Articles About Planets (20)

Astronomy Glossary - Terms & definitions

Astronomical Glossary - Terms & Definitions

What do astronomers really mean when they use those technical terms?

Illustration of altitude and azimuth in the celestial sphere.

Altitude & Azimuth: The Horizontal Coordinate System

Learn how to use altitude (elevation) and azimuth angles to locate any object in the sky, such as stars, planets, satellites, the Sun, or the Moon.

Mercury Transit

When Mercury transits the Sun, you can see it as a tiny black dot silhouetted against the Sun's disk. The last Mercury transit was on November 11, 2019.

Transit of Venus: June 5-6, 2012

The 2012 Venus transit was the last chance to see this phenomenon for over 100 years. Mercury transits happen more often, the next one in 2032.

Jupiter and Venus Closest Conjunction of 2015

From time to time, some of the planets in our solar system are in conjunction and become visible together in the sky. Venus, Jupiter, Mars, and Mercury have all been visible in the early mornings of October 2015.

An image of the solar system showing the alignment of the Earth, Jupiter, and Saturn for the Great Conjunction of 2020.

What Is a Conjunction?

A conjunction is when planets like Mars, Jupiter, or Saturn, or other bodies like stars or the Moon, meet in the sky. Why and when do conjunctions happen?

A view from our Night Sky Map of totality over the US city of Dallas at 13:42 (local time) on April 8, 2024.

What Is the Ecliptic?

The ecliptic is the name given to the path the Sun follows through the stars and constellations over the course of a year.

The Moon: Our Satellite

Our Moon is the 5th-largest of the more than 200 moons in the solar system.

Gravity Assists

A gravity assist maneuver is where a planet helps a spacecraft gain or lose speed.

Screenshot of timeanddate.com's Night Sky Map for December 21, 2020, shortly after sunset in the northern hemisphere.

Great Conjunction 2020

In December 2020, Jupiter and Saturn met in the sky in a rare Great Conjunction.

An image from our Night Sky Map showing all five naked-eye planets

What Is a Planet?

A celestial body needs to pass three tests to be called a planet.

NASA technicians work on the New Horizons spacecraft at the Kennedy Space Center in November 2005.

The Solar System

Everything that orbits the Sun is part of the solar system.

Mars: The Red Planet

Mars is the outermost of the Solar System’s small inner planets.

Venus captured by NASA's Mariner 10 spacecraft

Venus: Our Twin Planet

There is much that is similar—and much that is different—between Venus and Earth.

Earth: The Living Planet

Earth is the largest of the Solar System’s rocky inner planets.

A mosaic of Saturn made up of images taken by the Cassini spacecraft in October 2016.

Saturn: The Ringed Planet

Saturn is easily visible with the naked eye, although a small telescope is required to see its rings.

A close-up of Uranus, taken by the Voyager 2 spacecraft in January 1986.

Uranus: The Sideways Planet

Uranus is the seventh planet from the Sun. It was the first “new” planet to be discovered.

A mosaic of images of Mercury taken by NASA's MESSENGER spacecraft.

Mercury: The Iron Planet

Mercury, which is made mostly of iron, is the smallest planet, and the closest to the Sun.

Jupiter and its moon Europa, as seen by the Hubble Space Telescope on August 25, 2020

Jupiter: The Massive Planet

Jupiter is fifth in line from the Sun, and the largest planet in the solar system.

Image of Neptune against a black background.

Neptune: The Farthest Planet

Neptune is too far away to be seen with the naked eye, but a good pair of binoculars can capture it.