Wednesday, May 7, 2014

Which Planets are Visible to the Naked Eye?

If you have an elementary aged child, he/she has likely studied the planets of the solar system in class or read books about the planets.  I can't count the number of planet books my 7 year old has brought home from school or the library because the number is too high!  These books do a great job of teaching kids about the 8 Solar System planets:  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.  Pluto is missing because, unlike when I was a kid, Pluto is no longer an official planet.  More on this in a future post.

What's often missing from these books is a discussion on which planets are visible to the naked eye and which are not.  Since several of the planets are visible to the naked eye and are usually brighter than most of the stars in the sky, it's important to know which ones you can see without an observing aid.

The naked eye planets are Mercury, Venus, Mars, Jupiter, and Saturn.  Uranus and Neptune, as well as Pluto and other Pluto-like objects, all require a telescope to see.  Venus is brighter than all of the stars when present in the night sky.  Jupiter and Saturn can both be very bright.  Mars is a bit dimmer, but has a reddish appearance and is easy to find when it's out at night.  Mercury is the tough one.  Since it's a planet inside Earth's orbit and it is the closest planet to the Sun, it is always seen very close to the Sun in the sky.  Since the Sun floods the sky with light, Mercury can't be seen when the Sun is up.  It can only be seen just before the Sun rises, or just after the Sun sets.  Even then, it's very close to the horizon and requires a sky void of trees and buildings.

It's also important to note that planets are not always up at night.  They are just as likely to be up during the day as they are at night, and in the case of Mercury and Venus (inner planets), they are more likely to be up during the day than they are at night.  When up during the day, you can't see them, due to the Sun's much more intense light.

The next time your child brings home a book about the planets, or brings up the planets in a discussion, talk to them about which we can see and can't see in the sky.

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