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Country Always

Caring for Country

A Corner of the Empire

The Garden Palace

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The Holding Pen

The Agricultural Hall

Sepia photograph of the Technological College and Museum in Broken Hill

Regional Networks

Across New South Wales

A Museum of Doing

Technological Museum

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Transforming the Tramsheds

Powerhouse Stage 1 and the Harwood Building

A Symbol in Time

Sydney Observatory

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Ongoing Transformations

Powerhouse Ultimo

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Applied Arts and Sciences

Defining the terms in the 21st century

Powerhouse Renewal

A dense galaxy cluster.

Sky Guide August 2024

Sydney Observatory's monthly guide to the southern sky

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Powerhouse Food: Producers

Across Western Sydney24 Aug 2024 — 25 Jul 2025

We Rise

Blak Powerhouse

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Powerhouse-1 Mission Launch to the ISS

An initiative of the Powerhouse: Future Space program

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Exoskeleton

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Powerhouse x We Are Warriors

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Stories

Sky Guide August 2024

Sydney Observatory's monthly guide to the southern sky
With Geoffrey Wyatt and Dr Andrew Jacob
A dense galaxy cluster.

The best time to observe any meteor shower is after midnight, usually a few hours before dawn. This month during the mornings of Sunday 11 to Tuesday 13 August look low toward the north-east into a part of the sky known as Perseus. If the conditions are good, you may see a meteor, more commonly called a shooting star.
Dr Sarah Reeves, science curator and astronomer

Moon phases

New Moon Sunday 4 August 9:13 pm AEST

First quarter Tuesday 13 August 1:19 am AEST

Full Moon Tuesday 20 August 4:26 am AEST

Last quarter Monday 26 August 7:26 pm AEST

Planets

The planet Saturn against a deep black background

EVENING

Mercury starts the month low in the west in Leo. At the end of the first week of August it has a brief excursion to the non-Zodiacal constellation Sextans, returning to Leo after a few days. It disappears into the twilight just before the middle of the month.

Venus is low in the west in Leo for most of the month but moves to Virgo at the beginning of the last week of the month. It passes Regulus, the brightest star of Leo, on 5 August with a separation of just two moon-widths. On 6 August a very thin crescent Moon is above and to the right or north of Venus, forming an interesting triangular pattern with Regulus, Venus and Mercury.

Saturn appears low in the east in Aquarius during the last week of the month.

MORNING

Mars is in the north-east in Taurus. On 15 August Mars passes Jupiter at a separation of under one moon-width. On 28 August, the crescent Moon is below and to the left or north of Mars.

Jupiter is in the north-east in Taurus. On 27 August the crescent Moon is below and to the left or north of Jupiter.

Saturn is in the west in Aquarius. On 21 August the gibbous Moon is below and to the left or south of Saturn, while the next morning it is above and to the right or north.

Constellations

Constellations are groups of stars that represent mythological figures, fanciful beasts or old scientific instruments. Some have been used for millennia as a tool to share significant cultural stories and to track the passage of the weeks and months. Today they also help astronomers mark out portions of the sky and locate astronomical objects. Those listed below have been selected for their visibility in the evening up to two hours after sunset as seen from the Southern Hemisphere.

The night sky showing multiple stars

Boötes the herdsman is low in the north May to August and quite unremarkable apart from its star Arcturus, which is the fourth brightest star in the night sky overall and the brightest in the northern sky. Arcturus is only slightly more massive than our Sun, but its advanced evolution has taken it off the Main Sequence to become a bloated giant 25 times bigger and 170 times brighter, which gives it a golden orange hue at about 37 light years.

Centaurus the half man half horse represents the scholarly Chiron, tutor of many of the Greek gods and heroes including Heracles, Achilles and Jason. Its two brightest stars of Alpha – the closest star system to the Sun and Beta Centauri – make up the front legs of the centaur. When used with Crux, they help find south. It also contains the most spectacular globular cluster of all, Omega Centauri NGC 5139. Centaurus was one of the original 48 constellations as mapped by Ptolemy and originally included Crux before the latter was identified separately in the 17th century CE.

Crux or the Southern Cross is the smallest of all 88 western constellations and consists of four bright stars. Along with the nearby pointers of Alpha and Beta Centauri, Crux can be used to find south. Draw an imaginary line from the top of the cross shape though the bottom and across the sky. Midway between the pointers draw a line perpendicular to the line that joins them. Where these two longer lines intersect is close to the southern celestial pole. From this point drop to the horizon to locate south. This technique works at any time of the night, any time of the year. The superb open cluster NGC 4755 (Jewel Box) appears very close to the second brightest star, Beta Crucis.

Libra has been recognised historically as scales or a part of Scorpius, forming the scorpion’s claws, however the Romans returned it the separate set of scales we are familiar with today. The former association of Libra and Scorpius is reflected in the names of the two brightest stars in Libra: Zubenelgenubi and Zubeneschamali, meaning ‘the southern claw’ and ‘the northern claw’ respectively. Libra is host to the star Gliese 581, the first star identified with an Earth-like exoplanet.

Ophiuchus the serpent bearer is an ancient constellation and one of the original 48 as mapped by Ptolemy. It is said to represent the mythical healer Aesculapius. It sits close to the galactic centre in Sagittarius. It is now the thirteenth Zodiac sign with the Sun, Moon and planets passing through it from 30 November to 17 December.

Stars with a drawing of a person amongst the stars.
OBJECT NO. 85/59-16/29

Sagittarius the archer is located just behind the sting of Scorpius. In Greek mythology the archer is a centaur pointing his arrow towards the heart of Scorpius, though from the Southern Hemisphere this constellation looks more like a teapot. Sagittarius is home, as we see it, to the centre of our galaxy, the Milky Way with a monstrous black hole about four million times the mass of the Sun and 26,000 light years away. Called ‘Sagittarius A *’ (pronounced as Sagittarius-A-Star), images taken in 2017 and released in May 2022 from NASA’s Event Horizon Telescope (EHT) show matter swirling around it at close to the speed of light. The event horizon is about the same distance from the singularity as Mercury is from our Sun.

Scorpius the scorpion is one of the easiest constellations to pick out as it is one of the few that does look like what it’s supposed to represent. Among the brightest parts of the Milky Way along with Sagittarius, the red supergiant star Antares (Rival of Mars) marks the heart of the scorpion. From the heart, three stars mark the head and claws while moving the other way shows the body, hooked tail and sting. The scorpion plays a role in many myths; however, it is best known in Greek mythology for its pursuit of Orion through the night sky. Scorpius dominates the sky from June to August when it sits high overhead. It contains the globular cluster M4, the first in which individual stars were resolved approximately 6000 light years away. It also has two open clusters M6 the Butterfly cluster, which is 100 million years old, and M7 the Ptolemy cluster at just 200 million years old.

Virgo the maiden is the second largest of all constellations. Virgo rises in the east in April and sets after sunset by mid-August. 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 a little like a maiden. It is one of the two constellations in which the ecliptic and celestial equator cross – the other being Pisces. This one marks the current position of the September equinox, the beginning of our Spring in the Southern Hemisphere. It is home to a cluster of galaxies, of which M87 is the largest, at around 60 million light years with a central black hole at least 7 billion times the mass of the Sun. Virgo’s one bright star, Spica, is the 16th brightest in the night sky and about 250 light years away.

Star cluster, M4.

Deep sky

Alpha Centauri is a triple star system consisting of Alpha Centauri A and B, and the closest star to our Sun, Proxima Centauri (Alpha Centauri C) at 4.2 light years away. Proxima Centauri is a red dwarf star, only visible through large telescopes, and revolves around the other two stars once every 550,000 years. Two planets have been confirmed in orbit around Proxima: Proxima b and Proxima c. Proxima b is an Earth-mass planet discovered in 2016, which is located within the habitable zone of Proxima Centauri, while Proxima c is a super-Earth exoplanet discovered in 2020, which orbits the star once every 1928 days.

The Jewel Box (NGC 4755) is an open star cluster approximately 10 million years old. It is close to Beta Crucis (Mimosa), the second-brightest star in Crux (Southern Cross) and in binoculars and small telescopes appears as an ‘A’ shape. It is about 20 light years across, and has around 100 stars, most of which are blue and include some blue and red super giants such as DU Crucis which is around 500 times the diameter of the Sun. The Jewel Box is one of the youngest open clusters in our skies with an estimated age of about 14 million years. It lies at a distance of about 6400 light years.

M4 is the closest globular cluster to Earth at 5500 light years away. M4 is easy to locate, sitting next to the red supergiant star, Antares, in Scorpius. The cluster contains more than 100,000 stars with approximately 40,000 of these being white dwarf stars.

M6 the Butterfly and M7 Ptolemy’s are two open star clusters found near the sting of the Scorpion. M6 is about 1600 light years away and M7, about 980 light years.

Wide-field Infrared capture of the stars.

Omega Centauri (NGC 5139) is the brightest and largest of approximately 150 globular clusters orbiting the Milky Way. It is so bright it was labelled as a star on early sky charts by Ptolemy and is one of the few objects in the sky that carries both a star designation and an object catalogue designation. Omega Centauri shines with the luminosity of a million suns and is relatively close to us, only 15,800 light years away. It contains approximately 10 million stars and some theories suggest it could be the remnant core of a galaxy that is merging with the Milky Way.

The Sombrero Galaxy (M104 or NGC 4594) is an almost edge on barred spiral galaxy about 30% the size of the Milky Way, 28 million light years away. Its central black hole is about one billion times the mass of our Sun, which makes it one of the largest black holes found so far in the heart of a galaxy. The Sombrero Galaxy is situated within the constellation Virgo on the border with Corvus. It requires a moderate sized telescope and will appear as a small smoky smudge.

47 Tucanae (NGC 104) is a globular cluster second only to Omega Centauri. It sits beside but is unrelated to the SMC in the constellation Tucana. It can be easily seen away from city lights with the unaided eye due to its very dense star core. 47 Tucana is approximately 15,000 light years from us.

Special Events

A dense galaxy cluster.

T Coronae Borealis (T CrB) the Blaze Star may brighten suddenly. Located low in the northern sky just after sunset this month lies the small constellation of Corona Borealis – the Northern Crown. It is not normally of significant interest to those in the Southern Hemisphere – until now. While it cannot be guaranteed, a star within the constellation, designated T Coronae Borealis (or T CrB), may brighten suddenly as a nova. Nova means 'new', so this star, which is normally too faint to see, brightens in just a few hours to become equal to the fourth brightest star in the Southern Cross (called Delta Crucis). To the eye it is a 'new' star in the sky. Why? T CrB is composed of a huge red giant star and a tiny white dwarf star, which is about the size of the Earth but with more mass than the Sun. Gas is drawn off the giant onto the dwarf by gravity. Every 80 years or so the extra mass triggers an enormous and very bright thermonuclear explosion on the surface of the dwarf – but not so enormous as to destroy the white dwarf totally in a supernova.

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Sydney Observatory

Open for pre-booked tours, located on Gadigal land, a national place of connection and scientific research. The site is undergoing heritage conservation works.

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