The top sights to observe or image this month
DON’T MISS: The Lyrids 2022
BEST TIME TO SEE: 22–26 April, peak on the night of 22/23 April
The annual meteor calendar starts with a bang as Earth experiences the Quadrantid meteor shower at the start of January. However, in the weeks that follow, activity is restricted to very weak showers and the background ‘noise’ of sporadic meteors, that is until April when the Lyrid shower raises the game once again.
Lyrids occur when Earth passes through the debris spread around the orbit of comet C/1861 G1 Thatcher. Activity typically begins on 16 April and continues through to the 25th. For most of this period, meteor rates are quite low in activity, reaching a peak on the night of 22/23 April, when a zenithal hourly rate of 18 meteors per hour can be expected.
A shower’s zenithal hourly rate (ZHR) can be misleading. Quoted as the number of meteors expected to occur over an hourly period, the figure is adjusted to assume perfect conditions and the shower’s radiant position – the area of sky where the shower trails appear to emanate from – directly overhead. In practice, hardly any of the conditions required to witness the ZHR figure are met and the resulting visual hourly rate tends to be significantly lower.
On 23 April, the last quarter Moon won’t hinder the view of the Lyrids
This year, Earth will pass through the densest part of the Lyrid stream at 20:00 BST (19:00 UT) on the 22nd. At this time the Lyrid radiant, located near Vega (Alpha (α) Lyrae), will be low, which isn’t ideal. As the night progresses the radiant’s altitude increases, which helps matters.
The Moon will be at last quarter on the morning of 23 April, but because it’s spring the angle made by the ecliptic with the eastern horizon in the run-up to dawn is shallow. As a consequence, the Moon won’t really interfere, rising as dawn is well underway. This would normally mark the end of a meteor watch anyway, so for 2022 at least, the Moon will not be an issue.
To observe the Lyrids, find a place away from any stray lights. Give yourself at least 20 minutes in total darkness for your eyes to dark adapt and thereafter, avoid looking at bright light sources such as a mobile phone. Stare up at an angle of about 60˚, two-thirds the way up the sky from horizon to zenith. Any direction will do, so choose the one in which the sky looks darkest. A garden recliner is a comfortable viewing platform. Aim to observe for periods of at least 30–60 minutes between short breaks.
Morning conjunctions
BEST TIME TO SEE: 5 April for Mars and Saturn, from 27 April for Venus and Jupiter
At April’s start, mag. –4.2 Venus rises above the east-southeast horizon, 80 minutes before sunrise. The bright planet lies near to mag. +0.9 Saturn and +1.1 Mars. This dimmer pair appears southwest (right, as seen from the UK) of Venus in the dawn twilight.
As the mornings pass, Venus heads east, leaving the group. On the morning of 5 April, Mars and Saturn appear just 19 arcseconds apart with Venus 7.3˚ to the northeast. Mid-month, Jupiter enters the scene. On the 14th, Venus rises 70 minutes before sunrise, with mag. –1.9 Jupiter rising 30 minutes after Venus.
Over the remainder of the month, both planets appear to converge. On the morning of 27 April, Venus and Jupiter appear 3.4˚ apart, 4˚ north of a slender 13%-illuminated waning crescent Moon.
Both planets appear 2.5˚ apart on 28 April, 1.6˚ apart on the 29th, and 41 arcminutes apart on the 30th. The closest approach is on 1 May, when Venus and Jupiter are separated by 22 arcminutes.
Viewing the pair won’t be as straightforward as their impressive individual magnitudes suggest due to low altitude. The best strategy is to catch Venus early in the month and stick with it. At the month’s end, they rise an hour before the Sun and it should be possible to spot them 30–45 minutes before sunrise.
As an extra challenge, both planets can be seen in broad daylight, Venus with the naked eye, Jupiter with optical assistance. Using Venus as a guide provides an opportunity to observe Jupiter in daylight. By using a driven equatorial mount, you can pick up Venus in the early morning and stay with it until after sunrise.
Minor planet 8 Flora almost at opposition
BEST TIME TO SEE: All month, closest to Heze (Zeta (ζ) Virginis) on 12 April
8 Flora, an asteroid, is close to opposition on 12 April. Technically, opposition occurs when a superior or minor planet has an elongation of 180˚ from the Sun. However, some objects may not achieve this within a particular year, reaching an elongation of almost 180˚. On 12 April, Flora’s elongation reaches 170.3˚, which is just shy of a true opposition, but certainly good enough to present the asteroid at its best for the year.
On this date Flora shines at mag. +9.8 in the constellation of Virgo, the Virgin. It’s located near to mag. +3.4 Heze (Zeta (ζ) Virginis) this month. On the night of 12 April, 8 Flora lies 1˚ north of Heze (Zeta (ζ) Virginis). During the rest of April, it follows a gently curving track, approximately parallel to the line joining Heze to Auva (Delta (δ) Virginis), its brightness making it a great target for a small scope.
Flora is a large asteroid. Its mean diameter is 128km, based on tri-axial ellipsoidal dimensions of 136km x 136km x 113km and it has a high albedo of 24.3 per cent; a measure of how much incoming light the asteroid reflects. At favourable oppositions it can brighten to mag. +7.9, but is also capable of dimming to mag. +11.6. The near-opposition presents Flora at a fairly average brightness.
