Sun
hideThe Sun is the star at the center of the Solar System. The Earth and other matter (including other planets, asteroids, meteoroids, comets, and dust) orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass. The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (93.0 million miles), and its light travels this distance in 8 minutes and 19 seconds. This distance varies throughout the year from a minimum of 147.1 million kilometers (91.4 million miles) on the perihelion (around 3 January), to a maximum of 152.1 million kilometers (94.5 million miles) on the aphelion (around 4 July). Energy from the Sun, in the form of sunlight, supports almost all life on Earth via photosynthesis, and drives the Earth's climate and weather. The Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24% of mass, 7% of volume), and trace quantities of other elements, including iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium, and chromium.
The Sun has a spectral class of G2V. G2 means that it has a surface temperature of approximately 5,780 K (5,510 °C) giving it a white color, which often appears as yellow when seen from the surface of the Earth because of atmospheric scattering. It is this scattering of light at the blue end of the spectrum that gives the surrounding sky its color. The Sun's spectrum contains lines of ionized and neutral metals as well as very weak hydrogen lines. The V (Roman five) in the spectral class indicates that the Sun, like most stars, is a main sequence star. This means that it generates its energy by nuclear fusion of hydrogen nuclei into helium. There are more than 100 million G2 class stars in our galaxy. Once regarded as a small and relatively insignificant star, the Sun is now known to be brighter than 85% of the stars in the galaxy, most of which are red dwarfs.
The Sun's hot corona continuously expands in space creating the solar wind, a hypersonic stream of charged particles that extends to the heliopause at roughly 100 AU. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.
The Sun is currently traveling through the Local Interstellar Cloud in the low-density Local Bubble zone of diffuse high-temperature gas, in the inner rim of the Orion Arm of the Milky Way Galaxy, between the larger Perseus and Sagittarius arms of the galaxy. Of the 50 nearest stellar systems within 17 light-years (1.6×1014 km) from the Earth, the Sun ranks 4th in mass as a fourth magnitude star (M = +4.83)., although slightly different values for the magnitude have been published, for example 4.85 and 4.81. The Sun orbits the center of the Milky Way galaxy at a distance of approximately 24,000–26,000 light years from the galactic center, moving generally in the direction of Cygnus and completing one revolution in about 225–250 million years (one Galactic year). Its orbital speed was thought to be 220 ± 20, km/s but a new estimate gives 251 km/s. Since our galaxy is moving with respect to the cosmic microwave background radiation (CMB) in the direction of Hydra with a speed of 550 km/s, the sun's resultant velocity with respect to the CMB is about 370 km/s in the direction of Crater or Leo.
For more information about Sun, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with sun
Sharpest views of Betelgeuse reveal how supergiant stars lose mass
Jul 29, 2009 |
4.8 / 5 (31) |
78
(PhysOrg.com) -- Betelgeuse -- the second brightest star in the constellation of Orion (the Hunter) -- is a red supergiant, one of the biggest stars known, and almost 1000 times larger than our Sun. It is ...
Largest Ring Around Saturn Discovered
Oct 07, 2009 |
4.7 / 5 (32) |
12
(PhysOrg.com) -- NASA's Spitzer Space Telescope has discovered an enormous ring around Saturn -- by far the largest of the giant planet's many rings.
Mystery of the Solar Tsunami -- Solved (w/ Video)
Nov 19, 2009 |
4.9 / 5 (27) |
9
(PhysOrg.com) -- Sometimes you really can believe your eyes. That's what NASA's Solar Terrestrial Relations Observatory (STEREO) is telling researchers about a controversial phenomenon on the sun known as ...
Our Sun: A Little Slow On the Uptake for Cycle 24
Apr 27, 2009 |
4.5 / 5 (28) |
26
A very recent article carried by the BBC called, 'Quiet Sun Baffling Astronomers' sent me in a twitter of research activity. The BBC article's head notes include "The Sun is the Dimmest It Has Been for Nearly ...
The sun is a star when it comes to sustainable energy
Feb 25, 2009 |
4.2 / 5 (25) |
56
At a national scientific meeting last week where biofuels - principally ethanol - were uniformly trashed as an environmental train wreck, one bright, carbon-free light gleamed in our energy future: the sun.
Spotless Sun: Blankest Year of the Space Age
Space & Earth / Space Exploration
Oct 01, 2008 |
4.5 / 5 (23) |
2
Astronomers who count sunspots have announced that 2008 is now the "blankest year" of the Space Age.
NASA Spacecraft Finds the Sun is Not a Perfect Sphere
Space & Earth / Space Exploration
Oct 02, 2008 |
4 / 5 (26) |
6
(PhysOrg.com) -- Scientists using NASA’s RHESSI spacecraft have measured the roundness of the sun with unprecedented precision. They find that it is not a perfect sphere. During years of high solar activity ...
Long-standing sunspot puzzle solved
Space & Earth / Space Exploration
Aug 19, 2009 |
4.5 / 5 (20) |
4
(PhysOrg.com) -- Scientists at the Universities of Glasgow, Strathclyde and Central Lancashire have used 21st Century solar observations and image processing to finally solve a sunspot puzzle first noticed ...
A bubbling ball of gas (w/ Video)
Space & Earth / Space Exploration
Nov 11, 2009 |
4.9 / 5 (18) |
7
The Sun is a bubbling mass. Packages of gas rise and sink, lending the sun its grainy surface structure, its granulation. Dark spots appear and disappear, clouds of matter dart up - and behind the whole thing ...
SOHO discovers its 1,500th comet
Space & Earth / Space Exploration
Jun 27, 2008 |
4.2 / 5 (21) |
0
The ESA/NASA SOHO spacecraft has just discovered its 1500th comet, making it more successful than all other comet discoverers throughout history put together. Not bad for a spacecraft that was designed as a ...
Gravity wells could provide 'parking lots' for spaceships
Space & Earth / Space Exploration
Jul 15, 2009 |
4.4 / 5 (19) |
22
Nature has provided five huge rest stops far out in space for the convenience of spacecraft traveling from Earth. Some NASA folks call them "parking lots" in space.
Does too much sun cause melanoma?
Jul 23, 2008 |
4.2 / 5 (20) |
1
We are continuously bombarded with messages about the dangers of too much sun and the increased risk of melanoma (the less common and deadliest form of skin cancer), but are these dangers real, or is staying out of the sun ...
The sun could be having a 15% or 20% effect on climate change
Space & Earth / Earth Sciences
Jul 18, 2008 |
2.9 / 5 (27) |
11
Global warming is mainly caused by greenhouse gas emissions resulting from human activities; however, current climatic variations may be affected “around 15% or 20%” by solar activity, according to the researcher Manuel Vázquez ...
'Printed chips' could be boon for consumers
Aug 12, 2009 |
4.6 / 5 (16) |
4
Until now, creating the microchips that power all of our electronic gadgets has been a laborious, complex and time-consuming process costing billions of dollars. But if a Milpitas, Calif.-based startup succeeds, making them ...
The Good Vibrations of Nearby Stars
Oct 23, 2008 |
4.5 / 5 (16) |
0
Some of the first data collected by the CoRoT space telescope mission, launched in December 2006, provides valuable information about the physical vibrations and surface characteristics of nearby stars that ...
