Exoplanets – planets outside our Solar System – continue to provide astronomers with fascinating glimpses of other worlds, including the one designated WASP-76b. On this inferno-like planet, almost the size of Jupiter, the daytime surface temperatures are hot enough to vaporize iron, which could fall as rain on the slightly cooler night side.
Now researchers have given WASP-76b another look and concluded that it might actually be hotter than previously thought. Key to that conclusion is the discovery of ionized calcium, which would need “significantly hotter” conditions to form than have previously been outlined in studies.
As we know from previous research, temperatures on the surface of WASP-76b are thought to climb to around 4,400 degrees Fahrenheit (2,246 Celsius) on the daytime side – but that might be something of an underestimation if the new and updated temperature profile turns out to be more accurate.
“We’re seeing so much calcium; it’s a really strong feature,” says astrophysicist Emily Deibert from the University of Toronto in Canada. “This spectral signature of ionized calcium could indicate that the exoplanet has very strong upper atmosphere winds, or the atmospheric temperature on the exoplanet is much higher than we thought.”
Discovered in 2016, WASP-76b is known as a ‘hot Jupiter’ exoplanet because it’s so close to its star – an orbit takes just 1.8 Earth days. It’s around 640 light-years away from our position in the Universe. It’s also tidally locked, meaning the same side of the planet always faces its star, itself slightly hotter than our Sun.
Here the researchers used data from the Gemini North Telescope in Hawaii to look at the moderate temperature zone of the planet, the border between day and night. They used a process of transit spectroscopy, where the light of an exoplanet’s star shines through its atmosphere, all the way back to Earth.
The quality and composition of that light enable us to make calculations about the atmosphere at a variety of different depths. In this case, the team was able to identify a rare trio of spectral lines, readings that indicate the presence of ionized calcium.
“It’s remarkable that with today’s telescopes and instruments, we can already learn so much about the atmospheres – their constituents, physical properties, presence of clouds and even large-scale wind patterns – of planets that are orbiting stars hundreds of light-years away,” says astronomer Ray Jayawardhana from Cornell University in New York.
Spectroscopy techniques such as the one used here enable astronomers to discover all kinds of secrets about exoplanets hundreds of light-years (or more) away: everything from the details of the planet’s rotation to the wind patterns on the surface.
That means that as more and more of these exoplanets are discovered and cataloged, researchers can group them for easier reference. Ultimately we end up learning more about our place in the Universe and where we might find other forms of life.
This study is part of a multi-year project looking at a minimum of 30 exoplanets, called Exoplanets with Gemini Spectroscopy (ExoGemS). Once the project is completed, experts should have a much better idea of the diversity of atmospheres that exist on these distant and exotic worlds.
“As we do remote sensing of dozens of exoplanets, spanning a range of masses and temperatures, we will develop a more complete picture of the true diversity of alien worlds – from those hot enough to harbor iron rain to others with more moderate climates, from those heftier than Jupiter to others not much bigger than the Earth,” says Jayawardhana.
The research has been published in the Astrophysical Journal Letters.
Our Solar System, with just one star in the sky, may be a bit of an oddball. Most of the stars in the Milky Way galaxy actually have at least one gravitationally bound stellar companion, meaning that two-starred worlds like Tatooine are probably not uncommon.
Star systems, however, are confined to a maximum of two stars. We’ve found systems of up to seven stars bound together in a complex orbital dance. And now, scientists have found what they believe may be a first for astronomy: an exoplanet orbiting a system of three stars, also known as a stellar trinary.
To be clear, exoplanets have been found in trinary systems before – orbiting just one of the stars in the system. If this new discovery is validated, though, the exoplanet will be in orbit around all three of the stars, which isn’t something that’s been seen previously.
Observations of GW Orionis. (ALMA (ESO/NAOJ/NRAO), ESO/Exeter/Kraus et al.)
Stars in the Milky Way are not usually born in isolation. Their birthplaces are massive molecular clouds, where dense clumps of gas collapse under gravity.
As these clumps spin, material in the cloud forms a disk that accretes onto the forming star. If this disk fragments, another star, or multiple stars, can start forming in the same place – a little stellar family of siblings. After the star is done forming, what’s left of the disk can go on to form planets.
It’s estimated that some 40 to 50 percent of stars have a binary companion, and another 20 percent are in systems that have three or more stars.
These systems will be quite gravitationally complex, which may make it difficult for smaller objects to stick around – but nevertheless, around 2.5 percent of exoplanets are estimated to be in these multiple systems consisting of three stars or more.
To date, around 32 exoplanets have been found in trinary systems. And then a system called GW Orionis came along.
Located about 1,300 light-years away, GW Orionis caught astronomers’ attention because it’s surrounded by a huge, misaligned protoplanetary disk circling all three stars.
Using the powerful Atacama Large Millimeter/submillimeter Array (ALMA), astronomers confirmed something else about the system: There’s a substantial gap in the protoplanetary disk.
According to our models of planet formation, gaps in protoplanetary disks are likely to be caused by planets forming. As they go around the star, these planets sweep up the dust and gas in their orbital path, clearing it and leaving a gap.
In GW Orionis, things aren’t necessarily so clear-cut. Because the three stars would generate a complex gravitational field, there’s a possibility that any strange features in the disk could have been created by the stars themselves.
Previous analysis suggested that this is probably not the case; the gravitational interaction between the stars alone is not sufficient to have carved a gap in the disk, leaving a forming exoplanet as the likely explanation.
Now, a new analysis has agreed with this interpretation. Led by astronomer Jeremy Smallwood of the University of Nevada, Las Vegas, a team of researchers reconstructed a model of the GW Orionis system, integrating N-body and three-dimensional hydrodynamic simulations.
They found, just as researchers before them had, that the torque generated by the stars is not sufficient to have split the protoplanetary disk.
Instead, the culprit is likely a gas giant, like Jupiter, in the process of forming, or perhaps multiple gas giants. We’ve not seen the exoplanet itself, which means there’s still room for doubt, but the agreement between the two separate research efforts does seem to favor the baby exoplanet interpretation.
Which could mean that the planet formation process might be able to survive more extreme conditions than we expected, such as complicated environments like the space around triple stars.
“It’s really exciting because it makes the theory of planet formation really robust,” Smallwood said. “It could mean that planet formation is much more active than we thought, which is pretty cool.”
The team hopes that astronomers will be able to see the exoplanet or exoplanets directly in upcoming observations of the GW Orionis system.
The research has been published in the Monthly Notices of the Royal Astronomical Society.
Artist’s concept of a Hycean planet, with a global ocean and hydrogen atmosphere. Image via Amanda Smith/ University of Cambridge.
Is there life beyond Earth? It seems extremely probable, although we still don’t have the hard evidence. But astronomers said on August 26, 2021, that they’ve identified a new class of exoplanets that are a big step forward in the search for life. They’re calling them Hycean worlds, from the words hydrogen and ocean. Planet-wide oceans and hydrogen-rich atmospheres might cover these worlds. And yet, the researchers said, they might be habitable.
Researchers from the University of Cambridge led this intriguing research. The peer-reviewed Astrophysical Journal published it on August 26.
Hycean planets: Like Earth but different
According to the researchers, Hycean worlds could greatly accelerate the search for life elsewhere. In some ways they are reminiscent of Earth, largely or even completely covered by oceans. Yet they are also uniquely alien: up to 2.6 times the diameter of Earth, with temperatures up to 200 degrees C (about 400 degrees F) and thick hydrogen atmospheres. This places them somewhere between Earth and giant planets like Neptune or Uranus.
Indeed, many such worlds in this size range are already known to exist, the super-Earths and mini-Neptunes. Scientists say that planets in this size range are the most common in our galaxy.
There may also be different kinds of Hyceans, including “dark” and “cold.” As noted in the paper:
Our investigations include tidally locked “Dark Hycean” worlds that permit habitable conditions only on their permanent nightsides and “Cold Hycean” worlds that see negligible irradiation [receive little radiation from their stars].
Graphic representation of the habitable zones for Hycean planets, including both dark and cold. The habitable zone for terrestrial planets is much smaller. Black dots with rings are promising Hycean candidates. Image via Madhusudhan et al./ Kopparapu et al. 2013/ The Astrophysical Journal.
Super-Earths, mini-Neptunes and Hyceans
Super-Earths are rocky but larger than Earth. Even now, little is known about what kinds of atmospheres they have, although some have been found in the habitable zones of their stars where temperatures could allow liquid water. Mini-Neptunes though have long been thought to be inhospitable for life as we know it. Most mini-Neptunes lack a solid surface and the temperatures and pressures in their atmospheres would make it very difficult for life to evolve.
What the new study suggests, however, is that some of those worlds may be able to support life after all. Those are the Hyceans. As lead author Nikku Madhusudhan at the University of Cambridge stated:
Hycean planets open a whole new avenue in our search for life elsewhere.
Are Hycean planets habitable?
How, then, might Hycean planets be habitable? Having plentiful liquid water is of course a good start. These planets, unlike most mini-Neptunes, may have solid surfaces, like Earth. Many of the known Hycean candidates are larger and hotter than Earth, but still would be able to host large oceans, the researchers say. The conditions might be similar to some of the more extreme aquatic environments on our planet, but could theoretically still support at least microbial life.
Nikku Madhusudhan at the University of Cambridge led the new study about Hycean planets and their potential habitability. Image via University of Cambridge.
By their nature, these planets would also mean that the habitable zones around their stars could be a lot larger than those in systems with Earth-like planets. That’s another plus for the possibility of life. The habitable zone is the region around a star where temperatures would be suitable for liquid water on the surface of a rocky planet.
Another previous study, of the mini-Neptune K2-18b, supports the possibility of habitable Hycean worlds. Based on this study, scientists identified the new class of exoplanets, the Hyceans. While some scientists refer to K2-18b as a super-Earth, most now classify it as a mini-Neptune.
Looking for biosignatures
So, how would astronomers look for evidence of life on any of these worlds? They will search for biosignatures, chemical fingerprints of biological processes in the planets’ atmospheres. Some common ones are oxygen, ozone, methane and nitrous oxide, as well as methyl chloride and dimethyl sulphide. The last two are not common on Earth, but might be on hydrogen-rich planets. According to Madhusudhan:
Essentially, when we’ve been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start. But we think Hycean planets offer a better chance of finding several trace biosignatures.
Artist’s concept of K2-18b, the most promising candidate so far for a Hycean world. It orbits in the habitable zone of its star, and water vapor is already known to exist in its atmosphere. Image via ESA/ Hubble, M. Kornmesser/ UCL News.
Madhusudhan and his team say that many of these biosignatures should be easily detectable on Hycean planets. In fact, the nature of the planets themselves – larger sizes, higher temperatures and hydrogen-rich atmospheres – means that the biosignatures would be even more easily detectable than on Earth-like planets. From the paper:
We find that a number of trace terrestrial biomarkers that may be expected to be present in Hycean atmospheres would be readily detectable using modest observing time with the James Webb Space Telescope (JWST). We identify a sizable sample of nearby potential Hycean planets that can be ideal targets for such observations in search of exoplanetary biosignatures.
Upcoming observations
Excitingly, it might not be too long before we get some good spectroscopic observations of some Hycean planets. Astronomers already have a good sampling of candidate Hycean-type worlds to study, and upcoming space telescopes like the James Webb Space Telescope (the Webb) will be able to analyze their atmospheres. All the candidates are fairly close, from 35 to 150 light-years away, and orbit red dwarf stars.
K2-18b is currently the primary Hycean candidate, and observations with the Webb, which will launch sometime after October 31 this year, are already planned.
Most Hyceans are probably mini-Neptune-sized worlds. Both mini-Neptunes and super-Earths are larger than Earth but smaller than Neptune. Image via Patterson Clark/ Washington Post/ Quora.
If any of these candidate Hyceans do in fact support life, the upcoming studies with the Webb and other telescopes have a good chance of detecting signs of it. As Madhusudhan noted:
A biosignature detection would transform our understanding of life in the universe. We need to be open about where we expect to find life and what form that life could take, as nature continues to surprise us in often unimaginable ways.
Astronomers also announced last July that another mini-Neptune, TOI-1231 b, has a deep atmosphere ideal for further study by the Webb and the Hubble Space Telescope. It will be exciting to see what future observations of worlds like this, and Hyceans in particular, reveal.
Bottom line: Astronomers at the University of Cambridge have identified a new class of potentially habitable exoplanets called Hyceans. These are huge, hot worlds that could be covered by oceans and have thick hydrogen atmospheres.
Source: Habitability and Biosignatures of Hycean Worlds
Source (preprint): Habitability and Biosignatures of Hycean Worlds
Via University of Cambridge
Paul Scott Anderson
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About the Author:
Paul Scott Anderson has had a passion for space exploration that began when he was a child when he watched Carl Sagan’s Cosmos. While in school he was known for his passion for space exploration and astronomy. He started his blog The Meridiani Journal in 2005, which was a chronicle of planetary exploration. In 2015, the blog was renamed as Planetaria. While interested in all aspects of space exploration, his primary passion is planetary science. In 2011, he started writing about space on a freelance basis, and now currently writes for AmericaSpace and Futurism (part of Vocal). He has also written for Universe Today and SpaceFlight Insider, and has also been published in The Mars Quarterly and has done supplementary writing for the well-known iOS app Exoplanet for iPhone and iPad.
Astronomers have identified a new class of habitable planets, dubbed ‘Hycean’ planets – hot, ocean-covered planets with hydrogen-rich atmospheres – which could represent a big step forward in the search for life elsewhere. Credit: Amanda Smith, University of Cambridge
A new class of exoplanet very different to our own, but which could support life, has been identified by astronomers, which could greatly accelerate the search for life outside our Solar System.
In the search for life elsewhere, astronomers have mostly looked for planets of a similar size, mass, temperature and atmospheric composition to Earth. However, astronomers from the University of Cambridge believe there are more promising possibilities out there.
The researchers have identified a new class of habitable planets, dubbed ‘Hycean’ planets—hot, ocean-covered planets with hydrogen-rich atmospheres—which are more numerous and observable than Earth-like planets.
The researchers say the results, reported in The Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next two or three years is a real possibility.
“Hycean planets open a whole new avenue in our search for life elsewhere,” said Dr. Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research.
Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth’s most extreme aquatic environments.
These planets also allow for a far wider habitable zone, or ‘Goldilocks zone’, compared to Earth-like planets. This means that they could still support life even though they lie outside the range where a planet similar to Earth would need to be in order to be habitable.
Thousands of planets outside our Solar System have been discovered since the first exoplanet was identified nearly 30 years ago. The vast majority are planets between the sizes of Earth and Neptune and are often referred to as ‘super-Earths’ or ‘mini-Neptunes’: they can be predominantly rocky or ice giants with hydrogen-rich atmospheres, or something in between.
Most mini-Neptunes are over 1.6 times the size of Earth: smaller than Neptune but too big to have rocky interiors like Earth. Earlier studies of such planets have found that the pressure and temperature beneath their hydrogen-rich atmospheres would be too high to support life.
However, a recent study on the mini-Neptune K2-18b by Madhusudhan’s team found that in certain conditions these planets could support life. The result led to a detailed investigation into the full range of planetary and stellar properties for which these conditions are possible, which known exoplanets may satisfy those conditions, and whether their biosignatures may be observable.
The investigation led the researchers to identify a new class of planets, Hycean planets, with massive planet-wide oceans beneath hydrogen-rich atmospheres. Hycean planets can be up to 2.6 times larger than Earth and have atmospheric temperatures up to nearly 200 degrees Celsius, but their oceanic conditions could be similar to those conducive for microbial life in Earth’s oceans. Such planets also include tidally locked ‘dark’ Hycean worlds that may have habitable conditions only on their permanent night sides, and ‘cold’ Hycean worlds that receive little radiation from their stars.
Planets of this size dominate the known exoplanet population, although they have not been studied in nearly as much detail as super-Earths. Hycean worlds are likely quite common, meaning that the most promising places to look for life elsewhere in the Galaxy may have been hiding in plain sight.
However, size alone is not enough to confirm whether a planet is Hycean: other aspects such as mass, temperature and atmospheric properties are required for confirmation.
When trying to determine what the conditions are like on a planet many light years away, astronomers first need to determine whether the planet lies in the habitable zone of its star, and then look for molecular signatures to infer the planet’s atmospheric and internal structure, which govern the surface conditions, presence of oceans and potential for life.
Astronomers also look for certain biosignatures which could indicate the possibility of life. Most often, these are oxygen, ozone, methane and nitrous oxide, which are all present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulphide, that are less abundant on Earth but can be promising indicators of life on planets with hydrogen-rich atmospheres where oxygen or ozone may not be as abundant.
“Essentially, when we’ve been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start,” said Madhusudhan. “But we think Hycean planets offer a better chance of finding several trace biosignatures.”
“It’s exciting that habitable conditions could exist on planets so different from Earth,” said co-author Anjali Piette, also from Cambridge.
Madhusudhan and his team found that a number of trace terrestrial biomarkers expected to be present in Hycean atmospheres would be readily detectable with spectroscopic observations in the near future. The larger sizes, higher temperatures and hydrogen-rich atmospheres of Hycean planets make their atmospheric signatures much more detectable than Earth-like planets.
The Cambridge team identified a sizeable sample of potential Hycean worlds which are prime candidates for detailed study with next-generation telescopes, such as the James Webb Space Telescope (JWST), which is due to be launched later this year. These planets all orbit red dwarf stars between 35-150 light years away: close by astronomical standards. Planned JWST observations of the most promising candidate, K2-18b, could lead to the detection of one or more biosignature molecules.
“A biosignature detection would transform our understanding of life in the universe,” said Madhusudhan. “We need to be open about where we expect to find life and what form that life could take, as nature continues to surprise us in often unimaginable ways.”
Could life exist in the atmosphere of a sub-Neptune planet?
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Habitability and Biosignatures of Hycean Worlds, Astrophysical Journal (2021). doi.org/10.3847/1538-4357/abfd9c
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Gravity is the weird, mysterious glue that binds the Universe together, but that’s not the limit of its charms. We can also leverage the way it warps space-time to see distant objects that would be otherwise much more difficult to make out.
This is called gravitational lensing, an effect predicted by Einstein, and it’s beautifully illustrated in a new release from the Hubble Space Telescope.
In the center in the image (below) is a shiny, near-perfect ring with what appear to be four bright spots threaded along it, looping around two more points with a golden glow.
(ESA/Hubble & NASA, T. Treu; Acknowledgment: J. Schmidt)
This is called an Einstein ring, and those bright dots are not six galaxies, but three: the two in the middle of the ring, and one quasar behind it, its light distorted and magnified as it passes through the gravitational field of the two foreground galaxies.
Because the mass of the two foreground galaxies is so high, this causes a gravitational curvature of space-time around the pair. Any light that then travels through this space-time follows this curvature and enters our telescopes smeared and distorted – but also magnified.
Illustration of gravitational lensing. (NASA, ESA & L. Calçada)
This, as it turns out, is a really useful tool for probing both the far and near reaches of the Universe. Anything with enough mass can act as a gravitational lens. That can mean one or two galaxies, as we see here, or even huge galaxy clusters, which produce a wonderful mess of smears of light from the many objects behind them.
Astronomers peering into deep space can reconstruct these smears and replicated images to see in much finer detail the distant galaxies thus lensed. But that’s not all gravitational lensing can do. The strength of a lens depends on the curvature of the gravitational field, which is directly related to the mass it’s curving around.
So gravitational lenses can allow us to weigh galaxies and galaxy clusters, which in turn can then help us find and map dark matter – the mysterious, invisible source of mass that generates additional gravity that can’t be explained by the stuff in the Universe we can actually detect.
A bit closer to home, gravitational lensing – or microlensing, to be more precise – can help us find objects within the Milky Way that would be too dark for us to see otherwise, such as stellar-mass black holes.
And it gets smaller. Astronomers have managed to detect rogue exoplanets – those unattached from a host star, wandering the galaxy, cold and alone – from the magnification that occurs when such exoplanets pass between us and distant stars. And they’ve even used gravitational microlensing to detect exoplanets in other galaxies.
It’s pretty wild what the Universe has up its gravitational sleeves.
You can download a wallpaper-sized version of the above image on ESA’s website.
Thanks to data from NASA’s Transiting Exoplanet Survey Satellite (TESS), an international collaboration of astronomers has identified four exoplanets, worlds beyond our solar system, orbiting a pair of related young stars called TOI 2076 and TOI 1807.
These worlds may provide scientists with a glimpse of a little-understood stage of planetary evolution.
“The planets in both systems are in a transitional, or teenage, phase of their life cycle,” said Christina Hedges, an astronomer at the Bay Area Environmental Research Institute in Moffett Field and NASA’s Ames Research Center in Silicon Valley, both in California. “They’re not newborns, but they’re also not settled down. Learning more about planets in this teen stage will ultimately help us understand older planets in other systems.”
A paper describing the findings, led by Hedges, was published in The Astronomical Journal.
Stellar siblings over 130 light-years away host two systems of teenage planets. Watch to learn how NASA’s Transiting Exoplanet Survey Satellite discovered these young worlds and what they might tell us about the evolution of planetary systems everywhere, including our own. Credit: NASA’s Goddard Space Flight Center/Chris Smith (KBRwyle)
TOI 2076 and TOI 1807 reside over 130 light-years away with some 30 light-years between them, which places the stars in the northern constellations of Boötes and Canes Venatici, respectively. Both are K-type stars, dwarf stars more orange than our Sun, and around 200 million years old, or less than 5% of the Sun’s age. In 2017, using data from ESA’s (the European Space Agency’s) Gaia satellite, scientists showed that the stars are traveling through space in the same direction.
Astronomers think the stars are too far apart to be orbiting each other, but their shared motion suggests they are related, born from the same cloud of gas.
Both TOI 2076 and TOI 1807 experience stellar flares that are much more energetic and occur much more frequently than those produced by our own Sun.
“The stars produce perhaps 10 times more UV light than they will when they reach the Sun’s age,” said co-author George Zhou, an astrophysicist at the University of Southern Queensland in Australia. “Since the Sun may have been equally as active at one time, these two systems could provide us with a window into the early conditions of the solar system.”
TESS monitors large swaths of the sky for nearly a month at a time. This long gaze allows the satellite to find exoplanets by measuring small dips in stellar brightness caused when a planet crosses in front of, or transits, its star.
Planet TOI 1807 b is about twice Earth’s size and orbits a young dwarf, as shown in this illustration. It completes one orbit every 13 hours. Credit: NASA’s Goddard Space Flight Center/Chris Smith (KBRwyle)
Alex Hughes initially brought TOI 2076 to astronomers’ attention after spotting a transit in the TESS data while working on an undergraduate project at Loughborough University in England, and he has since graduated with a bachelor’s degree in physics. Hedges’ team eventually discovered three mini-Neptunes, worlds between the diameters of Earth and Neptune, orbiting the star. Innermost planet TOI 2076 b is about three times Earth’s size and circles its star every 10 days. Outer worlds TOI 2076 c and d are both a little over four times larger than Earth, with orbits exceeding 17 days.
TOI 1807 hosts only one known planet, TOI 1807 b, which is about twice Earth’s size and orbits the star in just 13 hours. Exoplanets with such short orbits are rare. TOI 1807 b is the youngest example yet discovered of one of these so-called ultra-short period planets.
Scientists are currently working to measure the planets’ masses, but interference from the hyperactive young stars could make this challenging.
According to theoretical models, planets initially have thick atmospheres left over from their formation in disks of gas and dust around infant stars. In some cases, planets lose their initial atmospheres due to stellar radiation, leaving behind rocky cores. Some of those worlds go on to develop secondary atmospheres through planetary processes like volcanic activity.
The ages of the TOI 2076 and TOI 1807 systems suggest that their planets may be somewhere in the middle of this atmospheric evolution. TOI 2076 b receives 400 times more UV light from its star than Earth does from the Sun – and TOI 1807 b gets around 22,000 times more.
If scientists can discover the planets’ masses, the information could help them determine if missions like NASA’s Hubble and upcoming James Webb space telescopes can study the planets’ atmospheres – if they have them.
The team is particularly interested in TOI 1807 b because it’s an ultra-short period planet. Theoretical models suggest it should be difficult for worlds to form so close to their stars, but they can form farther out and then migrate inward. Because it would have had to both form and migrate in just 200 million years, TOI 1807 b will help scientists further understand the life cycles of these types of planets. If it doesn’t have a very thick atmosphere and its mass is mostly rock, the planet’s proximity to its star could potentially mean its surface is covered in oceans or lakes of molten lava.
“Many objects we study in astronomy evolve on such long timescales that a human being can’t see changes month to month or year to year,” said co-author Trevor David, a research fellow at the Flatiron Institute’s Center for Computational Astrophysics in New York. “If you want to see how planets evolve, your best bet is to find many planets of different ages and then ask how they’re different. The TESS discovery of the TOI 2076 and TOI 1807 systems advances our understanding of the teenage exoplanet stage.”
Reference: “TOI-2076 and TOI-1807: Two Young, Comoving Planetary Systems within 50 pc Identified by TESS that are Ideal Candidates for Further Follow Up” by Christina Hedges, Alex Hughes, George Zhou, Trevor J. David, Juliette Becker, Steven Giacalone, Andrew Vanderburg, Joseph E. Rodriguez, Allyson Bieryla, Christopher Wirth, Shaun Atherton, Tara Fetherolf, Karen A. Collins, Adrian M. Price-Whelan, Megan Bedell, Samuel N. Quinn, Tianjun Gan, George R. Ricker, David W. Latham, Roland K. Vanderspek, Sara Seager, Joshua N. Winn, Jon M. Jenkins, John F. Kielkopf, Richard P. Schwarz, Courtney D. Dressing, Erica J. Gonzales, Ian J. M. Crossfield, Elisabeth C. Matthews, Eric L. N. Jensen, Elise Furlan, Crystal L. Gnilka, Steve B. Howell, Kathryn V. Lester, Nicholas J. Scott, Dax L. Feliz, Michael B. Lund, Robert J. Siverd, Daniel J. Stevens, N. Narita, A. Fukui, F. Murgas, Enric Palle, Phil J. Sutton, Keivan G. Stassun, Luke G. Bouma, Michael Vezie, Jesus Noel Villaseñor, Elisa V. Quintana and Jeffrey C. Smith, 12 July 2021, The Astronomical Journal. DOI: 10.3847/1538-3881/ac06cd
TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA’s Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes, and observatories worldwide are participants in the mission.
Astronomers using a new technique may have not only found a super-Earth at a neighbouring star, but they may also have directly imaged it. And it could be nice and cozy in the habitable zone around Alpha Centauri.
It’s much easier to see giant planets than Earth-size planets. No matter which detection method is being used, larger planets are simply a larger needle in the cosmic haystack. But overall, astronomers are very interested in planets that are similar to Earth. And finding them is much more difficult.
We thought we’d have to wait for the ultra-powerful telescopes currently being built before we could directly image exoplanets.
Facilities like the Giant Magellan Telescope and the European Extremely Large Telescope will bring enormous observing power to bear on the task of exoplanet imaging.
But a team of researchers have developed a new technique that might do the job. They say they’ve imaged a possible sub-Neptune/super-Earth-sized planet orbiting one of our nearest neighbours, Alpha Centauri A.
The team presented their observations in an article in Nature Communications titled “Imaging low-mass planets within the habitable zone of α Centauri.” The lead author is Kevin Wagner, an astronomer and Sagan Fellow at the University of Arizona.
While astronomers have found low-mass exoplanets before, they’ve never sensed their light. They’ve watched as the planets revealed themselves by tugging on their stars. And they’ve watched as the light from the stars that host these planets dips when the planet passes in front of the star.
But they’ve never directly imaged one. Until now, maybe.
This new detection method comes down to the infrared. One of the challenges in imaging Earth-sized exoplanets in infrared is to discern the light coming from an exoplanet when that light is washed out by all of the background infrared radiation from the star.
Astronomers can search for exoplanets in wavelengths where the background infrared is diminished, but in those same wavelengths, temperate Earth-like planets are faint.
One method is to look in the near-infrared (NIR) part of the spectrum. In NIR, the thermal glow of the planet is not so washed out by the star. But the starlight is still blinding, and millions of times brighter than the planet. So just looking in the NIR is not a total solution.
The solution may be the NEAR (New Earths in the AlphaCen Region) instrument used in this research. NEAR is mounted on the ESO (European Southern Observatory’s) Very Large Telescope (VLT) in Chile. It works with the VISIR instrument, also on the VLT. The group behind NEAR is the Breakthrough Watch, part of Yuri Milner’s Breakthrough Initiatives.
The NEAR instrument not only observes in the desirable part of the infrared spectrum, but it also employs a coronagraph.
The Breakthrough group thought that the NEAR instrument used on an 8-meter ground-based telescope would allow for better observations of the Alpha Centauri system and its planets.
So they built the instrument in collaboration with the ESO and installed it on the Very Large Telescope.
This new finding came as a result of 100 hours of cumulative observations with NEAR and the VLT.
“These results,” the authors write, “demonstrate the feasibility of imaging rocky habitable-zone exoplanets with current and upcoming telescopes.”
The 100-hour commissioning run was meant to demonstrate the power of the instrument.
The team says that based on about 80 percent of the best images from that run, the NEAR instrument is an order of magnitude better than other methods for observing “…warm sub-Neptune-sized planets throughout much of the habitable zone of α Centauri A.”
They also, possibly, found a planet. “We also discuss a possible exoplanet or exozodiacal disk detection around? Centauri A,” they write. “However, an instrumental artifact of unknown origin cannot be ruled out.”
This isn’t the first time astronomers have found exoplanets in the Alpha Centauri system.
There are a couple of confirmed planets in the system, and there are also other candidates.
But none of them have been directly imaged like this new potential planet, which has the placeholder name C1, and is the first potential detection around the M-dwarf in the system, Proxima Centauri.
Follow-up observations will have to confirm or cancel the discovery.
It’s exciting to think that a warm-Neptune class exoplanet could be orbiting a Sun-like star in our nearest neighbouring star system. One of the Breakthrough Initiatives goals is to send lightsail spacecraft to the Alpha Centauri system and give us a closer look.
But that prospect is out of reach for now. And in some ways, this discovery isn’t so much about the planet, but about the technology developed to detect it.
The large majority of discovered exoplanets are gigantic planets similar in mass to Jupiter, Saturn, and Neptune. They’re the easiest to find. But as humans from Earth, we’re predominantly interested in planets like our own.
Earth-like planets in a star’s habitable zone get us excited about prospects for life on another planet. But they can also tell us a lot about our own Solar System, and how solar systems in general form and evolve.
If C1 does turn out to be a planet, then the Breakthrough group has succeeded in a vital endeavour. They’re the first to detect an Earth-like planet by direct imaging.
Not only that, but they did it with an 8-meter, ground-based telescope and an instrument specifically designed and developed to detect these types of planets in the Alpha Centauri system.
The authors are confident that NEAR can perform well, even in comparison to much larger telescopes. The conclusion of the paper contains a description of the overall sensitivity of the instrument. Then they write that “This would in principle be sufficient to detect an Earth-analog planet around α Centauri A (~20 µJy) in just a few hours, which is consistent with expectations for the ELTs.”
The E-ELT will have a 39-meter primary mirror. One of its capabilities and design goals is to image exoplanets, especially smaller, Earth-size ones, directly.
Of course, the E-ELT will be an enormously powerful telescope that will undoubtedly fuel scientific discovery for a long time, not just in exoplanet imaging but in a variety of other ways.
And other gigantic ground-based telescopes will change the exoplanet imaging game, too.
What took hours for NEAR to see may take only minutes for the E-ELT, the Thirty Meter Telescope, or the Giant Magellan Telescope to see.
NEAR can’t compete with those telescopes and was never meant to.
But if these results are confirmed, then NEAR has succeeded where nobody else has, and for a fraction of the price of a new telescope.
Either way, what NEAR has accomplished likely represents the future of exoplanet research. Rather than broad-based surveys like Kepler and TESS, scientists will soon be able to focus on individual planets.
This article was originally published by Universe Today. Read the original article.
A pair of high schoolers are being commended for making a major astronomical discovery after they identified four new planets in orbit around a star approximately 200 light years away from Earth.
What are the details?
The two students, 16-year-old Kartik Pinglé and 18-year-old Jasmine Wright, both of whom attend schools in Massachusetts, were elated at taking part in the discovery and wrote about it in a peer-reviewed paper published by the Astronomical Journal last week.
The finding may make them the youngest astronomers yet to make such a major discovery, according to a press release about the news published by the Center for Astrophysics, a collaboration between Harvard University and the Smithsonian Institution.
The students made their discovery as part of the CFA’s “Student Research Mentoring Program,” an initiative that pairs students interested in research with real-world scientists who then together embark on a year-long project.
As part of the program, the high schoolers were selected to work alongside Tansu Daylan, a postdoctoral researcher at the Massachusetts Institute of Technology, analyzing data from the Transiting Exoplanet Survey Satellite (TESS), a satellite that orbits the Earth and surveys nearby bright stars hoping to discover new planets.
The team focused on a nearby Sun-like star referred to as TESS Object of Interest 1233 to perceive whether or not planets were in orbit around it.
“We were looking to see changes in light over time,” Pinglé explained regarding the research. “The idea being that if the planet transits the star, or passes in front of it, it would [periodically] cover up the star and decrease its brightness.”
While probing the star, the students had hoped to discover at least one planet, but to their surprise, they ended up finding four.
“I was very excited and very shocked,” Wright said of the discovery. “We knew this was the goal of Daylan’s research, but to actually find a multiplanetary system, and be part of the discovering team, was really cool.”
According to the research paper, the three outer planets are considered “sub-Neptunes,” or gaseous planets that are smaller than but otherwise similar to our solar system’s planet of the same name, while the innermost planet is considered a “super-Earth” due its large size and rockiness.
What else?
The program’s director, Clara Sousa-Silva, noted that Pinglé and Wright’s achievement is rare.
“Although [it] is one of the goals of the SRMP, it is highly unusual for high-schoolers to be co-authors on journal papers,” she said in the press release.
Daylan added that it was a “win-win” to work alongside Pinglé and Wright and make a major discovery
“As a researcher, I really enjoy interacting with young brains that are open to experimentation and learning and have minimal bias,” he said. “I also think it is very beneficial to high school students, since they get exposure to cutting-edge research and this prepares them quickly for a research career.”
According to the press release, Pinglé, who is still just a junior in high school, is considering studying applied mathematics or astrophysics after graduating, while Wright has been accepted into a five-year master of astrophysics program at the University of Edinburgh in Scotland.
A five-planet system around TOI-1233 includes a super-Earth (foreground) that could help solve mysteries of planet formation. The four innermost planets were discovered by high schoolers Kartik Pinglé and Jasmine Wright alongside researcher Tansu Daylan. The fifth outermost planet pictured was recently discovered by a separate team of astronomers. Artist rendering. Credit: NASA/JPL-Caltech
The high schoolers turned scientists published their findings this week, thanks to a research mentorship program at the Center for Astrophysics; Harvard and Smithsonian.
They may be the youngest astronomers to make a discovery yet.
This week, 16-year-old Kartik Pinglé and 18-year-old Jasmine Wright have co-authored a peer-reviewed paper in The Astronomical Journal describing the discovery of four new exoplanets about 200-light-years away from Earth.
The high schoolers participated in the research through the Student Research Mentoring Program (SRMP) at the Center for Astrophysics | Harvard & Smithsonian. Directed by astrochemist Clara Sousa-Silva, the SRMP connects local high schoolers who are interested in research with real-world scientists at Harvard and MIT. The students then work with their mentors on a year-long research project.
“It’s a steep learning curve,” says Sousa-Silva, but it’s worth it. “By the end of the program, the students can say they’ve done active, state-of-the-art research in astrophysics.”
Pinglé and Wright’s particular achievement is rare. High schoolers seldom publish research, Sousa-Silva says. “Although that is one of the goals of the SRMP, it is highly unusual for high-schoolers to be co-authors on journal papers.”
With guidance from mentor Tansu Daylan, a postdoc at the MIT Kavli Institute for Astrophysics and Space Research, the students studied and analyzed data from the Transiting Exoplanet Survey Satellite (TESS). TESS is a space-based satellite that orbits around Earth and surveys nearby bright stars with the ultimate goal of discovering new planets.
The team focused on TESS Object of Interest (TOI) 1233, a nearby, bright Sun-like star. To perceive if planets were orbiting around the star, they narrowed in on TOI-1233’s light.
“We were looking to see changes in light over time,” Pinglé explains. “The idea being that if the planet transits the star, or passes in front of it, it would [periodically] cover up the star and decrease its brightness.”
To the team’s surprise, they discovered not one but four planets orbiting around TOI-1233.
“I was very excited and very shocked,” Wright says. “We knew this was the goal of Daylan’s research, but to actually find a multiplanetary system, and be part of the discovering team, was really cool.”
Three of the planets are considered “sub-Neptunes,” gaseous planets that are smaller than, but similar to our own solar system’s Neptune. It takes between 6 and 19.5 days for each of them to orbit around TOI-1233. The fourth planet is labeled a “super-Earth” for its large size and rockiness; it orbits around the star in just under four days.
Daylan hopes to study the planets even closer in the coming year.
“Our species has long been contemplating planets beyond our solar system and with multi-planetary systems, you’re kind of hitting the jackpot,” he says. “The planets originated from the same disk of matter around the same star, but they ended up being different planets with different atmospheres and different climates due to their different orbits. So, we would like to understand the fundamental processes of planet formation and evolution using this planetary system.”
Daylan adds that it was a “win-win” to work with Pinglé and Wright on the study.
“As a researcher, I really enjoy interacting with young brains that are open to experimentation and learning and have minimal bias,” he says. “I also think it is very beneficial to high school students, since they get exposure to cutting-edge research and this prepares them quickly for a research career.”
The SRMP was established in 2016 by Or Graur, a former postdoctoral fellow at the Center for Astrophysics |Harvard & Smithsonian. The program accepts about a dozen students per year with priority given to underrepresented minorities.
Thanks to a partnership with the City of Cambridge, the students are paid four hours per week for the research they complete.
“They are salaried scientists,” Sousa-Silva says. “We want to encourage them that pursuing an academic career is enjoyable and rewarding–no matter what they end up pursuing in life.”
Reference: “TESS Discovery of a Super-Earth and Three Sub-Neptunes Hosted by the Bright, Sun-like Star HD 108236” by Tansu Daylan, Kartik Pinglé, Jasmine Wright, Maximilian N. Günther, Keivan G. Stassun, Stephen R. Kane, Andrew Vanderburg, Daniel Jontof-Hutter, Joseph E. Rodriguez, Avi Shporer, Chelsea X. Huang, Thomas Mikal-Evans, Mariona Badenas-Agusti, Karen A. Collins, Benjamin V. Rackham, Samuel N. Quinn, Ryan Cloutier, Kevin I. Collins, Pere Guerra, Eric L. N. Jensen, John F. Kielkopf, Bob Massey, Richard P. Schwarz, David Charbonneau, Jack J. Lissauer, Jonathan M. Irwin, Özgür Bastürk, Benjamin Fulton, Abderahmane Soubkiou, Benkhaldoun Zouhair, Steve B. Howell, Carl Ziegler, César Briceño, Nicholas Law, Andrew W. Mann, Nic Scott, Elise Furlan, David R. Ciardi, Rachel Matson, Coel Hellier, David R. Anderson, R. Paul Butler, Jeffrey D. Crane, Johanna K. Teske, Stephen A. Shectman, Martti H. Kristiansen, Ivan A. Terentev, Hans Martin Schwengeler, George R. Ricker, Roland Vanderspek, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Zachory K. Berta-Thompson, Luke G. Bouma, William Fong, Gabor Furesz, Christopher E. Henze, Edward H. Morgan, Elisa Quintana, Eric B. Ting and Joseph D. Twicken, 25 January 2021, The Astronomical Journal. DOI: 10.3847/1538-3881/abd73e
Pinglé, a junior in high school, is considering studying applied mathematics or astrophysics after graduation. Wright has just been accepted into a five-year Master of Astrophysics program at the University of Edinburgh in Scotland.
