‘One in 10 Billion’ Double Star System Discovered
Astronomers have discovered a “phenomenally rare” star system that could one day cause an extremely powerful explosion that showers space with gold.
The “one in 10 billion” system is so rare that only 10 such systems are thought to exist in our entire galaxy.
It has all the conditions to eventually cause a kilonova, caused by the merger of two neutron stars, experts in the US say, creating an explosion 1,000 times brighter than a classical nova.
An unusual grouping of stars known as CPD-29 2176 is located about 11,400 light-years from Earth and was first identified NASANeil Gerels Swift Observatory, launched into space in 2004.
Follow-up observations with the 1.5-meter SMARTS telescope at the Cerro Tololo Inter-American Observatory in Chile allowed astronomers to confirm that the system will one day form a kilonova.
Unusual: Astronomers have discovered a ‘phenomenally rare’ star system (shown in an artist’s print) that could one day unleash an extremely powerful explosion that showers space in gold
This is because they can see that it contains a single neutron star created by what is known as an “ultra-clothed supernova” as well as a massive, close-orbiting star that is itself in the process of becoming an “ultra-clothed supernova.”
An ultra-naked supernova differs from a normal one in that it produces little or no ejection or “ejection”, which experts say is because the exploding star has already been stripped of its outer atmosphere by a companion star.
The exploded star then becomes a neutron star, but since its supernova lacks explosive power, this means that the nearby binary companion is not lost.
A conventional supernova would have thrown the nearest companion star out of the system.
Instead of being ejected, the companion star often ends up transforming into another neutron star itself, providing the perfect ingredients for a kilonova to form.
These are huge explosions caused by the collision of neutron stars with each other, sending an intense stream of high-energy particles into space.
They produce a glowing burst of radioactive light that produces large amounts of important elements such as silver, gold, platinum, and uranium.
CPD-29 2176 is unusual because astronomers have always thought that in order for a kilon star to form, at least one of the neutron stars—some of the densest objects in the universe—must have been created in a traditional supernova explosion.
The new system suggests that this is not the case.
“The current neutron star should have formed without throwing its companion out of the system. An ultra-clothed supernova is the best explanation for why these companion stars are in such a narrow orbit,” said lead author Noel Richardson of Embry-Riddle Aviation University.
“In order to create a kilonova one day, another star would also need to explode as a supernova so that the two neutron stars could eventually collide and merge.”
Cycle: The system contains one neutron star created by an ultra-naked supernova, as well as a massive, close-orbiting star that is itself in the process of becoming an ultra-naked supernova. This picture shows how the system started out as two massive stars (#1) before one became a neutron star and the other will now eventually do so and give rise to a kilon star.
The researchers hope that their discovery will help unravel the mystery of the formation of kilonovae, which in turn will shed light on where the heaviest elements in the universe come from.
“For a long time, astronomers have speculated about the exact conditions that could eventually lead to the emergence of a kilonova,” said co-author André-Nicolas Chenet.
“These new results demonstrate that, at least in some cases, two sister neutron stars can merge if one of them was created without a classical supernova explosion.”
However, astronomers say building such an unusual system would be a long and unlikely process.
“We know that the Milky Way contains at least 100 billion stars and probably hundreds of billions more,” Chené said.
“This wonderful binary system is essentially a one in ten billion system.
“Prior to our study, it was believed that only one or two such systems should exist in a spiral galaxy such as the Milky Way.”
Although the CPD-29 2176 system has all the ingredients to form a kilonova, it would take at least one million years for the massive companion star to end its life in a titanic supernova explosion and leave behind a second neutron star.
What happens next is that the two neutron stars will gradually pull towards each other before they enter a kind of “cosmic ballet” where they slowly lose their orbital energy in the form of gravitational radiation.
A possible merger would likely lead to a kilonova explosion, leaving behind large amounts of heavy elements such as silver and gold.
“This system shows that some neutron stars are formed only in a small supernova explosion,” said Richardson.
“As we understand the growing population of systems such as CPD-29 2176, we will get an idea of how peaceful the death of some stars can be and whether these stars can die without traditional supernovae.”
The results are published today in the journal Nature.