In a bizarre twist of events, Pluto, which recently lost its status as a planet, has been downgraded to No. 134340 in the asteroid belt by the Minor Planet Center while the object, called 2003 UB313, which led to Pluto’s planetary demise, has been given the name Eris after the Greek goddess of chaos and strife. Eris’ satellite, a tiny moon about 190 miles in diameter, has been named Dysnomia after a Greek spirit of lawlessness.
Pluto lies in the Kuiper belt beyond the orbit of Neptune while Eris is even farther away in what is called the “scattered disk.” Eris is a bit bigger than Pluto, and its time of orbit about the sun is 557 years compared to 248 years for Pluto. It probably made sense to strip Pluto of its planetary status so that Eris, Ceres and a host of other objects would not have to be upgraded to planets. Yet, for those who still harbor a fondness for the old nine-planet system, the name chosen for this interloper seems somehow appropriate.
Focus on the planets
Mercury is very low on the western horizon and sets soon after sunset making October a poor month to view the innermost planet. The best time to view Mercury will be around Oct. 20 when it lies just below, and slightly to the right of, Jupiter about a half-hour after sunset.
Venus peeks above the eastern horizon just before sunrise as the month opens but, in a few days, vanishes to reappear in the evening sky at year’s end.
Mars is lost in the sun’s glare all month and will just begin to be visible in the morning sky as the year draws to a close.
Jupiter opens the month low in west and continues to sink toward the horizon as October passes. The Earth’s atmospheric turbulence will prevent viewers with telescopes from seeing many of the giant planet’s features.
Saturn rises in the northeast around 3 a.m. as October opens and a favorable tilt to its ring system plus the presence of dozens of moons, highlighted by Titan, make the ringed planet a treat for viewers with even small telescopes. On Oct. 16, look for Saturn high in the east-northeast about an hour before sunrise in the company of a waning crescent moon.
Uranus is high in the southeast by late evening where its blue-green color is distinctive among the stars of Aquarius.
Neptune lies well up on the southern horizon, a bluish disk among the stars of Capricornus. Both of these far distant planets are visible with a small telescope.
1 Sunrise, 6:33 a.m.; sunset, 6:17 p.m.
2 Jupiter shines in solitary splendor in the southwest about an hour after sunset. The reddish star well to Jupiter’s upper left is Antares.
6 Moon at perigee, or closest approach to the Earth, today. With the full moon occurring within 12 hours of perigee, look for abnormally high tides.
7 Full moon, 12:13 p.m. As the full moon nearest the fall equinox, the full moon of October is the harvest moon this year.
9 If you are up around midnight, you will be able to watch the waning gibbous moon passing in front of the Pleiades star cluster temporarily covering or occulting most of it.
14 Moon in last quarter, 8:26 p.m.
19 Moon at apogee, or farthest distance from Earth, tonight.
21 Tonight is the peak night for the Orionid meteor shower derived from comet Halley. Look for up to 20 meteors an hour originating in the tip of Orion’s club. Typical Orionids are swift, bright, and often leave persistent trails. The nearly new moon greatly aids viewing.
22 New moon, 1:13 a.m.
23 The sun enters the astrological sign of Scorpio but astronomically is still in Virgo.
24 The thin crescent moon lies just above the southwest horizon a half-hour after sunset with Jupiter to its right and Mercury to the latter’s lower left.
29 Moon in first quarter, 4:25 p.m. Last Sunday in October so don’t forget to set your clocks back an hour as we return to Standard Time.
31 Halloween or All Hallow Eve, the cross-quarter daymarking the midpoint between the fall equinox and winter solstice. The sun enters Libra on the ecliptic. Sunrise, 6:12 a.m.; sunset, 4:26 p.m.
Clair Wood taught physics and chemistry for more than a decade at Eastern Maine Technical College. He can be reached at email@example.com.