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.
Related Black Hole Current Events and Black Hole News ArticlesNew solar power material converts 90 percent of captured light into heat
A multidisciplinary engineering team at the University of California, San Diego developed a new nanoparticle-based material for concentrating solar power plants designed to absorb and convert to heat more than 90 percent of the sunlight it captures.Lucky Star Escapes Black Hole With Minor Damage
Astronomers have gotten the closest look yet at what happens when a black hole takes a bite out of a star-and the star lives to tell the tale.Big Black Holes Can Block New Stars
Massive black holes spewing out radio-frequency-emitting particles at near-light speed can block formation of new stars in aging galaxies, a study has found.Construction secrets of a galactic metropolis
Galaxy clusters are the largest objects in the Universe held together by gravity but their formation is not well understood.Dead star shines on
A supernova is the cataclysmic death of a star, but it seems its remnants shine on. Astronomers have found a pulsating, dead star beaming with the energy of about 10 million suns.NuSTAR Discovers Impossibly Bright Dead Star
Astronomers working with NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), led by Caltech's Fiona Harrison, have found a pulsating dead star beaming with the energy of about 10 million suns.Simulations Reveal An Unusual Death for Ancient Stars
Certain primordial stars-those between 55,000 and 56,000 times the mass of our Sun, or solar masses-may have died unusually. In death, these objects-among the Universe's first-generation of stars-would have exploded as supernovae and burned completely, leaving no remnant black hole behind.Big surprises can come in small packages
Astronomers using the NASA/ESA Hubble Space Telescope have found a monster lurking in a very unlikely place. Mysterious quasar sequence explained
Quasars are supermassive black holes that live at the center of distant massive galaxies. NASA's RXTE Satellite Decodes the Rhythm of an Unusual Black Hole
Astronomers have uncovered rhythmic pulsations from a rare type of black hole 12 million light-years away by sifting through archival data from NASA's Rossi X-ray Timing Explorer (RXTE) satellite.
More Black Hole Current Events and Black Hole News Articles
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,...
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...
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 Hole Focus: How Intelligent People Can Create a Powerful Purpose for Their Lives|
by Isaiah Hankel (Author)
"...an absurdly motivating book." -- A.J. Jacobs, New York Times bestselling author Don't get stuck on a career path you have no passion for. Don't waste your intelligence on something that doesn't really mean anything more to you than a paycheck. Let Isaiah Hankel help you define a focus so powerful that everything in your life will be pulled towards it. Create your purpose and change your life. Be focused. Be fulfilled. Be successful. Black Hole Focus has been endorsed by top names in business, entrepreneurship, and academia, including 4 times New York Times bestseller AJ Jacobs and Harvard Medical School Postdoc Director Dr. Jim Gould. The book is broken up into 3 different sections; the first section shows you why you need a purpose in life, the second section shows you how to...
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: 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...
Black Holes: A Kids Book About Space - What is a Black Hole? Learn About the Physics and Mysteries of Black Holes|
Children's author Jared Johnson presents: "Black Holes: A Kids Book About Space - What is a Black Hole? Learn About the Physics and Mysteries of Black Holes". This informative children's book includes brilliant REAL, high-quality photographs & some of the most interesting, important facts about Black Holes.
Aside from the beautiful pictures, Jared uncovers some of the most intriguing facts about black holes like:
Where do Black Holes come from and how are they formed?
What do Black Holes look like and how do we know that they exist?
Will our own Sun turn into a Black Hole?
This book is appropriate for children over the age of 8 and young adults because of the physics and space concepts presented in this book.
Get this book at this...
Black Holes (True Books: Space)|
by Ker Than (Author)
Book Details:Format: PaperbackPublication Date: 3/1/2010Pages: 48Reading Level: Age 7 and Up
The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics|
by Leonard Susskind (Author)
At the beginning of the 21st century, physics is being driven to very unfamiliar territory--the domain of the incredibly small and the incredibly heavy. The new world is a world in which both quantum mechanics and gravity are equally important. But mysteries remain. One of the biggest involved black holes. Famed physicist Stephen Hawking claimed that anything sucked in a black hole was lost forever. For three decades, Leonard Susskind and Hawking clashed over the answer to this problem. Finally, in 2004, Hawking conceded.
THE BLACK HOLE WAR will explain the mind-blowing science that finally won out, and the emergence of a new paradigm that argues the world--this catalog, your home, your breakfast, you--is actually a hologram projected from the edges of...
Black Holes! Learn About Black Holes and Enjoy Colorful Pictures - Look and Learn! (50+ Photos of Black Holes)|
Are your kids interested in Black Holes? Awesome! You have found the right book. Help your children learn more about Black Holes today by reading this book.
Here is what is included inside "Black Holes! Learn About Black Holes and Enjoy Colorful Pictures – Look and Learn!"...
Rogue Black Holes
Black Hole Images
Black Hole Facts
Supermassive Black Holes
Black Hole Structures
Fun Black Hole Facts
And Lots More!
Includes over 50 high quality photos of Black Holes!
Other bonuses inside "Black Holes! Learn About Black Holes and Enjoy Colorful Pictures – Look and Learn!"...
This book has photos of Black Holes.