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[bright music]

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>> Preston: "What's Up" for September?

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The moon with Mars and Venus,

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and a star with a planet that wasn't.

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On September 6th, you'll find the moon

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extremely close to Mars
in the predawn sky.

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Now they were even closer
back on August 9th,

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but still a really pretty
spectacle this month.

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If you're up early and can
step outside for a look,

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they'll be only a couple of degrees apart,

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meaning they'll appear
in the same field of view

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if you look with most binoculars.

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On September 13th and 14th,
look in the east before dawn

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to see the slim crescent moon
slip past brilliant Venus.

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On the 13th, you'll find
the moon hanging above Venus

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with about 20% of its surface illuminated.

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By the next morning,
the moon has moved here

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to the left of Venus and has only about

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10% of its sunlit surface visible.

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Looking toward the south in September,

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there's really only one
relatively bright star

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for most of us who live near cities.

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That star is called Fomalhaut,

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and it's got a pretty interesting story.

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The star is about 25 light years away,

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meaning it's relatively close by.

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It's also fairly young at just
a few hundred million years,

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and it's still surrounded
by a disk of debris,

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which is a common feature for stars

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during their planet forming phase.

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Now we've discovered
thousands of exoplanets,

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planets outside our solar system,

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but Fomalhaut appeared
to be the first star

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to have a planet detected
by direct imaging

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with a telescope; that being
the Hubble Space Telescope.

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Astronomers announced
the find back in 2008.

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So Fomalhaut had itself a planet,

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but this is where it gets interesting.

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As the planet had a funky orbit,

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wasn't giving off excess heat
like a young planet should,

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and proceeded to grow fainter

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over the several years that followed,

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disappearing by 2014.

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In April, 2020 another team of astronomers

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using Hubble announced their finding

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that Fomalhaut's planet
wasn't a planet after all.

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In fact, their study
showed what Hubble detected

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was likely a giant
expanding cloud of debris

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resulting from a huge
collision of two small bodies

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made of dust and ice,

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similar to worlds you might
find in our own Kuiper Belt.

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The scientists calculate
collisions like this happen

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around Fomalhaut only every
couple hundred thousand years.

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So Hubble just happened to
be looking at the right time

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not long after the collision took place.

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So we may have lost a planet,
but we gained a cool insight

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into how planetary
systems form and evolve.

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You can find Fomalhaut low in the south

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a couple of hours after sunset

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to the left of the bright
pair of Saturn and Jupiter.

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Since it's bright and low in the sky,

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it's sometimes appears to flicker

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from atmospheric turbulence.

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That can cause some sky watchers to wonder

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just what the heck it is.

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Now you know. It's Fomalhaut.

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The nearby star where
it appears we witnessed

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a dramatic planetary collision.

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Here are the phases of
the moon for September.

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You can catch up on all of NASA's missions

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to explore the solar system
and beyond at nasa.gov

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I'm Preston Dyches from NASA's
Jet Propulsion Laboratory.

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And that's "What's Up" for this month.