Any number of scientific discoveries or events make the "best of" lists every year. Well, our astronomy contributor Jean Creighton is no different, and she shares her picks for 2019:
First all-female spacewalk
The first all-female spacewalk took place on Oct. 18. Astronauts Christina Koch and Jessica Meir made the historic excursion.
The initial all-female spacewalk was planned in March, but it was canceled.
"What's interesting here is that the reason why the original crew didn't get to do it was because they didn't have a suit that was suitable for two women at the same time," Creighton explains.
As NASA makes new missions to the Moon and possibly even Mars, she says spacesuits will need to be made individually for each astronaut.
"Because people are going to be spending a lot of time in space, they're going to have suits that will be made to their particular size — men or women," she says.
First molecule in the universe
Now, we go from a huge spacewalk to something that's very, very, very small. After decades of searching, scientists discovered the first molecule that formed in the universe. Keep in mind, the universe is almost 14 billion years old.
Scientists believe the universe's first type of molecule is helium hydride. It's a combination of helium and hydrogen, according to NASA, and likely formed 100,000 years after the Big Bang.
"That was made in the lab in 1925, almost 100 years ago. But it was elusive. We couldn't identify it in any of the astronomical objects that we've been looking at," Creighton says.
But finally, a NASA aircraft called SOFIA (Stratospheric Observatory for Infrared Astronomy) made it possible for scientists to see helium hydride for the first time.
First photograph of a supermassive black hole
"We have been lucky in the black hole department for the last few years. This year, it was a direct image of a supermassive black hole at the center of very cool galaxy, which is called M87," says Creighton.
She says what's cool about M87 is that way before the photograph, scientists were able to see "huge lobes." Since the lobes were much larger than the galaxy, scientists were curious about how the lobes were powered.
"It turns out, at the core, as we now understand of most galaxies, of M87 there is a supermassive black hole — that as it spins, it ejects sharp jets that pile into the gas and make these balloons of gas at the intersection of where the jet hits and where clouds of material might be," she explains.