The Boomerang Nebula
Hubble image of the Boomerang Nebula. Image credit: NASA/ESA
The average temperature in the Boomerang Nebula is minus 458 degrees Fahrenheit (minus 272 degrees Celsius). The coldest possible temperature in physics is called absolute zero, which is equivalent to minus 460 degrees Fahrenheit (minus 273 degrees Celsius). This means that the Boomerang Nebula is only one degree above the coldest possible temperature in our universe. The Boomerang Nebula is even cooler than the Cosmic Microwave Background Radiation (CMBR), which is a form of microwave radiation left over from the Big Bang. Light from the CMBR has been traversing the universe for over 13 billion years, so its temperature has dropped significantly since the Big Bang. So far, the Boomerang Nebula is the only known object in the universe that has a temperature lower than the CMBR. How exactly did a nebula get so cold?
A Cosmic Refrigerator
Image of the Boomerang Nebula showing the expansion of gas within the nebula. Yellow means gas expanding outward from the central star. Image credit: JPL/ESO
The Boomerang Nebula contains a red giant star that is currently in the final stages of its life. The nebula itself is defined as a protoplanetary nebula and is actually made up of the material ejected from its central star. One day, the red giant star will become a white dwarf and the Boomerang Nebula will become a true planetary nebula. It may seem strange then that the Boomerang Nebula should be so cold since it contains a red giant. Interestingly, the reason this particular nebula is so cold is in principle similar to how a refrigerator works. A refrigerator uses expanding gas to keep it cold, and inside the Boomerang Nebula, gas from the red giant star is expanding outward at an extremely fast rate. This causes the entire structure to become extremely cold, and thus the Boomerang Nebula can be thought of as a kind of cosmic refrigerator.
Aidan Remple September 17, 2022 in Science
