These are organized by a classification scheme developed exclusively for Cosma. More…
star : a self-luminous gaseous spheroidal celestial body of great mass which produces energy by means of nuclear fusion reactions — Webster
Staris a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes.
For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star’s interior and then radiates into outer space. Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star’s lifetime, and for some stars by supernova nucleosynthesis when it explodes. Near the end of its life, a star can also contain degenerate matter. Astronomers can determine the mass, age, metallicity (chemical composition), and many other properties of a star by observing its motion through space, its luminosity, and spectrum respectively. The total mass of a star is the main factor that determines its evolution and eventual fate. Other characteristics of a star, including diameter and temperature, change over its life, while the star’s environment affects its rotation and movement. A plot of the temperature of many stars against their luminosities produces a plot known as a Hertzsprung–Russell diagram (H–R diagram). Plotting a particular star on that diagram allows the age and evolutionary state of that star to be determined.
A star’s life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. When the stellar core is sufficiently dense, hydrogen becomes steadily converted into helium through nuclear fusion, releasing energy in the process. The remainder of the star’s interior carries energy away from the core through a combination of radiative and convective heat transfer processes. The star’s internal pressure prevents it from collapsing further under its own gravity. A star with mass greater than 0.4 times the Sun’s will expand to become a red giant when the hydrogen fuel in its core is exhausted. In some cases, it will fuse heavier elements at the core or in shells around the core. As the star expands it throws a part of its mass, enriched with those heavier elements, into the interstellar environment, to be recycled later as new stars. Meanwhile, the core becomes a stellar remnant: a white dwarf, a neutron star, or if it is sufficiently massive a black hole.
Binary and multi-star systems consist of two or more stars that are gravitationally bound and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy. — Wikipedia
Stars News -- ScienceDaily News about Stars. Read science articles and see images on the birth of monstrous stars, brown dwarfs and red giants. Consider stellar evolution and more.
Closest temperate world orbiting quiet star...
on November 15, 2017 at 2:17 pm
A temperate Earth-sized planet has been discovered only 11 light-years from the solar system by a team using ESO's unique planet-hunting HARPS instrument. The new world has the designation Ross 128 b and is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. […]
Duo of titanic galaxies captured in extreme...
on November 13, 2017 at 5:36 pm
Astronomers have uncovered the never-before-seen close encounter between two astoundingly bright and spectacularly massive galaxies in the early universe. […]
Stellar explosions and cosmic 'recipe' for nearby...
on November 13, 2017 at 5:36 pm
Thanks to an in-depth look into the composition of gas in the Perseus galaxy cluster, Japan's Hitomi mission has given scientists new insights into the stellar explosions that formed its chemical elements. […]
Anatomy of a cosmic snake reveals structure of...
on November 13, 2017 at 4:11 pm
We have a fair understanding of star formation, from the interstellar matter to the diffuse clouds whose gravitational contraction gives birth to stars. But observations of distant galaxies have questioned this picture, the size and mass of these distant stellar nurseries exceeding that of their local counterparts. Astrophysicists have tackled this inconsistency and found the first answers thanks to the observation of the cosmic snake. […]
Winds blowing off a dying star
on November 10, 2017 at 1:43 pm
Stars like our Sun eject large amounts of gas and dust into space, containing various elements and compounds. Asymptotic giant branch -- AGB -- phase stars, near their end of life, are particularly significant sources of such substances in our galaxy. […]