Skynotes: April 2026

Our crowded corner of space

An impression not-to-scale of Low Earth Orbit debris at altitudes up to 2000km. Three quarters of all active operational satellites are also in this region which gives them high resolution for studying Earth resources and features. Despite their high orbital speed, their multiple passes allow for rapid and frequent downlinking of data to ground stations, and for continuous communication or internet coverage. / Source: ESA

We know Earth is surrounded by thousands of active and inactive satellites, and tens of thousands of pieces of orbital debris (aka 'space junk'), but the accelerated growth in satellites providing global communications and internet coverage, especially in Low Earth Orbit (LEO), raises serious and worrying issues for astronomy. 

Now that SpaceX has placed over 10,000 satellites in orbit, we may wonder what is Earth’s safe orbital ‘carrying capacity’. Over 20 corporations have launched communications satellites into Low Earth Orbit (LEO). Some have also been placed into Medium Earth Orbit (MEO), such as GPS systems at 20,000km, and geostationary satellites in High Earth Orbit (HEO) at 36,000km. In terms of the number of current satellites, by far the majority are from SpaceX Starlink, followed by lesser numbers by OneWeb (UK), Amazon Leo, SpaceX Starshield and Xingwang (China).

SpaceX has approval from US regulators for around 42,000 more LEO satellites. While plans from others, such as ESpace, seem more like business hopes or politicking, the overall trend across the sector is accelerating with more parties entering the market. And with the growth of terrestrial data centres, some corporations intend on satisfying that rising demand by creating space-based orbiting data centres. SpaceX’s own ambition is to launch perhaps a million satellites into LEO.

Once ‘constellation’ referred only to star patterns but now it increasingly covers fleets of satellites in Earth orbit. Other problems are rising as well. LEO satellites do not last forever and those that inevitably leave orbit and burn up on re-entry are said, on average, to leave a residue of around 30kg of aluminium oxide in the upper atmosphere raising questions of this being an “uncontrolled chemical experiment”. And while amateur and professional astronomers wrestle with worsening terrestrial light pollution, compounding their problems they now regularly report image pollution from satellites that detract from sensitive telescope observations.

It is not just in optical astronomy either. A disturbing pattern is emerging for radio astronomy. In one example, researchers using Australia's Square Kilometre Array SKA-Low facility in Western Australia, have reported up to 30% of their data was effected by electromagnetic interference from SpaceX satellites in frequencies that should otherwise be free from such radio pollution.  

Explore:

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Melbourne Sun times¹

¹ Daylight Savings time ends 3am, Sunday 5 April, with clocks turned back 1 hour.

² When the sun is at its highest, crossing the meridian or local longitude. 

Moon Phases

Moon Distance

Tuesday 7th is lunar apogee (furthest from Earth) at 404,970 km. 

Sunday 19th is lunar perigee (nearest to Earth) at 361,633 km.

Planets

Mercury is visible early in the month in the eastern sky from around 4:20am before fading by sunrise. It will appear a little earlier each morning before it finally is lost to view as it moves behind then Sun.

Venus will become visible again by the 18th as it emerges from the Sun when it will be in the north-west from around 6pm before setting by 7pm.0am.

Mars will return to our skies later this month after its passage behind the Sun. On the 18th the Red Planet will be in the east before dawn from 5am and then fade by sunrise.

Jupiter will be visible in the north from 6:15pm early in the month before setting in the west around 11pm. During the month it will rise and set a little earlier each night.

Saturn will become visible again by the 20th in the eastern early morning skies from around 5am before being 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 to 25th peaking on the 22nd to 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 an apparent circle around the South Celestial Pole as Earth rotates on its axis, half the circle during the night when visible and the other half during daytime.

In the North to 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.

Below Orion and drawing closer to the horizon during the month is the Hyades, an open group of stars that form a sideways wedge or V. This is the triangular head of Taurus, the bull, with his ‘angry eye’ as the red-giant star Aldebaran on the corner.

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. Here are some of the brightest passes expected this month over Melbourne and Central Victoria:

Morning

Friday 3rd 6:57am to 7:04am, South-West to North-East.

Saturday 4th 6:11am to 6:16am, South-South-East to East-North-East.

Evening

Saturday 11th 7:33pm to 7:37pm, North-West to South-South-East

Sunday 12th 6:46pm to 6:52pm, North-North-West to East-South-East

Thursday 30th 7:00pm to 7:04pm, South-West to North-East

Heavens Above gives predictions for visible passes of space stations and major satellites, live sky views and 3D visualisations. Be sure first to enter your location under ‘Configuration’.

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