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We have gotten really good at spotting exoplanets.
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Usually we see them when they transit in front of their star and cause a drop in light levels,
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or when their gravitational pull makes their star wobble.
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But very rarely, it's possible to see them with an optical telescope and we've seen
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about fifty this way.
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But that number has actually gone down, because one of the first exoplanets ever directly
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imaged vanished in 2014.
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Now new research may explain where it went.
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Was it destroyed by a Death Star?
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It was the Death Star, wasn't it?
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The planet in question was observed orbiting the star Fomalhaut, and so was named Fomalhaut b.
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Hubble was the first to spot it in 2004 and again in 2006 as a moving dot around its star,
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and it could have been easily missed.
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Even though it was estimated to be as massive as three Jupiters and much brighter than other
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exoplanets, which tend to be too small to reflect enough light for us to see, Fomalhaut b
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is a billion times fainter than its star.
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One astronomer called it “one of the most difficult detections
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in the history of exoplanet science.”
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Though it was spotted in 2004 and 2006, there was some controversy over whether or not it
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was actually an exoplanet.
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Some things just seemed off.
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For one thing, its orbit was highly elliptical.
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Fomalhaut, by the way, also has a huge debris belt around it, so a false-color composite
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image of the system taken by Hubble looks like, there's no other way of saying it,
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the eye of Sauron.
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Then there's the fact that it didn't radiate any detectable infrared radiation.
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Scientists expected to see some heat coming off what they assumed was a large and young
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planet, but there wasn't any to see.
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Nonetheless, in 2008 scientists declared it was an exoplanet visible from Earth, causing
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much debate.
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And then in 2014, Fomalhaut b up and vanished on us.
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You ungrateful hunk of space rock, do you know how lucky you are? Pluto would kill to
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be declared a planet!
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To find out where it went, astronomers from the University of Arizona returned to the
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first images taken of it by Hubble in 2004 and tracked its evolution until its 2014 disappearance,
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presumably while muttering “enhance” the whole time.
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Over that 10-year period Fomalhaut b actually appeared to expand and fade away.
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Now, in early May of 2020, they think they have an explanation.
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The astronomers who noticed the expansion and slow fade concluded that Fomalhaut b the
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planet never existed in the first place.
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Plot twist!
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Instead they suggest it was a cloud of expanding dust that resulted from two massive planetesimals
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smashing into each other.
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This hypothesis would explain some outstanding questions about Fomalhaut b nicely, like the
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elliptical shape of the orbit, and how it would fade as the small dust particles spread
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out until they fell below Hubble's detection limit.
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So, Fomalhaut b may not have been one of the 50 or so exoplanets we've directly imaged
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through a telescope, but it may be something we've seen even less often.
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We almost never directly observe collisions of massive objects like these, and based on
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the simulations proposed by the study's authors, Hubble only just missed this collision.
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It could be a very useful data point that helps us understand how planetary systems
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evolve.
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That's assuming this new explanation is in fact what we saw.
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It's thought a dust cloud like this wouldn't be visible until a decade after the asteroid's
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crash, disagreeing with the model the astronomers from the University of Arizona put forward
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for Fomalhaut b's disappearance.
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Perhaps it's something even stranger.
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More observations from bigger and better telescopes like the long awaited James Webb could finally
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put this mystery to bed.
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So, what I'm hearing is the Death Star...not totally off the table yet.
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While this new paper suggests Fomalhaut b was the result of two planetesimals colliding,
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it's not the first time someone proposed the “planet” was actually just a cloud
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of dust.
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As our technology improves, we're not going to just look for exoplanets, but signs of
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alien life as well.
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Check out Amanda's video on the future of space-observing cameras here.
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Make sure to subscribe to Seeker for more videos like this, and as always, thanks for
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watching.
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I'll see you next time.