Astronomy Facts

Mars is called the Red Planet because of the iron oxide (rust) on its surface, which gives it a reddish appearance when viewed from Earth.

The Sun is the closest star to Earth, at an average distance of about 93 million miles (150 million kilometers). The next closest star system is Alpha Centauri, about 4.37 light-years away.

There are 8 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was reclassified as a dwarf planet in 2006.

Our solar system is located in the Milky Way galaxy, a barred spiral galaxy estimated to contain 100-400 billion stars and spanning about 100,000 light-years in diameter.

Jupiter is the largest planet in our solar system, with a diameter of about 86,881 miles — more than 11 times that of Earth. It is so large that all other planets could fit inside it.

A solar eclipse occurs when the Moon passes between the Sun and Earth, casting a shadow on Earth. During a total solar eclipse, the Moon completely blocks the Sun's face.

Saturn has the most extensive and spectacular ring system in our solar system. The rings are made primarily of ice particles, with smaller amounts of rocky debris and dust.

A light-year is a unit of distance, not time. It is the distance that light travels in one year, approximately 5.88 trillion miles (9.46 trillion kilometers).

Neil Armstrong became the first person to walk on the Moon on July 20, 1969, during the Apollo 11 mission, famously saying: 'That's one small step for man, one giant leap for mankind.'

Halley's Comet is a short-period comet that is visible from Earth every 75-79 years. It last appeared in 1986 and is expected to return in 2061.

The heliopause is the boundary where the Sun's solar wind is stopped by the interstellar medium. Voyager 1 crossed this boundary in 2012, becoming the first human-made object to enter interstellar space.

Europa, one of Jupiter's four Galilean moons, is believed to have a vast saltwater ocean beneath its icy surface. Scientists consider it one of the most promising places to search for extraterrestrial life.

The universe is estimated to be approximately 13.8 billion years old, based on observations of the cosmic microwave background radiation and the expansion rate of the universe.

A black hole is the densest type of stellar remnant, formed when a very massive star collapses under its own gravity. Its gravitational pull is so strong that nothing, not even light, can escape.

The Hubble Space Telescope, launched on April 24, 1990, has revolutionized astronomy with its stunning visible-light images and has helped determine the age and expansion rate of the universe.