30 September 2011

Mars passes through a star cluster, the Beehive

Our fellow planets in the Solar System are on the go, always wandering from place to place in the sky. The rocky planets (Mercury, Venus, Mars) move quickly, due to their closer proximity to the Sun, and their motion from day to day can be noticeable to the naked eye. The gas giant planets (Jupiter, Saturn, Uranus, Neptune) move more gradually but are nonetheless regularly moving against the backdrop of stars.

Mars, being our 2nd-closest Solar System neighbor, can appear to move quite considerably against the backdrop of stars from one night to the next. This week, it will pass through the constellation Cancer and in doing so, travel through one of the most well-known star clusters in the heavens, the Beehive Cluster. This will be a fine site even in city skies, but you will need binoculars to truly appreciate the view. Use the diagram to find this spectacle in the early morning sky, looking due east (just as I can see when I walk out my front door in the morning). Enjoy!

Image courtesy of Sky & Telescope Magazine.

27 September 2011

Observing Twilight into Dusk

The minutes after sunset are some of the most beautiful, as the last rays of sunlight have disappeared and the sky begins its daily transition from bright blue to dark night. Looking west after sunset in the early days of Fall, you quickly find Arcturus shining due west, at first looking almost like an airplane that is moving very slowly. But soon you realize that this is a star, the third-brightest in the heavens. It is bright enough to shine clearly through the glow of twilight. The colors of the sky are changing rapidly during twilight, and the brightest stars soon emerge. In late September, you can easily find the fifth-brightest star in the heavens, Vega, directly overhead, guiding you to its neighbors Deneb and Altair in the Summer Triangle. And looking back toward the western horizon where Arcturus is shining, you can soon find the red supergiant star Antares shining low to the left (south-west) of Arcturus.

Later this week, the young Moon arrives in the twilight sky and passes near Antares. Find a nice western horizon, get comfortable, and enjoy the evening show that is pleasant, relaxing and beautiful to see.

Image courtesy of Sky & Telescope Magazine.

19 September 2011

Autumnal Equinox: what do you see?

Friday September 23rd is the start of Fall here in the Northern Hemisphere, an event that has a specific moment, in this case 2:05 am on the West Coast. What happens at this moment? Can you 'see' an Equinox?

The two Solstices of the year, in December and June, get much more fanfare because they mark more dramatic transitions, both in the weather and in the slow change of the seasons. The longest day and shortest day of each year are much easier to understand. But the balance points in the equation of Earth's orbit, the Equinoxes, get much less attention because there is much less drama. But for me, there is a lot going on. From an observational point of view, there are three things to look for.

1. Sunrise is precisely due East and Sunset precisely due West, the two days of the year this happens.

2. The Sun is above the horizon 12 hours and below the horizon 12 hours (give or take a few minutes owing to the bending of light around the horizon as experienced at Sunrises and Sunsets).

3. The Sun's height in the sky at local noon, as measured in degrees above the southern horizon, is 90 degrees minus your latitude on Earth. For example, in San Francisco, we are about 38 degrees north of the equator, so the Sun's height at local noon is 90 - 38, or 52 degrees above the horizon.

There is a fourth, more subtle effect that happens around the time of the Equinox. The length of the day is changing most rapidly around this time. From the Summer Solstice to the Winter Solstice, the length of the day is continually reducing. On the Equinox, it is 12 hours, but from one day to the next the length changes about 2 1/2 minutes, around 16 minutes during the full week. That is noticeable, and if you get up at the same time each day, you are certainly aware of the changing light of the morning (or lack of light at this point in time).

The combination of the Earth's annual circuit around the Sun, the tilt of the Earth's axis, and the slightly eccentric orbit of the Earth around the Sun all contribute to very interesting effects that are most pronounced around the interesting transition points of Equinoxes and Solstices. Take a moment this Friday to appreciate what you are observing in the sky around you.

16 September 2011

KFOG Podcast - Sep 16, 2011

Today's discussion with KFOG's Irish Greg features (a) the Milky Way in the Autumn Sky, (b) Fireball across Southern California, (c) new planets being discovered, and (d) the Supernova in the Pinwheel Galaxy. As always, it's good fun and in exactly 8 minutes, you'll be a more informed citizen scientist. Click here to listen.

08 September 2011

Seeing the Supernova in the Pinwheel Galaxy

This week we can witness, first hand, a supernova that was just discovered in the Pinwheel Galaxy. A supernova is an explosion that marks the end of the life of a star, and usually these fiery events emit a great deal of light, brighter than anything else in the region for a short period of time. In this case, the star was a white dwarf of similar mass to our own Sun, but located 21 million light years away in a relatively-close galaxy. It is brightening and will be visible at its peak this weekend. However, you will still need patience and some kind of optical aid (telescope or binoculars) to see this.

The Pinwheel Galaxy (also known as M101) is located near the Big Dipper, quite high in the sky after sunset, so use the handle of the Big Dipper to help you located the Pinwheel Galaxy. Supernova discoverer Peter Nugent of Berkeley explains how to find the Supernova in this short video. To set expectations, the supernova will be a bright spot of light, similar to a star, so don't expect to see a vast region of glowing gas and colors, but nonetheless, you can be assured that the light you are seeing has been traveling for 21 million years directly from one of the most violent, cataclysmic places in our universe, at a moment just after a star's life has ended and new matter has been created. That is a good thought to ponder as you search for the supernova.

Good luck, and leave a message if you find it!