One of the coolest things about astronomy is that just by looking out into space, you
can look back in time.
You can still see stars shining thousands of years after they exploded, and intergalactic
collisions that ended billions of years ago.
And if you look even further, you can see some of the first stars and galaxies in the
universe -- the earliest ancestors of big galaxies like our very own Milky Way.
All of that, just from looking up at the sky.
One of those early galaxies is known as the Himiko blob.
And it’s pretty weird, as blobs go.
It’s huge, it’s bright, and it’s really, really old.
Himiko was discovered back in 2009 by a team of Japanese astronomers, who named it after
a third-century Japanese queen.
But even though they detected it using a telescope in Hawaii, Himiko’s light originally wouldn’t
have been able to make it through our atmosphere.
Himiko is a type of early galaxy called a Lyman alpha blob, after the particular type
of ultraviolet light that its gas gives off.
If the blob were nearby, that light would get blocked by Earth’s protective ozone
layer long before it reached the ground.
And astronomers never would’ve seen it.
But luckily for them, Himiko isn’t nearby.
It’s so far away that its light took 12.9 billion years to reach Earth, meaning that
Himiko formed just 800 million years after the universe began in the Big Bang.
Himiko is so old that it has almost no heavy elements like carbon, which form as stars
die.
So all of Himiko’s stars are from the first generation of stars in the universe.
Over those 12.9 billion years of traveling, Himiko’s light was redshifted.
Space itself expanded underneath the light, stretching it from short-wavelength ultraviolet
light all the way to much longer-wavelength infrared.
And infrared light can pass through the atmosphere just fine, which is why the team could observe
this ancient cloud.
But with great age came great mysteries, at least at first.
Because Himiko seemed to challenge the way that we think galaxies built up in the early
universe.
The traditional story had been that smaller clouds of gas merged again and again, gradually
producing bigger and bigger galaxies over the course of the first couple billion years
of the universe’s history.
But Himiko was the oldest Lyman alpha blob ever discovered, and it was also the biggest
thing ever discovered from when the universe was so young.
It was already half the size of the Milky Way, and ten times more massive than any other
galaxy we’ve ever found from that era.
Which was confusing.
Astronomers realized that if something that big could’ve formed before things started
merging, either galaxies today should be much bigger or we’re missing something major
about the way the universe evolved.
To make things even weirder, Himiko seemed like it was forming an incredible number of
stars for its size, making it much brighter than astronomers would expect.
They needed to take a closer look at this weird blob.
So that’s exactly what an international team of astronomers did back in 2013, in a
study published in the Astrophysical Journal.
Using the combined powers of the Hubble Space Telescope and the ALMA observatory in New
Mexico, they found that Himiko isn’t just one large cluster like everyone thought.
It’s actually three merging clouds, and each cloud is about the size you’d expect
objects to be from so soon after the Big Bang.
So that’s one mystery solved: A rare early collision between three young galaxies produced
Himiko, which fit perfectly with what astronomers expect about that era of the universe.
And the mergers actually solved the other mystery, too.
When gas clouds collide, huge amounts of gas get forced together, triggering rapid star
formation — just like astronomers saw in Himiko.
That’s why it was so bright.
Himiko was one of those mysteries where scientists saw something that didn’t make sense yet
and weren’t sure what was going on.
But with more data, they solved it!
Blobs like Himiko still have a lot to teach us about the universe and the kinds of collisions
that produced large galaxies.
But, at least for now, they’re no longer making astronomers scratch their heads in
confusion.
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