Diagram of Cosmic Evolution. The time scale is logarithmic. In the bottom right-hand corner. Solar system and biodiversity evolution is shown on the cosmic timescale.
The universe is believed to have emerged from the big bang singluarity through an initial phase of cosmic inflation in which the universe grew faster than the speed of light through exponential anti-gravity firld tensions. When the symmetry-breaking of the four forces of nature occurred, gravity became attractive, the latent heat released a shower of hot particles leading to the hot young universe.
Cosmic nucleo-synthesis leads to a hot plasma which disengages from light as the plasma becomes neutral atomic matter. The halo of this radiation is red-shifted to the 4 degree absolute cosmic background radiation. Lage scale clumping of a fractal nature resulted in the great galazy clusters. Galaxies have been through a process of evolution involving collision and re-absorbtion.
A faint blue galaxy and a quasar showing its jet extending from the centre
Quasars became common for example in the first two billion years of the universe. There appears to be a relatively random distribution of small distant blue galaxies that may represent smaller precursors of such agglomerations. Large spiral galaxies like the milky way have enabled long-lived stable stellar evolution. of sun-like stars to the extent that life on earth has remained possible over a time span about a third as long as the universe itself.
Galaxies seen in the Deep Field project. These look back at a universe about half our age.
Seeking our cosmic roots
A key scientific justification for building Hubble Space Telescope was to use it to measure the size and age of the universe, test theories about its origin in the Big Bang, an the emergence of large-scale structure as embodied in vast filaments of galaxies. We live within a universe that is expanding and evolving. Images of distant galaxies offer "fossil" clues to what the universe looked like when it was only a small fraction of its present age. Understanding galaxy evolution is a prerequisite to addressing even more fundamental questions about the expansion of space and ultimate fate of the universe.
The first Hubble deep images showed that the early universe contained galaxies in a bewildering variety of shapes and also sizes. Some had the familiar elliptical and spiral shapes seen among normal galaxies, but there were many peculiar shapes not commonly seen in the local universe. Few astronomers had expected to see this activity presented in such amazing detail. Impressed by the results of earlier observations a special advisory committee plan to take the deepest picture of the universe, by aiming Hubble for 150 consecutive orbits on a single piece of sky.
To carry out geometrical tests for the curvature of the universe, it is essential to correct for the changing appearance of galaxies as they grow old. A central problem is that the simplest ideas for galaxy evolution are based on observations of nearby galaxies, their apparent sizes, and their distribution in space. This means that a view of young galaxies is missing from fundamental models of galaxy evolution, or from the current picture of the universe itself.
Super-computer simulation of evolution of young small galaxies into larger galaxies in pronounced clusters. See also colliding galaxies Sci. Am. Aug 90.
Observations in the 70's and 80's showed the universe is not as simple as first presumed. Galaxies are not randomly distributed on the sky, but form great clusters, walls, and sheets. This made astronomers and physicists realize that seeing how large-scale structures formed and developed provides a key to the universe's origin. Current observations show that galaxies tend to cluster around other galaxies. However, the faintest galaxies are almost randomly distributed on the sky.
The universe's large-scale structure may be the imprint of much smaller-scale, or quantum, processes that acted shortly after the Big Bang, when the universe was just a soup of subatomic particles. Much later in the universe's history, structure was primarily governed by gravity. In this view, the gravitational attraction was largely between clouds of "dark matter" -- subatomic particles that make up most of the mass of the universe. The galaxies formed at the densest concentrations of dark matter, like froth on the crests of waves in the ocean. Different forms of dark matter predict a different character of the waves and ripples of the early universe.
Bubble of Cosmic Creation May 98 The Gamma ray explosion from galaxy GRB 971214 was for one or two seconds on December 14 as luminous as the entire rest of the universe. It is about 12 billion light years from Earth. In a region 100 miles across the burst created conditions like those of the early universe, about one millisecond after the big bang said Prof. Djorgovski whose findings were reported in Nature.
Quasars date from very early in the evolution of the Universe when the were more galactic collisions drawing large amounts of matter into black holes. At that thime there were 1000 times as many quasars and radio galaxies as there are today. The brightness of a quasar is believed to result from the radiation shooting out their opposed jets from particles spiralling in. If pointing towards Earth this jet concentrates extreme power even at a great distance (The Mosr Distant Radio Galaxies Sci. Am. Jun 93, The Quasar 3C 273 Sci. Am. Jun 91).
Detailed studies of the ages and chemical compositions of stars in our own galaxy suggest that it has led a relatively quiet existence, forming stars at a rate of a few suns a year for the last 10 billion years (How the Milky Way Formed Sci. Am. Jan 93). Other spiral galaxies seem to have similar histories. If this is typical evolution for spiral galaxies, then predictions can be made for what they should have looked like at half their present age -- including their size, color and abundance. This information, combined with actual distances derived from ground-based spectroscopic observations, will provide a new test for theories of spiral galaxies. The other major class of galaxies seen in the nearby universe is the elliptical, football-shaped aggregates of stars that appear to be very old and stopped forming stars long ago. There is currently much debate about when such galaxies formed and whether they formed through collisions of other types of galaxies or through collapse of a pristine cloud of primordial gas in the very early universe.
Orbits of spiral galaxies are circular and planar, but those of elliptical galaxies shuttle around the long axis
Planets, Solar Systems and Biogenesis
An open universe expands forever because it does not contain enough matter (also called mass density). Space is said to be negatively curved, as first described by Einstein in his law of general relativity. A closed universe eventually stops expanding and then contracts, to ultimately collapse into a black hole. In such a universe space is described as positively curved -- the universe folds back in on itself and space is unbounded but finite. The distribution of galaxies in the Hubble Deep Field images may yield clues to the curvature of space.
Left: One of the most distant galaxies discovered lies lensed around the closer galaxly lower right centre. It has a red-shift of 4.92 and is approximately 13 billion light years away putting it at only about 7% of the current age of the universe. Right: Details of the galaxy spread to correct for the gravitational lensing.
Mar 98 Most Distant Galaxy:
A young galaxy 0140+326RD1 has been found at 12.22 billion light years away, when the universe was only 6% of its present age, about 820 million years after the big bang. RD1 a fairly average galaxy with a mass and luminosity less than our own milky way is 90 million light years further away than any other galaxy.
The Most Distant Known Galaxy shows the early Universe at 7% its current age.
An international team of astronomers has discovered the most distant galaxy found in the universe to date. The galaxy is so far away that its light is only reaching us now from a time when the universe was but 7% of its current age of approximately 14 billion years. This places the young galaxy as far as 13 billion light-years from us, and far back in time during the "formative years" of galaxy birth and evolution. Hubble shows that bright dense knots of massive stars power this object. Because of the firestorm of starbirth within it, the galaxy is intrinsically one of the brightest young galaxies in the universe, blazing with the brilliance of more than 10 times our own Milky Way. The object is similar to what Hubble sees in nearby starburst galaxies, though it is a very extreme and dramatic example.
The object is so far away, observing it in such detail would tax the capabilities of both Hubble and Keck without the magnification of the gravitational lens, provided by a foreground cluster of galaxies that is much closer to us at 5 billion light-years. A telltale sign of the lensing is the fact the remote galaxy's image is smeared into an arc-shape by the gravitational influence of the intervening galaxy cluster. The smeared image of the galaxy stood out because of its unusual reddish color, never observed in such galaxies before. The suspected remoteness of the lensed object was confirmed when the team of astronomers made spectroscopic observations with one of the twin Keck telescopes on Mauna Kea, Hawaii to measure its redshift (4.92), which is a measure of the expansion of space (due to the Big Bang) the larger the redshift, the greater space has expanded between us and the object The researchers used a theoretical model of the effects of the gravitational lens to "unsmear" the galaxy back into its normal appearance. The corrected image clearly shows several bright, very compact regions of intense star formation. The stellar knots could be the building blocks that eventually assembled to form the hub of a galaxy, like the central region of our Milky Way. The tiny, 700 light-year-sized stellar knots are scattered over a region that is only about 15,000 light-years across, only about a quarter the diameter of our Milky Way galaxy. "Based on this image we can begin to make some conclusions about the early growth of galaxies," says Illingworth. "The knots show that starbirth happens in very tiny regions compared with the size of the final galaxy." This helps clarify the astronomer's view of the formation of galaxies as occurring within a cauldron of hot gas, with knots of intense star formation, strong winds, and "mergers" -- collisions of the dense star-forming knots. Using Keck's spectroscopic capabilities, the astronomers have also, for the first time, been able to measure the motions of the gas within such a distant galaxy. The observations reveal a nearly half million mile per hour "wind" -- an outflow of gas, presumably accelerated by energy from supernova explosions going off like a string of firecrackers. "The strong winds that we observe suggest that galaxies may lose a lot of material when they are young and thereby enrich the empty space around them," say Franx. "Many astronomers had speculated about the existence of such winds in such distant galaxies, and we now have an object where we can see them directly. It is striking that the most distant galaxy found to date is also the one that provides us the most detailed picture of events in such distant galaxies."
A Far Cry New Scientist 21 Feb 98 p18.
The furthest observed galaxy now has a red-shift of 5.3, but gamma-ray bursters, probably caused by colliding neutron stars or stars collapsing to form black holes have red-shifts up to 6.2. Supernovas are believed to collapse to neutron stars (pulsars) or to black holes if they contain sufficient mass.
Absence of expected small brown dwarfs in these Hubble pictures indicates brown dwarfs cannot account for dark matter. The yellow simulations indicate the expected density of such objects are to contribute to the mass of dark matter. Left a randomly selected area of sky taken to search for faint red stars that might constitute dark matter in our Milky Way Galaxy. Centre a region (1.4 light-years across) in the globular star cluster NGC 6397 (right) shows far fewer stars than would be expected in faint red dwarf stars were abundant. HST resolves about 200 stars. The stellar density is so low that HST can literally see right through the cluster and resolve far more distant background galaxies
The Elusive nature of dark matter
Becuase the galaxies spin fast enough to throw their stars off unless there is much more matter in the universe than that seen, cosmologists believe there is an order of magnitude more 'dark matter' than the bright matter we see in galactic mass clusters. Various proposals for the source of this dark matter are WIMP (weakly-interacting particles arising from anomalies in force unification), neutrinos (the electron neutrino may have a very small mass and be subject to resonance between the electron, muon and tauon forms, explaining why there are fewer neutrinos leaving the sun than expected from the nuclear reactions it supports. An alternative hypothesis for this is that the sun has a skin of cometary material reducing the required nuclear emission to achieve the current brightness New Scientist 15 June 96).
MACHOS (faint brown starlets) and such anomalies as cosmic strings, solitons (magnetic monopole?) or membranes (again arising from force unification) are also cited to explain dark matter, as well as weakly interacting particles from force diffeerentiation such as axions (WIMPS) weakly-interacting massive particles. Knowing the extent of dark matter is pivotal in determining whether the universe will collapse or expand forever (closed-open models), which the inflationary models take us to the boundary between.
Faint distant galaxies appear gravitationally lensed by nearer bright galaxies at centre (left cross-hair lensing right faint blue galaxies lensed by the closer yellow galaxies). Predicted by Einstein's theory of general relativity, gravitational lenses are collections of matter (such as clusters of galaxies) so massive they warp space in their vicinity, allowing the light of even more-distant objects to curve around the central lens-mass and be seen from Earth magnified.
Bent light Scientific American Sept 92
Gravitational distortions illuminate dark matter
Imagine walking into a pitch-black room and being asked to describe the people standing silently inside. That is the kind of quandary faced by astronomers trying to learn more about dark matter, the unseen material thought to account for as much as 99 percent of the mass of the universe. Amazingly enough, they are having some success in this undertaking. All knowledge of dark matter derives from the fact that it has mass and so produces a gravitational field. In the past few years several astronomers have utilized that property to "see' dark matter indirectly. Because gravity bends, or lenses, light (according to Einstein's theory of relativity), dark matter can be discerned when it distorts one's view of luminous matter. 'The potential of this technique has barely been explored," says Scott D. Tremaine of the University of Toronto, a veteran of dark matter searches. I'm optimistic about it.' The existence of dark matter was posited during the 1970s. At the time, astronomers demonstrated that the outer parts of galxies rotate much faster than theory would predict. If galaxies consisted only of luminous matter, they would quickly fly apart. Similarly, individual galaxies in clusters move at inexplicably high velocities, and yet the clusters have not dispersed. The only plausible explanation for such behavior is that galaxies and clusters contain a healthy dose of dark matter that provides the gravitational glue needed to hold them together. Clumps of dark matter probably helped to instigate the coalescence of the visible galaxies and clusters of galaxies. The abundance of dark matter determines the mass, and hence the fate, of the universe. Current theories predict there should be just enough dark matter to overcome the present cosmic expansion. A little astronomical sleuthing has at last begun to unravel the riddle of where the invisible matter resides and how much of it there is. Although galaxy motions cannot provide much information about where the dark matter is located, observations of gravitational bending of light can. To that end, J. Anthony Tyson and Richard Wenk of AT&T Bell Laboratories and Francisco Valdes of the National Optical Astronomy Observatories have focused their attention on faint, blue galaxies several billion light-years from the earth.
Each square degree of sky contains more than 300,000 blue galaxies, enough to provide a convenient backdrop against which to search for dark matter. Gravity from clusters of galaxies located closer to the earth deflects light from the more distant blue galaxies, altering their oval forms into elongated ellipses and arcs. The shapes and locations of the distorted blue galaxies indicate the abundance and distribution of matter in the nearer cluster. Tyson finds that dark matter follows the overall pattern of visible matter but that its basic unit of 'clumpiness' measures about 300,000 light-years across, distinctly larger than a typical galaxy. Vahe Petrosian of Stanford University, who has made gravitational-lens observations much like those done by Tyson, notes that his work shows dark matter to be "more highly peaked'-that is, more centrally concentrated-than the luminous matter in clusters. That finding underscores just how little is known about the origin of structure: most cosmological models predict that dark matter should be spread more evenly than the visible galaxies. Dark matter may form halos that stretch far beyond the visible edges of clusters of galaxies. If so, it 'could easiIy close the universe,' Tyson says; in Other words, its gravitational pull could eventually halt the expansion of the universe. Tremaine adds that 'there is no reason why you can't have dark matter clusters with no visible frosting at all.' Much of the mass of the universe could reside in unseen clumps that are devoid of luminous galaxies. So far Tyson can only set a lower limit to the density of the universe of about 0.2 times the critical value needed to overcome the expansion. Improving that estimate will require measuring the total extent of the dark matter halos. The outer parts of clusters cover broad patches of sky, so surveying them demands the use of large light detectors that can make use of a telescope's entire field of view. in the past the available detectors were too small to do the job properly. Tyson plans to begin using a larger detector this fall. If there is enough dark matter to close the universe, then dark matter halos must fill the space between clusters of galaxies. In that case, one could look at an apparently empty section of sky and still see signs of gravitational distortion. Such observations might also chance on clusters consisting solely of dark matter. Conversely, if no such distortion appears, one could conclude that the density of the universe is well below the critical value-a finding that would send a lot of theorists back to their blackboards. Tyson has looked at 40 blank fields and claims he already has an answer, but he is not telling anyone until he double-checks his results. A follow-up search using the updated detectors will take about a year. Until then, astronomers will have to be content to believe that there is light at the end of the dark matter tunnel. -Corey S. Powell
Clumping Galaxies Scientific American Mar 91
The cold dark matter theory requires significant modification to account for the clumpiness of observed galaxies, but is supported by some of the findings from the infra-red astronomical satellite (IRAS). The astronomical motions of the galaxies support the conclusion that the universe supports far more mass than that observed. Recent measurements of the motions of satellite galaxies orbiting spirals suggests the spiral galaxies are associated with haloes of dark matter 20 times broader and 100 times more massive than themselves.
Sanity Check Scientific American Jun 94
Puzzling observations of things that go lump in the night
The farther astronomers peer into space, the more they come to appreciate the intricate structure of the universe at very large scales. In 1987 a group of observers inferred the presence of a vast accumwation of matter, nicknamed the 'Great Attractor' (note Sci Am Mar 90 this accounts for 66% and there are larger attracting collections). Two years later another team discovered the 'Great Wall,' an aggregation of ges at least 500 million light-years across. New celestial surveys that take in larger chunks of the universe hint at still vaster gatherings of galaxies. Theorists find themselves hard-pressed to understand the origin of such enormous structures in a cosmos that, according to present knowledge, started out almost perfectly uniform. 'The new surveys are very impressive," says Margaret J. Geller of the Harvard-Smithsonian Center for Astrophysics, "but the state of our ignorance is equally impressive." Geller should know. Over the past decade, she and a number of colleagues-most notably John P. Huchra, also at the Center for Astrophysics-have produced information that has challenged the most ingenious theorizing. What the researchers do is measure the redshift (the stretching of light caused by the expansion of the universe) of thousands of galaxies. The redshift in turn indicates the galaxies' approximate distances from the earth. Those efforts have led to an increasingly comprehensive set of maps that show galaxies located along the bubblelike surfaces of enormous 'voids.' These comparatively empty regions measure as much as 150 million light-years in diameter (for comparison, the Milky Way is only about 100,000 light-years across). The Great Wall is more like a sheet of galaxies that outlines voids. The discovery of the Great Wall has raised two crucial questions: Are such formations typical of the universe as a whole, and does the universe contain even larger structures? In their search for an answer, researchers at the Center for Astrophysics teamed up with a number of astronomers working in Argentina, Chile and South Africa. Observatories in those locations can scnitinize southem parts of the sky that are invisible from the Whipple Observatory in Arizona, where most of the earlier mapping was done. Luis Nicolaci da Costa of the Brazilian National Observatory, a former graduate student at the Center for Astrophysics, headed the group that conducted the mapping of galaxies in the southern sky. Nearly 3,600 galaxies appear in this latest survey. The distribution of galaxies in the southern sky shows a 'gross similahty' to that seen in the nonk Geller reports. For example, da Costa and his co-workers have uncovered a second feature much hke the Great Wall, which is known-predictably-as the Southem Wall. Yet statistical analysis reveals that there are some differences in certain measures," according to Geller. Such differences are significant because they imply that parts of the universe contain structures even larger than the ement of the current north-south sky map. Otherwise, every section of the universe should, when viewed in terms of statistical averages, look like any other section. Da Costa and his fellow team members conclude that the nature of the "shells" of galaxies seen in the map varies over a scale of 300 million light-years or so. Even larger structures may be out there, simply too large to show up in the current study. In the past few years, several groups of researchers have found that the universe displays another, unexpected kind of departure from uniformity. The Milky Way and all the galaxies around us seem to be rushing headlong in the direction of the constellation Leo.
Quantized Red Shifts?
Detailed measurement of the red-shifts of a large collection of galaxies has led to the hypothesis that red-shifts fall into a quantized series. This result which has been independently been confirmed by three independent surveys might indicate quantum effects at very great distances.
Dark Matter blamed for mass extinctions New Scientist 11 Jan 97
WITH dark matter supposedly making up as much as 99 per cent of the Universe, it is used to explain an increasing number of cosmological phenomena. Now nvo physicists are claiming that it may also have changed the course of life on Earth. Dark matter is virtually undetectable except by its gravitational influence on galaxies. Samar Abbas and Asfar Abbas of the institute of Physics at Utkal University in Bhubaneswar, India, suggest that Earth could have encountered dense clumps of dark matter in space, and that this produced large quantities of heat in the planet's interior. Over time, they say the build-up of heat could have led to catastrophic volcanic eruptions. The subsequent climate changes would in turn have wreaked havoc on living species, possibly causing mass extinctions. Their paper is available at the Los Alamos National Laboratories Web site (http://xxx.lanl. gov/abs/astro-ph/9612214). In the mid-1980s, scientists estimated that, given a uniform distribution of dark matter throughout space, Earth could "capture" as many as 1018 particles per second. Abbas and Abbas say this means that Earth would eventually gather so many dark-matter particles in its dense core that they would begin to collide with normal matter there, annihilating themselves in the process. These annihilations could create 10 billion watts of extra heat in the lower mantle. But according to some cosmologists. dark matter is not uniformly distributed, but is instead clumped throughout the Universe. The researchers calculate that an encounter with a dense clump of dark matter could generate even more heat-enough to cause magma to well up from the lowest regions of the mantle. Jeff Kanipe
Consensus Emerges on the
Age of the Universe
Marcus Chown New Scientist 25 May 96
AFTER decades of dispute, astronomers are nearing agreement on the age of the Universe. The researchers who two years ago claimed that the Universe could have been around for as few as 8 billion years have revised their estimate to between 9 and 12 billion-and other groups are reaching similar conclusions. "Everyone is now converging," says Wendy Freedman of the Camegie Observatories in Pasadena. Freedman's 1994 results suggested the universe was younger than some of its stars (New Scientist, Science, 29 October 1994, p 20). Her latest findings, presented at a meeting in Baltimore earlier this month, might just remove that paradox. When calculating the time that has elapsed since the big bang, astronomers first work out a value for the Hubble constant, a measure of the rate at which the Universe is expanding. If the constant is small, the Universe would have taken a long time to reach its present size and must be old. If it is large, the cosmos is young. Astronomers have fallen into two camps, one favouring a high Hubble constant of around 100 kilometres per second per megaparsec, the other a figure of about 50 kilometres per second per megaparsec. Freedman's new figure of 73 kilometres per second per megaparsec is based on Hubble Space Telescope observations of 50 pulsating stars known as Cepheid variables in NGC 1365, a galaxy in the Fomax galaxy cluster. From the timing of the pulses, astronomers can work out the true brightness of the stars. Comparing this with the Cepheids' apparent brightness reveals the stars' distance. The Cepheids indicate that Fornax lies about 18 megaparsecs away. Freedman then used five other distance indicators, including the apparent intensity of Type 1a supemovae, which are all thought to have the same intrinsic brightness, to extend her measurements farther across the Universe. From the redshifts of all these objects, she was able to convert the distances into a value for the Hubble constant, which she believes is accurate to t 15 per cent. Her previous figure of 80 kilometres per second per megaparsec had an error margin of more than 20 per cent.
The new measurement is more reliable because Fornax is more compact than the Virgo cluster, which Freedman studied previously. Relating the Cepheid data to the supemova measurements is also easy, because three supemovae have been seen in Fornax since 1980. Other astronomers are producing values for the constant, that-given the statistical uncertainties-broadly agree with Freedman's figure. Allan Sandage, also of the Carnegie observatories, has obtained a value of 57 kilometres per second per megaparsec, which makes the Universe between 11 and 14 billion years old.
If the Universe's age is at the high end of the range suggested by Freedman and Sandage, the problem surrounding the age of some stars may disappear. 'The proviso is that we live in a low-density Universe," says Freedman. But this creates problems for the cosmological theory of inflation, which says that the Universe went through a short period of ultrafast expansion in its youth. For inflation to have occurred, the Universe must have a high density.
The most distant ype 1a supernova SN1987ap exploded about 7 billion years ago - half the age of the universe.
Distant Exploding Stars Foretell Fate Of The Universe
BERKELEY, CA-- New studies of exploding stars in the farthest reaches of deep space indicate that the universe will expand forever. "Distant supernovae provide natural mile-markers which can be used to measure trends in the cosmic expansion," says Berkeley Lab's Saul Perlmutter, leader of the Supernova Cosmology Project. "All the indications from our observations of supernovae spanning a large range of distances are that we live in a universe that will expand forever. Apparently there isn't enough mass in the universe for its gravity to slow the expansion, which started with the Big Bang, to a halt." This result rests on analysis of 40 of the roughly 65 supernovae so far discovered by the Supernova Cosmology Project. Exploding stars known as supernovae are so intrinsically bright that their light is visible half-way across the observable universe. By the time the light of the most distant supernova explosions so far discovered by the team reached telescopes on earth, some 7 billion years had past since the stars exploded. After such a journey the starlight is feeble, and its wavelengths have been stretched by the expansion of the universe over time (a phenomenon known as redshift). By comparing the faint light of distant supernovae to that of bright nearby supernovae, the astrophysicists were able to determine how far the supernova light had traveled. Distances combined with redshifts of the supernovae give the rate of expansion of the universe over its history, allowing a determination of how much the expansion rate is speeding up or slowing down. The supernova-based measurement of the deceleration depends on the remarkable predictability of one particular kind of supernova explosions, called "Type Ia", These explosion are triggered when a dying white dwarf star pulls too much gas off a neighboring red giant star, igniting a thermonuclear explosion that rips the white dwarf apart. "A Type Ia supernova can shine brighter than an entire galaxy, but only for a month or so before it becomes too faint for even the largest telescopes to observe at these distances," says Gerson Goldhaber, a professor at the Berkeley Lab and the University of California at Berkeley. Although not all Type Ia supernova have the same brightness, their intrinsic brightness can be determined by examining how quickly each supernova fades away. In fact, Type Ia supernovae seen in nearby galaxies are so predictable that, as Peter Nugent of the Berkeley Lab explained at the Washington meeting, "the time at which the supernova explosion started can be determined just from looking at a spectrum. When we studied even the most distant of our supernovae, we found they had just the right spectrum on just the right day of the explosion. This tells us that Type Ia supernovae which exploded when the universe was half its present age behave essentially the same as they do today." Team member Ariel Goobar of the University of Stockholm says, "Reaching out to these most distant supernovae teaches us about the 'Cosmological Constant' which Einstein once called his greatest mistake" -- because if the newly discovered supernovae confirm the story told by the previous 40, astrophysicists may have to invoke Einstein's cosmological constant to obtain agreement with the popular inflation theory which explains how the universe developed shortly after the Big Bang.
The three left lower pictures show visible ultra-violet and a telescope shot of the Sefert galaxy NGC 4151. Hundreds of gas blobs are shown caught up in a twin-cone beam of radiation emanating from a supermassive black hole at the core. Follow-up observations reveal hot gas emanating from deep within the throat of the beam, near the vicinity of the black hole. . Top centre NGC 3379 is a typical class of galaxy believed ot contain a massive central black hole. Top right: This composite image of the core of the galaxy NGC 6251 was constructed by combining a visible light image taken with Hubble's Wide Field Planetary Camera 2 (WFPC2), with a separate image taken in ultraviolet light with the Faint Object Camera (FOC). The bent structure indicates a twisted disk around a massive bare radiating black hole.
Largest Black Hole Discovered? Scientific American
300 million light-years from Earth, next to spiral galaxy NGC 6240, lurks something very dark and very heavy. Examining the galaxy with a telescope in Hawaii, astronomers noticed a whirlwind of stars and gas just beyond the galaxy's edge. The astronomers calculated that at the center of the cyclone lies something as massive as the entire Milky Way-which contains 100 billion stars-but at least 10,000 times smaller in volume and emitting no detectable light. In this image, an ellipse shows the outline of NGC 6240, and a cross marks the location of the massive object. (See also Black Holes in Galactic Centers Sci. Am. Nov 90)
Conclusive evidence of a black hole containing 300,000,000 solar masses
The colorful "zigzag" on the right is not the work of a flamboyant artist, but the signature of a supermassive black hole in the center of galaxy M84, discovered by Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS), on May 12, 1997. The image on the left, taken with Hubble's Wide Field Planetary and Camera 2 shows the core of the galaxy where the suspected black hole dwells. The STIS data on the right shows the rotational motion of stars and gas along the slit. The change in wavelength records whether an object is moving toward or away from the observer. The larger the excursion from the centerline -- as seen as a green and yellow picture element along the center strip, the greater the rotational velocity. If no black hole were present, the line would be nearly vertical across the scan.
Instead, STIS's detector found the S-shape at the center of this scan, indicating a rapidly swirling disk of trapped material encircling the black hole. Along the S-shape from top to bottom, velocities skyrocket as seen in the rapid, dramatic swing to the left (blueshifted or approaching gas), then the region in the center simultaneously records the enormous speeds of the gas both approaching and receding for orbits in the immediate vicinity of the black hole, and then an equivalent swing from the right, back to the center line. STIS measures a velocity of 880,000 miles per hour (400 kilometers per second) within 26 light-years of the galaxy's center, where the black hole dwells. This motion allowed astronomers to calculate that the black hole contains at least 300 million solar masses.