20 December 2009

Jupiter and Neptune Triple Conjunction: The Finale

For much of 2009 Jupiter and Neptune have been sharing the same space in the sky inside the Zodiac constellation Capricornus. Over the last few months they have moved progressively closer to each other and are now aligned in what is called a "Conjunction." In fact, the year 2009 saw this happen three times in a row, what astronomers call a Triple Conjunction, a rare and beautiful alignment of heavenly bodies.

I had not seen Neptune before this year's Triple Conjunction. A conjunction creates an opportunity to easily locate the less-bright planets Neptune and Uranus. These two are just dim enough to be invisible unless you (a) know exactly where to look, and (b) use optical aid such as a telescope or binoculars. With bright Jupiter as my guide, I was easily able to find Neptune lurking in the neighborhood, a beautiful blue pinpoint of light (see my previous post on the subject, Blue Neptune). The third of the three conjunctions of Jupiter and Neptune is even easier to find this week because the waxing Moon passes just above the duo on the evenings of December 20 and 21. In fact, the Moon makes a splendid guide to the planets each month, having just passed near Mercury a few days ago, and later in the month approaching orange-red Mars and yellow-white Saturn.

For a more detailed view of the paths of Jupiter and Neptune across the night sky check the diagrams on Martin Powell's excellent astronomy website. With these detailed charts, you can get a clear perspective on how these objects slowly make their way from one Zodiac constellation to the next every year. As Jupiter now begins prograde motion away from Capricornus, it will speed across Aquarius and into Pisces during the winter and by spring will be closing in on Uranus, where in 2010 we will have a Triple Conjunction of Jupiter and Uranus. Scroll down this page to see an excellent animation showing the motion of Uranus and Jupiter across the sky in 2010. The heavens never cease to offer up opportunities for discovery. Here's to clear skies!

12 December 2009

Geminid Meteor Shower 2009

One of the finest meteor showers of the year is the Geminids, so named because the meteors appear to emanate from the zodiac constellation Gemini. The shower peaks this year on Sunday evening December 13th and for us on the west coast of the United States, we will be well placed for the peak of the shower at 9:00 pm. Given that there won’t be any moonlight for this meteor shower, conditions are ideal for a good shower that can produce up to 120 meteors per hour in very dark conditions. For those of us who live in urban areas such as San Francisco, we will see considerably fewer meteors. Nonetheless, if you can get yourself away from streetlights, houselights and allow some time to adapt to the dark, you will see some Geminids.

Meteor showers that occur at the same time every year are usually caused by some kind of debris trail that the Earth intersects, showering the upper atmosphere with fine particles in an unusually intense period of time. Based on the way in which the Earth intersects the tiny bits of rock and dust, the meteors will all appear to originate in a single point in the sky, a point known as the "radiant." The Geminid meteor shower appears to originate in the constellation Gemini and as this constellation rises shortly after sunset, this particular meteor shower appears strong all night long, as Gemini treks across the sky from the east nearly directly overhead and then dropping into the west.

NASA has a great website talking about the origins of the Geminids, and Sky & Telescope Magazine has a very helpful article (written by Tony Flanders, an astronomer I've come to know personally) that is full of good tips for seeing the Geminids.

The weather outlook is always a challenge for December, and if the skies are clear they are most assuredly accompanied by a cold evening, so dress extra-warmly for the Geminids and enjoy.

09 December 2009

The Northern Sky: Circumpolar Stars and Polaris

I enjoy stargazing for many reasons, one of which is to get a sense of the motion of the sky as viewed from our vantage point here on Earth. As I have traveled around the globe, I've always tried to observe how the sky changes depending on where you view it from. One of the more fundamental things you can observe is the dynamic of the stars and constellations in the northern sky. For those of us who dwell in North America, we see the north star, Polaris, at the same height in the sky as we are located north of the equator. That is, for San Francisco at approximately 38 degrees north latitude, Polaris can be found due north, 38 degrees above the horizon.

For reasons you can read about in Wikipedia, Polaris does not move in the sky and therefore is never below the horizon. It is always fixed in the north above the horizon at the same arc as you are located north of the equator. However, the stars that surround Polaris also never dip below the horizon, but rather circle around Polaris in a 24-hour spiral that turns counter-clockwise. Long-exposure photographs show this effect very vividly.

Wonderful constellations and asterisms occupy the circumpolar region of the sky, including the Big and Little Dipper, Cassiopeia, Draco and Cepheus.

07 December 2009

Astronomy Gifts for the Holidays / Telescope Shopping

If you are considering a gift for someone who enjoys astronomy (or want to share something with a young person who might like to discover astronomy), I present to you my astronomy gift guide for the holidays.

A. Astronomy Gifts.

At my local astronomy shop here in San Francisco, Scope City, I asked manager Sam and salesperson Steve what they would recommend for the holidays. Telescopes are plentiful and that warrants a separate section of this blog post - see below. But aside from telescopes, there are binoculars of all types, excellent books, tools such as Star Finders and Planispheres, and new this year, the Sky Scout, a hot selling item from Celestron that has the astronomy hobbyist world abuzz. Point the Sky Scout at an object in the sky and it tells you what the object is and provides additional details. For another approach, you can open a door for astronomy for someone with a gift subscription to Astronomy Magazine or Sky & Telescope Magazine.

B: Telescopes - Top 5 Things to Consider When Buying a Telescope

A telescope is a powerful scientific instrument which, when well cared for, can provide years of viewing pleasure. Top brands include Meade, Orion and Celestron. However, there is a very wide range of options, quality and performance to choose from so before you buy a telescope learn a few things about them. Telescopes.com offers some useful background information, as does Astronomics.com with its informative pages. The Bad Astronomy blog has a helpful article, and this post provides a lot of detail for the telescope shopper. If you summarize all of the articles and if I draw from my own experience, I would recommend five things to think about when purchasing a telescope.

1. Consider Binoculars. They are easy to use, can be used at daytime as well as nighttime, cost less than a telescope, and are a good first test of one's interest in the night sky.

2. Buy quality. Avoid the cheap telescopes at the department stores. They not only have generally poor quality optics, but end up being a turn-off for those who purchase them. It's worth the extra money to get something you will enjoy.

3. Start simple. As much as the high-tech telescopes look like fun, they are still complex instruments that will need some degree of care-and-feeding when you use them. The most basic scopes, simple refractors on a lightweight tripod, take little time to set up and are the most simple to use. Also, a simple telescope is not as bulky and heavy to carry around. For kids, try out the Celestron FirstScope (see below).

4. Be comfortable. You really need to feel at ease with a telescope, so in the best case go to your local astronomy shop and try out a few. Scope City will let you take their binoculars and telescopes out in front of the store and do the "Safeway Test" to see how well you can resolve items in the aisles of Safeway grocery store next door.

5. Learn to use your telescope at your local astronomy club. Amateur astronomers like to help others to learn about astronomy. The San Francisco Amateur Astronomers and San Francisco Sidewalk Astronomers hold Telescope Clinics at their monthly star parties. These are excellent venues to bring your scope and learn to use it with astronomy enthusiasts. Check the Night Sky Network for a club near you.

C: For Young People.

Kids can benefit from astronomy gifts that are easy to use and make it simple to immediately start enjoying. I found numerous websites that showcase books for kids. Skymaps.com has a very well organized list of books for different age ranges, all the way from age 4 to young adult and educator. The Top 10 Astronomy Books for Kids on about.com offers some good choices. On the telescope front in 2009, Celestron premiered the FirstScope, an extremely simple telescope for kids that, from the reviews I've read, is surprisingly good quality yet very low price (about $50 at most outlets). It is an 'official product' of the International Year of Astronomy (IYA) celebration. But in the end I was most enamored with this simple recommendation from the Suite101.com blog:

"What children really need, more than 'stuff,' is for someone to take the time to stand outside with them on a starry night and point out planets and constellations. Teach them the sky. You can give coupons good for '1 Hour of Observing with Mom' or something similar."

Happy Holidays. Stay warm and enjoy the long dark nights.

02 December 2009

Get Involved: Astronomy Lectures, Star Parties and Telescope Workshops

There are many ways to get involved with astronomy here in San Francisco, or wherever you may be. A great resource for finding events in your neighborhood is the Night Sky Network, a resource chock-full of information from astronomy clubs across the United States. Just enter your location and you can find out what is happening in your area.

Here in San Francisco, the California Academy of Sciences has an astronomy lecture series called the Benjamin Dean Lecture Series. The next lecture in the series will be on Monday December 7th. The topic is Saturn, presented by Dr. Carolyn Porco, the director of the imaging team for the Cassini spacecraft that is orbiting Saturn. You can get tickets for the December 7th Dean Lecture online.

The San Francisco Amateur Astronomers (SFAA) have their monthly meeting at the Randall Museum on December 17th and their "City Star Party" on December 26th at Land's End in San Francisco. The City Star Party on the 26th (weather permitting) will be a great chance to bring out new holiday gifts such as telescopes and binoculars and learn to use them alongside amateur astronomers. The SFAA and the San Francisco Sidewalk Astronomers have free telescope workshops before each City Star Party but please RSVP to them at clinic@sfsidewalkastronomers.org if you plan to come on December 26th.

I hope to see you at an upcoming event!