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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 El Nath Powering some bright stars September 6, 2023

Bow and Arrow Aiming a bright celestial bow July 29, 2023

Venus and the Beehive Buzzing a “beehive” of stars June 11, 2023

Alphard A long but barren constellation April 8, 2023

Moon, El Nath, and Mars An intriguing stellar giant March 27, 2023

Columba A faint dove in southern skies February 25, 2023

Lynx Looking with the eyes of a lynx January 13, 2023

Moon and Aldebaran The “puffy” future of the Sun October 13, 2022

Moon and Pollux Slowing down one of the twins September 19, 2022

Beta Boötis Two stars with a lot in common July 30, 2022

Beta Cassiopeia Watching a star puff up July 9, 2022

The Goose Chasing down an old goose June 26, 2022

Head of the Serpent Split ends for the serpent May 17, 2022

Draco A not-so-ferocious dragon September 29, 2021

Moon and Aldebaran Brewing up a key element August 29, 2021

Markab The shoulder of the flying horse August 28, 2021

Alphard The “solitary” star of the water snake February 27, 2021

Impressive Clusters A land of monster star clusters August 20, 2020

Muscida The shiny nose of the great bear June 6, 2020

Crimson Star The color of a dying star February 14, 2020

The Whale’s Tail The tale of the tail of the whale November 21, 2019

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

Featured Images

Filling a Jug July 15, 2023
M79, a globular star cluster in Lepus

A Burst of Stars January 5, 2023
Giant bubbles of hot gas form bright splotches on the surface of a red-giant star

Blobby Star December 26, 2017