Sky Matters: A meteor shower will light up the night sky in the first week of May

The sky is full of stories. Constellations record mythical figures and events. Most take their names from the Greeks or Romans, although we know the Greeks based their system on Sumerian traditions from some 3,000 years earlier.

Sky Matters: A meteor shower will light up the night sky in the first week of May

There is evidence from cave paintings at Lascaux in the south of France of recordings of star patterns that could be 17,000 years old. While mythical worlds may intrigue us, the stories behind the real universe and all those points of light in the night sky are much more fascinating and diverse, with facts being often stranger than fiction. Each point of light, however apparently trivial, has its own history, its own story to tell.

For example, look towards the east around 10pm and you will see three bright points of light. The brightest is Jupiter which you really cannot miss.

To its upper left is Arcturus and to its lower left is Spica. Imagine you lived before the telescope was invented. With your unaided eye you might notice three things about Jupiter – it moves relative to the other points of light, it changes in brightness and it hardly twinkles.

For Arcturus and Spica you might notice that they do not move relative to other points of light and have a constant brightness except for their twinkling.

And yet since the invention of the telescope, and a few other technological advances, we now know so much more of the story behind these three points of light. We know Jupiter is not a star but a large gas planet, composed mostly of Hydrogen.

It takes light about 4 minutes to get from Jupiter to Earth. Arcturus is a star, about the same mass as the Sun but a good deal cooler, that is nearing the end of its lifetime. It has swelled to 25 times its original size – a fate that will eventually befall our Sun in about 5 billion years. Light takes almost 37 years to reach us from Arcturus.

Spica is not one, but two stars which orbit each other in just 4 days. One star is 10 times larger than the Sun, the other 7 times, and both are much hotter than the Sun. They are so close that the outer layers of the smaller star are being sucked onto the bigger star. Light takes 250 years to reach us from Spica.

When you think about it, our unaided eyes are easily fooled when we look at very distant objects. There is no way the originators of Greek or Roman mythology could ever have woven the astonishing diversity of those three points of light into their tales.

And of course this begs the question: what do we NOT see today ourselves, even with our advanced technology?

And what “stories” will our grandchildren be telling about the universe they live in?

Coming a little closer to home, watch out for the Eta Aquarids meteor shower on May 6th and 7th. Meteors are caused when small particles, often left over from the tails of comets, burn up harmlessly in the Earth’s atmosphere.

Conditions this year are not ideal because the Moon is almost full, so you might see only the brighter meteors.

Look anywhere in the sky and this is one “story” that’s best watched with just the unaided eye, so no binoculars or telescopes please!

By way of some compensation for the lunar light pollution, the Moon will be very close to Jupiter and should make for a terrific sight.

See www.bco.ie/skymatters for more information on the sky in May.

Did you know?

The Moon gets 4cm farther from the Earth every year.

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