APRIL 2024

Moon phases

Third Quarter Tuesday 2nd
New Moon Tuesday 9th
First Quarter Tuesday 16th
Full Moon Wednesday 24th

Moon distances

Lunar perigee (closest to Earth) is on Monday 8th at 358,850 km. Lunar apogee (furthest from Earth) is on Monday 20th at 405,623 km.

Planets

Mercury is in front of the Sun this month (its inferior solar conjunction) and not visible.

Venus rises in the east around 5:30am early in the month and a little later each morning, but fades in the dawn light by 6:20am.

Mars is visible high in the east from 3:40am, a little later each night, before fading in the morning light by around 6am.

Jupiter is about to move behind the Sun for its superior solar conjunction, but can still be seen high in the north-west from around 3:40am before fading by 6am in pre-dawn light. By late April it will no longer be visible.

Saturn can be seen from 3:40am early in the month in the east, and then a little earlier each night, before it is lost in the dawn light.

Meteors

April's main shower, The Lyrids, is centred near the bright star Vega low in the north at 3am. It is active from 16th – 25th peaking on the 22nd-23rd. Better placed is the Pi-Puppids associated with Comet Grigg-Skjellerup which peaks on 24th centred low in the south-west near Canopus in Carina.

Stars and constellations

In the south

The Southern Cross can be found on its side in the south-east with the Two Pointers below. To the right of the Cross, in the south-western sky, is the star Canopus, the second brightest star in the night sky. Low in the south is Achernar, the head of the river Eridanus. Achernar never sets in Melbourne and is called a circumpolar star as it moves through a half-circle around the South Celestial Pole during the night as Earth rotates on its axis.

Here is the night sky taken by the AAT of the region containing the Southern Cross or Crux and the nearby Pointers. The Anglo-Australian Telescope forms part of the Australian Telescope Observatory (AAO) at Siding Spring in NSW which hosts a variety of telescopes and detectors studying the sky. The image above reveals a region of the galaxy densely packed with millions of stars. Their true colours, seen in long exposures like this one, reveal their surface temperature – blue-white for the hottest stars, orange-yellow for those cooler, and red for the coolest.

The dark Coal Sack dust cloud sits at centre with the five stars of the Southern Cross, and to the left are the two Pointers, Alpha and Beta Centauri, with the brighter at far left being Alpha Centauri, a triple star system and our Sun's immediate neighbours.

In the south-west

If a dark location you can see the Large and Small Clouds of Magellan, two small neighbouring galaxies to our own Milky Way. They appear as irregular fuzzy patches isolated from the broad band of stars that runs across the sky which is our edge-on view of own galaxy.

In less light-polluted skies you can also see in the Milky Way several dark regions that are vast clouds of dust. Whilst we may see a few foreground stars, the dark areas behind obscure our view of more distant stars of the galaxy.

In the west

Orion, the hunter, is in the west lying almost on his side with the red-giant star Betelgeuse as one of his shoulders. The three bright stars that form an obvious line are Alnitak, Alnilam and Mintaka. They mark his belt and also conveniently the base of the local 'Saucepan' asterism. The handle of the saucepan is Orion's scabbard which hangs from his belt. Continuing the belt stars above and a little to the right we reach Sirius, the brightest star in the night sky and principal star in Canis Major (greater or larger dog) which is one of Orion's hunting dogs. Below Sirius in the north-west is Procyon which marks the position of his lesser or smaller dog Canis Minor.

In the north

In the north but upside down from our southern hemisphere perspective is Leo, the lion. This constellation is easily recognised by the hook shape (or inverted backwards question mark) of stars that forms the mane on the lion's head and shoulders.

To the left of Leo and close together are the two bright stars Castor and Pollux, the principal stars in the constellation of Gemini, the twins which appears upside down as well from southern latitudes.

In the east

Later this month and into May the spectacular constellation of Scorpius will begin its return to our evening skies. This is one of the largest constellations and when it appears low in the east you can easily identify to the left its long curving tail leading to its body containing the red-giant star Antares marking its heart, and to the right its pincers reaching out.

International Space Station

ISS orbits every 90 minutes at an average distance of 400 km appearing like a bright star moving slowly across the night sky. Heavens Above gives predictions for visible passes of space stations and major satellites, live sky views and 3D visualizations. Be sure to first enter your location under 'Configuration'.

On this day

1st 1948, Alpha, Bethe and Gamow publish their famous paper on the 'hot Big Bang'.

2nd 1845, Fizeau and Foucault take the first photograph of the Sun.

3rd 1966, Luna 10 (USSR) became the first spacecraft to orbit the Moon.

7th 1973, Pioneer 11 (USA) probe launched to Jupiter and Saturn.

8th 1732, birth of David Rittenhouse who determined Earth-Sun distance of 150 million km.

9th 1959, NASA's first cohort of astronauts, "the Mercury 7", are announced.

11th 1905, Einstein's 'Special Theory of Relativity' is published.

11th 1970, Apollo13 (USA) was launched on its ill-fated mission.

12th 1633, Galileo's trial by the Catholic Inquisition, on the question of a sun-centred solar system, begins in Rome.

12th 1961, Yuri Gagarin (USSR) became the first human in space orbiting Earth for 108 minutes in Vostok 1.

12th 1981, Columbia (USA) was the first space shuttle to be launched.

14th 1629, birth of Christiaan Huygens who explained Saturn's rings and discovered its largest moon Titan.

16th 1495, birth of Petrus Apianus who established that cometary tails at all times point away from the Sun.

18th 1971, Salyut 1 (USSR), the first space station, was launched.

19th 1975, first Indian satellite, Aryabhata, is launched.

21st 1990, the Hubble Space Telescope (HST) was launched on the space shuttle Discovery.

23rd 1992, COBE satellite reveals microwave temperature variation across universe.

27th 2002, final telemetry received from probe Pioneer 10 (USA).

28th 1900, birth of Dutch astronomer Jan Oort whose name is given to a vast cloud of icy objects thought to orbit the sun well beyond the Kuiper Belt.

28th 2001, American Dennis Tito became first space tourist paying the Russian Space Agency $US20 million to travel on a Soyuz craft to the ISS for an 8-day journey.

30th 1006, brightest supernova ever recorded is seen in the constellation of Lupus.