The Planets
Venus
Best time to see: 31 January, from 06:00 UT Altitude: 5º (low) Location: Ophiuchus Direction: Southeast Features: Phase, subtle disc shadings Equipment: 75mm or larger
Venus is currently a morning planet shining brighter than mag. –4.0 all month. On the mornings of 1 and 2 January the planet’s naked-eye appearance will be enhanced by the presence of a waning crescent Moon. On New Year’s morning the Moon will be 21% lit and appear to the west-northwest of the planet – that’s above and right as seen from the UK. The following morning, the now 13% lit, waning crescent Moon swaps sides to lie to the east-southeast of Venus. The separation of about 4.3° will make for a particularly attractive sight on 2 January. As the dawn sky brightens so Venus and the Moon will be joined by mag. –1.6 Jupiter and then mag. –0.4 Mercury.
Through a telescope Venus currently appears close to half lit. According to calculations, Venus should appear perfectly 50% illuminated on the day of its greatest western elongation, which is 6 January. However, owing to an effect known as the phase anomaly when Venus is in the morning sky, it appears that this event happens late by a few days. Phase anomaly is thought to be due to
Mathematically, Venus will be half-lit on 6 January, but in practice it may not appear that way, because of an atmospheric effect
the way sunlight scatters in the planet’s atmosphere. Record your own estimates of the phase by imaging or sketching Venus through a telescope over the days running up to and from greatest western elongation, to pinpoint when you think the planet looks exactly half-lit. Later in the month, look out for a close encounter between Venus and mag. –1.7 Jupiter. On 23 January both planets appear separated by just 2.5°,
and should be a stunning sight low in the southeast as they rise around 05:00 UT. As the pair separate over the following mornings, there’s an additional point of interest on the very last day of the month when an 18%-lit waning lunar crescent once again joins the scene and appears to lie between both planets.