Our galaxy’s south window

Tonight, let the moon and the bright star Fomalhaut show you our galaxy’s south window on the sky’s dome. In other words, you’ll be looking away from the flat plane of our Milky Way – where most of our galaxy’s stars reside – and toward intergalactic space. You can do this no matter what part of Earth you’re standing on. For the fun of it, we show Neptune – the 8th planet from the sun, and the farthest known solar system planet – but you need an optical aid to see it.

When the moon is no longer there to guide you, try star-hopping from the Great Square of Pegasus to Fomalhaut. Once you find Fomalhaut, you’re looking out the galaxy’s south window.

The 4 stars making up the Great Square of Pegasus might be visible, despite the moonlight . When the moon is long gone, you can always use the Great Square to find the star Fomalhaut.

From the Northern Hemisphere: The Great Square of Pegasus appears high in the south to overhead by around 7 to 8 p.m. local time in late November. This large asterism really does look like a large square pattern, with four medium-bright stars marking the corners. Draw a line through the Great Square’s two westernmost (or right-hand) stars, and extend that line southward to land on the bright star Fomalhaut in the constellation Piscis Austrinus the Southern Fish.

From the Southern Hemisphere: Follow the directions above, but – instead of looking southward to overhead for the Great Square – you’ll be looking low in the north. You’ll still draw your line southward, but, in your sky – starting at the Great Square – that means you’ll draw the line upwards to Fomalhaut. Just take the chart at the top of this post, and turn it upside-down!

Why find Fomalhaut? When you look at this star – sometimes called the Loneliest Star – you are looking some 90 degrees from the plane of our galaxy’s equator.

Our Milky Way galaxy is round and flat, like a pancake. When you look toward Fomalhaut, you’re looking away from the pancake, and out the south window of the galaxy. In other words, we’re looking away from the star-packed disk of the galaxy, into extragalactic space and the realm of galaxies.

Want the exact location of the south galactic pole? It lies east of Fomalhaut, in the faint constellation Sculptor.

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Star chart of constellation Sculptor with galactic pole located in upper middle.

The south galactic pole lies in the direction of the constellation Sculptor.

Bottom line: Tonight, use the moon to find the star Fomalhaut. Then, when the moon is gone, use the Great Square of Pegasus. Once you’ve found Fomalhaut, you’re on your way to visualizing looking out the south window of our Milky Way galaxy.

Easily locate stars and constellations during any day and time with EarthSky’s Planisphere.

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Bruce McClure