Saturn Returns

Saturn has returned to the morning sky, rising higher each day shining in the east before sunrise. It is near the bright blue giant star Spica, in the constellation Virgo, and this week is graced by a visit from the Moon, creating a beautiful grouping on the morning of November 22nd.

Saturn and Spica are an interesting pair to compare. They are a contrast in color, with Spica shining a deep blue, and Saturn with a yellow-white tinge. Spica is 260 light years away, distant compared to many other bright stars in the evening sky, but being a giant star, it emits enough light to be the 15th brightest star in our night sky. Saturn is 80 light minutes away, a giant planet by Solar System standards, but due to its distance it never shines as bright as other Solar System objects such as Venus and Jupiter. But Saturn still captivates all who see it through a telescope because of its impressive ring system, making it a welcome target for any star gazer.

Image courtesy Sky & Telescope Magazine

Shimmering Early Morning Sky

As we approach the latest sunrise of the year (January 4th at 7:25 am in San Francisco), the morning sky remains dark enough to see stars until well after 6:00 am. That means that the early riser is rewarded with some lovely sights to close out 2010 and welcome 2011. Brilliant Venus dominates the sky each morning, shining bright in the South-East well before dawn. This week the waning Moon presents a changing landscape as it moves past Saturn, the bright star Spica (see diagram on the right), and then later in the week Venus and Mercury. Following the Solstice-Total-Lunar-Eclipse, the Moon is tracking downward on the Ecliptic, meaning that each Morning it is following the planets from high in the sky on a steep angle toward the horizon.

If you are not an early riser, don't despair. I'll have a post about the Winter skies soon. All you have to do is look up (especially if you are up at midnight on New Year's Eve and have clear skies). The Winter is a fantastic time to enjoy the stars.

Image courtesy of Sky and Telescope Magazine.

Brilliant Venus and Old Moon in the Dawn Sky

With sunrise at 7:00 in the morning, I find this time of year to be one in which I can do some early morning stargazing without having to change my morning routine. This week the waning Moon provides a lovely scene against the backdrop of brilliant Venus, bright Saturn and the bright star Spica. The illustration demonstrates what to expect in the eastern skies as the Moon shrinks each day on its way to the New Moon on December 5^th. If you are a morning person with an interest in astronomy, this will be an excellent week for you. Get out your binoculars for an especially riveting view of these heavenly bodies, and take in a few minutes of beauty about an hour before the sunrise.

Perspective of the Solar System

After weeks of foggy skies in San Francisco, the sky has started clearing, yielding spectacular sunsets and sky shows at Ocean Beach. I have been writing about (but not seeing much of) the amazing sight of the planets dancing across the evening sky. With the clear skies, the view was great, showcasing Venus and Mars very close together, with Saturn just to the lower right and the bright Zodiac start Spica (in Virgo) just to the upper left.

This configuration traces a curve in the sky and if you have a clear southern horizon you can "connect the dots" from this cluster of stars and planets to the south where bright Jupiter dominates the sky. Beyond that, the Moon is slicing across the lower southern sky, providing the observer with a nice visual of the Ecliptic, the line of the planets, Moon and Sun. This is a great way to visualize the path of the planets in the Solar System when you look out from our Earth-bound perspective.

Over the coming months, Mars and Saturn and eventually Venus fade, but the giant planet Jupiter will be dominating the Fall skies.

Star-and-Planet Drama

The evening sky over the next few weeks offers a study in the changes that take place in the sky along the path of the Moon and the path of the planets. This is exciting to watch and helps to unveil some of the intricacies of the Solar System, something you can see right from your own backyard. For quite a while now I have been particularly fond of sharing the path of the planets across the sky (the "Ecliptic") while conducting star parties and giving astronomy talks. I find that the ability to visualize this band across the sky is an important one for those who wish to have a basic understanding of the motion of the planets across the sky. And for several months the bright planets, a collection of bright stars, and the monthly sweep of the Moon across the sky have provided a perfect laboratory for learning. This month is no exception.

Shortly after sunset there is an excellent parade of planets and stars easily visible as the glare of dusk fades, starting with brilliant Venus in the west, and then in succession from west to south are Regulus, Mars, Saturn and Spica. These bright objects show the line of the Ecliptic.

At the end of this week there is a total solar eclipse (unfortunately not visible

from the San Francisco Bay Area). The eclipse comes at the middle of an Eclipse Season and as such, the Moon follows a descending path below the Ecliptic in the days that follow the eclipse, in particular from the 12th to the 17th of July. As it moves from day to day, it swoops just below the Ecliptic and makes a pleasant arc across the southern sky below Venus and Regulus, then Mars, then Saturn and then Spica.

And in addition, we are just coming into a period of time when fast-moving Venus has close encounters with the other planets and stars along the Ecliptic, starting with a close encounter of Regulus on the 9th of July. More drama to come in the next few weeks -- stay tuned!

High in the sky: The Big Dipper

The Big Dipper is one of the easiest groupings of stars in the sky to identify, and it serves as a guide to some of the more interesting stars in other parts of the sky. Late Spring evenings it is nearly overhead as seen from San Francisco, and its distinctive pattern provides an interesting exercise for understanding the motions of objects in the heavens.

The Big Dipper is not a constellation, by strict definition, because it is only the brightest 7 stars of the larger constellation Ursa Major. A named combination of stars within a constellation such as the Big Dipper is known as an "asterism." Because of its distinctive shape, the Big Dipper is a very well known asterism, one of several celestial groupings that lives up to its name (I put Leo, Scorpius, Cygnus and a few other constellations in this special class).

The Big Dipper points to the North Star (Polaris) if you follow the two stars at the side of the bowl of the dipper. This Wikipedia article illustrates this nicely. The line along the pointers from the Big Dipper to Polaris is helpful because this line is similar to an hour hand on a 24-hour clock. Every 24 hours the Big Dipper makes one counter-clockwise rotation around Polaris. From latitude 38 degrees north (approximately the latitude here in San Francisco) the Big Dipper is high in the sky when it is above Polaris (as it is now at sunset) and low in the sky when it is rotated half way around Polaris just above the horizon (as it will be in late Fall evenings).

The three stars in the handle of the Big Dipper form a curve, and if you think of this curve as an arc, you can follow it to a very bright star called Arcturus (in the constellation Bootes), and by continuing along this arc you end up at another bright star called Spica (in the constellation Virgo).

One more fun thing to find in the Big Dipper is the middle star of the handle, known as Mizar (see image above). This star has a very close companion, Alcor, next to it and if you want to test your eyesight, see if you can split the two without using binoculars or a telescope.

Enjoy learning about the Big Dipper in the pleasant weather of May and June. It's full of surprises and one of my favorite stops when sharing the sky with friends and guests at star parties.

Moon, Saturn, Corvus, Virgo and Venus

Now that the sky is remaining dark later and later each day, I am enjoying the early morning interplay of Solar System and stellar objects. This week provides a series of lunar alignments with Saturn, the constellation Corvus, the bright star Spica in Virgo, and finally Venus -- if you have an exceptionally clear, low eastern horizon. Sunrise in San Francisco is from 6:45 to 6:50 am this week.