Mercury makes its way into the evening sky, visible shortly after sunset for the next few weeks. The fleet-footed planet never strays far from the Sun from our point of view, so we get glimpses of Mercury in the evening, then the morning before sunrise, and again in the evening several times a year. Right now Mercury is going to be easy to find because it will move near Venus this week. Venus is the bright evening "star" in the west, shining through the glow of dusk, and Mercury, although dimmer, will be fairly easy to spot now that you know where to look.
It's time for the first full moon of Spring, rising up to dominate the sky Monday evening. The first full moon following the Vernal Equinox (the moment when Spring arrived on March 20th) marks the arrival of Passover and Easter week, holidays that are based on lunar calendars. The Moon passes near Saturn on its trek across the eastern sky in the early evening on the 28th and 29th, and then onward toward the bright star Spica on the 30th. The Moon is full at exactly 7:25 pm pacific time on Monday 29th.
One of the highlights of the winter sky is the Winter Triangle. This shape is a nearly perfect equilateral triangle that shines in the southern sky over the next few months. It includes three of the most brilliant stars in the sky, and it is called an "asterism" because it is not a single constellation, but a combination of stars from three different constellations.
The first and brightest star is Sirius, the brightest star in the night sky. Sirius is close to the Solar Systems (8 light years) and has a slight blue coloration. Sirius is in the constellation Canis Major, the big dog that accompanies Orion. To the upper right is Betelgeuse, a red supergiant star in Orion that is a distinctive orange color. Betelgeuse is so big that if it was our Sun, it would envelop Mercury, Venus, Earth and Mars! And the third star of the triangle is Procyon, in the constellation Canis Minor, the small dog that accompanies Orion. Procyon is actually a double-star system with a faint partner star.
Inside the Winter Triangle you can find numerous clusters of stars. I spent some time looking here a few nights ago and was able to see quite a few of these clusters, even in San Francisco. My backyard has a dark western horizon so by looking through binoculars later in the evening I was able to see quite a bit in and around the asterism. Try this for yourself sometime soon.
There are many ways to take your interest in astronomy up a notch. Here are a few things that are sure to enhance your interest and knowledge of the skies.
Globe at Night: I am a big fan of this annual project, one that combines astronomy with awareness of light pollution and is also a global participation project. Go outside tonight and look up at Orion, then report what you see at the Globe at Night website. It only will take a few minutes but it will change how you see the sky at night. I am certain about this one.
Continuing from the last post, here's a snapshot of the Moon continuing on its journey across the morning sky, a series of guideposts to the Ecliptic. The view is what you would see around 5:30 am each morning here in San Francisco.
In 2005 I began writing a column for the San Francisco Waldorf School newsletter called "The Urban Astronomer." I started this blog in 2007 as a place to archive my articles and to offer additional insights on the night sky - even if you live in a big city. In 2008 I became an occasional guest on the KFOG Morning Show, and more recently on KALW and KGO. Archived shows are posted on the blog.