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Some of the most exciting areas of astronomy deal with the birth and death of stars.
These processes create solar systems, fill the universe with heavy elements, and create
the supermassive black holes that form the cores of galaxies—so pretty important stuff!
But since young stars, supernovas, and stellar remnants are so energetic, they give off a
lot of high-energy light—specifically X-rays.
And those aren’t detectable from Earth because our atmosphere soaks them up.
That’s why NASA built Chandra, an X-ray telescope launched in 1999, that would give
us incredible new insights into the X-ray universe.
Chandra was one of four telescopes that made up NASA’s so-called Great Observatories project.
The others—Hubble, Compton, and Spitzer—each operated in a different part of the electromagnetic
spectrum, and with the four of them, astronomers could observe just about everything that gives
off light in space.
But on top of the astronomy it made possible, Chandra was also an engineering feat—which
it had to be, because, if you’ve ever had an X-ray done on your body, you know that
X-rays go right through stuff!
So if Chandra were designed like a regular optical telescope, with a mirror or dish set
up to intercept light nearly head-on, it wouldn’t work—X-rays have so much energy that they’d
just shoot right through.
But the trick to Chandra is that if the angle is shallow enough, X-rays will glance off
a mirror instead of punching through.
So Chandra’s engineers carefully designed a set of long, nested barrels of mirrors to
gently steer X-rays onto a detector.
That made Chandra the most powerful X-ray telescope ever launched, with a sharp enough
focus to read a stop sign from around 20 kilometers away.
Since 1999, it’s turned that sharp focus on the universe and made some major discoveries
about high-energy events in space, including the processes surrounding the birth and death of stars.
For one, Chandra showed us that newborn stars play a huge role in determining the fate of
planets that form around them.
This research started back in 2003, when astronomers pointed Chandra toward the Orion Nebula, which
is full of newly-forming stars known as T Tauris.
T Tauri stars are big balls of collapsing gas—surrounded by a swirling disk—that
haven’t quite started fusing hydrogen into helium yet.
They give off a lot of X-rays, which come in flares, and astronomers found that those
flares create turbulence in the disk around them, where the planets form.
Which sounds unpleasant… but it might actually be a good thing! Because rocky planets that
form too close to their star can eventually fall into it, but this turbulence can help
push planets into a more stable orbit, even one in the habitable zone.
In addition to influencing the planets’ location, these flares also change the composition
of the disk the planets form from.
The energy they spew out drives chemical reactions that strip away electrons, change the makeup
of certain atoms, and vaporize some heavier elements.
All of which tells us that our baby Sun likely had a major effect on where we are today—and
what we and our planet are made out of!
Speaking of what we’re made out of, you may have heard that Earth’s heaviest elements
formed in a star that died as a supernova and blasted its contents into space.
And with Chandra’s help, astronomers have been able to learn a lot about exactly how
supernovas spew out their insides to enrich the space around them.
One of Chandra’s best-studied targets, and actually the first thing it ever observed,
is a supernova called Cassiopeia A.
Early observations found something that astronomers had predicted with models, but had never observed:
iron from the star’s core at the outer edges of the supernova.
It showed that supernovas turn themselves inside out when they explode.
Just how that happens is still an open question, but answering it will help us understand what
drives supernovas, and how exactly the elements produced in the supernova, both before and
during the explosion, spread through space.
After all, supernovas play a huge role in getting complex elements out into the universe
and seeding new stars and planets.
In fact, later observations of Cassiopeia A showed that this single, massive star has
produced thousands of Earths’ worth of life-forming elements like sulfur, oxygen, and phosphorus,
along with other elements important to life on Earth.
But supernovas aren’t the only way star death can fuel new growth in the universe.
Along with data from other telescopes, Chandra’s observations of black holes have revealed
that, under the right conditions, these stellar remnants may help stars form.
In 2019, scientists found a black hole almost 10 billion light-years away, in a region of
super high star formation. It lives inside a massive bubble of gas, hot enough that it’s
only visible in X-rays.
The bubble contains four whole galaxies, and it appears to be heated by the black hole’s
polar jets.
Astronomers think that the reason so many new stars are being born is because, as the
bubble expanded, it created shockwaves that compressed gases in these galaxies enough
to trigger star formation.
And this is remarkable for two reasons: First of all, the idea that a black hole in one
galaxy could trigger star formation in other galaxies is pretty incredible, but also, black
holes usually have the opposite effect on star formation.
As a black hole heats up the gas around it, that tends to prevent stars from forming,
since hotter, high-pressure gas is less likely to collapse into a star.
So, if scientists are understanding the 2019 discovery correctly, it suggests that black
holes could play a more diverse role in galactic life cycles than we expected.
And fortunately, Chandra is still going strong, so in the coming years, we’ll be able to
keep exploring mysteries like this and to better understand the X-ray universe.
Thanks for watching this episode of SciShow Space! And if you’re now a new fan of the
Chandra X-Ray Observatory—or an old one—you might like our September Pin of the Month.
It’s of Chandra, and you can order it at DFTBA.com/SciShow or find it in the description
below. But it’s only available until the end of September, so if you want one, get
yours now!
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