|8/17/2013 8:58:00 AM|
Year of the comet
|Sisters Astronomy Club member Jim Hammond captured this picture of comet PANSTARRS from near his home southeast of Sisters on the evening of March 31, 2013. The fuzzy object above the comet is the Andromeda Galaxy. |
photo by Jim Hammond
By J. Thomsa JeffreyEarlier this year, sky watchers were excited by the prospect of being able to see two bright comets in 2013. The first was due by late winter/early spring and some predictions claimed it might become as bright as the planet Venus. Then, in late fall, an even brighter comet is to light up the night sky.
The following is a description of what has happened so far:
Comet C/2012 L4 PANSTARRS was discovered in June 2012 by the Panoramic Survey Telescope & Rapid Response System telescope located at the summit of Haleakala on Maui, Hawaii. It took the comet millions of years to reach the inner solar system from the Oort Cloud, a huge spherical collection of billions of icy bodies left over from the formation of the solar system extending out to one light-year from the sun.
The orbital period of the comet is estimated to be 106,000 years, and its nucleus is thought to be 0.6 miles in diameter.
Comet PANSTARRS was visible from both hemispheres in the first weeks of March, and approached to within 93 million miles of Earth on March 5, 2013.
Many astronomers thought the comet would become as bright as the planet Venus. However, in January 2013, there was a noticeable slowdown in the comet's brightening that continued through the month of February. As a result, the comet only reached a magnitude of +1, about the same brightness as the reddish star Antares in the constellation Scorpius, currently visible in the southwest at nightfall.
During the time when the comet was at its brightest, it was still close enough to the sun that evening twilight made locating it difficult. There were very few reports of people being able to see the comet without some type of optical aid, though it did show up better in photographs. The comet was best seen through binoculars about 40 minutes after sunset.
Sisters Astronomy Club (SAC) member John Huntsberger, who winters at his home in Austin, Texas, reported having fine views of the comet. "PANSTARRS was visible to the people in my Lifetime Learning Astronomy class in Austin during March of this year. I set up my 9.25-inch Celestron telescope just east of Austin where the class was held and we could see the comet and its tail about 13 degrees above the western horizon," said Huntsberger. Several of his students commented that it was a lifetime experience for them.
Members of SAC showed the comet to people in the community on several occasions. For many, these sessions were the only opportunities to see the comet.
While PANSTARRS was drawing most of the attention, a slightly dimmer comet also made its way into the inner solar system.
Comet C/2012 F6 Lemmon was discovered on March 23, 2012 with a telescope located at the summit of Mt. Lemmon in the Catalina Mountains north of Tucson, Arizona. Like PANSTARRS, comet Lemmon is a long-period comet that also came from the Oort Cloud. It has an orbital period of about 11,000 years.
Because this comet has a steep orbit inclined 82.6 degrees relative to the ecliptic, it was visible from the northern hemisphere last year from September through December. It then moved into the southern hemisphere and became barely visible to the naked eye in January and February. In early May the comet returned to the northern hemisphere, positioned very low in the eastern sky just before morning twilight. But by then the comet had faded and could only be seen with the aid of binoculars or telescopes. By July it was high enough that it could be seen in the evening sky.
Comet Lemmon was viewed by members of the local community at several public observing events put on by SAC.
Comet C/2012 S1 ISON, dubbed by some astronomers to become the "Comet of the Century," will be visible later this fall. It will become visible through modest-sized telescopes by the end of August. Will ISON dazzle or disappoint? Stay tuned.
To learn about astronomy-related programs and events, visit www.sistersastronomyclub.org.
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