29 April 2012

Planet and Star Pairs Line the Sky

This April, as the weather has improved and I've been conducting star parties, I've found myself focusing on some striking pairs of planets and stars that punctuate the night sky this spring. The pairs are all located in the Zodiac, the band across the sky that houses the well-known 12 signs, and also the planets and the Moon. The pairs of planets and stars are easy to find, and when you find them, you get a big picture of the band of the Zodiac, with the planets in our Solar System superimposed upon that band.

Shortly after sunset, it is quite easy to find Mars, shining a bright orange color almost directly overhead, and just next to it, the bright blue-white star Regulus in the constellation Leo. Starting from this point and looking North-West toward the point of sunset, you will encounter the twin stars Castor and Pollux, the two brightest stars in the constellation Gemini. And starting again at Mars, if you look toward the South-East, you will find the next pair along the Zodiac, the planet Saturn and the bright star Spica in the constellation Virgo.

If you trace a line from Saturn through Mars, and then toward the North-West through Gemini and to the brilliant planet Venus, you will be tracing out the path of the planets along the night sky, through the band of constellations we call the Zodiac, and along a line in space called the Ecliptic. It's a great way to get acquainted with the heart of our night sky, and this week you can watch the Moon gliding through the same space, as it makes its 29 1/2 day journey around our home planet.

Images courtesy of Sky & Telescope.

21 April 2012

Lyrid Meteor Shower 2012

Meteor Showers occur throughout the year, and a bright Moon can wash out the view, so when we have ideal conditions for a shower, it's a good idea to take a few minutes and try to see it. Tonight, the Lyrid Meteor Shower reaches its peak, and we will have no moonlight to interfere.

The Lyrids are named after the tiny constellation Lyra, and although it is a small constellation it features the fifth-brightest star in the night sky, Vega. The constellation is the 'radiant' of the meteor shower, meaning that the meteors appear to emanate from this area of the night sky. Lyra rises before midnight and as it climbs higher in the sky during the late night into the early morning, more and more Lyrids will be visible.

As is the case with all meteor showers, you want to dress warmly, find a relaxing spot in a dark area (mountains, backyard, beach), be sure you have a wide view to the night sky, and have some patience. Observing is good with a friend or two, since you might see one meteor in a part of the sky where your friend is not looking, or vice versa.

I wish you dark skies and a pleasant night observing.

Image courtesy of Astronomy.com.

17 April 2012

Get Involved: Mt. Tam Lectures, Globe at Night

Part of the joy of astronomy is to gaze up in the heavens and enjoy the spectacle of looking into the vastness of space. And for many, another part of the joy of astronomy is learning about space science. I like to highlight opportunities in the San Francisco Bay Area for both of these perspectives, and one of my favorite places to both learn about space and also enjoy gazing into the heavens is on Mt. Tamalpais in Marin County, where the public is invited to take part in monthly lectures by leading astronomers, and immediately afterwards, enjoy the heavens through telescopes provided by our local astronomy club, the San Francisco Amateur Astronomers (SFAA). The 2012 season of lectures kicks off this Saturday April 21st with Dr. Alex Filippenko of UC Berkeley, talking about the upcoming Ring of Fire Solar Eclipse in May, and the Transit of Venus in June. I'll be there giving a night sky tour following Dr. Filippenko's lecture, and the weather is cooperating so a good evening is in store. More information here.

The annual dark sky awareness event called Globe At Night comes to a close this week. The public around the world is invited to find one of three bright constellations and estimate how many of the stars in the constellation are visible from your location. By submitting your results online, you contribute to a world-wide database of sighting, helping to build a global map of light pollution and to raise awareness of this issue.

No matter where you are, you can find astronomy events on the Night Sky Network. Check out this great resource and Get Involved today!

08 April 2012

Venus in Motion

The brilliant planet Venus shines each evening in the west, leaving most who see it saying "that's not a planet, that's an airplane, isn't it?" For the next two months, its orbit around the Sun is bringing it closer to Earth each day, en route for a rare and exciting Transit on June 5th (for Western Hemisphere viewers).

Because Venus is located nearer to the Sun than Earth, as it moves in its orbit around the Sun it only is visible in the evening sky after sunset, or in the morning sky before sunrise. Right now, as we observe Venus in the evening sky, we can watch it speed around the Solar System by comparing its position to the backdrop of stars in the distance. Last week, Venus passed near the Pleiades star cluster, and for the next few weeks it will glide away from the Pleiades, as the star cluster moves quickly into the glare of the sunset sky while Venus hangs high in the west. At the end of April, Venus is at its greatest brilliance (brightest) for the year. Nakedeyeplanets.com has excellent charts showing the changing position of Venus in the heavens.

Soon after greatest brilliance, Venus will reverse its course into retrograde motion and begin a slow fade into the glare of the sunset sky as it rapidly closes the gap for its nearest approach to Earth and the June 5th Transit. I'll have more on the Transit of Venus in another article. For now, enjoy the bright shiny object in the west as it holds 'center stage' for all of us.

Image courtesy of Sky & Telescope Magazine.

06 April 2012

Vernal Equinox, Full Moon, Passover and Easter

As Spring arrives, so do the religious festivals of Passover and Easter. These two festivals change date each year, happening sometime in March or April. These festivals are tied to the phase of the Moon and the Vernal Equinox (the first day of Spring), and hence they change date each year. Tonight's Full Moon is the event that ushers in these festivals. How does the timing of these events work?

The Vernal Equinox is the first day of Spring, the day when the Earth's tilt is aligned to its orbit around the Sun, so the poles of the Earth tilt neither toward the Sun or away from the Sun. On this day (and again in the Fall at the Autumnal Equinox), every place on Earth experiences the same number of hours of Sun above the horizon and Sun below the horizon, hence 'equinox' for equal lengths of day and night.

The first Full Moon following the Vernal Equinox marks the start of the religious festivals in Judaism and Christianity, with Passover taking place on the day of the Full Moon (today), and Easter on the first Sunday following the Full Moon (this Sunday April 8th).

Tonight's Full Moon will be very close to the bright blue star Spica, the brightest star in Virgo, and just to the left of Spica you will have a nice view of the planet Saturn. Enjoy the view!

Image courtesy of Sky & Telescope Magazine.