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The casual observer

The two giants of the skies, Orion and Taurus, are getting low in the sky. So now is your time to see them before they depart for winter.

It’s also your last chance to see the Pleiades, also known as The Seven Sisters, sitting low in the west in early April, just below the waxing crescent Moon, and then slipping below the north western horizon by the end of the month.

Coming up from the eastern horizon is Virgo. In mythology, Virgo represents fruitfulness and fertility, and the constellation is no different. Telescopes reveal Virgo as home of the great Virgo galaxy cluster, made up of over 1,000 galaxies lying some 65 million light-years away!

The arrival of Virgo also signals the change of season. In WA, the start of autumn is closely followed by the Noongar season of Djeran.

See if you can spot some of the famous stars of our April night sky like Spica, a white-blue star, the brightest of the Virgo constellation, and Menkent, an orange giant that marks the shoulder (or head) of Centaurus.

To the right of Menkent (and up a little) is Alpha Centauri, the brightest star in the constellation Centaurus, and the nearest star system to our sun.

And of course, April is a great time to see the Southern Cross (aka Crux). So pop out from 7.30pm each night and face south to catch this famous sight. Look just above Alpha Centauri and expect it to be lying on its side!

Constellation map of the April night sky, showing Menkent, an orange giant that marks the shoulder (or head) of Centaurus, Alpha Centauri and Crux (or the Southern Cross) just to the left of Musca

Image: Constellation map of the April night sky, showing Menkent, an orange giant that marks the shoulder (or head) of Centaurus, Alpha Centauri and Crux (or the Southern Cross) just to the left of Musca.

Phases of the Moon

New Moon

April 1

First Quarter

April 9

Full Moon

April 16

Last Quarter

April 23

New Moon

April 1

Dates of interest

  1. Conjunction of the Moon, Castor and Pollux.

    April 9

  2. Conjunction of the Moon and Spica.

    April 16

  3. Lyrids meteor shower.

    April 22

  4. Lyrids meteor shower.

    April 23

  5. Alignment of Saturn, Mars, Venus, Jupiter and the Moon.

    April 28

  6. Partial solar eclipse.

    April 30

Planets to look for

Venus, Jupiter, Saturn, and Mars will be putting on a show in the early morning eastern sky all month – but you’ll need to be up bright and early (read that as ‘before sunrise’) to see them.

This culminates with a line of planets capped by the Moon which will be spotted in the early hours of 28 April. From highest in the sky to lowest in the east: Saturn, Mars, Venus, Jupiter and the Moon will form a large line pointing eastward. For those with telescopes, Neptune can also be observed, slightly higher in the sky than Venus.

Trailing this alignment is the Sun, bringing Mercury along with it.

Constellation of the month


It’s up there in the north, to the right of Orion, and it’s bright. This month we can spot the constellation of Gemini, also known as ‘The Twins’. The Twins, of course, being Castor and Pollux, who appear in many stories from ancient Roman and Greek mythologies. They are famed for being two heroes who joined Jason on his voyages on the Argo.

Constellation of Gemini outlined in the April night sky

Image: the outline of the Gemini constellation in the April night sky. Credit: Stellarium

According to some myths, Castor was born mortal, son of Tyndareus, but Pollux was the son of Zeus and therefore immortal. When Castor was slain in battle, Pollux was inconsolable and asked to renounce his immortality. Zeus agreed, and now the two brothers are united in the night sky as the two brightest stars in the Gemini constellation.

You should see the two bright stars, one above the other.

Pollux, the bright star at the top, should look somewhat reddish/orange. Underneath it you should see Castor, a slightly bluish looking star that’s a little bit fainter.

Pollux and Castor represent The Twins’ faces, and about halfway back towards Betelgeuse, you should see a few more stars strewn about, and these represent their feet. Imagine they are standing sideways in our sky as we see them.

Castor is also known as Alpha Geminorum – and usually an alpha star is the brightest in its constellation. But Castor is the second brightest in Gemini, after Pollux (or Beta Geminorum).

A photo of Castor and Pollux showing their colour difference - Pollux (on the left) is a reddish/orange and Castor (right) looks blue

Image: A photo of Castor and Pollux showing their colour difference – Pollux (on the left) is a reddish/orange and Castor (right) looks blue. Credit: Rogelio Bernal Andreo

In a further twist, the ‘star’ that we call Castor is actually six stars which consists of three pairs of binary stars all orbiting each other in a complicated arrangement.

Pollux is a giant star, about ten times the size of our Sun. It has run out of fuel in its core and is swelling up in size as it starts to consume material surrounding its core. Pollux also has a nice close-to-home story: in 2006, astronomers discovered a planet orbiting Pollux. So the question arose … what should we call it?

Well, as this was happening, three Western Australian organisations – The University of Western Australia, Curtin University, and The International Centre for Radio Astronomy Research – were working together on a separate project called theSkyNet. This group suggested the name Leda, who was the mother of Castor and Pollux in the stories of Greek mythology. Unfortunately there’s already a moon of Jupiter called Leda, and an asteroid as well. So the name Thestias was suggested instead. Thestius was Leda’s father, and the name Thestias means ‘daughter of Thestius’ – aka Leda. So, scientists from Western Australia helped named a planet that lives 320 trillion kilometres away.

Object for the small telescope

HD162826 – A sibling star to the Sun

Our familiar star, it turns out, is not unique. Our Sun has a sibling—a sister-star that almost certainly originated from the same cloud of gas and dust.

The majestically named HD162826 is 15% larger than our Sun, and located 110 light-years away from us in the Hercules constellation – which is best seen from Perth at about 3am on 16 April, low in the northern sky.

Astronomers identified HD162826 in two ways. First, like with the Hyades cluster (see our March update), they used spectroscopy to determine what it is made of – and learnt that it is similar to the Sun.

Secondly, they noticed it is moving through the Milky Way Galaxy on a very similar path to the Sun. Tracing back the orbits of both, astronomers were able to determine that about 4.6 billion years ago, not long after the Sun formed, both stars were very close together, meaning there is a strong possibility that they are stellar siblings.

However, even though they are siblings, they are not exactly like. HD162826 is a bit bigger, and a bit hotter. Find out more in our latest season of our Audio Guide to the Galaxy that will be released throughout April.

How does the Russia-Ukraine war affect space?

Getting to space is difficult and expensive, so access to space has always been a litmus test of sorts for international co-operation. Even at the height of the Cold War, there was co-operation between NASA and Roscosmos. Today it’s difficult to predict how access to space will be affected.


How does it affect the International Space Station?

In a Twitter rampage, head of Roscosmos Dmitry Rogozin threatened: “Do you want to destroy our co-operation on the ISS … If you block co-operation with us, who will save the ISS from an uncontrolled deorbit and fall into the United States or Europe? … The ISS does not fly over Russia, so all the risks are yours. Are you ready for them?”

To which Elon Musk smartly responded:

But Rogozin may have a point. Even though it is typically more than 400km above the ground, there is still a tiny amount of air resistance that the station experiences. Given enough time, its orbit will eventually decay and fall back to Earth. To avoid that, the station’s orbit is periodically boosted by the Russian built Soyuz craft on a Progress resupply mission. Currently, the Soyuz is the only spacecraft that can boost the ISS.

Despite its immense size, the ISS is extremely flimsy. Boosting the orbit is not just a case of strapping a rocket to it and firing it up. The Soyuz has to pulse its engines in such a way as to cancel out any vibration introduced to the station. Despite Musk’s confidence, the SpaceX Dragon is not yet capable of boosting the ISS without extensive modifications and developments.

There is one more option, which is the Cygnus resupply craft. Fittingly, it’s capability to boost the ISS is to be tested soon.

ISS configuration as of Feb 2022 - with Crew-3 Dragon, Cygnus-17, Soyuz MS-19, Progress 80 and Progress 79 occupying separate areas

Image: One big family – the ISS configuration as of February 2022. Credit: NASA

Cygnus is operated by the US based Northrop Grumman. Unfortunately, Cygnus is launched on the Antares rocket, the first stage of which is built in Ukraine, and powered by Russian engines.

Northrop Grumman Antares CRS-11 Launch

Image: Northrop Grumman Antares CRS-11 Launch. To quote science communicator Scott Manley, “If only international politics was as easy as rocket science”. Credit: NASA/Bill Ingalls

It seems like Antares and Cygnus are not a solution for the time being. One possibility is launching the Cygnus on a SpaceX Falcon 9 but it’s too early to say if this could be achieved.

What about crewed flights?

This is where Russia stands to lose. Without access to the space station, Russia will have no way to have long term access to space science. There is speculation that they may partner with China on the Tiangong Space Station, but this is a long-term project that’s still very unclear.

The SpaceX Crew Dragon can launch astronauts to the ISS and, partnered with the Soyuz, NASA and Roscosmos, were in a position to engage in a rideshare program. This meant Russian cosmonauts could hitch a ride to the station on a Dragon, in exchange for astronauts to catch a ride on the Soyuz. NASA and ESA astronauts are no strangers to launching on the Soyuz, but there has never been a cosmonaut launched on a Dragon. So as far as crewed access to space, Russia will be left in the cold if the co-operation around the ISS breaks down.

NASA astronaut Scott Kelly trains in a Russian Soyuz simulator

Image: NASA astronaut Scott Kelly trains in a Russian Soyuz simulator. Credit: NASA/Bill Ingalls

Which brings us back to SpaceX …

Unfortunately for NASA, while SpaceX is an option for most of the problems, it is an ‘all the eggs in one basket’ solution. But a problem with the Falcon 9 could ground the rocket for months.

As far as competitors go, Boeing has consistently failed to deliver a capsule capable of transporting astronauts to the station. The plagued Boeing Starliner is years overdue and over budget and still requires a launch vehicle. This will probably have to be a Falcon 9.

Another competitor, Sierra Nevada, offers a promising alternative with their Dream Chaser space plane, but this is still in the development phase and has yet to make a single test flight to orbit. Again, it needs a launch vehicle. Again, this will probably have to be a Falcon 9.

Well, there is one alternative launch vehicles but again, it’s complicated.

United Launch Alliance (ULA) have an excellent reputation for providing extremely reliable launch vehicles. The Atlas V is their current signature rocket, with achievements such as launching the Perseverance Rover to Mars, the Boeing Starliner on its first test flight and most recently the GOES 18 weather satellite.

But there’s a problem. The Atlas V uses Russian built RD180 engines.

ULA was directed by the US government to phase out the Atlas V to remove the reliance on Russia for its space capability. ULA’s response was the Vulcan Centaur rocket, will be powered by locally manufactured BE-4 engines, built by Jeff Bezos’s aerospace company Blue Origin.

Unfortunately, Blue Origin failed to deliver the engines to ULA on time in 2017 when they were due … and still hasn’t. Recently, Jeff Bezos stepped down as CEO of Amazon to focus more on the trouble ridden Blue Origin (working there 2 afternoons a week). Fans of Bezos are confident he will be able to lead the company to deliver the engines.

Jeff Bezos in a Blue Origin uniform

Image: Jeff Bezos. Credit: ABC news

Meanwhile in the Scitech planetarium …

The dome has gone.


Yes, the iconic City West dome was removed on 28 March for updating.

But don’t fear! This icon of Perth will be reinstalled atop the Planetarium in late April 2022.

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