Get ready as comet C/2017 K2 draws closer and play spot the difference with two triangles
When to use this chart
1 October at 00:00 AEST (14:00 UT)
15 October at 23:00 AEDT (12:00 UT)
31 October at 22:00 AEDT (11:00 UT)
The chart accurately matches the sky on the dates and times shown for Sydney, Australia. The sky is different at other times as the stars crossing it set four minutes earlier each night.
OCTOBER HIGHLIGHTS
Comet C/2017 K2 (PanSTARRS) is worth following during autumn and summer. Ideal from the Southern Hemisphere, it’s setting late in the evening and has possibly achieved 8th magnitude. The comet skirts around the head of the Scorpion, following the Scorpius/Lupus border during October. It slowly brightens as it continues its southward trek, passing through Norma, Ara and concluding the year in Pavo. By then it will be circumpolar from mid-latitude Australia.
STARS AND CONSTELLATIONS
Some constellations have northern and southern counterparts, such as Pisces and Piscis Austrinus. A lesser-known pair, each composed of three main stars, look exactly like their namesakes. Rising early October evenings in the northeast a distinctive narrow isosceles triangle of 3rd- to 4th-magnitude stars called Triangulum. Low in the southwest you’ll find Triangulum Australe, sitting on its base above the Pointers, with a prominent 2nd-magnitude apex star.
THE PLANETS
Saturn is still well-placed to observe early in the night, transiting around the end of twilight (midmonth) and visible until the early morning. With Neptune and Jupiter at opposition last month, they are well up in the evening hours, crossing the meridian around 23:00 (midmonth). Uranus is rising early in the evening and visible most of the night. Mars arrives just before midnight and transits around dawn. Unfortunately, Venus and Mercury remain too close to the Sun to observe.
DEEP–SKY OBJECTS
This month a visit to the constellation of the Water Bearer, Aquarius, or more specifically to the western end close to the border with the more recognisable roof-shaped asterism in Capricornus. NGC 7184 (RA 22h 02.6m, Dec –20° 49’) is an 11th-magnitude, nearedge-on barred spiral galaxy. It has a reasonably bright halo (1×4 arcminutes) with a star-like nucleus. It displays two distinctive stars, an 11th-magnitude star on its northeast end, with another a similar distance due west of its centre.
Move 3° east to discover impressive double star 41 Aquarii (RA 22h 14.3m, Dec –21° 05’). The two components are mag. +5.6 and +6.7, just 5 arcseconds apart. Both should be visible with reasonable seeing and magnification (150x). The real attraction of this double is the colour contrast, one yellow and the other blue.