SkyEye

The Calendar

Mars reaches its minimum distance from Earth and opposition a week apart in early December. Observations of the Geminid meteor shower are severely hampered by moonlight this year.

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 Ophiuchus → Sagittarius

Although Ophiuchus is not a member of the zodiac, the ecliptic passes through it.

Mercury Ophiuchus → Sagittarius

Found in evening twilight low in the southwest, Mercury attains greatest elongation east on 21 December and joins Venus one final time this year on 29 December when the two planets are 1.4° apart.

Venus Ophiuchus → Sagittarius

Venus meets Mercury for the third and final time this year on 29 December when the two planets are 1.4° apart in the west after sunset. The evening star is slowly gaining altitude, rising more quickly for southern hemisphere observers than those in the north.

Earth and Moon

The Phoenicids are not too inconvenienced by moonlight this year but the Puppid-Velids and Geminids are seriously compromised. However, the last major shower of the year, the Ursids, rejoice in dark skies. The Moon occults both Uranus (5 December) and Mars (8 December). Earth reaches it second solstice in this year on 21 December. The word solstice means 'sun stands still' so that on this day, the solar declination reaches an extreme. In this case, the Sun appears directly over the Tropic of Capricorn in the southern hemisphere.

Mars Taurus

Mars makes it closest approach to Earth on the first day of the month, with opposition occurring one week later. At the time of opposition, Mars is a blazing magnitude −1.9 and appears 17.3 arc-seconds wide in a telescope. On the same day, the red planet is occulted by the Full Moon in an event beginning at approximately 03:30 UT and visible across much of North America, Greenland, Iceland, western Europe and northwestern Africa. Mars experiences an equinox on 26 December, with spring coming to the Martian northern hemisphere and autumn to the south.

Jupiter Pisces

The largest planet in the solar system achieves east quadrature — a position 90° away from the Sun — on 22 December. This is an excellent time to observe the planet and its major satellites through a telescope; the shadows are cast somewhat off to the side, leading to some interesting visual effects. Jupiter ends the year as it started, as evening sky object. It sets around midnight for astronomers in northern temperate latitudes but somewhat earlier for observers in the southern hemisphere.

Saturn Capricornus

Visible after sunset, first-magnitude Saturn vanishes in the west by mid-evening.

Uranus Aries

The fifth of the month ushers in the last lunar occultation this year of Uranus. Beginning around 15:30 UT, planet watchers in northern Africa, northern parts of the Middle East, Europe and northern Asia will see the waxing gibbous Moon pass in front of the sixth-magnitude planet.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Northern hemisphere planet chasers have slightly longer to observe this elusive object than those in southern latitudes, with Neptune setting around midnight as seen from northern temperate regions. The planet reverses course and resumes direct motion in early December; it reaches east quadrature on 14 December.