Conjunction Junction (of the Planetary Function)


330px-Celestial_Conjunction_at_Paranal

When you look up at the stars at night, there are many things to gaze at. There is the Moon, countless stars, and 7 planets that orbit our Sun. Although the planets are quite far away by comparison, there are times when they appear quite close to one another in the sky. This phenomenon is known as a conjunction.

A conjunction can involve two or more planets, or the Moon with a planet or several planets. This provides a unique opportunity to spot and identify planets, even those that are difficult to spot, such as Mercury or Uranus. All of the planets, including Earth and the Moon orbit the Sun in the same general plane. However, this plane is not precisely the same, but it is close enough in astrological terms. That plane that stretches across our sky is called the ecliptic.

As the planets move around their orbits, and as the Earth moves around it’s orbit, the planets are always on the move across the sky. Sometimes, they appear near or behind the sun, other times they appear in the night sky. It all depends on their positions and the angles at which we can see them from Earth. Every so often though, the planets will “line up”, or appear close to one another.

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Jupiter and Venus in conjunction

Just a few months ago, there was a publicized conjunction between Venus and Jupiter. These conjunctions happen often, but usually not quite as close together. Everything lined up properly, and the two planets appeared unusually close, fitting in the same field of view in a telescope.

Conjunctions can help find those pesky hard to find planets. The Moon frequently passes near the planets in the sky. Using the Moon as a guide, finding planets like Uranus and Mercury becomes easier. A full moon usually hinders spotting deep space objects, but the planets are bright enough that the Moon won’t drown them out.

The most common conjunctions tend to involve Venus and Mercury, as they move quicky around the Sun. Jupiter takes 11 years to make a trip around the Sun, and Neptune has only made one complete trip since its discovery in 1846. Therefore, though conjuctions involving outer planets can and do happen, they are much more rare.

This month, there will be another close conjunction between Jupiter and Venus, this time occuring in the pre-dawn hours. This time around, Mercury and Mars will add to the show. Mercury and Mars will not be as close as Venus and Jupiter, but they’ll be nearby, giving early-birds a great chance to see 4 of the 5 naked-eye planets relatively close together in the eastern sky about an hour or so before dawn!

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Moon, Venus, and Mercury in conjunction

If you’re interested in finding the planets, keep an eye out for planetary conjunctions. It’ll allow you to see naked eye planets and positively identify them, and it will help you find the dimmer planets more easily with a brighter reference point. It’s pretty neat to see a grouping of our nearest celestial neighbors! See if you can spot conjunctions between planets, and also between the Moon and planets!

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Venus and Mars in conjunction, image taken by me

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