From Skies to Stars - April 2013
The Comet Cometh
By Ed Downs
First a meteor smacks into Russia, and then, just a few days later, we get a close flyby of a good sized asteroid. In cosmic terms, that asteroid came close enough to give “doomsday preppers” reason to celebrate their decisions. It was close. But it is not all scary news. Astronomers who work with visible light, versus those light bands that can be seen only through the use of special instrumentation, have something to celebrate. It seems as though the summit of Haleakala on the Hawaiian island of Maui, at 10,000 feet above sea level, now sports a telescopic array that promises to be the most powerful survey telescope ever built. “Survey” means a telescope that specifically looks for things, all sorts of things, which may be heading our way. It’s called Pan-STARRS, short for Panchromatic Survey Telescope And Rapid Response System. And is the first of a four telescopes array planned.
Pan-STARRS’s most immediate and important goal will be to locate near-Earth objects (NEOs), by finding thousands of asteroids and comets as small as 300 feet in diameter. No, Pan-STARR did not see the Russian event coming. But Pan-STARR does not just look close in to the earth when searching; it looks far out into our solar system, beyond the outermost planets. Basically, Pan-STARR, and its soon to be completed companions, will constantly (and automatically) search and photograph the heavens with 60 large CCD cameras, watching for something to move…when it shouldn’t. That is the signal to pay attention. When the array is complete, about a fifth of the night sky can be surveyed each night. But, does it work? Yes, I give you comet Pan-STARR, named after the telescope that saw it coming.
March was an exciting month for astronomy, as the Pan-STARR comet passed through our solar system. First visible in our hemisphere in early March, it only reached a height of about 10 degrees above the horizon, making it difficult to view. It also appeared at about 30 minutes past sunset, so residual light was a challenge. I packed up my 12-inch reflector telescope and headed for a hilltop on my brothers ranch. A good view of the horizon was possible and our local astronomy club had provided excellent charts as to where to look.
As one soon learns in the world of telescopes, it is less about magnification and more about the choice of eyepieces and field (width) of view. After some searching with a low-power, wide-view eyepiece, Pan-STARR came into view. A quick switch to a higher-power eyepiece disclosed the brilliant nucleus of the comet, a ball of ice and dust a bit more than a half mile in diameter, sporting a “tail” that was an estimated 75,000 miles long.
It was not bright, as a comet can only reflect light; it has none of its own. It was amazing. Pan-STARR lives in the Oort cloud, the outer most limit of our solar system, called the Sun’s cosmographical limit. It may have taken more than a million years for the Sun’s weak gravity to draw Pan-STARR in for a suicidal run at the sun. As the comet gets closer to the sun, solar energy causes the surface of the comet to evaporate, creating microscopic particles that stream away from the sun, catch light, and give us the classic “comet tail.”
Pan-Starr zoomed around the sun inside the orbit of Mercury and took a slingshot ride towards Earth’s orbit. No, it was not a close call, as Pan-STARR passed us a safe 1.09 AU’s away. An “AU” is an astronomical unit, or the approximate distance from the earth to the Sun, roughly 93 million miles.
I could not get over the fact that I was looking at an object that had traveled more than one light year (light travels at 186,000 miles per second) from the Oort Cloud (50,000 AU’s away) just to give me a view of a 300-foot pile of galactic ice and dust. Remarkable performance is available from telescopes available for amateur use. Fortunately, this experience was enjoyed by family and friends.
Okay, you missed Pan-STARR, but you have a second chance. Amateur astronomers Vitali Nevski (in Belarus) and Artyom Novichonok (in Russia), using a 16-inch reflector that’s part of the worldwide International Scientific Optical Network (ISON), spotted something that moved last September. While typically named after the individuals who discover a comet, technicalities cropped up and a compromise was struck by naming this visitor “Comet ISON.” The comet is inbound from the Oort Cloud and will pass very close to the Sun – just 725,000 miles on Nov. 28, 2013. Comet ISON will be visible about a half hour before sunrise and has the potential to put on quite a show.
There is plenty of time to hit the websites of companies like Orion, Celestron and Mead, as well as www.skyandtelescope.com/letsgo for tips for beginners. You may be surprised that excellent, fully automatic, self-seeking (go-to) telescopes start at about $300 and excellent table-top scopes come in at $100. Don’t miss Comet ISON like you did Comet Pan-STARR. One hundred thousand years is a long time to wait for their next trip past our planet.
