Tonight's Sky
Sun
Sun
Moon
Moon
Mercury
Mercury
Venus
Venus
Mars
Mars
Jupiter
Jupiter
Saturn
Saturn

Tonight's Sky — Change location

OR

Searching...

Tonight's Sky — Select location

Tonight's Sky — Enter coordinates

° '
° '

What happens to stars once they die and cool down completely? Is the end result different for neutron stars, pulsars, and white dwarfs?

Rich Livitski, Seal Beach, California
ScreenShot20170802at1.14.08PM
During totality, some stars and planets may become visible in the darkened sky, including Sirius, Arcturus, Capella, Jupiter, and Venus.
Astronomy: Richard Talcott and Roen Kelly
The discovery of nuclear fusion processes last century was the seed for a detailed picture of the evolution of a star from a protostellar gas cloud through extinction as a white dwarf or death in a supernova. A star’s mass largely determines its fate; chemical composition plays a smaller role.

Stars with mass similar to the Sun will end up as white dwarfs — cores of carbon and oxygen with hydrogen- or helium-dominated atmospheres — after their outer layers of gas are lost as stellar superwinds. Ultraviolet radiation from the white dwarf ionizes the ejected gas, forming a planetary nebula. The white dwarf core can burn no additional fuel, and it gradually cools until it no longer emits heat or electromagnetic radiation in the visible spectrum. This stellar remnant is called a black dwarf. No black dwarf has been detected yet, as the cooling time that a white dwarf needs to reach this state is longer than the age of the universe. Stars of a few solar masses also end their life cycles as white dwarfs; however, these objects have a mixture of carbon, oxygen, neon, and magnesium in their cores.

In the final moments of stars more than eight times our Sun’s mass, the outer layers fall in at a tenth of the speed of light, bounce off the rigid core, and are ejected in an intense supernova explosion. The core of the star, which contains traces of heavier elements such as iron, is either left as a neutron star or implodes as a black hole. A white dwarf in a binary system can also explode as a supernova, leaving no remnant and expelling iron and other heavier elements generated during the explosion into interstellar space.

Borja Anguiano   
Research Associate, Department of Astronomy,   
University of Virginia, Charlottesville   
0

JOIN THE DISCUSSION

Read and share your comments on this article
Comment on this article
Want to leave a comment?
Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Login or Register now.
0 comments
ADVERTISEMENT

FREE EMAIL NEWSLETTER

Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter.

ADVERTISEMENT
ADVERTISEMENT
EclipseEguideBooklet

Click here to receive a FREE e-Guide exclusively from Astronomy magazine.

Find us on Facebook