Step out early in the morning to see a fine show in the eastern sky.
October's sky highlight is a spectacular dawn grouping of Venus, Saturn and Regulus — visited by the crescent Moon at just the right time. At dusk, Jupiter is sinking low in the southwest. And Mars is a brightening fire rising later in the night. Read on!
Evening
Mercury sinks out of visibility into the Sun's afterglow in the opening days of October for observers at mid-northern latitudes. Viewers around 35° south latitude find Mercury much higher and can follow it until it gets too faint in mid-October. The little planet passes through
inferior conjunction (between Earth and the Sun) on October 23rd, then enters the morning sky.
Jupiter still shines at magnitude -2.0 but is getting quite low in the southwest at nightfall. By October's end the giant planet sets less than an hour after dark. Antares, Jupiter's summertime companion, sinks away even faster to Jupiter's lower right. The Moon pays the pair a visit on October 15th but passes more than 5° south of the planet.
Pluto is also getting lost in evening twilight.
Neptune is highest in the south not long after dark, and Uranus is there about 1½ hours after Neptune. Finder charts for both planets appear on page 60 of the
July issue of
Sky & Telescope.
Late NightMars is the bright, pumpkin-colored point of light lifting up from the northeastern horizon in late evening — but earlier and earlier each week. Observers at mid-northern latitudes can see it rise as early as 9:30 p.m. daylight-saving time by October 31st.
Mars starts the month entering Gemini from Taurus. Early on the morning of October 1st for the Americas, it passes a mere 7′ north of the 4th-magnitude star 1 Geminorum. In the next few days Mars glides about 1° south of the impressive star cluster Messier 35, visible in binoculars. By late October Mars is slowing its direct (eastward) motion relative to the stars.
How bright is Mars this month? It swells from magnitude -0.1 to -0.6 by October's end, outshining all the winter stars save Sirius. How big does Mars appear in telescopes? It enlarges from 10″ to 12″ wide, big enough that you may start seeing surface features in a relatively modest telescope — once Mars gets far above the horizon on a night of good atmospheric "seeing" (stability). The planet is very high in the south just before the start of morning twilight; this is the best time to look.
Dawn
Venus in October is the highest it ever gets in the dawn sky, about 30° up in the southeast an hour before sunrise for watchers at mid-northern latitudes.
The lamp-like planet attains its greatest elongation (separated from the Sun by 46°) on October 28th. Do you see Venus in the telescope exactly half-illuminated that day, or a few days before or after? By the time of greatest elongation this brightly cloud-shrouded world has shrunk down to 24″ across.
Saturn, near Venus before and during dawn, is noticeably dimmer than usual (magnitude +0.8) because its rings have now closed to less than 10° from edgewise for the first time in 10 years. All that matters this month, however, is Saturn's marvelous positioning in relation to Venus and Regulus, the brightest star in Leo, the Lion.
On the morning of October 5th, Saturn is 7½° to the lower left of Venus, and Regulus is about 4° from both planets (a little above the midpoint of the line connecting the two). But the grouping is still contracting. On the 6th, the waning Moon hangs not far above these three lights. Then, several hours before sunrise in the Americas on October 7th, Venus, Saturn, and Regulus rise in a triangle that's only 6° long and very thin — with the crescent Moon inside it!
On October 8th and 9th the Moon appears well below the planet-star bunching, but the gap between Venus and Regulus becomes smallest, about 2¾°. Venus, Saturn, and Regulus make an official "trio" — that is, three celestial objects fitting within a circle just 5° wide — from October 9th through 13th. The trio is at its most compact, with all three within 4.6° of one another, on the 10th.
Will you be watching the sky this month?
Venus comes to within 3° of Saturn on the 14th and 15th, then starts dropping away from it as Saturn moves higher. By the end of October, Saturn is almost 15° to the upper right of Venus and 6½° to the lower left of Regulus.
Moon PhasesLast quarter: Oct. 3, 6:06 a.m. EDT
New Moon: Oct. 11, 1:01 a.m. EDT
First quarter: Oct. 19, 4:33 a.m. EDT
Full Moon: Oct. 26, 12:52 a.m. EDT
Other Sky HighlightsOct. 1: Mars is less than 7′ north of 1 Geminorum 1 to 4 a.m. EDT.
Oct. 3-4: Mars passes less than 1° south of the star cluster M35 in Gemini. The best views are before dawn. Use binoculars.
Oct. 5: The Moon is roughly 1° north of the Beehive Cluster (M44) before dawn.
Oct. 7: The thin crescent Moon shines amid Venus, Saturn, and Regulus in early dawn; see page xx. The Moon occults Regulus before dawn for Western Europe and Morocco, after sunrise for the rest of Europe and the Middle East.
Oct. 15: The Moon forms a compact triangle with Jupiter and Antares at dusk in North America. The Moon occults Antares as seen from Antarctica and passes {1/2}° north of the star in South Africa.
Oct. 20-22: The Orionid
meteor shower peaks on the 21st, but activity should be strong for several nights. Observers at dark sites may see up to 20 meteors per hour after 2 or 3 a.m., when the radiant is high in the sky.
Oct. 25-26: The Moon is it's closest to Earth for the year at 7:52 a.m. EDT. So tonight's
full Moon is the largest of 2007.
Oct. 27: The Moon occults the Pleiades star cluster for Europe and easternmost North America.
© 2007 Reprinted with permission from Sky Publishing Corp.
