Stars are large celestial bodys gravitationally contained hot gases emitting electromagnetic radiation,especially light,as a result of nuclear reactions inside the star.As far as I know,the Sun which is a star,is in a fixed position.The balance of stars seem to be in a fixed position, but in fact they are not.This is due to the fact that their distances are so great that there relative changes become apparent only over the centuries.The star nearest to our solar system is the triple star Proxima Centauri which is about 25 trillion miles from earth or about 4.29 light years away.A light year is the distance light travels in one year at 186,000 miles per second!So to go to Proxima Centauri its about 4 years and 3 months.
The Sun is a typical star,with a visable surface called a photosphere,an overlyiny atmosphere of hot gases,and above them a more diffuse corona and an outflowing stream of particles called the steller wind.Temperatures vary a lot from core to the surface and beyond,like several million degreees difference.
Nobody,until now,knew what was causing the dramatic increase in temperature.Professor Eric Priest of St Andrews University in Scotland and colleagues in Britain and France said a clash of magnetic fields was heating giant,super-hot loops that extend over the sun's surface to produce the extreme temperatures.Priest said the explosions occur in tiny regions of intense electric current that heat up the atmosphere in the same way as an electric current in a light bulb or electric fire.
Heres a little info on the above picture.First of all this picture was taken with the Hubble Space Telescope.Clusters of stars and a fishhook-shaped cloud of luminescent gases glow brilliantly in NGC 2363 a giant star-forming region in the Magellanic galaxy NGC 2366. Though the nebula is 10 million light-years away, the Hubble Space Telescope resolves details comparable to such nebulae in our own galaxy.What a great telescope!This monstrous star (30 to 60) times as massive as the Sun) is in a very unstable,eruptive phase of its life.This picture was taken in January 1996.An archival search showed the star grew 40 times brighter,now making it the brightest star in its galaxy.
HUBBLE CAPTURES THE HEART OF STAR BIRTH
NASA Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2) has captured a flurry of star birth near the heart of the barred spiral galaxy NGC 1808.
On the left are two images, one superimposed over the other. The black-and-white picture is a ground-based view of the entire galaxy. The color inset image, taken with the Hubble telescope's Wide Field and Planetary Camera 2 (WFPC2), provides a close-up view of the galaxy's center, the hotbed of vigorous star formation.
The ground-based image shows that the galaxy has an unusual, warped shape. Most spiral galaxies are flat disks, but this one has curls of dust and gas at its outer spiral arms (upper right-hand corner and lower left-hand corner). This peculiar shape is evidence that NGC 1808 may have had a close interaction with another nearby galaxy, NGC 1792, which is not in the picture Such an interaction could have hurled gas towards the nucleus of NGC 1808, triggering the exceptionally high rate of star birth seen in the WFPC2 inset image.
The WFPC2 inset picture is a composite of images using colored filters that isolate red and infrared light as well as light from glowing hydrogen. The red and infrared light (seen as yellow) highlight older stars, while hydrogen (seen as blue) reveals areas of star birth. Colors were assigned to this false-color image to emphasize the vigorous star formation taking place around the galaxy's center. NGC 1808 is called a barred spiral galaxy because of the straight lines of star formation on both sides of the bright nucleus. This star formation may have been triggered by the rotation of the bar, or by matter which is streaming along the bar towards the central region (and feeding the star burst).
Filaments of dust are being ejected from the core into a faint halo of stars surrounding the galaxy's disk (towards the upper left corner) by massive stars that have exploded as supernovae in the star burst region. The portion of the galaxy seen in this "wide-field" image is about 35,000 light-years across. The right-hand image, taken by WFPC2, provides a closer look at the flurry of star birth at the galaxy's core. The star clusters (blue) can be seen (and many more are likely obscured) amid thick lanes of gas and dust. This image shows that stars are often born in compact clusters within star bursts, and that dense gas and dust heavily obscures the star burst region. The brightest knot of star birth seen here is probably a giant cluster of stars, about 100 light-years in diameter, at the very center of the galaxy. The other star clusters are about 10 to 50 light-years in diameter. The entire star burst region shown here is about 3,000 light-years across.
This galaxy is about 40 million light-years away in the southern constellation Columba. The observation was taken Aug. 14, 1997, and was the last of 13 Hubble Space Telescope amateur programs.
Credits: Jim Flood, an amateur astronomer affiliated with Sperry Observatory at Union College in New Jersey, and Max Mutchler, a member of the Space Telescope Science Institute staff who volunteered to work with Jim.