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Red Giants

A state of stellar evolution beyond the main-sequence life of a star. A red giant core is degenerate ionized helium, surrounded by a shell of hydrogen fusion, that expands the outer atmosphere in response to higher core temperatures. The hydrogen fusing shell eats through the surrounding atmosphere and deposits helium onto the shrinking core. The ballooning atmosphere cools and glows red; hence red giant. The Sun will become a red giant the size of Earth’s orbit in five to six billion years. Once the helium core reaches 100 million degrees, it explosively begins fusing helium. The birth of the active helium core is called the helium flash. The Sun as a red giant will fuse helium for about 2 billion years after the helium flash.

Resources

Aries, the ram

Aries, the Ram October 4, 2011

Radio Programs

Moon and Aldebaran Inflating a giant star October 17, 2019

Schedar A young star that’s near the end September 9, 2019

Moon and Aldebaran Taking a trip into the future July 26, 2019

Telling Tails The tail ends of two constellations October 13, 2018

Moon and Aldebaran Stirring up a stellar “soup” August 5, 2018

Tarazed An aging star shines bright July 2, 2018

Serpens The severed halves of a snake June 9, 2018

Beta Pegasi Cooling off a giant star September 20, 2017

Menkent An over-represented class of stars June 1, 2017

The Solitary One A solitary light in a zone of darkness April 29, 2017

Moon and Aldebaran The Moon faces the bull March 31, 2017

Moon and Aldebaran A star with a “fuzzy” appearance February 5, 2017

Moon and Aldebaran Things get complicated for a star September 20, 2016

Bow and Arrow Plucking a bright celestial bow August 15, 2016

Moon and Aldebaran Big, fluffy, bright, and orange July 1, 2016

Arcturus Extra pounds cut billions of years June 12, 2016

Moon and Aldebaran Looking at the future of the Sun December 23, 2015

El Nath Sharing a bright star December 20, 2015

Rising Serpent Piecing together a celestial snake May 15, 2015

Bear’s Nose The shiny nose of the great bear May 9, 2015

Alphard A long but barren constellation March 22, 2015

Beta Cassiopeia Watching a star puff up February 27, 2015

Moon and Aldebaran The cool glow of a bright star February 24, 2015

Perseus Taking the measure of a monster January 24, 2015

Featured Images

Giant bubbles of hot gas form bright splotches on the surface of a red-giant star

Blobby Star December 26, 2017
Diagram comparing sizes of Sun, Aldebaran

Giant Eye July 21, 2014