WASHINGTON, Oct. 11 (Xinhua) -- A study published Thursday in the journal Science described the death of a massive star that exploded in a surprisingly faint and rapidly fading supernova, suggesting that the star might have an unseen companion.
The companion siphoned away the star's mass to leave behind a stripped star that exploded in a quick supernova, resulting in a dead neutron star orbiting around its dense and compact companion, according to the study.
This is the first time that scientists have witnessed the birth of a compact neutron star binary system.
Because this new neutron star and its companion are so close together, they will eventually merge in a collision similar to the 2017 event that produced both gravitational waves and electromagnetic waves, according to the study.
When a massive star, at least eight times the mass of the sun, runs out of fuel, its core collapses inwards and then rebounds outward in a powerful explosion.
After the explosion, all of the star's outer layers would have been blasted away, leaving behind a dense neutron star. A teaspoon of a neutron star would weigh as much as a mountain.
During a supernova, the dying star blasts away all of the material in its outer layers, usually a few times the mass of the sun. However, the event Mansi Kasliwal and her colleagues with California Institute of Technology observed ejected matter only one fifth of the mass of the sun.
"We call this an ultra-stripped envelope supernova and it has long been predicted that they exist. This is the first time we have convincingly seen core collapse of a massive star that is so devoid of matter," said Kasliwal.
The researchers inferred that the mass must have been stolen by some kind of dense, compact companion, either a white dwarf, neutron star, or black hole, which is close enough to gravitationally siphon away its mass before it exploded.
The event was first seen at Palomar Observatory in California in a nightly survey of the sky to look for transient, or short-lived, cosmic events like supernovae.