KFOG Broadcast - October 25, 2011

I was a guest on a live broadcast with the KFOG Morning Show today, talking about Jupiter, things to see in the Autumn night sky, the Pleiades, meteor showers, and the Bay Area Science Festival. The DJs on the Morning Show are an interesting group, and the conversation is always lively. Click here to listen.

The Moon amid planets and star clusters

The morning sky this week will be rich with easy-to-spot celestial objects in the hour before sunrise. Find a good view toward the eastern horizon and use binoculars to enhance the view of Venus, Mars, the waning crescent Moon and two of the finest star clusters in the sky, the Pleiades and Hyades. I am looking forward to it!

The Moon and two Star Clusters: Pleiades and Hyades

The Moon graces the last vestiges of the winter sky this week, as the waxing Moon splits two of the prettiest star clusters, the Pleiades and the Hyades. This will be an exciting sight for stargazers, one that will look particularly magical through binoculars. So mark your calendar for Thursday April 7th and watch the show unfold all week long.

When the Moon emerges from the New phase and starts its 29 1/2 day journey around the Earth, the first few days are always a treat, because the waxing crescent offers so much to see through a telescope or binoculars, and even without optical aid, the sight of the thinly-lit Moon and the glow of Earthshine always catch your eye.

On Thursday, the Moon moves past the Pleiades star cluster, one of the best known clusters in the sky because the stars in it are fairly bright and concentrated into a small space, creating a kind of glow in the sky. Around the bright star Aldeberan in Taurus is the open cluster called the Hyades. These stars are also a close grouping in the sky, but not as tightly arranged, so you don't get the same kind of glow. However, through binoculars this cluster offers much to see.

Use the graphic (above) to help you orient yourself this week. You will want an observing location with a clear western horizon, away from streetlights or other distractions, and good weather. If you get all these conditions just right, you have no excuse for missing this gem of a celestial lineup. And if you live in San Francisco, come join me at the Cal Academy for a personal tour :-)

Waning Moon, Morning Darkness

Each month the Moon makes a 29 1/2 day journey around the Earth, bringing different faces of the Moon to light, making beautiful patterns with the surrounding stars and planets, and shining light into the evening, midnight or morning skies. Right now, the Moon is waning, getting smaller each night as it passes through gibbous phases while moving from Full Moon to Last Quarter, lining up with bright celestial objects such as the Pleiades and Taurus. During the gibbous phases, the orientation of the Moon is quite different from what we normally expect in the evening skies.

The illustration shows the changing orientation of the Moon just after sunset in the waxing phases, as the Moon grows from New to Full. This view is for Northern Hemisphere viewers. But after the Full Moon, the orientation reverses and is best measured in the sunrise sky. So the view you can see right now is of a Moon curved not toward the east as normally seen in the evening sky, but rather curved toward the west in the morning sky. It's refreshing to see this time of year while it is so dark in the morning, and it provides a chance to see things in a different light. Eye-opening.

Image courtesy of University of Virginia.

A Beacon in the Twilight

As the days grow longer and the last vestiges of twilight linger later in the evening, look to the West this week for some very beautiful planetary/celestial lineups. The week features fast-moving Venus passing very near to some of the most spectacular star clusters in the night sky, the Pleiades and the Hyades.

When you look into the twilight sky, the brightest objects shine majestically against the bright blue background. That is the case for Venus this week, as it is for the young crescent Moon each month when it shines low in the West in the first few days after new Moon. However, in order to see the star clusters near Venus, you will need to use binoculars. The stars are there to see, but the bright twilight makes them all but invisible to the naked eye. It's worth the time to get out and see this spectacle. Sunset in San Francisco is just before 8:00 pm, and the sky will be dark enough about 45 minutes to an hour after that.

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.

Moon, Pleiades, Mars and Venus

The next few mornings provide a great chance to see close alignments of planets, the Moon and the easy-to-spot, beautiful star cluster known as the Pleiades. Click on the illustration (at the right) for a detailed view of the spectacle in the eastern pre-dawn sky, especially the changing location of the Moon each morning as it wanes from last quarter to a thin crescent.