JPL-Caltech/Space Science Institute
The Cassini orbiter revealed many fascinating things about the Saturn system before its mission ended in September of 2017. In addition to revealing much about Saturn’s rings and the surface and atmosphere of Titan (Saturn’s largest moon), it was also responsible for the discovery of water plumes coming from Enceladus‘ southern polar region. The discovery of these plumes triggered a widespread debate about the possible existence of life in the moon’s interior.
This was based in part on evidence that the plumes extended all the way to the moon’s core/mantle boundary and contained elements essential to life. Thanks to a new study led by researchers from of the University of Heidelberg, Germany, it has now been confirmed that the plumes contain complex organic molecules. This is the first time that complex organics have been detected on a body other than Earth, and bolsters the case for the moon supporting life.
The “tiger stripes” of Enceladus, as pictured by the Cassini space probe. Credit: NASA/JPL/ESA
The existence of a liquid water ocean in Enceladus’ interior has been the subject of scientific debate since 2005, when Cassini first observed plumes containing water vapor spewing from the moon’s south polar surface through cracks in the surface (nicknamed “Tiger Stripes”). According to measurements made by the Cassini-Huygens probe, these emissions are composed mostly of water vapor and contain molecular nitrogen, carbon dioxide, methane and other hydrocarbons.
The combined analysis of imaging, mass spectrometry, and magnetospheric data also indicated that the observed southern polar plumes emanate from pressurized subsurface chambers. This was confirmed by the Cassini mission in 2014 when the probe conducted gravity measurements that indicated the existence of a south polar subsurface ocean of liquid water with a thickness of around 10 km.
Shortly before the probe plunged into Saturn’s atmosphere, the probe also obtained data that indicated that the interior ocean has existed for some time. Thanks to previous readings that indicated the presence of hydrothermal activity in the interior and simulations that modeled the interior, scientists concluded that if the core were porous enough, this activity could have provided enough heat to maintain an interior ocean for billions of years.
However, all the previous studies of Cassini data were only able to identify simple organic compounds in the plume material, with molecular masses mostly below 50 atomic mass units. For the sake of their study, the team observed evidence of complex macromolecular organic material in the plumes’ icy grains that had masses above 200 atomic mass units.
Hydrothermal activity in Enceladus’ core and the rise of organic-rich bubbles. Credit and Copyright: ESA; F. Postberg et al (2018)
This constitutes the first-ever detection of complex organics on an extraterrestrial body. As Dr. Khawaja explained in a recent ESA press release:
“We found large molecular fragments that show structures typical for very complex organic molecules. These huge molecules contain a complex network often built from hundreds of atoms of carbon, hydrogen, oxygen and likely nitrogen that form ring-shaped and chain-like substructures.”
The molecules that were detected were the result of the ejected ice grains hitting the dust-analyzing instrument aboard Cassini at speeds of about 30,000 km/hour. However, the team believes that these were mere fragments of larger molecules contained beneath Enceladus’ icy surface. As they state in their study, the data suggests that there is a thin organic-rich film on top of the ocean.
These large molecules would be the result of by complex chemical processes, which could be those related to life. Alternately, they may be derived from primordial material similar to what has been found in some meteorites or (as the team suspects) that is generated by hydrothermal activity. As Dr. Postberg explained:
“In my opinion the fragments we found are of hydrothermal origin, having been processed inside the hydrothermally active core of Enceladus: in the high pressures and warm temperatures we expect there, it is possible that complex organic molecules can arise.”
Artist rendering showing an interior cross-section of the crust of Enceladus, which shows how hydrothermal activity may be causing the plumes of water at the moon’s surface. Credits: NASA-GSFC/SVS, NASA/JPL-Caltech/Southwest Research Institute
As noted, recent simulations have shown the moon could be generating enough heat through hydrothermal activity for its interior ocean to have existed for billions of years. This study follows up on that scenario by showing how organic material could be injected into the ocean by hydrothermal vents. This is similar to what happens on Earth, a process that scientists believe may have played a vital role in the origins of life on our planet.
On Earth, organic substances are able to accumulate on the walls of rising air bubbles created by hydrothermal vents, which then rise to the surface and are dispersed by sea spray and the bubbles bursting. Scientists believe a similar process is happening on Enceladus, where bubbles of gas rising through the ocean could be bringing organic materiel up from the core-mantle boundary to the icy surface.
When these bubbles burst at the surface, it helps disperse some of the organics which then become part of the salty spray coming through the tiger cracks. This spray then freezes into icy particles as it reaches space, sending organic material and ice throughout the Saturn System, where it has now been detected. If this study is correct, then another fundamental ingredient for life is present in Enceladus’ interior, making the case for life there that much stronger.
This is just the latest in a long-line of discoveries made by Cassini, many of which point to the potential existence of life on or in some of Saturn’s moons. In addition to confirming the first organic molecules in an “ocean world” of our Solar System, Cassini also found compelling evidence of a rich probiotic environment and organic chemistry on Titan.
In the future, multiple missions are expected to return to these moons to gather more evidence of potential life, picking up where the venerable Cassini left off. So long Cassini, and thanks for blazing a trail!
ESA's Solar Orbiter will capture the very first images of the Sun’s polar regions, where magnetic tension builds up and releases in a lively dance. Credits: Spacecraft: ESA/ATG medialab; Sun: NASA/SDO/P. Testa (CfA)
Our understanding of distant stars has increased dramatically in recent decades. Thanks to improved instruments, scientists are able to see farther and clearer, thus learning more about star systems and the planets that orbit them (aka. extra-solar planets). Unfortunately, it will be some time before we develop the necessary technology to explore these stars up close.
But in the meantime, NASA and the ESA are developing missions that will allow us to explore our own Sun like never before. These missions, NASA’s Parker Solar Probe and the ESA’s (the European Space Agency) Solar Orbiter, will explore closer to the Sun than any previous mission. In so doing, it is hoped that they will resolve decades-old questions about the inner workings of the Sun.
These missions – which will launch in 2018 and 2020, respectively – will also have significant implications for life here on Earth. Not only is sunlight essential to life as we know it, solar flares can pose a major hazard for technology that humanity is becoming increasingly dependent on. This includes radio communications, satellites, power grids and human spaceflight.
And in the coming decades, Low-Earth Orbit (LEO) is expected to become increasingly crowded as commercial space stations and even space tourism become a reality. By improving our understanding of the processes that drive solar flares, we will therefore be able to better predict when they will occur and how they will impact Earth, spacecraft, and infrastructure in LEO.
As Chris St. Cyr, the Solar Orbiter project scientist at NASA’s Goddard Space Flight Center, explained in a recent NASA press release:
“Our goal is to understand how the Sun works and how it affects the space environment to the point of predictability. This is really a curiosity-driven science.”
Both missions will focus on the Sun’s dynamic outer atmosphere, otherwise known as the corona. At present, much of the behavior of this layer of the Sun is unpredictable and not well understood. For instance, there’s the so-called “coronal heating problem”, where the corona of the Sun is so much hotter than the solar surface. Then there is the question of what drives the constant outpouring of solar material (aka. solar wind) to such high speeds.
As Eric Christian, a research scientist on the Parker Solar Probe mission at NASA Goddard, explained:
“Parker Solar Probe and Solar Orbiter employ different sorts of technology, but — as missions — they’ll be complementary. They’ll be taking pictures of the Sun’s corona at the same time, and they’ll be seeing some of the same structures — what’s happening at the poles of the Sun and what those same structures look like at the equator.”
Illustration of the Parker Solar Probe spacecraft approaching the Sun. Credits: Johns Hopkins University Applied Physics Laboratory
For its mission, the Parker Solar Probe will get closer to the Sun than any spacecraft in history – as close as 6 million km (3.8 million mi) from the surface. This will replace the previous record of 43.432 million km (~27 million mi), which was established by the Helios B probe in 1976. From this position, the Parker Solar Probe will use its four suites of scientific instruments to image the solar wind and study the Sun’s magnetic fields, plasma and energetic particles.
In so doing, the probe will help clarify the true anatomy of the Sun’s outer atmosphere, which will help us to understand why the corona is hotter than the Sun’s surface. Basically, while temperatures in the corona can reach as high as a few million degrees, the solar surface (aka. photosphere), experiences temperatures of around 5538 °C (10,000 °F).
Meanwhile, the Solar Orbiter will come to a distance of about 42 million km (26 million mi) from the Sun, and will assume a highly-tilted orbit that can provide the first-ever direct images of the Sun’s poles. This is another area of the Sun that scientists don’t yet understand very well, and the study of it could provide valuable clues as to what drives the Sun’s constant activity and eruptions.
Both missions will also study solar wind, which is the Sun’s most pervasive influence on the solar system. This steam of magnetized gas fills the inner Solar System, interacting with magnetic fields, atmospheres and even the surfaces of planets. Here on Earth, it is what is responsible for the Aurora Borealis and Australis, and can also play havoc with satellites and electrical systems at times.
Artist’s impression of a solar flare erupting from the Sun’s surface. Credit: NASA Goddard Space Flight Center
Previous missions have led scientists to believe that the corona contributes to the process that accelerates solar wind to such high speeds. As these charged particles leave the Sun and pass through the corona, their speed effectively triples. By the time the solar wind reaches the spacecraft responsible for measuring it – 148 million km (92 million mi) from the Sun – it has plenty of time to mix with other particles from space and lose some of its defining features.
By being parked so close to the Sun, the Parker Solar Probe will able to measure the solar wind just as it forms and leaves the corona, thus providing the most accurate measurements of solar wind ever recorded. From its perspective above the Sun’s poles, the Solar Orbiter will complement the Parker Solar Probe’s study of the solar wind by seeing how the structure and behavior of solar wind varies at different latitudes.
This unique orbit will also allow the Solar Orbiter to study the Sun’s magnetic fields, since some of the Sun’s most interesting magnetic activity is concentrated at the poles. This magnetic field is far-reaching largely because of solar wind, which reaches outwards to create a magnetic bubble known as the heliosphere. Within the heliosphere, solar wind has a profound effect on planetary atmospheres and its presence protects the inner planets from galactic radiation.
In spite of this, it is still not entirely clear how the Sun’s magnetic field is generated or structured deep inside the Sun. But given its position, the Solar Orbiter will be able to study phenomena that could lead to a better understanding of how the Sun’s magnetic field is generated. These include solar flares and coronal mass ejections, which are due to variability caused by the magnetic fields around the poles.
In this way, the Parker Solar Probe and Solar Orbiter are complimentary missions, studying the Sun from different vantage points to help refine our knowledge of the Sun and heliosphere. In the process, they will provide valuable data that could help scientists to tackle long-standing questions about our Sun. This could help expand our knowledge of other star systems and perhaps even answer questions about the origins of life.
As Adam Szabo, a mission scientist for Parker Solar Probe at NASA Goddard, explained:
“There are questions that have been bugging us for a long time. We are trying to decipher what happens near the Sun, and the obvious solution is to just go there. We cannot wait — not just me, but the whole community.”
In time, and with the development of the necessary advanced materials, we might even be able to send probes into the Sun. But until that time, these missions represent the most ambitious and daring efforts to study the Sun to date. As with many other bold initiatives to study our Solar System, their arrival cannot come soon enough!
From ground-based telescopes, the so-called "ant nebula" (Menzel 3, or Mz 3) resembles the head and thorax of a garden-variety ant. This dramatic NASA/ESA Hubble Space Telescope image, showing 10 times more detail, reveals the "ant's" body as a pair of fiery lobes protruding from a dying, Sun-like star. Credit: NASA/ESA/Hubble Heritage Team (STScI/AURA)
When low- to middleweight stars like our Sun approach the end of their life cycles they eventually cast off their outer layers, leaving behind a dense, white dwarf star. These outer layers became a massive cloud of dust and gas, which is characterized by bright colors and intricate patterns, known as a planetary nebula. Someday, our Sun will turn into such a nebula, one which could be viewed from light-years away.
This process, where a dying star gives rise to a massive cloud of dust, was already known to be incredibly beautiful and inspiring thanks to many images taken by Hubble. However, after viewing the famous Ant Nebula with the European Space Agency’s (ESA) Herschel Space Observatory, a team of astronomers discovered an unusual laser emission that suggests that there is a double star system at the center of the nebula.
The life cycle of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant on the right after billions of years. Credit: ESO/M. Kornmesser
The Ant Nebula (aka. Mz 3) is a young bipolar planetary nebula located in the constellation Norma, and takes its name from the twin lobes of gas and dust that resemble the head and body of an ant. In the past, this nebula’s beautiful and intricate nature was imaged by the NASA/ESA Hubble Space Telescope. The new data obtained by Herschel also indicates that the Ant Nebula beams intense laser emissions from its core.
In space, infrared laser emissions are detected at very different wavelengths and only under certain conditions, and only a few of these space lasers are known. Interestingly enough, it was astronomer Donald Menzel – who first observed and classified the Ant Nebula in 1920 (hence why it is officially known as Menzel 3 after him) – who was one of the first to suggest that lasers could occur in nebula.
According to Menzel, under certain conditions natural “light amplification by the stimulated emissions of radiation” (aka. where we get the term laser from) would occur in space. This was long before the discovery of lasers in laboratories, an occasion that is celebrated annually on May 16th, known as UNESCO’s International Day of Light. As such, it was highly appropriate that this paper was also published on May 16th, celebrating the development of the laser and its discoverer, Theodore Maiman.
As Isabel Aleman, the lead author of a paper, described the results:
“When we observe Menzel 3, we see an amazingly intricate structure made up of ionized gas, but we cannot see the object in its center producing this pattern. Thanks to the sensitivity and wide wavelength range of the Herschel observatory, we detected a very rare type of emission called hydrogen recombination line laser emission, which provided a way to reveal the nebula’s structure and physical conditions.”
Artist’s impression of the Herschel Space Telescope. Credit: ESA/AOES Medialab/NASA/ESA/STScI
“Such emission has only been identified in a handful of objects before and it is a happy coincidence that we detected the kind of emission that Menzel suggested, in one of the planetary nebulae that he discovered,” she added.
The kind of laser emission they observed needs very dense gas close to the star. By comparing observations from the Herschel observatory to models of planetary nebula, the team found that the density of the gas emitting the lasers was about ten thousand times denser than the gas seen in typical planetary nebulae, and in the lobes of the Ant Nebula itself.
Normally, the region close to the dead star – in this case, roughly the distance between Saturn and the Sun – is quite empty because its material was ejected outwards after the star went supernova. Any lingering gas would soon fall back onto it. But as Professor Albert Zijlstra, from the Jodrell Bank Center for Astrophysics and a co-author on the study, put it:
“The only way to keep such dense gas close to the star is if it is orbiting around it in a disc. In this nebula, we have actually observed a dense disc in the very center that is seen approximately edge-on. This orientation helps to amplify the laser signal. The disc suggests there is a binary companion, because it is hard to get the ejected gas to go into orbit unless a companion star deflects it in the right direction. The laser gives us a unique way to probe the disc around the dying star, deep inside the planetary nebula.”
The planetary nebula Abell 39. According to a new study, our Sun will similarly become a luminous planetary nebula by the end of its life cycle. Credit: WIYN/NOAO/NSF
While astronomers have not yet seen the expected second star, they are hopeful that future surveys will be able to locate it, thus revealing the origin of the Ant Nebula’s mysterious lasers. In so doing, they will be able to connect two discoveries (i.e. planetary nebula and laser) made by the same astronomer over a century ago. As Göran Pilbratt, ESA’s Herschel project scientist, added:
“This study suggests that the distinctive Ant Nebula as we see it today was created by the complex nature of a binary star system, which influences the shape, chemical properties, and evolution in these final stages of a star’s life. Herschel offered the perfect observing capabilities to detect this extraordinary laser in the Ant Nebula. The findings will help constrain the conditions under which this phenomenon occurs, and help us to refine our models of stellar evolution. It is also a happy conclusion that the Herschel mission was able to connect together Menzel’s two discoveries from almost a century ago.”
Next-generation space telescopes that could tell us more about planetary nebula and the life-cycles of stars include the James Webb Space Telescope (JWST). Once this telescope takes to space in 2020, it will use its advanced infrared capabilities to see objects that are otherwise obscured by gas and dust. These studies could reveal much about the interior structures of nebulae, and perhaps shed light on why they periodically shoot out “space lasers”.
Using information from Gaia's second data release, a team of scientists have made refined estimates of the Milky Way's mass. Credit: ESA/Gaia/DPAC
In 2013, the European Space Agency (ESA) deployed the Gaia mission, a space observatory designed to measure the positions of movements of celestial bodies. For the past four years, Gaia has been studying distant stars, planets, comets, asteroids, quasars and other astronomical objects, and the data it has acquired will be used to construct the largest and most precise 3D space catalog ever made, totaling 1 billion objects.
The second release of Gaia data, which took place on April 25th, 2018, has already resulted in a number of impressive discoveries. The latest was made by an international team of scientists who identified 13,928 white dwarfs within 100 parsecs (326 light-years) of the Sun, many of which were formed through mergers. This is the first time that white dwarf stars have been directly detected within the Solar neighborhood.
Artist impression of colliding white dwarfs. Credit: CfA
Basically, white dwarfs are what become of the majority of stars (with masses less than 8 Solar masses) once they exit the main sequence phase of their lives. This consists of a star exhausting its hydrogen fuel and expanding to several times its size (entering its Red Giant Branch Phase). These stars then blow off their external layers (a supernova) and leaving behind a white dwarf remnant.
By studying them, astronomers can learn far more about the life cycle of stars and how they evolve. As Dr. Kilic explained to Universe Today via email:
“[W]e’re basically doing Galactic archaeology when we study nearby white dwarfs. They tell us about the ages and star formation histories of the Galactic disk and halo. More importantly, white dwarfs explode as a Type Ia supernova when they reach 1.4 times the mass of the Sun. We use these supernovae to study the shape of the Universe and conclude that the expansion of the universe is accelerating. However, we have not yet found the progenitor systems of these supernovae. One of the channels to form Type Ia supernovae is through mergers of white dwarfs. Hence, the direct detection of merged white dwarfs is important for understanding the frequency of these white dwarf mergers.”
However, until recently only a few hundred white stars have been found within the local galactic neighborhood (500 within a 40 parsec radius). In addition, astronomers were only able to obtain accurate parallax (distance) measurements for about half of these. But thanks to the Gaia data, the number of white dwarfs systems that astronomers are able to study has increased exponentially.
Artist’s impression of a white dwarf star in orbit around Sirius (a white supergiant). Credit: NASA, ESA and G. Bacon (STScI)
“Gaia provided distance measurements,” said Kilic. “We can now create complete samples of white dwarfs within a given volume. For example, prior to Gaia, we only knew about 100 white dwarfs within 20 parsecs of the Sun. With Gaia Data Release 2, we identified more than 13,000 white dwarfs within 100 parsecs of the Sun. The difference in numbers is amazing!”
The Gaia data was also helpful in determining the nature of these white dwarf systems and how they formed. As they indicate in their study, previous research has shown that the majority of white dwarf stars in our local galaxy (roughly 56%) are the product of single-star evolution, whereas 7 to 23% were the product of mergers between binaries. The remainder were white dwarf binaries, or binaries with one white dwarf and a main sequence star.
Using the Gaia data – which included the color and distribution data of thousands of white dwarf stars within ~326 light-years of the Sun – the team was able to determine how massive these stars are. This, in turn, provided vital clues as to how they formed, which indicated that mergers were far more common than previous studies suggested. As Kilic explained:
“Massive white dwarfs tend to be smaller, which means that they are also fainter (since they have a smaller surface area). Since Gaia gave us a complete sample of white dwarfs within 100 parsecs of the Sun, for the first time, we were able to derive the magnitude distribution (hence the mass distribution) of thousands of white dwarfs and find a large fraction of massive white dwarfs. We see that the number of massive white dwarfs is significantly higher than expected from single star evolution. Therefore, we concluded that many of these massive white dwarfs actually formed through mergers in previously binary systems.”
Artist’s impression of white dwarf binary pair CSS 41177. Credit: Andrew Taylor.
From this, the team was able to assemble the first reliable Hertzsprung-Russell Diagram for nearby field white dwarf stars, as well as estimates on how often white dwarf binaries merge. As Kilic indicated, this could have significant implications for other areas of astronomical study.
“Based on the frequency of these single white dwarfs that formed through mergers, we can estimate how many white dwarf mergers occur on average and with what mass distribution,” he said. “We can then infer the rate of Type Ia supernovae from these mergers and see if it’s enough to explain part or all of the Ia supernova explosions. This is an ongoing area of research and I’m sure we will some results on these very soon.”
These findings are yet another gem to come from the second Gaia data release, which has proven to be a treasure trove for astronomers. The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).
Rotation of the Large Magellanic Cloud, as revealed by the ESA's Gaia spacecraft. Copyright: ESA/Gaia/DPAC
On December 19th, 2013, the European Space Agency’s (ESA) Gaia spacecraft took to space with for a very ambitious mission. Over the course of its planned 5-year mission (which was recently extended), this space observatory would map over a billion stars, planets, comets, asteroids and quasars in order to create the largest and most precise 3D catalog of the Milky Way ever created.
Since that time, the ESA has made two data releases that cover the first three years of the Gaia mission. The second data release, which took on April 25th, 2018, has already proven to be a treasure trove for astronomers. In addition to the positions, distance indicators and motions of over a billion stars and celestial objects in the Milky Way Galaxy, it also contained a hidden gem – the proper motions of stars within the Large Magellanic Cloud (LMC).
Located about 200,000 light-years from Earth, the LMC has dense clouds of dust that results in it experiencing high rates of star formation. In addition, it’s central bar is warped (where the east and west ends are nearer to the Milky Way), suggesting that it was once a barred dwarf spiral galaxy who’s spiral arms were disrupted by interaction with the Small Magellanic Cloud (SMC) and the Milky Way.
The proper motions of the stars in the LMC, as captured by the Gaia spacecraft (without color). Copyright: ESA/Gaia/DPAC
For these reasons, astronomers have been hoping to derive the orbits of dwarf galaxies (and globular clusters) that revolve around the Milky Way. In so doing, they hope to learn more about how our galaxy evolved due to mergers with clusters and other galaxies. By determining the proper motions of the LMC’s stars, the Gaia mission has provided clues as to how the Milky Way and its largest satellite galaxy have interacted over time.
As you can see from the image (at top), the bar of the LMC is outlined in great detail, along with individual star-forming regions like the Tarantula Nebula (aka. 30 Doradus, which is visible just above the center of the galaxy). The image combines the total amount of radiation detected by the observatory in each pixel. The radiation measurements were then taken through different filters on the spacecraft to generate color information.
This allowed Gaia to obtain information about the total density of stars within the LMC as well as their proper motions. As you can see, the image is dominated by the brightest, most massive stars, which greatly outshine their fainter, lower-mass counterparts. The proper motions of the stars observed is represented as the texture of the image – which looks a lot like a fingerprint.
The Large Magellanic Cloud (LMC), one of the nearest galaxies to our Milky Way, as viewed by ESA’s Gaia satellite using information from the mission’s second data release. Copyright ESA/Gaia/DPAC
From this, scientists were able to see an imprint of the stars rotating clockwise around the center of the galaxy. Using this information, astronomers will be able to create new models on how the LMC, SMC, and Milky Way evolved together over time. This, in turn, could shed light on how galaxies like our own, formed and evolved over the course of billions of years.
As with other information contained in the first and second data releases, this latest discovery demonstrates that the Gaia mission is fulfilling its intended purpose. The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).
And be sure to enjoy this animated view of the LMC’s rotation, courtesy of the ESA:
On October 19th, 2016, the European Space Agency’s Exobiology on Mars (ExoMars) mission established orbit around Mars. Consisting of the ExoMars Trace Gas Orbiter (TGO) and the Schiaparelli lander, the purpose of this mission is to investigate Mars for past signs of life. And whereas the Schiaparelli unfortunately crashed during deployment, the TGO has managed to begin its mission ahead of schedule.
A few weeks ago, the satellite achieved a near circular orbit around Mars after performing a series of braking maneuvers. Since that time, the orbiter’s Color and Stereo Surface Imaging System (CaSSIS) took a stunning image of the surface. This picture was not only the TGO’s first image of Mars, it was also a test to see if the orbiter is ready to being its main mission on April 28th.
The image captured a 40 km- (25 mi) long segment of the Korolev Crater, which is located high in Mars’ northern hemisphere. The image was a composite of three images in different colors that were taken simultaneously on April 15th, 2018, which were then assembled to produce this color image. The bright material that appears at the edge of the crater is water ice.
The ExoMars Colour and Stereo Surface Imaging System, CaSSIS, captured this view of the rim of Korolev crater (73.3ºN/165.9ºE). Copyright ESA/Roscosmos/CaSSIS
As Antoine Pommerol, a member of the CaSSIS science team working on the calibration of the data, explained in a recent ESA press release:
“We were really pleased to see how good this picture was given the lighting conditions. It shows that CaSSIS can make a major contribution to studies of the carbon dioxide and water cycles on Mars.”
Prior to the test phase, the camera team transmitted new software to the TGO, and after a few minor issues, they determined that the instrument was ready to work. The camera is one of four instruments on the TGO, which also carries two spectrometer suites and a neutron detector. The spectrometers began their science mission on April 21st by taking the first sample of the atmosphere to see how its molecules absorb sunlight.
By doing this, the TGO hopes to determine the chemical composition of Mars atmosphere and find evidence of methane and other trace atmospheric gases that could be signatures of active biological or geological processes. Eventually, the camera will help characterize features on the surface that could be related to trace gas sources. Hence the importance of this recent test.
ExoMars’ Trace Gas Orbiter (TGO) and Schiaparelli lander seperating in orbit of Mars. Credit: ESA/ATG medialab
“We aim to fully automate the image production process,” said Nicolas Thomas, the camera’s principal investigator from the University of Bern. “Once we achieve this, we can distribute the data quickly to the science community for analysis.”
A lot of challenges lie ahead, which includes a long period of data collection to bring out the details of rare (or yet to be discovered) trace gases in Mars’ atmosphere. This is necessary since trace gases (as the name would suggest) are present in only very small amounts – i.e. less than 1% of the volume of the planet’s atmosphere. But as Håkan Svedhem – the ESA’s TGO project scientist – indicated, the test image was a good start.
“We are excited to finally be starting collecting data at Mars with this phenomenal spacecraft,” he said. “The test images we have seen so far certainly set the bar high.”
By 2020, the second part of the ExoMars mission is scheduled to launch. This will consist of a Russian surface platform and a European rover landing on the surface in support of a science mission that is expected to last into 2022 or longer. Alongside NASA’s proposed Mars 2020 rover, the Red Planet is due to have several more visitors in the coming years!
Using information from Gaia's second data release, a team of scientists have made refined estimates of the Milky Way's mass. Credit: ESA/Gaia/DPAC
On December 19th, 2013, the European Space Agency’s (ESA) Gaia spacecraft took to space with one of the most ambitious missions ever. Over the course of its planned 5-year mission (which was recently extended), this space observatory would map over a billion stars, planets, comets, asteroids and quasars in order to create the largest and most precise 3D catalog of the Milky Way ever created.
The first release of Gaia data, which took place in September 2016, contained the distances and motions of over two million stars. But the second data release, which took place on April 25th, 2018, is even more impressive. Included in the release are the positions, distance indicators and motions of more than one billion stars, asteroids within our Solar System, and even stars beyond the Milky Way.
Whereas the first data release was based on just over a year’s worth of observations, the new data release covers a period of about 22 months – which ran from July 25th, 2014, to May 23rd, 2016. Preliminary analysis of this data has revealed fine details about 1.7 billion stars in the Milky Way and how they move, which is essential to understanding how our galaxy evolved over time.
ESA’s Gaia is currently on a five-year mission to map the stars of the Milky Way. Image credit: ESA/ATG medialab; background: ESO/S. Brunier.
As Günther Hasinger, the ESA Director of Science, explained in a recent ESA press release:
“The observations collected by Gaia are redefining the foundations of astronomy. Gaia is an ambitious mission that relies on a huge human collaboration to make sense of a large volume of highly complex data. It demonstrates the need for long-term projects to guarantee progress in space science and technology and to implement even more daring scientific missions of the coming decades.“
The precision of Gaia‘s instruments has allowed for measurements that are so accurate that it was possible to separate the parallax of stars – the apparent shift caused by the Earth’s orbit around the Sun – from their movements through the galaxy. Of the 1.7 billion stars cataloged, the parallax and velocity (aka. proper motion) of more than 1.3 billion were measured and listed.
For about 10% of these, the parallax measurements were so accurate that astronomers can directly estimate distances to the individual stars. As Anthony Brown of Leiden University, who is also the chair of the Gaia Data Processing and Analysis Consortium Executive Board, explained:
“The second Gaia data release represents a huge leap forward with respect to ESA‘s Hipparcos satellite, Gaia‘s predecessor and the first space mission for astrometry, which surveyed some 118 000 stars almost thirty years ago… The sheer number of stars alone, with their positions and motions, would make Gaia‘s new catalogue already quite astonishing. But there is more: this unique scientific catalogue includes many other data types, with information about the properties of the stars and other celestial objects, making this release truly exceptional.“
In addition to the proper motions of stars, the catalog provides information on a wide range of topics that will be of interest to astronomers and astrophysicists. These include brightness and color measurements of nearly all of the 1.7 billion stars cataloged, as well as information on how the brightness and color change for half a million variable stars over time.
It also contains the velocities along the line of sight of seven million stars, the surface temperatures of about 100 million, and the effect interstellar dust has on 87 million. The Gaia data also contains information on objects in our Solar System, which includes the positions of 14,000 known asteroids (which will allow for the precise determination of their orbits).
Beyond the Milky Way, Gaia obtained more accurate measurements of the positions of half a million distant quasars – bright galaxies that emit massive amounts of energy due to the presence of a supermassive black hole at their centers. In the past, quasars have been used as a reference frame for the celestial coordinates of all objects in the Gaia catalogue based on radio waves.
However, this information will now be available at optical wavelengths for the first time. This, and other developments made possible by Gaia, could revolutionize how we study our galaxy and the Universe. As Antonella Vallenari, from the Istituto Nazionale di Astrofisica (INAF), the Astronomical Observatory of Padua, Italy, and the deputy chair of the Data Processing Consortium Executive Board, indicated:
“The new Gaia data are so powerful that exciting results are just jumping at us. For example, we have built the most detailed Hertzsprung-Russell diagram of stars ever made on the full sky and we can already spot some interesting trends. It feels like we are inaugurating a new era of Galactic archaeology.“
The Hertzsprung-Russell diagram, which is named after the two astronomers who devised it in the early 20th century, is fundamental to the study of stellar populations and their evolution. Based on four million stars that were selected from the catalog (all of which are withing five thousand light-years from the Sun), scientist were able to reveal many fine details about stars beyond our Solar System for the first time.
Along with measurements of their velocities, the Gaia Hertzsprung-Russell diagram enables astronomers to distinguish between populations of stars that are of different ages, are located in different regions of the Milky Way (i.e. the disk and the halo), and that formed in different ways. These include fast moving stars that were previously thought to belong to the halo, but are actually part of two stellar populations.
“Gaia will greatly advance our understanding of the Universe on all cosmic scales,” said Timo Prusti, a Gaia project scientist at ESA. “Even in the neighborhood of the Sun, which is the region we thought we understood best, Gaia is revealing new and exciting features.”
For instance, for a subset of stars within a few thousand light-years of the Sun, Gaia measured their velocity in all three dimensions. From this, it has been determined that they follow a similar pattern to stars that are orbiting the galaxy at similar speeds. The cause of these patterns will be the subject of future research, as it is unclear whether its caused by our galaxy itself or are the result of interactions with smaller galaxies that merged with us in the past.
Last, but not least, Gaia data will be used to learn more about the orbits of 75 globular clusters and 12 dwarf galaxies that revolve around the Milky Way. This information will shed further light on the evolution of our galaxy, the gravitational forces affecting it, and the role played by dark matter. As Fred Jansen, the Gaia mission manager at ESA, put it:
“Gaia is astronomy at its finest. Scientists will be busy with this data for many years, and we are ready to be surprised by the avalanche of discoveries that will unlock the secrets of our Galaxy.“
The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year). A series of scientific papers describing what has been learned from this latest release will also appear in a special issue of Astronomy & Astrophysics.
From the evolution of stars to the evolution of our galaxy, the second Gaia data release is already proving to be a boon for astronomers and astrophysicists. Even after the mission concludes, we can expect scientists will still be analyzing the data and learning a great deal more about the structure and evolution of our Universe.
A single frame from the animation created by twitter user landru79. The images were taken by the Rosetta spacecraft of 67P on June 1st, 2016. Credit: Europeans Space Agency -ESAC
The European Space Agency’s Rosetta mission was an ambitious one. As the first-ever space probe to rendezvous with and then orbit a comet, Rosetta and its lander (Philae) revealed a great deal about the comet 67p/Churyumov-Gerasimenko. In addition to the learning things about the comet’s shape, composition and tail, the mission also captured some incredible images of the comet’s surface before it ended.
For instance, Rosetta took a series of images on June 1st, 2016, that showed what looks like a blizzard on the comet’s surface. Using these raw images (which were posted on March 22nd, 2018), twitter user landru79 created an eye-popping video that shows just what it would be like to stand on the comet’s surface. As you can see, its like standing in a blizzard on Earth, though scientists have indicated that it’s a little more complicated than that.
The video, which consists of 25 minutes worth of images taken by Rosetta’s Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS), was posted by landru79 on April 23rd, 2018. It shows the surface of 67p/Churyumov-Gerasimenko on the loop, which lends it the appearance of panning across the surface in the middle of a snowstorm.
#ROSETTA ? OSIRIS #67P/CHURYUMOV-GERASIMENKO new albums ?–ROSETTA EXTENSION 2 MTP030– Miércoles 1 Junio 2016 all filters stacked pic.twitter.com/Bf173Z5g79
However, according to the ESA, the effect is likely caused by three separate phenomena. For instance, the snow-like particles seen in the video are theorized to be a combination of dust from the comet itself as well as high-energy particles striking the camera. Because of OSIRIS’ charge-coupled device (CCD) – a radiation-sensing camera – even invisible particles appear like bright streaks when passing in front of it.
As for the white specks in the background, those are stars belonging to the Canis Major constellation (according to ESA senior advisor Mark McCaughrean). Since originally posting the video, landru79 has posted another GIF on Twitter (see below) that freezes the starfield in place. This makes it clearer that the comet is moving, but the stars are remaining still (at least, relative to the camera’s point of view).
And of course, the entire video has been sped up considerably for dramatic effect. According to a follow-up tweet posted by landru79, the first image was shot on June 1st, 2016 at 3.981 seconds past 17:00 (UTC) while the last one was shot at 170.17 seconds past 17:25.
Si apilamos todo el set alineando con las estrellas de fondo se distingue mejor que son estrellas y q es polvo (olvidaos de rayos cósmicos ) #ROSETTA ? OSIRIS #67P/CHURYUMOV-GERASIMENKO new albums ?–ROSETTA EXTENSION 2 MTP030– Miércoles 1 Junio 2016 all filters stacked? pic.twitter.com/UyZ628JxKP
Still, one cannot deny that it is both captivating and draws attention to what Rosetta the mission accomplished. The mission launched in 2004 and reached 67P/Churyumov-Gerasimenko in 2014. After two years of gathering data, it was deliberately crashed on its surface in 2016. And yet, years later, what it revealed is still captivating people all over the world.
