Science Current Events | Science News |

Rogue stars ejected from the galaxy are found in intergalactic space

May 01, 2012

It's very difficult to kick a star out of the galaxy.

In fact, the primary mechanism that astronomers have come up with that can give a star the two-million-plus mile-per-hour kick it takes requires a close encounter with the supermassive black hole at the galaxy's core.

So far astronomers have found 16 of these "hypervelocity" stars. Although they are traveling fast enough to eventually escape the galaxy's gravitational grasp, they have been discovered while they are still inside the galaxy.

Now, Vanderbilt astronomers report in the May issue of the Astronomical Journal that they have identified a group of more than 675 stars on the outskirts of the Milky Way that they argue are hypervelocity stars that have been ejected from the galactic core. They selected these stars based on their location in intergalactic space between the Milky Way and the nearby Andromeda galaxy and by their peculiar red coloration.

"These stars really stand out. They are red giant stars with high metallicity which gives them an unusual color," says Assistant Professor Kelly Holley-Bockelmann, who conducted the study with graduate student Lauren Palladino.

In astronomy and cosmology, "metallicity" is a measure of the proportion of chemical elements other than hydrogen and helium that a star contains. In this case, high metallicity is a signature that indicates an inner galactic origin: Older stars and stars from the galactic fringes tend to have lower metallicities.

The researchers identified these candidates by analyzing the millions of stars catalogued in the Sloan Digital Sky Survey.

"We figured that these rogue stars must be there, outside the galaxy, but no one had ever looked for them. So we decided to give it a try," said Holley-Bockelmann, who is studying the behavior of the black hole at the center of the Milky Way galaxy.

Astronomers have now found evidence for giant black holes at the centers of many galaxies. They estimate that the Milky Way's central black hole has a mass of four million solar masses. They calculate that the gravitational field surrounding such a supermassive black hole is strong enough to accelerate stars to hypervelocities.

The typical scenario involves a binary pair of stars that get caught in the black hole's grip. As one of the stars spirals in towards the black hole, its companion is flung outward at a tremendous velocity.

A second scenario takes place during periods when the central black hole is in the process of ingesting a smaller black hole. Any star that ventures too close to the circling pair can also get a hypervelocity kick.

Red giant stars are the end stage in the evolution of small, yellow stars like the Sun. So, the stars in Holley-Bockelmann's rogues' gallery should have been small stars like the Sun when they tangled with the central black hole. As they traveled outward, they continued to age until they reached the red giant stage. Even traveling at hypervelocities, it would take a star about 10 million years to travel from the central hub to the spiral's edge, 50,000 light years away.

"Studying these rogue stars can provide us with new insights into the history and evolution of our home galaxy," said Holley-Bockelmann. The researchers' next step is determine if any of their candidates are unusually red brown dwarfs instead of red giants. Because brown dwarfs produce a lot less light than red giants, they would have to be much closer to appear equally bright.


Heather Morrison at Case Western Reserve University, Patrick Durrell and John Feldmeier at Youngstown State University, Robin Ciardullo and Richard Wade at Pennsylvania State University, and J. Davy Kirkpatrick and Patrick Lowrance at the California Institute of California also contributed to the research, which was funded by grants from the National Science Foundation and the Department of Education's Graduate Assistance in Areas of National Need fellowship.

Vanderbilt University

Related Black Hole Current Events and Black Hole News Articles

Researcher's work offers more proof of Einstein's general theory of relativity
A Florida State University high-performance computing researcher has predicted a physical effect that would help physicists and astronomers provide fresh evidence of the correctness of Einstein's general theory of relativity.

GMRT discovers a dying, giant radio galaxy 9 billion light years away!
A team of astronomers working at the National Centre for Radio Astrophysics (NCRA, TIFR), Pune have discovered, using the Giant Metrewave Radio Telescope (GMRT), an extremely rare galaxy of gigantic size. This galaxy -- located about 9 billion light years away towards the constellation Cetus -- emits powerful radio waves and has an end to end extent of a whopping 4 million light years!

NASA's Swift spots its thousandth gamma-ray burst
NASA's Swift spacecraft has detected its 1,000th gamma-ray burst (GRB). GRBs are the most powerful explosions in the universe, typically associated with the collapse of a massive star and the birth of a black hole.

Astronomers catch a black hole shredding a star to pieces
When a star comes too close to a black hole, the intense gravity of the black hole results in tidal forces that can rip the star apart. In these events, called tidal disruptions, some of the stellar debris is flung outward at high speeds, while the rest falls toward the black hole. This causes a distinct X-ray flare that can last for years.

The golden anniversary of black-hole singularity
When a star collapses forming a black hole, a space-time singularity is created wherein the laws of Physics no longer work. In 1965 Sir Roger Penrose presented a theorem where he associated that singularity with so-called ''trapped surfaces'' that shrink over time. That hypothesis -one of the results of the general theory of relativity- is now celebrating its anniversary.

11-year cosmic search leads to black hole rethink
One hundred years since Einstein proposed gravitational waves as part of his general theory of relativity, an 11-year search performed with CSIRO's Parkes telescope has failed to detect them, casting doubt on our understanding of galaxies and black holes.

Radio telescopes could spot stars hidden in the galactic center
The center of our Milky Way galaxy is a mysterious place. Not only is it thousands of light-years away, it's also cloaked in so much dust that most stars within are rendered invisible.

Pairs of supermassive black holes in galaxies may be rarer than previously thought
There may be fewer pairs of supermassive black holes orbiting each other at the cores of giant galaxies than previously thought, according to a new study by astronomers who analyzed data from the National Science Foundation's Karl G. Jansky Very Large Array (VLA) radio telescope.

New support for converging black holes in Virgo constellation
Earlier this year, astronomers discovered what appeared to be a pair of supermassive black holes circling toward a collision so powerful it would send a burst of gravitational waves surging through the fabric of space-time itself.

Volunteer black hole hunters as good as the experts
Trained volunteers are as good as professional astronomers at finding jets shooting from massive black holes and matching them to their host galaxies, research suggests.
More Black Hole Current Events and Black Hole News Articles

Black Hole (Pantheon Graphic Novels)

Black Hole (Pantheon Graphic Novels)
by Charles Burns (Author)

Winner of the Eisner, Harvey, and Ignatz Awards

The setting: suburban Seattle, the mid-1970s. We learn from the outset that a strange plague has descended upon the area’s teenagers, transmitted by sexual contact. The disease is manifested in any number of ways — from the hideously grotesque to the subtle (and concealable) — but once you’ve got it, that’s it. There’s no turning back.

As we inhabit the heads of several key characters — some kids who have it, some who don’t, some who are about to get it — what unfolds isn’t the expected battle to fight the plague, or bring heightened awareness to it , or even to treat it. What we become witness to instead is a fascinating and eerie portrait of the nature of high school alienation itself — the savagery,...

Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved

Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved
by Marcia Bartusiak (Author)

For more than half a century, physicists and astronomers engaged in heated dispute over the possibility of black holes in the universe. The weirdly alien notion of a space-time abyss from which nothing escapes—not even light—seemed to confound all logic. This engrossing book tells the story of the fierce black hole debates and the contributions of Einstein and Hawking and other leading thinkers who completely altered our view of the universe.

Renowned science writer Marcia Bartusiak shows how the black hole helped revive Einstein’s greatest achievement, the general theory of relativity, after decades during which it had been pushed into the shadows. Not until astronomers discovered such surprising new phenomena as neutron stars and black holes did the once-sedate universe...

Death by Black Hole: And Other Cosmic Quandaries

Death by Black Hole: And Other Cosmic Quandaries
by Neil deGrasse Tyson (Author)

“[Tyson] tackles a great range of subjects . . . with great humor, humility, and―most important― humanity.” ―Entertainment Weekly Loyal readers of the monthly "Universe" essays in Natural History magazine have long recognized Neil deGrasse Tyson's talent for guiding them through the mysteries of the cosmos with clarity and enthusiasm. Bringing together more than forty of Tyson's favorite essays, ?Death by Black Hole? explores a myriad of cosmic topics, from what it would be like to be inside a black hole to the movie industry's feeble efforts to get its night skies right. One of America's best-known astrophysicists, Tyson is a natural teacher who simplifies the complexities of astrophysics while sharing his infectious fascination for our...

Everything About Black Holes

Everything About Black Holes
by Jonathan Valkanet (Author)

This book explains the most modern scientific knowledge about black holes. Everything known since 2015 is explained simply and clearly. Also included is the Infinite Universe Theory that answers so many unexplained mysteries in our universe like the cause of the big bang, the missing gravity, and the further accelerating galaxies. The last section explains a discovery of the connection between our Sun and the black hole at the center of our galaxy. This book is informative, entertaining, and easy to understand. A must read!

Black Hole: A Novel

Black Hole: A Novel
by Bucky Sinister (Author)

There are no old drug addicts. That's what everyone says, at least. So how did Chuck get to his forty-third birthday and find himself still neck-deep in this scene? He knows he's the creepy old guy with the drugs or the guy who's too old to be at the party doing everyone else's drugs, but if it ain't broke ... Well, he manages to make it to work at the dwarf whale distributor every day. He may hate that his dearly seedy San Francisco has become overrun with Starbucks, startups, and Lululemon moms, but he makes do every month for the rent-controlled apartment he shares with roommates he never sees. It's not perfect, but it's livable.

In the end, though, every addict has that one special vice that can tip them from relatively functional to completely unhinged. For Chuck, it's a new...

Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program)

Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program)
by Kip S. Thorne (Author), Stephen Hawking (Foreword)

Ever since Albert Einstein's general theory of relativity burst upon the world in 1915 some of the most brilliant minds of our century have sought to decipher the mysteries bequeathed by that theory, a legacy so unthinkable in some respects that even Einstein himself rejected them. Which of these bizarre phenomena, if any, can really exist in our universe? Black holes, down which anything can fall but from which nothing can return; wormholes, short spacewarps connecting regions of the cosmos; singularities, where space and time are so violently warped that time ceases to exist and space becomes a kind of foam; gravitational waves, which carry symphonic accounts of collisions of black holes billions of years ago; and time machines, for traveling backward and forward in time.


Black Holes (True Books: Space)

Black Holes (True Books: Space)
by Ker Than (Author)

Book Details:Format: PaperbackPublication Date: 3/1/2010Pages: 48Reading Level: Age 7 and Up

A Black Hole Is Not a Hole

A Black Hole Is Not a Hole
by Carolyn Cinami DeCristofano (Author), Michael Carroll (Illustrator)

Get ready to S-T-R-E-T-C-H your mind!

What is a black hole? Where do they come from? How were they discovered? Can we visit one? Carolyn Cinami DeCristofano takes readers on a ride through the galaxies (ours, and others), answering these questions and many more about the phenomenon known as a black hole.

In lively and often humorous text, the book starts off with a thorough explanation of gravity and the role it plays in the formation of black holes. Paintings by Michael Carroll, coupled with real telescopic images, help readers visualize the facts and ideas presented in the text, such as how light bends, and what a supernova looks like.

A BLACK HOLE IS NOT A HOLE is an excellent introduction to an extremely complex scientific concept. Back matter includes a timeline...

Black Holes and Baby Universes and Other Essays

Black Holes and Baby Universes and Other Essays
by Stephen W. Hawking (Author)


In his phenomenal bestseller A Brief History of Time, Stephen Hawking literally transformed the way we think about physics, the universe, reality itself. In these thirteen essays and one remarkable extended interview, the man widely regarded as the most brilliant theoretical physicist since Einstein returns to reveal an amazing array of possibilities for understanding our universe.

Building on his earlier work, Hawking discusses imaginary time, how black holes can give birth to baby universes, and scientists’ efforts to find a complete unified theory that would predict everything in the universe. With his...

Black Holes: Everything You Need to Know About Black Holes and Black Hole Physics (space exploration, space, astronomy, Cosmology)

Black Holes: Everything You Need to Know About Black Holes and Black Hole Physics (space exploration, space, astronomy, Cosmology)

Everything you Need to Know about Black Holes and Black Hole Physics!

Black Holes have been, and are still to this day, one of the great mysteries of cosmology. They have inspired the imaginations of generations when looking out into space and have been the focus of astronomy for years. Today, much is known about black hole physics and the characteristics of these great beasts of space. This book will bring you up to speed with what we know today about black holes.

Here Is A Preview Of What You'll Learn...Black Hole FundamentalsBlack Hole HistoryBlack Hole FormationBlack Hole AnatomyEvent HorizonSpace and TimeEntering a Black HoleCosmology and AstronomySchwarzschild RadiusPrimordial Black HoleSupermassive Black HoleStellar Black HoleSingularityPhoton...

© 2015