We can think of our location in the universe along the lines of an address. The street would be planet Earth, the local government area would be the solar system, and the country would be the Milky Way Galaxy.

The state would be the Orion Arm – a ribbon of stars that wraps part of the way around the galaxy.

The Milky Way is a disk that is about a hundred thousand light-years wide. It has a long “bar” of stars in its middle. Spiral arms extend from the ends of the bar and wrap all the way around the galaxy. They make the Milky Way look like a pinwheel spinning through the void.

The arms don’t contain more stars than the darker regions between them. Instead, the arms are like waves on the ocean. As a wave washes through the galaxy, it squeezes clouds of gas and dust, giving birth to new stars. Many of those stars are big, hot, and bright. So, they make the spiral arms look bright and blue. But such stars die quickly, so the wave of brightening doesn’t last.

A few shorter arms fill in between the major ones. And the Orion Arm fits into that category. It’s about 3500 light-years wide and 20,000 light-years long. At our distance from the centre of the Milky Way, the arm wraps only about a quarter of the way around the galaxy.
The arm is named for Orion because of the arm’s location in the sky. The stars of Orion are among its most prominent members. But the arm also includes almost all the stars that are visible to the unaided eye.

If we could go back in time, more than four and a half billion years ago, we could watch our solar system being born: a newborn star surrounded by developing planets, one of which became our own Earth. We also would see a vast cloud of gas and dust that was spawning many other stars around the Sun.
Of course, we can’t actually go back in time. But we can see what the Sun’s birthplace might have looked like simply by observing one of the brightest and easily recognised constellations in the sky.

Orion, the hunter, is high in the eastern sky these January evenings. It features three bright stars in a row, which make up Orion’s Belt.

Above the belt is a row of objects that makes up Orion’s Sword. If you look carefully, you’ll see that one of the stars in the sword looks fuzzy. That’s because it’s not a star at all. Instead, it’s the Orion Nebula (labelled M42 on the star chart), a cloud of gas and dust that’s giving birth to thousands of stars. To the eye alone, it looks like a faint, murky smudge of light. Binoculars reveal the brightest of those young stars, while a telescope shows many more.

Four of those stars are called the Trapezium, because of the shape they form. Each of the stars is less than a million years old. That’s a lot of years by human standards, but the blink of an eye for stars.
The Trapezium’s stars are much hotter and brighter than the Sun. That’s because they’re also much more massive than the Sun. Such heavy stars burn through the nuclear fuel in their cores at a fantastic rate, which makes them shine brilliantly.

Like the nebula itself, the stars of the Trapezium are about 1500 light-years away. The brightest member of the quartet is just visible to the unaided eye, but you’ll need binoculars to see the others.

If not for the Trapezium, we wouldn’t see the Orion Nebula at all. The stars produce a lot of ultraviolet energy, which is absorbed by the nebula’s gas. This boosts the energy level of the atoms that make up the gas. When the atoms return to their normal energy level, they emit light, making the Orion Nebula shine brightly.

Astronomers recently discovered how this great star creator may have formed. They’ve found that the nebula is just a small part of a ring of dust that’s 330 light-years across. This suggests that a cluster of hot, bright stars once inhabited the ring’s centre. Their radiation pushed on the surrounding clouds of gas and dust, causing them to collapse and give birth to new stars. One of those clouds was the Orion Nebula, giving us a view of a stellar nursery like the one that cradled the young Sun.

Below the belt is Orion’s orange shoulder, the star Betelgeuse. And above the belt is the hunter’s blue-white heel, the star Rigel. Both of them are supergiants, stars that are much larger, brighter, and heavier than the Sun. And both are destined to end their lives with titanic explosions.

And you can see the remains of one of these explosions not far from Orion. Almost a thousand years ago, it announced its birth in dramatic fashion, as a brilliant new star in the constellation Taurus, the Bull. It was bright enough to see in daylight for several weeks.

The Crab Nebula is a cloud of glowing gas that spans about a dozen light-years. It’s called the crab because its tendrils of gas resemble a crab.
The nebula was born when a heavy star exploded as a supernova, blasting its outer layers into space. The gas raced outward at millions of kilometres per hour, so it’s spread out to form a big cloud.

At the centre of the nebula is the star’s crushed core, known as a neutron star. It’s roughly twice as massive as the Sun, but only about as wide as a small city. At such extreme density, a teaspoon of its matter would weigh as much as 10 million African elephants!!
The explosion that created the nebula also caused the neutron star to spin more than 30 times a second. And it created a magnetic field a trillion times stronger than Earth’s. As the star spins, the magnetic field causes it to beam energy into space. Radio telescopes detect this beam as “pulses” of energy, so the neutron star is also known as a pulsar.

Get your last look at “ring-less” Saturn before we lose it in the glare of the sunset sky. As our angle of view changes, we will begin to see the rings in their glory by end of 2026. As we draw the curtains on what has been the major feature of 2025, we re-open them to greet the colossus of the solar system, Jupiter. Look for it amongst the stars of Gemini in the north-east at the end of twilight. This behemoth will keep us entertained over the coming months as we watch the merry dance of the 4 Galilean moons around the planet. More on Jupiter next month.

The Moon is Full on January 3, at Last Quarter on the 10th, New on the 19th and at First Quarter on January 26.

Happy observing!

(Generated with Stellarium software, v25.3)