{"id":55215,"date":"2024-02-16T06:50:55","date_gmt":"2024-02-16T06:50:55","guid":{"rendered":"http:\/\/7933f694-6ef4-4c8b-aea3-1d4f2fea9379"},"modified":"2024-02-16T07:33:53","modified_gmt":"2024-02-16T07:33:53","slug":"its-cold-in-the-cosmos-this-is-how-astronomers-arrive-at-determining-the-temperature-of-space","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/its-cold-in-the-cosmos-this-is-how-astronomers-arrive-at-determining-the-temperature-of-space\/","title":{"rendered":"It’s cold in the cosmos! This is how astronomers arrive at determining the temperature of space"},"content":{"rendered":"

A guide to cosmic thermodynamics and the extreme temperatures of the Universe. <\/p>

By Alastair Gunn\n <\/p>

Published: Friday, 16 February 2024 at 06:50 AM<\/p>

\n\n

Attempting to deduce the temperature of space is a fascinating exercise, but typically there isn’t a simple, straightforward answer.<\/p>

Temperature is a measurement of the kinetic energy of matter particles.<\/p>

Astronomers often refer to the \u2018temperature\u2019 of a region of space to indicate the kinetic energy of matter in that region.<\/p>

Generally, there isn\u2019t enough matter in space to transfer this heat (or coldness) to other objects.<\/p>

So if you place an object in space, the temperature it attains depends on how much radiation it receives and how good it is at absorbing and emitting that radiation.<\/p>

Put it near a star<\/a> and it will generally heat up, for example.<\/p>

Its temperature, however, is just a measure of the heat balance between the object and its surroundings, and is not the temperature of \u2018space\u2019.<\/p>

So what temperature in space can we measure?<\/strong><\/h2>The Boomerang Nebula is often cited as the coldest place in space. Credit: Bill Saxton (NRAO\/AUI\/NSF); NASA\/Hubble; Raghvendra Sahai<\/figcaption><\/figure>
Space itself doesn\u2019t consist of matter and so doesn\u2019t have a temperature.<\/p>
There is a lot of variation in temperature throughout the Universe.<\/p>
The coldest naturally-occurring temperature in the Universe<\/a> was discovered inside the Boomerang Nebula in 1995.<\/p>
This cloud of gas and dust, in the constellation of Centaurus, was thrown off by a star nearing the end of its life.<\/p>
Its temperature, a result of the slow expansion of the gas cloud, is only -272\u00b0C.<\/p>
The hottest temperatures in space (not including the Big Bang itself) are likely to be generated in the cataclysmic interactions that create Gamma-Ray Bursts<\/a> (GRBs) and may be as high as a trillion degrees.<\/p>
Between these two extremes there is an enormous range of temperatures and the temperatures of objects are constantly changing.<\/p>
$\"GRB$
The afterglow of Gamma Ray Burst 221009A. Credit: NASA\/Swift\/A. Beardmore (University of Leicester)<\/figcaption><\/figure>
How cold can anything be?<\/strong><\/h2>
Physicists have determined that there is a lower limit to the temperature scale called \u2018absolute zero\u2019. It occurs at -273.15\u00b0C, or 0 Kelvin (K).<\/p>
No matter how much you cool something, it can never achieve absolute zero (though you can get pretty close).<\/p>
Strictly speaking, the coldest place in the Universe was in a laboratory in Finland in 2000, when a temperature only 100 trillionths of a degree above absolute zero was artificially created.<\/p>
The average temperature of space<\/strong><\/h2> $\"A$
A snapshot of the Cosmic Microwave Background – heat left over from the Big Bang – when the Universe was just 380,000 years old. Credit: ESA and the Planck Collaboration<\/figcaption><\/figure>
But, what about the overall or average temperature of the Universe?<\/p>
Astronomers often regard the temperature of the Cosmic Microwave Background<\/a> as the temperature of \u2018space\u2019. It has a temperature of 2.735 K (-270.415\u00b0C).<\/p>
The Cosmic Microwave Background is a snapshot of the oldest light in the Universe, imprinted on the sky when the Universe was just 380,000 years old and first became transparent to light.<\/p>
The Big Bang<\/a> theory predicts that as the Universe expands<\/a> this temperature should drop, just as an expanding gas cools.<\/p>
This is exactly what astronomers have found by deducing the temperature of the Cosmic Microwave Background at various distances across the Universe.<\/p>
When the Cosmic Microwave Background radiation was emitted it would have been around 3,000 K.<\/p>
So, given that space is so cold, does water immediately freeze on exposure to the vacuum of space? Yes and no.<\/p>
For water to remain liquid it requires both high temperature and high pressure.<\/p>
With pressure completely removed water will immediately become a vapour, i.e. it will boil.<\/p>
Almost immediately, though, that water vapour will freeze into a mist of ice particles.<\/p> <\/body><\/html>\n
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