by Akkana Peck
The big shallow-sky story in November is Comet C/2012 S1 ISON, brightening to naked-eye levels as it approaches its peak next month.
So far, ISON isn’t quite living up to some of the hype we heard earlier in the year. It may be as much as two magnitudes fainter than the early predictions had indicated. But don’t give up hope — ISON could still turn out to be a very nice comet.
It will likely be only around sixth magnitude as November opens — just barely naked-eye visible, if you go to a dark sky site like Coe or Fremont Peak — but will brighten to around second magnitude by later in the month, comparable to the stars in the Big Dipper.
Here’s the bad news (at least, it’s bad for a lot of us) — ISON is still a morning object, and will remain so for nearly its whole pass. At the beginning of November it rises at about 3:30 am, then moves to about 3 am by the second weekend. But by the 16th, it’s later again, not rising until 4 am (sunrise is around 6:50) and by a week after that, it’s so close to the sun that it’ll be tough to spot at all.
As November opens,, the comet will hang between Mars and a slim crescent moon in the dawn sky. It remains there, with the tail (whatever tail it might have by then) sweeping toward Mars, for the rest of the week, though of course the moon will move on. A nice opportunity for early rising photographers!
As the month continues, ISON should brighten steadily, but it will also rise later as it moves sunward. That means it’ll be harder to spot. But it’s worth trying — particularly on November 23 and 24, when ISON will be close not only to Saturn and Mercury, but to another comet, 2P Encke, all four of them fitting in a roughly 6-degree field along with the magnitude 2.8 star Alpha Librae (Zubenelgenubi).
Six degrees isn’t small enough to get them all in a telescope together, but wide-field binoculars should be able to fit them in. ISON should be around second magnitude by that time. (Some sites have predicted that it will be brighter than Venus by this time in November, but don’t count on it.) Encke is a much fainter magnitude 4.8 — it’s reported to have a green glow this year, though whether that will be apparent to a visual observer when it’s this close to the sun is doubtful — and Saturn and Mercury are magnitudes 0.5 and -0.5 respectively.
ISON makes its closest approach to the sun, at about 700,000 miles, on November 28. You won’t be able to see the comet’s head then — but
if it’s grown a long tail, you might be able to see the tail rising before sunrise. I vividly remember a night in 1997 at the SJAA Messier Marathon at Coe — “What’s that glow over there? Is it headlights from a car driving on a road up in the hills?” “No, there’s way too much of it!” and the amazement as we gradually realized we were watching Hale-Bopp rising, forked tail first, over the Diablo range.
But the real ISON show is expected to happen in early December. By the middle of the month the comet should be visible in both morning and evening skies, and it’s anyone’s guess how bright it will be. I’ll cover more details of its December schedule next month, but for now, cross your fingers!
Okay, so you’re sick of hearing about the comet and you don’t want to get up that early anyway. What else is there to look at?
Try Jupiter! The gas giant rises at around 8:30 and is visible for the rest of the evening.
On November 5 there’s a nice multiple shadow transit. It starts during daylight, around 3:30, with Io’s shadow. By sunset (about 5:05), Io’s shadow, just about to exit the disk, has been joined by Europa’s shadow plus Io itself. Europa’s shadow exits the disk around 6:60, just about the time that Europa enters. Then there’s a very similar Io/Europa shadow event on the 12th, starting just before 5pm with Io’s shadow, with Europa’s shadow exiting around 9:20. And there are lots of single shadow transits, as well as single shadow plus single moon events — it’s a busy month for the Galilean moons!
Venus, too, is accessible in the evening sky all month., setting a little before 8 pm, going from roughly half phase at the beginning of the month to slightly crescent by November’s end. Uranus and Neptune transit near nightfall, so you’re best off catching them early in the evening. Pluto sets around 7 pm, so it’s really too low for observing this month.
Mercury, Mars and Saturn are all in the morning sky. On November 25, a couple of days after that nice ISON/Saturn/Mercury/Encke conjunction, Saturn and Mercury have a close conjunction, only about 20 arcminutes apart. That separation is only a little bigger than Saturn’s own disk.