SkyEye

The Calendar

Three of the five bright planets are too close to the Sun to observe at the outset of 2020 but Venus dominates the western sky at sunset whilst fainter Mars is visible before dawn. The Moon undergoes four penumbral lunar eclipses this year, the first one on 10 January. And keep an eye on red Betelgeuse in the constellation of Orion. It has been dimming since last October and astronomers don't know why.

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 briefly a morning sky object but is low to the horizon at the beginning of the year and soon disappears from view. It undergoes superior conjunction on 10 January and reappears in the west after sunset late in the month. The nearly new Moon passes close by the tiny planet on 25 January.

Venus Capricornus → Aquarius

Venus ushers in the new year as the evening star. This apparition favours northern latitudes; although the planet is fairly low at this time, it will climb much higher over the next two months. However, observers in the southern hemisphere will not see Venus any higher in the west than it is now. Venus passes within 0.1° of Neptune on 27 January but a telescope will be required to spot the dim outer planet.

Earth and Moon

Perihelion and the Quadrantids always occur around the same time of year. In 2020, perihelion takes place on 5 January when Earth is 0.9832 au away from the Sun. As for the Quadrantid meteor shower which peaks the day before, the waxing gibbous Moon sets around midnight, leaving dark skies in the early morning hours. On 10 January, the Moon dips into Earth's penumbra, leading to a penumbral lunar eclipse, the first of four this year. Later, on 23 January, the waning crescent Moon occults Jupiter.

Mars Libra → Scorpius → Ophiuchus

The red planet is a morning sky object this month, rising an hour or so before the sky starts to brighten. The waning crescent Moon pays a visit on 20 January, coming within almost 2° of the planet. Mars is over 2 au away from Earth and shines at around magnitude +1.5.

Jupiter Sagittarius

Jupiter was at conjunction late last month so it is not visible during early January. However, it eventually appears in the morning sky ahead of the Sun and is occulted by waning crescent Moon on 23 January. This event begins just after midnight UT and is visible from Madagascar.

Saturn Sagittarius

The ringed planet is at conjunction on 13 January, actually passing behind the disk of the Sun as seen from Earth. This phenomenon is sometimes referred to as an anti-transit or secondary eclipse. Because it is so close to the Sun mid-month, Saturn is largely unobservable in January but appears in the east before sunrise next month.

Uranus Aries

Uranus enters the year backwards, moving in retrograde motion across the sky. However, it reaches a stationary point on 11 January and resumes direct motion. Two days before that, the distant green planet reaches its maximum declination south for the year (+11.8°). On 23 January, Uranus reaches quadrature, the point where it is 90° away from the Sun as seen from Earth. Look for this sixth-magnitude object in the evening after the skies are dark.

Neptune Aquarius

A small telescope is necessary to view the most distant planet in the solar system. Like its neighbour Uranus, Neptune is an evening sky object and sets before midnight. On 27 January, Neptune is found in close proximity with brilliant Venus, with the two objects less than 0.1° apart. However, only Venus is visible to the naked eye.