Lightweight black hole merger detected, offering new insight into gravity
by Graham Templeton
The twin LIGO (Laser Interferometer Gravitational wave Observatory) detectors on either side of the continent have produced a new, fascinating result: not only have they spied a new black hole collision to add to the still-tiny list of confirmed gravitational events, but they’ve proven that the two black holes involved are quite a bit lighter than before, just 14 and eight times the mass of our Sun, respectively. That’s helpful for a number of reasons, not the least of which because it provides significantly more data for analyze — a whole second!
That single second represents a truly incredible period of time. The waves that LIGO detected are the result of two black holes spiraling in to meet one another, and because they’re lighter than the black holes that produced the historic readings from a few months ago, they went through that process much more slowly. It turns out that the black holes from the original detection were probably actually born within the same star, and so the period of time from their birth to their merger was essentially nil.
But these two lighter black holes spend about a second in the “sensitive band” of the frequency spectrum, creating gravitational waves LIGO can detect. That corresponds to about 27 revolutions, meaning that these two enormous celestial bodies were, by the end, completing an orbit of one another in just 0.037 seconds — unfathomable.
This marks the beginning of gravitational waves as a real field of study, rather than a single, binary proof. With two data points detected in such quick succession, (just a few months apart) the researchers can start to make some inferences about how often the Earth is being bombarded with this sort of information. The events reported this week occurred some 1.4 billion years ago, and the ripples have been traveling through space ever since. We’re used to the idea of light traversing such incredible distances, but the idea that the universe is constantly pulsating with passing gravitational waves is somehow more alien.
“Dark” events like colliding black holes offer crucial insight into the invisible world of gravity, which is an increasingly interesting area for physicists. It’s not just that dark matter seems to interact with regular matter solely through the medium of gravity, but that the frontiers of physics increasingly demand the most extreme forces in the universe. The Large Hadron Collider is one thing — the most energetic collisions ever created by man — but the universe itself is capable of forces that dwarf such paltry inventions. And as we discover the frequency with which the echoes of these violent events are reaching us, it’s becoming clear just how much insight we could gain by looking into black holes.
LIGO will open a third observatory soon, in Tuscany, called the Advanced Virgo Interferometer. This is actually a long-standing gravitational wave detector, but when it re-opens in late 2016 it will be some 10 times more sensitive than it was before — sensitive enough to usefully add to LIGO’s measurements, and significantly increase the volume of space the new three-pronged global device can probe for new black holes collisions.
And who knows what we’ll find then? Gravitational wave science could tell us about the nature of black holes, or the nature of gravity. It could help map dark matter or look into the origin of the universe. This is a bit like watching the first early discoveries of telescopes — but since this is the modern age, we get new revolutionary updates on the order of months, not decades.
The next such increase in fidelity should come with the opening of the Virgo component of the LIGO array, in the second half of 2016.
Note: This article was originally published on ExtremeTech.com.