Is the sun a star?

The sun is a star with a diameter of 1, 390,000 km.

Mass: 1.989e30

Temperature: 5800 K (surface)

15.6 million (core)

The sun is the largest object in the solar system. It has 99.8% of the total mass of the solar system (Jupiter has most of the rest).

The sun is personified in many myths: the ancient Greeks called it the sun god, while the ancient Romans called it the sun god.

The mass of the sun is composed of 75% hydrogen and 25% helium (92. 1% atomic number is hydrogen and 7.8% helium); The total amount of other substances ("metals") is only 0. 1%. At the core of the sun, hydrogen is converted into helium, and these quantities change slowly.

The outer layer of the sun has different rotation periods: the equatorial plane rotates once every 25.4 days; The polar region reached 36 days. This strange phenomenon is because the sun is not a solid sphere like the earth, and a similar situation can be seen on gaseous planets. So in the sun, the rotation period is also different, but the core of the sun still rotates like a solid.

The state of the sun's core is amazing, with the temperature reaching15,600,000 Kelvin and the pressure equivalent to 250 billion atmospheres. The gas in the core is compressed to 150 times the density of water.

The energy released by the sun is 3.86e33 erg/s (3.86 trillion MW), which is produced by nuclear fusion reaction. Every second, about 700,000,000 tons of hydrogen atoms are converted into about 695,000,000 tons of helium atoms, and 5,000,000 tons of energy (= =3.86e33 erg) are released in the form of gamma rays. Because the radiation is emitted to the surface of the sphere, it constantly absorbs and emits energy, which makes the temperature drop continuously, so the temperature difference between inside and outside is huge, and it is basically visible light. The energy output by convection is at least 20% higher than that by radiation divergence.

The outer surface of the sun is called the photosphere, and the temperature is about 5800 K. Sunspots are "cool" places on the sun, only 3800 km (because they look darker than the surrounding areas). Sunspots can be very large, with a diameter of 50 thousand kilometers. Sunspots are produced by the complex and unknown action of the solar magnetic field.

A small area above the photosphere is called chromosphere.

The wide and thin material above chromosphere is called a solar halo, which extends into space for millions of kilometers, but can only be observed during the solar eclipse (left). The internal temperature of the solar flare exceeds 1 1,000,000 K.

The solar magnetic field is extremely powerful (by the standards of the earth) and very complicated. Its magnetosphere is even much larger than Pluto.

In addition to light and heat, the sun also emits low-density particle streams (mostly electrons and protons) to form a solar wind, which propagates in the solar system at a speed of 450 km/s. When the solar wind and high-energy particles shine on the sun, it will have an impact on tidal waves and radio communication on the earth, and will produce aurora.

Recent data from the Ulysses spacecraft show that the speed of solar wind diverging from the poles has doubled to 750 km/s, which also occurs in low latitudes. The composition of the solar wind in the polar regions is also different, and the solar magnetic field seems surprisingly unstable.

More research on the solar Wind will be completed with the help of Wind, ACE and SOHO spacecraft in the near future. They will take advantage of dynamic stability and be located directly between the earth and the sun, 65,438+0,600,000 kilometers away from the earth.

The solar wind causes comets to produce tails, and sometimes even has measurable effects on the orbit of spacecraft.

Spectacular annular protrusions, corona, also often appear at the edge of the sun. (Left)

The energy output of the sun is unstable, and the number of sunspot activities is also unstable. /kloc-there was an unusually weak sunspot activity period in the second half of the 0/7th century, which was consistent with the abnormal low temperature period (Little Ice Age) in northern Europe at that time. Since the formation of the sun, energy output has increased by 40%.

The sun is 4.5 billion years old. Since its birth, it has used half of the hydrogen atoms in its core. It will still radiate "gently" for about 5 billion years (although the brightness will be twice as high as it is now), but it will eventually run out of energy. At that time, it will be in an extremely unstable state, and with the change of state, it will eventually destroy the earth (possibly forming a brand-new planetary system).