Events

Melbourne sun times

§ When the Sun is at its highest, crossing the meridian or local longitude

Moon phases and distances

This month’s Moon apogee (furthest from Earth) is on Mon 2nd at 404,410 km and perigee (closest to Earth) is on Tue 17th at 369,124 km.

Planets

Mercury has moved behind the sun and so not visible this month.

Venus is bright in the north-west before setting around 8.30pm. It is the second brightest object in the night sky (after the moon), our closest sunward neighbour, and thickly shrouded in cloud that reflects sunlight. It’s both the ‘morning’ and ‘evening’ star. Explore why in a 2020 virtual planetarium show from Rochester Museum and Science Center that uses the free programs Stellarium (in a northern hemisphere view) and NASA’s Eyes on the Solar System.

Mars is not visible this month and is about to pass behind the sun for some time. The Red Planet will be lost to our view for the rest of the year before returning in the east in the early morning skies next January.

Jupiter, the third brightest object in the night sky, is easily seen this month from around 7pm as it rises in the east, moves across to the west and fades by 7am in the early morning light.

Saturn, fainter and preceding Jupiter, the second largest planet can be seen rising in the east about 6pm before it too travels across the northern skies to set in the west around 6am.

Meteors

This month’s major meteor shower is the Perseids which peaks on the 13-14th although not strong in the southern hemisphere. They are fast, bright, can leave persistent trails, and come from a point below the north-east horizon in the northern constellation of Perseus. These meteors result from Comet Swift-Tuttle which passed near the Sun in 1991 leaving a trail of particles for the Earth to regularly pass through.

Stars and constellations

In the north

This month’s evening skies show Virgo and Spica (Alpha Virginis), the 15th brightest star at night and 262 light years away, have moved towards the west, while Leo has largely disappeared below the north-western horizon. However, Libra (the weighing scales) is high in the north and in the north-east is Aquila (the eagle) with its principal star Altair (Alpha Aquilae), the 12th brightest star at night and 17 light years from us.

In the east

Very high in the east after sunset and slowly moving overhead during the night as our planet rotates to the east is Scorpius with its impressive curving line of stars. The central star of the three that form the scorpion’s body is the red giant Antares (Alpha Scorpii) at 34 light years and 16th brightest star at night. Rising behind and following during the night is the centaur Sagittarius with its bow and arrow forming the famous Teapot asterism.

In the south

Standing high in the south-west is Crux, or the Southern Cross. On a moonless night, and certainly away from city lights, can be seen the dark patch known as the Coal Sack nebula, a vast region of interstellar dust that blocks our view of more distant stars. To its left are the Pointers (Alpha and Beta Centauri), the brightest and second brightest stars in the constellation of Centaurus which is the other horse-human hybrid from ancient Greek myth.

Alpha Centauri is also known as Rigel Kentaurus (‘foot of the centaur’) and is the 4th brightest star in the night sky. Until very recently it was thought to be our sun’s nearest neighbour at 4.37 light years. Although we see one star it is in fact two, Alpha Centauri A and Alpha Centauri B in close elliptical orbits around their barycentre or common centre of mass. The pair are not unlike our sun - one very similar and the other a little cooler and smaller. The existence of two planets, one around each star, is suspected but as yet unconfirmed.

Of special interest is the faint small red-dwarf star Proxima Centauri (designated Alpha Centauri C) that lies a considerable distance away but seemingly bound to the others. We now understand Centauri to be a triple star system.

Proxima, as the name suggests, is currently the closest star to our sun at 4.24 light years and hosts at least two planets. Proxima Centauri b (discovered in 2016) is a little over Earth mass, orbits swiftly much closer than Mercury does to our sun, and is presumed to be tidally locked with only one face turned to its star. The second planet Proxima Centauri c (discovered in 2016) is about seven Earth masses, lies further out in a 5-year orbit, and may possess a huge ring system.

Returning to our August night skies…

Low in the south-east is the 10th brightest star Achernar (in the constellation of the Eridani, the river) which sits at 144 light years from Earth, and in the south-west lies the 2nd brightest star Canopus in the constellation of Carina (the keel) at 313 light years. From our southern latitude both of these stars never disappear below the horizon.

These two stars provide are a handy example of a key relationship in astronomy and observing the night sky. A star’s apparent brightness depends not only on its distance from us, but also its luminosity (how much light it emits). Luminosity is determined by size (radius) and surface temperature both of which can change over the life of a star as it undergoes stages of stellar evolution. Canopus is almost two and a half times further from us than Achernar but its luminosity is well over three times higher. On a league table of brightness as observed from Earth the energy output of Canopus easily wins over Achernar’s closeness to us.

In the west

Low in the north-west is Arcturus, the 3rd brightest star at night and 37 light years from us in the constellation of Bootes (the herder or plower).

Corvus (Latin for crow) sits squarely in the west in the evening this month. In ancient Greek mythology, however, this sacred bird is a raven that perches on the back of Hydra (the sea serpent). The serpent’s nearby head is a little higher up in the west and marks one end of a long narrow body that snakes to the horizon in the longest of the traditional 88 constellations.

This set of constellations was agreed upon by the International Astronomical Union (IAU) almost a century ago and drew heavily on European, Mediterranean or Middle Eastern traditions, sources and catalogues of the past. However, in this century new or supplementary names for celestial objects, as well as their stories, are increasingly being introduced from many cultures around the world to complement those already used widely in astronomy.

First Peoples night sky

First Peoples across Victoria and around Australia have ancient practices of night sky observing and story-telling that relate to the origin of things, the seasons, animals and plants, the local landscape, and the climate in different parts of the continent. These diverse and rich traditions have great cultural importance as knowledge and understanding is passed from generation to generation.

As for new names two recent First Peoples examples are from the Wardaman tradition of Northern Territory – the naming of the fifth brightest star in the Southern Cross (Epsilon Crucis) as Ginan, and the equally bright star in Scorpius (Epsilon Scorpii) as Larawag. This growing trend of global recognition can be seen in new star names here in Australia, and also from other cultures around the world.

In the evening this month the Milky Way, seen from dark locations away from city lights, ranges from south-west to north-east with the well-known emu’s body its dark regions (Coal Sack as its head, the Pointers as its neck, and further dark regions its body and legs).

In some stories the dense starfield of our galaxy is the Warring or smoke from campfires of the Nurrumbungittias, the ancient beings who created the land.

As mentioned last month the star Canopus in the south-west and the second brightest star at night, is Wah the male crow from north-west Victoria. His partner the female crow Cullugulloric Wah flying nearby in the low south-west is the massive star Eta Carinae in the constellation of Carina (the keel). This hypergiant star is some 8,500 light years away and embedded in a complex and dynamic nebula. Sadly, it is no longer visible to the naked eye as over time it has shed gas and faded – a change in brightness carefully observed and reflected in some First Peoples stories as Cullugulloric Wah grew tired looking after her children.

Recognition of First Peoples Star Names
New Star Names From Around the World
First Peoples of Australia Astronomy
Australian Indigenous Astronomy

International Space Station

At a distance of about 400km the ISS completes an orbit every 90 minutes and appears as a bright object that moves slowly across the night sky. There are many visible passes expected this month over Melbourne and Central Victoria:

Morning

Mon 9 6.29am-6.35am West-South-West to North-North-East
Tue 10 5.44am-5.48am South-West to North-East

Evening

Wed 18 7.18pm-7.22pm North-West to East-South-East
Thu 19 6.30pm-6.36pm North-North-West to East-South-East

Tiangong Space Station

On 29 April this year the Chinese Manned Space Program launched into orbit the core module Tianhe-1 (Harmony of the Heavens) for its planned Tiangong Space Station (Heavenly Palace). On 17 June Shenzhou-12 (Divine Vessel) launched with a crew of three to dock with the core module. Once completed the station will have one-fifth the mass of the ISS. It will be faint but it may be possible to see the core module pass overhead. Here are two of the best opportunities this month:

Evening

Wed 3 7.04pm-7.08pm West-North-West to East-North-East
Wed 11 6.59pm-7.03pm West-South-West to East

Heavens Above gives predictions for visible passes of both space stations and major satellites.

On this day

3^rd 2004, the MESSENGER (USA) mission to Mercury was launched.

4^th 2007, Phoenix (USA) Mars lander was launched.

5^th 1998, NASA Near Earth Object Program is created to detect and catalogue asteroids that approach Earth.

5^th 1939, first person to walk on the moon, American Neil Armstrong, is born.

6^th 2012, the Mars rover Curiosity lands on the red planet.

6^th 1996, a meteorite from Mars discovered in Antarctica is said by NASA to contain possible microfossils of bacteria.

7^th 1959, Discoverer 1 (USA) returns the first satellite images of the Earth.

10^th 1675, Royal Greenwich Observatory is established east of London.

10^th 1990, Magellan (USA) arrives at Venus and begins radar mapping of its surface.

12^th 1877, Astronomer Asaph Hall at the US Naval Observatory discovers Mars’ tracks are clearly eviden.t 12.6km diameter moon Deimos.

13^th 1898, Eros, the first near-Earth asteroid is found by Carl Gustav Witt.

17^th 1970, Soviet probe Venera 7 is launched to Venus and will send first pictures from the surface of another planet after landing on December 15th.

18^th 1877, Mars’ 22.5km diameter moon Phobos is discovered by Asaph Hall.

18^th 1868, new element ‘helium’ is found by Pierre Janssen from analysis of the Sun’s spectrum. It is now known to be the second most abundant element in the universe after hydrogen.

19^th 1960, two dogs, Belka and Strelka, are launched aboard Sputnik 5 (USSR), and successfully returned to Earth.

19^th 1646, birth first Astronomer Royal John Flamsteed who catalogued 3000 starts.

20^th 1975, launch of Viking 1 (USA), first probe to land on and study Mars.

20^th 1977, Voyager 2 (USA) launched to the planets of the outer Solar System.

22^nd 1989, Voyager 2 (USA) discovers positive evidence for Neptune’s rings.

24^th 2006, first formal definition of ‘planet’ is debated and vote upon by International Astronomical Union in Prague resulting in dwarf planet status for Pluto.

25^th 1609, Galileo demonstrates to the Venetian Doge and officials his improved version of the newly invented telescope.

31^st 1913, birth of famous British radio-astronomer Bernard Lovell.