Hubble discovers hyperfast star hailing from Milky Way’s core

WASHINGTON - NASA’s Hubble Space Telescope has come across a hypervelocity star - which is moving three times faster than our sun - hailing from the Milky Way’s core.

The star may have been created in a cosmic misstep. A hundred million years ago, a triple-star system was travelling through the bustling centre of our Milky Way galaxy when it wandered too close to the galaxy’s giant black hole. The black hole captured one of the stars and hurled the other two out of the Milky Way. The two outbound stars merged to form a super-hot blue star travelling at incredible speeds.

This story may seem like science fiction, but Hubble astronomers say it is the most likely scenario for the creation of a so-called hypervelocity star, known as HE 0437-5439. It is one of the fastest ever detected with a speed of 1.6 million mph. Hubble observations confirm that the stellar speedster hails from the Milky Way’s core, settling some confusion about the star’s original home.

Most of the roughly 16 known hypervelocity stars, all discovered since 2005, are thought to be exiles from the heart of our galaxy. But this Hubble result is the first direct observation linking such a star to an origin in the center of the galaxy.

“Using Hubble, we can for the first time trace back to where the star came from by measuring the star’s direction of motion on the sky. Our measurements point directly to the Milky Way centre,” said astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Brown, a member of the Hubble team that observed the star, is the lead author on a paper about the finding published online in the Astrophysical Journal Letters.

Brown said, “These exiled stars are rare in the Milky Way’s population of 100 billion stars. For every 100 million stars in the galaxy, there lurks one hypervelocity star.”

“Studying these stars could provide more clues about the nature of some of the universe’s unseen mass, and it could help astronomers better understand how galaxies form,” added team leader Oleg Gnedin of the University of Michigan in Ann Arbor.

The star’s age is another mystery. Based on the speed and position of HE 0437-5439, the star would have to be 100 million years old to have journeyed from the Milky Way’s core. Yet its mass - nine times that of our sun - and blue colour mean that it should have burned out after only 20 million years - far shorter than the transit time it took to get to its current location.

Astronomers have proposed two possibilities to solve the age problem. The star either dipped into the Fountain of Youth by becoming a blue straggler, or it was flung out of the Large Magellanic Cloud, a neighbouring galaxy.

The most likely explanation for the star’s blue colour and extreme speed is that it was part of a triple-star system that was involved in a gravitational billiards game with the galaxy’s monster black hole. (ANI)