Astronomers Discover a New Ultra-Hot Jupiter

Astronomers have detected an ultra-hot Jupiter and it is definitely scorching. The team of international astronomers found the exoplanet with the help of NASA's Transiting Exoplanet Survey Satellite (TESS). They found the planet while they were watching a bright star named TOI-1518 and that’s when they noticed a transit signal meaning that there was a planet nearby and they confirmed it with high-resolution observations from the EXtreme PREcision Spectrometer (EXPRES) on the Lowell Observatory Discovery Channel Telescope (DCT).

Named TOI-1518b, the planet is almost twice as big as Jupiter (1.875 times its radius) and has a mass estimated to not be any more than 2.3 times that of our Solar System’s Gas Giant. “Hot Jupiters” are similar to the Gas Giant, except that their orbital periods last less than ten days. In fact, TOI-1518b completes a full orbit around its host star in just 1.9 Earth days at a distance of almost 0.04 AU away (one astronomical unit is the distance that Earth is from the sun; therefore, TOI-1518b is extremely close to its star).

And since “hot Jupiters” orbit their stars at such a close range, their surface temperatures are exceptionally hot. TOI-1518b, however, is so hot that it has been categorized as an “ultra-hot Jupiter”. It has an equilibrium temperature of 2,492 Kelvin (4,026 degrees Fahrenheit or 2,219 degrees Celsius) and a dayside brightness temperature of 3,237 Kelvin (5,367 degrees Fahrenheit or 2,964 degrees Celsius). Now that’s hot!

Additionally, it has a very misaligned orbit of 240.34 degrees. This is because the planet orbits so close to its star which has a temperature of about 7,300 Kelvin (12,681 degrees Fahrenheit or 7,027 degrees Celsius). Furthermore, the TOI-1518 star is approximately twice as large as our own sun with about 1.79 solar masses.

The astronomers then detected iron (Fe) in the exoplanet’s atmosphere. After completing an atmospheric cross-correlation analysis, they determined that neutral iron was present. This is quite significant as only a handful of other ultra-hot Jupiters have had iron detected in their atmospheres. The scientists went into further details by writing in part, “We searched for neutral and ionized Fe in the companion's atmosphere through high-resolution transmission spectroscopy. (...) We detect neutral iron (5.2σ), at Kp = 157 km/s and Vsys = −16 km/s, adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission.”

Their study was published in arXiv where it can be read in full.