Gravity is usually an uncompromising force, but not for newly discovered white dwarf star US 708. A team of astronomers in Hawaii have found this star is hurtling through space fast enough to escape the entire gravity of our galaxy.
When a star nearby exploded as a supernova, the double detonation sent it flying out of the Milky Way and collecting rapid speed on the way. At its current speed, it could make the journey from Earth to the moon in around 11 minutes, a trip which took Apollo astronauts three days.
Discovered as long ago as 1982 by Dr Peter Usher of Pennsylvania State University, the US 708 star had been long ignored until astronomers at the University of Hawaii at Manoa took another look. They found that it’s currently breaking the galactic record for an unbound star.
Galactic speed records might not mean much right now. But your great great great great great great great grandchildren are going to be all over them.
The white dwarf star is currently on a path that will take it out of our Milky Way in around about 25 million years or so, give or take, unless it gets blasted by another thermonuclear supernova explosion. Then who knows what might happen?
It’s said by scientists that most stars in the Milky Way chill out for a few million or billion years, orbiting the galaxy centre like the Earth orbits the Sun. But this white dwarf star US 708 is a trailblazer. This star is heading out, clocking up speeds of roughly 1,200 kilometers per second or 2.7 million miles per hour, according to 10-metre Keck II and Pan-Starrs1 telescopes in Hawaii.
These findings make the white dwarf the fastest rogue star in the galaxy, a star that no longer orbits the centre and is answerable to no strict Sun dictatorship. Fortunately for US 708, there are no reported intergalactic speed cameras.
Considered a rare “hypervelocity” star and also dubbed the ‘shrapnel star’, the white dwarf will eventually be able to escape the gravity of our Milky Way and head on out to create its own new adventures in the universe.
University of Hawaii at Manoa’s Dr Eugene Magnier commented.
“At that speed, you could travel from Earth to the moon in five minutes. By observing the sky repeatedly over several years, the Pan-Starrs1 survey, let us make a movie of the motions of the stars in the sky. That enables us to study the behaviors of extremely rare and weird stars like US 708.” (Actually 11 minutes as 2.700,000 mph divided by 239,000 distance from the earth to the moon = 11.29707112970711 or rounded off to 11 minutes)
US 708 is a helium-rich white dwarf, suggesting its already squeaky voice must have gotten even squeakier when an even bigger white dwarf star nearby blew up in a tight binary, giving it the biggest kick of its life. Now a 1a supernova, having received material from another star, the white dwarf has avoided the usual fate of reaching a critical mass and exploding thanks to the characteristics of its binary system. Stars that take a hit like this are often obliterated or sent into a funky low speed because they’ve lost a companion star and don’t know what to do with themselves. It naturally just retains a forward momentum, idling out into space.
But not so, the gutsy US 708 white dwarf star, which remained intact to achieve galactic record speeds.
[Images – ESA, Hubble, NASA]