Hubble Space Telescope detects unbound hypervelocity stars traveling out of our Milky Way Galaxy.
An unbound hypervelocity star may have been created in a cosmic misstep. It is known as a hypervelocity star, and it travels unbound. The space term of the hypervelocity star is HE 0437-5439.
More than a hundred million years ago, a triple-star system was traveling through the center of our Milky Way galaxy. However, 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 traveling 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 in the sky,” said astronomer Warren Brown of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Our measurements point directly to the Milky Way center.”
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 color 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 neighboring galaxy.
The team is trying to determine the homes of the unbound stars, all located on the fringes of the Milky Way. “We are targeting massive ‘B’ stars, like HE 0437-5439,” Warren Brown said in a statement. “These stars shouldn’t live long enough to live in the distant outskirts of the Milky Way, so we shouldn’t expect to find them there. But the quantity of stars in the outer region is much less than in the core, so we have a better chance of finding these unusual objects.”