Sunday, February 12, 2017

Milky Way in the Night Sky

Summer Milky Way and Galactic Core
The Milky Way is the galaxy we live in.  It is also HUGE!  Both in actual size and how large it is in the sky.  I often photograph it with a fisheye lens it is so big!

Finding the Milky way in the night sky is actually pretty easy.  Go outside and look is the simple advice.

Ok, maybe it is not quite that easy........  The Milky Way is visible every month of the year but you really need dark sky to see it.  That means getting away from the city and it helps when there is not a bright moon in the sky.  

Really you can observe it about three weeks a month with just a few days either side of the full moon being less than good viewing conditions.  Of course the days around the new moon will give you the longest nights of dark sky and are the best time to see the Milky Way.

Winter view Spiral Arm
So go outside at night close to the new moon helps.  But just because you can see stars it does not mean it is dark enough.

After sunset you need to wait for astronomical twilight which is roughly 90 minutes after sunset.  It takes the sky that long to get dark.  Then in the morning about 90 minutes before sunrise you begin to lose the night sky.

It also helps to find dark sky.  Get away from the city.  You need at least 30 miles.  At that distance I can see the Milky Way but often get light pollution.  When you find true dark sky areas then the magic of the night sky really appears.  Google dark sky map or light pollution map to find some sites like DarkSiteFinder to see maps of light pollution.  If you live east of the Mississippi River in the US or pretty much anywhere in western Europe you see very little dark sky.  Those west of the Mississippi or in western Australia can find some very dark sky.

Another thing to know is the Milky Way is visible at different times of the night and in different parts of the sky in different times of the year.  Make sense?

We can see the galactic core of our galaxy which is the best and brightest part of the Milky Way.  It runs between the constellations Sagittarius (also known as the Tea pot)  in the southern half of the sky in summer and Cassiopeia in the north.  Cassiopeia spins around the North Star opposite the Big Dipper.  We can also see one of the spiral arms of our galaxy between Cassiopeia (still in the north) and Orion in southern half of the sky in winter.  The spiral arm is not near as bright as the galactic core but it can be seen. Especially if you find very dark sky.

So here in February, if you go outside about two hours after sunset in a reasonably dark sky area you will see the spiral arm of the Milky Way from the northwest.  Remember this is the less bright part.    Look for Cassiopeia and Orion.  If you went back outside at 5am you would start to see the galactic core rise in the east right before night faded.

In June if you went outside about 11pm you would see the galactic core rising in the east and be visible the rest of the night.

In October if you went outside two hours after dark you would see the galactic core setting in the southwest.  The Milky Way will still be visible but the best part is now below the horizon.

Galactic core in the west in the fall
In December if you went outside after dark you would see Orion rising in the east and the Milky Way going to the northwest toward Cassiopeia and beyond.  Again the best part has set but it is still visible.

A general rule I use is in the spring the Milky Way is best visible in the morning in the east the week after the new moon.  In the fall it is best visible to the west in the evening the week leading into the new moon.

Check out apps like Stellarium, Google Sky, Photo Pills and many others to help you see and find the night sky.

Want to learn more about the Milky Way?  Check out this by NASA on our Galaxy:
NASA on the Milky Way