This past summer, there was a lot of excitement about the solar eclipse. What many may not know, is that another rare astronomical event happened around the same time. Two interferometers, instruments that measure interference phenomena between waves, detected merging neutron stars on August 17, 2017.
When normal stars die they leave behind and Earth-sized remnant called a white dwarf. However, when large stars—those with a mass of ten to 20 times that of the Sun—die, they shrink down to the size of a city but maintain a large mass (about two times that of the sun). The pressure of gravity forces electrons into the nuclei of their atoms, where they merge with protons to form neutrons. This is how “neutron stars” get their name. These remnants rotate very quickly, spinning hundreds of times per second. In comparison, the original stars may have only spun once per month.
Most stars are part of binary pairs and, when they die, their neutron stars circle around each other. These orbiting pairs of neutron stars spiral closer and closer as they lose energy. It takes tens to hundreds of millions of years for the neutron stars to come together, but their collision happens in a flash.
The two interferometers that observed the collision are called LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo. Since it takes so long for the neutron stars to get close enough to collide, collisions are more common in older galaxies, so that is where astronomers look.
When the LIGO and Virgo teams detected the stars merging, the observations confirmed the theory that some gamma ray bursts are a result of neutron stars colliding and merging. The LIGO and Virgo teams also gathered information about the merging neutron stars masses, the distance between Earth and the host galaxy, and the duration of the event.
Observing something for the first time is rare, and it confirms a longstanding theory, making it an even more fascinating event—even if it was eclipsed by another space phenomenon.
[Sources: Associated Press; Madison.com; space.com]