25 August 2012

The Galactic Center: Staring Into the Heart of the Milky Way

Summer is prime time to look into the heavens and touch the wonder of the Galactic Center, the heart of our own Milky Way galaxy. Two bright constellations guide you to the center of the Milky Way, Scorpius and Sagittarius, which are easy to spot due south each evening shortly after sunset.

The Galactic Center
Our own Sun and Solar System occupy their special place 30,000 light years from the center of the Milky Way, and as we look out and around us into space, we view our own galaxy from within, along the spiral arms and toward the center. Many have seen the lovely band of the Milky Way when camping or far away from city lights, but the faint river of light is all but invisible in any urban area. Nonetheless, with binoculars, you can see deeper into the sky and discover some of the deep space wonders and faint objects that are visible between our own location and the center of the galaxy, an area full of star clusters and nebulae. So I encourage everyone to get a pair of binoculars, face south, and using the star chart (above) as a guide, aim between Scorpius and Sagittarius and meander from there upwards. You will encounter the Lagoon Nebula and the nearby Trifid Nebula, easily visible in city lights if you use a telescope or binoculars, and many more Messier Objects, the fuzzy blobs that dot the sky near the Galactic Center.

In six months, when the Earth has traveled half-way around the Sun, we'll be able to look in the opposite direction, toward the Galactic Anticenter, as I have described in a previous blog post. That is interesting to consider, but more exciting is the Summer when we can enjoy our own galaxy's finest wonders on full display.

Here's a link to an image of the Galactic Center on Sky & Telescope's website.

Image courtesy SkySafari.

21 August 2012

Planet/Star Trio Fades into the Sunset

The "Trio" fading into the sunset
I've enjoyed watching the changing view of the evening sky over the past months, in particular as the pair of Saturn and Spica have become a trio with Mars. Saturn and Spica straddle the ecliptic and Mars has raced from its location far to the west of the pair in Spring, to a near-split of the two last week, and now as the trio fades into the sunset, Mars is continuing to glide eastward, this week being joined by a crescent Moon.

I've been pointing out this dynamic at star parties for the past few months, as it vividly illustrates the motion of planets in our Solar System, and it also highlights the differences in perceived speed of the outer planets, with Mars circling the Sun every 2 earth-years, and Saturn taking nearly 30 earth-years to accomplish the same.

Image courtesy Sky & Telescope.

08 August 2012

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."