NASA Uncovers KELT-9b! One of the hottest and most bizarre planets known has been modeled by astronomers using measurements from NASA’s planet-hunting Transiting Exoplanet Survey Satellite (TESS) mission.
The previously-discovered planet, known as KELT-9 b and HD 195689 b, is about twice the size of Jupiter and has a dayside temperature that reaches around 7,800º Fahrenheit/4,300º Celsius, which is hotter than the surfaces of some stars.
It’s so big that it’s thought to be on the cusp between being a planet and a star.
It’s so hot that its atmosphere certainly boils away into space.
“The weirdness factor is high with KELT-9 b,” said John Ahlers, an astronomer at Universities Space Research Association in Columbia, Maryland, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s a giant planet in a very close, nearly polar orbit around a rapidly rotating star, and these features complicate our ability to understand the star and its effects on the planet.”
What and where is KELT-9 b?
It’s a (very) “hot Jupiter” giant planet orbiting a star about 670 light-years away.
If you’re anything like me, you’ll want to know where it is before learning much about it. Although it’s just outside naked eye visibility, it’s very close to the bright star Sadr at the center of the Northern Cross in the constellation Cygnus, the Swan. That’s easily seen in the northern hemisphere’s summer night skies—it’s high in the eastern sky come darkness.
What’s so bizarre about KELT-9 b?
It’s not just ultra-hot. Here’s what’s going on at KELT-9 b:
- It’s a gas giant world about 1.8 times bigger than Jupiter, with 2.9 times its mass.
- It always shows the same side to its star—much like the Moon does to Earth.
- It orbits its star in just 36 hours and travels directly above both of the star’s poles.
- It receives 44,000 times more energy from its star than Earth does from the Sun.
- Every 36 hours, KELT-9 b experiences two summers and two winters, with each season about nine hours.
Why is KELT-9 b so hot?
The star has hot poles and a cool equator, which means that during a single 36-hour orbit—a year—the planet KELT-9 b experiences two cycles of heating and cooling. That means a summer when the planet faces the star’s pole and winter when it faces the star’s equator. The result is that KELT-9 b experiences two summers and two winters every 36 hours.