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A Guide to the Night Sky: May 2016


A Guide to the Night Sky
May 2016 

By Tre Gibbs, LAAS

“Blue Moon….you left me standing alone…”

Remember that song?  Well this month we will have a blue moon - on May 21st.  

What exactly is a blue moon?   Well, for starters, it isn’t a color reference.   Let me try to explain this….   First of all, the Moon. It’s about 240,000 miles away, so if you drove your car at a 70 mph, it would take you roughly 4 months and three weeks driving non-stop to get there (no bathroom breaks). It orbits our planet and takes roughly 28 days, or about one month to make one full orbit around Earth - you may (or may not) have noticed that it rises a little later each night.

FUN FACT: Our word “month” comes from “moon”.

Secondly, let’s bring in the seasons.  Each season is about three months long, so we usually get three full moons in a particular season. But every once in a while (or once in a “blue moon”), we get four full moons in a season. Well, the THIRD full moon in a season is referred to as “blue”, so that’s what a blue moon is.  Though rare, and only happening once in a while, it has absolutely no effect on us humans down here.  It’s not bigger, it’s not closer and most importantly it’s not actually the color blue. 

However, this blue moon does have an added significance - this “blue moon” will be traveling the night sky with two wandering guardians, the planet Mars to the right and the planet Saturn to the left.

FUN FACT: The word “planet” comes from the Greek word for “wander”.

The trio will rise in the east together on May 21st. just after sunset around 8:00 pm or so.  Look for them a little later, after the sky is dark, to see their magnificence.  Mars, though small and dim, will be slightly orangish, and Saturn, also pretty small, will have a barely discernible beige-ish hue. The bright, twinkling star Antares will be below the Moon and Mars, and the four objects together make a square shape. For all of you Scorpios out there, Antares is The Heart of the Scorpion, FYI.  Try not to miss this, though if you do, you can check out the Moon, Mars and Saturn the following night, May 22nd., although the Moon, slowly gliding east, will be to the left of Saturn.

The moon also does it’s monthly pairing with the planet Jupiter.  Earlier in the month, look for the moon and Jupiter appearing high in the south at dusk on the evening of the 14th as they travel across the night sky as a celestial duo. Jupiter will be the bright, non-twinkling, star like object just to the left of the moon.

FUN FACT: Stars twinkle - planets don’t.

But let’s go back to the planet Mars for a moment. Later this month, Mars will be at “opposition”, which means that Mars is “opposite” the sun, relative to us. Just like when the moon is full, it’s because it’s opposite the sun relative to Earth. From our perspective here on Earth, this appears as Mars rising in the east at sunset, being directly overhead around 12:00 am midnight and 

setting in the west when the sun rises. However, as the weeks and months go by, and as Earth continues it’s orbit around the sun (which is slightly faster than Mars’ orbit around the sun), Mars will rise earlier and earlier, and will drift off to the west sooner and sooner, as Earth glides past “The God of War”.

Have a fantastic month and remember to look up at the wondrous show going on overhead every night.