Space & astronomy · the experiment
Link the two signals
Two faint gravitational waves 7.1 hours apart, a supernova in the same place, and a disk that breaks apart. Four questions, from beginner to expert.
1 · Find the link
Beginner
What links the two gravitational-wave alerts of 10 September 2019?
2 · Weigh what distance adds
Probability that an unrelated pair of alerts is this close: 7.6 × 10⁻⁵ using time, sky position and distance; 1.41 × 10⁻⁴ using time and sky position only.
Intermediate
How many times rarer does distance make the pair?
3 · Interpret the 6.6%
The team places a system of 34 + 3 solar masses at the supernova's distance, 140.6 megaparsecs, and draws its orientation at random. A signal as faint as S190910d's comes out 6.6% of the time, mostly for orientations seen nearly edge-on.
Expert
What does the team conclude?
4 · Stretch the spiral
In the fragmenting disk, two light fragments formed about 300 gravitational radii from the black hole (a unit of distance set by the black hole's mass) merge in about 1.3 hours if their initial separation is a third of the Hill radius. The Hill radius is the widest a pair can be at that place in the disk without the black hole pulling it apart. The spiralling time scales as the fourth power of that separation.
Expert
How long do they take if the initial separation is half the Hill radius?
Signals linked
—