Реферат: Solar System Essay Research Paper The Sun

Solar System Essay, Research Paper

The Sun is an ordinary G2 star, one of more than 100 billion stars in our galaxy.

diameter: 1,390,000 km.

mass: 1.989e30 kg

temperature: 5800 K (surface)

15,600,000 K (core)

The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total

mass of the Solar System (Jupiter contains most of the rest).

The Sun is personified in many mythologies: the Greeks called it Helios and the Romans called it

Sol.

The Sun is, at present, about 75% hydrogen and 25% helium by mass (92.1% hydrogen and

7.8% helium by number of atoms); everything else (”metals”) amounts to only 0.1%. This changes

slowly over time as the Sun converts hydrogen to helium in its core.

The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once

every 25.4 days; near the poles it’s as much as 36 days. This odd behavior is due to the fact that the

Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential

rotation extends considerably down into the interior of the Sun but core of the Sun rotates as a solid

body.

Conditions at the Sun’s core are extreme. The temperature is 15.6 million Kelvin and the pressure

is 250 billion atmospheres. The core’s gases are compressed to a density 150 times that of water.

The Sun’s energy output (3.86e33 ergs/second or 386 billion billion megawatts) is produced by

nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about

695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma

rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at

lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light.

For the last 20% of the way to the surface the energy is carried more by convection than by

radiation.

The surface of the Sun, called the photosphere, is at a temperature of

about 5800 K. Sunspots are “cool” regions, only 3800 K (they look dark

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