[topquark]

The localization isn't performed through parallax, it's done through triangulation and time-of-arrival. For a pair of observatories, a difference in the arrival time of a signal (moving at the speed of light) defines a circle on the sky of possible source locations. With three observatories, there are three circles on the sky, which intersect at a single point.

The Virgo detector, outside of Pisa, is in the final stages of installing its advanced instrumentation. With LIGO+Virgo a source like the first detection, from September (a very loud event), could be localized to a patch of sky about 10 square degrees in area.

[tossaway1]

> 10 square degrees in area

Wow, that's much bigger than I expected. So basically we can only determine the general direction?

[mapt]

> So basically we can only determine the general direction?

With current-generation detectors installed at three stations which is all we can hope to achieve at the current level of funding in the very near future.

More money, more detections at lower energies, better idea where they come from. There are plenty of instruments in cosmology, astronomy, and physics that have already been designed and planned out, but which do not have the funding to be built; Wait 20 years and five percent of them might come to fruition. You could pour trillions of dollars on these problems without running out of novel questions that we've already proposed ways of answering, and novel results from exploratory instruments we've already proposed building. We spend about 30 billion a year on basic science research according to the NSF, spread over all fields. For comparison, the military gets upwards of 600 billion.

We have good ideas about how to make gravitational wave detectors much, much better, but not how to make them much, much cheaper.

[topquark]

Not so bad as that, but it is a large area, and it's a challenge for optical astronomers to detect a faint source in such a large patch of sky. It's about the size of your two palms held at arms length. (Or, 40 times the size of the full moon, but that sounds less optimistic.)

[sampo]

> > 10 square degrees in area

> So basically we can only determine the general direction?

10 square degrees is about 0.3% of the full spherical sky.

[im3w1l]

It looks 45 times as big as the sun.

[Qantourisc]

Well, the goal of LIGO is to detect if gravity is a wave. So we had to build sensitive sensors, over large distances to be able to pull off this feet. It was (to my knowledge) only build to do this. The fact you can use it for triangulation is a bonus. If they wanted triangulation, I suspect they would have made it with 3 sensors instead of 2.