LIGO Does It Again: A 2nd Robust Binary Black Hole Coalescence-Observed (Practical) -

LIGO Does It Again: A 2nd Robust Binary Black Hole Coalescence-Observed (Practical)

The two LIGO gravitational wave detectors in Hanford Washington &  Livingston Louisiana have wedged a second healthy signal from two black holes in their last orbits and then their coalescence into a solitary black hole. This occasion, dubbed GW151226, was see on December 26th at 03:38:53 (in Universal Coordinated Time, also recognized as Greenwich Mean Time), close to the end of LIGO's first observing period ("O1"), and was immediately nickname "the Boxing Day occasion".
Like LIGO's first discovery, this event was identified within minutes of the gravitational wave's transitory. Subsequent careful study of the instruments and environment around the observatories show that the signal seen in the two detectors was truly from distant black holes – some 1.4 billion light years away, by accident at about the same distance as the first signal ever detect. The Boxing Day event differ from the LIGO's first gravitational wave surveillance in some important ways, however.

    The gravitational wave at home at the two detectors at almost the similar time, indicating that the source was located anywhere in a ring of sky concerning midway between the two detectors. Knowing our detector sensitivity pattern, we can put in that it was a bit additional likely overhead or underfoot in its place of to the West or the East. With only two detectors, though, we can't narrow it down much more than that. This differs from LIGO's 1st detected signal (GW150914, from 14 September 2015), which come from the 'southeast', hitting Louisiana's detector previous to Washington's.
    The two amalgamation black holes in the Boxing Day occasion were less massive (14 and 8 times the mass of our sun) than those experiential in the first detection GW150914 (36 and 29 times the mass of our sun). While this complete the signal weaker than GW150914, when these lighter black holes merged, their signal shift into higher frequencies bringing it into LIGO’s responsive band earlier in the merger than we experiential in the September happening. This allowed us to observe additional orbits than the first detection–some 27 orbits over concerning one second (this compares with presently two tenths of a second of surveillance in the first detection). Combined, these two factors (smaller masses and more experiential orbits) were the keys to enabling LIGO to notice a weaker signal. They also allowed us to make more exact comparisons with General Relativity. Spoiler: the sign agrees, again, perfectly with Einstein’s theory.
    Last but not slightest, the Boxing Day event revealed that one of the first black holes was spinning like a top! – and this is a first for LIGO to be clever to state this with self-assurance. A spinning black hole suggests that this thing has a different history –- e.g. maybe it 'sucked in' mass from a friend star before or after in trouble from a star to form a black hole, receiving spun-up in the process.

With these two long-established detections, along with a third likely detection complete in October 2015 (believed also to be cause by a pair of merging black holes--see our paper draft on Black Hole Binaries in O1 for extra information) we can now create to estimate the rate of black hole coalescences in the Universe base not on theory, but on genuine observations. Of course with just a few signals, our estimate has big uncertainties, but our top right now is somewhere between 9 and 240 binary black hole coalescences per cubic Gigaparsec per year, or concerning one every 10 years in a volume a trillion times the quantity of the Milky Way galaxy! Happily, in its first few months of process, LIGO’s advanced detectors were sensitive sufficient to probe deeply enough into space to see about one occasion every two months.

Our next observe interval – Observing Run #2, or "O2" – will start in the Fall of 2016. With improved sensitivity, we expect to see additional black hole coalescences, and perhaps detect gravitational waves from other source, like binary neutron-star mergers. We are also looking onward to the Virgo detector joining us later in the O2 run. Virgo will be extremely helpful in locating source on the sky, collapsing that ring down to a patch, but also serving us understand the source of gravitational waves.

LIGO release its data to the public. This open-data policy allows others to examine our data, thus ensure that the LIGO and Virgo collaborations did not miss no matter which in their analyses, and in the hopes that others will find even more attractive events. Our data are shared at the LIGO Open Science Center. GW151226 has its own sheet there.

We encourage you to stroll around the LIGO Laboratory web page where you will discover graphics to help you understand the Boxing Day observation, relations to the press release, and pointers to technical papers if you would like to dig in even deeper. There you will also discover links to the LIGO Scientific Collaboration website, and to our sister collaboration, Virgo, both of which are middle to these scientific- results.

LIGO Does It Again: A 2nd Robust Binary Black Hole Coalescence-Observed (Practical)

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