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If you’ve ever looked up at the night sky,
you’ve probably noticed the constellation of Orion the hunter,
whose one shoulder is marked by a bright red star called Betelgeuse.
It’s one of the most recognizable stars in the night sky.
The thing is, these days, it’s starting to look a little funny.
It’s always been super bright because it’s just 650 light-years away
and it’s mind-bogglingly big.
Seriously, our solar system out to Jupiter would fit inside of it.
That tells us this star is a red supergiant, meaning it’s at the end of its life,
and scientists believe it’s the closest star to Earth ready to explode in a massive supernova.
But since last year, scientists have noticed that Betelgeuse is dimming,
and not just a little. It’s gone from the 11th-brightest star in the sky to the 24th.
That’s enough to notice with the naked eye!
And just last week, thanks to observations from the European Southern Observatory,
we learned that this dimming is kind of lopsided.
Which has got people talking about how close Betelgeuse might actually be to that explosion.
The lopsidedness is especially weird, since astronomers usually think of stars
as objects that basically look the same from every side.
But that’s definitely not the case here.
Because Betelgeuse is so big and so close,
astronomers can study it in ways that are impossible for almost any other star.
For instance, powerful modern telescopes, like Europe’s Very Large Telescope,
can take pictures directly of its surface.
And when a team of researchers recently compared images of Betelgeuse
taken in January and December of 2019, they found a remarkable difference.
The January image, which was snapped before the recent dimming,
shows a star that’s pretty symmetric-looking.
But in the more recent photo, it’s definitely looking crooked.
Astronomers have a couple of ideas why.
One has to do with the star’s size.
Because it’s so big, the gravity at the surface of Betelgeuse is pretty weak.
That means elements in its outer layers can drift away easily,
producing massive clouds of dust.
Just like on a hazy day, that dust could be obscuring our view of the star.
Another possibility is that the whole bottom part could be covered in one giant sunspot.
Sunspots are really just cooler parts of a star’s surface,
which causes them to shine less brightly than the surrounding material.
On the Sun, spots never get even remotely close to that big,
but the physical processes happening on Betelgeuse could just be totally different.
Either way, this new image suggests that the dimming
probably isn’t a sign that Betelgeuse is about to explode.
Which is kind of too bad, since Betelgeuse is far enough away from Earth to be safe,
but close enough that its explosion would shine as brightly as the full Moon.
Which would be awesome for science but not so great for its close neighbors.
While we’re not expecting fireworks from Betelgeuse anytime soon,
scientists will stay busy exploring a whole new trove of data
from NASA’s New Horizons spacecraft.
Back on January 1st, 2019, the spacecraft flew by a tiny Kuiper Belt Object called Arrokoth,
which means “sky” in the language of the Powhatan tribe of Native Americans.
It took a while to sort out its name,
so you might’ve heard this object called MU69 or Ultima Thule in the past.
It orbits more than a billion kilometers past Pluto,
making it the farthest object ever explored by a spacecraft.
New Horizons collected most of its data over about 12 hours as it zipped past,
but it took the better part of a year to radio that information back to Earth,
so most of the findings are just starting to come out.
In a series of three papers published last Thursday in the journal Science,
mission scientists shed light on how Arrokoth and other Kuiper Belt objects may have formed.
The key was Arrokoth’s unique snowman-like shape.
It’s made up of two lobes that are neatly stuck together.
And astronomers already knew that the two parts
must have formed separately before colliding, but how that happened was a puzzle.
In one of the recent papers, computer simulations showed that,
to avoid cracking the two lobes of the snowman, the collision had to be really slow,
under about 18 kilometers per hour.
Amazingly, that small detail about the conditions at the time of Arrokoth’s formation
might have answered a big question about how planets form.
See, Arrokoth is an example of a planetesimal,
the basic building block of larger planets,
and astronomers have two basic ideas about how they form.
In one model, called hierarchical accretion,
objects start small and grow as they run into other stuff.
The other idea, known as gravitational instability,
suggests that full-sized planetesimals basically form all at once
as big clouds of gas and dust collapse.
New Horizons’ results suggest this second one is probably the right answer,
at least for the Kuiper Belt.
That’s because hierarchical accretion leads to more violent collisions,
not the slow, gentle impact that created Arrokoth.
Other New Horizons observations,
like the fact that the two lobes have the same composition,
support the idea that they formed from a gravitational instability.
After all, if they formed near each other, they'd both be made of the same stuff
and wouldn’t have to pick up much speed to collide.
Conditions in the inner solar system may have been different during planet formation,
so it’s not yet clear how broadly these conclusions apply,
but figuring it out for even the Kuiper Belt is a really big deal.
And that’s just one example of what New Horizons has uncovered.
It also searched for rings, estimated Arrokoth’s age,
and calculated how much gas might’ve been in the early Kuiper Belt.
So while it’s likely that we’ll never visit this tiny, freezing world again,
scientists now have enough data to explore its mysteries for years to come.
In the meantime, while we wait for the next set of results,
we have an odd, supergiant star to keep an eye on.
While astronomers are working on telling the story of our solar system,
there are lots of other stories waiting to be told.
Right now, I’m listening to There There by Tommy Orange which follows
12 native characters leading up to the Big Oakland Powwow in California.
My favorite character is Orvil, who teaches himself
traditional dance through YouTube videos,
but so far I’m in love with all the characters, and I think you will be too.
And I haven’t finished the story yet, so if you have, no spoilers in the comments, please!
You can find this audiobook on Audible, along with tons of other amazing stories.
Next up, I’m planning on listening to Never Home Alone by Rob Dunn
all about the critters living in your home with you.
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To get started, visit audible.com/scishowspace or text “scishowspace” to 500 500.
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