Extrasolar Planets Archives

August 18, 2017August 18, 2017 by Matt Williams

Another Nearby Red Dwarf Star System, Another Possible Exoplanet Discovered!

Artist's impression of rocky exoplanets orbiting Gliese 832, a red dwarf star just 16 light-years from Earth. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org).

In the past few years, there has been no shortages of extra-solar planets discoveries which orbit red dwarf stars. In 2016 and 2017 alone, astronomers announced the discovery of a terrestrial (i.e. rocky) planet around Proxima Centauri (Proxima b), a seven-planet system orbiting TRAPPIST-1, and super-Earths orbiting the nearby stars of LHS 1140 (LHS 1140b), and GJ 625 (GJ 625b).

In what could be the latest discovery, physicists at the University of Texas Arlington (UTA) recently announced the possible discovery of an Earth-like planet orbiting Gliese 832, a red dwarf star just 16 light years away. In the past, astronomers detected two exoplanets orbiting Gliese 832. But after conducting a series of computations, the UTA team indicated that an additional Earth-like planet could be orbiting the star.

The study which details their findings, titled “Dynamics of a Probable Earth-mass Planet in the GJ 832 System“, recently appeared in The Astrophysical Journal. Led by Dr. Suman Satyal – a physics researcher, lecturer and laboratory supervisor at UTA – the team sought to investigate the stability of planetary orbits around Gliese 832 using a numerical and detailed phase-space analysis.

*Artistic representation of the potentially habitable exoplanet Gliese 832c as compared with Earth. Credit: PHL/UPR Arecibo.*

As indicated, two other exoplanets had been discovered around Gliese 832 in the past, including a Jupiter-like gas giant (Gliese 832b) in 2008, and the super-Earth (Gliese 832c) in 2014. In many ways, these planets could not be more different. In addition to their disparity in mass, they vary widely in terms of their orbits – with Gliese 832b orbiting at a distance of about 0.16 AU and Gliese 832c orbiting at a distance of 3 to 3.8 AU.

Because of this, the UTA team sought to determine if perhaps there was a third planet with a stable orbit between the two. To this end, they conducted numerical simulations for a three and four body system of planets with elliptical orbits around the star. These simulations took into account a large number of initial conditions, which allowed for all possible states (aka. s phase-space simulation) of the planet’s orbits to be represented.

They then included the radial velocity measurements of Gliese 832, accounting for them based on the presence of planets with 1 to 15 Earth masses. The Radial Velocity (RV) method, it should be noted, determines the existence of planets around a star based on variations in the star’s velocity. In other words, the fact that a star is moving back and forth indicates that it is being influenced by the presence of a planetary system.

Simulating the star’s RV signal using a hypothetical system of planets also allowed the UTA team to constrain the average distances at which these planets would orbit the star (aka. their semi-major axes) and their upper mass-limits. In the end, their results provided strong indications for the existence of a third planet. As Dr. Satyal explained in a UTA press release:

“We also used the integrated data from the time evolution of orbital parameters to generate the synthetic radial velocity curves of the known and the Earth-like planets in the system. We obtained several radial velocity curves for varying masses and distances indicating a possible new middle planet.”

*Diagram showing the possible orbit of a third exoplanet around Gliese 832, a star system located just 16 light years away. Credit: uta.edu/Suman Satyal*

Based on their computations, this possible planet of the Gliese 832 system would be between 1 and 15 Earth masses and would orbit the star at a distance ranging from 0.25 to 2.0 AU. They also determined that it would likely have a stable orbit for about 1 billion years. As Dr. Satyal indicated, all signs coming from the Gliese 832 system point towards there being a third planet.

“The existence of this possible planet is supported by long-term orbital stability of the system, orbital dynamics and the synthetic radial velocity signal analysis,” he said. “At the same time, a significantly large number of radial velocity observations, transit method studies, as well as direct imaging are still needed to confirm the presence of possible new planets in the Gliese 832 system.”

Alexander Weiss, the UTA Physics Chair, also lauded the achievement, saying:

“This is an important breakthrough demonstrating the possible existence of a potential new planet orbiting a star close to our own. The fact that Dr. Satyal was able to demonstrate that the planet could maintain a stable orbit in the habitable zone of a red dwarf for more than 1 billion years is extremely impressive and demonstrates the world class capabilities of our department’s astrophysics group.”

*Artist’s impression of a Super-Earth orbiting close to a red dwarf star. Credit: M. Weiss/CfA*

Another interesting tidbit is that this planet’s orbit would place it beyond or just within Gliese 832’s habitable zone. Whereas the Super-Earth Gliese 832c has an eccentric orbit that places it at the inner edge of this zone, this third planet would skirt its outer edge at the nearest. In this sense, Gliese 832’s two Super-Earths could very well be Venus-like and Mars-like in nature.

Looking ahead, Dr. Satyal and his colleagues will be naturally be looking to confirm the existence of this planet, and other institutions are sure to conduct similar studies. This star system is yet another that is sure to be the subject of follow-up studies in the coming years, most likely from next-generation space telescopes like the James Webb Space Telescope.

Further Reading: University of Texas Arlington, The Astrophysical Journal

August 15, 2017 by Matt Williams

Potentially Habitable, Tidally-Locked Exoplanets May be Very Common, say New Study

Artist's impression of a system of exoplanets orbiting a low mass, red dwarf star. Credit: NASA/JPL

Studies of low-mass, ultra-cool and ultra-dim red dwarf stars have turned up a wealth of extra-solar planets lately. These include the discoveries of a rocky planet orbiting the closest star to the Solar System (Proxima b) and a seven-planet system just 40 light years away (TRAPPIST-1). In the past few years, astronomers have also detected candidates orbiting the stars Gliese 581, Innes Star, Kepler 42, Gliese 832, Gliese 667, Gliese 3293, and others.

The majority of these planets have been terrestrial (i.e. rocky) in nature, and many were found to orbit within their star’s habitable zone (aka. “goldilocks zone”). However the question whether or not these planets are tidally-locked, where one face is constantly facing towards their star has been an ongoing one. And according to a new study from the University of Washington, tidally-locked planets may be more common than previously thought.

The study – which is available online under the title “Tidal Locking of Habitable Exoplanets” – was led by Rory Barnes, an assistant professor of astronomy and astrobiology at the University of Washington. Also a theorist with the Virtual Planetary Laboratory, his research is focused on the formation and evolution of planets that orbit in and around the “habitable zones” of low-mass stars.

*Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth (left side). Credit: Wikipedia*

For modern astronomers, tidal-locking is a well-understood phenomena. It occurs as a result of their being no net transfer of angular momentum between an astronomical body and the body it orbits. In other words, the orbiting body’s orbital period matches its rotational period, ensuring that the same side of this body is always facing towards the planet or star it orbits.

Consider Earth’s only satellite – the Moon. In addition to taking 27.32 days to orbit Earth, the Moon also takes 27.32 days to rotate once on its axis. This is why the Moon always presents the same “face” towards Earth, while the side that faces away is known as the “dark side”. Astronomers believe this became the case after a Mars-sized object (Theia) collided with Earth some 4.5 billion years ago.

Aside from throwing up debris that would eventually form the Moon, the impact is believed to have struck Earth at such an angle that it gave our planet an initial rotation period of 12 hours. In the past, researchers have used this 12-hour estimation of Earth’s rotation as a model for exoplanet behavior. However, prior to Barnes’ study, no systematic examinations had ever been conducted.

Looking to address this, Barnes chose to address the long-held assumption that only smaller, dimmer stars could host orbiting planets that were tidally locked. He also considered other possibilities, which included slower or faster initial rotation periods as well as variations in planet size and the eccentricity of their orbits. What he found was that previous studies had been rather limited and only made allowances for one outcome.

*Tidally-locked, rocky planets are common around low-mass, M-type (red dwarf) stars, due to their close orbits. Credit: M. Weiss/CfA*

As he explained in a University of Washington press statement:

“Planetary formation models, however, suggest the initial rotation of a planet could be much larger than several hours, perhaps even several weeks. And so when you explore that range, what you find is that there’s a possibility for a lot more exoplanets to be tidally locked. For example, if Earth formed with no Moon and with an initial ‘day’ that was four days long, one model predicts Earth would be tidally locked to the sun by now.”

From this, he found that potentially-habitable planets that orbit very late M-type (red dwarf) stars are likely to attain highly-circular orbits about 1 billion years after their formation. Furthermore, he found that for the majority, their orbits would be synchronized with their rotation – aka. they would be tidally-locked with their star. These findings could have significant implications for the study of exoplanets formation and evolution, not to mention habitability.

In the past, tidally-locked planets were thought to have extremes climates, thus eliminating any possibility of life. As an example, the planet Mercury experiences a 3:2 spin-orbit resonance, meaning it rotates three times on its axis for every two orbits it completes of the Sun. Because of this, a single day on Mercury lasts as long as 176 Earth days, and temperature range from 100 (-173 °C; -279 °F) to 700 K (427 °C; 800 °F) between the day side and the night side.

For a tidally-locked planets that orbit close to their stars, it was believed this situation would be even worse. However, astronomers have since come to speculate that the presence of an atmosphere around these planets could redistribute temperature across their surfaces. Unlike Mercury, which has no atmosphere and experiences no wind, these planets could maintain temperatures that would be supportive to life.

In any case, this study is one of many that is putting constraints on recent exoplanet discoveries. This is especially important given that the detection and study of extra-solar planets is still in its infancy, and limited to largely indirect methods. In other words, astronomers make estimates of a planet’s size, composition and whether or not it has an atmosphere based on transits and the influence these planets have on their stars.

In the coming years, next-generations missions like the James Web Space Telescope and the Transiting Exoplanet Survey Satellites (TESS) are expected to improve this situation drastically. In addition to conducting more detailed observations on existing discoveries, they are also expected to uncover a wealth of more planets. If Barnes’ study is correct, the majority of those found will be tidally-locked, but that need not mean they are uninhabitable.

Prof. Barnes paper was accepted for publication by the journal Celestial Mechanics and Dynamical Astronomy. The research was funded by a NASA grant through the Virtual Planetary Laboratory.

Further Reading: University of Washington, arXiv

August 9, 2017August 9, 2017 by Matt Williams

New Study Claims There are Four Exoplanets Around Nearest Sun-Like Star!

Artist's impression of a yellowish star being orbited by an extra-solar planet. Credit: ESO/L. Calçada

It has been an exciting time for the field of exoplanet studies lately! Last summer, researchers from the European Southern Observatory (ESO) announced the discovery of an Earth-like planet (Proxima b) located in the star system that is the nearest to our own. And just six months ago, an international team of astronomers announced the discovery of seven rocky planets orbiting the nearby star TRAPPIST-1.

But in what could be the most encouraging discovery for those hoping to find a habitable planet beyond Earth, an an international team of astronomers just announced the discovery of four exoplanet candidates in the tau Ceti system. Aside from being close to the Solar System – just 12 light-years away – this find is also encouraging because the planet candidates orbit a star very much like our own!

The study that details these findings – “Color difference makes a difference: four planet candidates around tau Ceti” – recently appeared online and has been accepted for publication in the Astrophysical Journal. Led by researchers from the Center for Astrophysics Research (CAR) at the University of Hertfordshire, the team analyzed tau Ceti using a noise-eliminating model to determine the presence of four Earth-like planets.

*This illustration compares the four planets detected around the nearby star tau Ceti (top) and the inner planets of our solar system (bottom). Credit: Fabo Feng/CAR/Univ. of Hertfordshire*

This discovery was made possible thanks to ongoing improvements in instrumentation, observation and data-sharing, which are allowing for surveys of ever-increasing sensitivity. As Steven Vogt, a professor of astronomy and astrophysics at UC Santa Cruz and a co-author on the paper, said in a UCSC press release:

“We are now finally crossing a threshold where, through very sophisticated modeling of large combined data sets from multiple independent observers, we can disentangle the noise due to stellar surface activity from the very tiny signals generated by the gravitational tugs from Earth-sized orbiting planets.”

This is the latest in a long-line of surveys of tau Ceti, which has been of interest to astronomers for decades. By 1988, several radial velocity measurements were conducted of the star system that ruled out the possibility of massive planets at Jupiter-like distances. In 2012, astronomers from UC Santa Barabara presented a study that indicated that tau Ceti might be orbited by five exoplanets, two of which were within the star’s habitable zone.

The team behind that study included several members who produced this latest study. At the time, lead author Mikko Tuomi (University of Hertfordshire, a co-author on the most recent one) was leading an effort to develop better data analysis techniques, and used this star as a benchmark case. As Tuomi explained, theses efforts allowed them to rule out two of the signals that has previously been identified as planets:

“We came up with an ingenious way of telling the difference between signals caused by planets and those caused by star’s activity. We realized that we could see how star’s activity differed at different wavelengths and use that information to separate this activity from signals of planets.”

*Artist’s impression of the Tau Ceti system, based on data retrieved in 2012. Credit: J. Pinfield/Univ. of Hertfordshire*

For the sake of this latest study – which was led by Fabo Feng, a member of the CAR – the team relied on data provided by the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at the ESO’s La Silla Observatory in Chile, and the High Resolution Echelle Spectrometer (HIRES) instrument at the W. M. Keck Observatory in Mauna Kea, Hawaii.

From this, they were able to create a model that removed “wavelength dependent noise” from radial velocity measurements. After applying this model to surveys made of tau Ceti, they were able to obtain measurements that were sensitive enough to detect variations in the star’s movement as small as 30 cm per second. In the end, they concluded that tau Ceti has a system of no more than four exoplanets.

As Tuomi indicated, after several surveys and attempts to eliminate extraneous noise, astronomers may finally have a clear picture of how many planets tau Ceti has, and of what type. “[N]o matter how we look at the star, there seem to be at least four rocky planets orbiting it,” he said. “We are slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system.”

They further estimate from their refined measurements that these planets have masses ranging from four Earth-masses (aka. “super-Earths”) to as low as 1.7 Earth masses, making them among the smallest planets ever detected around a nearby sun-like star. But most exciting of all is the fact that that two of these planets (tau Ceti e and f) are located within the star’s habitable zone.

*Recent studies have shown that rocky planets orbiting red dwarf stars will be tidally-locked and subject to intense radiation, reducing their chances of being habitable. Credit: M. Weiss/CfA*

The reason for this is because tau Ceti is a G-type (yellow dwarf) star, which makes it similar to our own Sun – about 0.78 times as massive and half as bright. In contrast, many recently discovered exoplanets – such as Proxima b and the seven planets of TRAPPIST-1 – all orbit M-type (red dwarf) stars. Compared to our Sun, these stars are variable and unstable, increasing their chances of stripping the atmospheres of their respective planets.

In addition, since red dwarfs are much dimmer than our Sun, a rocky planet would have to orbit very closely to them in order to be within their habitable zones. At this kind of distance, the planet would likely be tidally-locked, meaning that one side would constantly be facing towards the sun. This too makes the odds of life emerging on any such planet pretty slim.

Because of this, astronomers have been looking forward to finding more exoplanets around stars that are closer in size, mass and luminosity to our own. But before anyone gets too excited, its important to note these worlds are Super-Earths – with up to four times the mass of Earth. This means that (depending on their density as well) any life that might emerge on these planets would be subject to significantly increased gravity.

In addition, a massive debris disc surrounds the star, which means that these outermost planets are probably subjected to intensive bombardment by asteroids and comets. This not doesn’t exactly bode well for potential life on these planets! Still, this study is very encouraging, and for a number of reasons. Beyond finding strong evidence of exoplanets around a Sun-like star, the measurements that led to their detection are the most sensitive to date.

Artist’s impression of how an infant earth might look. Credit: ESO.

At the rate that their methods are improving, researchers should be getting to the 10-centimeter-per-second limit in no time at all. This is the level of sensitively required for detecting Earth analogs – aka. the brass ring for exoplanet-hunters. As Feng indicated:

“Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earth’s habitability through comparison with these analogs. We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals.”

Think of it! In no time at all, exoplanet-hunters could be finding a plethora of planets that are not only very close in size and mass to Earth, but also orbiting within their stars habitable zones. At that point, scientists are sure to dispense with decidedly vague terms like “potentially habitable” and “Earth-like” and begin using terms like “Earth-analog” confidently. No more ambiguity, just the firm conviction that Earth is not unique!

With an estimated 100 billion planets in our galaxy alone, we’re sure to find several Earths out here. One can only hope they have given rise to complex life like our own, and that they are in the mood to chat!

Further Reading: UCSC, arXiv

August 8, 2017 by Matt Williams

Standford Team Creates mDOT, a Mini-Starshade for Exoplanet Research

The new DARKNESS camera developed by an international team of researchers will allow astronomers to directly study nearby exoplanets. Credit: Stanford/SRL

NASA has turned a lot of heads in recent years thanks to its New Worlds Mission concept – aka. Starshade. Consisting of a giant flower-shaped occulter, this proposed spacecraft is intended to be deployed alongside a space telescope (most likely the James Webb Space Telescope). It will then block the glare of distant stars, creating an artificial eclipse to make it easier to detect and study planets orbiting them.

The only problem is, this concept is expected to cost a pretty penny – an estimated $750 million to $3 billion at this point! Hence why Stanford Professor Simone D’Amico (with the help of exoplanet expert Bruce Macintosh) is proposing a scaled down version of the concept to demonstrate its effectiveness. Known as mDot, this occulter will do the same job, but at a fraction of the cost.

The purpose behind an occulter is simple. When hunting for exoplanets, astronomers are forced to rely predominantly on indirected methods – the most common being the Transit Method. This involves monitoring stars for dips in luminosity, which are attributed to planets passing between them and the observer. By measuring the rate and the frequency of these dips, astronomers are able to determine the sizes of exoplanets and their orbital periods.

As Simone D’Amico, whose lab is working on this eclipsing system, explained in a Stanford University press statement:

“With indirect measurements, you can detect objects near a star and figure out their orbit period and distance from the star. This is all important information, but with direct observation you could characterize the chemical composition of the planet and potentially observe signs of biological activity – life.”

However, this method also suffers from a substantial rate of false positives and generally requires that part of the planet’s orbit intersect a line-of-sight between the host star and Earth. Studying the exoplanets themselves is also quite difficult, since the light coming from the star is likely to be several billion times brighter than the light being reflected off the planet.

The ability to study this reflected light is of particular interest, since it would yield valuable data about the exoplanets’ atmospheres. As such, several key technologies are being developed to block out the interfering light of stars. A spacecraft equipped with an occulter is one such technology. Paired with a space telescope, this spacecraft would create an artificial eclipse in front of the star so objects around it (i.e. exoplanets) can be clearly seen.

But in addition to the significant cost of building one, there is also the issue of size and deployment. For such a mission to work, the occulter itself would need to be about the size of a baseball diamond – 27.5 meters (90 feet) in diameter. It would also need to be separated from the telescope by a distance equal to multiple Earth diameters and would have to be deployed beyond Earth’s orbit. All of this adds up to a rather pricey mission!

Artist’s impression of the mDOT system. Much like the moon in a solar eclipse, one spacecraft would block the light from the star, allowing the other to observe objects near that star. Credit: Space Rendezvous Laboratory/Stanford University

As such, D’Amico – an assistant professor and the head of the Space Rendezvous Laboratory (SRL) at Stanford – and and Bruce Macintosh (a Stanford professor of physics) teamed up to create a smaller version called the Miniaturized Distributed Occulter/Telescope (mDOT). The primary purpose of mDOT is to provide a low-cost flight demonstration of the technology, in the hopes of increasing confidence in a full-scale mission.

As Adam Koenig, a graduate student with the SRL, explained:

“So far, there has been no mission flown with the degree of sophistication that would be required for one of these exoplanet imaging observatories. When you’re asking headquarters for a few billion dollars to do something like this, it would be ideal to be able to say that we’ve already flown all of this before. This one is just bigger.”

Consisting of two parts, the mDOT system takes advantage of recent developments in miniaturization and small satellite (smallsat) technology. The first is a 100-kg microsatellite that is equipped with a 3-meter diameter starshade. The second is a 10-kg nanosatellite that carries a telescope measuring 10 cm (3.937 in) in diameter. Both components will be deployed in high Earth orbit with a nominal separation of less than 1,000 kilometers (621 mi).

With the help of colleagues from the SRL, the shape of mDOT’s starshade was reformulated to fit the constraints of a much smaller spacecraft. As Koenig explained, this scaled down and specially-designed starshade will be able to do the same job as the large-scale, flower-shaped version – and on a budget!

Simone D’Amico’s Space Rendezvous Laboratory, pictured inside the room where they test space navigation in highly realistic illumination conditions. Credit: Space Rendezvous Laboratory/Stanford University

“With this special geometric shape, you can get the light diffracting around the starshade to cancel itself out,” he said. “Then, you get a very, very deep shadow right in the center. The shadow is deep enough that the light from the star won’t interfere with observations of a nearby planet.”

However, since the shadow created by mDOT’s starshade is only tens of centimeters in diameter, the nanosatellite will have do some careful maneuvering to stay within it. For this purpose, D’Amico and the SRL also designed an autonomous system for the nanosatellite, which would allow it to conduct formation maneuvers with the starshade, break formation when needed, and rendezvous with it again later.

An unfortunate limitation to the technology is the fact that it won’t be able to resolve Earth-like planets. Especially where M-type (red dwarf) stars are concerned, these planets are likely to orbit too close to their parent stars to be observed clearly. However, it will be able to resolve Jupiter-sized gas giants and help characterize exozodiacal dust concentrations around nearby stars – both of which are priorities for NASA.

In the meantime, D’Amico and his colleagues will be using the Testbed for Rendezvous and Optical Navigation (TRON) to test their mDOT concept. This facility was specially-built by D’Amico to replicate the types of complex and unique illumination conditions that are encountered by sensors in space. In the coming years, he and his team will be working to ensure that the system works before creating an eventual prototype.

*Artist’s concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL*

As D’Amico said of the work he and his colleagues at the SNL perform:

“I’m enthusiastic about my research program at Stanford because we’re tackling important challenges. I want to help answer fundamental questions and if you look in all current direction of space science and exploration – whether we’re trying to observe exoplanets, learn about the evolution of the universe, assemble structures in space or understand our planet – satellite formation-flying is the key enabler.”

Other projects that D’Amico and the SNL are currently engaged in include developing larger formations of tiny spacecraft (aka. “swarm satellites”). In the past, D’Amico has also collaborated with NASA on such projects as GRACE – a mission that mapped variations in Earth’s gravity field as part of the NASA Earth System Science Pathfinder (ESSP) program – and TanDEM-X, an SEA-sponsored mission which yielded 3D maps of Earth.

These and other projects which seek to leverage miniaturization for the sake of space exploration promise a new era of lower costs and greater accessibility. With applications ranging from swarms of tiny research and communications satellites to nanocraft capable of making the journey to Alpha Centauri at relativistic speeds (Breakthrough Starshot), the future of space looks pretty promising!

Be sure to check out this video of the TRON facility too, courtesy of Standford University:

Further Reading: Standford University

August 3, 2017August 3, 2017 by Matt Williams

Hubble Eyes Stratosphere Around a Very Hot, Watery Jupiter!

Artist's concept of the hot Jupiter WASP-121b, which presents the best evidence yet of a stratosphere on an exoplanet - generated using Engine House VFX. Credit: Bristol Science Centre/University of Exeter

Extra-solar planet discoveries have been exploding in recent years. In fact, as of Aug. 1st, 2017, astronomers have identified 3,639 exoplanets in 2,729 planetary systems and 612 multiple planetary systems. And while the majority of these have been discovered by Kepler – which has detected a total of 5,017 candidates and confirmed the existence of 2,494 exoplanets since 2009 – other instruments have played an important role in these discoveries as well.

This includes the Hubble Space Telescope, which in recent years has been dedicated to the detection of atmospheres around distant planets. Most recently, it was used in a survey that produced the strongest evidence to date for the existence of a stratosphere – a layer of atmosphere in which temperature increases with altitude – around a gas giant located about 900 light-years from our Solar System.

The study, titled “An ultrahot gas-giant exoplanet with a stratosphere“, recently appeared in the journal Nature. Led by Thomas Evans, a Research Fellow from the Astrophysics Group at the University of Exeter, the team relied on data provided by NASA’s Hubble Space Telescope to study a planet known as WASP-121b, a gas giant that orbits a yellow-white star that is slightly larger than our own.

*The top of the planet’s atmosphere is heated to a blazing 2,500 °C (4,600 °F), hot enough to boil some metals. Credit: NASA/ESA/G. Bacon (STSci)*

The planet itself has roughly 1.2 times the mass of Jupiter, has a radius that is about 1.9 times that of Jupiter, and has an orbital period of just 1.3 days. This is due to its close proximity to its sun, which makes it a particularly “Hot Jupiter”. In fact, if this exoplanet were any closer to its star, it is estimated that WASP-121’s gravity would begin to tear it apart.

It is also this close proximity that super-heats the planet’s atmosphere, driving temperatures up to 2,500 °C (4,600 °F). As Mark Marley, a researcher with NASA’s Ames Research Center and a co-author on the study, indicated in a NASA press statement:

“This result is exciting because it shows that a common trait of most of the atmospheres in our solar system — a warm stratosphere — also can be found in exoplanet atmospheres. We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system.”

Whereas Hubble has found possible signs of stratospheres around WASP-33b and other hot Jupiters in the past, this new study presents the strongest evidence to date for the existence of an exoplanet stratosphere. The reason for this has to do with the spectrographic data obtained by Hubble of WASP-121b’s atmosphere, which indicated the presence of water vapor – which is a first as far as hot-Jupiter’s are concerned.

As Tom Evans – also a Research Fellow at the University of Exeter and the lead author on the paper – explained, these findings confirmed something that astronomers have suspected for some time. “Theoretical models have suggested stratospheres may define a distinct class of ultra-hot planets, with important implications for their atmospheric physics and chemistry,” he said. “Our observations support this picture.”

To study WASP-121b’s stratosphere, the team relied on spectroscopic data gathered by Hubble’s Wide Field Camera 3. After analyzing the different wavelengths that were part of WASP-121b’s light cure, they noted that certain wavelengths were glowing rather brightly in the infrared band. This, they concluded, was due to the presence of water vapor at the top of the planet’s atmosphere.

“The emission of light from water means the temperature is increasing with height,” Tiffany Kataria, one of the co-authors on the study from NASA’s Jet Propulsion Laboratory, said. “We’re excited to explore at what longitudes this behavior persists with upcoming Hubble observations.”

Beyond being the most convincing case so far of an exoplanet having a stratosphere, WASP-121b is also interesting because of just how hot this hot Jupiter is. Based on their data, the team concluded that temperatures in the atmosphere increased with altitude – a defining characteristic of a stratosphere. In Earth’s stratosphere, this process is driven by ozone, which traps the Sun’s ultraviolet light and raises the temperature of the surrounding molecules.

*Artist’s concept of “hot Jupiter” exoplanet, a gas giant that orbits very close to its star. Credit: NASA/JPL-Caltech)*

However, the temperature of Earth’s stratosphere does not exceed 270 K (-3°C; 26.6°F). When one considers other Solar Planets that also have stratosphere’s – like Saturn’s moon Titan, which experiences heating due to the interaction of solar radiation, energetic particles and methane – temperatures don’t change by more than 56 °C (100 °F). But in the case of WASP-121b, temperatures in the stratosphere increase by about 560 °C (1,000 °F).

Not even Venus, the hottest planet in the Solar System, can compete with that! On Earth’s “Sister Planet”, temperatures remain steady at about 735 K (462 °C; 863 °F), which is hot enough to melt lead. But on WASP-121b, temperatures reach over four times as high! This means the planet’s atmosphere is hot enough to melt stainless steel and other metals – like beryllium, platinum and zirconium.

At present, scientists do not now what chemicals are driving this temperature increase. Some possibilities have been suggested though, such as vanadium oxide and titanium oxide. Not only are these compounds believed to be common to brown dwarfs (aka. “failed stars”, which have much in common with gas giants), they also require the hottest temperatures possible in order to keep them in a gaseous state.

In any case, this distant gas giant has proven to be an interesting case study. In the future, research into this and other “super-hot Jupiters” is likely to challenge and expand our current understanding of how atmospheric forms and behave over time.

Further Reading: NASA, Nature

August 2, 2017August 2, 2017 by Matt Williams

Kepler Spots the First Exomoon Candidate 4000 Light Years From Earth

Artist's impression of the view from a hypothetical moon around a exoplanet orbiting a triple star system. Credit: NASA

Ever since it was deployed in March of 2009, the Kepler mission has detected thousands of extra-solar planet candidates. In fact, between 2009 and 2012, it detected a total of 4,496 candidates, and confirmed the existence of 2,337 exoplanets. Even after two of its reaction wheels failed, the spacecraft still managed to turn up distant planets as part of its K2 mission, accounting for another 521 candidates and confirming 157.

However, according to a new study conducted by a pair of researches from Columbia University and a citizen scientist, Kepler may also have also found evidence of an extra-solar moon. After sifting through data from hundreds of transits detected by the Kepler mission, the researchers found one instance where a transiting planet showed signs of having a satellite.

Their study – which recently published online under the title “HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I” – was by led Alex Teachey, a graduate student at Columbia University and a Graduate Research Fellow with the National Science Foundation (NSF). He was joined by David Kipping, an Assistant Professor of Astronomy at Columbia University and the Principal Investigator of The Hunt for Exomoons with Kepler (HEK) project, and Allan Schmitt, a citizen scientist.

*Artist’s impression of NASA’s Kepler spacecraft. Credit: NASA*

For years, Dr. Kipping has been searching the Kepler database for evidence of exomoons, as part of the HEK. This is not surprising, considering the kinds of opportunities that exomoons present for scientific research. Within our Solar System, the study of natural satellites has revealed important things about the mechanisms that drive early and late planet formation, and moons possess interesting geological features that are commonly found on other bodies.

It is for this reason that extending that research to the hunt for exoplanets is seen as necessary. Already, exoplanet-hunting missions like Kepler have turned up a wealth of planets that challenge conventional ideas about how planet formation and what kinds of planets are possible. The most noteworthy example are gas giants that have observed orbiting very close to their stars (aka. “Hot Jupiters”).

As such, the study of exomoons could yield valuable information about what kinds of satellites are possible, and whether or not our own moons are typical. As Teachey told Universe Today via email:

“Exomoons could tell us a lot about the formation of our Solar System, and other star systems. We see moons in our Solar System, but are they common elsewhere? We tend to think so, but we can’t know for sure until we actually see them. But it’s an important question because, if we find out there aren’t very many moons out there, it suggests maybe something unusual was going on in our Solar System in the early days, and that could have major implications for how life arose on the Earth. In other words, is the history of our Solar System common across the galaxy, or do we have a very unusual origin story? And what does that say about the chances of life arising here? Exomoons stand to offer us clues to answering these questions.”

*A montage of some of the potentially-habitable moons in our Solar System. From top to bottom, left to right, these include Europa, Enceladus, TItan and Ceres. Credit: NASA/JPL*

What’s more, many moons in the Solar System – including Europa, Ganymede, Enceladus and Titan – are thought to be potentially habitable. This is due to the fact that these bodies have steady supplies of volatiles (such as nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide) and possess internal heating mechanisms that could provide the necessary energy to power biological processes.

Here too, the study of exomoons presents interesting possibilities, such as whether or not they may be habitable or even Earth-like. For these and other reasons, astronomers want to see if the planets that have been confirmed in distant star systems have systems of moons and what conditions are like on them. But as Teachey indicated, the search for exomoons presents a number of challenges compared to exoplanet-hunting:

“Moons are difficult to find because 1) we expect them to be quite small most of the time, meaning the transit signal will be quite weak to begin with, and 2) every time a planet transits, the moon will show up in a different place. This makes them more difficult to detect in the data, and modeling the transit events is significantly more computationally expensive. But our work leverages the moons showing up in different places by taking the time-averaged signal across many different transit events, and even across many different exoplanetary systems. If the moons are there, they will in effect carve out a signal on either side of the planetary transit over time. Then it’s a matter of modeling this signal and understanding what it means in terms of moon size and occurrence rate.”

To locate signs of exomoons, Teachey and his colleagues searched through the Kepler database and analyzed the transits of 284 exoplanet candidates in front of their respective stars. These planets ranged in size from being Earth-like to Jupiter-like in diameter, and orbited their stars at a distance of between ~0.1 to 1.0 AU. They then modeled the light curve of the stars using the techniques of phase-folding and stacking.

*An artist’s conception of a habitable exomoon. Credit: NASA*

These techniques are commonly used by astronomers who monitor stars for dips in luminosity that are caused by the transits of planets (i.e. the transit method). As Teachey explained, the process is quite similar:

“Basically we cut up the time-series data into equal pieces, each piece having one transit of the planet in the middle. And when we stack these pieces together we’re able to get a clearer picture of what the transit looks like… For the moon search we do essentially the same thing, only now we’re looking at the data outside the main planetary transit. Once we stack the data, we take the average values of all the data points within a certain time window and, if a moon is present, we ought to see some missing starlight there, which allows us to deduce its presence.”

What they found was a single candidate located in the Kepler-1625 system, a yellow star located about 4000 light years from Earth. Designated Kepler-1625B I, this moon orbits the large gas giant that is located within the star’s habitable zone, is 5.9 to 11.67 times the size of Earth, and orbits its star with a period of 287.4 days. This exomoon candidate, if it should be confirmed, will be the first exomoon ever discovered

The team’s results (which await peer review) also demonstrated that large moons to be a rare occurrence in the inner regions of star systems (within 1 AU). This was something of a surprise, though Teachey acknowledges that it is consistent with recent theoretical work. According to what some recent studies suggest, large planets like Jupiter could lose their moons as they migrate inward.

If this should prove to be the case, then what Teachey and his colleagues witnessed could be seen as evidence of that process. It could also be an indication our current exoplanet-hunting missions may not be up to the task of detecting exomoons. In the coming years, next-generations missions are expected to provide more detailed analyses of distant stars and their planetary systems.

*An artist’s conception of a distance exomoon blocking out a star’s light. Credit: Dan*

However, as Teachey indicated, these too could be limited in terms of what they can detect, and new strategies may ultimately be needed:

“The rarity of moons in the inner regions of these star systems suggests that individual moons will remain difficult to find in the Kepler data, and upcoming missions like TESS, which should find lots of very short period planets, will also have a difficult time finding these moons. It’s likely the moons, which we still expect to be out there somewhere, reside in the outer regions of these star systems, much as they do in our Solar System. But these regions are much more difficult to probe, so we will have to get even more clever about how we look for these worlds with present and near-future datasets.”

In the meantime, we can certainly be exited about the fact that the first exomoon appears to have been discovered. While these results await peer review, confirmation of this moon will mean additional research opportunities for Kepler-1625 system. The fact that this moon orbits within the star’s habitable zone is also an interesting feature, though its not likely the moon itself is habitable.

Still, the possibility of a habitable moon orbiting a gas giant is certainly interesting. Does that sound like something that might have come up in some science fiction movies?

Further Reading: arXiv

July 20, 2017April 14, 2020 by Matt Williams

Advanced Civilizations Could Build a Galactic Internet with Planetary Transits

In a series of papers, Professor Loeb and Michael Hippke indicate that conventional rockets would have a hard time escaping from certain kinds of extra-solar planets. Credit: NASA/Tim Pyle

Decades after Enrico Fermi’s uttered his famous words – “Where is everybody?” – the Paradox that bears his name still haunts us. Despite repeated attempts to locate radio signals coming from space and our ongoing efforts to find visible indications of alien civilizations in distant star systems, the search extra-terrestrial intelligence (SETI) has yet to produce anything substantive.

June 20, 2017 by Matt Williams

NASA Announces 10, That’s Right 10! New Planets in Their Star’s Habitable Zone

The Kepler space telescope is surely the gift that keeps on giving. After being deployed in 2009, it went on to detect a total of 2,335 confirmed exoplanets and 582 multi-planet systems. Even after two of its reaction wheels failed, it carried on with its K2 mission, which has discovered an additional 520 candidates, 148 of which have been confirmed. And with yet another extension, which will last beyond 2018, it shows no signs of stopping!

In the most recent catalog to be released by the Kepler mission, an additional 219 new planet candidates have been added to its database. More significantly, 10 of these planets were found to be terrestrial (i.e. rocky), of comparable in size to Earth and orbited within their star’s habitable zone – the distance where surface temperatures would be warm enough to support liquid water.

These findings were presented at a news conference on Monday, June 19th, at NASA’s Ames Research Center. Of all the catalogs of Kepler candidates that have been released to date, this one is the most comprehensive and detailed. The eighth in a series of Kepler exoplanet catalogs, this one is based on data that was obtained from the first four years of the mission and is the final catalog that covers the spacecraft’s observations of the Cygnus constellation.

Since 2014, Kepler has ceased looking at a set starfield in the Cygnus constellation and has been collecting data on its second mission – observing fields on the plane of the ecliptic of the Milky Way Galaxy. With the release of this catalog, there are now 4,034 planet candidates that have been identified by Kepler – of which 2,335 have been verified.

An important aspect of this catalog were the methods that were used for producing it, which were the most sophisticated to date. As with all planets detected by Kepler, the latest finds were all made using the transit method. This consists of monitoring stars for occasional dips in brightness, which is used to confirm the presence of planets transiting between the star and the observer.

To ensure that the detections in this latest catalog were real, the team relied on two approaches to eliminate false positives. This consisted of introducing simulated transits into the dataset to make sure the dips that Kepler detected were consistent with planets. Then, they added false signals to see how often the analysis mistook these for planet transits. From this, they were able to tell which planets were overcounted and which were undercounted.

This led to another exciting find, which was the indication that for all of the smaller exoplanets discovered by Kepler, most fell within one of two distinct groupings. Essentially, half the planets that we know of in the galaxy are either rocky in nature and larger than Earth (i.e. Super-Earth’s), or are gas giants that are comparable in size to Neptune (i.e. smaller gas giants).

This conclusion was reached by a team of researchers who used the W.M. Keck Observatory to measure the sizes of 1,300 stars in the Kepler field of view. From this, they were able to determine the radii of 2,000 Kepler planets with extreme precision, and found that there was a clear division between rocky, Earth-sized planets and gaseous planets smaller than Neptune – with few in between.

As Benjamin Fulton, a doctoral candidate at the University of Hawaii in Manoa and the lead author of this study, explained:

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals. Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

These results are sure to have drastic implications when it comes to knowing the frequency of different types of planets in our galaxy, as well as the study of planet formation. For instance, they noted that most rocky planets discovered by Kepler are up to 75% larger than Earth. And for reasons that are not yet clear, about half of them take on hydrogen and helium, which swells their size to the point that they become almost Neptune-sized.

*Histogram shows the number of planets per 100 stars as a function of planet size relative to Earth. Credits: NASA/Ames Research Center/CalTech/University of Hawaii/B.J. Fulton*

These findings could similarly have significant implications in the search for habitable planets and extra-terrestrial life. As Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate, said during the presentation:

“The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs – planets with roughly the same size and orbit as Earth. Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”

From this information, scientists will be able to know with a greater degree of certainty just how many “Earth-like” planets exist within our galaxy. The most recent estimates place the number of planets in the Milky Way at about 100 billion. And based on this data, it would seem that many of these are similar in composition to Earth, albeit larger.

Combined with a statistical models of how many of these can be found within a circumstellar habitable zone, we should have a better idea of just how many potentially-life-bearing worlds are out there. If nothing else, this should simplify some of the math in the Drake Equation!

In the meantime, the Kepler space telescope will continue to make observations of nearby star systems in order to learn more about their exoplanets. This includes the TRAPPIST-1 system and its seven Earth-sized, rocky planets. Its a safe bet that before it is finally retired after 2018, it will have some more surprises in store for us!

Further Reading: NASA, NASA Kepler and K2

June 7, 2017June 7, 2017 by Matt Williams

Even Calm Red Dwarf Stars Blast Their Planets with Mini-Flares, Destroying their Habitability

Artist's impression of a flaring red dwarf star, orbited by an exoplanet. Credit: NASA, ESA, and G. Bacon (STScI)

Thanks to some rather profound discoveries, red dwarf stars (aka. M-type stars) have been a popular target for exoplanet hunters lately. While small, cool, and relatively dim compared to our Sun, red dwarf star systems are where many of the most recent and promising exoplanet finds have been made. These include Proxima b, the seven rocky planets orbiting TRAPPIST-1, and the super-Earth discovered around LHS 1140b.

Unfortunately, red dwarf stars pose a bit of a problem when it comes to habitability. In addition to being variable in terms of the light they put out, they also known for being unstable. According to a new study by a team of scientists – which was presented the this week at the annual meeting of the American Astronomical Society – red dwarfs also experience mini-flares that could have a cumulative effect, thus rendering their orbiting planets uninhabitable.

For the sake of their study, titled “gPhoton: The GALEX Photon Data Archive“, the team relied on the ten years of ultraviolet observations made by the Galaxy Evolution Explorer (GALEX) spacecraft. During its mission, which ran from 2003 to 2013, GALEX monitored stars to detect rapid increases in brightness – i.e. signs of solar flare activity. These flares emit radiation across many wavelengths, but a significant amount is released in the UV band.

*Artist’s impression of the GALEX mission, which monitors ultraviolet throughout the Universe. Credit: NASA/JPL-Caltech*

Though not originally intended for exoplanet hunting, GALEX’s data proved very useful since red dwarfs are usually relatively dim in the ultraviolet band (a trait which makes flares particularly noticeable). Using this data, the team was able to measure events that were less intense than many previously detected flares. This was important, since red dwarf flares are known to be greater in frequency, but weaker in intensity.

It was also important from a habitability standpoint, since it is possible that frequent flaring could add up over time to create an inhospitable environment on orbiting planets. If planets like Proxima b are subject to radiation from smaller (but more frequent) flares, could there be a cumulative effect that could ultimately prevent life from emerging over time?

Such is the question that the team sought to address. To do this, they sorted through the ten years of GALEX data, which is held at the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute (STScI). Led by Chase Million of Million Concepts at State College in Pennsylvania, their efforts led to the creation of gPhoton – a 130 terabyte database with millisecond-timing resolution.

This database was then examined with custom software developed by Million and Clara Brasseur of the STScI, which enabled them to analyze the UV data at the photon level. As Million indicated, the results were quite interesting. “We have found dwarf star flares in the whole range that we expected GALEX to be sensitive to,” he said, “from itty bitty baby flares that last a few seconds, to monster flares that make a star hundreds of times brighter for a few minutes.”

While many of the flares that GALEX noticed were similar in strength to those generated by our Sun, the dynamics of red dwarf star systems are quite different. Since they are cooler and less bright, rocky planets need to orbit closer to red dwarfs in order to be warm enough to maintain liquid water on their surfaces (i.e. be habitable). This proximity means that they would be subject to more of the energy produced by these flares.

Such flares would be capable of stripping away a planet’s atmosphere, and could also prevent life from arising on the surface. And over time, smaller flares could poison an environment, making it impossible for organic life to thrive. At present, team members Brasseur and Rachel Osten (also from the STScI) are examining other stars observed by GALEX and also Kepler to look for similar flares.

The team expects to find examples of hundreds of thousands of these flares, which could help shed additional light on just what effect they could have on planetary habitability in red dwarf star systems. But for the time being, the case for red dwarf habitability appears to have been weakened. And once again, it has to do with the instability and radiation produced by these cool customers.

In the future, next-generation missions like the James Webb Space Telescope (which is scheduled to launch in 2018) are expected to reveal vital information on the atmospheres of nearby exoplanets. Most of these reside in red dwarf star systems, where questions about their composition and ability to support life are waiting to be resolved. In addition, the mission can also expected to shed light on these planet’s ability to retain atmospheres.

*Artist’s impression of the view from the most distant exoplanet discovered around the red dwarf star TRAPPIST-1. Credit: ESO/M. Kornmesser.*

On the plus side, this study has shown that archival data from missions that are no longer in operation can still be incredibly useful. As Don Neill, a research scientist at Caltech and a member of the GALEX collaboration, explained:

“These results show the value of a survey mission like GALEX, which was instigated to study the evolution of galaxies across cosmic time and is now having an impact on the study of nearby habitable planets. We did not anticipate that GALEX would be used for exoplanets when the mission was designed.”

These results were presented in a press conference at the American Astronomical Society, which will be taking place from June 4th to June 8th in Austin, Texas.

Further Reading: HubbleSite, The Astrophysical Journal

May 30, 2017May 31, 2017 by Matt Williams

Super-Earth Planet Found in the Habitable Zone of a Nearby Star

Artistic design of the super-Earth GJ 625 b and its star, GJ625 (Gliese 625). Credit: Gabriel Pérez/SMM (IAC)

M-type stars, also known as “red dwarfs”, have become a popular target for exoplanet hunters of late. This is understandable given the sheer number of terrestrial (i.e. rocky) planets that have been discovered orbiting around red dwarf stars in recent years. These discoveries include the closest exoplanet to our Solar System (Proxima b) and the seven planets discovered around TRAPPIST-1, three of which orbit within the star’s habitable zone.

The latest find comes from a team of international astronomers who discovered a planet around GJ 625, a red dwarf star located just 21 light years away from Earth. This terrestrial planet is roughly 2.82 times the mass of Earth (aka. a “super-Earth”) and orbits within the star’s habitable zone. Once again, news of this discovery is prompting questions about whether or not this world could indeed be habitable (and also inhabited).

The international team was led by Alejandro Mascareño of the Canary Islands Institute of Astrophysics (IAC), and includes members from the University of La Laguna and the University of Geneva. Their research was also supported by the Spanish National Research Council (CSIS), the Institute of Space Studies of Catalonia (IEEC), and the National Institute For Astrophysics (INAF).

*Diagram showing GJ 625’s habitable zone in comparison’s to the Sun’s. Credit: IAC*

The study which details their findings was recently accepted for publication by the journal Astronomy & Astrophysics, and appears online under the title “A super-Earth on the Inner Edge of the Habitable Zone of the Nearby M-dwarf GJ 625“. According to the study, the team used radial-velocity measurements of GJ 625 in order to determine the presence of a planet that has between two and three times the mass of Earth.

This discovery was part of the HArps-n red Dwarf Exoplanet Survey (HADES), which studies red dwarf stars to determine the presence of potentially habitable planets orbiting them. This survey relies on the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) instrument – which is part of the 3.6-meter Galileo National Telescope (TNG) at the IAC’s Roque de Los Muchachos Observatory on the island of La Palma.

Using this instrument, the team collected high-resolution spectroscopic data of the GJ 625 system over the course of three years. Specifically, they measured small variations in the stars radial velocity, which are attributed to the gravitational pull of a planet. From a total of 151 spectra obtained, they were able to determine that the planet (GJ 625 b) was likely terrestrial and had a minimum mass of 2.82 ± 0.51 Earth masses.

Moreover, they obtained distance estimates that placed it roughly 0.078 AU from its star, and an orbital period estimate of 14.628 ± 0.013 days. At this distance, the planet’s orbit places it just within GJ 625’s habitable zone. Of course, this does not mean conclusively that the planet has conditions conducive to life on its surface, but it is an encouraging indication.

*Tjhe Observatorio del Roque de los Muchachos, located on the island of La Palma. Credit: IAC*

As Alejandro Suárez Mascareño explained in an IAC press release:

“As GJ 625 is a relatively cool star the planet is situated at the edge of its habitability zone, in which liquid water can exist on its surface. In fact, depending on the cloud cover of its atmosphere and on its rotation, it could potentially be habitable”.

This is not the first time that the HADES project detected an exoplanet around a red dwarf star. In fact, back in 2016, a team of international researchers used this project to discover 2 super-Earths orbiting GJ 3998, a red dwarf located about 58 ± 2.28 light years from Earth. Beyond HADES, this discovery is yet another in a long line of rocky exoplanets that have been discovered in the habitable zone of a nearby red dwarf star.

Such findings are very encouraging since red dwarfs are the most common type of star in the known Universe- accounting for an estimated 70% of stars in our galaxy alone. Combined with the fact that they can exist for up to 10 trillion years, red dwarf systems are considered a prime candidate in the search for habitable exoplanets.

But as with all other planets discovered around red dwarf stars, there are unresolved questions about how the star’s variability and stability could affect the planet. For starters, red dwarf stars are known to vary in brightness and periodically release gigantic flares. In addition, any planet close enough to be within the star’s habitable zone would likely be tidally-locked with it, meaning that one side would be exposed to a considerable amount of radiation.

As such, additional observations will need to be made of this exoplanet candidate using the time-tested transit method. According to Jonay Hernández – a professor from the University of La Laguna, a researcher with the IAC and one of the co-authors on the study – future studies using this method will not only be able to confirm the planet’s existence and characterize it, but also determine if there are any other planets in the system.

“In the future, new observing campaigns of photometric observations will be essential to try to detect the transit of this planet across its star, given its proximity to the Sun,” he said. “There is a possibility that there are more rocky planets around GJ 625 in orbits which are nearer to, or further away from the star, and within the habitability zone, which we will keep on combing”.

According to Rafael Rebolo – one of the study’s co-authors from the Univeristy of La Laguna, a research with the IAC, and a member of the CSIS – future surveys using the transit method will also allow astronomers to determine with a fair degree of certainty whether or not GJ 625 b has the all-important ingredient for habitability – i.e. an atmosphere:

“The detection of a transit will allow us to determine its radius and its density, and will allow us to characterize its atmosphere by the transmitted light observe using high resolution high stability spectrographs on the GTC or on telescopes of the next generation in the northern hemisphere, such as the Thirty Meter Telescope (TMT)”.

But what is perhaps most exciting about this latest find is how it adds to the population of extra-solar planets within our cosmic neighborhood. Given their proximity, each of these planets represent a major opportunity for research. And as Dr. Mascareño told Universe Today via email:

“While we have already found more than 3600 extra-solar planets, the exoplanet population in our near neighborhood is still somewhat unknown. At 21 ly from the Sun, GJ 625 is one of the 100 nearest stars, and right now GJ 625 b is one of the 30 nearest exoplanets detected and the 6th nearest potentially habitable exoplanet.”

Once again, ongoing surveys of nearby star systems is providing plenty of potential targets in the search for life beyond our Solar System. And with both ground-based and space-based next-generation telescopes joining the search, we can expect to find many, many more candidates in the coming years. In the meantime, be sure to check out this animation of GJ 625 b and its parent star:

Further Reading: arXiv, IAC