Birth of a black hole or neutron star captured for first time

January 10, 2019, Northwestern University
A look at The Cow (approximately 80 days after explosion) from the W.M. Keck Observatory in Maunakea, Hawaii. The Cow is nestled in the CGCG 137-068 galaxy, 200 million light years from Earth. Credit: Raffaella Margutti/Northwestern University

A Northwestern University-led international team is getting closer to understanding the mysteriously bright object that burst in the northern sky this summer.

On June 17, the ATLAS survey's twin telescopes in Hawaii found a spectacularly bright anomaly 200 million away in the Hercules constellation. Dubbed AT2018cow or "The Cow," the object quickly flared up, then vanished almost as quickly.

After combining several imaging sources, including hard X-rays and radiowaves, the multi-institutional team now speculates that the telescopes captured the exact moment a star collapsed to form a compact object, such as a black hole or neutron star. The stellar debris, approaching and swirling around the object's event horizon, caused the remarkably bright glow.

This rare event will help astronomers better understand the physics at play within the first moments of the creation of a black hole or neutron star. "We think that 'The Cow' is the formation of an accreting black hole or neutron star," said Northwestern's Raffaella Margutti, who led the research. "We know from theory that black holes and form when a star dies, but we've never seen them right after they are born. Never."

Margutti will present her findings at the 233rd meeting of the American Astronomical Society on Jan. 10 in Seattle. The research will then be published in the Astrophysical Journal.

Margutti is an assistant professor of physics and astronomy in Northwestern's Weinberg College of Arts and Sciences and a member of CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics), an endowed research center at Northwestern focused on advancing astrophysics studies with an emphasis on interdisciplinary connections.

The curious Cow

After it was first spotted, The Cow captured immediate international interest and left astronomers scratching their heads. "We thought it must be a supernova," Margutti said. "But what we observed challenged our current notions of stellar death."

For one, the anomaly was unnaturally bright—10 to 100 times brighter than a typical supernova. It also flared up and disappeared much faster than other known star explosions, with particles flying at 30,000 kilometers per second (or 10 percent of the speed of light). Within just 16 days, the object had already emitted most of its power. In a universe where some phenomena last for millions and billions of years, two weeks amounts to the blink of an eye.

"We knew right away that this source went from inactive to peak luminosity within just a few days," Margutti said. "That was enough to get everybody excited because it was so unusual and, by astronomical standards, it was very close by."

Using Northwestern's access to observational facilities at the W.M. Keck Observatory in Hawaii and the MMT Observatory in Arizona, as well as to the SoAR telescope in Chile, Margutti took a closer look at the object's makeup. Margutti and her team examined The Cow's chemical composition, finding clear evidence of hydrogen and helium, which excluded models of compact objects merging—like those that produce gravitational waves.

Comprehensive strategy

Astronomers have traditionally studied stellar deaths in the optical wavelength, which uses telescopes to capture visible light. Margutti's team, on the other hand, uses a more comprehensive approach. Her team viewed the object with X-rays, hard X-rays (which are 10 times more powerful than normal X-rays), radio waves and gamma rays. This enabled them to continue studying the anomaly long after its initial visible brightness faded.

After ATLAS spotted the object, Margutti's team quickly obtained follow-up observations of The Cow with NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and INTEGRAL hard X-ray laboratories, soft X-rays at XMM-Newton and radio antennae at the Very Large Array toward The Cow.

Margutti attributes The Cow's relative nakedness to potentially unraveling this intergalactic mystery. Although stars might collapse into black holes all the time, the large amount of material around newly born blocks astronomers' vision. Fortunately, about 10 times less ejecta swirled around The Cow as compared to a typical stellar explosion. The lack of material allowed astronomers to peer straight through to the object's "central engine," which revealed itself as a probable black hole or neutron star.

"A 'lightbulb' was sitting deep inside the ejecta of the explosion," Margutti said. "It would have been hard to see this in a normal stellar explosion. But The Cow had very little ejecta mass, which allowed us to view the central engine's radiation directly."

Galactic neighbor

Margutti's team also benefited from the star's relative closeness to Earth. Even though it was nestled in the distant dwarf galaxy called CGCG 137-068, astronomers consider that to be "right around the corner."

"Two hundred million light years is close for us, by the way," Margutti said. "This is the closest transient object of this kind that we have ever found."

Margutti's team at Northwestern includes graduate student Aprajita Hajela, postdoctoral fellows Giacomo Terreran, Deanne Coppejans and Kate Alexander (who is a Hubble Fellow), and first-year undergraduate student Daniel Brethauer.

"Being given the opportunity to contribute to something as cutting edge and international as understanding AT2018cow as an undergrad is a surreal experience," Brethauer said. "To have helped the world's experts figure out what AT2018cow is even in the smallest way was beyond my wildest expectations at the beginning of the summer and something that I will remember for the rest of my life."

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23 comments

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Display comments: newest first

Whydening Gyre
5 / 5 (4) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
Benni
2.2 / 5 (10) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
....."more" what? Stars? Aren't billions already plenty enough?
Whydening Gyre
4.4 / 5 (9) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
....."more" what? Stars? Aren't billions already plenty enough?

C'mon benni..
more events like this...
Benni
2.2 / 5 (10) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
....."more" what? Stars? Aren't billions already plenty enough?
C'mon benni..
more events like this...
Oh, you mean the galaxies hosting the billions of stars.
Da Schneib
4.2 / 5 (15) Jan 10, 2019
The vaguer you are, the more Benni will take advantage of you. Standard troll methodology.
Whydening Gyre
4.6 / 5 (9) Jan 10, 2019
The vaguer you are, the more Benni will take advantage of you. Standard troll methodology.

DS,
He perceives himself a teacher...
Kinda like RC does...
Surveillance_Egg_Unit
1.8 / 5 (10) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
....."more" what? Stars? Aren't billions already plenty enough?

C'mon benni..
more events like this...
says Whyde

How hard was it for you to be more specific and type: "more events like this" in your first post? Benni was puzzled - I was puzzled - everyone who reads it will go away scratching their heads, wondering. Why, even Da Pussyman was puzzled enough to let you know how vague you are.
Whydening Gyre
4.2 / 5 (5) Jan 10, 2019
The vaguer you are, the more Benni will take advantage of you. Standard troll


From an "arttist" viewpoint, it's up to guys to figure out what I mean... :-)
Surveillance_Egg_Unit
1.8 / 5 (10) Jan 10, 2019
ahaaa the Mona Lisa syndrome, eh?
jimmybobber
4.4 / 5 (14) Jan 10, 2019
@Benni and @SEU Do you seriously not understand what Whydening Gyre was referring to by "With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more..."
more "Births of a black holes or neutron stars"
The subject of the article!
Whydening Gyre
4 / 5 (8) Jan 10, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...
....."more" what? Stars? Aren't billions already plenty enough?

C'mon benni..
more events like this...
says Whyde

How hard was it for you to be more specific and type: "more events like this" in your first post? Benni was puzzled - I was puzzled - everyone who reads it will go away scratching their heads, wondering. Why, even Da Pussyman was puzzled enough to let you know how vague you are.

Thank you, Mr. Specificity...
Whydening Gyre
4.6 / 5 (10) Jan 10, 2019
@Benni and @SEU Do you seriously not understand what Whydening Gyre was referring to by "With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more..."
more "Births of a black holes or neutron stars"
The subject of the article!

Thanks, JB.
More than likely, they didn't...
At least not the title...
Whydening Gyre
4.2 / 5 (5) Jan 11, 2019
ahaaa the Mona Lisa syndrome, eh?

aaaannndddd…
what do you mean by that?
Surveillance_Egg_Unit
3 / 5 (6) Jan 11, 2019
ahaaa the Mona Lisa syndrome, eh?

aaaannndddd…
what do you mean by that?


The Mona Lisa syndrome is that which is claimed that the eyes of the Mona Lisa painting follow the viewer whether the viewer moves to the left or right. It has been disproven to be the case. However, there are some who will swear that it is true. I have seen artworks that do employ the use of tricks of colour, light and shadow to make one imagine that eyes are moving in a painting.
Surveillance_Egg_Unit
3 / 5 (4) Jan 11, 2019
double post
Surveillance_Egg_Unit
2 / 5 (8) Jan 11, 2019
@Benni and @SEU Do you seriously not understand what Whydening Gyre was referring to by "With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more..."
more "Births of a black holes or neutron stars"
The subject of the article!
says jimmybobber

Whyde has already explained in a post above that the end of the post was "I'm surprised that we haven't seen 'more events like this'". You're too late, jimmybobber. But it was nice of you to come to the aid of our artist-in-residence.
Surveillance_Egg_Unit
2.6 / 5 (5) Jan 11, 2019
@Whyde

https://phys.org/...ked.html

Mona Lisa Effect not Syndrome
antialias_physorg
4.2 / 5 (10) Jan 11, 2019
With trillions of galaxies containing billions of stars, I'm surprised we haven't seen more...

Doesn't happen everyday. And when it does it's not guaranteed that we see it. Astronomy is a lot of luck looking at the correct patch of sky at the correct time. Telescope focus is super-narrow (i.e. the patch a telescope is looking at at any one time is super small)

Be thankful that we don't see more of them - because that would mean it would be more likely that one of those happens close by (within 100 light years or so) within a reasonable timeframe. And we *definitely* don't want that.
Da Schneib
4.4 / 5 (7) Jan 11, 2019
@anti, troo dat. Our biggest threat is the OB association of Scorpius-Centaurus, about 400 light years away.
rrwillsj
4.4 / 5 (7) Jan 11, 2019
The woocultistsboys have nothing with which to refute the findings of the research. Probably nodded off by the end of the first paragraph in the article.

So they play childish indignation.

H\ey! That's MY gig!
rickofricks
4.4 / 5 (7) Jan 12, 2019
I want to know why.
Why so many idiots appear on this site and comment now.
Worst rated comments used to be rebellious thoughts with unique ideas in them.
Not gibberish gobble gook! Or the 'derr' idiots.
jonesdave
5 / 5 (6) Jan 12, 2019
I want to know why.
Why so many idiots appear on this site and comment now.
Worst rated comments used to be rebellious thoughts with unique ideas in them.
Not gibberish gobble gook! Or the 'derr' idiots.


There are a lot of idiots around, all trying to peddle their own pseudoscientific nonsense. Simple as that.
NeMaTo
1 / 5 (1) Jan 13, 2019
Don't feed the trolls.

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