Find out what to go out and look at this month


Mercury is visible very low in the Eastern morning sky until the middle of July appearing in the constellation of Taurus (The Bull). Mercury will reach its greatest elongation in the East on the 5th of July and it’ll move into the constellation of Gemini (The Twins) as it makes its way back towards the Sun and disappearing in the Sun’s glare. Venus and Mars will be visible low in the Western evening sky in July. Both planets will start the month off in the constellation of Cancer (The Crab), but as we move through July, they will move into the constellation of Leo (The Lion). At the start of the month, Venus will set at 07:19 pm (AWST) and Mars will set at 07:52 pm (AWST) and by the end of July, Venus will set at 08:12 pm (AWST) and Mars will set at 07:23 pm (AWST).

Mercury on the 15/07/21 at 06:30 am. Image Credit: Stellarium
Mercury's greatest elongation in the East on the evening of 05/07/2021. Image Credit: Stellarium
Venus and Mars on the 15/07/21 at 06:00 pm. Image Credit: Stellarium

Jupiter and Saturn can be found in the Eastern late evening sky. Jupiter can be found in the constellation of Aquarius (The Water-Bearer) while Saturn can be found in the constellation of Capricornus (The Sea-Goat) during July. At the beginning of the month, Jupiter will rise at 09:21 pm (AWST) and Saturn will rise at 07:48 pm (AWST). By the end of the month, Jupiter will rise at 07:11 pm (AWST) and Saturn will have risen before sunset.

Uranus can be found in the early morning in the constellation of Aries (The Ram). At the beginning of July, Uranus will rise at 03:02 am (AWST) and by the end of the month, it’ll rise at 01:08 am (AWST). Neptune will be viewable as well in the early morning between the constellation of Aquarius and the constellation of Pisces (The Fish). At the start of July, Neptune will rise at 11:00 pm (AWST) and by the end of the month, it’ll rise at 09:01 pm (AWST).

Jupiter and Saturn on the 15/07/21 at 11:00 am. Image Credit: Stellarium
Uranus and Neptune on the 15/07/21 at 05:00 am. Image Credit: Stellarium

Conjunctions And Occultations:

Conjunctions involve object(s) in the Solar System and/or more distant objects, such as a star. It’s an apparent phenomenon in which multiple objects which aren’t close together appear close in the sky and it’s caused by the observer’s perspective. An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer.

Astronomical Events This Month:

The Delta Aquarids:

The Delta Aquariid meteors are due to peak on the night of the 27th/28th of July and they’ll favour southern hemisphere observers, which includes observers in Perth. The shower is active from the 12th of July to the 23rd of August and they can vary in their hourly rate each year between 10 to 20 meteors per hour. In 2021, the Last Quarter Moon is near the Aquarius Constellation so the Delta Aquariids are expected to have a reduced hourly rate (meteors per hour).

The Delta Aquarids is located in the constellation of Aquarius and it can be viewable from 08:00 pm on the 27th, but it’ll be best to wait until around 03:00 am on the 28th. The source of the Delta Aquariids is believed to be 96P/Machholz 1 comet which was part of the unnamed ancient stream of Kreutz sungrazing comets.

The Delta Aquarids on the 28/07/21 at 05:00 am. Image Credit: Stellarium
A meteor from the Delta Aquarids. Image Credit: David S. Brown

Things To Look At This Month:

Omega Nebula:

The Omega Nebula is located in the Sagittarius constellation. This emission nebula is regarded as one of the brightest and most massive star-forming regions of the Milky Way. Within the nebula, the radiation from an open cluster of ~35 hot, young stars heats the surrounding gas to incandescence. There could be as many as 800 stars in the associated cluster.

The nebula was first discovered in 1745 and recorded by Charles Messier in 1764, and it’s so named because it appears like the Greek letter Omega. Alternatively, it may be seen as a horseshoe with a “tail” to one side giving it, perhaps, a swan’s neck appearance. It is also referred to as the Swan, Checkmark, Lobster and Horseshoe Nebula.

Omega Nebula on the 15/07/20 at 09:00 pm. Image Credit: Stellarium
M17 - Omega Nebula. Image Credit: Putman Mountain Observatory
Trifid And Lagoon Nebulas:

The Trifid Nebula (M20 & NGC 6514) and Lagoon Nebula (M8 & NGC 6523) can be found close together in the constellation of Sagittarius.

The Trifid Nebula is an emission (pink) and reflection (blue) nebula, with an open star cluster. The Trifid (Meaning “divided into three lobes”) comes from the three-pronged dark lanes (dark nebulae) through the nebula that blocks off the light behind. The nebula is 2,660 light-years away and is 15 light-years across.

The central star formation “nursery” where hot young stars power the emission nebulae. Infrared telescopes have shown there are 30 embryonic and 120 newborn stars not yet bright enough to emit light in the visible light part of the light spectrum. The new stars are very young at 400,000 years old with the central star in the nebula being a cluster of four-star systems, two of which are close binary stars, so there are six stars in all.

The Lagoon Nebula is, sometimes called the “Hourglass Nebula” (not to be confused with the true “Hourglass Nebula” in the constellation of Musca), is a very young nebula, perhaps less than 10,000 years. The nebula is further away than the Trifid Nebula at 4,100 light-years away and it’s a lot bigger with the nebula being 100 light-years across and 50 light-years high. It is one of the finest and brightest star-forming regions in the sky and contains many “Bok globules”, which contain dense cosmic dust and gas from which star formation may take place. The central emission area is energised by a bright ultraviolet “O4” class star and it’s a relatively easy object for amateur astrophotographers.

Trifid and Lagoon Nebulas on the 15/07/20 at 09:00 pm. Image Credit: Stellarium
Trifid and Lagoon Nebulas. Image Credit: Perth Observtory Volunteer Andrew Lockwood
Ptolemy Cluster:

The Ptolemy’s Cluster (M7 & NGC 6475) is a large open cluster near the sting of the tail of the constellation of Scorpius. While it’s 980 light-years away from us, it’s large enough to be seen with the unaided eye in a dark sky and is a nice sight in binoculars. The cluster is 25 light-years across, and it contains around 100 stars in total. It was first described by the Greek-Roman astronomer Ptolemy in 130 AD from which it gets its common name of Ptolemy’s cluster. The colour of the stars in this cluster is predominately yellow, indicating this is an older cluster, with an estimated age of 260 million years. Clusters that contain many hot blue stars, like the Pleiades, are considerably younger.

Ptolemy Cluster on the 15/07/21 at 09:00pm. Image Credit: Stellarium
Ptolemy Cluster. Image Credit & Copyright: Lorand Fenyes
Omega Centauri:

Omega Centauri or NGC 5139 is the largest and brightest globular cluster of 180 in the Milky Way and is the second-largest known, with only Mayall II in the Andromeda Galaxy being larger coming ins about twice its mass. The Globular cluster is located in Centaurus Constellation and it’s a naked eye ‘star’ and visible in binoculars as a ‘fuzzy blob’. Omega Centauri contains at least 3 million stars and the cluster has a diameter of roughly 150 light-years and the stars are roughly 12 billion years old. The average distance between the stars at the centre is around 10% of a light-year or more than 100 times the diameter of our solar system. It may be a dwarf galaxy that has been captured and disrupted by the Milky Way galaxy and measurements of its star movement by Hubble has indicated that a black hole may be located at the core of the cluster.

Omega Centauri on the 15/07/21 at 09:00 pm. Image Credit: Stellarium
Omega Centauri. Image Credit: Perth Observtory Volunteer Andrew Lockwood

Phases Of The Moon:

July 2021 Moon phases