Thursday, April 2, 2009

Life List

The typical beginning stargazer is not going to run out and look at the two celestial objects I’m about to describe. They should be considered targets for advanced observers, however, they are companions to familiar objects accessible to your naked eye. So you can run out and look at their “host” objects naked eye, and then live vicariously through my observing accounts of these tag-alongs.

Both objects were on my observing Life List and now have satisfying, indelible-ink checkmarks next to them. The lesson herein is to— if you haven’t already— start a Life List.

A Life List is the wish list of objects/phenomena you’d like to see during your observing lifetime. Generally a Life List contains challenge objects— objects that are difficult to see, objects that require a bit more effort, the right equipment, travel to a different latitude, and/or perfect sky conditions. A Life List is a fluid thing. I’m not sure you ever actually complete it. Check off a couple items, and more mysteriously appear.

How do you start a Life List? You might hear a more seasoned astronomer wax poetic about “the time I saw X after hiking 15 miles with a 60-pound scope on my back and waiting for the only ten-minute break in the clouds.” Or you might read something intriguing in an astronomy magazine or on a website, and think, “I’d like to see that!” And so a Life List begins.

Here are some of the items currently on my Life List:

Aurora borealis, aka the Northern Lights
The aurora is the colorful, undulating sky display that occurs primarily in arctic regions. Particles from the solar wind slam into Earth’s atmosphere at the poles and excite the gasses there.

I’ve only been in arctic regions once, on a trip to northern Scotland. Did I see the aurora? Of course not! Canada, here I come (some day).

The Northern Lights
Copyright 1995-2003 Jan Curtis

The dwarf-planet-formerly-known-as-a-planet is still a goal, regardless of its status. Perhaps it’s a New Mexican thing, since Pluto’s discoverer, astronomer Clyde Tombaugh, made his home in New Mexico. Seeing Pluto requires a commitment of several nights of observing. Since the tiny rock looks like a star— surrounded by stars— you must watch it move relative to the background of stars over a few nights to be certain you are observing the real McCoy.

Clyde Tombaugh, discoverer of Pluto

Magellanic Clouds
These are two companion galaxies to our home galaxy, the Milky Way. They are dwarf galaxies, much smaller than our Milky Way, whose gravity has disrupted and distorted the little galaxies’ structures. Known as the Large Magellanic Cloud and the Small Magellanic Cloud, they are easily visible to the naked eye from the Southern Hemisphere. Yup, I’m saving my pennies for that trip to Australia.

Diamond Ring
As you know, diamonds are a girl’s best friend. But the sparkler I’m holding out for is in the sky— the daytime sky, as it were. The Diamond Ring is the effect seen just before and just after totality during a total solar eclipse. It’s caused by a last (or first) ray of sunlight peeking through a deep lunar valley. The soft glow of the Sun’s corona illuminating the perimeter of the Moon and the brilliant point of light combine to resemble a diamond ring.

A total solar eclipse is when the Moon passes between the Earth and the Sun and is aligned such that it completely covers the Sun’s disk. Totality is the period of time during which the Moon completely covers the Sun’s disk.

Anyone for mainland China in July?

Then there’s 3C 273. But more on that later.

Back to my original topic, an observing account of the two tag-along objects, in the order in which I saw them.

Tag-along Object #1
On January 31 of this year, I decided to try to see Sirius B. It had been on my Life List for awhile, and I’d already made several unsuccessful attempts to see it. What I had going for me this time were steady, clear sky conditions, and a tracking telescope with an occulting eyepiece.

The equipment was not mine. For those of us with one low-tech telescope to our names, working on the Life List is best accomplished as a communal activity. Be an instigator! Get everyone around you on the observing field worked into a froth about what it is you’re trying to see, and pretty soon you’ll have all sorts of people and equipment resources dedicated to the quest. Oops, I’ve divulged my secret strategy. The jig is up.

Sirius B is the incredibly dim companion star to Sirius, the Dog Star, the brightest star in the night sky. Sirius is prominent in the night sky in winter and spring, and you can easily spot the brilliant star by looking east and south of Orion the Hunter.

Sirius A (the bright one you see naked eye in the sky) and Sirius B are a binary system, that is, they are in orbit around one another. The elusive, hard-to-spot Sirius B is 10,000 times fainter than Sirius A, in large part due to its relatively diminutive size. Sirius B is slightly smaller than Earth, whereas Sirius A is 3.5 times larger than our Sun. To illustrate the scale of Sun and Earth, if the Sun were the size of a bowling ball, Earth would be the size of a peppercorn! So you can see that Sirius B is a smidge. Plus it tends to be hidden in the glare from blazing Sirius A.

Sirius A and B vary in their distance from one another due to their eccentric orbits. They are currently separating, with maximum separation predicted for the year 2019. So the next ten years or so is an excellent window of opportunity for spotting Sirius B.

On the fated night, at a dark observing site, we combined my observing partner Carl’s occulting eyepiece and observing buddy Dave’s tracking telescope. The occulting eyepiece was simply a 15mm eyepiece that Carl had modified with a thin piece of black electrical tape carefully affixed inside the open end. The result is a thin, opaque bar that bisects your field of view when you look through the eyepiece. It’s great for blocking out bright objects when trying to see dim objects hidden nearby in the glare. You simply position the scope so that the bright object is occulted under the opaque bar and then scan the area around it for the faint object.

Having the eyepiece in a tracking telescope can make all the difference. Otherwise, due to the Earth’s rotation, the bright object is constantly re-emerging from under the occulting bar and you’re constantly nudging the scope and twirling the eyepiece in the focuser in order to put it back underneath. It is, at best, annoying. At worst, you can’t focus long enough on any one spot to look for your target.

We used the same doctored eyepiece with great success to cover bright Mars and view its pinprick-sized moons, Phobos and Deimos, during Mars’ close approach in August 2003. Ah yes, Phobos and Deimos, former tenants of my Life List.

With the right eyepiece and telescope, it didn’t take the three of us long to spot the bright dust mote swimming near the edge of the glare. Success! It was the first glimpse of Sirius B for all three of us. Soon, others on the field came over for their first look also.

I know you’re just dying to know what Tag-along Object #2 was. Tune in next week, for the exciting conclusion!

Astronomy Essential: The solar system is much larger than the orbits of the planets.

When we think of the solar system, we think of the Sun and a series of roughly concentric planetary orbits, concluding with Neptune (or Pluto, depending upon when you went to elementary school).

In reality, the solar system is much larger. The term solar system means “system of the Sun,” that is, the area of space where the Sun exerts its gravitational influence.

Beyond the planets are the Kuiper Belt and the Oort Cloud. The Kuiper Belt (pronounced KIGH-purr) is a large band of small, rocky bodies beyond the orbit of Neptune. Beyond the Kuiper Belt is the Oort Cloud (pronounced ORT), an immense, sphere-like cloud of an estimated one trillion comets. The Oort Cloud marks the outer edge of the solar system.

The Oort Cloud is estimated to lie nearly one light year from the Sun. A light year is the distance light travels in one Earth year, nearly six trillion miles. By comparison, Neptune’s orbit lies only 2.7 billion miles from the Sun.