A recent study published in The Astrophysical Journal Letters examines a rare alloy molecule known as chromium hydride (CrH) and its first-time confirmation on an exoplanet, in this case, WASP-31 b. Traditionally, CrH is only found in large quantities between 1,200 to 2,000 degrees Kelvin (926.85 to 1,726.85 degrees Celsius/1700 to 3,140 degrees Fahrenheit) and used to ascertain the temperature of cool stars and brown dwarfs. Therefore, astronomers like Dr. Laura Flagg in the Department of Astronomy and Carl Sagan Institute at Cornell University refer to CrH as a “thermometer for stars”.Continue reading “Astronomers Confirm First Exoplanet “Thermometer Molecule” that is Typically Used to Study Brown Dwarfs”
In a recent study published in Science Advances, a team of researchers commissioned the Hobby-Eberly Telescope (HET), which is designed to study exoplanetary atmospheres, to examine how a “hot Jupiter” exoplanet is losing its helium atmosphere as it orbits its parent star, leaving tails of helium that extend approximately 25 times the diameter of the planet itself.Continue reading “This Hot Jupiter is Leaving a Swirling Tail of Helium in its Wake”
Mercury is the speed champion in our Solar System. It orbits the Sun every 88 days, and its average speed is 47 km/s. Its average distance from the Sun is 58 million km (36 million mi), and it’s so fast it’s named after Mercury, the wing-footed God.
But what if instead of Mercury, Jupiter was closest to the Sun? And what if Jupiter was even closer to the Sun than Mercury and far hotter?Continue reading “Astronomers Find a Planet That Orbits its Star in Just 16 HOURS!”
The field of extrasolar planet research has advanced by leaps and bounds over the past fifteen years. To date, astronomers have relied on space-based and ground-based telescopes to confirm the existence of 4,566 exoplanets in 3,385 systems, with another 7,913 candidates awaiting confirmation. More importantly, in the past few years, the focus of exoplanet studies has slowly shifted from the process of discovery towards characterization.
In particular, astronomers are making great strides when it comes to the characterization of exoplanet atmospheres. Using the Gemini South Telescope (GST) in Chile, an international team led by Arizona State University (ASU) was able to characterize the atmosphere of a “hot Jupiter” located 340 light-years away. This makes them the first team to directly measure the chemical composition of a distant exoplanet’s atmosphere, a significant milestone in the hunt for habitable planets beyond our Solar System.Continue reading “Astronomers Measure the Atmosphere on a Planet Hundreds of Light-Years Away”
Astronomers estimate that in about four billion years, our Sun will exit the main sequence phase of its existence and become a red giant. This will consist of the Sun running out of hydrogen and expanding to several times its current size. This will cause Earth to become uninhabitable since this Red Giant Sun will either blow away Earth’s atmosphere (rendering the surface uninhabitable) or expand to consume Earth entirely.
In a lot of ways, Earth is getting off easy with these predicted scenarios. Other planets, such as WASP-12b, don’t have the luxury of waiting billions of years for their star to reach the end of its lifespan before eating them up. According to a recent study by a team of Princeton-led astrophysicists, this extrasolar planet is spiraling in towards its star and will be consumed in a fiery death just 3 million years from now.Continue reading “In About 3 Million Years, WASP-12b Will Spiral into its Star and be Consumed”
In the past decade, thousands of planets have been discovered beyond our Solar System. These planets have provided astronomers with the opportunity to study planetary systems that have defied our preconcieved notions. This includes particularly massive gas giants that are many times the size of Jupiter (aka. “super-Jupiters”). And then there are those that orbit particularly close to their suns, otherwise known as “hot-Jupiters”.
Conventional wisdom indicates that gas giants should exist far from their suns and have long orbital periods that can last for a decade or longer. However, in a recent study, an international team of astronomers announced the detection of a “hot-Jupiter” with the shortest orbital period to date. Located 1,060 light-years away from Earth, this planet (NGTS-10b) takes just 18 hours to complete a full orbit of its sun.Continue reading “Exoplanet Orbits its Star Every 18 Hours. The Quickest Hot-Jupiter Ever Found”
When it comes to how and where planetary systems form, astronomers thought they had a pretty good handle on things. The predominant theory, known as the Nebular Hypothesis, states that stars and planets form from massive clouds of dust and gas (i.e. nebulae). Once this cloud experiences gravitational collapse at the center, its remaining dust and gas forms a protoplanetary disk that eventually accretes to form planets.
However, when studying the distant star NGTS-1 – an M-type (red dwarf) located about 600 light-years away – an international team led by astronomers from the University of Warwick discovered a massive “hot Jupiter” that appeared far too large to be orbiting such a small star. The discovery of this “monster planet” has naturally challenged some previously-held notions about planetary formation.
The study, titled “NGTS-1b: A hot Jupiter transiting an M-dwarf“, recently appeared in the Monthly Notices of the Royal Astronomical Society. The team was led by Dr Daniel Bayliss and Professor Peter Wheatley from the University of Warwick and included members from the of the Geneva Observatory, the Cavendish Laboratory, the German Aerospace Center, the Leicester Institute of Space and Earth Observation, the TU Berlin Center for Astronomy and Astrophysics, and multiple universities and research institutes.
The discovery was made using data obtained by the ESO’s Next-Generation Transit Survey (NGTS) facility, which is located at the Paranal Observatory in Chile. This facility is run by an international consortium of astronomers who come from the Universities of Warwick, Leicester, Cambridge, Queen’s University Belfast, the Geneva Observatory, the German Aerospace Center, and the University of Chile.
Using a full array of fully-robotic compact telescopes, this photometric survey is one of several projects meant to compliment the Kepler Space Telescope. Like Kepler, it monitors distant stars for signs of sudden dips in brightness, which are an indication of a planet passing in front of (aka. “transiting”) the star, relative to the observer. When examining data obtained from NGTS-1, the first star to be found by the survey, they made a surprising discovery.
Based on the signal produced by its exoplanet (NGTS-1b), they determined that it was a gas giant roughly the same size as Jupiter and almost as massive (0.812 Jupiter masses). Its orbital period of 2.6 days also indicated that it orbits very close to its star – about 0.0326 AU – which makes it a “hot Jupiter”. Based on these parameters, the team also estimated that NGTS-1b experiences temperatures of approximately 800 K (530°C; 986 °F).
The discovery threw the team for a loop, as it was believed to be impossible for planets of this size to form around small, M-type stars. In accordance with current theories about planet formation, red dwarf stars are believed to be able to form rocky planets – as evidenced by the many that have been discovered around red dwarfs of late – but are unable to gather enough material to create Jupiter-sized planets.
As Dr. Daniel Bayliss, an astronomer with the University of Geneva and the lead-author on the paper, commented in University of Warwick press release:
“The discovery of NGTS-1b was a complete surprise to us – such massive planets were not thought to exist around such small stars. This is the first exoplanet we have found with our new NGTS facility and we are already challenging the received wisdom of how planets form. Our challenge is to now find out how common these types of planets are in the Galaxy, and with the new NGTS facility we are well-placed to do just that.”
What is also impressive is the fact that the astronomers noticed the transit at all. Compared to other classes of stars, M-type stars are the smallest, coolest and dimmest. In the past, rocky bodies have been detected around them by measuring shifts in their position relative to Earth (aka. the Radial Velocity Method). These shifts are caused by the gravitational tug of one or more planets that cause the planet to “wobble” back and forth.
In short, the low light of an M-type star has made monitoring them for dips in brightness (aka. the Transit Method) highly impractical. However, using the NGTS’s red-sensitive cameras, the team was able to monitored patches of the night sky for many months. Over time, they noticed dips coming from NGTS-1 every 2.6 days, which indicated that a planet with a short orbital period was periodically passing in front of it.
They then tracked the planet’s orbit around the star and combined the transit data with Radial Velocity measurements to determine its size, position and mass. As Professor Peter Wheatley (who leads NGTS) indicated, finding the planet was painstaking work. But in the end, its discovery could lead to the detection of many more gas giants around low-mass stars:
“NGTS-1b was difficult to find, despite being a monster of a planet, because its parent star is small and faint. Small stars are actually the most common in the universe, so it is possible that there are many of these giant planets waiting to found. Having worked for almost a decade to develop the NGTS telescope array, it is thrilling to see it picking out new and unexpected types of planets. I’m looking forward to seeing what other kinds of exciting new planets we can turn up.”
Within the known Universe, M-type stars are by far the most common, accounting for 75% of all stars in the Milky Way Galaxy alone. In the past, the discovery of rocky bodies around stars like Proxima Centauri, LHS 1140, GJ 625, and the seven rocky planets around TRAPPIST-1, led many in the astronomical community to conclude that red dwarf stars were the best place to look for Earth-like planets.
The discovery of a Hot Jupiter orbiting NGTS-1 is therefore seen as an indication that other red dwarf stars could have orbiting gas giants as well. Above all, this latest find once again demonstrates the importance of exoplanet research. With every find we make beyond our Solar System, the more we learn about the ways in which planets form and evolve.
Every discovery we make also advances our understanding of how likely we may be to discover life out there somewhere. For in the end, what greater scientific goal is there than determining whether or not we are alone in the Universe?
The discovery of extra-solar planets has certainly heated up in the past few years. With the deployment of the Kepler mission in 2009, several thousands of exoplanet candidates have been discovered and over 2,500 have been confirmed. In many cases, these planets have been gas giants orbiting close to their respective stars (aka. “Hot Jupiters”), which has confounded some commonly-held notions of how and where planets form.
Beyond these massive planets, astronomers also discovered a wide range of planets that range from massive terrestrial planets (“Super-Earths) to Neptune-sized giants. In a recent study, an international team astronomers discovered three new exoplanets orbiting three different stars. These planets are an interesting batch of finds, consisting of two “Hot Saturns” and one Super-Neptune.
This study, titled “The discovery of WASP-151b, WASP-153b, WASP-156b: Insights on giant planet migration and the upper boundary of the Neptunian desert“, recently appeared in the scientific journal Astronomy and Astrophysics. Led by Olivier. D. S. Demangeon, a researcher from the Institute of Astrophysics and Space Science in Portugal, the team used data from the SuperWASP exoplanet-hunting survey to detect signs of three new gas giants.
The Super Wide Angle Search for Planets (SuperWASP) is an international consortium that uses wide-angle Transit Photometry to monitor the night sky for transit events. The program relies on robotic observatories located on two continents – SuperWASP-North, located at the Roque de los Muchachos Observatory in Canary Island; and SuperWASP South, at the South African Astronomical Observatory, near Sutherland, South Africa.
From the SuperWASP survey data, Dr. Demangeon and her colleagues were able to detect three transit signals coming from three distant stars – WASP-151, WASP-153 and WASP-156. This was then followed by spectroscopic observations performed using the Haute-Provence Observatory in France and the La Silla Observatory in Chile, which allowed the team to confirm the nature of these planets.
From this, they determined that WASP-151b and WASP-153b are two “hot Saturns”, meaning they are low-density gas giants with close orbits. They orbit their respective suns, which are both early G-type stars (aka. yellow dwarfs, like our Sun), with an orbital period of 4.53 and 3.33 days. WASP-156b, meanwhile, is a Super-Neptune that orbits a K-type (orange dwarf) star. As they indicated in their study:
“WASP-151b and WASP-153b are relatively similar. Their masses of 0.31 and 0.39 M Jup and semi-major axes of 0.056 AU and 0.048 AU respectively indicate two Saturn-size objects around early G type stars of V magnitude ~ 12.8. WASP-156b’s radius of 0.51R Jup suggests a Super-Neptune and makes it the smallest planet ever detected by WASP. Its mass of 0.128 M Jup is also the 3rd lightest detected by WASP after WASP-139b and WASP-107b. Also interesting is the fact that WASP-156 is a bright (magV = 11.6) K type star.”
Taken together, these planets represent some major opportunities for exoplanet research. As they indicate, “these three planets also lie close to (WASP-151b and WASP-153b) or below (WASP-156b) the upper boundary of the Neptunian desert.” This refers to the boundary astronomers have observed around stars where shot period Neptune-size planets are very unlikely to be found.
Basically, of all the short period exoplanets (less than 10 days) to be discovered so far, the majority have tended to be in the “Super-Earth” or “Super-Jupiter” category. This deficit of Neptune-like planets has been attributed to different mechanisms when it comes to the formation and evolution for hot Jupiters and short-period super-Earths, as well as it being the result of gas envelop-depletion caused by a star’s ultraviolet radiation.
So far, only nine “Super-Neptunes” have been discovered; so this latest discovery (who’s characteristics are well know) should provide plenty of opportunities for research. Or as Dr. Demangeon and her colleagues explain in the study:
“WASP-156b, being one of the few well characterised Super-Neptunes, will help to constrain the formation of Neptune size planets and the transition between gas and ice giants. The estimates of the age of these three stars confirms the tendency for some stars to have gyrochronological ages significantly lower than their isochronal ages.”
The team also offered some possible explanations for the existence of a “Neptunian desert” based on their findings. For starters, they proposed that a high-eccentricity migration could be responsible, where Neptune-sized ice giants form in the outer reaches of a star system and migrate inward over time. They also indicate that their discovery offers compelling evidence that ultra-violet radiation and gas envelope-depletion could be a key part of the puzzle.
But of course, Dr. Demangeon and her colleagues indicate that further research will be necessary to confirm their hypothesis, and that further studies are needed to properly constrain the boundaries of the so-called “Neptunian desert”. They also indicate that future missions like NASA’s Transiting Exoplanet Survey Satellite and the ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission will be vital to these efforts.
“Obviously, a more thorough analysis is necessary to investigate all the possible implications behind this hypothesis,” they conclude. “Such an analysis is out of the scope of this paper but we think that this hypothesis is worth investigating. In this context, a search for long period companions that might have triggered the high eccentricity migration or an independent age estimate through asterosiesmology with TESS or Plato would be particularly interesting.”
The sheer number of exoplanets discoveries made in recent decades has allowed astronomers to test and revise commonly-held theories about how planetary systems form and evolve. These same discoveries have also helped advance our understanding of how our own Solar System came to be. In the end, being able to study a diverse array of planetary systems, which are different stages in their history, is allowing us to create a sort of timeline for cosmic evolution.
Further Reading: Astronomy and Astrophysics
The study of extra-solar planets has revealed discoveries that have confounded expectations and boggled the mind! Whether it’s Super-Earths that become diamond planets, multiple rocky planets orbiting closely together, or “Hot Jupiters” with traces of gaseous metal in their atmospheres, there’s been no shortage of planets out there for which there is no comparison here in the Solar System.
In this respect, WASP-12b is in good company. This Hot-Jupiter, located in a star system 1400 light years from Earth in the direction of the Auriga constellation, was recently studied by a team of astronomers using the Hubble Space Telescope. Due to the particular nature of its atmosphere, which absorbs the vast majority of light it receives instead of reflecting it, this planet appeared pitch black when observed by the Hubble team.
The study which details their findings, “The Very Low Albedo of WASP-12b from Spectral Eclipse Observations with Hubble“, was recently published in The Astrophysical Journal. Led by Taylor Bell, a researcher at the Institute for Research on Exoplanets (IREx) at McGill University, the team consulted data from the Hubble’s Space Telescope Imaging Spectrograph (STIS) to observe WASP-12b during an optical eclipse.
Like all Hot Jupiters, WASP-12b is similar in mass to Jupiter (1.35 to 1.43 Jupiter masses) and orbits very close to its star. At a distance of just 3.4 million km (2.115 million mi), or 0.0229 AU, it takes a little over a day to complete a single orbit. Because of its proximity, one side of the planet is constantly facing towards it’s sun – i.e. it is tidally locked with its star.
Because of its orbit, temperatures on the day side of the planet are estimated to reach as high as 2811 K (2538 °C; 4600 °F). It is because of these extreme temperatures that most molecules are unable to survive on the day side of the planet, so clouds cannot form to reflect light back into space. As a result, most incoming light penetrates deep into the planet’s atmosphere, where it is absorbed by hydrogen atoms and converted into heat energy.
This was what Bell and his team noticed as they observed the planet passing behind its star (aka. an optical eclipse). Using the STIS, they monitored the system for any dips in starlight, which would indicate how much reflected light was being given off by the planet. However, their observations did not detect reflected light, which indicated that the sun-facing side was absorbing most of the light it was receiving.
As Bell explained in a NASA press statement, this was quite the unusual find: “We did not expect to find such a dark exoplanet,” he said. “Most hot Jupiters reflect about 40 percent of starlight.” However, observations conducted of the night side of the planet show that things are quite different there. On this side, temperatures are about 1366 K (1093 °C; 2000 °F) cooler, which allows water vapor and clouds to form.
Back in 2013, scientists working with the HST detected traces of water vapor in the atmosphere (and possible traces of clouds as well) while studying the day/night boundary. As Bell indicated, this new research just goes to show just how diverse this type of gas giant can be:
“This new Hubble research further demonstrates the vast diversity among the strange population of hot Jupiters. You can have planets like WASP-12b that are 4,600 degrees Fahrenheit and some that are 2,200 degrees Fahrenheit, and they’re both called hot Jupiters. Past observations of hot Jupiters indicate that the temperature difference between the day and night sides of the planet increases with hotter day sides. This previous research suggests that more heat is being pumped into the day side of the planet, but the processes, such as winds, that carry the heat to the night side of the planet don’t keep up the pace.”
Since its discovery in 2008, several telescopes have studied WASP-12b, including Hubble, NASA’s Spitzer Space Telescope, and NASA’s Chandra X-ray Observatory. Previous observations by Hubble’s Cosmic Origins Spectrograph (COS) also revealed that the planet may be losing size and mass due to super-heated material from its atmosphere slowly being accreted onto the star.
This is just the latest find in a slew that has confounded scientists expectations about exoplanets. The more we come to learn about the nature and diversity of these distant worlds, the more tantalizing they seem and the more appealing the prospect of exploring them directly someday becomes!
The study of extra-solar planets has turned up some rather interesting candidates in the past few years. As of August 1st, 2017, a total of 3,639 exoplanets have been discovered in 2,729 planetary systems and 612 multiple planetary systems. Many of these discoveries have challenged conventional thinking about planets, especially where their sizes and distances from their suns are concerned.
According to a study by an international team of astronomers, the latest exoplanet discoveries are in keeping with this trend. Known as EPIC 211418729b and EPIC 211442297b, these two gas giants orbit stars that are located about 1569 and 1360 light-years from Earth (respectively) and are similar in size to Jupiter. Combined with their relatively close orbit to their stars, the team has designated them as “Warm Jupiters”.
The study, titled “EPIC 211418729b and EPIC 211442297b: Two Transiting Warm Jupiters“, recently appeared online. Led by Avi Shporer – a postdoctoral scholar with the Geological and Planetary Sciences (GPS) division at the California Institute of Technology (Caltech) – the team relied on data from the Kepler and K2 missions, and follow-up observations with multiple ground-based telescopes, to determine the sizes, masses and orbits of these planets.
As they indicate in their study, the two planets were initially identified as transiting planet candidates by the K2 mission. In other words, they were initially detected through the transit method, where astronomers measure dips in a star brightness to confirm that a planet is passing between the observer and the star. These observations took place during K2‘s Campaign 5 observations, which took place between April 27th and July 10th, 2015.
The team then conducted follow-up observations using the Keck II telescope (located at the W.M. Keck Observatory in Hawaii) and the Gemini North Telescope (at the Gemini Observatory, also in Hawaii). These observations, conducted from January 2016 to May 2017, were then combined with spectral data and radial velocity measurements from the High Resolution Echelle Spectrometer (HIRES) the on the Keck I telescope.
Finally, they added photometric data from the Cerro Tololo Inter-American Observatory (CTIO) in Chile, the South African Astronomical Observatory (SAAO), and the Siding Spring Observatory (SSO) in Australia. These follow-up observations confirmed the presence of these two exoplanets. As they wrote in the study:
“We have discovered two transiting warm Jupiter exoplanets initially identified as transiting candidates in K2 photometry… Both planets are among the longest period transiting gas giant planets with a measured mass, and they are orbiting relatively old host stars. Both planets are not inflated as their radii are consistent with theoretical expectations.”
From their observations, the team was also able to produce estimates on the planets respective sizes, masses and orbital periods. Whereas EPIC 211418729 b measures 0.942 Jupiter radii, has approximately 1.85 Jupiter masses and orbital period of 11.4 days, EPIC 211442297 b measures 1.115 Jupiter radii, has approximately 0.84 Jupiter masses and an orbital period of 20.3 days.
Based on their estimates, these planets experience surface temperatures of up to 719 K (445.85 °C; 834.5 °F) and 682 K (408.85°C; 768 °F), respectively. As such, they classified these planets as “Warm Jupiters”, since they fall short of what is considered typical for “Hot Jupiters” – which have exotic atmosphere’s that experience temperatures as high as several thousand kelvin.
The researchers noted that based on their orbital periods, these two planets have some of the longest orbital periods of any transiting gas giant (i.e. those that have been detected using the transit method) detected to date. Or as they state in their study:
“Both EPIC 211418729b and EPIC 211442297b are among the longest period transiting gas giant planets with a measured mass. In fact, according to the NASA Exoplanet Archive (Akeson et al. 2013) EPIC 211442297b is currently the longest period K2 transiting exoplanet with a well constrained mass.”
Another interesting observation was the fact that neither of these exoplanets were inflated, which is something they did not anticipate. In the case of Hot Jupiters, the atmospheres undergo expansion as a result of the amount of solar irradiation they receive, resulting in what the team refers to as a “radius-irradiation correlation” in their paper. In other words, Hot Jupiters are massive, but are also known to have low densities compared to cooler gas giants.
Instead, the team found that both EPIC 211418729b and EPIC 211442297b had radii that were consistent with what theoretical models predict for gas giants of their mass. Their results also led them to make some tentative conclusions about the planets’ structures and compositions. As they wrote:
“Both planets are not inflated compared to theoretical expectations, unlike many other planets in the diagram. Their positions are close to or consistent with theoretical expectations for a planet with little to no rocky core, for EPIC 211442297b, and a planet with a significant rocky core for EPIC 211418729b.”
These results suggest that solar irradiation does not play a significant role in determining the radius of Warm Jupiters. It also raises some interesting questions about the correlation between radii and irradiation with other gas giants. In the future, EPIC 211418729b and EPIC 211442297b will be targets of future K2 observations during the mission’s Campaign 18 – which will run from May to August 2018.
These observations are sure to offer some additional insight into these planets and the mysteries this study has raised. Future surveys of transiting exoplanets – conducting by next-generation instruments like the Transiting Exoplanet Survey Satellites (TESS) – and direct-imaging surveys conducted by the James Webb Space Telescope (JWST) are sure to reveal even more about distant, exotic exoplanets.
Further Reading: arXiv