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.

Each of those twinkling stars is a sun just like ours. Some are closer than others, some are bigger and brighter than others, but they are all suns. Who knows if there's someone laying on his back lawn on some faraway planet gazing at his starry sky.
Low in the south, you’ll find the Southern Cross (marked by its Latin name of Crux on the map), and the two Pointers. Look how they twinkle! They twinkle colourfully, sometimes showing flashes of red or green or blue.
Stars twinkle because their light passes through layers of air that are different temperatures and densities. These layers act like lenses, bending the starlight. Individual colours of light are bent at different angles, so sometimes more of the red wavelengths make it to our eyes, sometimes more of the blue. That makes the stars appear to shimmer and sparkle. How much twinkling tells you how stable the atmosphere is above you. Astronomers prefer as little twinkling as possible, because a stable atmosphere provides sharper images of the stars.
No matter how steady the atmosphere, stars near the horizon will twinkle quite a bit because you're looking at them through a thicker layer of air.

One of the most remarkable sights in the night sky is M42, the Orion Nebula. It looks like a hazy patch of light in Orion’s Sword, which is above his three-star belt in the northern early evening. The nebula is more than 1300 light-years away and is also one of the biggest – a couple of dozen light-years across.
What’s really remarkable, though, is the nebula’s identity. It’s a nursery that’s given birth to thousands of stars, with thousands more being born today. And all of that activity has taken place over just a few million years.

M42 contains huge clouds of gas and dust. Clumps of this material collapse to form stars. The most massive stars form a cluster known as the Trapezium. These stars are much bigger, brighter, and heavier than the Sun. They produce a lot of ultraviolet energy. It zaps the gas around them, making it glow.
If you could travel inside M42, you’d see hundreds or thousands of stars. Some would be too bright to look at directly, while others would look like dull embers. Ribbons and curtains of gas would surround you, glowing pink, green, or blue-white. Dark lanes and blobs would run through the background – dense clouds of dust where more stars are taking shape.

Come back to the belt stars of Orion and concentrate on the middle star. This is Alnilam, a star of very impressive statistics.
Alnilam is a supergiant, shining from a distance of over 1900 light years. It’s more than 60 times as massive as the Sun, tens of thousands of degrees hotter, and hundreds of thousands of times brighter. Its radiation is so intense, that it blows a dense “wind” of hot gas from its surface. The wind races into space at millions of kilometres an hour.

If you could catch the hot gas, in a million years you’d have enough to make two stars as heavy as the Sun. But you wouldn’t be able to tell much difference in Alnilam itself, because it’s one of the monsters of the Milky Way.

Although Alnilam is only a few million years old, it’s nearing the end of its life. It’s probably consumed its original hydrogen fuel. Over the next few million years, it’ll burn through a series of heavier elements forged in its core. Eventually, though, it won’t be able to sustain that process any longer. Its core will collapse, while its outer layers blast into space as a supernova — briefly outshining the combined light of most of the other stars in the galaxy.
Planetary observers will be thrilled to know that the naked eye planets, Venus, Saturn, Jupiter and Mars will all be visible in the evening sky this month, as will the telescopic Uranus and Neptune. Of the major planets, only Mercury is missing from this line-up.
Venus, shining like a celestial lighthouse in the western sky, has the most volcanic surface of any world in the solar system. Two-thirds of it is paved by volcanic plains, which hold more than 1600 major volcanoes, and more than 85 thousand in all. But it’s not clear whether any of them are active today. There’s evidence of recent eruptions, but there hasn’t been a smoking gun — uh, volcano — until recently.

It’s hard to see eruptions on Venus, or anything else, for that matter, because clouds blanket the entire planet. The only way to see the surface is with radar, which peeks through the clouds. The best radar images to date came from the Magellan spacecraft, which orbited Venus in the 1990s.
Researchers have pored over thousands of pairs of Magellan images snapped months or years apart. They were looking for changes in the volcanoes, signs of recent activity. And they found a change on the flank of Maat Mons, the planet’s biggest volcano. It’s 5 kilometres high, and the caldera at its peak is 30 kilometres across.

An image from early 1991 showed a circular, kilometre-wide pit on the side of Maat Mons. Eight months later, the feature was twice as wide, had a jagged shape, and appeared to be filled with lava. Computer models found that the only reasonable explanation was a volcanic eruption. The most direct evidence, so far, of an active volcano on Venus.

Saturn, located just above and to the right of Venus, is a whopping 1500 million kilometres away. Look out on the evening of January 5 and you’ll see a beautiful line up of Venus and the crescent Moon, with Saturn between them. Get your last look at Saturn now as it will soon disappear in the Sun’s glare. The rings will be entirely edge-onto our view by March.
Jupiter, now high in the northern sky, is perfectly placed for telescopic observation. The planet’s gargantuan proportions means that it appears large in the telescope eyepiece. The cloud belts and its 4 Galilean moons make for interesting viewing.

Mars, visible low in the north-eastern sky, joins Gemini’s twins, Castor and Pollux. Great colour contrast between the red of Mars and the white of the 2 stars. More on Mars next month as it becomes more prominent in the evening sky.

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