SkyEye

The Calendar

Mercury's best morning apparition for observers in northern temperate latitudes is underway this month and a partial solar eclipse takes place on 25 October.

The Solar System

The word planet is derived from the Greek word for 'wanderer'. Unlike the background stars, planets seem to move around the sky, keeping mostly to a narrow track called the ecliptic, the path of the Sun across the stars. Dwarf planets and small solar-system bodies, including comets, are not so constrained, often moving far above or below the ecliptic.

Sun Virgo → Libra

Mercury Virgo

Mercury returns to direct motion on the first day of the month. Now visible at dawn, this is the best morning apparition for northern temperate latitudes and a very poor appearance for observers in the southern hemisphere. The last perihelion of the year takes place on 6 October and greatest elongation west occurs two days later. The New Moon occults Mercury just before the partial solar eclipse on 25 October but the event will likely be unobservable.

Venus Virgo → Libra

The morning star finally vanishes from the dawn skies in early October, with Venus undergoing superior conjunction on 22 October. It is occulted by the New Moon just minutes after the partial solar eclipse of 25 October concludes.

Earth and Moon

The Draconids are largely spoiled by the moonlight of the Full Moon. The Orionids later in the month suffer from far less interference. The Moon occults three planets this month, Uranus on 12 October, Mercury on 24 October and Venus on 25 October, the same day as a partial solar eclipse.

Mars Taurus

Mars crosses its ascending node on 20 October, moving to the northern side of the ecliptic. Ten days later it reaches a stationary point in right ascension and begins retrograde motion. Mars is best viewed from the northern hemisphere where it rises mid-evening. Astronomers in the southern hemisphere must wait until nearly midnight before the red planet puts in an appearance in the east.

Jupiter Pisces

Now primarily an evening sky object, bright Jupiter is best viewed from northern latitudes where it doesn't set until well after midnight.

Saturn Capricornus

Saturn returns to direct motion this month, having entered into retrograde four and a half months earlier. It is visible in the skies after sunset and is best viewed from the southern hemisphere where it sets after midnight.

Uranus Aries

Now rising in early evening, Uranus is occulted by the waning gibbous Moon on 12 October. Astronomers in northern and western North America, northeastern Russia, Greenland and Iceland can witness this event beginning around 04:30 UT.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Neptune is already above the horizon when the Sun sets, not vanishing in the west until well after midnight. Look for it on a moonless night as it is never brighter than eighth magnitude.