2015 September 20
Mars greets Regulus in the morning sky
Mars is already visible in the morning sky, but on Friday September 25 it comes within 1 degree of Regulus (alpha Leonis), the magnitude 1.4 star at the bottom of the backward question mark asterism in Leo (RA10h 9min 11sec, dec +11deg 53arcmin 25arcsec). Although closest approach is on Sept 25, Mars and Regulus remain close together for a day or so either side of this date. On Sept 24 Mars lies around 1 degree away and slightly to the west of Regulus while by Sept 26 it lies slightly further away but now to the east of Regulus. The track of Mars over these few days is shown on the sky chart.
Mars rises at 02:41UT (03:41BST) shortly after brilliant Venus which rises at 02:06UT. Mars shines at magnitude 1.8 (Venus -4.5) and presents a disk diameter of 3.9arcsec with the north face of the planet tilted towards Earth. The Sun rises at 05:46UT around these dates.
In addition to getting up early you will also need a very good eastern horizon as Mars will only be 7 degrees above the horizon at 03:30UT. Acting as a guide to Mars will be Venus which will lie due east at this time, 12 degrees up.
By 04:15UT Mars will have increased its altitude to 13 degrees while Jupiter (magnitude -1.7) will also now have risen: Venus and Jupiter bracketing Mars (which may need binoculars to be seen) in a glorious early morning planetary display.
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