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The casual observer

As we enter the second half of Djeran it’s clear that the seasons are definitely changing. April brought with it some rainy and cloudy nights and we can expect more of the same. The flip side is this makes the clear nights all that more valuable. 

Scorpius is peeking up in the east after sunset and will dominate the night sky for the next six months. Correspondingly, Orion is setting in the west so be sure to take one last look before it goes. The hunter and the hunted forever chasing each other across the night sky. 

Image: Scorpius in the east during May. 

There is a partial lunar eclipse which begins at 11:14 pm on Friday May 5 and runs through to 3:31 am the following morning. This eclipse is the sister of the April 20 total solar eclipse in Ningaloo. The fact that eclipses occur in groups closely spaced in time is referred to as eclipse seasons. 

Eclipses happen when the Earth, Moon and Sun are all lined up, but are complicated by the fact that the Moon’s orbit around Earth is tilted with respect to the ecliptic by about 5 degrees. This means that at time of new or full moon, it is usually above or below the ecliptic and doesn’t quite line up with the sun in the sky, and we don’t get an eclipse every single month. 

 Image: The Moon’s orbit is inclined to the ecliptic. This is why we don’t get eclipses every month. 

However, at certain places along Earth’s orbit, the Moon’s orbit crosses the ecliptic at new and full moon, and this is when eclipses occur. In this case we had a total solar eclipse at new moon on Apr 20, and now a couple of weeks later the Moon has moved to the other side of the Earth and we are getting a lunar eclipse during full moon. Over the coming weeks, Earth will continue its orbit around the Sun far enough that the next new moon on May 19 will occur off the ecliptic and there will not be a solar eclipse, and the eclipse season has ended. 

Image: Partial lunar eclipse on May 5-6 

Credit: timeanddate 

The Eta Aquarids meteor shower occurs this month, peaking in the week centred on May 5. This shower should be viewed in the hours before dawn, and in good conditions you might expect to see a meteor every couple of minutes, though this will be complicated by the full moon around this time as well. The meteors in this shower come from Halley’s comet – fragments of dust that ejected from the comet centuries ago that are now contacting our planet, creating the bright streaks of light that momentarily draw our gaze. 

In case you missed it, there was a total solar eclipse in Exmouth on Apr 20. View the livestream here. Also, obligatory song. 

Phases of the Moon

Full Moon

May 6

Last Quarter

May 12

New Moon

May 19

First Quarter

May 27

Full Moon

May 6

Dates of interest

  1. Star Wars Day

    May 4

  2. Peak of Eta Aquarids meteor shower

    May 5

  3. Partial Lunar Eclipse

    May 5

  4. Jupiter, Moon and Mercury together in the pre-dawn sky

    May 18

  5. Venus, Moon and Mars together in west after sunset

    May 24

Planets to look for

Mars and Venus are still hanging in the northwest sky during the early evenings. Venus is moving noticeably higher as the month goes on and appears to get closer to Mars by the day. 

Saturn is rising in the east at about 2am. Be sure to give it a wave as you watch the Eta Aquarids meteor shower. 

Jupiter is visible in the east from 5:30 am onwards and is also joined by Mercury in the latter half of the month. The almost-new moon also makes a nice appearance alongside them on May 1. 

Image: Jupiter and Mercury in the pre-dawn sky joined by the moon on May 18. 

Constellation of the month

Libra the Scales 

Libra is a medium sized constellation visible during the middle parts of the year. A zodiacal constellation, the orbits of the planets and the moon pass through this part of the sky, as does the apparent motion of the sun. 

Libra was originally associated with Scorpius, as an extension of the stinging arachnid in the form of it’s claws. 

Image: Libra and Scorpius are neighbouring constellations in the sky. 

This association with Scorpius is manifest in the constellation’s three brightest stars Alpha Librae, Beta Librae and Gamma Librae, respectively known in Arabic as Zubenelgenubi (the Southern Claw), Zubeneschamali (the Northern Claw) and Zubenelhakrabi (the Scorpion’s Claw). 

Image: Star names in Libra 


Of interest this month, the Moon will be in Libra on the night of May 5-6 during which time the partial lunar eclipse occurs. 

The constellation really came into its own during the times of ancient Greece and Rome, where it was interpreted as the scales of Astraea, the Goddess of justice, who was associated with nearby Virgo in the sky. This interpretation as balancing scales is the one we are familiar with today. 

Libra is home to the extensively studied exoplanet system Gliese 581. This system is about 20 light years away and consists of a red dwarf star surrounded by at least three planets. Early data analysis also suggested that the star was home to three more planets, possibly in the habitable zone, however these were later ruled out as spurious signals caused by stellar activity.  

Image: Artist impression of the Super-Earth Gliese 581c  

Credit: NASA 

Initial studies of Gliese 581c suggested that it was the first Earth-like planet discovered within the habitable zone of its star, however later studies showed the planet was closer to its star than first thought.  

As it is currently understood, the three confirmed planets Gliese 581 e, b and c are inside the warm edge of the stars habitable zone and are expected to be tidally locked, always facing the same side towards the parent star. These parameters suggest it is unlikely these planets are hospitable to life. 

In 2008 a radio signal was beamed towards the Gliese 581 system containing 501 digitised messages. If anybody is listening at the other end, we can expect a reply in 2040. 

Object for the small telescope

The Moon 

Take a moment to observe the moon during the partial eclipse on the evening of May 5. The partial coverage of the moon by Earth’s penumbra should make it appear less bright than usual. 

Image: Simulated difference in brightness of the moon during partial eclipse. 


Zubenelgenubi – A double star. 

What looks like a single star, Zubenelgenubi – the Southern Claw – is revealed to be a binary star system containing a pair of binary stars for a total of four stars. The two binary systems are about 5500 AU apart and are separable in a modest telescope. 

 Image: The binary system Zubenelgenubi peeking out from behind an eclipsed moon. 

Credit & Copyright: Francois du Toit, APOD 

Feature Article

Starship roars to life, just like a chest burster 

After a frozen pressurant valve caused an aborted launch attempt on Apr 17, the SpaceX Starship finally undertook its first orbital launch attempt on Apr 20, blasting off from Starbase in Boca Chica at 9:33 am local time heading for the stars. Even if you’ve already seen this a hundred times before, a moment of silence please as we watch the beast take flight – skip to 45:00

Credit: SpaceX 

As exciting as the launch was, things almost immediately started going wrong, with three engines failing before the rocket even got off the ground and more being lost over the course of the short flight.  

Image: Underside view of Starship in flight with six of its thirty-three engines offline 

Two and a half minutes into the flight the spacecraft entered a flip manoeuvre with the intention of separating the Starship upper stage from the lower stage booster. However, stage separation never occurred and shortly thereafter the spacecraft was pointing its engines towards the sky.  

An expert from NASA has noted that if a rocket points its engines towards the sky then you are having a bad problem and you will not go to space today.   

One minute later, as the 120m tall rocket tumbled out of control at an altitude of 29km, engineers at SpaceX triggered the flight termination system – a set of explosives designed to safely destroy the rocket to stop it flying any further off course and putting public safety at risk. 

 Image: Pour one out for the massive engine that couldn’t 

Credit: SpaceX  

While orbit was not achieved, it is generally agreed that the launch was more of a success than a failure. There are seldom few examples of spacecraft that have successfully made it to orbit on their first test flight and for a spacecraft as monstrous as Starship, even getting off the ground was an amazing achievement. 

It is not yet known exactly why Starship failed; the Federal Aviation Authority will conduct an investigation with SpaceX to determine this, however a lot of speculation and criticism has already been directed to the Starbase launch site rather than the rocket itself. 

Just like a chest bursting xenomorph from an Alien movie, Starship killed its host, obliterating Starbase as it roared to life. In the launch video above, chunks of concrete from the launchpad are easily visible blowing away from the launch tower as the rocket takes flight. The entire launchpad was destroyed by the power of the engines as Starship lifted off. 

Image: The crater underneath the launch pad after hundreds of tons of concrete were gouged out by Starship. 

The fully fuelled Starship weighs 5000 tons, which by Newton’s third law means the engines have to direct at least this much thrust out the back of the rocket and into the ground to get the vehicle moving. SpaceX were gambling that the concrete pad would stand up to this onslaught. They lost this bet. 

Image: Note the white plumes of splashes in the ocean on the right caused by material blown away from the launch site 

It seems highly probable that debris and concrete blown off the launchpad may have impacted Starship and caused damage to the vehicle’s engines or hydraulic pressurisation units. The hydraulic pressurisation units are what allow Starship to steer its engines.  

Image: Note the falling debris and the flame that extends up past the base of the rocket, located at the one of Starships hydraulic pressurisation units. 

Unlike many launch facilities, Starbase is not equipped with a water deluge system or a flame trench. As the name suggests, a water deluge system floods a launchpad with water as a rocket takes flight. This flood of water absorbs heat from the exhaust as well as absorbing and deflecting sound from the engines. Rocket launches are literally so loud that sound waves can echo off the launch pad and back into the rocket and cause damage, which the water helps to offset. Likewise as its name suggests, a flame trench contains channels to direct exhaust products away from a rocket in a controlled manner. 

Both of these of these measures were used by NASA when launching the Space Launch System (SLS), which until Starship took flight, held the record as the most powerful rocket ever launched. The difference is that SLS successfully made it to space.  

Image: The Space Launch System taking flight. Note the water deluge (left) and the directionality of the flames (right) away from the rocket through the flame trench. 

Credit: NASA 

It will no doubt take many months to repair Starbase and complete the investigation into where and why Starship had problems, significantly longer than the 1-2 months predicted by Elon Musk. The tendency of Musk to greatly underestimate time scales is known in the space community as Elon time. Use this handy converter to translate into more realistic time frames. 


Other space news 

NASA tests a rotating detonation engine. 

United Launch Alliance experienced a rapid unscheduled disassembly of a Vulcan Centaur upper stage. 

The European Space Agency’s JUICE mission launched on a one-way trip to Jupiter 

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