Seasonal Skygazing

General news0
Image 2. Stargazing
The Aussie skies are incredibly clear this time of year for stargazing! Credit : Utah State University

Ever wondered, why is it hotter in summer and colder in winter? Does the Sun move further away this time of year? No, the Sun doesn’t move, it’s us that changes position. Now, this once seemed to make sense because the Earth is furthest from the Sun in the middle of the Aussie winter but in fact our temperature is not really affected by distance from the Sun.

While it’s true that the Earth-Sun distance varies during the year, the difference in distance is not enough to account for the temperature swing between the summer and winter seasons, and vice versa. Although Earth’s orbit around the sun isn’t quite circular, the difference between the farthest and nearest separation is only three percent.

As we all learned in school, the seasons are due to the tilt of the Earth’s axis, the imaginary line passing through the Earth’s north and south poles. So in winter, Australia is pointing slightly backwards from the Sun and folks in the Northern hemisphere are pointing forward. By the way, the earth isn’t a perfect sphere. It spins, so it’s a flattened at the poles a little bit. That difference of 43 kilometres.

It’s June, and if we can keep the clouds and rain away this will be an incredible week to enjoy some peaceful and relaxing time under the Moon and stars. The skies are clear and yes it’s always cold this time of the year but have you noticed, the stars seem to tinkle a whole lot more? They do, but stars don’t really twinkle! It’s an optical illusion.
Amazing star trails over the Australian outback captured by Bendigo amateur photographer Lincoln Harrison, who spends hours shooting the night sky. Cr. Lincoln Harris

If you were in space stars would be just bright, unblinking points of light. It’s our atmosphere which scatters the starlight before it reaches your eye, causing that ‘twinkling’ effect. Astronomers use this twinkling effect to calculate what the seeing is going to be like from one night to the next.

When you see a star low down on the horizon twinkling like crazy you can bet it’s not going to be a good night for the telescope. We’ve been having a lot of bad weather lately and the atmosphere is unsteady outside. If a star halfway up the sky twinkles a lot it’s time to watch that video you’ve been putting off.

By the way, all the stars you see in the night sky are all within our own Milky Way galaxy, you can’t see any outside it except with the world’s most powerful telescopes. The next time you stare up and try to count them remember this, there are more stars in the Universe than heartbeats for every human being who ever lived! True, that’s a big number and it’s a pretty big place.

While you’re stargazing don’t forget to have a seat. You’ll see more if you sit while viewing. For one, this allows you more time to relax and examine the field of view. Your body is not concentrating on balancing in the dark. Relaxing while viewing lets you mind concentrate more on the view. Take the strain off your body so your brain can fully enjoy the wonders of the heavens.

Hey, most people will be amazed that, under the right conditions, you can see the planet Venus in daytime. The planet appears as a tiny white dot, which often seems to ‘pop’ out at you once you find it. The contrast between planet and sky is much lower during the day, making the planet hard to see, but most smart phones have apps now that let you find planets in the sky anytime. Try it.

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