A world called TOI 849 b could be the exposed, naked core of a gas giant whose atmosphere was blasted away by its star.

Every day is a bad day on planet TOI 849 b. About half the mass of our own Saturn, this planet orbits a Sun-like star more than 700 light-years from Earth. It hugs its star so tightly that a year – one trip around the star – takes less than a day. And it pays a high price for this close embrace: an estimated surface temperature of nearly 2,800 degrees Fahrenheit, which is 1,500 degrees Celsius. It's a scorcher even compared to Venus, which is 880 degrees Fahrenheit (471 degrees Celsius).

But for TOI 849 b, discovered in 2020 by NASA's Transiting Exoplanet Survey Satellite (TESS), the price of closeness to its star might have been even higher. Though about the size of Neptune, the planet appears to have little or no atmosphere. Scientists aren't sure why, but the possibilities include photoevaporation – the stripping away of a planet's atmosphere by intense radiation from its star.

Compared to other exoplanets that orbit very close to their stars, this planet is quite unusual because it is 40 times the mass of Earth but only about three times as big around. The gravity of such massive worlds should attract large amounts of gas from the disk of material out of which planets form. And planets with similarly large masses are five to 10 times as wide as Earth. But TOI 849 b is a lot less puffy than that, leading scientists to conclude that it lacks a substantial atmosphere.

PLANET TYPE
Gas Giant
DISCOVERY DATE
2020
MASS
39.09 Earths
PLANET RADIUS
0.307 x Jupiter
ORBITAL RADIUS
0.01598 AU
ORBITAL PERIOD
0.8 days
ECCENTRICITY
0.0
DETECTION METHOD