SkyEye

The Calendar

Earth is at perihelion on the second day of the year. Moonlight hampers observations of the first meteor shower of 2021 and both Jupiter and Saturn disappear from view.

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 Sagittarius → Capricornus

Mercury Sagittarius → Capricornus

Mercury is low in the southwest at the beginning of January. It appears a little higher every evening at sunset for most of the month in what is a fair apparition for both hemispheres. However, southern hemisphere observers will have a slightly better chance of seeing Mercury near Saturn (10 January) and Jupiter (11 January). The very young Moon is just over 2° south of the tiny planet on 14 January but our satellite may be too close to the Sun to be visible. Mercury reaches greatest elongation east (only 18.6°) on 24 January and goes through its first perihelion of the year on 29 January. Retrograde motion begins the following day. Mercury is brightest at the beginning of the year but fades but fades two magnitudes to end up at +1.0 at the end of January.

Venus Ophiuchus → Sagittarius

The year opens with Venus in the east at sunrise, shining at magnitude −3.9 and appearing in its waxing gibbous phase when viewed through a telescope. It is already fairly low as seen from northern temperate latitudes but is somewhat higher when observed from the southern hemisphere. It slowly loses altitude throughout the month. The waning crescent Moon passes just 1.5° south of the morning star on 11 January.

Earth and Moon

Perihelion, that point when Earth is nearest to the Sun, occurs very early this year, on 2 January. The first meteor shower of the year, the Quadrantids, peaks shortly thereafter, but the light of the waning gibbous Moon seriously interferes with observations.

Mars Pisces → Aries

Mars begins the year at magnitude −0.2 in the evening sky. It passes 1.6° north of sixth-magnitude Uranus on 20 January. Planet watchers in the northern hemisphere have the best views of the red planet this month.

Jupiter Capricornus

With Jupiter at conjunction on 29 January, the beginning of the new year sees the gas giant very low in the west at sunset. Its close encounter with Mercury on 11 January may be lost in the glow of the sunset sky.

Saturn Capricornus

Saturn is missing during the first few weeks of 2021, hidden in the glare of the Sun as the ringed planet undergoes conjunction on 24 January. Its appearance next to Mercury on the tenth is unobservable. Look for Saturn in the morning late next month.

Uranus Aries

Uranus spends the first two weeks of January going backwards before reaching a stationary point on the fourteenth and returning to direct motion. Two days before that, however, the planet reaches its most southerly declination of the year. Uranus and Mars are 1.6° apart on 20 January but moonlight may make it difficult to spot the sixth-magnitude planet with the naked eye. East quadrature occurs on 26 January. Northern hemisphere observers get the best views, with Uranus not setting until after midnight.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Neptune is visible in the evening this month and is best viewed from northern latitudes. Choose a moonless night and look for it in the west.