There's nothing more magical than to lie down on your back lawn on a warm summer evening and gaze up at the brilliant night sky.

You might be sitting on the beach, enjoying one of our last warm summer evenings, watching as the Sun drops below the horizon. The sky will grow darker. Eventually, it’ll turn almost black, especially from locations away from the annoying glow of city lights. You’ll probably wonder why the night sky turns dark. Well, you’re not the only one. For several centuries, scientists also wondered why the night sky turns dark.

Most scientists thought the universe was infinite in both time and space. In other words, there was no point in time when the universe began, and it extended without end in every direction. If so, then we'd eventually see a star at every single point in the sky. That would make the night sky as bright as the Sun.
In the last century, though, astronomers realized that the universe isn't infinite. It began 13.8 billion years ago, in the Big Bang, so it’s not infinite in time.

And our view of the universe isn’t infinite, either. Because the speed of light is limited, there hasn't been enough time for us to receive light from stars that are more than 13.8 billion light-years away. So, we see only a bubble of space, known as the observable universe.

While we see lots of stars in the night sky, we also see lots more empty space; making the night sky dark.

If our eyes were attuned to microwaves, though, the sky would be bright. The afterglow of the Big Bang fills the entire universe. At the time it was produced, that energy was at visible wavelengths. But because the universe is expanding, the light waves have been stretched to longer wavelengths, invisible to the human eye.

As summer gives way to autumn, we arrive at the equinox on March 20. Day and night are about equal across the entire planet; hence the name “equinox,” which means “equal nights.”

The Sun is passing through Pisces, the fishes. In fact, it’s appeared in Pisces at the equinox for a couple of thousand years. Before that, it was in Aries, the ram. The shift is the result of an effect known as precession of the equinoxes.

Earth wobbles on its axis like a spinning gyroscope. As it wobbles, the Sun’s location against the background of stars moves, too. When the modern constellations were first drawn, the Sun appeared in Aries at the March equinox. So even today, the point of the equinox is sometimes called the First Point of Aries.

Stars come in a whole spectrum of colours, from icy blue to deep red. But our eyes can see the colour in only a few stars. Most of them are simply specks of white. That’s because most stars are too faint to show off their palette. The human eye can pick out the colours of only the brightest ones.

Most of us can see colour in some of the brighter stars in view this month. Betelgeuse, high in the north-west at nightfall, is bright orange. So is Aldebaran, lower in the sky. Rigel, at the opposite end of Orion, is blue-white, as is Regulus, in the north-east.
Some bright stars don’t show any colour. The best example is Sirius, the brightest star in the night sky, which is almost overhead during these early autumn evenings. It shines pure white, its true colour.

Another white star shines further south, Canopus.

When you’re headed toward the Moon or planets, there are no signposts to keep you on the right track. Fortunately, nature provides its own markers: the stars. Spacecraft orient themselves by sighting on the Sun and one or more other stars. In the early days of space exploration, the most popular of those stars was Canopus.

Canopus is a good navigational beacon because of a combination of brightness and location. It’s the second-brightest star in the night sky, only Sirius outshines it. And it’s in a region with no other bright stars. That makes it an easy-to-find target.

Canopus is more than 300 light-years away. It looks so bright because it’s more than 400 times brighter than Sirius, and ten thousand times brighter than the Sun.

The star is eight times the mass of the Sun. So even though it’s billions of years younger than the Sun, Canopus is nearing the end of its life. It’s uncertain how its demise will play out. It straddles an important dividing line. On one side of the line, it would end as the Sun will, throwing off its outer layers, leaving a hot, small corpse known as a white dwarf. On the other side, it would blast itself to bits as a supernova, briefly providing an especially bright lighthouse.
Look below Canopus, and you’ll notice two faint smudges of light. These are the Large and Small Magellanic Clouds, satellite galaxies of our own Milky Way galaxy.

The Large Magellanic Cloud is also home to one of the largest star forming regions in the sky. Because this fiery region’s knots of gas and dust resemble a spider, it’s called the Tarantula Nebula. Labelled on the star chart with its NGC catalogue number of 2070.
In star-forming regions like the Tarantula, stars are born from clouds of gas and dust. The hottest of these newborn stars emit a lot of ultraviolet energy. This energy tears electrons off hydrogen atoms, ionizing the hydrogen; giving it an electrical charge. Regions of ionized hydrogen thus mark areas that have spawned huge stars, as well as many smaller ones.

The most famous region of ionized hydrogen in the Milky Way is the Orion Nebula (M42), which appears in the sword of the constellation of Orion. To the unaided eye, it looks like a fuzzy star.
The Orion Nebula has spawned thousands of new stars. But the Tarantula puts the Orion Nebula to shame. The Tarantula spans hundreds of light-years and has given birth to tens of thousands of stars. Were the Tarantula Nebula (200,000 light years away) at the distance of the Orion nebula (1600 light years away), then it would occupy a large part of our sky and be visible in daylight!

Two bright planets remain easily observable in the evening sky. Jupiter and Mars. Target Jupiter first as it sets early. You can find it between the horns of Taurus, low in the north-western sky. It’s fascinating to watch the 4 largest moons as they dance around the planet from night to night. Even binoculars will show them. This is your chance to channel your inner Galileo. Just like he did way back in 1609!
Mars can be found between the twins of Gemini in the northern sky. As the Earth is passing it on the inside track, it is getting further away from us, and hence smaller and fainter. At the beginning of March, it will be 129 million kilometres from us, by month’s end that distance will have increased by a further 40 million kilometres. It’s not a great view in a telescope at the moment.
For a long time, scientists believed that, with no liquid core like the Earth, the interior of Mars was dead. However, during its four years of life, from 2018 to 2022, NASA’s InSight lander recorded more than 1300 “marsquakes.” Most of them were tiny, and most were caused by space rocks slamming into Mars. But the largest quake it ever felt came from the planet’s insides, far below the surface. That’s an indication that Mars isn’t quite dead yet. The quake took place in May of 2022, just a few months before InSight’s mission ended. It was magnitude 4.7. By Earth standards, that’s not much, maybe strong enough to feel, but not strong enough to cause any damage. But by Mars standards, it was a whopper, five times more powerful than any measured previously. And it rattled around the planet for six hours.

The Moon is at First Quarter on March 7th, Full on the 14th, at Last Quarter on the 22nd, and New on March 29th.

Happy observing!