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  • We have gotten really good at spotting exoplanets.

  • Usually we see them when they transit in front of their star and cause a drop in light levels,

  • or when their gravitational pull makes their star wobble.

  • But very rarely, it's possible to see them with an optical telescope and we've seen

  • about fifty this way.

  • But that number has actually gone down, because one of the first exoplanets ever directly

  • imaged vanished in 2014.

  • Now new research may explain where it went.

  • Was it destroyed by a Death Star?

  • It was the Death Star, wasn't it?

  • The planet in question was observed orbiting the star Fomalhaut, and so was named Fomalhaut b.

  • Hubble was the first to spot it in 2004 and again in 2006 as a moving dot around its star,

  • and it could have been easily missed.

  • Even though it was estimated to be as massive as three Jupiters and much brighter than other

  • exoplanets, which tend to be too small to reflect enough light for us to see, Fomalhaut b

  • is a billion times fainter than its star.

  • One astronomer called itone of the most difficult detections

  • in the history of exoplanet science.”

  • Though it was spotted in 2004 and 2006, there was some controversy over whether or not it

  • was actually an exoplanet.

  • Some things just seemed off.

  • For one thing, its orbit was highly elliptical.

  • Fomalhaut, by the way, also has a huge debris belt around it, so a false-color composite

  • image of the system taken by Hubble looks like, there's no other way of saying it,

  • the eye of Sauron

  • Then there's the fact that it didn't radiate any detectable infrared radiation.

  • Scientists expected to see some heat coming off what they assumed was a large and young

  • planet, but there wasn't any to see.

  • Nonetheless, in 2008 scientists declared it was an exoplanet visible from Earth, causing

  • much debate.

  • And then in 2014, Fomalhaut b up and vanished on us.

  • You ungrateful hunk of space rock, do you know how lucky you are? Pluto would kill to

  • be declared a planet!

  • To find out where it went, astronomers from the  University of Arizona returned to the

  • first images taken of it by Hubble in 2004 and tracked its evolution until its 2014 disappearance,

  • presumably while mutteringenhancethe whole time.

  • Over that 10-year period Fomalhaut b actually appeared to expand and fade away

  • Now, in early May of 2020, they think they have an explanation.

  • The astronomers who noticed the expansion and slow fade concluded that Fomalhaut b the

  • planet never existed in the first place.

  • Plot twist!

  • Instead they suggest it was a cloud of expanding dust that resulted from two massive planetesimals

  • smashing into each other.

  • This hypothesis would explain some outstanding questions about Fomalhaut b nicely, like the

  • elliptical shape of the orbit, and how it would fade as the small dust particles spread

  • out until they fell below Hubble's detection limit.

  • So, Fomalhaut b may not have been one of the 50 or so exoplanets we've directly imaged

  • through a telescope, but it may be something we've seen even less often.

  • We almost never directly observe collisions of massive objects like these, and based on

  • the simulations proposed by the study's authors, Hubble only just missed this collision.

  • It could be a very useful data point that helps us understand how planetary systems

  • evolve.

  • That's assuming this new explanation is in fact what we saw.

  • It's thought a dust cloud like this wouldn't be visible until a decade after the asteroid's

  • crash, disagreeing with the model the astronomers from the University of Arizona put forward

  • for Fomalhaut b's disappearance.

  • Perhaps it's something even stranger.

  • More observations from bigger and better telescopes like the long awaited James Webb could finally

  • put this mystery to bed.

  • So, what I'm hearing is the Death Star...not totally off the table yet.

  • While this new paper suggests Fomalhaut b was the result of two planetesimals colliding,

  • it's not the first time someone proposed theplanetwas actually just a cloud

  • of dust.

  • As our technology improves, we're not going to just look for exoplanets, but signs of

  • alien life as well.

  • Check out Amanda's video on the future of space-observing cameras here.

  • Make sure to subscribe to Seeker for more videos like this, and as always, thanks for

  • watching.

  • I'll see you next time.

We have gotten really good at spotting exoplanets.

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這顆系外行星突然從太空中消失,它去了哪裡? (This Exoplanet Suddenly Disappeared From Space, Where Did It Go?)

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    Summer 發佈於 2021 年 01 月 14 日
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