I heard that one of the first waves it detected was from two black holes colliding, but how do the scientists know that it was that particular event, in that part of space, at that time in the past?
In: Physics
The frequency of the signal detected by LIGO lets us determine the masses of the objects involved as well as some other properties which allow us to work out if the event was a black hole-black hole collision or a black hole-neutron star collision. The relative strength of this signal lets us work out the distance to the event and therefore how long ago it was.
LIGO has two different locations which allows us to localise the direction the event is in relative to us.
Each LIGO antenna has two arms at right angles; this gives a partial answer to the question of which direction the signal came from. Every additional LIGO antenna further cuts down the possible directions, since they are necessarily in different orientations. (How many are there? I forget.)
Also, the time between the signal’s arrival at two stations gives the angle between the line from the source to Earth and the line between the stations.
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