Jupiter stood at opposition a week ago and remains unmistakable as it climbs through our SE evening sky to blaze high in the S at midnight. Before dawn, though, the two brightest objects low in the S are Saturn and, brighter still, Mars.
Our chart plots their motions over the coming months as they, too, reach opposition. It depicts a 40° by 20° window of sky centred some 18° high in the S as seen from London, but considerably higher for S Europe and the USA.
Mars, the target of the European-Russian ExoMars 2016 mission which is due to be launched on 14 March, is tracking eastwards at present and passes one third of a Moon-width N of the star Graffias in Scorpius on on the 16th. Graffias is a multiple star, easily visible as a double through a small telescope, though each of these components consists of at least three stars.
The leading star on the chart, the distinctly reddish supergiant Antares in Scorpius, is slightly variable around mag 1.0 and is outshone by both planets. Rho Ophiuchi, 3° N of Antares, is another star that appears as a pretty double through telescopes, but is actually multiple.
Just 1.3° W of Antares is the fuzzy ball of M4, a globular cluster of ancient stars, that is one of the closest of its type at some 7,200 light years.
The name Antares means “rival to Mars” and derives from its ruddy hue, but Mars is now appreciably brighter at mag 0.0 and improves sixfold to mag –2.0 by the time it reaches opposition on 22 May. It is then 76 million km distant and appears 18 arcsec wide if viewed through a telescope, 8 arcsec more than it does at present.
Saturn lies in Ophiuchus and improves from mag 0.5 to 0.0 by its opposition on 3 June. It is then 1,349 million km away and its rings, their N face tilted 26° to us, are 42 arcsec wide around an 18 arcsec disc.
As it is overtaken by the Earth, Mars’ progress slows to a so-called stationary point on 17 April before becoming westerly, or retrograde, through opposition. It reverses again at another stationary point on 30 June, leading to its sinuous path across our chart, a path that takes it 4.4° S of Saturn on 25 August. Saturn’s motion is less flamboyant, being retrograde between stationary points on 25 March and 13 August.
For reasons that are not yet clear, the star Delta Scorpii, close to Mars at opposition and perhaps also multiple, doubled in brightness from its usual mag 2.3 to 1.6 early this century but now seems to have settled near the middle of that range.
