JPL: A Planet Hotter Than Most Stars

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JPL: A Planet Hotter Than Most Stars

Post by bystander » Tue Jun 06, 2017 3:05 pm

Astronomers Find Planet Hotter Than Most Stars
NASA | JPL-Caltech | 2017 Jun 05

A newly discovered Jupiter-like world is so hot, it's being vaporized by its own star.

With a dayside temperature of more than 7,800 degrees Fahrenheit (4,600 Kelvin), KELT-9b is a planet that is hotter than most stars. But its blue A-type star, called KELT-9, is even hotter -- in fact, it is probably unraveling the planet through evaporation. ...

KELT-9b is 2.8 times more massive than Jupiter, but only half as dense. Scientists would expect the planet to have a smaller radius, but the extreme radiation from its host star has caused the planet's atmosphere to puff up like a balloon.

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. ...

A planet hotter than most stars
Ohio State University | 2017 Jun 05

Astronomers discover exoplanet hotter than most stars
Vanderbilt University | 2017 Jun 05

A giant planet undergoing extreme-ultraviolet irradiation by its hot massive-star host - B. Scott Gaudi et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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MPIA: Detecting the Boiling Atmosphere of KELT-9b

Post by bystander » Tue Jul 03, 2018 5:51 pm

Detecting the Boiling Atmosphere of the Hottest Known Exoplanet
Max Planck Institute for Astronomy | 2018 Jul 02
Astronomers have found that the atmosphere of the hottest known exoplanet, the hot Jupiter-like planet KELT-9b, is "boiling off," with the escaping gas being captured by the host star. Using the CARMENES instrument at Calar Alto Observatory, Fei Yan and Thomas Henning of the Max Planck Institute for Astronomy in Heidelberg were able to detect the escaping hydrogen atmosphere of the planet. Their observations indicate a spread-out hydrogen envelope that is being pulled towards the host star.

By all definitions, KELT-9b is a hellish kind of exoplanet: Due to its proximity to an extremely hot host star, the planet itself is the hottest exoplanet yet discovered. Now Fei Yan and Thomas Henning of the Max Planck Institute for Astronomy have detected that planet's extended atmosphere, showing that the star is not only heating up the planet's hydrogen atmosphere – it is then using its gravity to pull the hydrogen onto itself.

Specifically, the planet's host star KELT-9 is an extremely hot star with a temperature of up to 10,000 K (compare this with the Sun's much more modest 5800 K, or 5500 degrees Celsius). The planet's orbit is extremely small – ten times smaller than the orbit of Mercury in our Solar system (corresponding to only about 3% of the diameter of Earth's orbit around the Sun). When the planet was discovered in 2017 by a team of astronomers led by B. Scott Gaudi (Ohio State University), the astronomers measured its day-side temperature to be at 4600 K (4300 degrees Celsius), which is hotter than many stars!

The planet itself is a significantly larger version of our Solar System's Jupiter, at almost 3 times Jupiter's mass and almost twice Jupiter's diameter. These properties combined place KELT-9b firmly in the class of what astronomers call "hot Jupiter". ...

The atmosphere of Kelt-9b is being dragged towards its star
Hispanic-German Astronomical Center (CAHA) | Calar Alto Observatory | 2018 Jul 03

An Extended Hydrogen Envelope of the Extremely Hot Giant Exoplanet KELT-9b - Fei Yan, Thomas Henning
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor