The coldest place in the Universe looks like a ghost © Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai

The coldest place in the Universe looks like a ghost

This ghostly apparition is a new image of the Boomerang Nebula – the coldest known place in the Universe.

This ghostly apparition is a new image of the Boomerang Nebula – the coldest known place in the Universe.

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At a bone-chilling temperature of one degree Kelvin (−272.15 degrees Celsius), it’s colder, even, than the background temperature of space, which is at a comparatively balmy 2.7 degrees Kelvin.

The Boomerang Nebula, situated around 5,000 light-years away, is a young example of a so-called planetary nebula. These are formed when stars like our Sun reach the ends of their lives and expel their outer layers, leaving behind a luminous core.

A better name for this one, though, might be the Bow Tie Nebula – detailed observations by the Hubble telescope in the 1990s showed that it had a more symmetric, hourglass shape than originally thought. In the image above, the bow tie shape is shown in blue – the result of high-speed gas being ejected from the star. It’s this rapidly-expanding gas that gives the nebula its deathly temperature.

However, new high-resolution radio observations by the Atacama Large Millimeter/submillimeter Array (ALMA) reveal that the nebula actually has a more elongated shape – overlaid in red. Dust grains surrounding the star allow the light to leak out only in narrow directions, which is why Hubble sees the hourglass.

These observations are helping astronomers to shed new light on the death throes of stars. Our Sun is expected to meet a similar fate when it reaches the end of its life. But don’t worry – that won’t happen for another 5 billion years.


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