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
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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
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Geneva: Iron & Titanium in the Atmosphere of an Exoplanet

Post by bystander » Wed Aug 15, 2018 8:29 pm

Iron & Titanium in the Atmosphere of an Exoplanet
University of Geneva | 2018 Aug 15
Exoplanets, planets in other solar systems, can orbit very close to their host star. When, in addition to this, the host star is much hotter than our Sun, then the exoplanet becomes as hot as a star. The hottest “ultra-hot” planet was discovered last year by American astronomers. Today, an international team, led by researchers from the University of Geneva (UNIGE), who joined forces with theoreticians from the University of Bern (UNIBE), Switzerland, discovered the presence of iron and titanium vapours in the atmosphere of this planet. The detection of these heavy metals was made possible by the surface temperature of this planet, which reaches more than 4000 degrees. This discovery is published in the journal Nature.

KELT-9 is a star located 650 light years from Earth in the constellation Cygnus (the Swan). With a temperature of over 10,000 degrees, it is almost twice as hot as the Sun. This star is orbited by a giant gas planet, KELT-9b, which is 30 times closer than the Earth’s distance from the Sun. Because of this proximity, the planet circles its star in 36 hours and is heated to a temperature of over 4,000 degrees. It’s not as hot as the Sun, but hotter than many stars. At present, we do not yet know what an atmosphere looks like and how it can evolve under such conditions.

That is why NCCR PlanetS researchers affiliated with the University of Bern recently performed a theoretical study on the atmosphere of the planet KELT-9b. “The results of these simulations show that most of the molecules found there should be in atomic form, because the bonds that hold them together are broken by collisions between particles that occur at these extremely high temperatures”, explains Kevin Heng, professor at the UNIBE. This is a direct consequence of the extreme temperature. Their study also predicts that it should be possible to observe gaseous atomic iron, in the planet’s atmosphere using current telescopes. ...

Atomic Iron and Titanium in the Atmosphere of the Exoplanet KELT-9b - H. Jens Hoeijmakers et al
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Re: JPL: A Planet Hotter Than Most Stars

Post by Ann » Wed Aug 15, 2018 10:51 pm

Can't help it, I love the illustration. That's me. :wink:

That star, KELT-9, is slightly hotter than Vega, whose spectral class is A0. According to Jim Kaler, the temperature of Vega is about 9,500 K. However, because Vega has an oblate shape, its temperature varies from "10,150 at the poles to 7950 at the equator". And because we see Vega pole on, we see the hottest part of it.

My point is that KELT-9 is either a star very much like Vega, or else it is even hotter than Vega. Probably it is hotter. The planet probably orbits the star's equator, not its poles. So KELT-9 may be a B9-type star.

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Re: JPL: A Planet Hotter Than Most Stars

Post by neufer » Thu Aug 16, 2018 1:06 am

Ann wrote:
Wed Aug 15, 2018 10:51 pm

That star, KELT-9, is slightly hotter than Vega, whose spectral class is A0. According to Jim Kaler, the temperature of Vega is about 9,500 K. However, because Vega has an oblate shape, its temperature varies from "10,150 at the poles to 7950 at the equator". And because we see Vega pole on, we see the hottest part of it. My point is that KELT-9 is either a star very much like Vega, or else it is even hotter than Vega. Probably it is hotter.

The planet probably orbits the star's equator, not its poles. So KELT-9 may be a B9-type star.
https://news.vanderbilt.edu/2017/06/05/astronomers-exoplanet-hotter-stars/ wrote:
Astronomers discover exoplanet hotter than most stars
by David Salisbury Jun. 5, 2017, 10:00 AM

We were pretty lucky to catch the planet while its orbit transits the face of the star,” said co-author Karen Collins, a post-doctoral fellow at Vanderbilt. “Because of its extremely short period, near-polar orbit and the fact that its host star is oblate, rather than spherical, we calculate that orbital precession will carry the planet out of view in about 150 years, and it won’t reappear for roughly three and a half millennia.
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Re: JPL: A Planet Hotter Than Most Stars

Post by Ann » Thu Aug 16, 2018 1:47 am

Thanks for the info, Art! So KELT-9 may be a proper Vega analog, then.

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Re: JPL: A Planet Hotter Than Most Stars

Post by neufer » Thu Aug 16, 2018 11:00 am

Ann wrote:
Thu Aug 16, 2018 1:47 am

Thanks for the info, Art! So KELT-9 may be a proper Vega analog, then.
If we had a polar view of KELT-9 then precession would not carry the near polar orbiting planet out of view. So KELT-9 cannot be a proper Vega analog.

I'm sure they have this all pretty well figured out ... perhaps even with some near IR measurements of the planet's phases & eclipse.
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Re: JPL: A Planet Hotter Than Most Stars

Post by Ann » Thu Aug 16, 2018 2:16 pm

neufer wrote:
Thu Aug 16, 2018 11:00 am
Ann wrote:
Thu Aug 16, 2018 1:47 am

Thanks for the info, Art! So KELT-9 may be a proper Vega analog, then.
If we had a polar view of KELT-9 then precession would not carry the near polar orbiting planet out of view. So KELT-9 cannot be a proper Vega analog.

I'm sure they have this all pretty well figured out ... perhaps even with some near IR measurements of the planet's phases & eclipse.
You understand this far, far better than I do, Art. I would appreciate it if you could explain it in layman's terms, so that I, too, could get it.

Then again, explaining things in layman's terms is perhaps not your forte... in the same way as using pure math to understand something is most certainly not my forte!

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Re: JPL: A Planet Hotter Than Most Stars

Post by neufer » Thu Aug 16, 2018 3:06 pm

Ann wrote:
Thu Aug 16, 2018 2:16 pm

You understand this far, far better than I do, Art. I would appreciate it if you could explain it in layman's terms, so that I, too, could get it.
Based upon the artist impression alone you had it right about our equatorial view of the star but wrong about the equatorial orbit of the planet. (50% is fine for a layperson.)

https://www.etymonline.com/word/layman wrote:
layman (n.): "non-cleric," early 15c., from lay (adj.) + man (n.). Similar formation in Danish lægmand. Meaning "outsider, unprofessional person, non-expert" is from late 15c.
Professionally, I worked as a "cleric" on NOAA TIROS (near)polar orbiting weather satellites. They were launched from California over the Pacific Ocean such that the oblate Earth would cause the satellite to slowly precess eastward to track the annual motion of the Sun through the zodiac. This allowed the Earth to rotate exactly once every 24 hours under the satellite (rather than the nominal Sidereal rotation period of 23h 56m 4.1s).
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Re: JPL: A Planet Hotter Than Most Stars

Post by Ann » Thu Aug 16, 2018 10:39 pm

neufer wrote:
Thu Aug 16, 2018 3:06 pm
Ann wrote:
Thu Aug 16, 2018 2:16 pm

You understand this far, far better than I do, Art. I would appreciate it if you could explain it in layman's terms, so that I, too, could get it.
Based upon the artist impression alone you had it right about our equatorial view of the star but wrong about the equatorial orbit of the planet. (50% is fine for a layperson.)

https://www.etymonline.com/word/layman wrote:
layman (n.): "non-cleric," early 15c., from lay (adj.) + man (n.). Similar formation in Danish lægmand. Meaning "outsider, unprofessional person, non-expert" is from late 15c.
Professionally, I worked as a "cleric" on NOAA TIROS (near)polar orbiting weather satellites. They were launched from California over the Pacific Ocean such that the oblate Earth would cause the satellite to slowly precess eastward to track the annual motion of the Sun through the zodiac. This allowed the Earth to rotate exactly once every 24 hours under the satellite (rather than the nominal Sidereal rotation period of 23h 56m 4.1s).
Thanks for the illustration, Art! And thanks for telling me that we do see KELT-9 more or less "equator-on", and that KELT-9 is therefore hotter than Vega.

You said:
If we had a polar view of KELT-9 then precession would not carry the near polar orbiting planet out of view. So KELT-9 cannot be a proper Vega analog.
This is what I can't picture in my head. Yes, I know about precession, sort of. What I just can't "see" is why precession would carry KELT-9b out of view because of the planet's polar orbit. Sigh! I'll just take your word for it.
Click to play embedded YouTube video.
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Re: JPL: A Planet Hotter Than Most Stars

Post by BDanielMayfield » Fri Aug 17, 2018 5:01 am

The most amazing thing about this system is NOT the fact that the planet has been superheated, hot Jupiters are common. What seems totally out of whack about this system is the vast difference between the star's rotational plain and the planet's weird nearly polar orbit. How can a rotating clump of gas and dust condense into a massive, very rapidly rotating star ALONG WITH a close, very massive planet that's orbiting nearly 90 degrees out of alignment with the star??? Something very strange must have happened here.

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