Our Sun is a solitary star; a lonely sphere of dazzling, sparkling gas, with no stellar family to call its own. However, most stars are not as bereft of stellar companionship as our Sun--in fact, more than 80% of all the stars in our majestic barred spiral Milky Way Galaxy are very sociable members of multiple stellar systems, containing two or more stars. However, exactly how these systems evolve is not well understood by scientists. In March 2017, a team of astronomers announced that they had succeeded in solving some of this intriguing mystery by observing the dramatic outcome of a centuries-old gravitational battle--which concluded with the disastrous breakup of a multiple system of sibling stars. At least three of the unfortunate sibling stars were rudely evicted from their system, only to speedily streak through interstellar space in different directions--thus revealing their tragic story to the watchful eyes of curious observers.
The terrible star war occurred at the same time that British royal families were fighting the War of the Roses in the 1400s for control of England's throne. The stars, waging their own celestial war, ended with their system breaking apart--never to come together again. The trio of evicted stellar runaways went unnoticed for hundreds of years until--at last--over the past few decades, two of the wayward stars were detected in infrared and radio observations, which could cut through the obscuring thick shroud of dust in the Orion Nebula.
The observations revealed that the two stars were zipping away at high speeds in opposite directions from each other. The duo's origin, however, presented a delightful mystery to be solved. The astronomers who discovered the speedy pair were able to trace both stars back 540 years to the same location. This discovery indicated that they were then constituents of a young and widely dispersed multiple-star system. However, the stellar duo's combined energy, propelling them outward, didn't add up right. The astronomers, therefore, went on to reason that there must be at least one other stellar culprit that cruelly stole energy from the tragic stellar breakup.
The recent observations were conducted using NASA's Hubble Space Telescope (HST). The HST helped the astronomers find the missing piece of the puzzle by shining new light on the third wayward star. The astronomers followed the path of the newly detected third star back to the very same location where the duo of previously known stellar runaways were dwelling 540 years ago. The trio of evicted stars reside in a small region of youthful stars, named the Kleinman-Low Nebula, located near the center of the vast Orion Nebula complex, which is about 1,300 light-years from Earth.
"The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system. Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars. They're probably only a few hundred thousand years old. In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation," explained Dr. Kevin Luhman in a March 17, 2017 Hubblesite Press Release. Dr. Luhman, who is of Pennsylvania State University in University Park, is the lead researcher of the new study.
Stellar Siblings
Stars are born when an extremely dense blob of material, embedded within the swirling, billowing folds of a giant, cold, dark molecular cloud, collapses under the relentless pull of its own gravity. Mostly composed of gas, mixed with a smaller amount of dust, these beautiful, undulating, phantom-like clouds serve as nurseries for baby stars (protostars)--as the dense blob collapses.
The most abundant form of multiple stellar systems are those with two stars (binary systems). These stellar duos have played an important role in many areas of astronomy--especially X-ray astronomy. For many binary stellar systems the two stars orbit their common center of mass due to the lure of their mutual gravitational attraction. However, the two stars may evolve independently (wide binaries), that can be compared to siblings that live in different cities but still keep in touch with e-mails. Wide binaries play an important role in astronomy because they provide the best means available for measuring the masses of stars. This is because astronomers, by observing both the period and size of the orbit, can then apply the theory of gravity.
However, in another form of stellar binary system--called close binaries--the two stars are so close to one another that they are actually able to transfer matter to each other. This exchange influences the appearance of both stars, as well as the way that they evolve.
For example, consider the evolution of a stellar binary system in which the duo consists of two massive stars: A and B. In this hypothetical system, A is the most massive, and because of its greater mass, it will evolve into a red giant star before its sibling. As a result, star A will fling a large quantity of its mass onto smaller star B, altering the appearance of both stellar siblings. Star A quickly uses up its remaining necessary supply of nuclear-fusing fuel, blasts itself to smithereens in a supernova explosion, and leaves behind a stellar relic called a neutron star or a stellar mass black hole behind to tell the tragic story of its demise. Eventually, when smaller star B evolves into a red giant, material being dumped from it onto the sibling neutron star or stellar mass black hole produces a powerful X-ray source that is termed an X-ray binary. The X-ray power of an X-ray binary is millions of times greater than that of the X-rays emitted from more ordinary stellar coronas. The searing-hot, roiling coronas are the upper atmospheres of stars, and they churn out an abundance of X-rays.
What eventually happens to star B depends on its orbit, as well as on the masses of both stars. According to one model, star B could spiral into star A--resulting in a stellar mass black hole. In another scenario, star B could blast itself to smithereens in a supernova explosion that would wreak havoc with the binary system. The supernova blast could produce either a neutron star or a stellar mass black hole. This would result in binary neutron stars--which have been observed--or a neutron star/stellar mass black hole binary. It could also produce a black hole/black hole binary.
If both stars A and B sport relatively small masses approximately the same as that of our Sun, they may both wind up as a type of stellar corpse termed a white dwarf-- rather than as neutron stars or stellar mass black holes, which are produced by stars that are more massive than our Sun. If star A dumps its material onto star B it could result in some very powerful celestial fireworks, called novae. Sometimes star A can manage to dump more of its material on star B--now a white dwarf--than star B can swallow. When this occurs, the white dwarf goes supernova, just like stars of greater mass.
The Strange Tale Of A Stellar Runaway
Dr. Luhman and his colleagues found that the three stellar escapees being observed were zipping at high speed out of the Kleinman-Low Nebula. In fact, the trio of stars were rushing through interstellar space at almost 30 times the speed of most of the nebula's stellar denizens. Based on computer simulations, astronomers predicted that these close gravitational dances should occur in young star clusters, where baby stars are crowded together. "The Orion Nebula could be surrounded by additional fledgling stars that were ejected from it in the past and are now streaming away into space," Dr. Luhman explained in the March 17, 2017 Hubblesite Press Release.
Dr. Luhman chanced upon the elusive third speedy star, called "source x", while he was searching for free-floating exoplanets in the Orion Nebula. Free-floating exoplanets are the rejected and ejected offspring of a star beyond our Sun, who have been evicted from their planetary system as a result of unfortunate gravitational interactions with other planets inhabiting the system or, alternatively, the too close and tragic disruption caused by a passing star. In either case, free-floating exoplanets wander through the wilderness of interstellar space with no parent-star to call their own--bereft of both sister planets and parent-stars. They are the sad orphans of the exoplanet zoo.
As a member of an international team of astronomers, led by Dr. Massimo Robberto of the Space Telescope Science Institute (STSI) in Baltimore, Maryland, Dr. Luhman made his serendipitous discovery of the third stellar runaway. The team used the near-infrared vision of HST's Wide Field Camera 3 to conduct the survey. During the analysis, Dr. Luhman was comparing the new infrared images obtained in 2015 with infrared observations taken back in 1998 by the Near Infrared Camera and Multi Object Spectrometer (NICMOS), when he noticed something strange. Dr. Luhman realized that source x had changed its position considerably, relative to nearby stars over the passage of the 17 years between HST images. This strongly suggested that the star was traveling fast--at the remarkable speed of about 130,000 miles per hour.
Dr. Luhman then studied the earlier locations of the speedy star, projecting its path back in time. He came to the realization that in the 1470s source x had been very close to the same original location in the Kleinman-Low Nebula as the duo of other runaway stars--named Becklin-Neugebauer (BN) and source I.
BN had been detected in infrared images in 1967, but its extremely rapid speed wasn't realized until 1995, when radio observations measured the star's speed at 60,000 miles per hour. In addition source I is zipping along at the breathtaking pace of approximately 22,000 miles per hour. The star had been spotted for the first time in radio observations. This is because it is so heavily veiled within a thick blanket of dust, that its visible and infrared light had been effectively blocked.
The trio of stellar runaways were most likely rudely evicted from their original home when they took part in a wild gravitational dance, according to Dr. Luhman. What frequently occurs when a multiple star system falls apart is that two of the member stars travel close enough to each other that they either merge or form a very close binary system. In either scenario, the event liberates enough gravitational energy to hurl the stars screaming out of the system. The energetic episode also produces a massive outflow of material. This outflow was detected in NICMOS images as fingers of matter flowing away from the location of the embedded source I star.
In the future, upcoming telescopes, such as the James Webb Space Telescope (JWST), will be able to detect a large swath of the Orion Nebula. By comparing images of the Nebula obtained by the upcoming JWST with those already taken by HST years earlier, astronomers plan to identify more unfortunate stellar runaways that have been evicted from other disrupted multiple star systems.
The research describing this study appears in the March 20, 2017 issue of The Astrophysical Journal Letters.
Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various journals, magazines, and newspapers. Although she has written on a variety of topics, she particularly loves writing about astronomy, because it gives her the opportunity to communicate to others the many wonders of her field. Her first book, "Wisp, Ashes, and Smoke," will be published soon.
By Judith E Braffman-Miller
Article Source: The Strange Tale Of A Stellar Runaway
The terrible star war occurred at the same time that British royal families were fighting the War of the Roses in the 1400s for control of England's throne. The stars, waging their own celestial war, ended with their system breaking apart--never to come together again. The trio of evicted stellar runaways went unnoticed for hundreds of years until--at last--over the past few decades, two of the wayward stars were detected in infrared and radio observations, which could cut through the obscuring thick shroud of dust in the Orion Nebula.
The observations revealed that the two stars were zipping away at high speeds in opposite directions from each other. The duo's origin, however, presented a delightful mystery to be solved. The astronomers who discovered the speedy pair were able to trace both stars back 540 years to the same location. This discovery indicated that they were then constituents of a young and widely dispersed multiple-star system. However, the stellar duo's combined energy, propelling them outward, didn't add up right. The astronomers, therefore, went on to reason that there must be at least one other stellar culprit that cruelly stole energy from the tragic stellar breakup.
The recent observations were conducted using NASA's Hubble Space Telescope (HST). The HST helped the astronomers find the missing piece of the puzzle by shining new light on the third wayward star. The astronomers followed the path of the newly detected third star back to the very same location where the duo of previously known stellar runaways were dwelling 540 years ago. The trio of evicted stars reside in a small region of youthful stars, named the Kleinman-Low Nebula, located near the center of the vast Orion Nebula complex, which is about 1,300 light-years from Earth.
"The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system. Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected. But these three stars are the youngest examples of such ejected stars. They're probably only a few hundred thousand years old. In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation," explained Dr. Kevin Luhman in a March 17, 2017 Hubblesite Press Release. Dr. Luhman, who is of Pennsylvania State University in University Park, is the lead researcher of the new study.
Stellar Siblings
Stars are born when an extremely dense blob of material, embedded within the swirling, billowing folds of a giant, cold, dark molecular cloud, collapses under the relentless pull of its own gravity. Mostly composed of gas, mixed with a smaller amount of dust, these beautiful, undulating, phantom-like clouds serve as nurseries for baby stars (protostars)--as the dense blob collapses.
The most abundant form of multiple stellar systems are those with two stars (binary systems). These stellar duos have played an important role in many areas of astronomy--especially X-ray astronomy. For many binary stellar systems the two stars orbit their common center of mass due to the lure of their mutual gravitational attraction. However, the two stars may evolve independently (wide binaries), that can be compared to siblings that live in different cities but still keep in touch with e-mails. Wide binaries play an important role in astronomy because they provide the best means available for measuring the masses of stars. This is because astronomers, by observing both the period and size of the orbit, can then apply the theory of gravity.
However, in another form of stellar binary system--called close binaries--the two stars are so close to one another that they are actually able to transfer matter to each other. This exchange influences the appearance of both stars, as well as the way that they evolve.
For example, consider the evolution of a stellar binary system in which the duo consists of two massive stars: A and B. In this hypothetical system, A is the most massive, and because of its greater mass, it will evolve into a red giant star before its sibling. As a result, star A will fling a large quantity of its mass onto smaller star B, altering the appearance of both stellar siblings. Star A quickly uses up its remaining necessary supply of nuclear-fusing fuel, blasts itself to smithereens in a supernova explosion, and leaves behind a stellar relic called a neutron star or a stellar mass black hole behind to tell the tragic story of its demise. Eventually, when smaller star B evolves into a red giant, material being dumped from it onto the sibling neutron star or stellar mass black hole produces a powerful X-ray source that is termed an X-ray binary. The X-ray power of an X-ray binary is millions of times greater than that of the X-rays emitted from more ordinary stellar coronas. The searing-hot, roiling coronas are the upper atmospheres of stars, and they churn out an abundance of X-rays.
What eventually happens to star B depends on its orbit, as well as on the masses of both stars. According to one model, star B could spiral into star A--resulting in a stellar mass black hole. In another scenario, star B could blast itself to smithereens in a supernova explosion that would wreak havoc with the binary system. The supernova blast could produce either a neutron star or a stellar mass black hole. This would result in binary neutron stars--which have been observed--or a neutron star/stellar mass black hole binary. It could also produce a black hole/black hole binary.
If both stars A and B sport relatively small masses approximately the same as that of our Sun, they may both wind up as a type of stellar corpse termed a white dwarf-- rather than as neutron stars or stellar mass black holes, which are produced by stars that are more massive than our Sun. If star A dumps its material onto star B it could result in some very powerful celestial fireworks, called novae. Sometimes star A can manage to dump more of its material on star B--now a white dwarf--than star B can swallow. When this occurs, the white dwarf goes supernova, just like stars of greater mass.
The Strange Tale Of A Stellar Runaway
Dr. Luhman and his colleagues found that the three stellar escapees being observed were zipping at high speed out of the Kleinman-Low Nebula. In fact, the trio of stars were rushing through interstellar space at almost 30 times the speed of most of the nebula's stellar denizens. Based on computer simulations, astronomers predicted that these close gravitational dances should occur in young star clusters, where baby stars are crowded together. "The Orion Nebula could be surrounded by additional fledgling stars that were ejected from it in the past and are now streaming away into space," Dr. Luhman explained in the March 17, 2017 Hubblesite Press Release.
Dr. Luhman chanced upon the elusive third speedy star, called "source x", while he was searching for free-floating exoplanets in the Orion Nebula. Free-floating exoplanets are the rejected and ejected offspring of a star beyond our Sun, who have been evicted from their planetary system as a result of unfortunate gravitational interactions with other planets inhabiting the system or, alternatively, the too close and tragic disruption caused by a passing star. In either case, free-floating exoplanets wander through the wilderness of interstellar space with no parent-star to call their own--bereft of both sister planets and parent-stars. They are the sad orphans of the exoplanet zoo.
As a member of an international team of astronomers, led by Dr. Massimo Robberto of the Space Telescope Science Institute (STSI) in Baltimore, Maryland, Dr. Luhman made his serendipitous discovery of the third stellar runaway. The team used the near-infrared vision of HST's Wide Field Camera 3 to conduct the survey. During the analysis, Dr. Luhman was comparing the new infrared images obtained in 2015 with infrared observations taken back in 1998 by the Near Infrared Camera and Multi Object Spectrometer (NICMOS), when he noticed something strange. Dr. Luhman realized that source x had changed its position considerably, relative to nearby stars over the passage of the 17 years between HST images. This strongly suggested that the star was traveling fast--at the remarkable speed of about 130,000 miles per hour.
Dr. Luhman then studied the earlier locations of the speedy star, projecting its path back in time. He came to the realization that in the 1470s source x had been very close to the same original location in the Kleinman-Low Nebula as the duo of other runaway stars--named Becklin-Neugebauer (BN) and source I.
BN had been detected in infrared images in 1967, but its extremely rapid speed wasn't realized until 1995, when radio observations measured the star's speed at 60,000 miles per hour. In addition source I is zipping along at the breathtaking pace of approximately 22,000 miles per hour. The star had been spotted for the first time in radio observations. This is because it is so heavily veiled within a thick blanket of dust, that its visible and infrared light had been effectively blocked.
The trio of stellar runaways were most likely rudely evicted from their original home when they took part in a wild gravitational dance, according to Dr. Luhman. What frequently occurs when a multiple star system falls apart is that two of the member stars travel close enough to each other that they either merge or form a very close binary system. In either scenario, the event liberates enough gravitational energy to hurl the stars screaming out of the system. The energetic episode also produces a massive outflow of material. This outflow was detected in NICMOS images as fingers of matter flowing away from the location of the embedded source I star.
In the future, upcoming telescopes, such as the James Webb Space Telescope (JWST), will be able to detect a large swath of the Orion Nebula. By comparing images of the Nebula obtained by the upcoming JWST with those already taken by HST years earlier, astronomers plan to identify more unfortunate stellar runaways that have been evicted from other disrupted multiple star systems.
The research describing this study appears in the March 20, 2017 issue of The Astrophysical Journal Letters.
Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various journals, magazines, and newspapers. Although she has written on a variety of topics, she particularly loves writing about astronomy, because it gives her the opportunity to communicate to others the many wonders of her field. Her first book, "Wisp, Ashes, and Smoke," will be published soon.
By Judith E Braffman-Miller
Article Source: The Strange Tale Of A Stellar Runaway
