Stargazing this Week
This was originally published in our Weekly Newsletter. Each weekend we’ll treat you to stargazing tips and the latest physics news. You can sign up here! Also check out Stellarium for an open-source star map.
As we enter the middle of spring, nights in the northern hemisphere suddenly feel very short. Take heart, stargazers! There’s still plenty to see in the sky if you’re willing to stay out a bit later.
Hercules and M13
This week, look for the constellation Hercules. It’s high in the sky, and as an collection of stars the poor fellow looks more like an ocean creature than a mythical hero. To find Hercules, look East a bit after sunset. The brightest star you see is probably Vega. You’ll find Hercules just up and to the right from Vega. If you go too far in that direction, you’ll find the bright star Arcturus. For our friends down under of course, you’ll see the reverse. Hercules just barely pops over the northern horizon late in the night.
Look for its central, “keystone” asterism, near the bright star Vega. Along the “top” of the keystone square - in the Northern Hemisphere anyway - you can find the globular cluster M13.
M13 is a massive collection of old stars, bound tightly together by gravity. As a cluster is orbits our own Milky Way. M13 is so dense with stars that it may be difficult to resolve, even with a telescope. M13’s apparent magnitude is 5.8, meaning you can spot it by eye with dark conditions. But bring the binoculars, just in case.
Scorpius, M4 and the Messier Catalog
We don't often talk about the Southern sky, so here's another fun observing objective for the week: Scorpius. This time of year, the constellation Scorpius doesn’t quite make it all the way above the horizon, but its mandibles will. That means the bright star you see on the southern horizon is Antares. Just next to Antares is another globular cluster M4, which is about the same magnitude as M13. The brightest stars in M4 just on the cusp of needing a telescope to resolve. Nevertheless its a fairly large sized hazy ball of light accessible by binoculars and worth looking for!
Incidentally, the "M" in M4 and M13 stands for Messier, meaning these two clusters belong to the Messier Catalog of astronomical objects. The 18th Century French astronomer Charles Messier published the locations of these beasts to warn folks away from searching for comets there. He was obsessed with comets. He found 13. The Messier Catalog is his real legacy, and has 110 objects. You never know what your contribution to Science might be.
The Inner Planets at Sunset
Mercury, Venus and Mars are all out at sunset this week. With a new moon on the 11th, the skies will be dark and you’ll be able to see them clearly. Look to the west at sunset. The bright object is Venus. Fainter Mercury is nearby. Mars is up higher along the ecliptic, near our friends Gemini.
The waxing Crescent moon will follow the track between the planets as the week evolves, which could make for some great night sky photography.
