Comet ISON, the potentially mighty comet discovered late last year by members of the International Scientific Optical Network (ISON), has been running much dimmer than expected for months. But last week, there appeared to be signs that it had finally "turned on."
These next two weeks, the comet is diving at incredible speed toward a Thanksgiving Day close encounter with the sun, passing very close in our sky to our lines of sight with the bright star Spica and the paired bright planets Mercury and Saturn. Will the comet brighten enough to be seen with naked eye or binoculars near these objects in the dawn?
How much will the comet brighten? Even if Comet ISON doesn't brighten greatly in the next two weeks, it may flare tremendously as it passes less than 1 million miles from the sun's surface on Thanksgiving.
Last week, however, the water vapor production rates of the icy, warming comet suddenly doubled in a day or two. If - still a big if - this trend continues, the comet is likely to brighten rapidly. It might by the end of this week become easily visible in binoculars or even to the naked eye.
Wonders we might see. However bright ISON gets, late this week is the last chance in November to see it before bright moonlight and bright twilight interfere with viewing. Go to www.skyandtelescope .com or www.spaceweather .com to see detailed maps for finding it, low in the east, around 5:30 a.m. each day.
Sunday and Monday, Nov. 18, Comet ISON lies dramatically near one of the sky's brightest stars, Spica.
Here in the eastern U.S. on Sunday morning, the fuzzy patch of the comet's head will be located about 2 degrees - about the width of your thumb at arm's length - to the upper right of Spica and then, the next morning, less than 1½ degrees to the lower left of Spica. Will the comet's tail be bright enough and long enough then to be glimpsed at least with binoculars? If so, it should point to the upper right.
Comet ISON passes Mercury and Saturn closely in sky. Next week, Comet ISON appears lower - but hopefully brighter - each day. Get an unobstructed view of the east-southeast horizon and look low in that direction around 6 to 6:15 a.m. The brightest object you'll see is Mercury.
On Friday, Nov. 22, Comet ISON will shine about 5 degrees - about half the width of your fist at arm's length - to the right of Mercury. And about equally far to the lower left of Mercury will be a considerably dimmer planet, Saturn.
On Saturday, Nov. 23, Mercury, Saturn and Comet ISON will form a compact triangle (it'll fit into the field-of-view of most binoculars) with ISON directly right of Saturn and lower right of Mercury. The next day, the planets are only 2 degrees apart and the comet much farther to their lower right.
Finally, on Monday, Nov. 25, Mercury and Saturn are a dramatic pair less than a degree apart, and ISON is well to their lower right. In fact, the comet will be so low in such bright twilight that it may be visible only in binoculars or telescopes for a little while around 6:25 a.m.
Last week's partial eclipse of the sun. At sunrise, Nov. 3, I was watching from the Delaware Bay marshes and had a narrow cloud band that was out to sea block my view of the sun when the sun was right on the horizon. When it peeked above the cloud band, the sun was no longer dimmed enough by horizon haze and thickest atmosphere to view directly.
So at that point, I had to use aluminized Mylar "eclipse glasses" with unaided eye and a telescope to project an image of the sun with beautiful sunspots and almost half the moon's silhouette in front of it.
Fred Schaaf is a local author and astronomer. He can be reached at: firstname.lastname@example.org.