Planet-Sun Orbital Diagram Label the aphelion (farthest point in orbit) and perihelion (closest point in orbit) of a planet in orbit. Answers

Since the Sun formed 4.5 billion years ago, it has used up about half of its initial hydrogen supply.

Our Sun is a seond or third generation star. Second generation stars do not just burn hydrogen, they also burn heavier elements, like helium and metals (elements heavier than hydrogen and helium), and were formed from supernova explosions (the debris of exploded population II stars).

The element helium was named after the Sun (called "Helios" in Greek) because it was first discovered on the Sun. Helium is plentiful on the Sun but rare on Earth. The element helium was discovered by Jules Janssen during the total solar eclipse of 1868 when he detected a new line in the solar absorption spectrum; Norman Lockyer suggested the name helium.

The composition of the Sun is studied using spectroscopy in which the visible light (the spectrum) of the Sun is studied.

NUCLEAR ENERGY PRODUCTION
At the Sun's core, nuclear fusion produces enormous amounts of energy, through the process of converting hydrogen nuclei into helium nuclei (nuclear fusion).

Although the nuclear output of the sun is not entirely consistent, each second the Sun converts about 600,000,000 tons of hydrogen nuclei into helium nuclei. These fusion reactions convert part of these atoms' mass (roughly 4 million tons) into energy, and release an enormous amount of this heat and light energy into the Solar System. In these fusion reactions, the Sun loses 4 million tons of mass each second. The Sun will run out of fuel in about 5 billion (5,000,000,000) years. When this happens, the Sun will explode into a planetary nebula, a giant shell of gas that will destroy the planets in the Solar System (including Earth).

AGE OF THE SUN
The Sun formed 4.5 billion years ago, as the solar system coalesced from a cloud of gas and dust.

STUDYING THE SUN
Astronomers study the Sun using special instruments. Scientists analyze how and why the amount of light from the Sun varies over time, the effect of the Sun's light on the Earth's climate, spectral lines, the Sun's magnetic field, the solar wind, and many other solar phenomena. The outer regions of the Sun (the corona) are studied during solar eclipses.

NEVER LOOK DIRECTLY AT THE SUN! Looking at the Sun can blind you or cause cataracts.

SOLAR EXPLORATION
The Ulysses spacecraft, a joint mission of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), was launched from the space shuttle on October, 1990 to explore the sun. It has studied the sun's magnetism, solar prominences and coronal mass ejections (orbiting over the south pole of the Sun in 1994 and over the north pole in 1995), and will will complete a second solar orbit in December, 2001.

Sun Activities
A quiz about the Sun

An interactive puzzle about the Sun

Label the Planet-Sun Orbital Diagram. Answers.