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Kelt-9b is an exoplanet( planets, orbiting stars other than the Sun) more specifically, an ultra-hot Jupiter,that orbits the late B-type/early A-type star Kelt-9, located about 670 light-years from Earth.It is detected using the “Kilodegree” – an extremely Little Telescope, the exoplanet was announced in 2016.

Do you think planets can be hotter than stars?

Facts behind Kelt-9b

• The hottest exoplanet known so far is Kelt-9 b, which was discovered in 2016.

• Kelt-9 b orbits a star that is twice as hot as our Sun, at a distance ten times closer than Mercury orbits our star.

• It is a large gaseous exoplanet, with a radius 1.8 times that of Jupiter and temperatures reaching 5,000K.

• For comparison, this is hotter than 80% of all the stars in the universe and a similar temperature to our Sun.

How can we observe the atmospheres of an exoplanet like kelt-9b??

• There are two main methods to study exoplanet atmospheres.

• In the transit method, we can pick up stellar light that is filtered through the exoplanet’s atmosphere when it passes in front of its star, revealing the fingerprints of any chemical elements that exist there.

• The other method to investigate a planet is during an “eclipse”, when it passes behind its host star. Planets also emit and reflect a small fraction of light, so by comparing the small changes in the total light when the planet is hidden and visible, we can extract the light coming from the planet.

What made it auspicious on observing the atmosphere of kelt-9b??

• The presence of molecules and found there were plenty of metals (made from molecules). This discovery is interesting as it was previously thought that these molecules would not be present at such extreme temperatures – they would be broken apart into smaller compounds • Subject to the strong gravitational pull from its host star, Kelt-9 b is “tidally locked”, which means that the same face of the planet permanently faces the star. This results in a strong temperature difference between the planet’s day and night sides.

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