Traveling across the fabric of spacetime as two black holes merge
Space news (February 18, 2016) – It took a hundred years, but Einstein must be smiling, wherever he is –
Astronomers working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) recently announced they had observed the ripples of gravitational waves in space-time as predicted by Albert Einstein in his ground-breaking general theory of relativity in November of 1915.
Using two LIGO ground-based observatories in Livingston, Louisiana, and Hanford, Washington, astrophysicists observed gravitational waves within the range of 10 to 1,000 cycles per second (10 to 1,000 Hz). LIGO is the most sensitive instrument ever devised by man but is only sensitive to gravitational waves within this narrow band of frequencies and specific source types.
Astronomers believe the gravitational waves observed by LIGO were produced in the final moments of the merger of two black holes into a single, spinning monster black hole. The collision and eventual merger of black holes were predicted by scientists, but this is the first time it has been observed as it happened. You can watch and learn more about astronomers simulations of two black holes merging here.
Astronomers estimate these black holes had masses of about 29 and 36 times the mass of Sol when this event happened about 1.3 billion years ago. At the time of gravitational waves were produced, about three times the mass of our sun was converted in a fraction of a second. In a brief moment of time, astronomers estimate about 50 times the total power output of all the suns in the universe was emitted.
In this case, astronomers estimate two black holes around 150 meters in diameter, with 29 and 36 times the mass of Sol, collided at nearly half the speed of light and produced the gravitational waves observed. All estimates of size, mass, and other parameters made using LIGO have a significant plus/minus, so the numbers provided should be taken with a grain of salt, or two.
General relativity predicts these black holes collided into each other at almost fifty percent the speed of light. The collision forms a single, more massive black hole, but a portion of the combined mass of the black holes was converted to energy according to Einstein’s E = mc2. It was this energy that was emitted and observed by LIGO as a strong burst of gravitational waves, producing the violent storm in spacetime detected.
Doors to a new cosmos open
This news kicks open doors to a new branch of astrophysics, well refer to as gravitational astronomy, scientists have dreamed of exploring for over 50 years. Astronomers expect this young branch of astronomy to offer information capable of opening doors that will allow us to view the cosmos in ways the study of electromagnetic radiation hasn’t allowed. It will also complement the things we have learned about the cosmos through the detection and study of electromagnetic radiation.
The next phase of gravitational wave observation will be to design and engineer space-based systems to allow us a better view through our new window on the universe. Space-based systems can detect gravitational waves at frequencies from 0.0001 to 0.1 Hz and a bigger range of source types. NASA and the European Space Agency (ESA) are currently developing concepts for space-based observatories capable of detecting gravitational waves.
The ESA and NASA are currently developing the first space-based gravitational wave observatory eLISA, which will allow astronomers to directly observe the universe using gravitational waves. eLISA will allow us to listen to the universe in gravitational waves and observe the interesting sources of gravitational waves in the cosmos.
Essentially a high precision laser interferometer in space with an arm length of 1 million km, eLISA will open even more doors and windows to the gravitational universe and extend the cosmic horizon. This important mission extends the spectrum of gravitational waves astronomers want to study.
The ESA’s LISA Pathfinder mission, in partnership with NASA, is currently getting ready to demonstrate technologies expected to be used in future space-based gravitational observatories. LISA Pathfinder is currently at the L1 LaGrange point, about 1.5 million km in the direction of Sol, and is preparing to begin its science mission.
LISA Pathfinder was made to test the theory that free particles follow geodesics in spacetime, which is a key idea behind the design and engineering of gravitational wave detectors. Scientists had to design and engineer new technologies that allow them to track two test masses nominally in free fall, using picometer resolution laser interferometry.
You can learn more about NASA here.
Discover the mission of eLISA here.
Learn more about the LISA Pathfinder mission here.
Learn more about LIGO here.
Learn more about the ESA here.