Scientists have discovered the fastest orbiting ultra-hot Jupiter that takes just 16 hours to complete a full orbit around its star.
The newly discovered planet, which has been named TOI-2109b, is massive as it is about 1.35 times larger than Jupiter and around 5 times its mass. It is located about 855 light-years away from us. It is orbiting a yellow-white star that is approximately 1.7 times larger than our sun with about 1.4 times its mass.
TOI-2109b is located so close to its star that it is probably tidally locked with only one side of the planet facing it at all times – it is only about 2.4 million kilometers (1.5 million miles) away from the star or 1.6% of the distance that Earth is from the sun. It has been estimated that the side that is constantly facing the star would have a jaw-dropping temperature of about 3,500 Kelvin (5,840 degrees Fahrenheit or 3,227 degrees Celsius) – this makes it the second-hottest exoplanet that has ever been found.
As for the night side, that remains a mystery as stated by Avi Shporer who is an astrophysicist at MIT's Kavli Institute for Astrophysics and Space Research, “The planet's night side brightness is below the sensitivity of the TESS data, which raises questions about what is really happening there,” adding, “Is the temperature there very cold, or does the planet somehow take heat on the day side and transfer it to the night side?”
The fact that the planet completes a full orbit around its star in just 16 hours is absolutely incredible, making it the closest orbiting gas giant that has ever been detected. It does, however, mean bad news for the future of the planet as described by astronomer Ian Wong from 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 might not be there.”
Actually, TOI-2109b is the planet closest to its death by orbital decay that has ever been observed. It moves between 10 and 750 milliseconds closer to its star every year which is the fastest rate by any hot Jupiter that has been found so far. “Ultrahot Jupiters such as TOI-2109b constitute the most extreme subclass of exoplanet,” Wong added.
Hot Jupiters are a mystery as gas giants can’t form that close to their host stars which suggests that they formed further away and traveled inwards over time. “From the beginning of exoplanetary science, hot Jupiters have been seen as oddballs,” Shporer noted. “How does a planet as massive and large as Jupiter reach an orbit that is only a few days long? We don't have anything like this in our Solar System, and we see this as an opportunity to study them and help explain their existence.”
Their study was published in The Astronomical Journal.