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This Week's Sky at a Glance
Some daily events in the changing sky for October 1 – 9
by Alan M. MacRobert
Duringthe current dark-of-the-Moon period, Comet Hartley 2 passes south ofCassiopeia high in the evening sky. Click image for larger charts. Thecomet symbols are placed at 0:00 UT on the September and October datesindicated. Remember, 0:00 UT falls on the evening of the previous datein the times zones of the Americas.Sky & Telescope
Periodic Comet Hartley 2 should be about 7thmagnitude this week, visible in binoculars in a dark sky. It'sexcellently placed very high these moonless evenings, passing just southof Cassiopeia as shown at right. It's large and diffuse, meaning itslight is spread out over a wide area (as seen in binoculars) so you'llneed an unpolluted dark sky.
Hartley 2 may brighten to 5th magnitude in the next couple weeks. See the article in the October Sky & Telescope, page 56, or online.
Friday, October 1
At this time of year, fiveconstellations form a line descending from the zenith down to thewest-northwest horizon shortly after dark. Near the zenith is the starDeneb: the head star of the Northern Cross and the tail of Cygnus, theSwan. Next down is Lyra with bright Vega, then dim Hercules, then littleCorona Borealis, and finally Bootes with bright Arcturus low in thewest-northwest.Saturday, Oct. 2
Jupiter's Great Red Spotshould cross Jupiter's central meridian (the imaginary line down thecenter of the planet's disk from pole to pole) around 12:35 a.m. Sundaymorning Eastern Daylight Time; 9:35 p.m. Saturday evening PDT. The "red"spot appears very pale orange-tan. It should be visible for about anhour before and after in a good 4-inch telescope if the atmosphericseeing is sharp and steady. For all of the Red Spot's central-meridiancrossing times, good worldwide, use our Red Spot calculator or our list for the rest of this observing season.Sunday, October 3
The bright eclipsingvariable star Algol should be in one of its periodic dimmings, magnitude3.4 instead of its usual 2.1, for a couple hours centered on 10:28 p.m.EDT. Algol takes several additional hours to fade and to rebrighten.Use our comparison-star chart. For all times of Algol's minima, good worldwide, see the October Sky & Telescope, page 59, or use our Algol predictor.
Inthe dawn sky, the waning crescent Moon descends steeply day by day pastRegulus toward low Mercury. (The visibility of objects in brighttwilight is exaggerated here. The scene is drawn for the middle of NorthAmerica. European observers: move each Moon symbol a quarter of the waytoward the one for the previous date. The blue 10° scale is about thesize of your fist held at arm's length.)Sky & Telescope diagram
In the dark hours of Monday morning, October 4th,telescope users in most of the eastern and central U.S. can watch thewaning crescent Moon occult (cover) the 3.5-magnitude star OmicronLeonis near Regulus. The star disappears on the Moon's bright limb andreappears from behind its Earthlit dark limb. Map and local timetables of when the star disappears and reappears. The scene at right is later, in bright dawn — when Mercury has just risen.Monday, October 4
Mira is up. The brightestlong-period red variable star is visible to the unaided eye in Cetus.It was about magnitude 3.7 on September 27th, already at its predictedmaximum brightness a couple weeks early. Will it grow any brighter?Cetus is in good view in the east-southeast by about 11 p.m. daylightsaving time. See the comparison-star chart in the September Sky & Telescope, page 58. Jupiter's Red Spot should transit around 2:13 a.m. Tuesday morning EDT; 11:13 p.m. Monday evening PDT.Tuesday, October 5
Jupiter's Red Spot should transit around 10:04 p.m. EDT. In dawn tomorrow morning, a very thin crescent Moon is visible quite low in the east. Look about a half hour before your local time of sunrise. Mercury may also be detectable well to the Moon's lower left, as shown above. Bring binoculars!Wednesday, October 6
In the eastern eveningsky this month, look upper left of bright Jupiter for the Great Squareof Pegasus. Look farther to Jupiter's lower right for 1st-magnitudeFomalhaut. Algol should be at minimum light for a couple hours centered on 7:17 p.m. EDT.Thursday, October 7
New Moon (exact at 2:44 p.m. EDT). Jupiter's Red Spot should transit around 11:42 p.m. EDT.Friday, October 8
Spot Arcturus, thebrightest star of Bootes, low in the west-northwest as twilight fades.Look to its right in the north-northwest for the Big Dipper.Saturday, October 9
Jupiter's Red Spot should transit around 1:20 a.m. Sunday morning EDT; 10:20 p.m. Saturday evening PDT.
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