The new Jupiter Ultrahot contains iron in its atmosphere

Astronomers have discovered a highly irradiated gas giant exoplanet in close orbit and very misaligned around a bright star called TOI-1518.

Artist’s impression of the ultra-warm Jupiter TOI-1518b and its mother star. Image credit:

TOI-1518 is a rapidly rotating F-type star located approximately 742 light-years away in the constellation Cepheus.

Also referred to as TIC 427761355 and BD + 66 1610, it is almost twice the size and more massive than the Sun.

The new planet TOI-1518b is a swollen gas giant about 1.9 times the size of Jupiter.

It orbits its mother star once every 1.9 days at a distance of 0.04 AU (astronomical units).

“The new planet belongs to the category of super-hot Jupiters, which have equilibrium temperatures above 2000 K,” said Yale University astronomer Samuel Cabot and his colleagues.

“Many super-hot Jupiters contain vaporized metals, both neutral and ionized, in their upper atmosphere. “

“These metals and molecules containing them are recognized as strong sources of opacity in optical and near ultraviolet regions.”

TOI-1518b was first identified as a candidate transiting exoplanet in photometric data from NASA’s Transiting Exoplanet Survey Satellite (TESS).

The planet’s presence was then confirmed using high-resolution optical transmission spectra from the EXtreme PREcision Spectrometer (EXPRES) on the Lowell Discovery Telescope.

Additionally, Cabot and his co-authors detected iron vapor in the atmosphere of TOI-1518b.

“TOI-1518b is highly inflated, which makes it suitable for intensive atmospheric characterization,” they said.

“The equilibrium temperature of TOI-1518b (2.492 K) is in the regime where the planet could exhibit a thermal inversion.”

“This, combined with the brightness of the host star, makes TOI-1518b an attractive target for tracking emission spectroscopy.”

The team’s article will be published in the Astronomical Journal.


Samuel HC Cabot et al. 2021. TOI-1518b: An ultra-hot Jupiter misaligned with iron in its atmosphere. A J, in the press; arXiv: 2108.11403

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