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A planet hotter than most stars

Astronomers have discovered a Jupiter-like world hotter than most stars. The planet has a year only 1.5 days long and might have a tail like a comet.

his artist’s concept shows planet KELT-9b orbiting its host star, KELT-9. It is the hottest gas giant planet discovered so far. Image via NASA/JPL-Caltech.

Astronomers have discovered a Jupiter-like world – named KELT-9b – with a day-side temperature of more than 7,800 degrees F. (4,316 degrees C.) That’s hotter than most stars, and only about 2,000 degrees F. (about 1,000 degrees C.) cooler than our sun.

Scott Gaudi, astronomy professor at The Ohio State University, led a study on the topic, described in the journal Nature on June 5, 2017. Gaudi said in a statement:

This is the hottest gas giant planet that has ever been discovered.

But KELT-9b’s star – KELT-9 – is even hotter. So hot, in fact, that it’s probably vaporizing the planet, say astronomers. The KELT-9 star is only 300 million years old, astronomers say, which is young in star time. It is more than twice as large, and nearly twice as hot, as our sun. Given that the planet’s atmosphere is constantly blasted with high levels of ultraviolet radiation, the planet may even be shedding a tail of evaporated planetary material like a comet. Study co-author Keivan Stassun is a professor of physics and astronomy at Vanderbilt University. He said:

KELT-9 radiates so much ultraviolet radiation that it may completely evaporate the planet.

But that’s assuming the star doesn’t grow to engulf the planet first. Stassun said:

KELT-9 will swell to become a red giant star in a few hundred million years. The long-term prospects for life, or real estate for that matter, on KELT-9b are not looking good.

According to a NASA statment:

Because the planet is tidally locked to its star – as the moon is to Earth – one side of the planet is always facing toward the star, and one side is in perpetual darkness. Molecules such as water, carbon dioxide and methane can’t form on the dayside because it is bombarded by too much ultraviolet radiation. The properties of the nightside are still mysterious – molecules may be able to form there, but probably only temporarily.

The planet is also unusual in that it orbits perpendicular to the spin axis of its star. That would be analogous to the planet orbiting perpendicular to the plane of our solar system. One “year” on this planet is less than two days.

The KELT-9b planet was found using one of the two telescopes called KELT, or Kilodegree Extremely Little Telescope.

Bottom line: Newly-discovered planet is hotter than most stars.

Read more from NASA

Eleanor Imster