Sometimes science can seem really counter-intuitive. For example, occasionally in astronomy, you can see more with less light. Case in point: the emergence of a giant planet in observations made by the James Webb Space Telescope (JWST), when astronomers found a way to block out light from the planet's parent star.
The extrasolar planet, or exoplanet, in question is 51 Eridani b (51 ERI b), a gas giant with the same mass as around 11 Jupiters that orbits a star located around 97 light-years away. 51 ERI b was discovered back in 2015 by ground-based telescopes, but the planet was missing from observations of the system made by the JWST. That wasn't a failing of the JWST itself; no one is doubting the observing capabilities of the most powerful telescope humanity has ever hoisted into orbit around Earth. Instead, it was a result of starlight from the star 51 ERI A obscuring this intimidatingly massive world.
The brightest planets are 100,000 times fainter than their host stars, meaning spotting them is like observing a firefly hovering around a lighthouse. Even using a tool called a coronagraph to block the star isn't enough to reveal the planet, as that doesn't stop all the starlight.
The only solution to this glaring problem is a computer program to wipe out the starlight.
"For the past 20 years, astronomers have tackled this problem by observing a different star and using its image as a reference," Jason Wang of Northwestern University explained in a statement. "Then, they subtract that reference image from the original observation to remove the unwanted glare to reveal faint planets that otherwise might be hidden."
There is a problem with this process, however. Even the most stable telescopes "wobble." For instance, the JWST requires cryocoolers to keep its NIRCam instrument super cold, and those coolers have little motors that can cause the mirrors to vibrate. This movement, however slight, causes a scatter in starlight.
The result is enough glare remaining to obscure a planet, but Wang and colleagues developed a new approach to this problem.
Telescopes their more stable digital twins
The new approach taken by the team is dubbed Physics-based Learning for Imaging Planets (FLIP), and it involves creating a digital "twin" of a telescope. Essentially a virtual replica that simulates how starlight travels through the telescope's mirrors and reaches its detectors.
This twin is then fine-tuned to account for millions of tiny imperfections in the original telescope. The digital twin is then tweaked until it aligns with observations from the actual telescope. Astronomers can then remove the simulated glare from the original image.
To assess the validity of the technique, the researchers took a second look at JWST observations of two star systems with known exoplanets, HIP 65426 and 51 Eridani, and one system, TYC 5899, with no known planets.
The researchers found that, in terms of detecting faint exoplanets, FLIP outperformed conventional image-processing techniques two to 15 times. This led to ERI b emerging from data collected by the JWST two years ago.
"We showed that we can actually recover a planet that people previously couldn't see," Wang said. "This is real data in a real scenario. It was science left on the table because we didn’t have the right tools to analyze the data in the most optimal way."
Left: JWST/NIRCam observation of star 51 Eridani A (51 Eri) in the F430M filter, using standard method KLIP to subtract the glare of the star. Middle: The same observation, but using new method FLIP to subtract the glare of the star. Right: Simulated image of 51 Eri b (Image credit: Rodrigo Ferrer-Chavez.)
The team hopes that FLIP can now be adopted by other astronomers in a bid to recover hitherto undiscovered exoplanets that have been hidden by the glare of their stars.
"We know of no planets around other stars that are like those in our own solar system," team leader Rodrigo Ferrer-Chavez of Northwestern University said. "It's not that they don’t exist. It's that we cannot see them.
"Every time we improve our techniques, we discover new types of planets. By finding more planets, we can better understand how planetary systems form and evolve, and ultimately how typical our own solar system truly is."
The team's research was published on Wednesday (Nov. 4) in the journal Nature.
Earth would be terrifying if we celebrated Halloween every 11 hours, a possibility on a super-Earth investigated by the James Webb Space Telescope (JWST). That is, if this extrasolar planet, or exoplanet, wasn't so hellishly hot that no life could survive on its surface.
The exoplanet in question is the rocky lava planet TOI-561 b, located around 280 light-years away, which was discovered by NASA's exoplanet-hunting spacecraft TESS (Transiting Exoplanet Survey Satellite) in 2020. The planet is located so close to its star, TOI-561, that not only does it complete an orbit every 11 hours, but its surface temperatures reach in excess of 3,000 degrees Fahrenheit (1,800 degrees Celsius).
That is so hot that astronomers once believed that TOI-561 b couldn't possibly possess an atmosphere. With 37 hours of JWST observations covering nearly four full orbits of TOI-561, scientists have now found this horrific planet is buried in a reflective layer of vaporized silicate mineral clouds, the same family of compounds that make up quartz and sand.
"We measured how the planet's brightness and heat changed throughout its orbit," team member Lisa Dang of the University of Waterloo said in a statement. "This technique, known as a phase curve, revealed that the planet reflects a significant amount of light from its star, and that heat is being redistributed around the planet instead of only on the sunlit side. Together, these point to the presence of an atmosphere."
The hemispheres of lava super-Earth are day and night
The proximity of TOI-561 b to its star has another consequence. The planet is tidally locked, meaning it doesn't turn like Earth. Thus, TOI-561 b has one blisteringly hot "dayside" permanently facing its star, and a cooler "nightside" facing out into space in perpetuity.
Dang and colleagues investigated the fact that the bare rock of the dayside seemed to be cooler than should be expected. They theorized that missing heat could be carried around to the night side or the heat may be reflected away before TOI-561 b can absorb it.
By using the JWST to observe full orbits of TOI-561 b, the team was able to observe the planet's nightside for the first time. They found it isn't warm enough to account for all the heat missing from the dayside.
That means TOI-561 b must reflect roughly three-quarters of the starlight that hits it. That is comparable to the most reflective planet in the solar system, Venus, which reflects around 75% of incident sunlight compared to the 30% reflected by Earth.
The team determined that this high reflectivity is the result of clouds of silicate minerals, including silicon dioxide and magnesium silicate, forming on the planet's dayside and acting like sunscreen. These clouds could also help TOI-561 b hang on to an atmosphere.
A diagram shows that TOI-561 b and its two exoplanet siblings would fit well within the orbit of Mercury around the sun (Image credit: NASA)
Of course, the team can't yet be sure what this atmosphere is composed of. It could be a dense carbon dioxide fog like that seen on Venus, or it could be a blanket of sulfur dioxide like that of the most volcanic body in the solar system, Jupiter's moon Io. That would be the case if, like on Io, volcanic activity is replenishing the atmosphere of TOI-561 b.
"The next big question we will seek to answer is whether TOI-561 b's atmosphere resembles Venus or an extreme version of Io," Dang said. "Observing the planet at longer wavelengths with JWST could give us insights and help explain how a planet this hot has held on to an atmosphere for billions of years."
Using data from the James Webb Space Telescope (JWST), astronomers have unraveled some of the atmospheric secrets of a bizarre, blisteringly hot world that has the consistency of marshmallow.
The extrasolar planet, or exoplanet, under the watchful infrared eye of the JWST, is WASP-17b, located around 1,300 light-years away. The exoplanet has a mass around 0.8 times that of Jupiter, but it is around twice as wide as the solar system's largest planet, giving it a "super-puff" consistency comparable to the Earth-based treat. WASP-17 b is so close to its parent star that it completes an orbit in under four Earth days, with this proximity also making the temperature of this "hot Jupiter" skyrocket.
Given the extreme conditions of this exoplanet, it is little wonder that its atmosphere is pretty unusual too. Using a new technique called transmission strings, a team of scientists mapped the contours of the atmosphere of WASP-17b. They found that the atmosphere is shaped like a ring with prominent "gems" rising from it.
"Planets are temperamental, their atmospheres complex and chaotic," team member Hannah Wakeford of the University of Bristol said in a statement. "The fact that all of these numbers came together and showed us this very structured, dynamical picture of this giant world over 1,000 light-years away was just really exciting."
Astronomers like WASP-17b so much they put a ring on it
WASP-17b is so close to its parent star that it is tidally locked, meaning one side permanently faces the star; its dayside is constantly bombarded with stellar radiation. In contrast, the planet also has a cooler nightside, which faces out into space in perpetuity.
By creating incredibly comprehensive 3D views of this exoplanet's atmosphere, researchers found that WASP-17b's atmosphere has a chemical composition and temperature that shift between dayside and nightside according to theory and modelling.
This was possible because the transmission strings technique tracked WASP-17b as it crossed or transited in front of its star, capturing the composition of light around the edge of the planet's atmosphere, or limb, from different angles. This method trumps standard approaches because traditional modelling only maps light as an average across the entire limb.
"Rather than assuming your atmosphere is a circle with the same radius all the way around, our technique allows you to pull out different distances from the center to the edge of the planet," Lili Alderson, of Cornell University, said. "We're able to go around the edge.
"So, we've gone from a ring to understanding where on the ring the gemstones are, so to speak."
The modelling showed just such a "gem," that occurs where hot winds from the planet reach the equator and the nightside of WASP-17b, the atmosphere of the cooler side inflates.
An illustration of the atmosphere of WASP-17b with "gems" rising from it. (Image credit: Robert Lea)
"Theory predicts that the morning and the evening sides should have a strong temperature difference, and WASP-17b fits really nicely in that trend – pretty much bang-on what we thought it would be," Alderson said.
The successful application of the transmission strings method is an exciting step forward in the modelling of the atmospheres of the over 6,000 worlds in NASA's exoplanet catalog.
"This is proof of concept that planets are, in fact, 3D objects, and that, consistently, as they go around their star, what we predict should be happening is happening," Alderson concluded. "To move beyond computational exercises and see it for real is a different matter."
The team's research was published on Wednesday (Oct.14) in the journal Nature Astronomy.
You can tell a lot about how a child will age by looking at their parents, and it turns out that this could be true for planetary systems, too. Scientists have performed cosmic genealogy on planetary systems in the Milky Way, finding two distinct families that influence the evolution and fate of these systems.
The study team, led by researchers at the Italian National Institute for Astrophysics (INAF), studied 300 of the best-understood multiplanet systems of the over 1,000 that astronomers have discovered in the Milky Way.
The team's research clarifies how the environments around infant stars directly affect planetary fates and, in turn, the survival of extrasolar planets, or exoplanets, that are potentially capable of hosting life. That could be crucial as astronomers search for life beyond the solar system, pointing them to systems with potentially habitable planets like Earth.
"The fundamental question we started from was: What determines the characteristics of planetary systems as we see them today? Are they established at birth or sculpted by evolution over time? The truth, in the end, turned out to lie somewhere in the middle," team member and INAF researcher Diego Turrini said in a statement sent to Space.com.
"Our results show that there is a genetic link between planetary systems and their stars, and that, depending on the star around which they are born, this link also determines their fate," Turrini added.
What is the genetic code of a planetary system?
The first "family" the scientists identified consists of wide, massive systems, often with total masses between two and 10 times that of our own solar system. The planets in these systems orbit stars more massive than the sun with lower concentrations of elements heavier than hydrogen and helium (which astronomers somewhat confusingly call metals) than seen in our star.
The second family is more compact and lower-mass systems. The members of this family are composed of planets with comparable masses and sizes, a so-called "peas-in-a-pod" configuration. They orbit stars with mass and metallicity equal to or lower than those of the sun, with orbits that are usually much tighter than those of Mercury, the closest planet to the sun.
One of the "genes" Turrini and colleagues selected to sort planetary systems into families was the deviations that planets make from orbiting their star in the same circular plane. That, in turn, reveals a family history of violent gravitational instability caused by events like giant collisions and planetary ejections.
Violent events were common for the first family, but much less so for the second group of planetary systems, the researchers found. They determined that the number of these turbulent events a planetary system experiences can be linked to even modest variations in the environment in which planets form. These variations arise due to different properties of the parent star of those systems.
Thus, the nature of the star in these systems doesn't just fundamentally change the formation of planets in their systems; it influences the system's future evolution, determining whether it will be characterized by phases of marked instability and giant impacts.
An illustration shows two planets colliding. Such collisions may be more common around certain types of stars (Image credit: Robert Lea (created with Canva))
"The main difficulty during the data analysis was determining whether the two families of planetary systems were real or just an illusion created by the technological limits of current observational techniques," said team member Camilla Danielski, of the University of Valencia in Spain.
"At the end of the path, it became clear that selection effects acted as the tip of the iceberg, revealing the existence of much deeper structural diversities between these systems," Danielski said.
The scientists tested their conclusions by running simulations of planetary system evolution, all of which began with different conditions.
"The scenarios that best reproduce the dynamical properties of the family of wide and massive systems are those in which the systems are unstable from birth," said research supervisor and INAF researcher Danae Polychroni. "The greater abundance of material from which planets form around their host stars causes them to be born too large, preventing the system from remaining stable."
The team's research was published on Tuesday (Oct. 13) in the journal Nature Astronomy.
Astronomers have discovered the youngest exoplanet on record, and they spotted the "newborn" world hiding in old data archives.
About as massive as Jupiter, the newly-discovered exoplanet Elias 2-24 b is one big baby — despite its hefty size, Elias 2-24 b is by far the youngest planet ever found, thought to be less than a million years old. In fact, the exoplanet (or, planet outside of our solar system) was located 450 light-years away from Earth, still resting in the swirling gas and dust where it was born.
The previous record-holder for "youngest exoplanet" is a four-way tie between four worlds that are all over 5 million years old, according to Lucas Cieza, co-author of a study on Elias 2-24 b and a professor at the Instituto de Estudios Astrofísicos in Chile. "Our planet-formation models already struggled to explain the previous record holders for the youngest known planet," Cieza said in a statement. "Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes."
To spot this massive baby, a team led by Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, dug through archival data captured by the W.M. Keck Observatory in Hawaii. The study focused on the star Elias 2-24 which is surrounded by a disk of material. Their findings confirmed earlier observations collected with the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Southern Observatory's Very Large Telescope which suggested something may lie in a gap within the debris disk around Elias 2-24.
The archival data that confirmed these suspicions and this planet came from observations using Keck's coronagraph. Coronagraphs work by blocking out the glare from far-off starlight, allowing light bouncing off the planets orbiting those stars to be captured for direct observations. The team looked through such coronagraph data for seven distant stars, each surrounded by debris disks where planet formation may be happening. The team thought that perhaps it'd be possible to find a planet hiding in a gap in one of these disks. And they were right.
"The planets should be found within the gaps, since they are carving them," Bernardi said. "And that’s exactly where we found Elias 2-24 b."
By finding a planet in one of these disks, and by finding a planet so early in its lifetime, this finding gives researchers an opportunity to study the earlier development stages of planet formation.
"The galaxy churns out new stars and planets continuously, so there are many in every stage of evolution," Cieza said. "That means we can see the entire process in theory, but there is a large gap in what most telescopes can detect. We are mostly blind to these baby planets right now."
In looking at the future of planet detection and study, researchers hope to be able to conduct more direct observations with the Coronagraph Instrument that just launched (Aug. 30) aboard NASA's Nancy Grace Roman Space Telescope. This is the most advanced coronagraph ever launched to space, and scientists hope it will allow for more in-depth study of exoplanets and their atmospheres.
"We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together," Bernardi said. "Elias 2-24 b is at the limit of what current telescopes can detect, but with new instruments like NASA’s Nancy Grace Roman Space Telescope, such detections should become easier."
This work was described in a new study published Sept. 16 in the journal The Astrophysical Journal Letters.
A brand new observatory began its tenure on Aug. 30 — it's called the Nancy Grace Roman Space Telescope, and it's equipped with a high-tech tool that can directly photograph planets beyond our solar system.
The tool is called a coronagraph; in simple terms, a coronagraph is a device that can be affixed to a telescope and block out the light of a star the telescope is looking at to study features around that star. Without such a device, starlight can be so overpowering that it outshines details nearby. You can think of a coronagraph as a way to recreate a total solar eclipse, except instead of the moon blocking out the sun it's a humanmade mask of sorts that does that trick.
But while coronagraphs have been used many times before, the one that just launched toward the stars is unprecedented. "The Roman Space Telescope is carrying the most advanced coronagraph that humanity has ever put into space," Dominic Benford, the telescope's program scientist, told Space.com.
If you can remember the striking "Pale Blue Dot" image of Earth that NASA's Voyager 1 spacecraft captured while floating about 3.7 billion miles (6 billion kilometers) from the sun, this is the kind of thing scientists expect to see with Roman's coronagraph. A menagerie of Pale Brown Dots should soon make us feel the weight of our existence.
"I love the feeling of smallness that comes from understanding you're not alone in the universe," Vanessa Bailey, Roman's coronagraph instrument scientist, told Space.com.
Earth as a "pale blue dot" seen by Voyager 1 in 1990. (Image credit: NASA/JPL-Caltech)
How does it work?
Coronagraphs aren't really a new thing. Often, they're even used to study our own sun.
For example, NASA's PUNCH mission — which stands for Polarimeter to Unify the Corona and Heliosphere — launched in 2025 and consists of four spacecraft, one of which holds a coronagraph. This coronagraph blocks out the light of our sun in order to reveal the wispy tendrils of the sun's outer atmosphere, or corona.
"In fact, more than 100 years ago, astronomers used coronagraphs to create an artificial eclipse to study the sun's corona," Bailey said during a press briefing on Aug. 29, a day before Roman launched to space. "That's the reason for the name."
But when it comes to other stars, coronagraphs hold another purpose. They can block out a star's light in such a way that planets actually orbiting that star come into view.
"We can block that starlight until we have only a few parts per billion of the light of the star remaining," Benford said of Roman's coronagraph. As a result, he explained, "we can directly see the light bouncing off something like a Jupiter around another star, which we've never been able to do before."
NASA's Solar and Heliospheric Observatory, or SOHO, constantly observes the outer regions of the sun's corona using a coronagraph, which blocks the bright solar disk. (Image credit: ESA/NASA/SOHO)
This process will surely give us our Pale Brown Dots — but to take things a step further, scientists will also be able to dissect the light bouncing off the theoretical Jupiter to reveal what the atmosphere of the world is like, too.
To be clear, Roman isn't the only astronomy tool we have that utilizes a coronagraph while looking beyond our solar system. Even the James Webb Space Telescope and Hubble Space Telescope have their own, for that matter. However, Roman's is far more complex.
For one, the Roman's coronagraph doesn't exactly "block" out starlight like a standard coronagraph does. For the "moon" in its artificial eclipses, it uses a combination of patterned disks and special filters to create destructive interference with the light of a target star. Destructive interference means competing waves of light cancel one another out, leading to a zeroed amplitude. In effect, this blocks out the starlight as necessary and only allows light reflected off the planets of interest to pull through and reflect off the coronagraph's mirrors.
A diagram showing what the disk's pattern might look like. (Image credit: NASA's Goddard Space Flight Center)
The first active coronagraph
Which brings us to the next special part about Roman's coronagraph: It's the first "active" coronagraph to fly in space.
What this means is it can adjust those mirrors in real-time to make sure its exoplanet observations are as clear as possible. This is important because as light reflects off the coronagraph's mirrors, it can create small distortions that mess up the delicate destructive interference dance. You'd need to adjust to bring the balance back, and these adjustments are possible because Roman's coronagraph has hundreds of tiny pistons built into its mirrors. This makes them deformable so they can change shape to account for distortions.
If it all works out, this coronagraph should be capable of detecting exoplanets that are about 100 million times fainter than their stars.
"These deformable mirrors are a real engineering feat," Bailey said during the press briefing. "They can be commanded with the precision approaching the size of an atom, and this is what really allows us to make this transformative performance."
The Roman Space Telescope's coronagraph as scientists were working on it. (Image credit: NASA/JPL-Caltech)
As for what the specific hope is for Roman's coronagraph, Bailey explained there are a few nearby star systems the team is particularly interested in peering into because we have hints of Jupiter-like planets orbiting in those systems that still haven't been imaged. "Or," she said, "there may be really interesting remnants of dust and debris from the process of planet formation." Perhaps that dust could exist in the habitable zones of the stars Roman looks toward, and perhaps this could tell us more about the birth of planet Earth.
"That is interesting in its own regard but also interesting as a precursor to the Habitable Worlds Observatory," Bailey said, in reference to NASA's next great project that will be equipped with a more advanced version of Roman's coronagraph. "We can study how dusty these nearby systems are and understand whether any of them might have too much dust for us to be able to observe an Earth-like planet in the future."
An animation shows what Roman looks like deploying in space. (Image credit: NASA’s Goddard Space Flight Center Conceptual Image Lab)
While Roman will pretty much be focusing on Jupiter-like worlds because they're big enough to be detected with its current capabilities, HWO could certainly find another Earth someday.
From 6,000 exoplanets to 100,000
And before we wrap up, we must briefly mention this newly christened exoplanet hunter's partner tool, the majorly impressive Wide Field Instrument (WFI) that can survey huge swaths of sky in one go. It is because of the partnership between the WFI and its coronagraph that Roman will immensely expand our exoplanet gallery, says associate administrator for NASA's Science Mission Directorate Nicky Fox. The coronagraph won't be finding new exoplanets alone, but rather will be diving deeper into exoplanets the WFI finds first.
The Roman Space Telescope's WFI. (Image credit: NASA/Chris Gunn)
WFI will use two different techniques to contribute to our gallery. The first one is called the transit technique, and it's the same method big names like Kepler and TESS tapped into. It involves noticing dips in starlight that happen when a possible planet transits the face of a star from the telescope's vantage point. "If you see that happen multiple times," Fox said, "you can infer that it's a planet, and you can get the radius and the size of the planet from that observation."
The second technique has to do with gravitational lensing, which refers to how objects with mass in space (and therefore gravitational influence) can warp the very fabric of spacetime and alter the path of light traveling through the affected region. What comes to mind might be a mighty galaxy cluster twisting spacetime like a sheet of satin, but little things like stars and planets can do it, too. The so-called "microlensing" effect of smaller objects warping spacetime leads to the brightening of background objects.
Fox sums up WFI's two techniques in a nutshell: "If you see a little dip, that can suggest there's a transiting planet. You see a little brightening, that can suggest there's a microlensing planet."
For WFI, the microlensing technique will be sensitive to Earth-size planets in the habitable zones of their stars, while the transiting technique will be more sensitive to planets closer to their stars. And as Bailey reminds us, there are absolute heaps of planets to test Roman out on: "When you look up at the night sky, most of those stars have planets."
Right now, we only know of about 6,000 of those worlds. Fox believes this new space telescope could unveil 100,000 more.
Astronomers have discovered a new ocean world outside the solar system that orbits extremely close to its parent star. This means that the extrasolar planet, or "exoplanet," is in hot water, both literally and figuratively.
The exoplanet orbits the star HD 176071 located around 335 light-years away, and is about two and a half times the size of Earth, but has about eight and a half times the mass of our planet. That indicates to scientists that this planet is about 50% water. At a distance from its star of just under 1.5 million miles (about 1.6% of the distance between the Earth and the sun) and with a year lasting just 14 hours, HD 176071 b is a rare example of a "hot water world."
That close distance to its star means the planet experiences extreme tidal forces due to the pull of the star's gravity. These forces are driving the planet, designated HD 176071 b, towards a rapid and inexorable fatal encounter that will see it eventually violently devoured by its host star.
The exoplanet is also a rare occupant of what scientists call "Neptunian Desert" a term which describes a lack of Neptune sized worlds orbiting very close to their host stars. This is thought to be because intense stellar radiation strips planets of their gaseous layers effectively shrinking them. However, HD 176071 b seems to defy this suggestion, as this water world possesses surprisingly a dynamic atmosphere that hasn't been stripped away.
"Comparing historical data from the Kepler space telescope with new TESS (Transisting Exoplante Survey Satellite) observations six years later, we noticed an unexpected phase shift in the modulation of the reflected light," lead researcher Sylvain N. Breton of the Italian National Institute for Astrophysics (INAF) said in a statement.
"This tells us that we are not looking at a static photograph, but a living and changing atmosphere, in which dense, highly reflective clouds form, evolve, and move along the planet's coldest edges."
That isn't the only extraordinary thing about HD 176071 b. The way the ocean exoplanet was initially discovered is pretty special too.
This ocean world doesn't cross its stellar parent
Currently NASA's catalog of confirmed exoplanets has over 6,000 entries with thousands more worlds beyond the solar system awaiting conformation. The vast majority of these were discovered when they passed in from of their host star and caused a tiny dip in starlight reaching us from that stellar body in what's known as the transit method of exoplanet detection.
Thus, the transit method requires the planet to pass between its star and Earth. As you may imagine, that's a really fortunate arrangement for astronomers to find new planets in. Most known planets in the Milky Way don't do that.
"The vast majority of planets in the universe never transit in front of their star from Earth's perspective, making them virtually invisible," Breton said.
HD 176071 b is just such a world, with this geometric hinderance, so Breton and colleagues had to be crafty to discover this water world.
A diagram shows how the transit method of exoplanet detection works (Image credit: NASA)
The team still used the starlight of the parent star of HD 176071 b to detect the exoplanet, but instead hunted for tiny fluctuations in brightness caused when the light from this star was reflected from the planet. HD 176071 b is tidally locked, meaning it has a permanent "dayside" facing its star, and a perpetual "nightside" facing out to space. The variations in brightness result because sometimes the nightside of the planet faces us, and other times our instruments see its dayside.
"Thanks to the dataset acquired with the HARPS-N instrument on the Galileo National Telescope, we have managed to overcome this geometric obstacle: by measuring with extreme precision how the light reflected by the planet varies throughout its orbital journey, we can not only detect these elusive worlds, but also begin to characterize their structure and atmosphere, opening a fundamental window onto previously almost inaccessible planetary populations," Breton said.
The discovery of HD 176071 b shows that current astronomy techniques are sophisticated enough to characterize the atmosphere and internal structure of worlds beyond the solar system. That is a big boost for the detection of worlds that don't pass between Earth and their host star.
Astronomers have discovered an unusually massive, dense exoplanet that challenges conventional ideas about how rocky planets form.
Called GJ 523b, the exoplanet is about 2.5 times wider than Earth but packs roughly 23 times our planet's mass into that relatively compact size. Worlds this large and dense are sometimes referred to as "mega-Earths," an informal term for unusually massive, predominantly rocky planets. GJ 523b's high density suggests it contains relatively little atmosphere despite being large enough that astronomers would normally expect it to have accumulated a substantial gaseous envelope, according to a statement from the University of Wisconsin–Madison.
"This isn't what we expected at all," Max Kroft, lead author of the study, said in the statement. "Dense planets like this aren't uncommon, but they're usually small rocky planets similar to Earth or Mercury. This planet is two and a half times bigger than the Earth."
GJ 523b was initially identified as a candidate by NASA's Transiting Exoplanet Survey Satellite (TESS), which searches for periodic dips in starlight caused when planets cross, or transit, their host stars. Researchers followed up with observations from the ground-based WIYN 3.5-meter Telescope at Kitt Peak National Observatory in Arizona, using a spectrograph to measure the planet's gravitational tug on its star.
Combining those observations, the team calculated that GJ 523b has a mass about 23.5 times that of Earth, a radius 2.55 times larger and a density of about 126.82 grams per cubic inch. It circles its star every 17.75 days. The planetary system is also relatively young, at an estimated nearly 170 million years old, according to the study.
That combination of size, mass and youth poses a puzzle for planet formation models. Planets begin by building cores of rock and metal, which can then pull in hydrogen and helium from the disk of gas and dust surrounding a young star. In our own solar system, giant planets such as Jupiter and Saturn are thought to have begun rapidly accumulating their massive gaseous envelopes once their growing cores reached roughly 20 times Earth's mass.
GJ 523b is already about 23 times Earth's mass, putting it beyond that threshold. Yet instead of developing into a gas-rich world, its unusually high density suggests it has relatively little gas and remains predominantly rocky — raising the question of why it followed such a different path.
"The question is, why didn't this planet do that, if it's 20 times the size of Earth?" Kroft said in the statement.
One possibility is that GJ 523b initially formed with a thick atmosphere that was later stripped away. Another is that it formed through a collision between two planets, creating a larger rocky world while blasting much of their gaseous envelopes into space, according to the statement.
Astronomers have used the term "mega-Earth" for more than a decade to describe exceptionally massive rocky worlds, though it has never represented a formally established class of exoplanets. Finding more examples like GJ 523b could help reveal whether these unusual worlds are rare exceptions or part of a broader population.
"It's hard to infer things about planet formation in general from a sample size of one," Kroft said in the statement. "We're not going to get to 10,000 of these overdense planets, but if we can get to 20 or 30, maybe some trends might pop out."
The findings have been submitted to The Astronomical Journal and are currently available on the preprint server arXiv and have not yet been peer reviewed.
A rare planet-forming disk around a young triple-star system in the Orion constellation has been tipped over by a river of gas over 1 trillion miles (1.6 trillion kilometers) long. The discovery, made at radio wavelengths with ALMA, the Atacama Large Millimeter/submillimeter Array in Chile, could explain why astronomers keep finding planets with orbits that are drastically misaligned with the rotational axes of their stars.
GW Orionis is a triple system consisting of three pre-main sequence stars, meaning that they are still forming and contracting and have not yet initiated fusion reactions of hydrogen in their core. The stars are located roughly 1,300 light-years away, in the Lambda Orionis star-forming molecular ring in the constellation of Orion, the Hunter. Finding a planet-forming disk of gas and dust encircling all three stars in a system is very rare, and finding a disk consisting of three rings with misaligned orbits is even stranger.
"Previous studies of GW Orionis revealed that the system's inner, middle and outer rings are misaligned, with each ring tilted at a different angle," said Maria Galloway-Sprietsma, a PhD student at the University of Florida who led the research, in a statement.
The outer ring, which is one of the largest ever seen around a young star, is the most noticeably misaligned. It had previously been thought that an unseen gas giant planet, having carved out a gap between the middle and outer ring, was perturbing the outer ring.
Now though, Galloway-Sprietsma and colleagues have discovered the hidden truth: an enormous finger of gas reaching in from the surrounding molecular cloud is disturbing the outer ring, and the exchange of angular momentum, or rotational energy, between the two is warping the ring and tipping it over.
The disk around GW Orionis is composed of three rings, beginning at radii of 4.1, 17.4 and 31.6 billion miles (6.7, 28 and 51 billion kilometers/44, 187 and 340 astronomical units) from the center of the tight triple system.
The streamer of gas tilting the system's outer ring was discovered through new ALMA observations. Such streamers are thought to be how stars grow, delivering mass onto nascent suns. The streamer is composed mostly of molecular hydrogen, but since molecular hydrogen is invisible at radio wavelengths, ALMA searched for molecules of carbon monoxide in the streamer instead.
The length of the streamer is astounding, stretching 0.2 light years (12,600 astronomical units, 1.9 trillion kilometers or 1.2 trillion miles).
"When our team modeled the infall of this streamer, we found that the angle at which it impacts the disk is closely aligned with the outer ring," said Galloway-Sprietsma.
This superimposed image of of the GW Orionis star system shows images from the ALMA radio telescope (in blue) overlayed on the ESO Very Large Telescope's SPHERE instrument's view, which shows the shadow of the system's innermost ring. (Image credit: ESO/Exeter/Kraus et al., ALMA (ESO/NAOJ/NRAO))
It is believed that the streamer has already done most of the work in tipping over the outer ring of the disk. Today, its angular momentum, or spin, is less than that of the disk.
"In the past it likely had a greater angular momentum, and that allowed the disk to become misaligned," said Bae.
The discovery of the streamer might put to bed more than just the mystery of what tipped over GW Orionis' disk.
In our solar system, all the planets orbit around the sun in the ecliptic plane, which is a narrow plane aligned with the sun's equator and direction of rotation. Most exoplanets orbit their star in similar fashion, but astronomers have also previously discovered some planets that have highly inclined or even retrograde orbits around their star, as though some mighty force had tipped their orbits over. With the discovery of the GW Orionis streamer, astronomers may have found the nature of the force that creates these wonky planets.
"If these streamers are common, then we can naturally explain why planets may not necessarily end up in very orderly systems," said Bae in another statement. "They can have much more random orientations."
However, the team recognizes that such a conclusion is potentially a big leap based on discovering just one planet-forming disk being influenced in such a manner. So the plan is to find more.
"What we need next is a systematic survey of young stars to see how many have streamers and how many don't," said Galloway-Sprietsma. "That will tell us how important they are in shaping planetary systems."
Since the discovery of the first world beyond the solar system in the 1990s, astronomers have become adept at spotting extrasolar planets, or exoplanets. But while NASA's exoplanet catalog has burgeoned to over 6,000 confirmed entries, moons around these worlds, known as exomoons, have proved elusive.
In fact, we have failed to make a single confirmed discovery of an exomoon despite being certain that just as the planets of the solar system have their own natural satellites, worlds in other star systems must have them too.
Now, this controversial drought of exomoons may have become even more confusing and, frankly, weird. That is because while studying a strange star system called CD-35 2722 with the Very Large Telescope (VLT), astronomers have discovered an object that could be an exomoon, or it could be something that forces us to rethink our very definition of what a "moon" is and what a "planet" is.
The star CD-35 2722 is located around 73 light-years away and has around half the mass of the sun. It is orbited by a "failed star" or brown dwarf. These stellar bodies get their unfortunate nickname because they form like other stars but fail to gather enough mass to trigger the fusion of hydrogen to helium in their cores. In terms of mass, brown dwarfs are more massive than the largest gas giant planets, but smaller than the smallest stars, usually with around 13 to 80 times the mass of Jupiter, or around 0.013 to 0.08 times the mass of the sun.
The newly discovered object in CD-35 2722 is certainly moon-like, but rather than orbiting a planet as the moons in the solar system do, it orbits the system's brown dwarf.
"This system is somewhat hard to define using solar-system-based words like 'planet' and 'moon.' The exosatellite is clearly massive enough to be a planet, but it does not orbit a star, though it orbits an object that orbits a star," team leader Kevin Hoy of the Universidad Diego Portales and the Millennium Nucleus of Young Exoplanets and their Moons (YEMS) in Chile, said in a statement.
"Being the third wheel in this system makes us want to call it a moon, even if it is nothing like the small, rocky moons we have in our system."
The team's research was published on Wednesday (July 22) in the journal Nature.
Erm... It's definitely an exosatellite
The team currently isn't able to definitively claim this object in CD-35 2722 is an exomoon, because that would require really nailing down a new definition of what a moon is.
"The satellite we report is a giant gaseous body orbiting a highly massive companion, itself several times the mass of Jupiter. We have a clear delineation between the planets and the sun in the solar system, so defining things like moons is simple," team member Alice Zurlo of the Universidad Diego Portales said. "In the CD-35 2722 system, where we are blurring the lines between stars, planets, and moons, the whole thing becomes more complicated to describe."
Zurlo and colleagues can, however, confidently claim this is an exosatellite, meaning it is a first-of-its-kind detection no matter what the future holds for its classification.
The Extremely Large Telescope (ELT), currently under construction in Chile, could be integral in the hunt for exomoons and exosatellites. (Image credit: ESO/G. Vecchia)
It is hoped that the Extremely Large Telescope (ELT) currently under construction in Chile, will make a massive impact in the hunt for exomoons, and now, other exosatellites.
Until these objects begin to be uncovered, one thing this discovery re-emphasizes is something that astronomers have been gleefully discovering ever since the first exoplanet was spotted: planetary systems come in a variety of diverse, weird and wonderful forms.
