The Evening Sky in October 2017

Download a PDF containing this chart, additional charts for specific areas of the sky and descriptions of interesting objects visible at this time of year.

The Evening Sky in October 2017

Jupiter is the 'evening star' at the beginning of the month when it appears on the west horizon in the early twilight and sets around 8 p.m. It falls lower in the twilight night to night, disappearing around the middle of the month. Jupiter is on the far side of the Sun from us, 960 million km away.

Saturn is midway down the western sky at dusk, the brightest 'star' in that region. Well below and left of it is the orange star Antares. Saturn sets in the southwest after midnight at the beginning of October; before 11 pm by the end. It is 1570 million km away mid-month. Saturn appears oval-shaped in binoculars and small telescopes as the planet and the rings blend together. Larger telescopes show the rings, currently at their most 'open' or most tilted to our view. Saturn's biggest moon, Titan, looks like a star four ring-diameters from the planet. Smaller, fainter moons are closer in. The crescent moon will be below Saturn on the 24th.

Antares marks the body of the Scorpion. The Scorpion's tail loops up the sky in the evening, making a back-to-front question mark with Antares being the dot. The curved tail is the 'fish-hook of Maui' in Maori star lore. Antares is a red giant star: 600 light years* away and 19 000 times brighter than the sun. Red giants are dying stars, wringing the last of the thermo-nuclear energy from their cores. Massive ones like Antares end in a spectacular supernova explosion. Antares is about 20 times heavier than the sun. Above and right of the Scorpion's tail is 'the teapot' made by the brightest stars of Sagittarius. It is upside down in our southern hemisphere view.

Canopus is low in the southeast at dusk often twinkling colourfully. It swings up into the eastern sky during the night. Canopus is 13 000 times the sun's brightness and 300 light years* away. On the north skyline is Vega, setting in the early evening. It is 50 times brighter than the sun, 25 light years away and the 5th brightest star in the sky. From northern New Zealand the star Deneb is on the north skyline.

In the southwest are 'The Pointers ', Beta and Alpha Centauri, making a vertical pair. They point down to Crux the Southern Cross. Alpha Centauri, the top Pointer, is the closest naked eye star at 4.3 light years away. Beta Centauri is a blue-giant star, very hot and very luminous, hundreds of light years away.

The Milky Way is brightest and broadest in Scorpius and Sagittarius. In a dark sky it can be traced down to the south. In the north it meets the skyline right of Vega. From northern New Zealand the star Deneb can be seen near the north skyline in the Milky Way. It is the brightest star in Cygnus the Swan. 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. The actual centre, with a black hole four million times the sun's mass, is hidden by dust clouds in space. Its direction is a little outside the Teapot's spout. The nearer 'interstellar' clouds appear as gaps and slots in the Milky Way. The dust and gas has come from old stars that have thrown much of their material back into space as they faded or blew up. New stars eventually condense from this stuff. A scan along the Milky Way with binoculars shows many clusters of new stars and some glowing clouds of left-over gas. There are many in Scorpius and Sagittarius and in the Carina region.

The Large and Small Clouds of Magellan, LMC and SMC, look like two misty patches of light in the southeast sky. They are easily seen by eye on a dark moonless night. They are galaxies like our Milky Way but much smaller. The Large Cloud is about 5% the mass of our Galaxy and the small one 3%. That is still many billions of stars in each. The LMC is around 160 000 light years away; the SMC around 200 000 l.y.

On moonless evenings in a dark rural sky the Zodiacal Light is visible in the west. It looks like late twilight: a faint broad column of light tilted toward Antares, fading out at the Milky Way. It is sunlight reflecting off meteoric dust in the plane of the solar system. The dust may have come from a big comet, centuries ago.

Brilliant Venus (not shown) might be seen on the eastern horizon at dawn. At the beginning of the month it rises 50 minutes before the Sun. It sinks lower in the twilight as it moves to the far side of the Sun from us.

*A light year (l.y.) is the distance that light travels in one year: nearly 10 million million km or 1013 km. Sunlight takes

eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in four hours. It takes four years to reach the nearest star, Alpha Centauri.

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
P.O. Box 57 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lake Tekapo 7945
New Zealand