SKY REPORTER: October 2012 main content.

SKY REPORTER: October 2012

by Steve Beyer on

Hayden Planetarium Blog

Sky Data

Monday October first, sunrise is at 6:53 a.m. Eastern Daylight Time. That evening the Sun, located in the constellation Virgo, sets at 6:37 p.m.

Monday October 15 sunrise is at 7:07 and sunset occurs that day at 6:15 p.m.

The last day of this month Wednesday the 31th, the Sun is in Libra rising at 7:25 a.m. and setting at 5:53 that evening. During October the daily duration of daylight decreases by one hour and 17 minutes. The altitude of the Sun at solar noon descends during October from 46 degrees of arc on the first to 35 degrees on the 31st.

Average overnight temperatures recorded in Central Park during October drop from 55 degrees Fahrenheit on the first to 46 degrees on the last day of the month.

Principal Phases of the Moon are:

Last Quarter October 8
New Moon October 15
First Quarter October 21
Full Moon October 29

Sky Cast

The expressions “morning star” and “evening star” don’t refer to actual stars such as Vega or Sirius, but instead are traditional descriptions for planets that are above the horizon at either sunrise or sunset on a particular date.

On October first, Jupiter and Venus are the morning stars, and evening stars are Mercury, Mars, Saturn, Uranus, and Neptune. On that date Mercury sets during dusk at 7:10 pm, 33 minutes after sunset. The waning gibbous Moon, with its disk 97% illuminated and generally indistinguishable to casual observers from the Full Moon two days earlier, rises at 7:12 p.m. Saturn drops beneath the western horizon at 7:35, followed by Mars at 8:36. Jupiter rises at 9:47 p.m. Early the following morning, Venus rises at 3:23 a.m. Neptune sets at 3:44 a.m. and Uranus dips beneath the horizon at 6:44, shortly before sunrise.

Hubble eXtreme Deep Field
Hubble eXtreme Deep Field project (XDF) image.
Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team

During the last week of September, an image showing the furthest view of the Universe ever seen was released by NASA. It depicts about 5,500 galaxies including many that formed 13.2 billion years ago, relatively soon after the origin of the Universe in the Big Bang.

Thursday October 4, at about 3:30 a.m., the Moon is just south of the beautiful Pleiades open star cluster in the constellation Taurus. Following an imaginary line from that cluster past the Moon, onward toward the south point of the horizon, brings you past fourth magnitude star Tau4 in the constellation Eridanus then by third magnitude Acamar in Fornax. A minute portion of sky (about the apparent size as the Moon’s Mare Crisium when seen from Earth) is located about four and a half degrees of arc from Acamar, seven degrees from Tau4, and 22 degrees above the horizon. It marks the area portrayed in NASA’s digital picture, that was produced by stacking more than 2,000 separate images taken at various times over the past ten years, then assembled by the Hubble eXtreme Deep Field (XDF) project. Two Hubble cameras: the Advanced Camera for Surveys and the Wide Field Camera 3, sensitive to near-infrared light, were used in this endeavor.

As days of autumn pass, the site of the XDF image arrives at its location over the south horizon point about a half hour earlier with each passing week.

The nights of Thursday October 4 and Friday the 5th, the waning Moon is near Jupiter between the horns of Taurus. For those who have never had the experience of pointing to that giant planet, these proximities provide good guidance for having that experience.

Jupiter and its Moons Composite
Composite image with Jupiter shown with moons (from top) Io, Europa, Ganymede, and Callisto.

The great planet with its four largest moons: Io, Europa, Ganymede, and Callisto, is one of the finest sights in any telescope, and these objects are sufficiently bright to hold their own against the glare of nearby moonlight. At eleven p.m. on the evening of October 4, the Jovian moons are arrayed with Callisto and Io to the east of Jupiter’s disk with Europa and Ganymede to the west (the side of Jupiter nearest the Moon that night). The following evening at the same time, we may see that the Moon is then to the east (left) of Jupiter. A telescope will show that the Jovian moons have moved noticeably in the span of just one day. On the night of the 5th, relatively slow moving Callisto remains quite far to the east of the planet, but Europa, rather than Io, is now to the east of Jupiter’s disk. Ganymede remains to the west having been joined on that side of the planet by fast orbiting Io, located further westward from the disk.

The four largest moons of Jupiter were among the first astounding sights that greeted the eyes of Galileo after he turned his little 20 magnification telescope to the sky late in 1609. Io and Europa are about the same size as Earth’s Moon, while Ganymede (the Solar System’s largest satellite), and slightly smaller Callisto are about one and a half times the Moon’s diameter.

Early on the morning of Friday October 12, the thin 11% illuminated waning crescent Moon is above the east-southeastern horizon, six degrees to the right of Venus.

At the end of civil twilight about 6:45 p.m. on the evening of Wednesday October 17, the thin two day old waxing crescent Moon may be seen ten degrees of arc above the southwestern horizon, and ten degrees to the lower right of Mars, which shines in the constellation Scorpius with magnitude 1.24.

Saturday October 20 at about seven p.m., the waxing crescent Moon is in Sagittarius five degrees of arc to the east (left) of the dwarf planet Pluto, which has visual magnitude 14.

The evenings of October 24 and 25 the waxing gibbous Moon is about 25 degrees of arc north of first magnitude star Fomalhaut located in the constellation Piscis Austrinus.

On the last day of October, the morning stars are Venus and Saturn, with evening stars being Mercury, Mars, Jupiter, Neptune, and Uranus. During the evening twilight of Halloween, Mercury sets at 6:46 p.m. The 96% illuminated waning gibbous Moon rises at 7:02 p.m. and Mars sets at 7:54, followed beneath the western horizon by Neptune at 12:44 a.m. Venus rises at 4:27a.m., Uranus sets at 4:40, and Saturn rises at 6:55 just before the Sun appears above the horizon.

Sky Lore

Fomalhaut is not only the brightest star in Piscis Austrinus, it is the brightest star in a large portion of the southern sky seen during evenings of October. Located about 70 degrees from the Galactic equator, Fomalhaut is significantly south of concentrated dust and gas in the Milky Way’s plane, location of the Galaxy’s most active star formation sites. Piscis Austrinus, representing the Southern Fish, is part of a sky region featuring a number of constellations with watery associations including Aquarius, and Cetus, the Sea Creature.

The mouth of the Southern Fish is represented by Fomalhaut, sometimes depicted in classic star atlases as catching water spilling from the jar of Aquarius. These aquatic constellations are traditionally known as part of the Celestial Sea, a designation suggested by the presence of the Sun among these stars during the northern hemisphere’s spring season, when melting snows fill waterways with above average flows.