Universe Guide

Meet Kelt-9b, the Hottest Planet so far Discovered

If you think 30 degrees Celsius is extremely hot, you have no idea how hot things can get. The highest recorded temperature on Earth that has so far been recorded is 56.7 C and that was recorded on 10th July 1913 in Death Valley, California, United States. The previous highest with a measurement of 58 C was disqualified in 2012 by the World Meteorological Society. Ref: Guiness World Records.

The planet that is nearest to the Sun is Mercury but its not the hottest planet in the solar system believe it or not. The temperature of Mercury is about 160 C. The hottest planet in the solar system is the second nearest and that is Venus. Venus might be in the Goldilocks Zone but it has terrible global warming and run away temperatures. Venus is encompassed by a thick cloud of noxious gases that keep the heat in. It was once thought that the planet might have alien life but that has all but evaporated apart from some who think there still could be life out in Venus at high altitude where temperatures aren't as high. Any life would be bacterial which have been known to survive extreme temperatures.

Venus at a temperature of about 464 C is nowhere near as hot as what some scientists believe is the hottest planet so far discovered. The hottest planet outside our Solar System is imaginatively named Kelt-9b. Its name comes the star that it is in orbit round, Kelt 9 in the constellation of Cygnus the Swan. Ref: Vanderbilt

Kelt is not a name of a Greek or Roman god but an acronym for Kilo-degree Extremely Little Telescope. Kelt is a collaborative project between the Physics and Astronomy departments from Ohio State University, Vanderbilt University, Lehigh University and the South African Astronomical Observatory (SAAO).

Kelt 9b orbits very close to it star hence its extreme heat. The star is an A-Type star which means its a super hot and large star similar to Fomalhaut and Beta Pictoris which incidentally both stars also known to have planets in orbit round them. A rough estimate of the temperature of Fomalhaut for example based on the spectral type puts the temperature of the star at about 8-10,000C which we'll infer is the same temperature as Kelt-9. The temperature of Kelt-9 is put at about 4,300C which is hotter than a lot of stars, most notably red dwarf stars which are the most common type of stars in the universe although we can't see them from the Earth without telescopic aids. The nearest star is Proxima Centauri which is a red dwarf star and that's about 2,942C based on the spectral type. A planet hotter than a star, who'd have thought.

The planet is close to the star and orbits every two days, a year faster than a week. Another reason to avoid that planet, short years. The planet is about three times the mass of Jupiter and twice as big. Jupiter is about 11 times as big as the Earth so the planet is about 22 times as big in terms of radius. The planet doesn't orbit in the same way as the Earth in that it goes East to West but South to North.

Being so close to the star, its being boiled away by the sheer heat that the star is projecting onto it. The planet would look like a comet with a tail due to the heat from the star and would look blue if it was observed because of the heat. It won't disappear anytime soon, the planet is believed to be around for another 300 years and after that, all that'll be left is the rocky core if there is one. Ref: EOS

The planet is tidally locked to the planet meaning one side is always facing the star and one side is always facing away. The picture below is N.A.S.A. artist impression of the planet and its star.

In contrast, the coldest planet in the solar system is Neptune, that is if you exclude Pluto which was downgraded from planetary status. Neptune is about -201C, equally not a nice place to go.

N.A.S.A. artist's impression of Kelt-9b planet in the constellation of Cygnus

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