Hubble photographs the Boomerang Nebula
Feb 20, 2003
The Hubble Space Telescope has taken photo images of the “Boomerang Nebula” - the coldest object in the Universe. The nebula is located in the constellation of Centaurus, about 5000 light years from Earth. It is a cloud of dust and gas that is expanding out from an old star, the core of which is collapsing inwards as it becomes a white dwarf. As the gas expands, it has cooled to a temperature of just 1 Kelvin (NASA/ESA photo release 2003).
Raghvendra Sahai from the Jet Propulsion Laboratory and Lars-Ake Nyman from the European Southern Observatory and the Onsala Space Observatory, Sweden first studied the Boomerang Nebula in 1995 using the radio telescope at La Silla, in Chile. They showed that it was the only object cooler than the cosmic microwave background radiation.
Sahai and Nyman believe that the Boomerang is colder than most other expanding nebulae because it is losing its mass about 100 times faster than other similar dying stars. “As the object is losing so much mass, the gas around it – especially carbon monoxide – self-shields itself and the photons from the microwave background do not penetrate deep into the outflow,” says Nyman.
Hubble has shown in its high-resolution images that the “Bow-Tie Nebula” might be a more apt description for the Boomerang, which was originally named by Australian astronomers in 1980.
The images show faint arcs and filaments embedded within the diffuse gas of the smooth “bow-tie” lobes in the nebula. This shape is very different from other observed planetary nebulae, which have lobes that resemble bubbles blown in the gas. Researchers are not certain how these lobes are created but they believe that the overall shape of the Boomerang was created by a 500 000 kilometre-per-hour wind blowing ultra-cold gas away from the dying star.
About the author
Belle Dumé is Science Writer at PhysicsWeb