Moon to Occult Aldebaran

Moon Occulting a Star

Astronomical alignments are special events, times when the motions of the Earth and the rest of the cosmos brings about a particularly interesting juxtaposition of objects in the sky. Today (Sunday 10 April) the waxing crescent Moon will align itself with the bright star Aldebaran, covering it completely for observers in various parts of North America. See this article from Sky & Telescope for a detailed overview of the cities and the exact timing for disappearance and reappearance of Aldebaran.

The Moon sweeps around the entire night sky and touches each constellation of the Zodiac every month, passing in front of hundreds of naked-eye visible stars during its journey. But it is very uncommon for the Moon to pass in front of the brightest stars in the night sky. Aldebaran is a 'first magnitude' star, one of only 22 stars that are at magnitude 1 or brighter (and only four of these are close enough to the Ecliptic to be ever occulted by the Moon: Aldebaran, Antares, Spica and Regulus)
. For that reason the covering and uncovering of a star like this is a dramatic event, worth taking a few minutes with binoculars or a telescope to watch the proper motion of the Moon as a vastly more distant star's light is interrupted by the surface on the edge of the Moon and the light twinkles and vanishes from view for an hour.

On the west coast, the event takes place in broad daylight, but that should not make it any less impressive. Disappearance is at 2:21 pm and reappearance at about 3:40 pm. Check the Sky & Telescope article for more precise timings from around North America.

Astronomy Events in 2013

Every year is full of special moments in the sky as planets and stars and the Moon align to create noteworthy patterns and special views. 2013 will be marked by many special moments, so here's a quick overview of them.

Comets

Comet Hale-Bopp

The event of the year could be the fly-by of Comet Ison, currently en route for a November 28th close encounter with the Sun, potentially lighting up the night (and even daytime) sky. More information on Comet Ison here.

Asteroids

Mark your calendar for February 15-16, when Asteroid DA14 will pass within 10,000-20,000 miles of the surface of the Earth. This is a big asteroid, at 125 feet, and could cause considerable damage if it was to impact. Lucky for us, we will not have anything to worry about. More here from Earth Sky.

Eclipses

Only one eclipse will be of significance for the West Coast, on October 18th when the Moon will pass within the Earth's penumbral shadow. This partial eclipse will start before moonrise in California, but once the Moon rises, should be a nice sight.

Occultations

Every month as the Moon slips past planets and stars in the night sky, there are moments when a distant object is blocked out by the Moon, called an Occultation. This year there are several close encounters that should be quite fun to watch from the Bay Area. Depending where you are on Earth, you can see more or less of these events. A few noteworthy ones: January 21 and March 17 when the Moon passes very close to Jupiter; and February 28-March 1 and July 15-16 when the Moon passes very close to the bright star Spica.

Be sure to check out the Year In Space calendar for 2013 which has fascinating facts and is a wealth of astronomy information for every day and month of the year. And happy viewing this year!

Image courtesy Wikimedia Commons.

Close Encounter of the Pleiades and Moon

The Pleiades is one of the most beautiful star clusters in the sky. In Autumn it rises during the evening and its distinctive glow shines even for urban dwellers. The Pleiades, also known as M45 (from the Messier Catalog), is a collection of relatively young stars (only 100 million years old!) that shine with a blue color due to their hot temperature. The Pleiades are also known as the Seven Sisters and there is plenty of mythology describing each of the seven sisters. Despite the "Seven Sisters" mythology, most people see six stars when they look out at the Pleiades and describe the shape of the asterism as a small Little Dipper. Random fact: the Subaru car company logo is made up of six the stars, Subaru being the Japanese term for Pleiades.

This week on Tuesday evening the full moon passes very close to the Pleiades and in more southerly latitudes it actually occults (blocks out) several of the brightest stars in the cluster. For those of us in San Francisco, the evening of November 3rd should be especially interesting if you view the Moon through binoculars or a telescope. You will be able to notice how fast the Moon moves past the stars of the Pleiades. Although the very bright light of the full Moon will drown out nearly everything around it (including the blue nebulosity of the dust surrounding the Pleiades), all will be clear when you look closely with binoculars or a telescope.