A phase of stellar evolution that occurs after the main sequence life of a star. The core of a red giant is degenerate ionized helium, and it is surrounded by a shell of hydrogen fusion. In response to higher core temperatures, the shell of hydrogen fusion expands the outer atmosphere of the star and eats through it, depositing the helium it creates onto the shrinking core. The ballooning atmosphere cools and glows red, hence the name red giant. 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 will become a red giant the size of Earth's orbit in five to six billion years, and it will fuse helium for about 2 billion years after the helium flash.
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.
coolish, very luminous star.
Red giants are stars of similar mass as the Sun but at a later stage in their lifetime - the Sun will eventually become a red giant. Red giants are much bigger than the Sun, and they have a relatively low surface temperature which is responsible for their red colour.
A large, luminous star with a coll surface, and therefore red in colour.
A post-main-sequence stage of the lifetime of a star; the star becomes relatively bright and relatively cool.
A star which is very large, and relatively cool. Such stars are very bright, and easily visible at large distances. A small minority of them are stars in the process of formation. Most of them are stars in the last stages of their visible life -- in other words, dying stars.
A highly luminous but relatively cool star that has reached a late stage in its life. Such stars are in a more advanced state of evolution and are running out of nuclear fuel and have become less dense.
Phase in star's evolution after completion of hydrogen burning when outer layers become very extended.
A star of great size and brightness that has a relatively low surface temperature.
A star that has a low surface temperature, 2,000 to 3,000 degrees Celsius, and a diameter between 10 and 100 times that of the Sun.
An old star that has used up all the hydrogen in its nucleus (see Nucleosynthesis) and uses instead other elements as fuel to keep shining. The Sun will become a red giant in the future. These stars can be 25 times as big as the Sun, and hundreds of times brighter.
a dying star that has become large in diameter and cool on the surface while the core has shrunk and increased in temperature. Nuclear fusion takes place in a shell around the compressing core. They are more luminous than when the star was in the main sequence stage, even though their surface is cool, because they have a HUGE surface area. Therefore, they are plotted in the upper right part of the Hertzsprung-Russell diagram.
A giant star whose surface temperature is relatively low, so that it glows with a red color.
a large cool star; has a relatively low surface temperature and a diameter large relative to the sun
a bloated star near the end of its life
a large star of spectral class K or M which has evolved off the main sequence
a large star that is reddish or orange in color
an enormous star that has been through its main sequence phase (on the HR diagram)
a star that has exhausted the primary supply of hydrogen fuel at its core
a very large, relatively cool star comprised mainly of ionized atoms
a star in its dying phases. As the core of the star shrinks and heats up, the outer layers must expand and cool according to Newton's Third Law of Motion. These stars are very luminous but very cool
A post- main sequence star of modest mass (a few solar masses or less) with an extended, relatively cool atmosphere.
Red giants are post-main sequence stars on the Red Giant Branch of the HR diagram. They have low effective temperatures, ~ 3,000 K (K or M spectral class) so appear orange or reddish but have high luminosity, 102 to 103 × that of the Sun with luminosity class II or III. Their radius is typically 100 × that of the earlier main sequence stage. Red giants are have hydrogen shell burning and eventually helium core burning. Aldebaran is a red giant.
an unstable star whose hydrogen has run out; it burns helium at its core. The surface of the star is much cooler, which produces its red color. A red giant usually becomes a nova and ultimately a white dwarf.
A large, bright, cool star. Red giants are formed when a star runs out of nuclear fuel in its core. The star starts to contract, which in turn leads to heating and nuclear reactions in layers outside the core and the expansion of the star's outer layers. These outer layers become cooler and redder as they expand.
A large, cool star of high luminosity; a star occupying the upper right portion of the Hertzsprung-Russell diagram.
A large relatively cool star. The Earth and beyond
A large star, above the main sequence on the Hertzsprung-Russel diagram. The stars have a surface temperature of about 3000 degrees centigrade and an absolute magnitude of between around +2 and -2. Stars at this point on the Hertzsprung-Russel diagram will evolve into either white dwarves or neutron stars. See also luminosity classification.
After a star has finished burning the hydrogen in its core, it enters this stage before dying. The star swells up and turns red.
The phase of a star when all the core hydrogen is used up and the star becomes enlarged. It cycles between shell burning and core burning of successivly heavier elements, up to iron. The number of cycles depends on the mass of the star.
A spectral type K or M star nearing the end of its life having a low surface temperature and large diameter eg Betelgeuse in Orion.
A stage in the evolution of a star when the fuel begins to exhaust and the star expands to about fifty times its normal size. The temperature cools, which gives the star a reddish appearance.
a large red star that has low surface temperature and a diameter that is a hundred times that of the sun.
a cool star near the end of its life cycle that has expanded to a diameter a few dozen to a hundred times that of the sun.
the stage near the end of a star's life when it puffs up due to increased temperature in the star's core. The star may expand by 200 times it's main-sequence radius.
A star that has expanded in the late stages of its life and has become extremely large and bright. The outer gas layers are cool so that the star appears red. How can a star become a black hole
Is an expanded small star, this happens because the helium is hot enough to convert into carbon, and the outer layers of the core begin to expand and shine less brightly.
the step in the evolution of a star, during which its outer layers expand and cool down; therefore the star appears larger and more luminous, due to the fact that the emitting surface increases; besides, the temperature decrease determines the shift of the maximum of the light intensity towards the red, that is towards greater wavelengths.
A star that has low surface temperature and a diameter that is large relative to the Sun.
A huge red star that forms when Sun-sized stars start to die and expand.
According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. Examples include Aldebaran, in the constellation Taurus and Arcturus.