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The casual observer

As May brings us into the second half of Djeran the days continue to draw in and sunset is getting earlier every day. Isn’t it fantastic? Fittingly, Orion, the great hunter of the sky and the symbol of Australian summer night sky is sitting low in the western sky after sunset and is gone by 9pm. This is your last chance to get a decent look at this constellation before it starts to get lost in the sunset next month.  

High up above you can see some of the lesser-known constellations in Australia, with Hydra and Corvus up there. Corvus is quite easily recognisable, and Hydra might take a little more work to see. A monthly reminder that the Argo Navis is still up there in the southwest, made up of Carina, Puppis and Vela. You can go out and look at the Argo Navis, and then turn around and look at hydra and Corvus. 

Image: Hydra, Corvus and the Argo Navis. 

Credit: Stellarium 

The Eta Aquarids meteor shower peaks on May 5. This is a vibrant meteor shower emanating from the constellation of Aquarius. These meteors travel fast across the sky and actually originate from Halley’s Comet, having been stripped off the parent body centuries, if not thousands of years ago. 

It’s easy to get philosophical. The comet is likely older than the Earth, and, after billions of years in the cold storage of distant space, a chance gravitational encounter sent it tumbling into the inner solar system where it has hung out for the past several thousand years, reappearing every 80 years or so. In one of its more recent passes, some of the surface material of the comet was ejected as debris and, after drifting in space for a few more centuries, it finally reached Earth. Then, seconds before reaching the ground it hits the atmosphere and burns up, visible to your eye for a fleeting fraction of a second. If you are out there to see it. 

Image: Apparent location of Eta Aquarid meteor shower, with Saturn and Mars visible as well. 

Credit: Stellarium 

The best time to view this meteor shower is before sunrise on May 5 or 6. The Waning Gibbous Moon is rising not long after Aquarius, so this may hamper your viewing a little bit, but in good conditions you might see a meteor every few minutes. If not, the spectacle is nicely backdropped by Saturn and Mars that you can also admire.  


Blue Moons and Disappearing Space Stations

There is a Blue Moon of sorts this month. May 2024 has two Last Quarter Moons, on May 1 and May 31. When there are two Full Moons in a month, we call it a “Blue Moon”, but there isn’t really any special name for two Last Quarter Moons in a month even though it happens just as often (or just as rarely, perhaps). Either way it’s pretty neat. In its Last Quarter phase, the Moon rises at midnight and sets at midday, so no matter your sleep schedule there’s a chance to get a glimpse of it.  

If you look at the table of ISS sightings below, on May 3 you can see the ISS flyover will disappear at 50 degrees above the horizon. If you are watching this flyover, rather than seeing the space station appear, pass overhead, and then satisfyingly drift off over the horizon, the bright light you will see above will just fade away in the middle of the sky. What’s happening is that the station is passing into Earth’s shadow. When we see satellites, we are seeing reflected sunlight – satellites don’t actually give off much of their own light. Granted, there are some lights on board the ISS, but not bright enough to be seen from this distance. It’s all reflected sunlight, so when the station goes into Earth’s shadow it just disappears from view, and that’s the end of your observations. 


ISS sightings from Perth 

The International Space Station passes overhead multiple times a day. Most of these passes are too faint to see but a couple of notable sightings* are: 

Date, time  Appears  Max Height  Disappears  Magnitude  Duration 
3 May 7:17 PM  10° above SW  50°  50° above SW  -3.0  2.5 min 
6 May 6:26 PM  10° above SW  50°  10° above NNE  -2.8  6.5 min 

Table: Times and dates to spot the ISS from Perth 

Source: Heavens above, Spot the Station 

*Note: These predictions are only accurate a few days in advance. Check the sources linked for more precise predictions on the day of your observations. 

Phases of the Moon

Last Quarter

May 1

New Moon

May 8

First Quarter

May 15

Full Moon

May 23

Last Quarter

May 31

Last Quarter

May 1

Dates of interest

  1. Star Wars Day

    May 4

  2. Eta Aquarids meteor shower peaks

    May 5

  3. Potential launch of Boeing Starliner crew flight test

    May 6

  4. Blue Last Quarter Moon

    May 31

Planets to look for

Pop Quiz: What planets can you easily see after sunset this month? Let Nathan Explosion answer that question for you.  

Video: He speaks the truth. 

Credit: Adult Swim, Metalocalypse 

The eastern morning sky is the place to look this month, with Mars, Saturn and Mercury making for good viewing. They are joined by the Moon in the first few days of the month as well. Mercury rises quickly for the first week of May before abruptly turning and heading toward the horizon again. It will be gone by the end of the month. Saturn gets higher above the horizon each day, while Mars drifts north.  

Image: Mercury, Mars Saturn and the Moon at 6am on the morning of May 6. 

Credit: Stellarium 

Jupiter, Venus and Uranus are lost in the glare of the Sun this month and basically unviewable. Neptune is out before sunrise as well, but you will need a telescope and an app to find it. 

Constellation of the month

Vela – The Sail

If you’ve read the March and April editions of The Sky Tonight you knew this was coming. Vela is a medium sized constellation visible in the southwestern sky during May evenings. It represents the sail of the Argo Navis, the great boat in the sky, and its inclusion here completes our coverage of this mighty star pattern. 

Image: Vela and the Argo Navis. 

Credit: Stellarium 

Vela is home to the Vela Pulsar, a rapidly spinning neutron star that formed from a supernova that exploded 12000 years ago, also forming the Vela Supernova Remnant. With about 1-2 solar masses of material squeezed into a space 20km across, neutron stars are some of the most extreme objects in the universe. The intense magnetic field of the star causes beams of radio waves to shine from the star’s magnetic poles. As the star spins, these beams can sweep over Earth and we see it as a regular pulse of radio waves from the same point on the sky, hence the name pulsar.  

Image: Chandra image of the Vela Pulsar with jets clearly visible. 

Credit: NASA/CXC/Univ of Toronto/M.Durant et al; Optical: DSS/Davide De Martin 

Pulsars are known to form from the collapsing core of high mass stars. Much the same way that an ice skater bringing their arms in to their body allows them to spin faster, as the core of a large star shrinks down to 20km across it spins much faster. For its enormous mass and decent size, the Vela Pulsar spins 11 times per second, as determined by the number of radio pulses received from it per second, each pulse representing one of the beams of radio waves emanating from the stars magnetic poles sweeping across Earth. You can hear the playback of various pulsars at this link 

Not to be outdone, the brightest star in Vela, Gamma Velorum, also known as Regor, is the 30th brightest star in the night sky and is actually a quadruple star system consisting of a pair of binary stars. The brighter pair, Gamma Velorum A, consists of a 28 solar mass blue supergiant star and a 9 solar mass Wolf-Rayet star separated by a mere 180 million km (only slightly further than the Earth-Sun distance) and orbiting each other every 11 weeks. Together they emit more than 500000 times as much light as the Sun, though most of this is in the UV spectrum. 

Image: The position of Regor in Vela 

Credit: Stellarium 

Wolf-Rayet stars are some of the most unusual stars in the universe, perhaps almost as unusual as neutron stars. They are characterised by their lack of hydrogen in their atmosphere, abundance of heavy elements, and strong stellar winds. These properties are thought to be caused by the strong convection within high mass stars powered by helium core fusion, which mixes the layers of the star together and ejects enormous quantities of material away. The 9 solar mass Wolf-Rayet star in Gamma Velorum is thought to have once been closer to 40 solar masses, much of which it has since shed. 

Object for the small telescope

IC 2602 – The Southern Pleiades 

The Southern Pleiades is an appropriately named open cluster of stars in the constellation of Carina and at a magnitude of about 1.9 it is easily visible to even the naked eye. Consisting of many blue stars, the cluster bears a similar resemblance to the Pleiades Cluster in the constellation of Taurus. The Southern Pleiades contains about 75 stars located about 500 light years away, and like the Pleiades, contains young stars, in this case only about 13 million years old.  

Image: The Southern Pleiades up close. 

Credit: Tel Lekatsas, CC BY 2.0 Deed 

The cluster contains the bright star Theta Carina, which forms one of the points of the Diamond Cross asterism. 

Image: The Southern Pleiades circled and the Diamond Cross. 

Credit: Stellarium 

Australian Astronauts and Rockets, Boeing Starliner’s Crew Flight and Voyager 1’s Misadventure 

There is a lot happening in the space world this month, so let’s inadvisably try and fit it all into one short article. 

The Australian space program has taken a step forward with Katherine Bennell-Pegg graduating as an Australian Astronaut. The history of Australian astronauts goes back to Phillip K Chapman in 1967, but is quite light on numbers, and always contains the technicality of “Australian-born, American Astronaut” or something similar. After 14 months of training in Germany, covering things like robotic arm manipulation, underwater space walks and parabolic flight weightless simulators, Bennell-Pegg has become the first person to complete astronaut training under the Australian flag. It’s not clear at the moment if or when she will be going to space, but time will tell. 

Image: Katherine Bennell-Pegg completes astronaut training with the European Space Agency. Straight to the pool room! 

Credit: Katherine Bennell-Pegg 

Speaking of Australian space capability, Gilmour Space Technologies will soon launch the Eris Block 1 rocket on its first orbital test flight. This is the first Australian made rocket designed to go to orbit. 

Image: The Eris rocket being loaded vertically in preparation for launch.  

Credit: Gilmour Space Technologies 

The 25m tall rocket is capable of putting up to 305kg into a 500km altitude Low Earth Orbit, with future versions planned to increase these capabilities. A planned launch on May 4 from Bowen Orbital Spaceport in northern Queensland was cancelled due to lack of a launch permit from the Australian Space Agency but watch this space. 

Image: Stay tuned 

Credit: Gilmour Space Technologies 


Combining the topics of astronauts and experimental spacecraft, the Boeing Starliner is finally about to undertake its first crewed test flight. Commissioned by NASA in 2014, the history of the Starliner is long and tortured. During the first uncrewed test flight in 2019, two critical software errors almost resulted in mission failure, and follow up investigation revealed 80 separate problems with the spacecraft, all of which were addressed and corrected by Boeing before new problems with the propulsion system were discovered in 2021. Finally, a second uncrewed test flight was launched to the International Space Station in May 2022, largely successfully.  

Image: The Boeing Starliner sitting atop the Atlas V launch vehicle. 

Credit: NASA/Joel Kowsky, CC BY-NC-ND 2.0 Deed 

When preparing for the crewed test flight in mid 2023, it was discovered that the parachutes used to return Starliner from space were not strong enough to do so safely, and that a certain type of tape used to secure wiring in the vehicle was flammable under certain circumstances. Fixing these problems pushed the launch back by another year and now the time has come. 

The test flight is planned for May 7 and will carry NASA astronauts Barry Wilmore and Sunita Williams to the International Space Station on a 1-week mission. 

Further from home, you might have heard that in November last year, the Voyager 1 spacecraft started sending garbage information to Earth. Currently located about 24 billion km from Earth, Voyager 1 is the most distant human made spacecraft from us, meaning that the light travel time round trip is about 2 days. A long time to wait to troubleshoot an uncooperative robot. NASA operators narrowed the problem down to a failed chip on one of Voyager 1’s computers called the Flight Data System, responsible for collecting data from all the science and engineering instruments on board the craft and packaging it to be sent to Earth. 

Image: Artist’s impression of Voyager 1 in space. 

Credit: Caltech/NASA-JPL 

The broken chip stored some code that the computer used to package the science data. Broken chip means no code equals bad data, so the engineers cleverly divided the code up and saved it to different parts of the computer, being careful to reference where each piece was newly stored. The result is Voyager 1 is now sending basic engineering data back to Earth again. In coming months, NASA will continue to work on the problem to allow the spacecraft to start sending science data back again. 

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