GALAXIES IN THE NEWS


Galaxy's dark centre exposed BBC   October 2002



Chandra spies bursting galactic beauty - Centaurus A 
August 2002 - CNN Portrait of One Hundred Thousand and One Galaxies August 2002 - Cosmiverse Image of Young Universe Shows 'Seeds' of Galaxies - May 2002 - Reuters Spiral galaxy winds up astronomers BBC February - 2002 This galaxy is spiraling backwards Our galaxy - from the outside February 2002 - BBC News Telescope snaps 'perfect spiral' BBC News - February 2002


'Pipeline' funnels matter between colliding galaxies

January 10, 2001 - NASA

Although astronomers have taken many stunning pictures of galaxies slamming into each other, this image represents the clearest view of how some interacting galaxies dump material onto their companions. These results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA.

Astronomers used the Space Telescope Imaging Spectrograph to confirm that the pipeline is a continuous string of material linking both galaxies.

Scientists believe that the tussle between these compact galaxies somehow created the pipeline, but they're not certain why NGC 1409 was the one to begin gravitationally siphoning material from its partner. And they don't know where the pipeline begins in NGC 1410. More perplexing to astronomers is that NGC 1409 is seemingly unaware that it is gobbling up a steady flow of material. A stream of matter funneling into the galaxy should have fueled a spate of star birth. But astronomers don't see it. They speculate that the gas flowing into NGC 1409 is too hot to gravitationally collapse and form stars.

Astronomers also believe that the pipeline itself may contribute to the star-forming draught. The pipeline, a pencil-thin, 500 light-year-wide string of material, is moving a mere 0.02 solar masses of matter a year.

Astronomers estimate that NGC 1409 has consumed only about a million solar masses of gas and dust, which is not enough material to spawn some of the star-forming regions seen in our Milky Way. The low amount means that there may not be enough material to ignite star birth in NGC 1409, either.

The glancing blow between the galaxies was enough, however, to toss stars deep into space and ignite a rash of star birth in NGC 1410. The arms of NGC 1410, an active, gas-rich spiral galaxy classified as a Seyfert, are awash in blue, the signature color of star-forming regions. The bar of material bisecting the center of NGC 1409 also is a typical byproduct of galaxy collisions.

Astronomers expect more fireworks to come. The galaxies are doomed to continue their game of "bumper cars," hitting each other and moving apart several times until finally merging in another 200 million years. The galaxies' centers are only 23,000 light-years apart, which is slightly less than Earth's distance from the center of the Milky Way. They are bound together by gravity, orbiting each other at 670,000 miles an hour (1 million kilometers an hour). The galaxies reside about 300 million light-years from Earth in the constellation Taurus.


Huge galaxy grouping detected

Thousands of galaxies in the supercluster stand behind red and yellow-coloured foreground stars

January 9, 2001 - BBC

Astronomers have identified a supercluster of galaxies that could be the biggest structure anywhere in the observable Universe.

The grouping, which is in the constellation of Leo, is thought to be about 500 million light-years across and about 6.5 billion light-years from Earth. Because in astronomical terms distance equals time, scientists are seeing the supercluster when the Universe was perhaps one-third the age it is now.

The concentration of galaxies was revealed by the light it absorbed from even more distant quasars located behind the supercluster.

Quasars, "active" galaxies that have very bright cores, probably powered by giant matter-sucking black holes, have become useful tools for probing deep space. They help scientists to map the spatial distribution of galaxies, a task that is vital in developing coherent theories to explain why the matter in the Universe is spread out in the way it is.

The supercluster itself also contains an unusually large number of quasars of its own. It has 18 in a swath of space astronomers would normally expect to find only about two to three if there was no galaxy cluster present.

The international team of astronomers that made the latest discovery said the supercluster posed some questions for current cosmological theories.

Quasars are used to probe the intervening space to Earth

If the concentration of galaxies was caused by a larger than usual amount of matter in the area, traditional theories of the evolution of the Universe would have difficulty explaining how gravity could pull extremely massive structures together over such a large distance, in such a relatively short time, they said.

"A successful theory has to explain the extremes," said Dr Gerard Williger, from Nasa's Goddard Space Flight Center and the National Optical Astronomy Observatories in Arizona, US.

"Bizarre things like this huge supercluster present a unique opportunity to measure how well quasars and galaxies reveal the mass in such a big region of space, which can then be connected to predictions from theories. The light we are presently observing from this large quasar group had to cross such a vast distance to reach us that it actually left the group before the Earth was formed," said Williger.

"We see these galaxies as they existed billions of years ago. The amount of matter connected with quasars and galaxies at such distances and distant times in the past is probably not the same as we would measure in the local Universe today, so it's very important to find out how much mass we are actually looking at in the supercluster. The first step is to look for signs of extra galaxies in the area, and now we have evidence for a surplus of galaxies."

The grouping is in the constellation of Leo

The research was presented on Monday to a meeting of the American Astronomical Society in San Diego, California, and is being prepared for submission to the Astrophysical Journal.

Working with Luis Campusano of the University of Chile and Roger Clowes and Chris Haines of the University of Central Lancashire in the UK, Williger stressed that the research needed to be confirmed with more data.

Enormously bright objects at the edge of the Universe.

Appear point-like, similar to stars, from which they derive their name (quasar = quasi-stellar).

Some quasars shine with the light of a trillion suns.

A type of active galaxy powered by supermassive black hole.

Quasars can show up intervening galaxies.

"We haven't found anything bigger in the literature," he said. "And nobody has brought anything bigger to our attention, but I don't want to go out on a limb and say this is absolutely the biggest because then that surely means somebody is going to come up and say, "but wait ...'"

Scientists mapping the Universe see galaxies as part of groups, clusters and superclusters. These structures may be part of filaments, sheets and walls that enclose huge voids.

Our own galaxy, the Milky Way, is a tiny feature in a relatively small supercluster of galaxies about 50 million light-years in extent. A light-year is 9.5 trillion km (6 trillion miles), the distance light travels in a year.




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