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Uploaded:2022-05-13
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With exoplanets, often we want to know if they are Earth-like and whether they might host life, but we can also learn a lot from planets that are nothing like Earth.

Hosted By: Hank Green
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Sources:
https://iopscience.iop.org/article/10.3847/1538-3881/ac26bd/pdf
https://www.nasa.gov/feature/jpl/investigating-the-mystery-of-migrating-hot-jupiters
https://news.mit.edu/2021/planet-ultrahot-toi-2109b-1123
https://www.sciencealert.com/gas-giant-exoplanet-has-the-most-extreme-orbit-discovered-yet-and-it-s-totally-doomed
https://www.jpl.nasa.gov/news/for-hottest-planet-a-major-meltdown-study-shows
https://ui.adsabs.harvard.edu/abs/2016DDA....4720403C/abstract
https://ui.adsabs.harvard.edu/abs/2017Natur.546..514G/abstract
https://ui.adsabs.harvard.edu/abs/2011Natur.480..496C/abstract
https://www.aanda.org/articles/aa/full_html/2015/09/aa26346-15/aa26346-15.html
https://ui.adsabs.harvard.edu/abs/2019A%26A...627A..86B/abstract

Images:
https://svs.gsfc.nasa.gov/13795
https://commons.wikimedia.org/wiki/File:Artist%E2%80%99s_impression_of_a_hot_Jupiter_exoplanet_in_the_star_cluster_Messier_67.jpg
https://commons.wikimedia.org/wiki/File:Artist%27s_impression_of_a_gas_giant_planet_forming_in_the_disc_around_the_young_star_HD_100546.jpg
https://www.shutterstock.com/image-illustration/hot-jupiter-class-exoplanet-gas-giant-1141368953
https://svs.gsfc.nasa.gov/13635
https://photojournal.jpl.nasa.gov/catalog/PIA21472
https://photojournal.jpl.nasa.gov/catalog/PIA21472
https://exoplanets.nasa.gov/resources/2144/transit-method-multiple-planets/
https://www.gettyimages.com/detail/photo/hot-jupiter-an-exoplanet-approached-the-sun-royalty-free-image/1356390718?adppopup=true
https://www.gettyimages.com/detail/video/the-sun-storm-stock-footage/500539061
https://commons.wikimedia.org/wiki/File:Kepler-70b.png
https://commons.wikimedia.org/wiki/File:Kepler-70b.jpg
https://www.gettyimages.com/detail/video/two-female-friends-vlogging-in-city-with-digital-camera-stock-footage/1321450590
https://www.gettyimages.com/detail/video/4k-video-footage-of-a-mature-businessman-talking-on-a-stock-footage/1323564486?adppopup=true
Thanks to Babbel, a language learning  app, for sponsoring this episode.

If you’re interested in growing your  language skills, SciShow Space viewers get up to 65% off with a 20 day money-back  guarantee when you use our link. [♪ INTRO] The search for exoplanets is one of the  hottest areas of astronomy right now. And one main reason for that is because  humans are dying to know if there are other Earth-like planets out there…  and whether or not they might host life.

But sometimes, researchers are  interested in exploring the other end of the spectrum: the planets  that are nothing like Earth. These planets can give us an idea  what extremes are possible out there in the universe, and offer us  insight into how planets come to be and how they evolve over time. Some of the most fascinating  planets are the incredibly hot ones.

So today, we’ll take a look at three of  the most blistering-hot worlds ever found. The first is a planet called TOI-2109b. It’s a huge gas giant in the constellation  Hercules, 855 light-years away.

The planet is five times the mass of  Jupiter, but unlike our Jupiter, it orbits extremely close to its star, which is just  a little bit bigger and hotter than our Sun. The planet circles its star at a  distance of about 2.6 million kilometers. Now, that sounds like a long way, but it’s  basically a stone’s throw in astronomical terms.

That’s just under 5% of the distance between  our Sun and its closest planet, Mercury. It’s so close that its entire  year is just 16 hours long. When astronomers first  discovered huge planets like this so close to their stars, they were confused.

Because in the early days of planet  formation in a stellar system, it’s just too hot near the star  for such a big planet to form. The material needed for the  core is too hot to be solid, and the gas needed for the  atmosphere is too hot to be captured. So this planet, and others like  it, must have formed farther out, like Jupiter, but migrated inward.

And now, because of its proximity to its star, the day side of this so-called ultrahot  Jupiter is around 3300 degrees Celsius. That’s at least a thousand degrees more  than the night side of the planet. And this temperature difference is  believed to drive ferocious winds across the planet, making the skies  of this world a pretty horrific place.

But, while this planet gets almost  hot enough to melt diamonds, it’s not even the hottest planet out there. That distinction goes to  another giant, known as KELT-9b. This planet orbits a star 670 light-years  from Earth, and it’s also an ultrahot Jupiter.

It’s more than three times  as massive as our Jupiter, and its orbit is around  twice as big as TOI-2109b’s. Now, since it’s farther from its star,  you might also expect it to be cooler. But KELT-9b orbits an absurdly hot star.

The star burns white-hot, and  at about 10,000 degrees Celsius, it’s around twice as hot as our own Sun. That gives KELT-9b a scorching  temperature of 4,300 degrees Celsius. It’s a planet hotter than most stars.

And that temperature would  melt… pretty much anything. Even high-tech hafnium  carbide, the material on Earth with the highest known melting point,  would turn to mush on this planet. It’s actually so hot that astronomers think  molecules of hydrogen in its atmosphere get ripped apart on the day side and  reform on the slightly cooler night side.

This extreme cycle likely won’t  go on for too long, though, at least not in astronomical terms. The searing heat is evaporating the  material that makes up the planet. And observations show that the  intense radiation from its star seems   to be blasting away these evaporated  gases, almost like a comet’s tail. ~ So, in a few hundred million years,  the planet may be no more than a husk.

Now, it’s hard to beat KELT-9b when  it comes to extremely hot planets. But we’d be remiss if we  didn’t give a little shoutout to a hypothetical exoplanet known as Kepler 70b. Astronomers found what could be the sign  of a planet while they were observing the star Kepler 70, in the constellation Cygnus.

They picked up some periodic dips in the  star’s brightness, which is a pattern that can happen as a planet passes in front of  its star and blocks a little bit of light. This is actually one of the most common  ways astronomers discover exoplanets. And in this case, these dips suggested  that astronomers were possibly looking at a gas giant circling its star so closely  that it made a full orbit every six hours.

But measurements like these are really tricky. Detecting a gas giant passing in front  of a star is like detecting a mosquito passing in front of a car headlight  over a hundred kilometers away. And follow-up studies using different  detection methods have suggested that these dips in Kepler 70’s brightness  are just natural variations, not the signature of a planet.

So the planet Kepler 70b  likely doesn’t exist after all. But if it did, it would be the  hottest planet ever discovered, at over 7000 degrees Celsius. Now, none of the planets we’ve  talked about today are even close to being anything like… even near-habitable,  but the existence of these extremes gives us an idea about the  variety of planets that can exist.

And they’re a reminder that we share  this galaxy with some incredible worlds. Learning a new language requires  a lot of time and commitment, making it difficult to quickly  get into conversations. But if you’re as impatient as I am,  Babbel can help you start speaking fast.

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So whether you’re looking to brush up  on your skills for a summer adventure abroad or to gain a language skill to  help with your professional development, Babbel will help you learn about both the  language and the culture that speaks it. As a SciShow viewer, you’ll get up 65% off when  you sign up using our link in the description. Plus Babbel comes with a 20  day money back guarantee, so you can see where Babbel takes  you on our language learning journey. [♪ OUTRO]