The Sky Tonight is a monthly update of the amazing things you can find when looking up from here in Western Australia. This section is written by Jacquie Milner, resident astronomer at the Scitech Planetarium.
The casual observer
The latest sunset of the summer occurs on the 4th January, when the Earth reaches perihelion, or the closest point in its orbit to the Sun. However you probably wonâ€™t notice the evenings growing noticeably shorter until February â€“ although the time for sunrise should have changed by about half an hour during this time.
Are you wondering what that bright light in the west is at the moment? Itâ€™s the planet Venus, reflecting lots of sunlight from the cloud tops of its thick atmosphere. Read more about which planets are where below in the â€śPlanets to look forâ€ť section.
While youâ€™re out there enjoying the warm summer evenings, find out what satellites will be visible from you location by checking out http://www.heavens-above.com/
They should be visible nearly all night long, especially during the first weeks of January, when the Sun is still near its southern extremity and not all that far below the horizon â€“ at least not from a satellites high point of view.
Dates of interest
1st â€“ Mars passes within 7 arcminutes of Neptune, evening sky
2nd â€“ Moon under Venus, evening sky
3rd â€“ Next to Mars, evening sky
4th â€“ Earth at perihelion
19th â€“ Moon under Jupiter, morning sky
25th â€“ Moon under Saturn, morning sky
26th â€“ Moon to the left of Mercury, morning twilight
31st â€“ Moon to left of Venus, evening sky..
Planets to look for
Venus will dominate the evening sky for yet another month, as it continues to move closer towards us on its inside orbit. It will pass between Earth and Sun (Inferior conjunction) in late March, but during January it will continue to grace our summer evenings with its bright light.
Not far above it is Mars, which is slipping away around the far side of the Sun. No longer bright, you might miss it unless youâ€™re deliberately looking for it. The Moon is next to it on January 3rd. Neptune is also in the same line of sight on the 1st of January, but you will need a telescope to see this! You wonâ€™t need a great deal of magnification, but the larger the telescope the bluer Neptune should appear. The sapphire-blue of Neptune should make a nice contrast with the orange-red of Mars.
Jupiter is now rising in the late evening, so itâ€™s still for night owls. It wonâ€™t be good evening object until March. Saturn is back in the morning sky rising at 2am by the end of the month. Mercury also puts in a good pre-dawn appearance during the second half of the month â€“ look for it with the Moon in the morning twilight on the 26th.
Constellation of the month
Dorado the Goldfish
This is not meant to be the boggle-eyed fish youâ€™re used to seeing in a small bowl on the kitchen table, but rather a large tropical fish with gold-coloured skin. It was introduced to the sky by two Dutch navigators, Pieter Dirkszoon Keyser and Frederick de Houtman, who had watched it leap from the water to chase flying fish, which is why it is next to the constellation Volans, the Flying Fish, in the sky. (Incidentally, this is the same de Houtman that the Houtman Abrolhos, of the coast of Geraldton, are named after.)
Although it is a relatively faint constellation it contains the greater part of the Large Magellanic Cloud, the largest of the satellite galaxies to our Milky Way - the other half is in Mensa, which represents Table Mountain at the Cape of Good Hope in the Republic of South Africa. The misty look of the Large Magellanic Cloud is supposed to be the cloud that often sits on top of the terrestrial mountain at the Cape.
The huge Tarantula Nebula is within the constellation boundaries, too, (see below for more information) and nearby is the location of Supernova 1987a, the closest supernova to occur since the invention of the telescope.
It also contains the ecliptic pole, just off the end of the tail of the fish. This is the point that wobble of precession rotates around.
Dorado lies in between the bright stars Canopus and Achernar, the Large Magellanic Cloud under its tail.
Objects for the small telescope
The Tarantula Nebula
To one side of the Large Magellanic Cloud is a large, bright knot of gas known as the Tarantula Nebula. In the past is was also known as 30 Doradus, and if you have a goto telescope youâ€™ll need to know itâ€™s also called NGC 2070.
Itâ€™s not too hard to see how this nebula got its name; even in a small telescope the bright cluster of stars at the centre, the eyes of the spider, are surrounded by large loops of gas that look like legs. If you donâ€™t agree, let your imagination loose â€“ what do you see?
This is an emission nebula, a place where new stars are being born, and it is lit up by a cluster of super giant stars. The nebula, made up of mainly hydrogen gas, is super giant as well, at nearly 1000 light years in diameter â€“ which is nearly seven times larger than the Great Orion Nebula, M42. If it was as close as the Great Orion Nebula it would fill the whole constellation of Orion and cast shadows here on Earth, there wouldnâ€™t be much of a night as we know it now! The Tarantula Nebula is truly an impressive monster. Perhaps itâ€™s a good thing itâ€™s so far away then.
The Tarantula nebula is easy to find as a small, bright knot of light to one side of the Large Magellanic Cloud.
A cluster of super giant stars light up the nebula from the inside, where many new stars are being born.
Credit: TRAPPIST/E. Jehin/ESO - http://www.eso.org/public/images/eso1023a/
The IAU Ratifies 220 Official Star Names
Following on from the naming of fourteen stars and their exoplanets, the International Astronomical Union has now formalised a further 220 star names. Many of these will be familiar to regular stargazers as what we call the proper names of the brightest stars in the sky, such as Sirius, Canopus, Antares and Rigel. But it is also to reduce confusion around stars such as Betelgeuse and Fomalhaut, which can have many different spellings.
For us here in Australia we can now give three names to the stars in the Southern Cross: Alpha Crucis is Acrux, beta Crucis is Mimosa and gamma Crucis at the top is Gacrux. The two stars of the Pointers have also had their named formalised, which is okay for Rigil Kentaurus, or alpha Centauri, but it will certainly help for Hadar, or beta Centauri, who was also known as Agena on some maps. It also formalises the faint red dwarf Proxima Centauri, famous for being the closest star to our own solar system.
For more information and the full list of stars go to https://www.iau.org/public/themes/naming_stars/ and scroll down the page to find the list.
The proper names for these familiar stars are now standardised and official.