The top sights to observe or image this month
DON’T MISS: Quadrantid meteors
BEST TIME TO SEE: 3/4 January
EQUIPMENT: Naked eye
The Quadrantid meteor shower heralds the start of the New Year’s meteor activity. It is a high-rate shower with a typical peak ZHR (zenithal hourly rate) of 120 meteors per hour, which has been known to vary between 60–200 meteors per hour. Despite the cold, if the sky is clear on the evening of the 3rd, it is well worth putting in the effort as the Quadrantid meteor shower can deliver a fantastic display.
The radiant is located in a region of sky which used to be known as Quadrans Muralis (the Mural Quadrant), which is how the shower gets its name, but Quadrans Muralis is no longer recognised as one of the 88 official constellations.
The radiant location is in the region bounded by Draco, Boötes and Hercules. The Plough asterism is a handy tool for imaging where the radiant is during peak activity. Extend the line from Megrez (Delta (δ) Ursae Majoris) through Mizar (Zeta (ξ) Ursae Majoris) for 1.5x that distance again and you’ll be in the general vicinity of the radiant.
In case you struggle identifying Greek-lettered stars, the stars in the Plough are lettered in sequence starting at the west through to the east (at the end of the Plough’s handle). As long as you know the first seven Greek letters, α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon), ξ (zeta) and η (eta), you should be able to locate the stars we mentioned quite easily.
The Quadrantids are expected to reach peak activity around 20:40 UT on 3 January. This represents the period when Earth will be passing through the densest part of the Quadrantid stream. Unfortunately, the radiant will only be around 8˚ up at this time. A usual Quadrantid shower shows heightened activity for a few hours either side of the peak. The rates will begin to drop off as we head into the morning of the 4th, but the increasing altitude of the radiant should help to compensate to a degree, keeping things interesting through to dawn.
The Moon will be new on the evening of 2 January, which means that on the night of the Quadrantid peak it will not interfere. You will need to find a dark unobstructed observing site and plan to observe in periods no shorter than 30 minutes. Allow your eyes at least 20 minutes in darkness to become dark adapted. A garden recliner makes a great observing platform, but don’t forget to wrap up warm!
Comet C/2019 L3 Atlas
BEST TIME TO SEE: All month; best at the start and end of January when the Moon is absent
EQUIPMENT: Small/medium telescope
Comet C/2019 L3 Atlas is well placed in January. Reaching perihelion on the 10th, it is expected to reach mag. +9.7, making it a viable target for larger binoculars or a small scope. L3 Atlas was discovered by the ATLAS (Asteroid Terrestrial-impact Last Alert System) facility at Haleakala, Hawaii on 10 June 2019. Around 18th magnitude, it has brightened since then. It is located in the constellation of Gemini, tracking along the northern edge of the stick figure representing the body of the twin Castor.
In terms of brightness, C/2019 L3 Atlas is expected to stay at mag. +9.7 for the first half of the month, dropping a tenth of a magnitude during the second half. If the sky is clear and the Moon is out of the way, it should be easy to keep tabs on.
At January’s start, the comet is 3˚ north of mag. +4.4 Tau (τ) Geminorum, midway between mag. +1.9 Castor (Alpha (α) Geminorum) and mag. +3.4 Theta (θ) Geminorum. It follows a curving path southwest, ending the month 2˚ north of Mebsuta (Epsilon (ε) Geminorum). The full track length over the month is around 10˚.
Slightly brighter than 10th magnitude, L3 Atlas will make a great imaging target for wide-field and close-up study. C/2019 L3 Atlas isn’t the only bright comet. 19P Borrelly is moving northeast as it approaches perihelion on 2 February.
Lunar occultation of Zubenelgenubi
BEST TIME TO SEE: 26 January, from 05:10 UT until 06:50 UT
EQUIPMENT: Small/medium telescope
The 42%-lit waning crescent Moon will pass in front of the star Zubenelgenubi (Alpha (α) Librae) on the morning of 26 January, an event known as a lunar occultation. Bright star occultations aren’t rare but are uncommon enough to make them worth putting in a bit of effort to see. In this case there’s a hidden bonus because Zubenelgenubi is a double star with both components visible to the naked eye.
The two components are mag. +5.1 Apha-1 and mag. +2.8 Alpha-2. The name Zubenelgenubi, which means ‘Southern Claw’, applies to the brighter component, Alpha-2. They lie at the same distance of 77 lightyears and both have similar velocity and direction in space. As a consequence, they are very likely to be a physical pair.
From the centre of the UK, the Moon’s bright limb will hide Alpha-1 at 05:25 UT, Alpha-2 following suit nine minutes later at 05:34 UT. Alpha-1 reappears from behind the Moon’s dark limb at 06:35 UT, Alpha-2 reappearing at 06:43 UT. Dawn will be well underway as the reappearance occurs but both stars are bright enough to remain visible for the event. Times will vary slightly depending on your location so it pays to observe starting, say, 15 minutes before the quoted disappearance and reappearance times.