NASA scientists have used measurements taken from the Transiting Exoplanet Survey Satellite known as TESS to improve their understanding of the environment of one of the hottest planets in the known universe called KELT-9 b. That planet is bizarre in that it is a giant planet and very close, nearly polar orbit around a rapidly rotating star. KELT-9 b is about 670 light-years away in the constellation Cygnus.
The planet was discovered in 2017 by the KELT transit survey using two robotic telescopes located in Arizona and South Africa. KELT-9 b is a gas giant planet about 1.8 times larger than Jupiter with 2.9 times its mass. Tidal forces have locked its rotation so that the same side of the planet always faces its star.
The giant planet swings around the host star in only 36 hours, on an orbit that carries it almost directly above the poles of the star. KELT-9 b receives 44,000 times more energy from its star than the Earth does from the Sun. Scientists say that the planets dayside temperature is around 7800-degrees Fahrenheit, which is hotter than the surface of some stars.
The intense heating causes the planet’s atmosphere to stream away into space. As strange as the planet itself is, the star is odd as well. KELT-9 b’s host star is about twice the size of the Sun and is about 56% hotter. It also spends 38 times faster than the Sun completing a full rotation in only 16 hours.
It’s fast spin also distorts the shape of the star flattening at poles and widening its midsection. The star has a temperature difference across its surface of almost 1500-degrees Fahrenheit. Another interesting fact about KELT-9 b is that the planet experiences two summers and two winters every year, with each season lasting about nine hours. Summers occur as the planet swings over each hot pole and winter when it passes over the star’s midsection.