Observations

July 2021 Southern Sky Guide

Monthly sky maps from the 2021 Australasian Sky Guide published by MAAS Media.

What’s in the sky this July?

Constellations

Constellations are groups of stars that represent mythological figures, fanciful beasts or maybe old scientific instruments. For millennia they have been used as a tool to share significant cultural stories and to track the passage of the weeks and months. Today, they also help astronomers delineate portions of the sky and locate astronomical objects. In July, in the early evening, these constellations dominate the sky:

  • Scorpius – Appearing high in the eastern sky, Scorpius is one of the brightest and most easily identifiable constellations. Recognisable by its hooked tail and the red supergiant star Antares as its heart, Scorpius is a constellation that looks like its namesake. In Greek mythology, the scorpion plays a role in many stories, however it is best known for its pursuit of Orion through the night sky.
  • Libra – The Scales of Justice hover off the head of Scorpius. These stars were also recognised as the claws of the Scorpion. In fact the wonderfully named star Zubenelgenubi means “the southern claw”.
  • Sagittarius – Also known as the Archer, this centaur is found in the eastern sky below the tail of Scorpius on July evenings. In Greek mythology, Sagittarius points his arrow towards the heart of Scorpius. However, to many this constellation looks more like a teapot!
  • Virgo – This giant constellation of the maiden is found in the north-western sky. It can be most easily found by locating the constellation’s brightest star, Spica. The rest of the figure is composed of relatively faint stars and looks little like a maiden.
  • Southern Cross and Pointer Stars – Throughout the month the Southern Cross is high in the south-western sky near the bright Pointer Stars of Alpha Centauri and Beta Centauri. This landmark of the southern sky points the way toward the south celestial pole.
  • Centaurus – Surrounding the Southern Cross on three sides is the other centaur of the night sky, Centaurus. The Pointer Stars make up the front legs of the centaur. Centaurus is another large constellation including many delights of the southern sky, including Alpha Centauri – the closest star system to the Sun – and the globular cluster Omega Centauri.

Planets

Mercury is a morning planet this month. Venus and Mars are evening planets. And Jupiter and Saturn can be seen all night. Use the Moon as a guide to help you find the planets during the month.

  • Mercury – The smallest planet is visible in the morning twilight sky, low in the north-eastern sky. It passes from Taurus into Gemini and disappears into the morning twilight by the middle of the month.
  • Venus – Venus is the Evening Star once again, shining like a diamond low in the western sky. It moves from Cancer into Leo during the month. On July 13 Venus the planet is just one moon-width below the much fainter, but reddish, Mars.
  • Mars  – The red planet is low in the west after sunset. Venus passes by at a hurried pace on the 13th.
  • Jupiter – The king of planets is rising in the east during mid-evening in the constellation of Aquarius. It is visible almost all night and by dawn it is low in the west.
  • Saturn – This ringed gas-giant also appears in the east from mid-evening in Capricornus. It leads Jupiter across the sky and by dawn is also low in the west.

Moon

For the monthly movements of the moon, check out our Moon Phase Calendar.

Let the Moon be your guide to the planets this month.

On July 8 a thin waning crescent Moon is to the left of Mercury in the dawn sky.

Now, in the evening sky…on July 12, a thin crescent Moon (this time a waxing crescent) is below and right of Venus early in the night. On the following day, when Venus and Mars are at their closest the crescent Moon is above and to their right. Later in the month, on July 24 the full Moon is just above Saturn. Then on July 25 the full Moon sits between Saturn and Jupiter. And finally, on July 26 the Moon appears just below and right of Jupiter.

On July 17 the first quarter Moon, that’s when the disc is half-illuminated, lies just below the bright star Spica in Virgo. Look for this in the north-western quarter of the sky during the first half of the night.

Deep Sky

Explore the universe through your telescope or binoculars and take in some of the gems of the July winter sky, but dress warmly!

  • Jewel Box open cluster – About 5000 light-years away, within the Southern Cross constellation, and not far from the “left-hand” star of the Cross, this open star cluster consists of thousands of young stars. Through a telescope many blue supergiants, and one distinctive red supergiant can be seen.
  • Sombrero galaxy – Also known as M104 from the Messier Catalogue. This galaxy is about 30 million light-years away and is situated within the constellation Virgo. It is best seen with a telescope.
  • Alpha Centauri star system – A star system consisting of three stars, Alpha Centauri A and Alpha Centauri B and the closest star to our sun, Proxima Centauri at 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 it has two exoplanets in orbit about it.
  • Omega Centauri globular cluster – One of about 150 globular clusters orbiting the Milky Way. The largest globular cluster, Omega Centauri is about 16,000 light-years away in the Centaurus constellation. It is estimated to have over 10 million stars and may even be the core of an ancient galaxy partially canabalised by the Milky Way.

Other Events

On Tuesday July 6th Earth reaches its furthest point from the Sun, termed aphelion. This happens at 8:27am AEST to be precise, at which time Earth will be just over 150million km from the Sun.

Learn More

  • Purchase the 2021 Australasian 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 StarMap 07 July 2021, which shows the stars, constellations and planets visible in the night sky from anywhere in Australia.
  • Check out these resources for getting started.

2 responses to “July 2021 Southern Sky Guide

    • Roberto, Yes it was nice to have a clear night for a change. And a thin crescent Moon was sitting just below both. Hoping to see all three again tonight, cloud allowing. And, as long as you can see the western horizon from your balcony or window, you can stay-at-home (Sydney!) and still see these planets.

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