Wednesday, September 24, 2008

Overlapping Galaxies

NASA's Hubble Space Telescope has captured a rare alignment between two spiral galaxies. The outer rim of a small, foreground galaxy is silhouetted in front of a larger background galaxy. Skeletal tentacles of dust can be seen extending beyond the small galaxy's disk of starlight.

Such outer dark dusty structures, which appear to be devoid of stars, like barren branches, are rarely so visible in a galaxy because there is usually nothing behind them to illuminate them. Astronomers have never seen dust this far beyond the visible edge of a galaxy. They do not know if these dusty structures are common features in galaxies.

Understanding a galaxy's colour and how dust affects and dims that colour are crucial to measuring a galaxy's true brightness. By knowing the true brightness, astronomers can calculate the galaxy's distance from Earth.

Astronomers calculated that the background galaxy is 780 million light-years away. They have not as yet calculated the distance between the two galaxies, although they think the two are relatively close, but not close enough to interact. The background galaxy is about the size of the Milky Way Galaxy and is about 10 times larger than the foreground galaxy.

Most of the stars speckled across this image belong to the nearby spiral galaxy NGC 253, which is out of view to the right. Astronomers used Hubble's Advanced Camera for Surveys to snap images of NGC 253 when they spied the two galaxies in the background. From ground-based telescopes, the two galaxies look like a single blob. But the Advanced Camera's sharp "eye" distinguished the blob as two galaxies, cataloged as 2MASX J00482185-2507365.

Hubble Heritage release The images were taken on Sept. 19, 2006.

Tuesday, September 16, 2008

Upside down Rainbow

The sky is smiling @ Cambridge Evening News

EXCEPTIONAL atmospheric conditions created a rare and stunning display in the skies above Cambridge. At 4.45pm on Sunday, a circumzenithal arc - which looks like a bright, upside down rainbow - was visible above the city.

Cambridge-based astronomer Jacqueline Mitton captured the stunning sight, caused by sunlight being refracted through ice crystals high in the atmosphere, with her camera.

The phenomenon is rarely seen outside the polar regions.

She said: "I've never seen anything like it before - and I'm 60." "The conditions have to be just right: you need the right sort of ice crystals and the sky has to be clear." "It's quite surprising for this to occur somewhere like Cambridge, usually it is in places that are colder."

"We're not sure how big an area it was visible over, but it was certainly very impressive."

The intensity of the colours in the rainbow was heightened by the sun being at the optimum spot in the sky - 22 degrees. And the sky was made even more dazzling with the presence of "sun dogs" - gleaming spots on a halo around the sun - appearing near the phenomenon in the afternoon sky.

Dr Mitton said: "It was just an amazing combination of factors that happened at the right time."

Jacqueline's husband Simon, an astronomy writer, said: "The circumzenithal arc is a quarter circle, pointing toward the setting sun." "The 'rainbow' is much brighter and more concentrated than a rainfall rainbow."

A Met Office spokeswoman said: "They are fairly rare." "It is convex to the sun and is formed by refraction in suitably-oriented ice crystals and may show vivid rainbow colouring, as in this case."

Friday, September 12, 2008

Hawking -vs- Higgs

Stephen Hawking's recent quip that it might be more interesting if the Large Hadron Collider didn't find any Higgs bosons, sets the scene for the ultimate scientific showdown.

Getting upset at Stephen Hawking might not sound like a smart thing for a scientist to do, but when you consider that it's Professor Peter Higgs himself you can sort of see his point.

The Large Hadron Collider LHC @ CERN in Switzerland is the first particle accelerator able to access the energies necessary to reveal the Higgs particle (if it's there) or set an awful lot of people scurrying back to their blackboards (if it's not).

Monday, September 08, 2008

Milky Way Road Trip

Credit & Copyright: Tunç Tezel (TWAN) - Click on Image to Enlarge.

In search of planets and the summer Milky Way. An evening road trip driving the winding road up Uludag, a mountain near Bursa, Turkey, one is rewarded by this beautiful skyview to the south.

Near the center, bright planet Jupiter outshines the city lights below and the stars of the constellation Sagittarius.

Above the mountain peaks, an arcing cloud bank seems to lead to the Milky Way's own cloudy apparition plunging into the distant horizon. In Turkish, Uludag means Great Mountain. Uludag was known in ancient times as the Mysian Olympus.