The planet is close to its star at a distance of 1.5 million miles. Credit: NASA and G.
More than 4,000 worlds have been found around stars thousands of light years away from Earth. There are many extrasolar planets, from rocky super-Earths to Neptunes.
Hot Jupiters, massive balls of gas that are about the size of our own Jovian planet but that are zinging around their stars in less than 10 days, are among the more puzzling planets discovered to date. About 400 hot Jupiters have been discovered by scientists. One of the biggest mysteries in planetary science is how these whirlers came to be.
Astronomers have discovered a gas giant that is five times Jupiter's mass and can be seen in 16 hours. The shortest of any gas giant to date is the planet's circle.
The planet's day side is thought to be around 6,000 degrees Fahrenheit, or about as hot as a small star, due to its extremely tight and close proximity to its star. The planet, designated TOI-2109b, is the second hottest detected so far.
Astronomers think that TOI-2109b is in the process of "orbital decay", like a bathwater circling the drain. It is predicted that the planet will spiral toward its star faster than other hot Jupiters.
The MIT-led TESS mission made the discovery, and it presents a unique opportunity for astronomy to study how planets behave as they are drawn in and swallowed by their star.
Ian Wong, the lead author of the discovery, says that in one or two years, they may be able to detect how the planet moves closer to its star. We will not see the planet fall into its star. This planet might not be there for another 10 million years.
The work of a large collaboration that included members of MIT's TESS science team and researchers from around the world resulted in the discovery.
The track is transit.
On May 13, 2020, NASA's TESS satellite began observing TOI-2109, a star located in the southern portion of the Hercules constellation. The 2,109th "TESS Object of Interest" was identified by the mission as a star that might host an object in the solar system.
The TESS science team analyzed the star's light for dips in its light that might indicate a planet passing in front of it. TESS confirmed that the star hosts an object that transits about 16 hours a day.
After the team notified the astronomy community, a number of ground-based telescopes followed up over the next year to observe the star more closely over a range of frequencies. The transiting object was confirmed to be a planet by these observations and TESS' initial detection.
"We realized we had something very interesting and relatively rare when we realized everything was consistent with it being a planet," says Shporer.
Day and night.
The team determined that TOI-2109b is five times as big as Jupiter and 35 percent larger, and is very close to its star, at a distance of 1.5 million miles. Mercury is around 36 million miles from the Sun.
The star of the planet is 50 percent larger than the Sun. The researchers estimated that TOI-2109b is going into its star at a rate of 10 to 750 milliseconds per year.
The researchers determined that TOI-2109b was an ultrahot Jupiter, with the shortest path of any known gas giant. Like most hot Jupiters, the planet appears to be locked in place with a constant day and night side. The team was able to observe the planet's brightness as it revolves around its axis. The researchers estimated that the day side of the planet reaches temperatures of more than 3,300 Kelvin by observing it behind its star.
Shporer says that the planet's night side brightness is below the sensitivity of the TESS data, which raises questions about what is really happening there. Is the temperature very cold or does the planet take heat on the day side and transfer it to the night side? We are at the beginning of trying to answer this question.
The researchers hope to observe TOI-2109b with more powerful tools in the future, including the Hubble Space Telescope. As hot Jupiters fall into their star, more detailed observations could illuminate the conditions.
Wong says that TOI-2109b is the most extreme subclass of exoplanet. Some of the unique physical and chemical processes that occur in their atmospheres have no parallels in our own solar system.
Future observations of TOI-2109b may reveal clues to how the systems come to be. "From the beginning of exoplanetary science, hot Jupiters have been seen as weird," Shporer says. How does a planet of Jupiter's size get to an around-the-world location in a few days? We don't have anything like this in our solar system, and we see this as an opportunity to study them and explain their existence.
Ian Wong and his colleagues wrote about an Ultrahot Gas Giant on a 16 hour time period. There is a DOI: 10.847/1538-3881/ac26bd.
The journal has information about astronomy.
A year on this giant, hot planet is just 16 hours long.
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