Members Can Post Anonymously On This Site
-
Similar Topics
-
By NASA
Artist’s concept depicts new research that has expanded our understanding of exoplanet WASP-69 b’s “tail.” NASA/JPL-Caltech/R. Hurt (IPAC) The Planet
WASP-69 b
The Discovery
The exoplanet WASP-69 b has a “tail,” leaving a trail of gas in its wake.
Key Takeaway
WASP-69 b is slowly losing its atmosphere as light hydrogen and helium particles in the planet’s outer atmosphere escape the planet over time. But those gas particles don’t escape evenly around the planet, instead they are swept into a tail of gas by the stellar wind coming from the planet’s star.
Details
Hot Jupiters like WASP-69 b are super-hot gas giants orbiting their host stars closely. When radiation coming from a star heats up a planet’s outer atmosphere, the planet can experience photoevaporation, a process in which lightweight gases like hydrogen and helium are heated by this radiation and launched outward into space. Essentially, WASP-69 b’s star strips gas from the planet’s outer atmosphere over time.
What’s more, something called the stellar wind can shape this escaping gas into an exoplanetary tail.
The stellar wind is a continuous stream of charged particles that flow outwards into space from a star’s outer atmosphere, or corona. On Earth, the Sun’s stellar wind interacts with our planet’s magnetic field which can create beautiful auroras like the Northern Lights.
On WASP-69 b, the stellar wind coming from its host star actually shapes the gas escaping from the planet’s outer atmosphere. So, instead of gas just escaping evenly around the planet, “strong stellar winds can sculpt that outflow in tails that trail behind the planet,” said lead author Dakotah Tyler, an astrophysicist at the University of California, Los Angeles, likening this gaseous tail to a comet’s tail.
Because this tail is created by the stellar wind, however, that means it’s subject to change.
“If the stellar wind were to taper down, then you could imagine that the planet is still losing some of its atmosphere, but it just isn’t getting shaped into the tail,” Tyler said, adding that, without the stellar wind, that gas escaping on all sides of the planet would be spherical and symmetrical. “But if you crank up the stellar wind, that atmosphere then gets sculpted into a tail.”
Tyler likened the process to a windsock blowing in the breeze, with the sock forming a more structured shape when the wind picks up and it fills with air.
The tail that Tyler and his research team observed on WASP-69 b extended more than 7.5 times the radius of the planet, or over 350,000 miles. But it’s possible that the tail is even longer. The team had to end observations with the telescope before the tail’s signal disappeared, so this measurement is a lower limit on the tail’s true length at the time.
However, keep in mind that because the tail is influenced by the stellar wind, changes in the stellar wind could change the tail’s size and shape over time. Additionally changes in the stellar wind influence the tail’s size and shape, but since the tail is visible when illuminated by starlight, changes in stellar activity can also affect tail observations.
Exoplanet tails are still a bit mysterious, especially because they are subject to change. The study of exoplanet tails could help scientists to better understand how these tails form as well as the ever-changing relationship between the stellar and planetary atmospheres. Additionally, because these exoplanetary tails are shaped by stellar activity, they could serve as indicators of stellar behavior over time. This could be helpful for scientists as they seek to learn more about the stellar winds of stars other than the star we know the most about, our very own Sun.
Fun Facts
WASP-69 b is losing a lot of gas — about 200,000 tons per second. But it’s losing this gaseous atmosphere very slowly — so slowly in fact that there is no danger of the planet being totally stripped or disappearing. In general, every billion years, the planet is losing an amount of material that equals the mass of planet Earth.
The solar system that WASP-69 b inhabits is about 7 billion years old, so even though the rate of atmosphere loss will vary over time, you might estimate that this planet has lost the equivalent of seven Earths (in mass) of gas over that period.
The Discoverers
A team of scientists led by Dakotah Tyler of the University of California, Los Angeles published a paper in January, 2024 on their discovery, “WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 Rp,” in the journal, “The Astrophysical Journal.” The observations described in this paper were made by Keck/NIRSPEC (NIRSPEC is a spectrograph designed for Keck II).
View the full article
-
By NASA
Artist’s concept of “hot Neptune” TOI-3261 b. NASA/JPL-Caltech/K. Miller (Caltech/IPAC) By Grace Jacobs Corban
The Discovery
A Neptune-sized planet, TOI-3261 b, makes a scorchingly close orbit around its host star. Only the fourth object of its kind ever found, the planet could reveal clues as to how planets such as these form.
Key Facts
An international team of scientists used the NASA space telescope, TESS (the Transiting Exoplanet Survey Satellite), to discover the exoplanet (a planet outside our solar system), then made further observations with ground-based telescopes in Australia, Chile, and South Africa. The measurements placed the new planet squarely in the “hot Neptune desert” – a category of planets with so few members that their scarcity evokes a deserted landscape. This variety of exoplanet is similar to our own Neptune in size and composition, but orbits extremely closely to its star. In this case, a “year” on TOI-3261 b is only 21 hours long. Such a tight orbit earns this planet its place in an exclusive group with, so far, only three other members: ultra-short-period hot Neptunes whose masses have been precisely measured.
Details
Planet TOI-3261 b proves to be an ideal candidate to test new computer models of planet formation. Part of the reason hot Neptunes are so rare is that it is difficult to retain a thick gaseous atmosphere so close to a star. Stars are massive, and so exert a large gravitational force on the things around them, which can strip the layers of gas surrounding a nearby planet. They also emit huge amounts of energy, which blow the gas layers away. Both of these factors mean that hot Neptunes such as TOI-3261 b might have started out as much larger, Jupiter-sized planets, and have since lost a large portion of their mass.
By modeling different starting points and development scenarios, the science team determined that the star and planet system is about 6.5 billion years old, and that the planet started out as a much larger gas giant. It likely lost mass, however, in two ways: photoevaporation, when energy from the star causes gas particles to dissipate, and tidal stripping, when the gravitational force from the star strips layers of gas from the planet. The planet also might have formed farther away from its star, where both of these effects would be less intense, allowing it to retain its atmosphere.
The remaining atmosphere of the planet, one of its most interesting features, will likely invite further atmospheric analysis, perhaps helping to unravel the formation history of this denizen of the “hot Neptune desert.” Planet TOI-3261 b is about twice as dense as Neptune, indicating that the lighter parts of its atmosphere have been stripped away over time, leaving only the heavier components. This shows that the planet must have started out with a variety of different elements in its atmosphere, but at this stage, it is hard to tell exactly what. This mystery could be solved by observing the planet in infrared light, perhaps using NASA’s James Webb Space Telescope – an ideal way to see the identifying fingerprints of the different molecules in the planet’s atmosphere. This will not just help astronomers understand the past of TOI-3261 b, but also begin to uncover the physical processes behind all hot, giant planets.
Fun Facts
The first-ever discovery of an ultra-short-period hot Neptune, LTT-9779 b, came in 2020. Since then, TESS discoveries TOI-849 b and TOI-332 b have also joined the elite ultra-short-period hot-Neptune club (with masses that have been precisely measured). Both LTT-9779 b and TOI-849 b are in the queue for infrared observations with the James Webb Space Telescope, potentially broadening our understanding of these planets’ atmospheres in the coming years.
The Discoverers
An international science team led by astronomer Emma Nabbie of the University of Southern Queensland published their paper on the discovery, “Surviving in the Hot Neptune Desert: The Discovery of the Ultrahot Neptune TOI-3261 b,” in The Astronomical Journal in August 2024.
View the full article
-
By NASA
Artist’s concept of a young, newly discovered planet, exposed to observation by a warped debris disk. Credit: Robert Hurt, Caltech-IPAC. The discovery
A huge planet with a long name – IRAS 04125+2902 b – is really just a baby: only 3 million years old. And because such infant worlds are usually hidden inside obscuring disks of debris, it is the youngest planet so far discovered using the dominant method of planet detection.
Key facts
The massive planet, likely still glowing from the heat of its formation, lies in the Taurus Molecular Cloud, an active stellar nursery with hundreds of newborn stars some 430 light-years away. The cloud’s relative closeness makes it a prime target for astronomers. But while the cloud offers deep insight into the formation and evolution of young stars, their planets are usually a closed book to telescopes like TESS, the Transiting Exoplanet Survey Satellite. These telescopes rely on the “transit method,” watching for the slight dip in starlight when a planet crosses the face of its host star. But such planetary systems must be edge-on, from Earth’s vantage point, for the transit method to work. Very young star systems are surrounded by disks of debris, however, blocking our view of any potentially transiting planets.
A research team has just reported an extraordinary stroke of luck. Somehow, the outer debris disk surrounding this newborn planet, IRAS 04125+2902 b, has been sharply warped, exposing the baby world to extensive transit observations by TESS.
Details
While the warped outer disk is a great coincidence, it’s also a great mystery. Possible explanations include a migration of the planet itself, moving closer to the star and, in the process, diverging from the orientation of the outer disk – so that, from Earth, the planet’s orbit is edge-on, crossing the face of the star, but the outer disk remains nearly face-on to us. One problem with this idea: Moving a planet so far out of alignment with its parent disk would likely require another (very large) object in this system. None has been detected so far.
The system’s sun happens to have a distant stellar companion, also a possible culprit in the warping of the outer disk. The angle of the orbit of the companion star, however, matches that of the planet and its parent star. Stars and planets tend to take the gravitational path of least resistance, so such an arrangement should push the disk into a closer alignment with the rest of the system – not into a radical departure.
Another way to get a “broken” outer disk, the study authors say, would not involve a companion star at all. Stellar nurseries like the Taurus Molecular Cloud can be densely packed, busy places. Computer simulations show that rains of infalling material from the surrounding star-forming region could be the cause of disk-warping. Neither simulations nor observations have so far settled the question of whether warped or broken disks are common or rare in such regions.
Fun facts
Combining TESS’s transit measurements with another way of observing planets yields more information about the planet itself. We might call this second approach the “wobble” method. The gravity of a planet tugs its star one way, then another, as the orbiting planet makes its way around the star. And that wobble can be detected by changes in the light from the star, picked up by specialized instruments on Earth. Such “radial velocity” measurements of this planet reveal that its mass, or heft, amounts to no more than about a third of our own Jupiter. But the transit data shows the planet’s diameter is about the same. That means the planet has a comparatively low density and, likely, an inflated atmosphere. So this world probably is not a gas giant like Jupiter. Instead, it could well be a planet whose atmosphere will shrink over time. When it finally settles down, it could become a gaseous “mini-Neptune” or even a rocky “super-Earth.” These are the two most common planet types in our galaxy – despite the fact that neither type can be found in our solar system.
The discoverers
A science team led by astronomer Madyson G. Barber of the University of North Carolina at Chapel Hill published the study, “A giant planet transiting a 3 Myr protostar with a misaligned disk,” in the journal Nature in November 2024.
View the full article
-
-
By NASA
NASA/Jim Grossmann In this photo from Aug. 7, 2009, Jose Hernandez, mission specialist, smiles at the camera as he waits for his turn to enter the space shuttle Discovery as part of STS-128. It was the 128th Shuttle mission and the 30th mission to the International Space Station. While at the orbital lab, the STS-128 crew conducted three spacewalks.
Hernandez joined NASA’s Johnson Space Center in Houston in 2001. There, he was a materials research engineer in the Materials & Processes branch; eventually, he became branch chief. In 2004, he was selected as an astronaut candidate, and in 2009, he became a crew member of STS-128.
Get to know some of our Hispanic colleagues, past and present, during Hispanic Heritage Month.
Image credit: NASA/Jim Grossmann
View the full article
-
-
Check out these Videos
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.