Astronomers discover a giant planet hotter than most stars

Kelt-9b planet was discovered in 2014 when astronomers spotted the shadow as it crossed the face of its host star 650 light years away.

Created On: Jun 6, 2017 13:18 ISTModified On: Jun 6, 2017 13:17 IST

A team of astronomers led by B Scott Gaudi, an astronomer at the Ohio State University, recently discovered hottest giant planet named KELT-9b, an exoplanet that is hotter than the most stars.  The findings were published in the journal Nature on 5 June 2017.

KELT-9b is regarded as a hybrid planet-star. It has the mass of a planet, and an atmosphere like a star.


Astronomers discovered giant planet hotter than most stars

How was KELT-9b discovered?
Kelt-9b planet was discovered in 2014 when astronomers spotted the shadow as it crossed the face of its host star 650 light years away from Earth in the constellation of Cygnus. The planet was so close to the star that its surface reaches more than 4300 degrees C, making it the hottest giant planet ever found.

Astronomers discovered this hottest planet using two robotic telescopes Kilodegree Extremely Little Telescope (KELT)  in Arizona and Sutherland to the north of Cape Town in South Africa.

The twin telescopes focused on a star called Kelt-9 which at 10000 degrees C is nearly twice as hot as the sun. The observations revealed a regular dimming of starlight reaching Earth, the signature of a massive planet that was moving around it once every one-and-a-half days.

Made with off-the-shelf components, the Kilodegree Extremely Little Telescopes were built at a fraction of the cost of conventional multimillion dollar observatories.

The Findings
KELT-9b is estimated to be roughly 3777 degrees Celsius on the dark side and 4327 degrees C on the star-exposed side. This makes KELT-9b almost 20 per cent hotter than the next-most-boiling exoplanet WASP-33b.

KELT-9b receives 700 times as much solar radiation as WASP-33b, which is similar to the glow of an entire K-type star, the second coolest type and is more than enough to break down molecules to their constituent atoms.

The new planet’s scorching temperature is due its parent star KELT-9 which falls in the A-type bracket of stars, the third-hottest category. It is the seventh star of its classification to be found with an exoplanet and at roughly 300 million years old.

KELT-9b is surprisingly puffy, given that its mass is almost three times Jupiter’s. KELT-9b is 2.8 times more massive than Jupiter, but only half as dense.

For reasons no one fully understands yet, the planet also orbits its star from pole to pole, rather than around the equator as would be expected.

The planet is tidally locked to its star as the moon is to Earth. One side of the planet is always facing towards the star, and one side is in perpetual darkness.

Molecules such as water, carbon dioxide and methane can’t form on the dayside of the planet as it is bombarded by too much ultraviolet radiation.

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Early exoplanet discoveries happened around low-mass stars. These findings inspire a trend of researchers pursuing stars of lower and lower masses.

The discovery of KELT-9b might encourage more researchers to go into the depths of other planets on the opposite end of the typically researched spectrum.

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