The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, based on the results of a series of observations by the Hubble Space Telescope. It covers an area 15 arcminutes across, equivalent in angular size to a tennis ball (about 65mm) at a distance of 100 metres and a two-millionth of our sky. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and December 28, 1995.
The field is so small that only a few foreground stars in the Milky Way lie within it; thus, almost all of the 3,000 objects in the image are galaxies, some of which are among the youngest and most distant known. By revealing such large numbers of very young galaxies, the HDF has become a landmark image in the study of the early universe, and it has been the source of almost 400 scientific papers since it was created.
Three years after the HDF observations were taken, a region in the south celestial hemisphere was imaged in a similar way and named the Hubble Deep Field South. The similarities between the two regions strengthened the belief that the universe is uniform over large scales and that the Earth occupies a typical region in the universe (the cosmological principle). In 2004 a deeper image, known as the Hubble Ultra Deep Field (HUDF), was constructed from a total of eleven days of observations. The HUDF image is the deepest (most sensitive) astronomical image ever made at visible wavelengths.
I was reading about this at work earlier, it is indeed neat stuff.
I highly recommend the NASA coverage on the HDNet channel, it's awesome. The shuttle launches are the next best thing to being there.
The HD broadcasts from the ISP also are incredible. i actually got up and grabbed my Swiffer duster that I keep near the tv to remove some dust specks, but they didn't go away. I realized what I was seeing was dust particles on the lens in the space station. Awesome stuff.
Jet From Supermassive Black Hole Seen Blasting Neighboring Galaxy
By Marc Kaufman Washington Post Staff Writer Tuesday, December 18, 2007; Page A03
A jet of highly charged radiation from a supermassive black hole at the center of a distant galaxy is blasting another galaxy nearby -- an act of galactic violence that astronomers said yesterday they have never seen before.
Using images from the orbiting Chandra X-Ray Observatory and other sources, scientists said the extremely intense jet from the larger galaxy can be seen shooting across 20,000 light-years of space and plowing into the outer gas and dust of the smaller one.
The smaller galaxy is being transformed by the radiation and the jet is being bent before shooting millions of light-years farther in a new direction.
"What we've identified is an act of violence by a black hole, with an unfortunate nearby galaxy in the line of fire," said Dan Evans, the study leader at the Harvard-Smithsonian Center for Astrophysics in Cambridge. He said any planets orbiting the stars of the smaller galaxy would be dramatically affected, and any life forms would likely die as the jet's radiation transformed the planets' atmosphere.
Black holes are generally thought of as mysterious cosmic phenomena that swallow matter, but the supermassive ones that occur at the center of many -- possibly all -- galaxies also set loose tremendous bursts of energy as matter swirls around the disk of material that circles the black hole but does not make it in.
That energy, often in the form of highly charged gamma rays and X-rays, shoots out in powerful jets that can be millions of light-years long and 1,000 light-years wide.
Scientists are just beginning to understand these jets, which not only transform matter in their path but also help produce "stellar nurseries," where new stars are formed.
Evans's collaborator, Martin Hardcastle of the University of Hertfordshire in England, said the collision they have identified began no more than 1 million years ago and could continue for 10 million to 100 million more years. Hardcastle called the collision a great opportunity to learn more about the jets.
"We see jets all over the universe, but we're still struggling to understand some of their basic properties," he said. "This system . . . gives us a chance to learn how they're affected when they slam into something -- like a galaxy -- and what they do after that."
The two galaxies are more than 1.4 billion light-years away from the Milky Way galaxy (a light-year equals about 6 trillion miles). But they are close to each other in cosmic terms -- about as far as the distance from Earth to the center of the Milky Way. That the two appear to be moving toward a merger may have played a role in creating such a powerful jet from the larger galaxy's central black hole.
The researchers said that the collision would have no effect on Earth, but the process is one that could play out in our galaxy a billion years into the future.
The galaxy Andromeda is the closest to the Milky Way, and the two are gradually coming closer to each other. In time, astronomers say, the two will merge, and the process may cause the dormant central black holes in either the Milky Way or Andromeda to become active and begin sending out similarly powerful jets.
If a jet were to hit Earth, Evans said, it would destroy the ozone layer and collapse the magnetosphere that blankets the planet and protects it from harmful solar particles. Without the ozone layer and magnetosphere, he said, much of life on Earth would end.
"This jet could be causing all sorts of problems for the smaller galaxy it is pummeling," Evans said.
Neil deGrasse Tyson, an astrophysicist from the American Museum of Natural History in New York, said the discovery illustrates how researchers can now observe astronomical phenomena using many different tools and understand how they behave at many different points along the electromagnetic spectrum. Only when scientists measure a galaxy at all different wavelengths, he said, "can you really understand what's going on."
In making their discovery, the researchers used data from three orbiting instruments -- the Chandra X-ray Observatory, the Hubble Space Telescope and Spitzer Space Telescope -- as well as ground-based observatories including the Very Large Array telescope in New Mexico and Britain's Multi-Element Radio Linked Interferometer Network. The Astrophysical Journal will publish the results next year.
Interesting. I was watching a Nova program last night on supermassive black holes. Makes me glad that the Milky Way and Andromeda are on a collision course at a rate of 30,000 m/s and are projected to collide in oh, about 10 million years.