A guide to what's up in the sky for Southern Australia

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Starwatch for August 2026 (2nd Aug 2026)

The mid-winter Milky Way is still high overhead, and stars like Vega, Altair and Fomalhaut help to light the way on these cold nights. They will soon give way to the spring stars and constellations. Like our Sun, these stars are what astronomers refer to as Population I stars. Let’s explain that.

Every “normal” star is a ball of hydrogen and helium, the simplest of all chemical elements. All of the hydrogen and most of the helium were forged in the Big Bang.

Stars also contain smatterings of heavier elements, which are known as metals. These elements were forged by the stars themselves. As the stars die, they expel some of these elements into space, where they can be incorporated into new stars. So, each generation of stars contains a higher proportion of metals; everything from carbon and oxygen to iron and lead.

Based on the amount of metals, astronomers divide stars into two broad categories — Population I and Population II.

The Sun belongs to Population I. These stars contain fairly high percentages of metals, about two percent in the case of the Sun. These stars formed recently, after earlier generations had pumped the heavy elements into space.

The earliest generations yet seen form Population II. These stars have a much smaller percentage of metals, which means they formed when there were fewer metals around; perhaps less than a billion years after the Big Bang. When the massive ones used up their hydrogen reserves, they started the production of chemical elements heavier than hydrogen. Eventually, they exploded as supernovae, and dispersed their material into interstellar space. This was needed for the later formation of Population I stars, planets and life as we know it.
One of the main tasks for the James Webb Space Telescope is to search for Population III stars. These stars are the hypothetical first generation of stars in the universe, born completely from pristine primordial gas (hydrogen and helium). Because they formed before the first supernovae, they were entirely free of heavier elements (metals) and are believed to have been exceptionally massive, luminous, and short-lived. The hunt continues.

The star Vega is a bit of a puzzler. Over the years, astronomers reported evidence of several planets orbiting the bright star. But none of the planets has been confirmed. And observations by two space telescopes revealed nothing. But they left open the possibility of planets.

You can find Vega low in the north in the mid-evening. It’s about 25 light-years away. It’s a bit bigger, brighter, and heavier than the Sun. And it’s younger, at 450 million years – just 10 percent the Sun’s age.

A disk of dust encircles Vega. Hubble and James Webb Space Telescopes took a good look at the system. They showed that the disk is quite smooth. It’s probably renewed by comets and asteroids. They shed material as they orbit the star, and even more when they slam together. The smoothness of the disk means there are no giant planets orbiting within it. If there were, they would clear out wide gaps.

There is one gap. But it’s not completely open. A planet several times the mass of Earth could orbit in that zone, partially clearing it out. And there could be smaller planets elsewhere in the system – especially close to Vega. But so far, there are no confirmed planets, leaving Vega to travel through space alone.

The brightest star of the Southern Cross is like a whole episode of “Dancing with the Stars.” It consists of perhaps six or more stars. They’re all twirling through their own ballroom, linked by the strong hands of gravity.

Alpha Crucis, marked as Acrux on the chart, is 320 light-years away. To the eye alone, it looks like a single point of light – the 13th-brightest star in the night sky. But binoculars or a telescope show two stars. Both of them are at least a dozen times as massive as the Sun, and thousands of times brighter. They’re so far apart that it takes about 1300 years for them to complete a single orbit around each other – a slow turn across the dance floor.

But one of those stars is actually two stars on its own. They’re so close together that not even the biggest telescopes can see them individually – the second star reveals its presence only to special instruments. But it’s also bigger, heavier, and brighter than the Sun. The two stars are dancing to a faster tempo – one turn around each other every 76 days.

Those three stars might have three more companions. They’re a long way from the first trio, and they’re not as impressive. But they appear to share a common motion through the galaxy with the brighter trio. That means the two groups could be gravitationally bound to one another – dancing a waltz that would require a hundred thousand years to complete one turn across the floor.

There’s a beautiful conjunction between the Moon and the planet Venus on the evening of August 16. Venus is the “evening star” – the brightest object in the night sky after the Moon. The Moon is a thin crescent – the Sun illuminates only a sliver of the lunar hemisphere that faces Earth. Plenty of opportunity for beautiful nightscape photography.
We can’t see it, but the Moon is moving farther from us, by about 3.8 centimetres per year. It’s been moving away since it was born, when Earth was young. In fact, that shift was one of the clues that led to the leading theory of how the Moon was born. That number is not an estimate. It is a direct measurement, made by firing laser pulses from Earth toward retroreflectors left on the lunar surface by Apollo astronauts, timing the return journey to the nearest nanosecond, and calculating the distance with extraordinary precision.

In the chaotic conditions of the early solar system, Earth was walloped by a planet about the size of Mars. That blasted debris into orbit around Earth. Much of that material quickly coalesced to form one or more moons. Today’s Moon is the only survivor.

The collision caused Earth to spin much faster, so a day was much shorter than it is now. Gravitational interactions between Earth and Moon have slowed us down. But they’ve also caused the Moon to slide farther away.

The mechanism is elegant and gradual. The Moon's gravity raises tidal bulges in Earth's oceans. As Earth rotates, those bulges are carried slightly ahead of the Moon's position. The gravitational pull between the ahead-running bulge and the Moon transfers a small but continuous amount of Earth's rotational energy to the Moon — slowing Earth's rotation fractionally and pushing the Moon into a slightly wider orbit with each passing year.

That is why Earth's days were shorter billions of years ago. That is why the Moon once appeared larger in the sky and generated stronger tides. And that is why, over geological timescales, the gradual drift accumulates into distances that fundamentally reshape the relationship between the two bodies.
Today the Moon sits 384,400 kilometres away. At 3.8 centimetres per year, it will be 38,000 kilometres farther in a billion years. The tides will be weaker. Earth's rotation will have slowed further. The Moon will appear slightly smaller.

The Moon is at Last Quarter on August 6th, at New on the 13th, at First Quarter on the 20th, and Full on August 28th.