THE SUN The sun is the ball of fire in the sky that the Earth goes round, and that gives us heat the star that is the central body...
THE SUN
The sun is the ball of fire in the sky that the Earth goes round, and that gives us heat
the star that is the central body of the solar system, around which the planets revolve and from which they receive light and heat: its mean distance from the earth is about 93 million miles (150 million km)
the sun considered with reference to its position in the sky, its visibility, the season of the year, the time at which or the place where it is seen, etc.
SUN PROFILE
age: 4.6 billion years
diameter: 1,390,000 km.
mass: 1.989e30 kg
temperature: 5800 K (surface) 15,600,000 K (core)
ORIGIN OF THE SUN
Solar System Origins - Zoom Astronomy. A Globule of Gas: Our solar system formed about 5 billion years ago, from an enormous cloud of dust and gas, a nebula.The Sun, like other stars, was formed in a nebula, an interstellar cloud of dust and gas (mostly hydrogen).
A Globule of Gas:
Our solar system formed about 5 billion years ago, from an enormous cloud of dust and gas, a nebula.The Sun, like other stars, was formed in a nebula, an interstellar cloud of dust and gas (mostly hydrogen). These stellar nurseries are abundant in the arms of spiral galaxies (like our galaxy, the Milky Way).
In the stellar nursery, dense parts of the clouds undergo gravitational collapse and compress to form a rotating gas globule.
The globule is cooled by emitting radio waves and infrared radiation. It is compressed by gravitational forces and also by shock waves of pressure from supernova or the hot gas released from nearby bright stars. These forces cause the roughly-spherical globule to collapse and rotate. The process of collapse takes from between 10,000 to 1,000,000 years.
A Central Core and a Protoplanetary Disk:
As the collapse proceeds, the temperature and pressure within the globule increases, as the atoms are in closer proximity. Also, the globule rotates faster and faster. This spinning action causes an increase in centrifugal forces (a radial force on spinning objects) that causes the globule to have a central core and a surrounding flattened disk of dust (called a protoplanetary disk or accretion disk). The central core becomes the star; the protoplanetary disk may eventually coalesce into orbiting planets, asteroids, etc.
PROTOSTAR
A protostar is a very young star that is still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of stellar evolution. For a one solar-mass star it lasts about 1,000,000 years.
A Newborn Star and a Solar System:
When a temperature of about 27,000,000°F is reached, nuclear fusion begins. This is the nuclear reaction in which hydrogen atoms are converted to helium atoms plus energy. This energy (radiation) production prevents further contraction of the star.
Young stars emit jets of intense radiation that heat the surrounding matter to the point at which it glows brightly. These narrowly-focused jets can be trillions of miles long and can travel at 500,000 miles per hour. These jets may be focused by the star's magnetic field.
The protostar is now a stable main sequence star which will remain in this state for about 10 billion years. After that, the hydrogen fuel is depleted and the star begins to die.
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