The dominant constellation in our evening sky during autumn and winter is Scorpius, currently shining brightly in the eastern sky. Its brightest star, Antares, is a huge star of gargantuan proportions.

If we replaced our Sun with it, then all the planets from Mercury through to Jupiter would all find themselves engulfed within it! Just below the tail of Scorpius, you can find the star clusters designated M6 and M7. Take the trouble to observe these with binoculars. They make a beautiful sight, with many bright stars sparkling like diamonds against a background of gold dust.

As we shift our gaze to the south, we find the Southern Cross high in the sky. To the right and above the Southern Cross, the Milky Way is at its brightest. It’s here that we find a large cloud of gas and dust, known as the Eta Carinae Nebula (labelled 3372 on the chart).

The nebula (Latin for cloud) is a vast cloud of gas and dust, about 7300 light-years away in the constellation Carina, that's given birth to more than 60 hot, heavy stars. And one of those stars is the star that gave the nebula its name. Eta Carinae is a fascinating object.

It first attracted attention in the mid 1800s, when it flared to several hundred times its normal brightness, becoming one of the brightest stars in the sky for a brief period of time. The instruments of the day couldn't reveal any detail around the star, so astronomers couldn't make much sense of what was happening. But modern telescopes reveal an impressive sight. The flare-up was caused by a massive eruption from the star's surface. It surrounded Eta Carinae with a turbulent cloud of gas and dust that looks like an hourglass.

Astronomers measured its mass at about a hundred times that of the Sun. Current theories of star formation say that's almost too big for the star to even exist. But recent observations suggest that Eta Carinae may consist of 2 stars, which are hidden inside the cocoon. One star could be about 30 times as massive as the Sun, and the other about 80 times as massive. The stars produce violent "winds" of gas. As the winds ram into each other, they produce X-rays. The X-rays are most intense every five and a half years, suggesting that that's how long it takes the two stars to orbit each other.

Between the Southern Cross and the southern horizon, you’ll notice two small fuzzy blobs in the sky – these are the Large and Small Magellanic Clouds. You’ll need a dark sky to see these. When the first Portuguese explorers sailed into southern waters, they saw these faintly glowing clouds that weren't visible from their homeland. They named the little clouds for Ferdinand Magellan, the explorer who'd organized the first trip around the world. The Magellanic Clouds became beacons for southern navigators.

The Large Magellanic Cloud is the closer of the two, at a distance of about 170,000 light-years, whilst the Small Magellanic Cloud is about 40,000 light-years further than the large cloud. Due to their nearness, both galaxies serve as excellent laboratories for studying the universe. They contain a variety of stars, giant clusters of fairly young stars, and big clouds of gas in which new stars are being born.
Measuring the distances to other galaxies is a tough problem. In fact, it would be all but impossible without a discovery that was reported over 100 years ago. The discovery was made by Henrietta Leavitt, an assistant at Harvard College Observatory.

She was studying stars in the Magellanic Clouds. She found hundreds of stars that regularly brightened and faded. Leavitt discovered that there was a relationship between how bright the stars got and how long it took them to brighten.

The discovery was one of the most important of 20th-century astronomy. That’s because it provided a way to measure the relative distances to these stars, and therefore to their parent galaxies. Just measure the length of a star’s pulse, then see how bright the star looks. Stars that look fainter must be farther away.

Later, astronomers turned the relative distance into absolute distance when they realized that there are similar stars in our own galaxy; close enough to measure their distances with other techniques. With the distances to a few of the stars, astronomers could then calculate the distances to any of them just by measuring the star’s brightness and the length of its pulses.

These types of stars are bright enough to see in galaxies that are up to 50 million light-years away. These “flickering” stars provide a way to measure distances to the closest galaxies.

No one has seen Comet Halley in decades. Even so, it’s reminding us of its presence about now. That’s because it’s responsible for the Eta Aquarid meteor shower. The shower is predicted to reach its peak around May 5-6, with top rates of about 40 or 50 meteors per hour.
A meteor shower occurs when Earth passes through the orbital path of a comet. As a comet nears the Sun, some of the ice at its surface vaporizes in the heat. That releases small bits of rock and dust. Over time, this “comet dust” spreads out along the comet’s orbit. When Earth intersects the orbit, some of the debris slams into the atmosphere at tens of thousands of kilometres per hour, forming the glowing streaks known as meteors.
The Eta Aquarids are one of two showers that are caused by Halley. The other takes place in October. Our planet passes a little deeper into the debris field in May, so this shower is better.
The shower is best viewed in the early hours of the morning. That’s because the point at which the meteors appear to “rain” into the atmosphere is located in the constellation of Aquarius, seen low in the eastern sky. To see the Eta Aquarids, find a dark, safe skywatching site, away from city lights. Unfortunately, this year the Moon’s light also interferes with the view.
Two bright beacons hold centre stage in our night sky during May. In the beautiful pastel hues of an Australian sunset, you’ll find the brilliant planet Venus shining like a celestial lighthouse low in the north-western sky. A little further to the north and higher, you’ll find another bright star. That is the planet Jupiter, the largest of all the planets.

Venus, the “evening star”, is our closest planetary neighbour. It emerged from behind the Sun last month, and it’s coming closer to us in its smaller, faster orbit around the Sun.

As it does so, sunlight illuminates less of the hemisphere that faces our way. The combination of the closing distance and therefore larger size are such that Venus will continue to gain an even greater brilliance in coming months. A view in a telescope will show Venus to look like a Moon only days away from Full. It is currently about 225 million kilometres from Earth. When it reaches greatest brilliance in September, that distance will have shrunk to just 75 million kilometres.

Venus’s phases were discovered by the famed Italian astronomer Galileo Galilei. He was the first to turn a telescope toward the heavens. Among other wonders, he saw that Venus went through a cycle of phases, just as the Moon does. His discovery confirmed that Venus orbits the Sun, placing our star at the centre of the solar system instead of Earth.

The Moon is Full on May 2nd, at Last Quarter on the 10th, New on the 17th, at First Quarter on May 23rd and Full again on May 31st.