Gorgeous Dawn Sky

Sometimes the stars do in fact align and all is well. OK, perhaps not the stars but the planets, and suddenly they shine in the sky as the clouds and rain in San Francisco have miraculously disappeared just in time. The morning of Friday February 1st is one of those special moments when the brightest objects in the sky line up and make for great viewing. As Venus graces the morning skyline, it is being joined by Jupiter which is rising each morning higher out of the morning glare of sunrise. They pass very near to each other on the morning of the 1st and are about a half degree apart - that's about one full moon's width. But the moon is not far off, a crescent just up and to the right next to the bright star Antares in Scorpio.

The next few weeks will offer the chance to see the change in the lineup, as Jupiter continues to climb each day in the morning sky while Venus stays low on the horizon. That is because Jupiter, being considerably further away from the earth, moves at more the same pace across the sky as the sun, whereas Venus, being much closer, actually is speeding around the Sun and stays lower on the horizon.

Moon in Action / Being on KFOG

This week the waxing moon journeys across Taurus and Gemini. As it does, it encounters the Pleiades, the small but distinctive cluster of stars in Taurus also known as "the Seven Sisters." On the evening of January 17th, the moon will graze through this region of the sky in what is called an "occultation" of the Pleiades. Occultations are special times when a celestial object is "blocked" from our point of view by another object. The most common are occultations of stars and planets by the moon. When this is being caused by the moon, it affords anyone with binoculars or a telescope to easily observe the motion of the moon against the background stars as the moon makes its monthly journey around the earth. On the evening of January 17th as the moon variously covers and uncovers stars in the Pleiades, you will be able to sense that motion. Over the course of approximately three hours the moon will move across the Pleiades.

Two days later, the nearly full moon will pass very close to Mars but will not occult the planet from our vantage point in San Francisco. Observers much further north (in Canada) will in fact see the moon completely cover Mars. Because Mars is bright and fairly close to earth right now, the sight of it so close to the full moon will be quite beautiful. Take a few moments on the evening of January 19th to enjoy this spectacle. I observed a similar lineup of moon and Mars in December during the previous full moon two days before Christmas.

Earlier this month I was a guest on the KFOG radio morning show (104.5 FM in San Francisco). KFOG features the best morning show program in the San Francisco Bay Area (in my humble opinion) because the DJ and his crew talk about relevant subjects and current news items in an intelligent way. I thought it would be interesting for the KFOG listeners, affectionately known as Fogheads, to hear about astronomy and I asked to be a guest on the program. Morning show producer Greg McQuaid welcomed me to join and on January 8th I was a guest. The program went well and the Fogheads asked interesting questions. I am invited to return to the morning show in March and will post an update to the blog when the date is confirmed.

There were many more questions from Fogheads that we did not get to answer during the show, so I will post them to this blog from time to time.

KFOG broadcast: January 8, 2008

Astronomy Resources

The web is filled with excellent astronomy resources. Here are some of the sites I frequent for different kinds of information.

Visit daily: Astronomy Picture of the Day

Photos and Images: NASA has a wealth of photos from all of its missions.

Eclipses: the authority on all things related to eclipses: Fred Espenak's NASA site

Good for listening: StarDate is a quick daily dose of very general astronomy topics. Astronomy Cast is an excellent weekly podcast for those looking for deeper insights.

General Resources: Sky and Telescope Magazine or Astronomy Magazine are very good portals covering many aspects of astronomy for the amateur and hobbyist. Spaceweather.com has very useful up-to-date information and news about the goings-on in space.

Sun and Sky Conditions: The Clear Sky Clock provides a wealth of detail on sky conditions with details on transparency, darkness, seeing, and so on. The US Naval Observatory provides exact sunrise and sunset times anywhere on the globe.

Clubs: San Francisco Amateur Astronomers have a range of activities and resources if you want to get more involved in astronomy.

Winter Darkness / Geminids Meteor Shower

The deepening darkness of winter has arrived and with it the beautiful winter skies. The earliest sunset has already passed, but the longest night is yet to come on Friday December 20th when we will experience over 14 hours of twilight and darkness from sunset to sunrise. This date is known as the Winter Solstice and it marks the day when the sun appears to be at its lowest point in the sky (at noon) compared to every other day of the year. From our latitude in San Francisco, this means that the sun will only appear approximately 30 degrees above the southern horizon at noon on December 20th - very low indeed!

December also brings the annual Geminid Meteor Shower. If you spend enough time looking up at the sky on any night of the year you will likely see a few meteors streak across the sky. However, a meteor shower is a special time in which a much higher number of meteors are visible. December 13-15 is a time when the Earth passes through a part of the Solar System which contains a particularly high concentration of dust and particles which enter the atmosphere and burn up, creating the beautiful "shooting stars" that we have come to know. This year the Geminid Meteor Shower comes at a time when moonlight will not interfere with seeing and the weather prospects are good (at least as of the time of this writing). The meteor shower is called the Gemenids because the meteors in the shower all seem to emanate from the same part of the sky in the constellation Gemini.

To see the Geminids, you need to look east in the evening after 9:00 pm, or straight up around midnight, or due west in the pre-dawn skies in the morning. The twin stars of Gemini (Castor and Pollux) are a bright pair and brilliant orange Mars is nearby. These stars and planet mark the spot where the meteors will appear to come from. It's rumored that the early morning hours of Friday 14th should bring some of the finest viewing to us on the west coast. Bundle up in a very warm jacket and hat and take a look. There's no need for a telescope or binoculars. You should see at least a few meteors even in the bright city skies of the Bay Area.

Comet Holmes

Over the last three weeks a minor and otherwise dim comet has suddenly flared and become bright. Comet Holmes has been sighted many times since its discovery in 1892 but it has been historically a faint object barely worthy of note when it passed near earth. However, on October 24th this year it brightened suddenly by over 1 million times and became as bright as the neighboring stars in the area of the sky where we can see it now. Comet Holmes is in the constellation Perseus in the evening. This comet is not nearly as distinctive as previous comets such as Hale-Bopp but it has developed a unique shape compared to other comets, something more of a ball of light surrounding the core of the comet. One reason for this is that we are viewing the comet "straight on" from our perspective on earth and not "edge on", like looking at a train approaching from the front where all you see is a headlight and the front of the train, not the side view of the string of train cars from front to back. Because we see the tail of Comet Holmes from the front rather than the side, we see a cloud of glowing dust surrounding the core. In binoculars or a telescope it looks quite impressive. I had a good look at it a few days ago and have been watching it since then. It is subtle with the naked eye, but very distinctive through binoculars or a telescope.

There are excellent accounts of Comet Holmes on many websites. Start at www.skyandtelescope.com and you will find photos, charts and links with the latest information about the comet, since it is such a dynamic object. Astronomers are at a loss to explain exactly what happened to cause Comet Holmes to suddenly flare up. There is no way to know when it might fade from view, but by most accounts it should stay bright and visible for the days ahead.

Waxing Moon / International Space Station

Last weekend I was at Ocean Beach as the sun set. Minutes after sunset I spotted a thin crescent moon hovering low on the western horizon. I find the very young crescent moon a beautiful thing in part because of its rarity. We are all quite acquainted with the "normal" appearance of the night sky -- lots of stars! But I find myself drawn to moments when something rare or unique happens in the sky such as the times I have seen a total solar eclipse or a close alignment of planets with a bright star. When a very thin crescent moon emerges in the sunset or sunrise sky, it is quite often a stunning sight because it is so low on the horizon and therefore looks large against the horizon, and because the "earthshine" on the dark portion of the moon gives it a ghostly appearance.

This week the moon is waxing and moving across familiar territory along the ecliptic past Jupiter and through Sagittarius. The moon is, of course, a satellite of the earth. That is to say, it is held in an orbit by earth's gravity and is close enough to the earth that when it is visible it dominates the night sky. There are, of course, many other satellites orbiting earth. These are man-made satellites and they too can be exciting to see in part due to their rarity and in part due to their unusual motion or brightness. The most distinctive satellite we can see on a regular basis is the International Space Station, also known as ISS. It orbits the earth every 90 minutes and is approximately 200 miles above the earth. It makes a fairly constant trip around the earth but each time it does so, the earth rotates part of the way through the day. ISS is quite large (about the size of a football field) and reflects sunlight very well, so when it passes directly overhead just after sunset or just before sunrise (when our skies are darkened but ISS is still in sunlight), it shines very brightly and moves quickly across the sky, much faster than airplanes.

If you want to get a look at this, you need clear skies, attentive eyes, and an accurate wristwatch. NASA maintains a website with all the details when it will appear over which parts of the United States. The website address is http://www.jsc.nasa.gov/sightings/index.html (or just type "ISS sighting" into your search engine). The next opportunity to see ISS from the Bay Area is on Friday Oct 19th at 7:29 pm and Saturday Oct 20th at 7:52 pm. In both cases look to the north-west. The ISS will take about 2 minutes from the time it appears above the horizon until it travels into the shadow of the earth and goes dark.

Good luck and happy viewing.

Planet Lineup

As the days grow shorter and the nights longer and the Fall weather brings clearer skies to San Francisco, I find myself with more opportunities to gaze into the heavens. While some may groan that it is dark when they wake up in the morning, I think it is a perfect time for a 60-second peek into the sky. There is much going on so take note and enjoy the fact that Daylight Savings Time lasts an extra week this year (it ends on November 4th).

After the Moon, the five nearest planets are the brightest objects in the night sky. Right now we have clear views of four of them (Mercury is too close to the setting Sun to be seen at this time). Jupiter is an evening object low in the southwest after sunset. By the end of October it will be setting shortly after the Sun. Mars is a nightime object rising due east and moving directly overhead by morning. The diagram illustrates its location this week drifting through Gemini with a close encounter with one of the two bright "twin" stars of Gemini. Venus and Saturn are both morning objects. Given that sunrise is just after 7:00 am this week, the two planets are quite bright in the pre-dawn sky around 6:00 or earlier. Next week there are some beautiful combinations of planets, stars and Moon that you will want to see. The grouping on Sunday morning October 7th should be very striking.