{"id":57867,"date":"2024-04-29T08:18:00","date_gmt":"2024-04-29T08:18:00","guid":{"rendered":"http:\/\/8c9f4e1b-bfd4-41cc-b3f8-da80f63e01a2"},"modified":"2024-04-29T09:09:37","modified_gmt":"2024-04-29T09:09:37","slug":"a-black-dwarf-star-is-so-old-its-even-older-than-the-universe-itself-and-doesnt-technically-exist-yet","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/a-black-dwarf-star-is-so-old-its-even-older-than-the-universe-itself-and-doesnt-technically-exist-yet\/","title":{"rendered":"A black dwarf star is so old, it’s even older than the Universe itself and doesn’t technically exist…yet"},"content":{"rendered":"

A guide to the hypothetical star known as a black dwarf. <\/p>

By <\/p>

Published: Monday, 29 April 2024 at 08:18 AM<\/p>

\n\n

In a nutshell, a black dwarf is a star that\u2019s very, very old.<\/p>

That sounds nice and simple, doesn\u2019t it?<\/p>

But nothing\u2019s ever simple in space, and what complicates the picture somewhat here, is that to become a black dwarf, a star would need to have been around for longer than the Universe has been in existence.<\/p>

Better to say, then, that a black dwarf is an entirely hypothetical star that\u2019s very, very old, older than the current age of the Universe itself<\/a>.<\/p>

Or at least will be, one day.<\/p>

Our Sun and stars similar to it will end their lives by forming a cosmic cloud known as a planetary nebula. Credit: ESA\/Hubble & NASA, R. Wade<\/figcaption><\/figure>

How a black dwarf star forms, in theory<\/strong><\/h2>

Let\u2019s rewind a little and look at what happens to stars<\/a> as they age.<\/p>

The largest stars will swell up into a red supergiant, go bang in a Type II supernova and leave a black hole<\/a> or neutron star<\/a> behind when they\u2019re gone.<\/p>

Smaller stars like our own Sun will swell up into a red giant, then shed their outer layers to form a planetary nebula<\/a>, leaving behind a white dwarf<\/a>.<\/p>

\"Illustration
Illustration showing the explosion of a white dwarf during a Type Ia supernova. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>

White dwarfs are extremely dense \u2013 they\u2019re about the size of Earth, but with the mass of the Sun.<\/p>

They\u2019re also very hot when they first form but cool down gradually over time.<\/p>

Eventually a white dwarf will cool down so much it no longer emits any light or radiation at all, which is when it becomes a black dwarf star.<\/p>

Except that, as explained above, that hasn\u2019t actually happened anywhere yet.<\/p>

Other dwarf stars<\/strong><\/h2>
\"Brown
Artist’s impression of a brown dwarf<\/figcaption><\/figure>

Just to complicate the picture a little further, white and black dwarfs should not be confused with brown, yellow or red dwarfs.<\/p>

Brown dwarfs are stars that never quite achieved nucleur fusion.<\/p>

Larger than a gas giant, smaller than a star, these unloved blobs are scattered throughout the Universe, not doing anything very much.<\/p>

A \u2018yellow dwarf\u2019 is a popular nickname for G-type main sequence stars<\/a> like our own Sun or Alpha Centari B. <\/p>

And a red dwarf is the smallest and coolest category of main sequence stars.<\/p> <\/body><\/html>\n

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