Here’s a useful phrase for all of you stargazers. Scouts learn this phrase. Grandparents teach it to kids. It was one of the first sky tools I learned to use in astronomy. The phrase is: follow the arc to Arcturus and drive a spike to Spica. In 2014, you might also add … and locate the red planet Mars. And you want to locate Mars! It’s now at its best for this two-year period, plus it’ll be near the moon in eclipse later this month. Follow the links below to learn more.
Follow the arc to Arcturus. Here’s how to locate the star Arcturus, using the Big Dipper as a guide. Find the Big Dipper asterism in the northeastern sky in mid-evening this month, maybe around 9 p.m. It’s very easy to see, a large noticeable dipper-shaped pattern in the northeast in the evening. Once you can see the Big Dipper, notice that it has two parts: a bowl and a handle. Then, with your mind’s eye, draw an imaginary line following the curve in the Dipper’s handle until you come to a bright orange star: follow the arc to Arcturus. Arcturus is the brightest star the constellation Bootes the Herdsman. This star is known in skylore as the Bear Guard.
Arcturus is a giant star with an estimated distance of 37 light-years. It’s special because it’s not moving with the general stream of stars in the flat disk of the Milky Way galaxy. Instead, Arcturus is cutting perpendicularly through the galaxy’s disk at a tremendous rate of speed . . . some 150 kilometers per second.
Millions of years from now this star will be lost from the view of any future inhabitants of Earth, or at least those who are earthbound and looking with the eye alone.
Drive a spike to Spica. Once you’ve followed the curve of the Big Dipper’s handle to the star Arcturus, you’re on your way to finding the star Spica, and Mars. Just extend that same curve on the sky’s dome. You can read more about Spica here.
In 2014, use this tool to find Mars. The planet Mars is now at its best for 2014. In fact, since the cycle of Mars’ appearance in our sky is two years long, it’s now at its best for this two-year period. And we’re in luck. Mars is right next to Spica on the sky’s dome. You can probably identify Mars this month just by looking generally eastward for the brightest, reddest bad boy up there. That’ll be Mars. But if you need confirmation: Follow the arc to Arcturus and drive a spike to Spica. Mars will be there, too.
Earth will pass between Mars and the sun on April 8. That’s why Mars appears so bright in our sky now, because the distance between our two worlds is relatively small. April 8 is the martian opposition, when Mars will appear opposite the sun in our sky. Read about Mars’ opposition here.
Then mark your calendar! On the night of April 14-15, there will be a total eclipse of the moon, visible from the Americas. You’ll have to stay up late to see it. But if you take the trouble to watch you’ll be rewarded with the sight of the red planet Mars, right next to the eclipsed moon! That’ll be something to see. Read more about the April 14-15 total lunar eclipse.
Bottom line: Use the curve in the handle of the Big Dipper to “follow the arc” to the star Arcturus. Then “drive a spike” to the star Spica. In 2014, you’ll can identify the planet Mars this way, too. Have fun.