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It seems like something cool is always happening with Tabby’s Star.
Back in May, we got all excited because it was dimming again — and even though we haven’t
found anything out from that yet, the star is back in the news again!
According to a paper published last week in the Astrophysical Journal, astronomers might
have finally discovered part of why the star acts so strangely.
And I know what you’re hoping, but it’s still probably not an alien megastructure.
Those chances are dimming even more than the star is.
Tabby’s Star — lesser known as KIC 8462852 — is about 1300 light-years away.
It’s nicknamed after Tabetha Boyajian, who was the lead author on the first paper about it.
Since its discovery, it’s been one big mystery.
We’ve not only seen it continually dim over long periods of time, but we also keep seeing
short, randomly-timed dips in brightness.
It’s not like anything we’ve found in stars similar to what Tabby’s supposed to be.
To explain the data, people have suggested everything from broken up comets to a massive
structure built by extraterrestrials.
Now, in this new paper, astronomers are shedding a little more light on the situation, and
they did it by collecting light.
Specifically, more types of light.
Using NASA’s Spitzer and Swift telescopes and the AstroLAB IRIS public observatory in
Belgium, astronomers intermittently monitored three types of light coming from Tabby’s
Star between September 2015 and December 2016.
Those are infrared, visible, and ultraviolet light.
They found that the infrared light dimmed less than both the visible and ultraviolet
light — or in other words, that the dimming depended on the wavelength!
And that gave them some clues about what could be happening.
They concluded that this difference could be from an unevenly distributed dust cloud
orbiting Tabby’s Star about once every 700 days.
Each particle in the cloud wouldn’t be more than a few micrometers across, because anything
larger, like a megastructure, would block all wavelengths equally.
This idea is actually similar to how sunsets get their red hues: Shorter wavelengths of
light, like blue and ultraviolet, collide with tiny particles in the atmosphere and
get scattered more than longer wavelengths, like red and infrared.
So at sunset, when the Sun is lower in the sky and sunlight has to travel through more
of the atmosphere, it’s the redder light that makes it into your eyeballs.
On the other hand, when the particles in the atmosphere are too big, like with small raindrops
in clouds, all the wavelengths get blocked equally, and you get grey skies.
Now, this proposed dust cloud could explain the long-term dimming, but not everything.
Like, it doesn’t address the short, extreme dips in brightness we’ve seen, which previous
studies have suggested might be caused by comets.
It also can’t explain two brightening events — one in 2006 and one in 2014 — that another
team of astronomers may have found.
The paper hasn’t been peer-reviewed yet, so we can’t say anything for sure, but it
could throw a wrench into the works because astronomers have assumed Tabby’s Star was only dimming.
So we might be getting close to an answer, but Tabby’s Star remains a mystery for at
least a little while longer!
But speaking of astronomical mysteries, astronomers might have discovered what triggers a type Ia supernova.
According to research published last week in the journal Nature, they could be caused
by a helium nuclear explosion — which is as intense as it sounds.
Some supernovas happen when super-massive stars collapse, but a type Ia supernova happens
when a white dwarf, the remnant of an old star, gets too massive and explodes.
Usually, this happens because it’s been siphoning off matter from a companion star
in a binary system.
Type Ia supernovas are a really important tool in astronomy.
No matter where in the universe they are, the light they emit evolves following the same pattern.
That means it’s relatively easy to calculate how far away they and their galaxies are.
And studying them was actually how we found out the universe’s expansion was accelerating!
But we did all that without actually knowing what causes white dwarfs to go boom.
Now, we might have solved that mystery.
Using the Subaru telescope in Hawai’i, an international team of astronomers scanned
a large piece of the sky, looking for baby supernovas only a few days old.
In each galaxy, type Ia supernovas only happen about once per century, so they used a wide-field
camera mounted on the telescope to try and capture as many as possible.
And they found a bunch of them!
One candidate about 1.5 billion light-years away, officially called SN 2016jhr, appeared
to be only about half a day old!
That’s super young — younger than any previously studied supernovas like it.
It’s so young that the light it emitted didn’t even match what astronomers usually find.
After tracking this object’s light curve for two months, the team used a supercomputer
to try to model their observations.
According to the simulations, the star collected enough mass from its companion star that a
thin shell of helium on its surface experienced extreme temperature and pressure.
It was enough to fuse the helium atoms and create an explosion!
The resulting shockwave then traveled down into the white dwarf, causing the carbon inside
the star to ignite.
And that created the energy needed to rip the star apart in an explosion 5 billion times
brighter than our Sun.
Understanding how these explosions are triggered and what they look like just hours after starting
will be important, because it will help astronomers improve those distance measurements and how
we understand our universe’s history.
Speaking of stars, most of us know that our sun is kind of your average joe, unlike tiny
white dwarfs or huge, red giants.
Which is pretty common knowledge now, but what about way back in Greece around 200 BCE?
Our partner, Brilliant.org, has a cool lesson about how Greek astronomer Aristarchus tried
to estimate the size of the sun, and I'm going to look through it.
Brilliant’s really cool because it gives you context.
Like, instead of just giving you this math problem it’s putting you in the headspace
of an early astronomer.
Each little quiz is building on the previous one so you are applying what you learned in
the last section to this new section.
It’s fun because it’s kind of like a game and I want to win, but more than that I really
just want to know the answer and learn more about it.
So when you get a question wrong, you’re still learning a cool thing.
Thank for pretending to be Aristarchus with me and checking out Brilliant.org . If you
want to support SciShow Space and test your knowledge and try this out for yourself you
should click on the link in the description and check it out!
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