What’s in the sky this September?
Constellations represent groups of stars that have been given a name and more recently a border. For millennia they have been used as a tool to share significant cultural stories. Today, the 88 western constellations used here help astronomers map the sky and search for astronomical objects. This September these constellations dominate the spring sky:
- Sagittarius the half man half horse archer, looks more like a teapot than a centaur. High overhead its arrow points toward the heart of Scorpius now descending to the west. The spout of the teapot near the star Alnasl marks the area nearest to the heart of our galaxy and its monstrous black hole Sagittarius A* (pronounced Sagittarius-A-star)
- Scorpius is one of the brightest and most easily identifiable constellations. Easily identified by its hooked tail and the red supergiant star Antares meaning ‘rival of Mars’. Scorpius is the constellation that looks most like its namesake. In Greek Mythology, the scorpion plays a role in many myths, however it is best known for its pursuit of Orion through the night sky.
- Crux or the Southern Cross and its pointers of Alpha and Beta Centauri are now low in the south west making them hard to see in the early evening. Light pollution and the thicker atmosphere near the horizon dim the starlight.
- Aquila and Lyra. Both constellations are not well known in the southern hemisphere but contain the bright stars of Altair and Vega respectively. These two stars feature heavily in skylore from the northern hemisphere. In spring we can see them see them clearly in the early evening. Vega is the fifth brightest star in the night sky and will once again become the north polar star in about 12,000 years from now.
- Eridanus the river winds its way up from the horizon to the south east. While not bright it is long and ends with the ninth brightest star in the night sky, Achernar. Its high-speed rotation on its axis has altered its shape, making it the least spherical star in our galaxy.
All five naked eye planets: Mercury, Venus, Mars, Jupiter and Saturn can all be seen at various times this month. Watch how their positions change throughout the month as they travel along the ecliptic, the path of the Sun and Moon.
- Mercury – The smallest planet is just visible in the western evening twilight sky moving from Leo to Virgo early in the month. On 19 September a thin crescent Moon is to the right or north of Mercury. On 22 September mercury passes less than a Moon width from Spica, the brightest star in Virgo.
- Venus – Moves rapidly from Gemini to Cancer and then Leo in the morning sky. On 14 September the waning crescent Moon is to the left or north of Venus.
- Mars – The red planet is in the north-west in the constellation of Pisces with the best viewing mid-month from around 1 am until the morning twilight. On 6 September the waning gibbous Moon is below or to the west of Mars, while the next morning it will be above or the north.
- Jupiter – The king of planets is in Sagittarius high in the evening western sky. On the 25th the waxing gibbous Moon is above or east of Jupiter. With a sturdy mounted pair of binoculars, the Galilean moons may be visible.
- Saturn – The ringed gas-giant is also high in Sagittarius in the evening western sky. On the 26 September the waxing gibbous Moon is to the right or east of Saturn. Both Saturn and Jupiter are getting closer to one another for a conjunction in late 2020. They will be the closest to each other, as we see them, since the 17th
For the monthly movements of the moon, check out our Moon phase calendar.
Explore the universe through the lens of your telescope and take in some of the gems of the September sky:
- Alpha Centauri star system – A visual binary comprising of Alpha Centauri A and Alpha Centauri B locked in a gravitational dance of about 80 years to orbit one another. These two appear as one star to us while a third member of the system and the closest star to our sun, Proxima Centauri is just 4.2 light-years away. Proxima Centauri is a red dwarf star and is only visible through large telescopes. It is believed to be orbiting the first two stars and was found to have a planet in the habitable zone in 2016.
- NGC 104 or 47 Tucanae a globular cluster – One of about 150 globular clusters within the Milky Way. Though it is second largest and second brightest globular cluster within the galaxy, its bright compact core makes it the best from urban skies using binoculars or a small telescope. It contains several million old stars and is 13,000 light-years away within the Tucan constellation.
- M8 the Lagoon nebula. A cloud of gas and dust visually about three times the size of the Moon. It is 100 light years across and more than 4,000 light years away. Nebula is Latin for cloud and this particular nebula is an active star forming region with one star, Herschel 36 forty-two times the mass of the Sun and 200,000 times brighter. Binoculars or a small telescope will reveal it as a smudge on a moonless clear night. Long exposure astrophotography is needed to revel the trademark pink Hydrogen.
- NGC 253 the Silver coin galaxy. One of the brightest barred spiral galaxies visible to a small telescope with a dusty and active star forming nucleus. In the constellation of Sculptor it is about 10 million light years away and 70,000 light years across.
- Purchase the 2020 Australiasian Sky Guide by Dr Nick Lomb, featuring an annual report of what’s in the sky and the latest astronomical findings. Produced by MAAS Media.
- View the September Sky Chart, which shows the stars, constellations and planets visible in the night sky from anywhere in Australia
- Check out these resources for getting started