THE SOUTHERN HEMISPHERE
With Glenn Dawes
As Jupiter and Saturn both reach opposition this month, we follow the trail of Comet 2P/Encke
When to use this chart
1 July at 24:00 AEDT (13:00 UT) 15 July at 23:00 AEDT (12:00 UT) 31 July at 22:00 AEDT (11:00 UT)
JULY HIGHLIGHTS
Comet 2P/Encke is famous for being a comet with one of the shortest periods, only 3.3 years. Since passing through perihelion in late June, ‘Encke’ has moved into the evening sky. The comet opens July in Cancer at its maximum brightness (possibly 7th magnitude), setting around the end of astronomical twilight. As it moves away from the Sun it gains altitude, passing through Hydra, Sextans and Crater before closing July near the trapezium of Corvus.
THE PLANETS
This month is planet-observer heaven, with both Jupiter and Saturn at opposition, rising around sunset and visible for the whole night. Both reside in Sagittarius, with Jupiter following the Teapot and Saturn close behind. Although
DEEP-SKY OBJECTS
This month we visit the constellation of Libra. Starting at naked-eye star Sigma Librae, move 4.1° NNW to find the brilliant double star HN 28 (RA 14h 57.4m, dec. –21° 24’). The main components are mag. +5.8 and +8.2, separated by 24”. Their colours offer an impressive contrast – orangy yellow and red respectively.
Return to ‘Sigma’, jump 3.5° ENE to discover an impressive close
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.
STARS AND CONSTELLATIONS
The ancient constellation of Hercules is marked by a distinctive asterism of six stars sitting close to the evening northern horizon. This Greek god is typically depicted as kneeling on his right leg with his left arm stretched out towards Lyra. Today, this hand is empty, however some early star maps showed him gripping Cerberus. This now obsolete constellation recognised the 12th task of Hercules where he fought the three-headed monster (shown as a dog or snake) that guarded the underworld.
Neptune and Mars rise in the evening they are best observed in the morning. Brilliant Venus is high in the predawn eastern sky, passing near Aldebaran on the 11th. Mercury returns to the dawn glow but remains low, reaching maximum altitude on the 23rd. pair of galaxies, NGC 5898 (RA 15h 18.2m, dec. -24° 06’) and NGC 5903, 0.1° to its west. Although both are 11th magnitude ellipticals and of similar size there are some interesting differences. NGC 5898 shows a round, evenly illuminated 1’ halo with very little brightening towards the centre. In contrast NGC 6903 has a more elongated, diffuse 0.8’ x 1.3’ halo with an obvious star-like nucleus.
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