Perseid Meteor Shower 2012

The big meteor shower of the year, the Perseids, peaks this weekend and promises a good show for all who can find dark skies and have the patience to enjoy them. The Moon will generally cooperate with viewers since it will only interfere very late into the night, and even then will only cast a small amount of glare on an otherwise exciting event.

The Perseids are a regular meteor shower that peak over one or two days each August as the Earth plunges into a stream of particles from the comet Swift-Tuttle. As we impact these particles at tens of thousands of miles per hour, we enjoy a spectacle of shooting stars darting across our night sky, sometimes one per minute, sometimes less or even sometimes more. Your ability to see more meteors depends upon three things: (a) dark sky, (b) dark adaptation, and (c) lateness of the night. The darker the sky, the fainter the meteors you will see. The longer you are in your dark environment, the better your eyes will adapt to the dark and enable you to see fainter objects. And finally, later in the night the Earth is intercepting more and more meteors, right up until the first light of dawn.

The shower peaks on Saturday night August 11th and Sunday night August 12th. Your best bet in the San Francisco Bay Area will be locations away from city lights with good views across the entire sky, but in particular with a good eastern horizon.

EarthSky has a helpful article about the Perseids. From EarthSky: "They radiate from a point in the constellation Perseus the Hero. You don’t need to know Perseus to watch the shower because the meteors appear in all parts of the sky. The Perseids are considered by many people to be the year’s best shower, and often peak at 50 or more meteors per hour in a dark sky."

Watching the Solar System in Action

As we move into August, we can witness the gradual change in the night sky from one evening to the next as planets near and far align and move among the backdrop of stars in the heavens. In particular, Mars is moving quickly in its path around the Sun, and as it does so in early August, it will move just between a pair of bright objects, the star Spica and the planet Saturn. The diagram illustrates the position at the end of July, and the spacing between Mars and the pair will close as we move into August. This is a superb opportunity to witness the motions in our Solar System as we on Earth move around the Sun (making the trio of planets and stars appear lower in the sky each night), and Mars moves eastward with respect to Saturn.

Image courtesy of Sky & Telescope.

Get Involved: Star Parties and Astronomy Lectures

Wherever you live, there are always good astronomy events happening in your town. The Night Sky Network is the first resource you should check for the latest events anywhere in the world.

Every weekend, the observatories and science museums in the San Francisco Bay Area open up for public viewing, such as the Chabot Space and Science Center and Foothill College Observatory.

Lecture: In the San Francisco area, I always encourage people to visit the monthly meetings of my astronomy club, the San Francisco Amateur Astronomers (SFAA). Every month we have some of the best astronomy speakers present their latest ideas, and this month is no exception, with a science history talk presented by John Dillon entitle "Galileo Reconsidered" on Wednesday July 18th. Click here for more details.

Lecture & Star Party: Once a month at the top of Mt. Tamalpais in Marin County, high above the thick fog of a San Francisco summer's night, you can find a wonderful Saturday night event featuring a lecture in the Mountain Theater, and stargazing with the SFAA afterwards. This Saturday, July 21st, features Dr. David J. Des Marais from the NASA-Ames Research Center. The tile of his talk is “Astrobiology Investigates Life in the Context of Space.” Click here for more details.

I hope you can join us for an upcoming event.

Beauty in the Dawn Skies

Dawn Sky: Moon and Planet

The next few days feature a fine lineup of Moon and Planets in the dawn sky. As the Earth swings around in its most distant stretch of its orbit (we were at aphelion last week), the constellation Taurus gradually becomes visible in the morning sky, with its bright star Aldebaran rising just ahead of the Sun. Looking in that direction of the sky, the giant planet Jupiter is present near the "V" of Taurus, as well as the planet Venus, fresh off of the Transit and now heading westward from our point of view against the backdrop of stars. These bright objects are visited by the crescent Moon for a few days this weekend, so take a moment and look east if you are up before the sunrise.

Image courtesy of Sky & Telescope.

Planets moving along the Ecliptic

Position of Mars in early July

Looking into the evening sky, two planets are visible in the south-west and are heading toward a 'conjunction' in August when they will line up with a bright star. Mars is the faster-moving of the two, changing position each night against the backdrop of stars as it travels around the Sun roughly every two Earth years. In a previous blog post, I noted the position of Mars in the constellation Leo, where it emerged from retrograde motion in April and has been moving steadily east each night since then. Last week I showed its position in another blog post highlighting how far it had traveled from Leo, now moving into Virgo. And in one month, during the middle of August, Mars will finally arrive between Saturn and its stellar neighbor Spica, creating a wonderful sight.

But these milestones are just the highlights that punctuate the journey. In fact, looking out each night at Mars is quite wonderful, seeing it shifting its position along the ecliptic, illuminating the pathway of the planets, Sun and Moon across the zodiac band in our night sky. I point this out to guests at the California Academy of Sciences when I give talks there during NightLife each Thursday, and this is one of the most inspiring things people discover as they look up in the sky with me -- that they can actually see the motion of Solar System objects by just looking up and paying attention to what they see.

If you want to learn more about Mars, and the upcoming landing of the Mars rover Curiosity, check out the Night Sky Network page called "We're Mad About Mars!"

Image courtesy of SkySafari.

Summer looking South-West

Now that the summer constellations have fully emerged, I am enjoying the sparkling views at night as I look from one horizon to the next. Last week I focused on the eastern horizon while conducting a Star Party at Mt. Tam, but the next night I was in my yard viewing the south-western sky, and was so amazed by the view.

South-West Sky in June

In early summer, Leo is diving down toward the western horizon, with the familiar lion shape almost face-down. Mars has been steadily moving eastward across the ecliptic, from its springtime position near Regulus in Leo, now more than half-way to Spica in Virgo and a lineup with Saturn in August.

Bright Spica and Regulus, with the planets Saturn and Mars between them, create a beautiful string of bright shiny objects low along the south-west, and from my backyard in San Francisco, the view to the south-west is fairly dark, so everything was just right in the sky as I gazed in that direction. To the left (east) Scorpius is coming up into view and later in the evening dominates the southern horizon -- but I'll have more on that in a future post. And directly above, you can enjoy the dazzling star Arcturus and the lovely Northern Crown just nearby (Corona Borealis - - read more here). Just below Virgo is the easy-to-spot constellation Corvus. The sky is full of wonder, and summer weather makes it more fun and relaxing to see the sky. Wherever travels take you this summer, dedicate an evening to star gazing and reward your senses with the beauty of the heavens.

Image courtesy of SkySafari.

Slender Moon

It’s been a full lunar cycle since the Annular Eclipse of the Sun in May, and now the Moon once again graces the evening sky with its slender disk, slicing below the ecliptic in a line just south (left) of the planet Mercury and the star Regulus. I enjoy spotting the very young Moon such as we will see on Thursday 21^st, not just in the glow of dusk alongside the emerging planets and stars, but also in the mid-day sky where it is high above, near the summer Sun. Finding the young disk of the Moon in the daytime sky takes patience and focus, but with a well-placed location next to a building or tree that solidly blocks out the bright Sun, the thin Moon is a treat to find. 

Image courtesy of Sky & Telescope.

Transit of Venus on June 5

It's showtime! 8 years ago, the planet Venus passed in front of the Sun, and now it's time for the second of the pair of transits before a 105-year break. The view from San Francisco and the west coast of the US will be very fine, with the event visible in the western sky starting around 3:00 pm until sunset.

I spoke with Ben Trefny of KALW radio about the Transit of Venus. You can listen to it here. 

Much is being written about this transit. It fits into the category of 'unique and rare astronomical events' that are special and worthwhile to see if only for the rarity of the event. Venus makes two transits of the Sun every 100+ years, and the last one of this pair (8 years ago) was not visible in San Francisco, so Tuesday June 5th is a special opportunity to see this event. The website transitofvenus.org is an outstanding resource, as is Sky & Telescope with their historical writeup of past transits. Safe viewing tips can be found here on EarthSky.

I am going to take part at an event co-sponsored by the San Francisco Amateur Astronomers and NASA Ames in Mountain View. And there are many more places to see the transit with amateur and professional astronomers around the San Francisco Bay Area - thanks to this list from the AANC. However, if you don't get out to an event, no need to worry. You won't need a telescope to see this, just eye protection as you would use during any solar viewing, and you will easily spot the disk of Venus moving slowly across the Sun's surface. Make the effort; the next chance will be in 2117.

Image courtesy of Wikipedia.