Mars and the PLEIADES
BEST TIME TO SEE: 1–10 April
Mars is a frustrating planet to observe. Coming to opposition every 2.1 years, it is close enough to show a decent disc size for just a few months around this time. After this the distance between Earth and Mars increases and the planet appears to shrink through the eyepiece. This makes it harder to see surface detail.
Following opposition, Mars does a clever trick. It virtually stands still relative to the horizon at the same time of night. The last opposition occurred on 27 July 2018, when
Mars had an apparent size of 24 arcseconds but from the UK it was low in altitude, even when at its highest point due south. Then, as it started to pull off its standing still trick, it gained altitude as it appeared to shrink.
At present, Mars looks tiny through the eyepiece, at around 4 arcseconds across. It’s also a lot dimmer than it was at opposition, currently shining at mag. +1.5 compared to –2.8 at the end of last July. Its characteristic salmon-pink colour stands out well, though, and this makes it easy to identify.
This month Mars passes south of the beautiful Pleiades open cluster, M45, in Taurus, tracking between the Pleiades and Hyades clusters. This presents a great opportunity for astrophotography (see page 76).
At present, Mars is unable to achieve its highest point in the sky, due south, in darkness. By the time the sky darkens, around 22:00 BST (21:00 UT), the planet appears 22° up in the west.
On 1 April it lies 3.4° south-southeast of the Pleiades. Mars does not linger and moves rapidly through Taurus over the following evenings. On 5 April, look out for mag. +4.3, 37 Tauri, 0.3° to the north of the planet as darkness falls. Mars will appear midway between Alcyone (Eta (d) Tauri), the brightest star in the Pleiades, and Ain (Epsilon (¡) Tauri), the northernmost star in the main V-shape of the Hyades.
Mars drifts further from the Pleiades as it passes north of the Hyades. On the evenings of 8 and 9 April it is joined by the waxing crescent Moon, making another great opportunity for astrophotography.
On 12 April, Mars forms a tight triangle with mag. +4.3 Upsilon (p) and +4.2 Kappa (g) Tauri. Both stars are separated by just over half a degree in the sky. On the evening of 18 April it passes 20 arcminutes north of mag. +4.3 Tau (o) Tauri. On 25 and 26 April, Mars will pass in front of the sixth magnitude open cluster NGC 1746.