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The night sky for July 2015

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during June 2015.

Arcturis, the brightest star in the constellation of Bootes, is visible in the southwest. Meanwhile, in the northwest, Merak and Dubhe of the constellation Ursa Major may be seen pointing towards the Polaris near the North Celestial Pole. Further north the w-shaped set of stars which form Cassiopeia may be seen, while towards the east the Summer Triangle is clearly visible. It is composed of three bright stars: Vega of Lyra, Deneb of Cygnus, and Altair of Aquila. Just to the left of Vega lies the Double-double: what appears to be a binary star system when viewed with binoculars becomes two binaries when observed through a telescope. Below Albireo, the head of Cygnus the Swan, the Cygnus Rift, a dark, dusty region of the Milky Way may be seen. Within the Cygnus Rift you may spot Brocchi's Cluster, also known as the Coathanger, while to the lower left of the summer triangle lies a faint constellation known as Delphinus the dolphin. Halfway between Arcturis and Vega lies the constellation of Hecules. The Keystone of Hercules consists of the four stars in its center, and on its right hand side lies M13, the Great Globular Cluster, and the brightest in the Northern Hemisphere.

The Planets


Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during July 2015.

Venus and Jupiter begin the month as pair in our north western evening sky after dark. They will gradually move further apart as Jupiter sinks more quickly into the western twilight. Venus, too, sinks throughout the month and appears a thin crescent through a telescope. Through a small telescope Jupiter’s 4 largest moons: Io, Europa, Ganymede and Callisto, are visible, lined up to either side of the planet.

High in the north-east lies Saturn, its rings and largest moon, Titan, visible through a small telescope. Close by are the claws of Scorpius, with Antares a little further to the right. Lying along the tail of the scorpion is NGC 6231, a bright cluster of stars which looks like a small comet. At magnitude +2.6 this is easily visible to the naked eye, but in a dark sight, with a good pair of binoculars, NGC 6231 appears in an area of nebulosity, intermingled with open clusters Trumpler 24 and Collinder 316 to form a complex sometimes known as the Scorpius Lizard.

A little above the Scorpions tail, NGC 6193 is visible to the naked eye at magnitude +5.2, and nearby NGC 6167 may be seen with binoculars or a small telescope. Below Scorpius is an upside down teapot formed from the brightest stars in Sagittarius. To the left of the teapot’s spout, just visible to the naked eye, is the Lagoon Nebula (M8). Along with the nearby Trifid Nebula (M20), the Lagoon Nebula is a good target for binoculars or a small telescope.

There are also a number of globular clusters in this part of the sky. The brightest is M4, and this is also one of the easiest to find, lying just 1.3 degrees west of Antares. Appearing as a small fuzzy ball in binoculars or small telescopes, a slightly larger telescope will begin to pick out individual stars. Also in this region, near the top of the teapot, is M22.

From its bright centre the Milky Way stretches overhead through the diamond-kite-shaped Crux, the Southern Cross, and on to Carina, Vela and Puppis, which together make up the great ship Argo Navis, famous in Greek mythology. To Maori the Southern Cross is known as Te Punga, the anchor of Tamareriti’s waka, which stretches out along the Milky Way.

Alpha Crucis, the brightest star in the Southern Cross appears to be a single star with a magnitude of +0.9, but a small telescope will reveal a double star with blue-white components of magnitudes +1.4 and +1.9. Beta Crucis, slightly fainter at +1.3 magnitudes, is also blue-white. Gamma Crucis, at the top of the cross, is easy to pick out by its reddish-orange colour. A little below Crux are the Diamond Cross and False Cross. To distinguish Crux, seek The Pointers, Alpha and Beta Centauri. Alpha Centauri is the third brightest star in the night sky at magnitude -0.27. Beta Centauri appears almost as bright, with a combined magnitude of +0.6. Using these stars to find the Southern Cross is as easy as ABC - Alpha, Beta, Crux.

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