The Runaway Star That's Racing Full-Throttle Out of Our Galaxy

By Andrew Moseman | July 23, 2010 1:13 pm

bluestarI like the Milky Way. I dare say it’s my favorite galaxy, being home and all. But a blue star called HE 0437-5439 is in one big hurry to leave.

The star is zooming away from the Milky Way’s center at 16 million miles per hour, three times faster than our own sun glides across the galaxy. Astronomers had spotted the hasty traveler before—it’s one of 16 known “hypervelocity” stars. Now, with the help of the Hubble Space Telescope, Warren Brown of the Harvard-Smithsonian Center for Astrophysics traced the path of the star back to the event that allowed it to reach such great speed: a meeting with a black hole.

A hundred million years ago this star was one of three traveling together at a more sedate pace.

But the threesome passed dangerously close to the center of our galaxy where the supermassive black hole lurks. The space scientists say it swallowed up one of the stars and booted the other two out of the Milky Way. As they flew, the two stars merged to form one super-hot blue star [Christian Science Monitor].

After the stellar smashup, the black hole flung this remaining star away. That helps explain its path and its haste, Brown says.

“The star is traveling at an absurd velocity, twice as much as it needs to escape the galaxy’s gravitational field. There is no star that travels that quickly under normal circumstances — something exotic has to happen” [Wired.com].

The conflagration also explains the star’s blue appearance, which has scientists scratching their heads—it looked like it was only 20 million years old, but its long trajectory meant it had to be much older. Brown says that when the star absorbed its partner, that refreshed its appearance and made it look young again.

The study appears in The Astrophysical Journal.

Related Content:
DISCOVER: Amazing Images of the Heart of the Milky Way
80beats: Massive Blue Supergiant Challenges Theory of How Big a Star Can Be
80beats: Astronomer: Earth-Like Planets Are Common, But Stars Have Eaten Many
80beats: How a Massive Star Is Born (with gallery)

Image: NASA

CATEGORIZED UNDER: Space
  • Christina

    Why isn’t anyone taking into account that at high enough velocities, time is considerably slowed, and subsequently so is the aging process of the object traveling at such a high speed?

  • JaberwokWSA

    With the speed of light at about 186,000 miles per second, over 670 billion miles per hour, a speed of 16 million miles per hour is only about 2.4% the speed of light. At this comparitively slow speed, relativistic effects haven’t really come in to play. My calcs show that time is about 99.97% of “normal” time, that is, nothing. So, the 100 million years ago was 99.97 million years ago according to the star.

  • Brian Too

    So you’re saying that surgery is more effective than topical creams for rejuvenation? Well shoot, I already knew that…

  • scribbler

    Actually they’re saying that if you canabalize your brother you end up big, bloated and blue and get tossed out of your neighborhood by a tall, dark stranger…

  • Osso

    Maybe it’s a galactic mid-term election. Talk about losing a blue state!

  • WhoDoneIt

    Plus since it is all relative, is the star’s speed relative to our own or relative to the Milky Way?

  • KC

    What would be the effect on the planets (assuming they were not affected by the merge) when the star got booted out at speed?

  • http://cr4.globalspec.com Lew

    How did they figure out there was a 3rd star involved?

  • Amit

    well serves it right for eating its companion.

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