A newly discovered “ultrahot JupiterHas the shortest trajectory of any known gas giant.
The hunt for planets outside our solar system has shown more than 4,000 distant worlds orbiting stars thousands of light-years from Earth. These extrasolar planets are a true menagerie, from rock-filled super-Earths and miniature Neptunes to colossal gas giants.
Among the more confusing planets discovered to date are “hot Jupiters” – massive spheres of gas that are about the size of our own Jovian planet, but which orbit their stars in less than 10 days, as opposed to Jupiter’s 12-year orbit. . Scientists have discovered about 400 hot Jupiters to date. But exactly how these weighty vortices came to be remains one of the greatest unsolved mysteries in planetary science.
Now astronomers have discovered one of the most extreme ultra-hot Jupiters – a gas giant that is about five times the mass of Jupiter and blows around its star in just 16 hours. The planet’s orbit is the shortest of any known gas giant 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 close to 6,000 degrees Fahrenheit – about as hot as a small star. This makes the planet, designated TOI-2109b, the second hottest found so far.
Judging by its properties, astronomers believe that the TOI-2109b is in the process of “orbital decay” or spiraling into its star, like bathing water orbiting 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 initially made by NASA‘s Transiting Exoplanet Survey Satellite (TESS), en WITH-leaded mission, provides a unique opportunity for astronomers to study how planets behave when they are drawn in and swallowed by their star.
“In a year or two, if we’m lucky, we may discover how the planet moves closer to its star,” said Ian Wong, lead author of the discovery, who was a postdoc at MIT during the study and has since moved to NASA 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 may not be there.”
The discovery was reported on November 23, 2021 in Astronomical Journal and is the result of the work of a major collaboration that included members of MIT’s TESS science team and researchers from around the world.
On May 13, 2020, NASA’s TESS satellite began observing TOI-2109, a star located in the southern part of the Hercules constellation, about 855 light-years from Earth. The star was identified by the mission as the 2,109. “TESS object of interest”, for the possibility that it could host a planet in orbit.
Over the course of almost a month, the spacecraft collected measurements of star light, which the TESS science team then analyzed for transits – periodic dives into star light that could indicate a planet passing in front and briefly blocking a small fraction of the star’s light. The data from TESS confirmed that the star actually hosts an object that passes around every 16 hours.
The team informed the wider astronomical community, and shortly thereafter, several ground-based telescopes followed up over the next year to observe the star more closely across a series of frequency bands. These observations, combined with TESS’s first detection, confirmed the transiting object as an orbiting planet, designated TOI-2109b.
“Everything agreed that it was a planet, and we realized that we had something very interesting and relatively rare, ”says study co-author Avi Shporer, a researcher at MIT’s Kavli Institute for Astrophysics and Space Research.
Day and night
By analyzing measurements over various optical and infrared wavelengths, the team determined that the TOI-2109b is about five times as massive as Jupiter, about 35 percent larger and extremely close to its star, at a distance of about 1.5 million miles out. Mercury, by comparison, is about 36 million miles from the Sun.
The planet’s star is about 50 percent larger in size and mass compared to our sun. Based on the observed properties of the system, the researchers estimated that the TOI-2109b spirals into its star at a speed of 10 to 750 milliseconds per year – faster than any hot Jupiter yet observed.
Given the planet’s dimensions and proximity to its star, scientists determined the TOI-2109b to be an ultra-hot Jupiter, with the shortest orbit of any known gas giant. Like most hot Jupiters, the planet appears to be tidal locked with an eternal day and night side that resembles the Moon in terms of Earth. From the month-long TESS observations, the team was able to see the planet’s varying brightness as it rotated about its axis. By observing the planet passing behind its star (known as a secondary eclipse) at both optical and infrared wavelengths, the scientists estimated that the day side reaches temperatures of more than 3,500 Kelvin.
“Meanwhile, the planet’s brightness on the night side is below the sensitivity of the TESS data, raising questions about what’s really going on there,” says Shporer. “Is the temperature there very cold, or does the planet somehow take heat on the day side and transfer it to the night side? We are at the beginning of trying to answer this question for these ultra-hot Jupiters.”
Researchers hope to observe TOI-2109b with more powerful tools in the near future, including The Hubble Space Telescope and it soon launched James Webb Space Telescope. More detailed observations could illuminate the conditions that hot Jupiters undergo when they fall into their star.
Ultrahot Jupiters such as the TOI-2109b constitute the most extreme subclass of exoplanet“We are just beginning 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,” says Wong.
Future observations of the TOI-2109b may also reveal clues as to how such dizzying systems are going to be in the first place. “From the beginning of exoplanetary science, hot Jupiters have been seen as strange spheres,” says Shporer. “How does a planet as massive and large as Jupiter reach an orbit that is only a few days long? We have nothing 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 Mireles, J o shua E. Schlieder, Bernie Shiao and Jesus Noel Villaseñor, 23 November 2021, Astronomical Journal.
DOI: 10.3847 / 1538-3881 / ac26bd
This research was partially supported by NASA.