The astronomical story that is drawing the most attention this fall is Comet ISON.
Comet ISON (official label: C/2012 S1) was discovered on Sept. 21, 2012, when it glowed at a feeble magnitude 18. At that time the comet was still beyond the orbit of Jupiter and ISON’s brightness was unusually high for a comet that far from the sun.
This gave rise to speculation that ISON could be brilliant by November 2013. It is virtually certain now that Comet ISON will not be the "galactic fireworks show" that some people predicted earlier in the year.
On Thursday, the comet was shining in the predawn sky at 4th magnitude. Fourth magnitude should be bright enough to be seen with the naked eye, but you would need a dark sky with no clouds, no vog, no haze and no moonlight. Even professional and dedicated amateur astronomers have had a hard time seeing the comet with the naked eye.
Generally you still need binoculars or a low-power telescope to see the comet, assuming it emerges from out of the sun’s light in early December. In binoculars the comet appears as a fuzzy star with a hint of a tail.
The comet makes its closest approach to the sun ("perihelion") on Thanksgiving Day. This passage through perihelion is the moment of truth. No one knows if the comet will break apart as it passes through perihelion, or if it will emerge intact.
If it does survive the passage, it may well be a good viewing object in the December morning sky.
Assuming ISON re-emerges from behind the sun in early December at all, it will again be a predawn object, as it was in mid-November. Between Dec. 5 and 10, look east just before dawn (5:45 a.m.). Find the brilliant light of planet Saturn, which at 0.57 magnitude is the brightest dot low in the east. Saturn is really low in the east at 5:30 a.m., about 8 degrees above the horizon (a little less than the width of your palm at arm’s length).
Look to the lower left of Saturn about 20 degrees (the width of two palms, held at arm’s length) and try to see Comet ISON rising. Each morning Comet ISON will rise a little earlier, and will be higher in the east as day breaks. At the same time, it will also be fainter with each passing morning.
Given the unpredictable nature of this comet, it’s a good idea to check bit.ly/Ww6JxQ, a daily blog at Sky and Telescope magazine that has the latest in the brightness and appearance of ISON. More information on ISON is also available at www.astronomy. com/ison.
SPACE STATION
There is a bright appearance of the International Space Station on the morning of Dec. 1. The station appears low in the northwest at 6:19 a.m. Over the next seven minutes it will pass almost across the top of the sky, vanishing low in the southeast at 6:26 a.m.
If you prefer to hunt for the space station in the evening sky, there is a bright appearance of ISS on Dec. 6. The station will rise in the southwest at 6:47 p.m., pass very near Venus and a crescent moon, then pass high across the sky to the northeast, vanishing at 6:52 p.m.
Check the appearance of ISS and other satellites at heavens-above.com before you go out and look for a satellite. Sometimes the predictions change.
DECEMBER PLANETS
Venus is that airplanelike dot in the west as it gets dark. The planet continues to shine around minus 4.5 magnitude. At the start of December, Venus emerges low in the west at dusk and sets around 8:45 p.m. By Dec. 15, Venus sets by 8:15 p.m. By the last day of 2013 the planet barely has time to emerge in the twilight before it sets at 7:15 p.m. By early January, we’ll lose the planet entirely.
Look for the waxing crescent moon close to Venus on the nights of Dec. 4 and 5.
In early December, Jupiter rises in the east at 8:30 p.m., crosses the top of the sky at 3 a.m. and is still high in the west at daybreak. By the end of December, Jupiter rises in the east right at dusk, crosses the top of the sky at 1 a.m. and sets in the west at daybreak. Look for a fat moon next to Jupiter on the evening of Dec. 18.
Mars rises in the east around 1:30 a.m. at the start of the month, and by 12:45 a.m. at the end of December. By the end of the month, Mars will be at 0.85 magnitude, the brightest it has been for two years.
Mercury shines brightly in the east before dawn in the first week of December. On the morning of Dec. 1, Mercury rises at 5:50 a.m., shining at minus 0.65. On that morning only, look for the old, slender crescent moon above Mercury, and look for Saturn right above the moon. You’ll only have about 25 minutes to catch the scene, since day breaks around 6:15 a.m.
For the next week, Mercury will rise in the east just before daybreak. It will remain bright, but the time between Mercury’s rising and daybreak will get more and more narrow. By Dec. 8, Mercury comes up at 6:05 a.m., with barely enough time to see it low in the east before day floods the sky.
Try to catch the crescent moon between Mercury and Saturn at 5:55 a.m. Dec. 1.
GEMINID SHOWER
The Geminid Meteor Shower peaks on the nights of Dec. 12-13 and 13-14. The Geminids are one of the best showers, and we in Hawaii often have good weather in December to see it.
The waxing gibbous moon will provide some interference until it sets at 3:45 a.m. on Dec. 13 and 4:45 a.m. on Dec. 14.
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Mike Shanahan is director of education, exhibits and planetarium. For more information, go to www.bishopmuseum.org/planetarium/planetarium.html.