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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Knowing whether or not a planet elsewhere in the galaxy could potentially be habitable requires knowing a lot about that planet’s sun. Sarah Peacock relies on computer models to assess stars’ radiation, which can have a major influence on whether or not one of these exoplanets has breathable atmosphere.
Name: Sarah Peacock
Title: Assistant Research Scientist
Formal Job Classification: Astrophysicist
Organization: Exoplanets and Stellar Astrophysics Laboratory, Astrophysics Division, Science Directorate (Code 667)
Sarah Peacock is a research scientist with the Exoplanets and Stellar Astrophysics Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md.Courtesy of Sarah Peacock What do you do and what is most interesting about your role here at Goddard?
My overarching research goal is to find habitable planets in other solar systems. To do this, I study the high-energy radiation that specific stars produce to help determine if life can exist on any earthlike planets that orbit them.
What is your educational background?
In 2013, I received a Bachelor of Arts in astrophysics from the University of Virginia. I received both my master’s and doctorate degrees from the Lunar and Planetary Laboratory at the University of Arizona in 2016 and 2019, respectively.
What drew you to study the stars?
In high school, I took an astronomy class. We had a planetarium in our school and I had a wonderful teacher who inspired me to fall in love with the stars. She also showed us how many of the Harry Potter characters are drawn from the constellations and that spoke to my heart because I am a Harry Potter fan!
How did you come to Goddard?
I started at Goddard as a NASA post-doctoral fellow in July 2020, but I first saw the center the day before Goddard shut down due to COVID.
How does high-energy radiation show you what planets outside our solar system might be habitable?
High-energy radiation can cause a planet to lose its atmosphere. If a planet is exposed to too much high-energy radiation, the atmosphere can be blown off, and if there is no atmosphere, then there is nothing for life as we know it to breathe.
We cannot directly measure the specific radiation that I study, so we have to model it. The universe has so many stars, and almost all stars host a planet. There are approximately 5,500 confirmed exoplanets so far, with an additional 7,500 unconfirmed exoplanets.
I help identify systems that either have too much radiation, so planets in the habitable zone (the region around a star where liquid water could exist on a planet’s surface) are probably lifeless, or systems that have radiation levels that are safer. Ultimately, my research helps narrow down the most likely systems to host planets that should have stable atmospheres.
Sarah Peacock research goal is to find habitable planets in other solar systems.Courtesy of Sarah Peacock Where does your data come from?
I predominately use data from the Hubble Space Telescope and from the now-retired spacecraft GALEX. My work itself is more theory-focused though: I create a modeled stellar spectrum across all wavelengths and use observations to validate my modeling.
What other areas of research are you involved in?
I am working with a team analyzing data from the James Webb Space Telescope to see if earthlike planets around M-type stars (a star that is cooler and smaller than the Sun) have atmospheres and, if so, what the composition of those atmospheres is. An exciting result from this work is that we may have detected water in the atmosphere of a rocky planet for the first time ever. However, we cannot yet distinguish with our current observations if that water comes from the planet or from spots on the star (starspots on this host star are cold enough for water to exist in gas form).
I am also helping manage a NASA Innovative Advance Concept (NIAC) study led by my mentor, Ken Carpenter, to work on the Artemis Enabled Stellar Imager (AeSI). If selected for further development, this imager would be an ultraviolet/optical interferometer located on the South Pole of the Moon. With this telescope, we would be able to map the surface of stars, image accretion disks, and image the centers of Active Galactic Nuclei.
As a relatively new employee to Goddard, what have been your first impressions?
Everyone who I have met, especially those in my lab, are incredibly friendly and welcoming. Starting during the pandemic, I was worried about feeling isolated, but instead, I was blown away by how many folks in my lab reached out to set up calls to introduce themselves and suggest opportunities for collaboration. It made me feel welcome.
Who is your mentor and what did your mentor advise you?
Ken Carpenter is my mentor. He encourages me to pursue my aspirations. He supports letting me chart my own path and being exposed to many different areas of research. I thank Ken for his support and encouragement and for including me on his projects.
“Everyone who I have met, especially those in my lab, are incredibly friendly and welcoming.”Courtesy of Sarah Peacock What do you do for fun?
I am a new mom, so my usual hobbies are on pause! Right now, fun is taking care of my baby and introducing life experiences to him.
As a recently selected member of the Executive Committee for NASA’s Exoplanet Exploration Program Analysis Group (ExoPAG), what are your responsibilities?
The NASA ExoPAG is responsible for soliciting and coordinating scientific community input into the development and execution of NASA’s exoplanet exploration program. We solicit opinions and advice from any scientist who studies exoplanets. We are a bridge between NASA’s exoplanet scientists and NASA Headquarters in Washington.
What is a fun fact about yourself?
I got married the same day I defended my Ph.D. I had my defense in the morning and got married in the afternoon at the courthouse.
Who is your favorite author?
I love to read; I always have three books going. My favorite author is Louise Penny, who writes mysteries, but I read all genres. Right now, I am reading a biography about Marjorie Merriweather Post.
What is your favorite quote?
“The most that can be expected from any model is that it can supply a useful approximation to reality: All models are wrong; some models are useful.” —Box and Draper 1987
By Elizabeth M. Jarrell
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Conversations With Goddard is a collection of Q&A profiles highlighting the breadth and depth of NASA’s Goddard Space Flight Center’s talented and diverse workforce. The Conversations have been published twice a month on average since May 2011. Read past editions on Goddard’s “Our People” webpage.
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Last Updated Dec 10, 2024 Related Terms
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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).
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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.
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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.
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