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Newly Discovered Extreme “Ultrahot Jupiter” Flies Around Its Star – One Year Only Lasts 16 Hours

By on November 26, 2021 0

The newly discovered planet is relatively close to its star, at a distance of only about 1.5 million kilometers. Credit: NASA, ESA and G. Bacon

An “ultrahot Jupiter“has the shortest orbit of all known gas giants.

The hunt for planets beyond our solar system has revealed more than 4,000 distant worlds, orbiting stars thousands of light years from Earth. These extrasolar planets are a veritable menagerie, rocky super-Earths and miniature Neptunes with colossal gas giants.

Among the most puzzling planets discovered to date are the “Hot Jupiters” – massive balls of gas that are about the size of our own Jovian planet but which orbit their stars in less than 10 days, unlike the Jupiter’s 12-year orbit. . Scientists have discovered around 400 hot Jupiters so far. But exactly how these whirlwinds of weight came about remains one of the biggest unsolved mysteries in planetary science.

Now, astronomers have discovered one of the most extreme ultralight Jupiters – a gas giant that’s about five times the mass of Jupiter and revolves around its star in just 16 hours. The planet’s orbit is the shortest of all the gas giants known to date.

Due to its extremely narrow orbit and proximity to its star, the planet’s day side is estimated to be around 3,500 Kelvin, or nearly 6,000 degrees. Fahrenheit – about as hot as a small star. This makes the planet, designated TOI-2109b, the second hottest detected to date.

Hot exoplanet Jupiter

An artist’s illustration of a hot Jupiter orbiting near its host star. Credit: NASA, ESA and L. Hustak (STScI)

Judging by its properties, astronomers believe TOI-2109b is “disintegrating” or spiraling into its star, like bathwater circling the drain. Its extremely short orbit is expected to cause the planet to spiral toward its star faster than other hot Jupiters.

The discovery, which was made initially by ">NasaSatellite for the study of exoplanets in transit (TRIAL), a MIT-driven, presents a unique opportunity for astronomers to study how planets behave when attracted and swallowed by their star.

“In a year or two, if we’re lucky, we might be able to detect how the planet is approaching its star,” says Ian Wong, lead author of the discovery, who was a post-doctoral fellow at MIT during the study and has since transferred to NASA’s Goddard Space Flight Center. “In our lifetime, we will not see the planet fall into its star. But give it another 10 million years, and this planet might not be there.

The discovery was reported on November 23, 2021, in the Astronomical Journal and is the result of the work of a large collaboration that included members of MIT’s TESS science team and researchers from around the world.

Transit lane

On May 13, 2020, NASA’s TESS satellite began observing TOI-2109, a star located in the southern part of the constellation of Hercules, about 855 light years from Earth. The star was identified by the mission as the 2,109th “TESS object of interest” for the possibility that it could host an orbiting planet.

For nearly a month, the spacecraft collected measurements of the star’s light, which the TESS science team then analyzed for transits – periodic drops in starlight that could indicate a passing planet. ahead and briefly blocking a small fraction of the star’s light. TESS data confirmed that the star indeed hosts an object that transits approximately every 16 hours.

TOI-2109 Starlight

Starlight from TOI-2109 measured by TESS, showing periodic drops in brightness due to the planet in transit occurring every 16 hours. Credit: Courtesy of the researchers

The team briefed the wider astronomical community, and soon after, several ground-based telescopes followed up over the next year to observe the star more closely over a range of frequency bands. These observations, combined with the initial detection of TESS, confirmed the transiting object as an orbiting planet, which was designated TOI-2109b.

It was all consistent with the fact that it was a planet, and we realized that we had something very interesting and relatively rare, ”says study co-author Avi Shporer, researcher at MIT’s Kavli Institute for Astrophysics and Space Research.

Day and night

By analyzing measurements at various optical and infrared wavelengths, the team determined that TOI-2109b is about five times as massive as Jupiter, about 35% larger and extremely close to its star, at a distance of about 1.5 million kilometers. Mercury, by comparison, is about 36 million kilometers from the Sun.

The planet’s star is about 50% larger in size and mass than our Sun. From the observed properties of the system, the researchers estimated that TOI-2109b was heading towards its star at a speed of 10 to 750 milliseconds per year, faster than any hot Jupiter ever observed.

Given the dimensions of the planet and its proximity to its star, the researchers determined that TOI-2109b was an ultra hot Jupiter, with the shortest orbit of all known gas giants. Like most hot Jupiters, the planet appears locked in by the tides, with a perpetual day and night side, similar to the Moon in relation to Earth. From the month-long TESS observations, the team was able to observe the planet’s varying luminosity as it rotates around its axis. Watching the planet pass behind its star (called a secondary eclipse) at optical and infrared wavelengths, the researchers estimated that the day side reached temperatures of over 3,500 Kelvin.

“Meanwhile, the brightness on the night side of the planet is lower than the sensitivity of the TESS data, which raises questions about what is really going on there,” says Shporer. “Is the temperature there very cold or does the planet take heat from the day side and transfer it to the night side?” We’re at the start of trying to answer this question for those super-hot Jupiters.

Researchers hope to observe TOI-2109b with more powerful tools in the near future, including the The Hubble Space Telescope and the imminent launch James Webb Space Telescope. More detailed observations could shed light on the conditions hot Jupiters experience when they fall into their star.

“Ultra-hot Jupiters such as TOI-2109b are the most extreme subclass of exoplanet“Says Wong.” We have only just started to understand some of the unique physical and chemical processes that occur in their atmospheres – processes that have no analogues in our own solar system.

Future observations of TOI-2109b could also reveal clues as to how such dizzying systems first appeared. “Since the beginning of exoplanetary science, hot Jupiters have been considered eccentrics,” says Shporer. “How does a planet as massive and large as Jupiter reach an orbit that lasts only a few days?” We don’t have anything like it in our solar system, and we see this as an opportunity to study them and help explain their existence.

Reference: “TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit” by Ian Wong, Avi Shporer, George Zhou, Daniel Kitzmann, Thaddeus D. Komacek, Xianyu Tan, René Tronsgaard, Lars A. Buchhave, Shreyas Vissapragada, Michael Greklek-McKeon, Joseph E. Rodriguez, John P. Ahlers, Samuel N. Quinn, Elise Furlan, Steve B. Howell, Allyson Bieryla, Kevin Heng, Heather A. Knutson, Karen A. Collins, Kim K. McLeod, Perry Berlind , Peyton Brown, Michael L. Calkins, Jerome P. de Leon, Emma Esparza-Borges, Gilbert A. Esquerdo, Akihiko Fukui, Tianjun Gan, Eric Girardin, Crystal L. Gnilka, Masahiro Ikoma, Eric LN Jensen, John Kielkopf, Takanori Kodama, Seiya Kurita, Kathryn V. Lester, Pablo Lewin, Giuseppe Marino, Felipe Murgas, Norio Narita, Enric Pallé, Richard P. Schwarz, Keivan G. Stassun, Motohide Tamura, Noriharu Watanabe, Björn Benneke, George R. Ricker, David W. Latham, Roland Vanderspek, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Douglas A. Caldwell, William Fong, Chelsea X. Huang, Ismael Mirel es, Jo shua E. Schlieder, Bernie Shiao and Jesus Noel Villaseñor, November 23, 2021, Astronomical Journal.
DOI: 10.3847 / 1538-3881 / ac26bd

This research was supported, in part, by NASA.