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The Evening Sky in June 2023
Venus is the brilliant 'evening star' appearing low in the northwest soon after sunset. It sets after 8 pm. It is now at its largest angle from the Sun as it catches up on the Earth. It is bright enough to see by eye in daylight, if you can get your eyes focused on infinity. Around 3:30 pm it is due north and about 30° above the horizon. That’s about 1½ hand-spans at arm’s length. On the 22nd the thin crescent Moon will be 4° (8 Moon diameters) below Venus in the afternoon and beside Venus at dusk. Around the 13th-14th Venus will be just below the Praesepe or Beehive star cluster. Venus isn’t impressive in a telescope, looking like a tiny featureless crescent Moon.
Mars appears as a medium-brightness reddish star above and right of Venus when the sky is dark. Over the month the gap between the two planets gets smaller. On the 2nd and 3rd Mars will be crossing the Praesepe star cluster, nicely seen in binoculars. Venus and Mars appear close in the sky but are at very different distances from us. At mid-month Venus is 93 million km away and Mars is 315 million km away.
Sirius, the brightest true star, appears in the west soon after sunset. It sets in the southwest around 9 pm, mid-month, twinkling like a diamond. Canopus, the second brightest star, is in the southwest. Canopus is a 'circumpolar' star: it circles the South Celestial Pole (SCP on the chart) clockwise but never sets from Aotearoa NZ.
Arcturus is the brightest star in the north sky. Its orange light is often split into red and green when it is low in the sky. Arcturus is relatively close at 37 light-years from the Sun. It appears bright because it is 170 times brighter than the Sun.
Crux, the Southern Cross, is south of the zenith. Beside it, and brighter, are Beta and Alpha Centauri, often called 'The Pointers' because they point at Crux. Alpha Centauri is the closest naked-eye star, 4.3 light years* away. Beta Centauri and three of the four brightest stars in Crux are hot, extremely bright blue-giant stars hundreds of light years away.
Orange Antares, high in the eastern sky, marks the body of Scorpius the scorpion. It is a red giant star: 600 light years away and 19 000 times brighter than the sun. The scorpion's tail, upside down, curves off to the right. Below Scorpius is Sagittarius, its brighter stars making 'the teapot'.
The Milky Way is brightest and broadest in the southeast toward Scorpius and Sagittarius. It remains bright but narrower through Crux and Carina then fades in the western sky. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one. The thick hub of the galaxy, 30 000 light years away, is in Sagittarius. A scan along the Milky Way with binoculars will find many clusters of stars and some glowing gas clouds. Relatively nearby dark clouds of dust and gas look like holes and slots in the Milky Way. The dust, more like smoke, comes from old red-giant stars like Antares. These clouds eventually coalesce into new stars.
The Clouds of Magellan, LMC and SMC, in the lower southern sky, are luminous patches easily seen by eye in a dark sky. They are two small galaxies about 160 000 and 200 000 light years away. They are much smaller than our galaxy but still contain billions of stars.
Bright planets are in the late night or morning sky. Saturn rises due east before midnight at the beginning of the month and around 10 pm at the end. It has a cream tint and is the brightest ‘star’ in an empty region of sky. By dawn it is north or northwest of the zenith. Golden Jupiter rises around 4:30 a.m. at the beginning of June; around 3 a.m. at the end. It is the brightest ‘star’ in the morning sky. By dawn it is high up the northeast sky. At the beginning of the month Mercury rises around 5:30, below and right of Jupiter. It sinks lower. On the 14th Mercury will be 7° (a binocular field width, roughly) to the right of the Matariki/Pleiades star cluster, rising around 6:20.
*A light year (l.y.)is the distance that light travels in one year: nearly 10 million million km or 10^13 km. Sunlight takes eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in four hours. It takes sunlight four years to reach the nearest star, Alpha Centauri.
Notes by Alan Gilmore, University of Canterbury's Mt John Observatory, P.O. Box 56, Lake Tekapo 7945, New Zealand. www.canterbury.ac.nz