The Sky Tonight – March

THE CASUAL OBSERVER

March continues the season of Bunuru, the second summer, and while it is technically the start of Autumn, you can expect the warm weather to hang around a bit longer. 

The Argo Navis is sitting high in the southern sky during March, consisting of the three separate constellations of Carina, Puppis and Vela. You can also spot the trio of Hydra, Corvus and Crater in the eastern sky during the evenings, though these are a bit fainter and more difficult to spot. 

The equinox occurs on Mar 20, bringing the start of astronomical Autumn. On this day the Sun passes directly over the equator, and day and night will both be 12 hours long everywhere on Earth. From here on out, the Sun will continue to appear lower in the northern sky each day until the winter solstice in June, so if there was a symbolic day for the end of summer, the equinox really is it. 

_{Image: Simulated time lapse imagery of the Sun shows that its location in the sky changes throughout the year, and the equinox is the crossover point. Credit: Smith, Scitech.} 

There is a total lunar eclipse on Mar 14. Unfortunately, it is on exactly the other side of the world from us, running from about midday to 6pm Perth time, meaning that we won’t be able to see it at all. People in the eastern states can catch the very end of the eclipse in the early evening facing east. Correspondingly, two weeks later, there is a solar eclipse on Mar 29. Again, this eclipse is visible on exactly the other side of the world from us – its maximum coverage occurs in the far northern remote parts of Canada, and we certainly won’t see any of it from Perth, but it’s nice to keep an eye out on the news. 

The New Moon on Mar 29 is a super New Moon, if you’re into that sort of language. This means the New Moon occurs when the Moon is at or near its closest approach to Earth and so looks slightly bigger in the sky than average.  

Don’t forget to celebrate Pi Day and Einstein’s birthday on March 14.  

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: 

_{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. 

MOON PHASES

First Quarter: Mar 7 

Full Moon: Mar 14 

Last Quarter: Mar 22 

New Moon: Mar 29 

DATES OF INTEREST

Mar 5: Moon near Pleiades 

Mar 9: Moon near Mars 

Mar 14: International Pi Day 

Mar 20: Autumn Equinox 

Planets to look for 

Mars and Venus continue to be visible in the north during March and make noticeable movement towards the west as the days go on. Mars is still easily spotted against Castor and Pollux of Gemini, and Jupiter holds its place underneath Aldebaran in Taurus. An excellent way to begin an evening of skywatching. 

_{Image: Jupiter and Mars in the northern sky with prominent stars labelled. Credit: Stellarium} 

Saturn, Venus and Mercury are all lost in the glare of the Sun this month. They are gone from the evening skies and reappear in the eastern sky just before sunrise in the late month, but you’re probably better just waiting until April for them to really be worth getting up early for. 

CONSTELLATION OF THE MONTH

Lepus – the Hare 

Lepus is a middle sized constellation visible in the northwestern sky during March. It is related to the Orion group of constellations and is interpreted as a hare, but doesn’t really have much deeper mythology associated with it. One day, Orion and his hunting dogs, Canis Major and Canis Minor, hunted a hare. 

The constellation is easy enough to spot unaided, located slightly above Orion in the sky, with the two brightest stars Alpha Leporis (Arneb) and Beta Leporis (Nihal), forming a notable line with several bright stars on either side. 

_{Image: Lepus in the sky relative to Orion and Sirius, with Arneb and Nihal labelled. Credit: Stellarium} 

Alpha Leporis is a supergiant star about 14 times heavier and 30,000 times brighter than the Sun. It is only expected to live for another million years or so before exploding in a supernova event. This star exemplifies the unintuitive result that heavier stars live shorter lives than lighter ones. The ~5 billion year old, less-massive Sun requires less fuel to maintain gravitational equilibrium compared to heavier stars. The more massive Alpha Leporis must burn through fuel much faster to maintain equilibrium, and hence shines for nowhere near as long as the Sun, despite its much larger mass. 

Beta Leporis is also heavier than the Sun, though it’s more modest 3.5 solar masses has given it a lifespan of about 240 million years so far. The star seems to be in the process of swelling to become a red giant. 

OBJECT FOR THE SMALL TELESCOPE

M79 – A celestial snow globe 

Messier 79 is a magnitude 8 globular cluster located in the constellation of Lepus. The cluster contains about 150,000 stars packed in a region about 100 lightyears across. 

_{Image: Messier 79 in all its glory. Credit: NASA, ESA, STScI, F. Ferraro (Universita di Bologna) and S. Djorgovski (California Institute of Technology)} 

There are about 150 globular clusters orbiting the Milky Way and most of them are located in the direction of the centre of the galaxy. Interestingly, M79 is located in almost the exact opposite direction, and is ultimately about 60 000 lightyears from the galactic core. 

This has led astronomers to debate whether M79 was in fact once a globular cluster belonging to the Canis Major Dwarf Galaxy (which we mentioned last month). This argument is compounded by the fact that the Canis Major Dwarf Galaxy’s very existence is still unclear. 

If you would like to hear even more about this month’s night sky, give Particle’s Please Look Up a listen. Hosts Leon and Beth delve deeper into space, share the latest space news, and discuss fascinating astronomical facts. Available on all major podcast platforms.