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This Week's Sky at a Glance
Some daily events in the changing sky for October 22 – 30.
by Alan M. MacRobert
Periodic Comet Hartley 2, though still nearly its closest toEarth, is pretty much lost in the moonlight this week. Moon-freeobserving times return around the morning of November 1st. On themorning of November 4th, NASA's EPOXI mission will fly by the comet'snucleus. See our article Comet Hartley 2 At Its Closest, with finder charts.
Now at naked-eye visibility, Mira in Cetus climbs the eastern sky in late evening — in this case, over hills in Iran.Babak A. TafreshiMira, the brightest long-period red variable star, shouldsoon start to fade from its unusually bright maximum. As of October19th observers were still reporting it at about magnitude 3.0, obviousto the unaided eye. Mira is up in good view in the east-southeast byabout 10 p.m. daylight saving time. Use the comparison-star chart in theSeptember Sky & Telescope, page 58.
Friday, October 22
Full Moon (exact at 9:37 p.m. Eastern Daylight Time). For telescope users, Jupiter's Great Red Spot should transit across theplanet's central meridian around 9:05 p.m. EDT. (Here's a list to printout of all the Great Red Spot's predicted transit times for the rest of this observing season.)Saturday, October 23
The tiny black shadows of both Ganymede and Europa fall on Jupiter's face from 9:40 to 11:04 p.m. EDT. By the time the double shadow transit ends on Jupiter, Algol in Perseusis just about at its minimum light. Its mid-eclipse is around 12:10a.m. Sunday morning Eastern Daylight Time; 9:10 p.m. Saturday eveningPacific Daylight Time. Algol remains nearly this dim for about an hourbefore and after.
Catchthe waning gibbous Moon passing through Taurus in early dawn. How welldo you know the waning Moon in your telescope? (The Moon is shown threetimes actual size for clarity. Its placement with respect to the starsis exact for the middle of North America.)Sky & Telescope diagramSunday, October 24
Step outside (or open awest-facing window) before dawn Monday morning, and there will be thewaning gibbous Moon with the Pleiades right nearby as shown here.Binoculars will continue to show the Pleiades and Aldebaran for a whileeven after dawn grows too bright for them to be visible to the nakedeye.Monday, October 25
At this time of year theBig Dipper lies level in the north-northwest after dusk, quite low, farbelow the bowl of the much dimmer Little Dipper.Tuesday, October 26
Algol is at minimum light for a couple hours centered on 8:59 p.m. EDT.Wednesday, October 27
By mid-evening,bright Capella is shining well up in the northeast. Look off to itsright, in the east, for the little Pleiades star cluster. Below thePleiades, by about a fist-width at arm's length, is the orange giantAldebaran.Thursday, October 28
The Ghost of Summer Suns.Halloween is approaching, and this means that Arcturus, the starsparkling low in the west-northwest in twilight, is taking on its roleas "the Ghost of Summer Suns." What does this mean? Every year forseveral days around October 29th, Arcturus occupies a special place inthe sky above your local landscape. It closely marks the spot therewhere the Sun stood at the same time (by the clock) during warmJune and July — in broad daylight, of course. So at this season everyyear, you can think of Arcturus as the chilly Halloween ghost of thedeparted summer Sun.Friday, October 29
Venus is at inferior conjunction, 6° south of the Sun and basically unobservable. The last-quarter Moon shines late tonight (it's exactly last-quarter at 8:46 a.m. Eastern Daylight Time Saturday morning).Saturday, October 30
The tiny black shadows of both Europa and Ganymede fall on Jupiter's face from 9:16 to 11:59 p.m. Pacific Daylight Time.
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