A new picture from the Hubble Space Telescope shows an odd structure called the Boomerang Nebula, said to be the coldest object known in the universe.
The young planetary nebula resides in the constellation of Centaurus, 5,000 light-years from Earth. Planetary nebulae form around a bright, central star when it expels gas in the last stages of its life. They have nothing to do with planets, but got the name back when astronomers using crude telescopes thought they looked like the outer planets of our solar system.
The Boomerang Nebula is one of the Universe's peculiar places. In 1995, using the 15-metre Swedish ESO Submillimetre Telescope in Chile, astronomers revealed that it is the coldest place in the universe found so far. With a temperature of -272 degrees Celsius, it is only 1 degree warmer than absolute zero (the lowest limit for all temperatures).
The Boomerang is the only object found so far that has a temperature lower than the
Keith Taylor and Mike Scarrott called it the Boomerang Nebula in 1980 after observing it with a large ground-based telescope in Australia. Unable to see the detail that only Hubble can reveal, the astronomers saw merely a slight asymmetry in the nebula's lobes suggesting a curved shape like a boomerang.
The high-resolution Hubble images reveal feature that resemble a bow tie.
The Hubble telescope actually took this image in 1998, but it was only released today. It shows faint arcs and ghostly filaments embedded within the diffuse gas of the nebula's smooth 'bow tie' lobes. The diffuse bow-tie shape of this nebula makes it quite different from other observed planetary nebulae, which normally have lobes that look more like 'bubbles' blown in the gas. However, the Boomerang Nebula is so young that it may not have had time to develop these structures.
Why planetary nebulae have so many different shapes is still a mystery.
The bow-tie shape of the Boomerang appears to have been created by a very fierce wind of 310,700 mph (500,000 kph) blowing ultracold gas away from the dying central star. The star has been losing as much as one-thousandth of a solar mass of material per year for 1,500 years. This is up to 100 times more than what is lost from similar objects.
The rapid expansion is what has enabled the Boomerang to become so cold, astronomers said.
The image, obtained by researchers at NASA's Jet Propulsion Laboratory, was exposed for 1000 seconds through a green-yellow filter. The light in the image comes from starlight from the central star reflected by dust particles. The Hubble Space Telescope project is an international cooperation between ESA and NASA.
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