More ripples in space time detected, casting light into black holes
Welcome to a new era in astrophysics.
A huge international team of scientists have just announced the discovery of yet another gravitational wave signal sent out by the violent collision of two black holes circling each other 3 billion light-years away and felt on Earth on Jan. 4.
By using the Laser Interferometer Gravitational-wave Observatory (LIGO), scientists were able to observe the gravitational waves — literal ripples in the fabric of space and time — as they passed through Earth, and all of us, marking just the third time we’ve seen evidence of these invisible waves in space.
The new finding is detailed in a study published this week in the journal Physical Review Letters.
These discoveries allow scientists to parse out exactly what’s going on with the most powerful explosions in our universe, illuminating a way to understand the cosmos as we’ve never had before.
The detections are also answering some seemingly basic questions.
“Before our discoveries, we didn’t even know for sure that black holes existed,” Laura Cadonati, LIGO team member, said during a press conference. “What we do know now is that they do exist and may have played an important role in our early universe.”
This third detection — which comes after the first in September 2015 and the second in December 2015 — appears to be the result of two black holes merging and forming a new black hole about 49 times the mass of the sun.
Researchers are also starting to piece together the story of how black holes actually do collide, whether they start off as huge stars not far from one another or are black holes in a tight pair.
While there are still many questions yet to answer, this new detection fills in a gap in black hole knowledge for scientists studying them.
“We have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses — these are objects we didn’t know existed before LIGO detected them,” LIGO’s David Shoemaker, said in a statement.
So, what are gravitational waves?
The best way to visualize gravitational waves moving through the universe is to imagine two bowling balls on a sheet lying flat on a bed.
As those two bowling balls — which represent black holes in this analogy — spin around one another, they create ripples in the sheet. Those are gravitational waves.
When the bowling balls finally converge, if they were black holes, they would orbit one another closely, creating gravitational waves and then merging together.
LIGO — which is composed of two observatories located in Washington and Louisiana — was able to detect these ripples in space-time thanks to the extreme sensitivity of the instruments.
The two identical observatories are L-shaped tubes with a laser running through them. Mirrors are positioned at the end of each arm, with another mirror in the middle.
Researchers are able to monitor the laser at it moves through the tubes and they know exactly when it should hit back at the middle. If a gravitational waves comes by, however, the laser will be ever so slightly off.
And we do mean slightly.
The length of the tube will only change by a fraction of a proton as the gravitational wave passes.
This whole thing works because light isn’t affected by gravitational waves. While the powerful waves in space can warp matter of all kinds, light remains unchanged.
The future of LIGO
Scientists expect that LIGO should be able to detect other types of cosmic collisions as its sensitivity increases in the future.
For examples, researchers hope that they will be able to pick up the relatively faint gravitational wave signals from neutron stars colliding, helping them learn more about the dense objects light-years from Earth.
By studying gravitational waves, scientists now have access to a brand new way to understand the universe.
Instead of simply studying objects through the light they emit, gravitational waves actually allow us to probe the deeper structure of the objects that created them. Through looking at the signal from these two merging black holes, for example, scientists were able to figure out their masses and the general part of the sky where they formed.
And as scientists learn more and more about gravitational waves, they should also figure out the answers to questions they didn’t even know to ask.
“You build an instrument for things you want to measure, and then you see things that you didn’t expect to see,” LIGO researcher Nergis Mavalvala said during a February interview.
“I think that’s the true promise of these instruments.”