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What you need

A clear night

One or more children (optional)

THIS is the last part of the Stargazing at home series. We started at the September equinox and this week it is the December solstice, when the northern hemisphere is tilted at its furthest from the sun and the southern hemisphere is at its nearest.

It is also Christmas, and a great time to spot the International Space Station. If you have young children, and the ISS is visible from where you are on Christmas Eve, it can be fun to tell the kids it is Santa on his trip to deliver presents around the planet.

The space station travels at 28,000 kilometres an hour, circling Earth every 90 minutes or so, always from west to east. That means the six astronauts currently on board typically see 16 sunrises and sunsets each day. For the rest of us, it means we can observe the satellite moving steadily across the sky, much faster than planets and stars, but more slowly than an aircraft.

If you live below 51.6 degrees of latitude, you can see the station passing directly overhead, as this is the angle of its inclination. If you live north or south of this, such as in northern Europe and much of Canada, it will always be lower in the sky.

Because of Earth’s rotation, each ISS orbit is 22.5 degrees to the east of the previous one. That takes it over most countries at some point, although your chances of seeing it will vary from once a month to a few times in one week.

There have been astronauts living on the ISS since 2000 as part of its mission to investigate life in microgravity after the moon missions came to an end. It is 108 metres, end to end, and orbits 400 kilometres above Earth’s surface on average.

To spot the station, it has to be dark. The ISS can sometimes be as bright as Jupiter or Venus, but this depends on its altitude and the amount of sunlight reflecting off it. Satellites tend only to be visible just after sunset or just before sunrise. This is because they have no light source of their own, so it is only through the sunlight they reflect that we can see them.

Unlike meteors, most satellites don’t change in brightness as they move across the sky. Some satellites appear to gradually brighten or even flash – these are ones that are spinning. But this will be a series of flashes, unlike a meteor, which only lights up once.

To check whether the space station will be visible from your location around Christmas, go to . Tap in your location and it will tell you all the sighting opportunities in the next two weeks. You can also sign up for alerts telling you when the station will appear.

Thanks for following the series, and even if you don’t see Santa, I hope your presents arrive safely.

Abigail Beall is the author of The Art Of Urban Astronomy (Buy from *)

To download a printable version of the page click here.

Starting on 4 January: Science of cooking

Even if you are a great cook already, you can make food even more delicious if you understand the science behind it. Join Sam Wong, a Â鶹´«Ã½ reporter and self-confessed food nerd, to learn about the ancient biotechnology of cheese-making, plus delve into fermentation, curing, the science of the perfect roast potato and much more.

What you need for week 1

Onions

A frying pan

Bicarbonate of soda

All the projects are posted at
Email: maker@newscientist.com

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