KFOG Broadcast: November 25th, 2008

Conjunction of Venus and Jupiter

Venus and Jupiter will have a conjunction at the beginning of the month of December. What is a conjunction? There are many uses of the term in astronomy, and here we use it to describe when two planets are very near to each other because they are on the same line of "longitude." I put the word longitude in quotes because in astronomy, we use a coordinate system similar to latitude and longitude, but the proper names are declination and right ascension. Therefore, when two planets have the same right ascension, we call that a conjunction.

The sketch (made by my daughter) depicts the sky as it will appear shortly after sunset on November 30th just as Jupiter and Venus are moving toward their closest approach. The scene will be made all the more beautiful by a young crescent moon just below the two planets. The next night, December 1st, the Moon will have moved just to the left and above the two planets. Both nights will be perfect for telescopic viewing, as the young Moon with its cratered surface (usually accompanied by earthshine) is always a beautiful sight, and you can see Venus at gibbous phase and Jupiter with its four bright moons. As mentioned in a previous post, these three objects with their special traits are three of Galileo's most famous discoveries with his telescope in the early seventeenth century.

Don't wait: Use your telescope now

This month offers a great opportunity to dig out that old telescope that you've rarely used and put it to work. Jupiter and Venus are putting on a show that will be of interest to anyone who has ever marveled at the heavens. These two planets are moving closer and closer and at the end of November will form a very compact grouping with the crescent Moon. What will you see?

Venus is brightening as it gradually moves closer to Earth in its orbit. Because it is nearer to the Sun than the Earth, it never climbs too high in the sky. For the rest of 2008 it is a brilliant evening "star", dominating the western horizon just after sunset. Jupiter, on the other hand, is much more distant from the Sun than the Earth and therefore over a year can be seen in all parts of the sky, moving gradually against the backdrop of stars but not nearly as quickly (from our Earth-bound perspective) as Venus. Jupiter has spent 2008 in the constellation Sagittarius and the diagram shows its present location, moving east of Sagittarius toward Capricorn.

Each evening for the next few weeks you will be able to see Jupiter and the background stars of Sagittarius gently drift toward the Sun while Venus holds its own. The combined effect is that Jupiter will move closer and closer to Venus. It is an experiment that requires nothing more than taking a moment each evening (or every couple days) to look west after sunset and note the relative position of these two bright objects. They are much brighter than anything else in the sky so you should not have any problem finding them. On November 17th Venus makes a very close encounter with one of the brighter stars in Sagittarius.

The evenings of November 30th and December 1st are particularly noteworthy as the young crescent Moon makes a close "fly-by" of the two planets, something that should be dazzling to see with a telescope or binoculars. Jupiter, of course, is impressive with its four bright moons, and Venus is always fascinating because it goes through phases just like our own Moon. By end of month, Venus will be a waning gibbous phase as it moves closer to Earth and slowly becomes a crescent over the next several weeks. Happy viewing!

Dark October Mornings

Last year the US Congress made a change in daylight savings time. Rather than end in October it now carries into November. The effect of this is that mornings are dark in October, making it hard to get up and get going. On the other hand, it makes it much easier to see the morning sky and in the coming days it's going to be noteworthy.

Sunrise is happening this week at 7:30 which means that up until 6:45 or so, the sky is dark enough to see stars and planets. The diagram shows where to look for the Moon, Saturn and even Mercury. In the Fall, the path of the planets and Moon (the ecliptic) is in a very steep line from the point of sunrise into the eastern sky. Hence Mercury will be visible just above the point where the Sun will be rising, and Saturn and the Moon in increasing distances above and to the south of Mercury.

I love to see the very old Moon in the last days of its cycle. The ever thinning crescent reflects more and more "earthshine" and glows like a jewel in the morning sky. As October comes to a close, the waning Moon on the 24th, 25th, 26th and 27th should be a striking sight as the sky begins to glow with the dawn.

Galileo discoveries redux

Nearly 400 years ago Galileo pointed a crude telescope toward the heavens and documented three remarkable things in the sky, discoveries that dramatically affected the understanding of the universe at that stage in history. With his telescope Galileo was able to see that the Moon was not a perfect circle, that Venus had phases, and that Jupiter had satellites of its own. Each of these posed a threat to the current body of knowledge of that era - Jupiter's moons and Venus' phases challenged the geocentric view of the universe and the non-perfect Moon challenged the Aristotelian theory of perfectly circular shapes in the universe.

With a simple telescope or even binoculars you can recreate some of these discoveries in the coming weeks and months. I'll write more about Venus in a future post. In October and November the phase of Venus will gradually transition from gibbous to half and later in the year to a crescent. The Moon is easy enough to study and is a marvel to view in any telescope or binoculars with the spectacular rocky edge of the surface always intriguing.

However, for the coming months Jupiter is the dominant "star" in the evening sky. Jupiter calls out for investigation because of the interesting texture of its surface and because of the changing position of its four largest moons. Called the Galilean satellites, these moons are visible to us even in low magnification and are interesting to observe because they change location so quickly -- even within the course of a few hours. They regularly pass through the shadow of Jupiter, yielding eclipses on a frequent basis.

From the nearest to the furthest moon, the names of the four satellites are Io, Europa, Ganymede and Callisto. Io is so close to Jupiter that it orbits the giant planet in less than two Earth days. Europa takes exactly twice as long and Ganymede twice as long again. Every few hours the overall pattern of these four moons is changed sufficiently to see new moons emerge from behind Jupiter, others disappear, and the overall pattern spread apart and then contract into a group.

Sky and Telescope Magazine has an excellent article on the moons and a very helpful pop-up screen that you can view in your web browser. It shows you the relative position of the moons of Jupiter at any time and can make a star gazing evening into a treasure hunt that will give you the feeling of discovery that will rival that of Galileo. So take the time to look to the south for the brightest object you can see (about halfway up the horizon above due south after sunset) and try it for yourself.

KFOG Broadcast: September 24th, 2008

California Academy of Sciences and Morrison Planetarium

The California Academy of Sciences reopens in a beautiful new building on Saturday September 27th. This long-awaited opening will be a major event for San Francisco. The new building is an architectural achievement and a model of sustainability. I am particularly enthusiastic about the new Morrison Planetarium, one of the signature pieces of the CAS. I was able to preview it today in a press-only tour and I was very impressed.

There are several elements of a planetarium that make it distinctive. The newest planetariums (such as Morrison Planetarium here in San Francisco and Griffith Park Observatory in Los Angeles) feature state-of-the art projection systems that blend traditional star projections with high-resolution digital images, enabling a richer and more engaging presentation of astronomy. Morrison also features a tilted dome rather than an overhead dome, so you can fully experience the immersion of the screen without having to tilt your head back in your chair. The dome is tipped at approximately 30 degrees so you are viewing the show more like a movie theater than planetarium. The narration and sound are very good and the total effect is to truly transport you out of the day-to-day and take you untethered into space. It works!

The highlight of my visit today was the show in the Morrison Planetarium theater. The inaugural show is called Fragile Planet and it provides, through a series of stunning images - the Earth, the Solar System, nearby stars with planets, the Milky Way and other galaxies - a snapshot of the extremely delicate balance of conditions necessary to create life as we know it. What I found most interesting was the notion of the "habitable zone" that exists at just the right distance from the Sun (or around any star for that matter), the space in which planets can experience the temperature conditions as we do on Earth, conditions which support liquid water. During Fragile Planet you are transported to Gliese 581 d, an extrasolar planet orbiting a star in Libra. Gliese 581 d is a planet that due to its location near and in the habitable zone of its star, might support life.

Wired Magazine has a good video clip on the new planetarium featuring Ryan Wyatt, Director of Morrison Planetarium and Science Visualization.

All in all, the California Academy of Sciences is a superb place to learn about a broad range of sciences, housed in a magnificent facility that will be a treasure for San Francisco for generations to come.

Biodynamic Astronomy Lecture and Star Party on September 6th

Over the past many years I've made several visits to a biodynamic farm called Live Power Farm. The children at San Francisco Waldorf School have a tradition of going there to learn about farming and as a parent on several of these trips I have had a chance to get to know the farmers at Live Power Farm and the approach they embrace, biodynamic farming. It relates to astronomy because it is a very natural and harmonious approach to working with soil, seed, sun and the cycles of nature. As a member of the Live Power CSA, I share in the bounty of the farm and enjoy the amazing food they produce every week.

On my visits to Live Power Farm I learned that the farmers are very cognizant of the lunar cycles and planetary positions with respect to the Sun and Earth. They use a well known guidebook by Maria Thun and biodynamic calendars to guide their work on the farm and I was fascinated to see how farmers worldwide have come to understand cycles in the heavens and use these cycles in their farming. I spent many nights at Live Power Farm talking with the farmers and apprentices about the celestial mechanics of the sky to deepen their appreciation of how these cycles actually come to be.

Saturday September 6th I will be hosting a lecture with Stephen Decater of Live Power Farm. I will share my insights on how to understand the motions of the Moon and planets and how we see their motions from our vantage point here on Earth. Stephen will share his interpretations of these motions and how he works with the cycles in the heavens to guide his work on the farm. Please join us at 7:00 pm for the lecture and 8:30 for star gazing and telescope viewing of the skies. This event takes place at the Marin Waldorf School and is being sponsored by Live Power Farm, San Francisco Waldorf and Marin Waldorf Schools. I hope to see you there.