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Looking Back in Time to See Stars Bursting Into Life
ScienceDaily (Dec. 17, 2010) — A UK-led international team of astronomers have presented the first conclusive evidence for a dramatic surge in star birth in a newly discovered population of massive galaxies in the early Universe. Their measurements confirm the idea that stars formed most rapidly about 11 billion years ago, or about three billion years after the Big Bang, and that the rate of star formation is much faster than was thought.
An artist's rendition of the core of one of the new SPIRE 'hot starburst' galaxies. (Credit: NASA/CXC/M.Weiss)
The scientists used the European Space Agency's Herschel Space Observatory, an infrared telescope with a mirror 3.5 m in diameter, launched in 2009. They studied the distant objects in detail with the Spectral and Photometric Imaging Receiver (SPIRE) camera, obtaining solid evidence that the galaxies are forming stars at a tremendous rate and have large reservoirs of gas that will power the star formation for hundreds of millions of years.
Dr Scott Chapman, from the Institute of Astronomy in Cambridge, has presented the new results in a paper in a special edition of the journal Monthly Notices of the Royal Astronomical Society focusing on results from Herschel.
Scott comments "These Herschel-SPIRE measurements have revealed the new population of galaxies to be hotter than expected, due to stars forming far much more rapidly than we previously believed."
The galaxies are so distant that the light we detect from them has been travelling for more than 11 billion years. This means that we see them as they were about three billion years after the Big Bang. The key to the new results is the recent discovery of a new type of extremely luminous galaxy in the early Universe.
These galaxies are very faint in visible light, as the newly-formed stars are still cocooned in the clouds of gas and dust within which they were born. This cosmic dust, which has a temperature of around -240oC, is much brighter at the longer, far infrared wavelengths observed by the Herschel satellite.
A related type of galaxy was first found in 1997 (but not well understood until 2003) using the "SCUBA" camera attached to the James Clerk Maxwell Telescope on Hawaii, which detects radiation emitted at even longer sub-millimetre wavelengths. But these distant "sub-millimetre galaxies" were thought to only represent half the picture of star formation in the early Universe. Since SCUBA preferentially detects colder objects, it was suggested that similar galaxies with slightly warmer temperatures could exist but have gone largely unnoticed.
Dr. Chapman and others measured their distances using the Keck optical telescope on Hawaii and the Plateau de Bure sub-millimetre observatory in France, but were unable to show that they were in the throes of rapid star formation.
Herschel is the first telescope with the capability to detect these galaxies at the peak of their output, so Dr. Chapman joined forces with the "HerMES" team, led by Professor Seb Oliver of the University of Sussex and Dr Jamie Bock in Caltech who were undertaking the largest survey of galaxies with Herschel.
With the Herschel observations, focused on around 70 galaxies in the constellation of Ursa Major, the scientists acquired the missing piece of evidence to confirm that these galaxies represent a crucial episode in the build up of large galaxies around us today, such as our own Milky Way.
Team member Professor Rob Ivison from the University of Edinburgh explains the significance of the new results. "With the data we had before, we couldn't tell exactly where the infrared light from these galaxies comes from. But using SPIRE we can see that this is the signature of star formation."
The new galaxies have prodigious rates of star formation, far higher than anything seen in the present day Universe. They probably developed through violent encounters between hitherto undisturbed galaxies, after the first stars and galaxy fragments had already formed. None the less, studying these new objects gives astronomers an insight into the earliest epochs of star formation after the Big Bang.
Team colleague Dr Isaac Roseboom from the University of Sussex sums up the work. "It was amazing and surprising to see the Herschel-SPIRE observations uncover such a dramatic population of previously unseen galaxies." Professor Seb Oliver, also from Sussex, adds: "We are really blown away by the tremendous capability of Herschel to probe the distant universe. This work by Scott Chapman gives us a real handle on how the cosmos looked early in its life."
With the new discovery, the UK-led astronomers have provided a much more accurate census of some of the most extreme galaxies in the Universe at the peak of their activity. Future observations will investigate the details of the galaxies' power source and try to establish how they will develop once their intense bursts of activity come to an end.
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The galaxies are so distant that the light we detect from them has been travelling for more than 11 billion years. This means that we see them as they were about three billion years after the Big Bang.
Amazing, the matters in question were that unspeakably distant. Eyeballing an event that had already taken place more than 11 billion years ago and no longer is, in some spot of the universe! In other words, this cosmic cluster that researchers are now looking at is by now in a fairly different state, since a lot can and must have happened in those 11 billion+ years. How long will it take before, or if at all, one gets to see the entire essence of the evolved "hot" cosmic cluster as it *presently* exists, outside of theoretical lab simulations; could it take another billion years, by which time many of the currently living on earth will not be around? Is that even possible, to get a wholistic eye-witness account of such an entity as it exists today, not to say anything of the still-travelling light emitted in the intermediary stages between that which analysts are now seeing and the state that the-by-now evolved cluster exists? I suppose only remnants of the said cosmic cluster that have drifted relatively closer to our area of the universe will be seen, assuming that these retain light emission in some extraordinary state or another. Wonderful stuff.
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quote:Originally posted by vwwvv: Looking Back in Time to See Stars Bursting Into Life
ScienceDaily (Dec. 17, 2010) — A UK-led international team of astronomers have presented the first conclusive evidence for a dramatic surge in star birth in a newly discovered population of massive galaxies in the early Universe. Their measurements confirm the idea that stars formed most rapidly about 11 billion years ago, or about three billion years after the Big Bang, and that the rate of star formation is much faster than was thought.
An artist's rendition of the core of one of the new SPIRE 'hot starburst' galaxies. (Credit: NASA/CXC/M.Weiss)
The scientists used the European Space Agency's Herschel Space Observatory, an infrared telescope with a mirror 3.5 m in diameter, launched in 2009. They studied the distant objects in detail with the Spectral and Photometric Imaging Receiver (SPIRE) camera, obtaining solid evidence that the galaxies are forming stars at a tremendous rate and have large reservoirs of gas that will power the star formation for hundreds of millions of years.
Dr Scott Chapman, from the Institute of Astronomy in Cambridge, has presented the new results in a paper in a special edition of the journal Monthly Notices of the Royal Astronomical Society focusing on results from Herschel.
Scott comments "These Herschel-SPIRE measurements have revealed the new population of galaxies to be hotter than expected, due to stars forming far much more rapidly than we previously believed."
The galaxies are so distant that the light we detect from them has been travelling for more than 11 billion years. This means that we see them as they were about three billion years after the Big Bang. The key to the new results is the recent discovery of a new type of extremely luminous galaxy in the early Universe.
These galaxies are very faint in visible light, as the newly-formed stars are still cocooned in the clouds of gas and dust within which they were born. This cosmic dust, which has a temperature of around -240oC, is much brighter at the longer, far infrared wavelengths observed by the Herschel satellite.
A related type of galaxy was first found in 1997 (but not well understood until 2003) using the "SCUBA" camera attached to the James Clerk Maxwell Telescope on Hawaii, which detects radiation emitted at even longer sub-millimetre wavelengths. But these distant "sub-millimetre galaxies" were thought to only represent half the picture of star formation in the early Universe. Since SCUBA preferentially detects colder objects, it was suggested that similar galaxies with slightly warmer temperatures could exist but have gone largely unnoticed.
Dr. Chapman and others measured their distances using the Keck optical telescope on Hawaii and the Plateau de Bure sub-millimetre observatory in France, but were unable to show that they were in the throes of rapid star formation.
Herschel is the first telescope with the capability to detect these galaxies at the peak of their output, so Dr. Chapman joined forces with the "HerMES" team, led by Professor Seb Oliver of the University of Sussex and Dr Jamie Bock in Caltech who were undertaking the largest survey of galaxies with Herschel.
With the Herschel observations, focused on around 70 galaxies in the constellation of Ursa Major, the scientists acquired the missing piece of evidence to confirm that these galaxies represent a crucial episode in the build up of large galaxies around us today, such as our own Milky Way.
Team member Professor Rob Ivison from the University of Edinburgh explains the significance of the new results. "With the data we had before, we couldn't tell exactly where the infrared light from these galaxies comes from. But using SPIRE we can see that this is the signature of star formation."
The new galaxies have prodigious rates of star formation, far higher than anything seen in the present day Universe. They probably developed through violent encounters between hitherto undisturbed galaxies, after the first stars and galaxy fragments had already formed. None the less, studying these new objects gives astronomers an insight into the earliest epochs of star formation after the Big Bang.
Team colleague Dr Isaac Roseboom from the University of Sussex sums up the work. "It was amazing and surprising to see the Herschel-SPIRE observations uncover such a dramatic population of previously unseen galaxies." Professor Seb Oliver, also from Sussex, adds: "We are really blown away by the tremendous capability of Herschel to probe the distant universe. This work by Scott Chapman gives us a real handle on how the cosmos looked early in its life."
With the new discovery, the UK-led astronomers have provided a much more accurate census of some of the most extreme galaxies in the Universe at the peak of their activity. Future observations will investigate the details of the galaxies' power source and try to establish how they will develop once their intense bursts of activity come to an end.
These mysterious objects are dark-energy stars, physicist claims.
Black holes may in fact be pockets of 'dark energy'.
Black holes are staples of science fiction and many think astronomers have observed them indirectly. But according to a physicist at the Lawrence Livermore National Laboratory in California, these awesome breaches in space-time do not and indeed cannot exist.
Over the past few years, observations of the motions of galaxies have shown that some 70% the Universe seems to be composed of a strange 'dark energy' that is driving the Universe's accelerating expansion.
George Chapline thinks that the collapse of the massive stars, which was long believed to generate black holes, actually leads to the formation of stars that contain dark energy. "It's a near certainty that black holes don't exist," he claims.
Black holes are one of the most celebrated predictions of Einstein's general theory of relativity, which explains gravity as the warping of space-time caused by massive objects. The theory suggests that a sufficiently massive star, when it dies, will collapse under its own gravity to a single point.
“It's a near certainty that black holes don't exist.”
George Chapline Lawrence Livermore National Laboratory
But Einstein didn't believe in black holes, Chapline argues. "Unfortunately", he adds, "he couldn't articulate why." At the root of the problem is the other revolutionary theory of twentieth-century physics, which Einstein also helped to formulate: Quantum Mechanics.
In General Relativity, there is no such thing as a 'universal time' that makes clocks tick at the same rate everywhere. Instead, gravity makes clocks run at different rates in different places. But quantum mechanics, which describes physical phenomena at infinitesimally small scales, is meaningful only if time is universal; if not, its equations make no sense.
This problem is particularly pressing at the boundary, or event horizon, of a black hole. To a far-off observer, time seems to stand still here. A spacecraft falling into a black hole would seem, to someone watching it from afar, to be stuck forever at the event horizon, although the astronauts in the spacecraft would feel as if they were continuing to fall. "General relativity predicts that nothing happens at the event horizon," says Chapline.
Quantum transitions
However, as long ago as 1975 quantum physicists argued that strange things do happen at an event horizon: matter governed by quantum laws becomes hypersensitive to slight disturbances. "The result was quickly forgotten," says Chapline, "because it didn't agree with the prediction of general relativity. But actually, it was absolutely correct."
This strange behaviour, he says, is the signature of a 'quantum phase transition' of space-time. Chapline argues that a star doesn't simply collapse to form a black hole; instead, the space-time inside it becomes filled with dark energy and this has some intriguing gravitational effects.
Outside the 'surface' of a dark-energy star, it behaves much like a black hole, producing a strong gravitational tug. But inside, the 'negative' gravity of dark energy may cause matter to bounce back out again.
If the dark-energy star is big enough, Chapline predicts, any electrons bounced out will have been converted to positrons, which then annihilate other electrons in a burst of high-energy radiation. Chapline says that this could explain the radiation observed from the centre of our galaxy, previously interpreted as the signature of a huge black hole.
He also thinks that the Universe could be filled with 'primordial' dark-energy stars. These are formed not by stellar collapse but by fluctuations of space-time itself, like blobs of liquid condensing spontaneously out of a cooling gas. These, he suggests, could be stuff that has the same gravitational effect as normal matter, but cannot be seen: the elusive substance known as dark matter.
posted
This is pretty cool stuff. I kinda of think of super massive objects as having dimensionally extended points within their very centers. The less dense an object, the more dimensionless a point at its center would be.
On the other hand super small objects would have inversely dimensionless points.
A true point neither extended dimensionally or inversely can only be expressed in an empty vacuum of space. Perhaps this is the only true way to define an inertial frame of reference. By clever calculation we might be able to pinpoint the very moment of creation.
Just a thought.
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A poster was produced as part of the "Friends with the Universe" project which formed part of South Africa's first year of Science and Technology, YEAST, in 1998. The Starlore poster was the first in a series of ten which were distributed nationally. The aim of Friends was to use astronomy as a vehicle to promote science amongst the diverse communities in South Africa.
The motif of the poster which is reproduced above comprises various scenes depicting legends of southern Africa that relate to the heavens. It was created by Braam Botha, and the copyright rests with SAAO. Scenes from the poster image are juxtaposed with the relevant legend. Click on a part of the image to go straight to the legend. Legends of the Khoikhoi and the San
* A girl child of the old people had magical powers so strong that when she looked at a group of fierce lions, they were immediately turned to stars. The largest are now in Orion's belt.
girl A strong-willed girl became so angry when her mother would not give her any of a delicious roasted root that she grabbed the roasting roots from the fire and threw the roots and ashes into the sky, where the red and white roots now glow as red and white stars, and the ashes are the Milky Way. Dornan. The Bushmen (1925).
And there the road is to this day. Some people call it the Milky Way; some call it the Stars' Road, but no matter what you call it, it is the path made by a young girl many, many years ago, who threw the bright sparks of her fire high up into the sky to make a road in the darkness. Leslau, Charlotte and Wolf. African Folk Tales (1963).
* When the Pleiades appear in the east, little ones are lifted by their mothers and presented to the stars . . . The Pleiades are considered friendly and the children are taught to stretch their hands toward them. * The Pleiades, named Khuseti or Khunuseh by the Khoikhoi, are called the rainstars. Their appearance indicates the rainy season is near and thus the beginning of a new year. Hahn. The Khoikhoi, or Bushmen (1881). * . . . when rain is accompanied by lightning, girls who are out in the open become killed by the lightning and are converted into stars. Therefore young unmarried women and girls must hide themselves from the rain. Schapera (1930).
hunter According to the Namaquas, the Pleiades were the daughters of the sky god. When their husband (Aldeberan) shot his arrow (Orion's sword) at three zebras (Orion's belt), it fell short. He dared not return home because he had killed no game, and he dared not retrieve his arrow because of the fierce lion (Betelgueuse) which sat watching the zebras. There he sits still, shivering in the cold night and suffering thirst and hunger.
* Initiated men among the Namaqua could not partake of hare's flesh. Long ago the moon sent a message to men that as it died and was renewed, so should men be. The hare told men instead they would die and perish like the hare, but said nothing of renewal. Tooke. The Hottentots (1888). * The Sun was once a man who made it day when he raised his arms, for a powerful light shone from his armpits. But as he grew old and slept too long, the people grew cold. Children crept up on him, and threw him into the sky, where he became round and has stayed warm and bright ever since.
The Sotho calendar horn Canopus was called Naka(the horn), or E a dishwa (it is carefully watched). Sotho men would camp in the mountains, where they made fires and watched the early morning skies in the South. It was believed that the first person to see the star would be very prosperous that year, with a rich harvest and good luck to the end of his life. In olden times the chief would give the lucky man a heifer. The day after Naka was sighted was the time for the men with divining bones to examine their bones in still water, to predict the tribe's luck for the coming year. Among the Venda, the first person to see Nanga (Canopus) in the morning sky announced his discovery by climbing a hill and blowing a sable antelope horn (phalaphala). Among the Mapeli, the first person to see the star would begin ululating loudly enough to be heard in the next village, which would then join the noisemaking to warn other villages, each in turn until all knew Canopus had been seen.
* When selomela (the Pleiades) rose in the east, frost was at hand and the leaves fell from the trees in the river beds. * If the senakane (the little horn) (Achernar) when rising in the East is very bright and giving off little lightnings, and the bullrushes are still in flower, men fear an early frost. If Canopus is seen in May with a very intense light, the frost would be very hard. * The shield of the little horn is the Small Magellanic Cloud, known as mo'hora le tlala, `plenty and famine'. If dry dusty air made it appear dim, famine was to be expected.
giraffe The bright stars of the pointers and the southern cross were often seen as giraffes, though different tribes had different ideas about which were male and which were female. Among the Venda the giraffes were known as Thutlwa, `rising above the trees', and in October the giraffes would indeed skim above the trees on the evening horizon, reminding people to finish planting. Tswana
* The sky is stone, and the earth is flat. Water is beneath the earth and above the sky. * The waning moon spills diseases. * Its markings are a woman carrying a child, who was caught gathering wood when she should have been at a sacred festival. * For the Tswana, the stars of Orion's sword were `dintsa le Dikolobe', three dogs chasing the three pigs of Orion's belt. Warthogs have their litters while Orion is prominent in the sky --- frequently litters of three.
sun Some believed that after sunset the sun traveled back to the east over the top of the sky, and that the stars are small holes which let the light through. Others said that the sun is eaten each night by a crocodile, and that it emerges from the crocodile each morning.
* Ntshune was a star (possibly Fomalhaut) visible on winter mornings. This `kiss me' star showed the time for lovers to part before parents found them. * The small constellation of Delphinus may have been seen by the Tswana as a mopane worm.
Sotho, Swazi, Nguni
* The sun's `summer house' and `winter house' (the solstices) were important to the traditional calendar as in many other parts of the world. To the Xhosa these were `injikolanga', `the turning back of the sun'. As late as 1921, governors of royal Swazi villages trusted traditional observations more than printed calendars. * Venus: iCelankobe (Zulu) = `asking for mealies'. As with the Sotho Se-falabogogo (`crust scrapings'), the idea is that someone who arrives for supper by the light of the evening star will do rather badly. The Tswana believed that if Venus were in the evening sky at hoeing season, there would be a good harvest. * According to Credo Mutwa, the Southern Cross is the Tree of Life, `our holiest constellation'.
digger isiLimela or the Pleiades were the `digging stars', whose appearance in southern Africa warned of the coming need to begin hoeing the ground. All over Africa, these stars were used as a marker of the growing season. `And we say isiLimela is renewed, and the year is renewed, and so we begin to dig'. (Callaway 1970). Xhosa men counted their years of manhood from the time in June when isiLimela first became visible.
* To Xhosas, the Milky Way seemed like the raised bristles on the back of an angry dog. Sotho and Tswana saw it as Molalatladi, the place where lightning rests. It also kept the sky from collapsing, and showed the movement of time. Some said it turned the Sun to the east. * For Swazi and Zulu skywatchers, iNqonqoli or Ingongoni was a star associated with wildebeest, whose calves were born in the season when Spica rose before the sun and the morning star. * Canopus was known to some tribes as the `ants' egg star' because of its prominence during the season when the eggs were abundant.
Assorted
* Among the Baronga each moon is regarded as a new birth after the death of the old one. At the appearance of the new moon, recently born children (third month) are `shown their moon'. The mother flings a burning stick toward the moon as the grandmother tosses the child in the air, crying `This is your moon'.The baby is then made to roll over in the ashes. Children lacking this rite would grow up stupid, and dull children are told, `You have not been shown your moon'.
More Moon Legends
* See Hare and the Moon above under Khoisan stories, and the Moon and stupidity in the above paragraph. * Nwedzana=waxing crescent. If the horns point up when the new crescent is sighted in the evening sky, it `was said to be holding up all kinds of disease, and when the horns were tipped down, the moon was a basin pouring illness over the world.' (Sotho, Tswana, Venda) * `No doubt Shaka's harem guards were called the Qwayi-Nyanga, or moon- gazers, because they were to watch over the royal women as intently as the Zulu people watched the moon.' Ng'olumhlope namhla (Zulu) was the black or dark day after the waning crescent's disappearance from the sky. Many considered this a solemn day of rest, when no work or business should take place, and no weddings should be celebrated. * `In Malawi the morning star is Chechichani, a poor housekeeper who allows her husband the moon to go hungry and starve; Puikani, the evening star, is a fine wife who feeds the moon thus bringing him back to life.' * On March 30, 1885 an Ndebele impi which had just set out on campaign saw the moon turn red in a total eclipse, decided the army had been bewitched, and returned to Bulawayo. * Many Africans saw the markings on the moon as a man or woman carrying a bundle of sticks. * For the Khoikhoi the Moon was the `Lord of Light and Life'. * Among the Xhosa it was believed that `the world ended with the sea, which concealed a vast pit filled with new moons ready for use', i.e. that each new lunation begins with a truly new moon. * In Bushman legend the moon is a man who has angered the sun. Every month the moon reaches round prosperity, but the sun's knife then cuts away pieces until finally only a tiny piece is left, which the moon pleads should be left for his children. It is from this piece that the moon gradually grows again to become full.
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