2019 was a big year for astronomy.
We learned what Voyager 2 is seeing in interstellar space, a Japanese robot landed on an asteroid,
and a Chinese spacecraft became the first-ever to touch down on the far side of the moon.
But 2019 will be best remembered as the year of the black hole
...and no, that’s not a metaphor.
On April 10th, the internet lit up with the first-ever direct image of a black hole,
specifically Messier 87, a supermassive black hole 55 million light years away.
To capture the image, researchers used the Event Horizon Telescope,
an eight-telescope project designed exactly for that purpose.
The EHT doesn’t take photos like a traditional camera would—instead, all eight telescopes
sync up to look at the radiation given off by black holes.
There’s a lot going on in this image of M87.
You can see the photon sphere, the accretion disk, and the event horizon, the visible point
of no return where nothing can escape the black hole’s gravitational force.
Being able to see and study black holes in this way will let us test scientific theories
like Einstein’s general relativity, which dictates how things move through space.
Using the EHT, we can watch how gravity-driven warps in spacetime impact how light travels.
Plus, it proved that this technology actually works and it can be used again.
The picture of M87 is a compilation of data captured over four days in 2017.
It took more than two years to process, partially because of the enormous size of the files—
the image is made up of more than 5,000 terabytes of data.
That sheer size of the information meant the files couldn’t be transferred digitally—
physical hard drives had to be taken from the observatories to the scientists.
In fact, the dataset in Antarctica took months to retrieve because of bad weather.
Though the image is an incredible accomplishment, it lacks sharpness in part because it had
to be compressed a million times over.
However, advances in technology, like using additional telescopes and new algorithms,
may help to speed up the process and sharpen future images.
Next, you may remember the name LIGO.
It stands for the Laser Interferometer Gravitational-Wave Observatory.
Three years ago, it observed ripples in spacetime called “gravitational waves”—
the same ones Einstein predicted.
Those ripples were caused by two black holes merging, which produced a signature “chirp” sound.
Fast-forward to 2019—just weeks after that picture of M87 was released—and LIGO may
have witnessed signs of a black hole slamming into a neutron star.
That's something scientists were never sure was even possible.
Here’s what happened.
On April 25th and 26th, LIGO, as well as Italy’s Virgo interferometer, detected two sets of
gravitational waves.
The latter seemed to come from a rare black hole-neutron star merger.
The collision probably happened about 1.2 billion light-years away, but that’s almost
all we know about it.
The team is still studying the results, and if the event is confirmed, it could start
a whole new field of astrophysics.
Before the year could come to a close, black holes managed to
sneak into the news one more time in October.
We’ve all heard of a wormhole—the mainstay of Star Trek and other sci-fi that can transport
a ship millions of light years in a fraction of a second.
They could exist under Einstein’s theory of gravity, but only black holes have the
oomph required to actually sculpt one.
The difference between the two is that a black hole simply crushes any matter that gets sucked
into its gravitational pull; a wormhole is like a tunnel, with a destination on either
side that can be traveled between.
And if we thought we found a wormhole, we could test it by sending a probe through.
But—unlike the film Interstellar—it would take millenia for any spacecraft to reach the nearest candidates.
So, instead, two theoretical physicists from China and the U.S. have been conducting a thought experiment.
They worked within the framework of Einstein’s laws of gravity to figure out if it’s even
possible for a big, stable wormhole to exist.
Their conclusion: it could happen, but only if the hole is kept open by the force driving
the expansion of the universe.
So, how do you discover a wormhole without actually going there?
You need to look at the stars orbiting it.
In fact, the duo previously hypothesized that stars circling a wormhole would wiggle in
a very specific way—a dance, if you will.
That’s because unlike a black hole, a wormhole could have something on the other side,
causing a slight gravitational pull on the stars on the other end.
Now, they are exploring what the effects would be like—and looking for dancing—on a specific
star called S2, which orbits Sagittarius A*, the supermassive black hole at the center of our galaxy.
But don’t get too excited, remember this is all theoretical.
Despite decades of advancements in the field of astrophysics, our tools and data still
aren’t precise enough to measure such movements.
In fact, they’d need to be 100 times more precise—a goal the team believe experiments
should reach in the coming decades.
Once that happens, we’ll be able to see if S2 is dancing or not.
For now, all we can do is wait.
What will 2020 be the year of?
Funghi?
Coral reefs?
Something else?
Let us know in the comments below.