October sky yields top view of Mercury

Focus on the planets

Mercury aficionados are in for a treat during October. Starting Oct. 27 and lasting for 11 days, Mercury and Venus will be within one degree of each other on the predawn eastern horizon. This rare sight is well worth getting up an hour early to check out.

Venus, besides its near conjunction with Mercury at the end of the month, keeps company with the crescent moon at midmonth. Look for Venus in the east about an hour before sunrise.

Mars is rapidly fading as Earth outdistances its slower neighbor, but details of the Martian surface can still be seen through a telescope. Look for the red planet high on the southern horizon about an hour after sunset.

Jupiter is best viewed on the southern horizon during the pre-dawn hours this month. The giant planet is steadily brightening and, around Oct. 7, is positioned so that details of its moons and swirling surface are easily viewed by telescope.

Saturn is well to the upper right of Jupiter on the southwestern horizon before dawn. Saturn maintains a highly favorable tilt for viewing its spectacular ring system.

Uranus and Neptune are high in the south during the early evening hours nestled among the stars of Capricornus. Both are visible through a moderately powerful telescope.

Pluto is not visible during October.

Our celestial neighborhood

Saturn is the sixth planet from the sun, with a year equal to 29.5 Earth years. Saturn’s fabled ring system makes it the most instantly recognizable planet in the solar system. Voyager 2 sent back closeup pictures of the rings in 1981, when it spent days passing through the countless millions of bits of dust and rocks miraculously without suffering any damage.

But it is not Saturn’s rings that hold scientists’ interest. The ringed planet has 18 major satellites and one of them, Titan, is thought to have one of the best chances, besides Earth, to harbor life in the solar system. Voyager 2 showed that Titan has a thick atmosphere consisting of nitrogen in the form of ammonia, and several hydrocarbons such as methane, ethane, and acetylene.

One of the ways life is theorized to have started is by the reaction of ammonia with hydrocarbons to yield molecules that are precursors to simple life. There is also evidence of water at Titan’s surface and data sent to Earth in 1994 by the Hubble Space Telescope hints at the presence of oceans. Whether any of these circumstances translated into the formation of life is a question astronomers hope to answer with probes to the satellite in the future.

October events

1 Sunrise, 6:33 a.m.; sunset, 6:17 p.m.

2 Full moon, 9:50 a.m. October’s full moon, being the one nearest to the fall equinox, is the harvest moon.

6 The moon shines above Aldebaran tonight, with Saturn to the moon’s lower left.

10 Moon in last quarter, 12:20 a.m.

14 Look for the nearly new moon above Venus in the predawn, with Denebola directly to the moon’s left.

16 New moon, 3:23 p.m.

21 This the peak night for the Orionid meteor shower. Halley’s comet is the source of this shower of very fast meteors that often leave a persistent trail. As the name suggests, the shower originates out of Orion with a variable rate of 10 to 15 sightings per hour.

23 Look for the moon to the immediate lower left of Mars about an hour after sunset. The sun enters the astrological sign of Scorpio but astronomically is still in Virgo.

24 Moon in first quarter, 10:57 p.m.

28 Don’t forget to set your clocks back an hour tonight as we go on to Standard Time for the winter months.

29 Look for Mercury and Venus extremely close together on the east-southeast horizon about an hour before sunrise. Spica is to their lower right.

30 The sun enters Libra on the ecliptic.

31 Halloween, the eve of All Saint’s Day, is a cross-quarter day marking the midpoint between the fall equinox and winter solstice. A full moon occurs 42 minutes after midnight tonight and some references place it in October rather than November. If so, it would be the second full moon of the month and hence a blue moon. Sunrise, 6:12 a.m.; sunset, 4:26 p.m.