Readers may recall when we covered the first detection of gravitational waves from space, heralding a new era in astronomy. It was big news. Now, a second detection has been announced.
From NASA’s Astronomy Picture of the Day: (h/t to Dr. Leif Svalgaard)
A new sky is becoming visible. When you look up, you see the sky as it appears in light — electromagnetic radiation. But just over the past year, humanity has begun to see our once-familiar sky as it appears in a different type of radiation — gravitational radiation. Today, theLIGO collaboration is reporting the detection of GW151226, the second confirmed flash of gravitational radiation after GW150914, the historic first detection registered three months earlier.
As its name implies, GW151226 was recorded in late December of 2015. It was detected simultaneously by both LIGO facilities in Washington and Louisiana, USA. In the featured video, an animated plot demonstrates how the frequency of GW151226 changed with time during measurement by the Hanford, Washington detector. This GW-emitting system is best fit by two merging black holes with initial masses of about 14 and 8 solar masses at a redshift of roughly 0.09, meaning, if correct, that it took roughly 1.4 billion years for this radiation to reach us.
Note that the brightness and frequency — here mapped into sound — of the gravitational radiation peaks during the last second of the black hole merger. As LIGO continues to operate, as its sensitivity continues to increase, and as other gravitational radiation detectors come online in the next few years, humanity’s new view of the sky will surely change humanity’s understanding of the universe.
Added: I had an interesting discussion with Dr. Leif Svalgaard about gravity that I thought was worth sharing since I found the topic fascinating.
On Wed, Jun 15, 2016 at 10:52 AM, Anthony Watts wrote:
I wonder, what is the speed of Gravity waves?
From: Leif Svalgaard
Sent: Wednesday, June 15, 2016 12:04 PM
To: Anthony Watts
Subject: Re: GW151226: A Second Confirmed Source of Gravitational Radiation
The same theory that predicts them [GR] also predicts that they propagate with the speed of light.Gravitational waves are ‘ripples’ in the fabric of space-time caused by some of the most powerful processes in the universe – colliding black holes, exploding stars, and even the birth of the universe itself. Albert Einstein predicted the existence of gravitational waves in 1916, derived from his general theory of relativity. Einstein’s mathematics showed that massive accelerating objects (such as neutron stars or black holes orbiting each other) would disrupt space-time in such a way that waves of distorted space would radiate from the source. These ripples travel at the speed of light through the universe, carrying information about their origins, as well as clues to the nature of gravity itself.
On Wed, Jun 15, 2016 at 12:08 PM, Anthony Watts wrote:
Yes, but how does the universe have gravitational cohesion at that speed? Maybe the waves are speed of light, but the effect of gravity across distance must be instantaneous, otherwise how would galaxies manage to form or stay together?
On Wed, Jun 15, 2016 at 12:24 PM, Leif Svalgaard wrote:
The effect of gravity is not instantaneous. We know this because the finite speed is needed be make the predicted positions of planets [and spacecraft] come out right.
Galaxies form because the gravity of Dark Matter helps to draw the intergalactic matter together.
Note: several updates were made to this story about an hour after publication, to correct the title, to replace “gravity waves” with “gravitational waves” so that they weren’t confused with the meteorological term “gravity waves” which I’ve always thought was wrongly named, and to add some new discussion I had with Dr. Svalgaard about the speed of gravity. Also added was an illustration. I’m sorry for the issues, I had partially written the story and set it to auto-publish hours ahead, and then I got distracted by a phone call and didn’t complete the story before it published.