Banished Stars Die Far From Home

Supernovae are the most powerful stellar explosions known, and they are so brilliant that they can be seen all the way out to the very edge of the observable Universe–which is that relatively small domain of the mysterious and unimaginably vast Cosmos that we can see. This is because the light sent forth by more remote objects has not had sufficient time to travel to us since the Big Bang birth of the Universe almost 14 billion years ago. A supernova heralds the “death” of a star, and these fierce explosions usually blast the doomed, dying star to pieces. In June 2015, astronomers reported that while most supernovae explode within their host galaxies, new, sharp images obtained by the Hubble Space Telescope (HST) confirm that a trio of dazzling supernovae, that were discovered several years ago, exploded in the dark, cold emptiness of the space between galaxies after having been hurled from their host galaxies millions–or even billions–of years earlier. These sad, solitary, doomed and dying stars, lived out their stellar “lives” in exile–and tragically exploded far from home.

Most supernovae occur inside galaxies that harbor hundreds of billions of stars. One supernova might explode per century within each galaxy. Alas, the trio of fiery, exiled supernovae were found in the space between galaxies situated within three large galactic clusters of several thousand galaxies each. The doomed stars’ closest neighbors were probably 300 light years away. This means that they were almost 100 times farther away than our own Sun’s nearest stellar neighbor, Proxima Centauri, which is about 4.25 light years away.

Such solitary supernovae provide an important piece of the puzzle concerning what dwells in the enormous empty spaces between galaxies, and can help astronomers to gain a necessary understanding about how galaxy clusters formed and evolved throughout the almost 14 billion year history of the Universe. 바카라사이트

In fact, the lonely stars destined to blow themselves up far from their galactic homes reminded study leader Dr. Melissa Graham of the fictional star dubbed Thrial, which, in the Ian Banks novel Against A Dark Background, dwells a million light years from any other star. Dr. Graham, an avid fan of science fiction, is a University of California, Berkeley, postdoctoral fellow. In the sci-fi novel, Golter–which is one of the inhabited planets circling Thrial–possesses an eerie black, empty night sky bereft of sparkling stars.

Any planets circling these bizarre intracluster stars were undoubtedly destroyed in the fiery tantrum of Type Ia supernova blasts, heralding the death of their host stars. However, before they went supernova, these very real intracluster stars may well have hosted planets like the imaginary Golter–and they too would have had dark night skies almost completely devoid of starlight, according to Dr. Graham. The density of intracluster stars is approximately one-millionth what we observe from Earth.

“It would have been a fairly dark background indeed, populated only by the occasional faint and fuzzy blobs of the nearest and brightest cluster galaxies,” Dr. Graham continued to explain.

Dr. Graham and her team, including Dr. David Sand of Texas Tech University in Lubbock, Dr. Dennis Zaritsky of the University of Arizona in Tucson, and Dr. Chris Pritchet of the University of Victoria in British Columbia, report their new analysis describing the trio of solitary, doomed stars in a paper presented on Friday, June 5, 2015, at a conference on supernovae held at North Carolina State University in Raleigh. Their paper has also been accepted for publication by the Astrophysical Journal.

Stellar Blasts

Stars do not live forever. All stars, both heavy and light, “live” out their entire stellar existence on what is termed the main-sequence, whereby they fuse their supply of hydrogen in their cores into heavier and heavier atomic elements. All stars are primarily composed of hydrogen–the lightest and most abundant atomic element in the Universe. Stars on the main-sequence must maintain a very delicate balance between two opposing forces–radiation pressure and gravity. The radiation pressure of the hydrogen-burning, main-sequence star pushes all of the stellar material out and away from the star, thus keeping this enormous sphere of roiling, searing-hot, glaring gas fluffy and bouncy against the relentless squeeze of its own merciless gravity. Radiation pressure is derived from stellar nuclear fusion, which is the progressive fusing of the atoms of heavier atomic elements out of lighter ones. All stars blissfully burn their abundant supply of hydrogen into helium–which is the second-lightest atomic element–and this kicks off the process of stellar nucleosynthesis, which is the process that creates all of the familiar atomic elements listed in the Periodic Table. All atomic elements heavier than helium–called metals by astronomers–were formed in the nuclear-fusing, seething-hot furnaces of the cores of stars, or else in the horrific, glaring, raging fires of their explosive supernovae “deaths.” The heaviest atomic elements of all, such as gold and uranium, were created in the supernovae blasts themselves.



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