Monday, June 21, 2021

The coldest object in the Universe: the Boomerang Nebula!

In February 1933 in the Siberian village of Ojmjakon an impressive temperature of -67.8 ° was recorded, which still remains the lowest temperature ever measured in an inhabited center.

More recently, in July 2013, some American scientists based in Antarctica instead measured the record temperature of -98.7 °, the lowest ever recorded on our planet.

However, these values ​​have nothing to do with the coldest object in the Universe: the Boomerang Nebula!

Studied by numerous telescopes, this nebula has a temperature of -272 °, just one degree above absolute zero (1 K)! The Boomerang Nebula is also the only object discovered in nature that has a temperature lower than that of the cosmic background radiation (2.7 K).

This low temperature is explained starting from the particular evolutionary state of the nebula-central star system. The latter is in fact a star of mass similar to the solar one in the final stages of its life that is ejecting its surface layers into space. So far there is nothing special: in the Universe stars in this phase about to form planetary nebulae are very common.

Unlike all these other cases, the star at the center of the Boomerang Nebula is ejecting mass at a very high rate, about 100 times faster than normal. As a result, the nebula's gases began to expand at an impressive speed (over 160 km/s). This expansion rate corresponds to a temperature of 1 K, the lowest ever recorded in the Universe.

Credit: NASA, ESA, Hubble.

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