# Five Little Planets All In A Row

In Astronomy by Brian Koberlein3 Comments

If you look to the east a bit before sunrise, you’ll be able to see five planets roughly in a line. Mercury will be the most difficult to observe, and might not be seen by many observers, but Venus, Saturn, Mars, and Jupiter should be easily seen if the sky is clear.

The occurrence has been called a planetary alignment by many, but that’s a bit of a misnomer. The planets aren’t arranged in a line within the solar system, it’s just that from Earth’s vantage point they appear in the same general direction. It’s an unusual event, but not particularly rare.

What’s interesting about this event is that it gives you a good idea of an imaginary line in astronomy known as the ecliptic. The ecliptic is the path the Sun traces through the sky over the course of a year. It marks the plane of Earth’s orbit around the Sun. Since the orbital planes of the Moon and planets have a similar orientation, the Sun, Moon, and planets all move through the sky roughly along the ecliptic. Historically that’s why this region of the sky was seen as astrologically significant, and why the zodiac constellations all have the ecliptic passing through them.

So if you get a chance, it’s worth checking out sometime before the end of the month. It’s a nice perk if you have to get up before dawn anyway.

1. Yep. Been watching this develop every morning when I walk the dog. He sniffs the ground and I look at the sky. Saturn was right on top of Venus a few weeks back. I can’t see Mercury because it’s obscured by Philadelphia.

2. Brian, is there any chance that all the eight planets get aligned in a plane perpendicular to the ecliptic? I’m thinking about multiplying each orbital period to guess how many years have to pass to look for such aligment…

3. Already did the math… It would take 1.15 cuatrillon years (one billon = 10^12 in my country), 8.4.10^13 times the actual age of the Universe… so the answer is: no way!!!