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Uploaded:2016-07-15
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In this week's news we discover that Tatooine has got nothing on HD 131399Ab's wide orbit, and there's a some really cool jets coming out of a supermassive black hole.

Hosted by: Hank Green
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Sources:
http://www.skyandtelescope.com/astronomy-news/exoplanet-found-in-triple-star-system-0707201623/
https://www.eso.org/public/news/eso1624/
http://science.sciencemag.org/content/early/2016/07/06/science.aaf9671
http://phys.org/news/2016-07-alma-swirling-cool-jet-reveals.html
http://www.space.com/33365-black-hole-jet-is-super-cool.html
http://www.space.com/26765-supermassive-black-holes-rapid-growth.html
http://www.astro.yale.edu/coppi/pubs/bhgrowth4.pdf
http://www.aanda.org/articles/aa/abs/2016/06/aa27664-15/aa27664-15.html


Image Sources:
https://commons.wikimedia.org/wiki/File:Eso1624d.jpg
https://commons.wikimedia.org/wiki/File:Centaurus_IAU.svg
https://commons.wikimedia.org/wiki/File:Artist%E2%80%99s_impression_of_planet_in_the_HD_131399_system.jpg
https://commons.wikimedia.org/wiki/File:Aerial_View_of_the_VLTI_with_Tunnels_Superimposed.jpg
https://commons.wikimedia.org/wiki/File:Artist%E2%80%99s_impression_of_planet_orbiting_in_the_HD_131399_system.webm
https://commons.wikimedia.org/wiki/File:ALMA_Antennas_on_Chajnantor.jpg
https://commons.wikimedia.org/wiki/File:Supermassiveblackhole_nasajpl.jpg
https://commons.wikimedia.org/wiki/File:Artist%E2%80%99s_illustration_of_galaxy_with_jets_from_a_supermassive_black_hole.jpg
https://commons.wikimedia.org/wiki/File:Gyroscope_precession.gif
[SciShow intro plays]

Hank: There are all kinds of strange and surprising things in our universe, and astronomers just keep finding more of them. Like planets with huge orbits in triple-star systems, or weird cold jets coming from supermassive black holes.

Let’s start with the planet. Last week in Science, a paper was published explaining that scientists have found a triple star system with an exoplanet whose orbit is unlike anything we’ve seen before. This system is called HD 131399... but I’ll just call it HD for short, or we’ll be here all day. HD is about 320 light-years away from Earth, in the constellation Centaurus. It’s around 16 million years old, and its brightest star, HD-A, has almost twice the mass of the Sun.

And researchers from the University of Arizona found an exoplanet that’s orbiting this star, called HD-Ab, that’s about four times the mass of Jupiter and has a temperature of 580 degrees Celsius. This is the very first exoplanet discovered using something called the SPHERE instrument on the Very Large Telescope in Chile. It’s also one of the coldest and least massive exoplanets to be directly-imaged.

Direct imaging is kind of what it sounds like: it’s similar to photography and it uses either visible or infrared light. But it’s pretty tough to take a photo of an exoplanet, especially when its light is outshone by three other stars. The SPHERE instrument can help with that, blocking out some of the stars’ light and detecting infrared light from young planets.

Now, what’s really weird about HD-Ab is that it’s about 82 times as far from its star, as the Earth is from the Sun. Because of this huge orbit, a year on planet HD-Ab would be about 550 Earth-years. Which makes it the exoplanet with the widest orbit within a triple system known to scientists.

Normally, wide orbits like this aren’t very common because the presence of the other two stars makes the orbit unstable. So if HD-Ab’s orbit is unstable, it might eventually get ejected from its star system entirely. But why does this exoplanet have such a weird orbit in the first place? Well, the researchers suggest three main possibilities.

The first is that it used to be closer to the star, but the gravitational influence from another, unseen planet ejected it out farther. Another explanation is that it used to orbit the other two stars in the system instead, but it got ejected either by those stars or by another planet. It’s also possible that HD-Ab’s orbit is weird because... it just is.

The system might have just kept changing over time until happened to end up the way it is now. But whatever the reason, the fact that this exoplanet exists suggests that these multiple-star systems can be a lot more complex than we thought.

Another first-of-its-kind discovery published last month in the journal Astronomy & Astrophysics comes from Chalmers University of Technology in Sweden. The researchers used the ALMA telescope, also in Chile, to discover a cool, swirling jet coming out of a supermassive black hole. And this jet is really weird.

You’ll usually find a supermassive black hole at the center of most galaxies, including our own. Their masses can be millions to billions of times the mass of the Sun -- hence the “supermassive” thing. And they usually have hot jets of fast-moving material coming out of them, which suggests that there’s mostly hot gas and dust pouring into them. But that is not the case for the supermassive black hole this team found, at the center of the NGC 1377 galaxy.

This black hole has a cool jet instead, which could mean that it mostly feeds on cool, dense gas and dust. A supermassive black hole with a jet like this has never been seen in a galaxy before, but their existence might help astronomers figure out how supermassive black holes can grow so quickly. See, the jet coming out of the black hole formed very quickly, in about half a million years.

But it already has a mass that’s equal to about two million times the mass of the Sun. So this black hole is growing at an incredibly fast rate, much faster than regular supermassive black holes -- the ones that have hot jets and feed on hot gas and dust instead. Which means that its growth might come from the fact that it’s accreting, or gathering, cold stuff.

But! It’s also possible that this black hole isn’t feeding on cold material at all and its cool jets have nothing to do with the material falling into it. The jet from the supermassive black hole in NGC 1377 is also precessing, or swirling around, which jets from other supermassive black holes don’t normally do. This might be because the gas and dust is falling into the black hole unevenly.

Or the motion of the jet could be caused by another black hole nearby. So we’re just now finding out that these cold jets are even a thing. But they are a great way to study how black holes grow.

Thank you for watching this episode of SciShow Space News, and thank you especially to our patrons on Patreon who help make this show possible. If you want to help us keep making episodes like this, just go to Patreon.com/SciShow, and don’t forget to go to YouTube.com/SciShowSpace and subscribe!