The Sky Tonight: November 2024

November continues the season of Kambarang and we really start to swing into the hot weather that will come to be the norm over the next few months.

Venus continues to dominate the western sky all month, rising higher as the days go on. It is moving through Scorpius this month as the giant arachnid is setting in the west after its long march across the sky, so you can use Venus as a useful visual marker to see how the background stars change day by day. 

The Leonids meteor shower peaks on Nov 17. These meteors appear to emanate from the constellation of Leo and the best time to see them is before sunrise on Nov 17 and 18 in the northeast. The Waning Gibbous Moon in the northwest is going to be a pain but there’s nothing we can do about that. Mars is there also as a faint red dot to help you get your bearings. In good conditions you might expect to see about a dozen meteors per hour. 

These meteors originate from comet 55P/Tempel-Tuttle. This comet is in a retrograde orbit, meaning it moves in the opposite direction around the Sun to most other objects in the solar system. Consequently, meteors making up the Leonids are essentially colliding head-on with Earth, so they move fast across the sky – about 70km/s – making this the fastest known regular meteor shower. Historically, Leonids have been responsible for some of the greatest meteor storms ever. The Leonid meteor storm of 1833 is estimated to have produced about 100 000 meteors per hour at its peak, though that level of activity isn’t expected this year. 

Astrofest

Astrofest is taking place again on Nov 9 at Curtin Stadium and Edinburgh Oval in Bentley. This is the largest public astronomy event in Australia and is well worth going to. Gaze into the night sky with big telescopes. See radio telescopes working to discover the hidden universe invisible to our eyes. Listen to real-life astronomers about what they’ve discovered in space. Explore the astrophotography exhibition and more! Find out more here.

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: 

*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. 

Dates of interest 

Nov 4: Mercury, Antares, Moon and Venus visible in the western sky 

Nov 9: Astrofest 

Nov 11: Moon near Saturn 

Nov 21: Moon next to Mars 

Moon phases 

New Moon: Nov 1 

First Quarter: Nov 9 

Full Moon: Nov 16 

Last Quarter: Nov 23 

Planets to look for 

Mercury visible in the eastern sky after sunset all month. It has a close encounter with the Moon on Nov 3. By Nov 4 the Moon will have moved higher in the sky, making for a neat line of observations from Mercury to Antares, the Moon and Venus.  

Saturn is visible as a yellowish point up in the northwest from sunset until about midnight. Meanwhile Jupiter is approaching opposition so is rising just after sunset in the east and is visible all night as a very bright point. Mars shows its face about midnight, just as Saturn is setting. You can watch Saturn set and then turn around and watch Mars rise. 

Constellation of the month 

Mensa  – The Mountain 

Mensa is a small constellation in the far southern sky. It was originally called ‘Montagne de la Table’, named after Table Mountain in South Africa, by that prolific namer-of-constellations Nicolas-Louis de Lacaile, before being shortened to Mensa by that prolific scientist-of-every-disciplie John Herschel. Interestingly, it is the only constellation named after a geographical feature of Earth, and so appears as a plateau in artisitic images.  

The constellation can be tricky to spot, especially from light polluted skies, and in some sense Mensa can be thought of as the faintest constellation in the night sky. Its brightest star, Alpha Mensae, is a binary star system 33 lightyears away made up of a Sun-like star, about 80% as bright as the Sun, orbited by a tiny red dwarf star 4.5 billion km adjacent (about the distance from the Sun to Neptune). Their combined light shines with a miniscule magnitude 5.09 in our night sky, just barely visible to the naked eye, and this actualy makes it the dimmest brightest-star of any constellaton. Everything else in the constellation appears fainter. 

Mensa is home to the Large Magellanic Cloud (LMC), a dwarf galaxy that orbits the MIlky Way and also spills over into neighbouring constellation Dorado. Situated 160 000 light years away, the LMC contains about 20 billion stars adding up to around 1% the mass of the Milky Way, and it appears in the dark night sky as a faint, well, cloud, appearing about 10 times larger than the Moon in in the sky.

The LMC, along with the nearby Small Magellanic Cloud (SMC) have been known about since antiquity but received their modern names after the writings of Ferdinand Magellan describing his circumnavigational voyage in the early 16th century brought them to the attention of European astronomers. 

The LMC seems to have once been something of a mini version of the Milky Way. It shows a barred structure running through its centre along with evidence of spiral arms, just like the much (much) larger Milky Way. This ‘dwarf barred spiral galaxy’ structure is being disrupted as the LMC interacts with the SMC and the Milky Way, and the LMC will eventually be absorbed into the Milky Way in about 2.5 billion years’ time.  

Object for the small telescope 

The Tarantula Nebula 

The Tarantula Nebula is an enormous star forming region located in the Large Magellanic Cloud. It is known as a HII region – astronomy jargon meaning it contains a lot of ionised hydrogen. New stars form when clouds of (mostly hydrogen) gas collapse under their own weight, eventually fragmenting into stars. As these new stars form, a few monsters stand out from the crowd, shining prodigiously in ultra-violet light. This UV light burns away pockets of the surrounding remaining hydrogen gas, ionising it in the process. This gives HII region nebulae like this a bubble-tendril appearance – a wispy stringy exterior surrounding a hollow interior filled with stars. All of this is on display in the Tarantula Nebula.  

The Tarantula Nebular appears slightly larger than the Full Moon in apparent size in  the sky, so, remembering that it is 160 000 lightyears away, some quick maths shows that if the Tarantula Nebula were located inside the Milky Way, in place of the well-known Orion Nebula (1300 light years away) it would span a good 4-5 handspans across the sky, compared to the Orion Nebula’s pinkie-nail size. Try it yourself right now. Hold out your hands and stretch your fingers out and lay out five handspans across the sky. That’s almost as big as some of the spiders in Australia!   

The First Page of Euclid’s Great Cosmic Atlas 

It has been more than a year since the Euclid spacecraft was launched by the European Space Agency, which we wrote about here.  

As a quick recap: Euclid, now located about 1.5 million km from Earth – 5x further than the Moon – is a survey telescope. Its mission, which it has chosen to accept, is to spend 6 years looking for as many galaxies as it can, ultimately mapping 1/3 of the sky to a distance of about 10 billion light years. Euclid is enormous, both in size and scope, as the 1.2m diameter mirror of the telescope collects enough light information to beam back to Earth about 100GB of data per day.  

And boy has it delivered. You know that feeling you sometimes get when you look at the stars and wonder how far away they are, and how many of them are in the universe and what’s your place in it? Take a deep breath and:  

Just about every speck in the above image is not a star, but a galaxy – made up of billions of individual stars. You can see a zoomable version here. For perspective, some readers may remember the paradigm shift in astronomy brought about from the Hubble Deep Field, with its ‘mere’ ~3000 galaxies in a single image. 

The purpose of Euclid’s voracious data collection is to study galaxies over cosmic timescales to see how, if at all, they behave differently between young and old. The most distant galaxies we see are also the oldest – we’re seeing them the furthest back in time because their light has taken up to 10 billion years to reach us. Looking at distant galaxies and comparing them, and their behaviour, to more nearby galaxies will give astronomers an idea of how Dark Energy and Dark Matter influence the evolution of the Universe over billions of years and allow them to refine models of cosmology. To do that, you need a huge dataset. The European Space Agency has just released Euclid’s latest result, a 208 gigapixel mosaic representing just 1% of the sky and containing 100 million objects, at least 14 million of which are galaxies.

There’s a lot going on in this image, and it’s hard for a picture squeezed into a browser to really give the study justice, so you should really watch this video to fully understand the perspective.  

Because of the way Euclid is designed, stars in the Milky Way galaxy that appear in its images have tiny spikes pointing out from them, an optical artefact called diffraction spikes. While a nuisance to astronomers, it makes for a handy tip – If it has spikes: it’s a star, if it doesn’t: it’s a galaxy, no matter how small and faint it looks. Now, count them: