Star

A cross-section of the Sun.

A cross-section of the Sun

A cross-section of the Sun

Source: commons.wikimedia.org

A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Earth is the Sun. Other stars, mostly in the Milky Way, are visible from Earth during the night, appearing as a multitude of fixed luminous points due to their immense distance. Historically, the most prominent stars were grouped into constellations and asterisms, and the brightest stars gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations.

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. Once the hydrogen in the core of a star is nearly exhausted, 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, luminosity, and spectrum respectively. The total mass of a star is the principal determinant of 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, known as a Hertzsprung–Russell diagram (H–R diagram), allows the age and evolutionary state of a 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. Once 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 processes. The star's internal pressure prevents it from collapsing further under its own gravity. Once the hydrogen fuel at the core is exhausted, a star with at least 0.4 times the mass of the Sun expands to become a red giant, in some cases fusing heavier elements at the core or in shells around the core. The star then evolves into a degenerate form, recycling a portion of its matter into the interstellar environment, where it will contribute to the formation of a new generation of stars with a higher proportion of heavy elements. 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)


 

A cross-section of the Sun.

NASA's Research on the Sun

Video: NASA's Research on the Sun
Duration: 3 minutes 42 seconds (12 MB)

Source: www.nasa.gov

3-D clip highlights active regions on the Sun

3-D clip  highlights active regions on the Sun

This 3-D clip (27 MB) highlights active regions on the Sun.

Source : www.nasa.gov

The Sun In Different Wavelengths Movie

The Sun In Different Wavelengths Movie

The Sun In Different Wavelengths Movie:
Each wavelength allows scientists to see different features on the sun.

Source: www.nasa.gov

All About Solar Flares (Video)

All About Solar Flares (Video)

All About Solar Flares (Video)
Duration: 5 minutes 01 second (16 MB)

Source: www.nasa.gov


Lifecycle of a Star (Video)

Lifecycle of a Star (Video)

Lifecycle of a Star (Video)
Duration: 4 minutes 18 seconds (14 MB)

Source: www.nasa.gov

A full-disk multiwavelength extreme ultraviolet image of the sun

multiwavelength extreme ultraviolet image of the sun

A full-disk multiwavelength extreme ultraviolet image of the sun. Reds are relatively cool (about 60,000 Kelvin, or 107,540 F); blues and greens are hotter (greater than 1 million Kelvin, or 1,799,540 F).

Image source: commons.wikimedia.org

Star-sizes

Star-sizes

Star-sizes

Image source: commons.wikimedia.org

Top 10 Intriguing Stars in the Universe

Top 10 Intriguing Stars in the Universe

Top 10 Intriguing Stars in the Universe

Source: www.toptenz.net

 

 

Time Line of the Universe

Time Line of the Universe

Early life of the Sun, from studies of solar proxies. From left to right, the Sun at an age of: <300 Ma, 650 Ma, 2 Ga, 4.5 Ga (now)

Image source: commons.wikimedia.org

 


Other types of stars

Star Trek

Star Trek

Star Trek

Image source: media.photobucket.com/Rochand

Star Gate

Star Gate

Star Gate

Image source: www.flickr.com/Star Gate

Star war-Warp Speed

Star war-Warp Speed

Star war-Warp Speed

Image source: www.flickr.com/unpolarized

E.T. the movie

E.T. the movie

E.T. the movie

Image source: media.photobucket.com/ manworld


Blue star

Blue star

Blue star

Image source: www.flickr.com/Caucas'

Super Star

Super Star

Super Star

Image source: media.photobucket.com/ NatYu_2008

Star fish

star fish

Star fish

Image source: media.photobucket.com/FlipOtt

Star

star

Star

Image source: media.photobucket.com/mizspopular53
Similar image: media.photobucket.com/MiSSYOU_photo


A closer look at the star.

A closer look at the star.

A closer look at the star.

Image source: www.flickr.com/Lydia Elle

Black Star

Black Star

Black Star

Image source: www.flickr.com/ecstaticist

Sea Stars sunning

Sea Stars sunning

Sea Stars sunning

Image source: media.photobucket.com/ Lana_aka_BADGRL

Our awesome star

Our awesome star

Our awesome star

Image source: media.photobucket.com/TheJBROWN11