Hercules

The Stars of Hercules

The early summer skies feature a fascinating constellation that climbs high into the night sky and provides several interesting features to see with the naked eye, binoculars or a telescope. Hercules is the Roman mythological hero that is adapted from the Greek hero Heracles. In the night sky, he is kneeling in the sky with a club overhead, engaged in battle with other mythological enemies throughout the heavens. Similar to Orion the Hunter, Hercules has a distinctive shape; in stark contrast to Orion, Hercules has no bright stars - no first magnitude stars, and only one that is barely second magnitude, and hence Hercules takes some effort to find. But it's worth the effort.

Hercules is visible due east after sunset in June, and is directly overhead by midnight. The middle four stars form a distinctive shape, well known to astronomers as the Keystone. This trapezoidal shape is the center of the figure of Hercules, and it contains a beautiful deep space object known as Messier 13, the Great Globular Cluster in Hercules. It is a spectacular sight to behold in binoculars or a telescope; M13 is a rich cluster that shimmers from the 300,000 stars located in it.

The stars of Hercules are not particularly bright, but they are quite interesting. One of the brightest stars is called Rasalgethi, and it is a a binary star system with a red giant star and a companion that orbit each other every 3,600 years. The brightest star is called Kornephoros, a yellow giant star 148 light years from Earth.

Exploring the heavens is more fun when you know what to look for. Spend a few minutes on Hercules with a telescope or binoculars, and you'll see plenty of interesting objects, even from within a big city.

Image courtesy of SkySafari.

Viewing Gemini and a Deep Space Gem, M35

Spring skies are dominated by an array of bright stars and distinctive constellations. In April and May, the zodiac constellation Gemini dominates the view to the west, gracing the sky with the twin stars Castor and Pollux, and guiding the curious observer toward a gem in the river of the Milky Way, which flows across the legs of the twin brothers.

The star pattern of Gemini is of the brothers Castor and Pollux standing side by side. The bright twin stars represent the heads of the twins, and the stars that are below Castor and Pollux trace out their bodies, arms, legs and even a foot. An advantage to viewing Gemini in the Spring is that the brothers are standing upright and are easy to see, whereas in other times of the year when Gemini is visible, the brothers are not in an easy-to-spot orientation, or are directly overhead, a difficult thing to see.

If you have binoculars, you can try to spot a very faint but beautiful star cluster called M35 near the foot of Castor, the twin on the right-hand side of the pair. You will need a star chart (click on the image above, or try this fine star chart) to locate this small circle of stars but if you have patience and a dark viewing location, you will know you have found it because M35 seems to glow in the view of your binoculars compared to the stars around it. The stars in M35 are quite distant, nearly 3000 light-years away (but still within the Milky Way galaxy).

Happy viewing, and good luck with M35!

Close Encounter of the Pleiades and Moon

The Pleiades is one of the most beautiful star clusters in the sky. In Autumn it rises during the evening and its distinctive glow shines even for urban dwellers. The Pleiades, also known as M45 (from the Messier Catalog), is a collection of relatively young stars (only 100 million years old!) that shine with a blue color due to their hot temperature. The Pleiades are also known as the Seven Sisters and there is plenty of mythology describing each of the seven sisters. Despite the "Seven Sisters" mythology, most people see six stars when they look out at the Pleiades and describe the shape of the asterism as a small Little Dipper. Random fact: the Subaru car company logo is made up of six the stars, Subaru being the Japanese term for Pleiades.

This week on Tuesday evening the full moon passes very close to the Pleiades and in more southerly latitudes it actually occults (blocks out) several of the brightest stars in the cluster. For those of us in San Francisco, the evening of November 3rd should be especially interesting if you view the Moon through binoculars or a telescope. You will be able to notice how fast the Moon moves past the stars of the Pleiades. Although the very bright light of the full Moon will drown out nearly everything around it (including the blue nebulosity of the dust surrounding the Pleiades), all will be clear when you look closely with binoculars or a telescope.

iPhone apps: Star Walk, Moon Map Lite

I love my iPhone. There are many reasons for this, not the least of which are the nifty astronomy apps that are available for the iPhone. These apps bring a universe of information (pun intended) to my fingertips anytime and anyplace.

I've been using these apps while enjoying the rare clear evenings here in San Francisco this summer and will start posting short write-ups of these apps. Although these are not definitive, elaborate product reviews, I wanted to offer some cursory thoughts on a selection of astronomy apps for the iPhone. Here are two, Star Walk and Moon Map (Lite).

Star Walk: ($4.99) I am delighted with this application and have put it to work under different circumstances and in different settings, high on Mt. Tam, in the coastal redwoods where the skies were dark, and in my own backyard in San Francisco under the glow of city lights. Dan Schroeder has an excellent website with a complete review of Star Walk including screenshots.

My personal experience is that the application provides the detail needed while enjoying an evening under the stars. I used it extensively to accurately locate all the stars of constellations when I simply want to know the exact configuration of Bootes or Virgo or Centaurus (as noted in my Mt. Tam blog post). I also used Star Walk with binoculars to find Messier objects in Canis Venatici and Ursa Major this evening and the level of detail was just sufficient to help me to correctly identify these objects.

As with any iPhone application, there is tremendous flexibility to zoom in and out, something that makes map reading feasible on such a small screen. Having all of this detail in my pocket, ready to go at any time, is a very powerful tool for the casual observer as well as the seasoned amateur. My test of technology, hobby toys and computer applications is whether I actually get them out and use them when I should. With Star Walk, I find I am using it more and more often to give me deeper insights into the night sky.

Moon Map Lite: This is a free application (there are standard and "pro" versions that cost a few dollars) and it does just what it claims, providing a nice detailed map of the moon that you can scroll and zoom. The creator of Moon Map has a nice webpage showing all three versions of the application with short demo videos.

Earlier this week the full moon dominated the sky and I spent some time trying to use Moon Map Lite to help me identify some of the major features of the moon. I've not tried to identify more than just a few features of the moon in the past, so I figured this would be a chance to see if I could learn some new craters and seas.

To my dismay, I found this to be considerably more challenging than expected, primarily because the full moon is illuminated in a way that "drowns out" some of the key features of craters and makes them look quite a bit different than the excellent maps in Moon Map. However, I don't blame the Moon Map application for this, but rather my limited attempt to use it during only one phase of the moon. I will try using Moon Map to learn more of the moon's features when the moon is at different points in its orbit, looking for additional details through the telescope that might be easier to see when the sunlight strikes the moon from different angles. And who knows, I might just spring for $2.99 to get Moon Map Pro :-)

Coming soon: I'll review more iPhone apps including Distant Suns, Iridium Flares, ISS Visibility and iSolarScape. If you want to read an excellent group of reviews of star-map applications and see a very helpful comparison chart, look at Dan Schroeder's webpage comparing seven different iPhone apps.