Sunday, November 7, 2010

What's Up? - The Immensity of the Universe

Welcome back to What's Up?

When looking up at the night sky, the vastness of the universe can be completely mind-blowing. Over the centuries our view of the universe and the scale of the universe has changed dramatically.

A comparison of the difference in sizes between planets and various stars.

For millennia it was believed that the Sun, Moon, and five planets orbited the Earth. The stars were believed to be holes in a large dark sphere surrounding our solar system.

That model had many problems fitting the motion of the planets in the night sky and finally, in the 16th century, Nicolaus Copernicus finally presented a Sun-centred solar system. This theory, called heliocentrism, features the planets of the solar system all orbiting the Sun in perfect circles.

In the early 17th century, Johannes Kepler published what are now known as Kepler's laws. With these laws it was shown that the planets orbit in elliptical (egg-shaped) orbits and not perfectly circular orbits as was believed at the time.

In the 1800's, the distances to the nearest stars were measured and discovered to be quite large. The nearest star, Proxima Centauri, is 4.2 light years away. In other words, since a light year is the distance that light travels in a year, this star is 40 trillion kilometres away! It would take tens of thousands of years travelling in a relatively fast spaceship to reach this star.

In our galaxy, the Milky Way, there are around 100 billion stars in a large pan-cake shaped disk 100,000 light years wide. Our Sun is a tiny yellow-dwarf star in the suburbs of this galaxy, two thirds of the way out from the centre.

In 1925, Edwin Hubble announced that he had discovered that certain nebulae were not actually nebulae, but galaxies just like our Milky Way. Shortly after, he also discovered that the universe is expanding.

The Andromeda galaxy, the nearest large galaxy like our own, is 2.2 million light years away and yet this is only a stone's throw compared to the most distant known galaxies.

The most distant galaxy known is over 13 billion light years away. This galaxy was, interestingly enough, discovered by the Hubble Space Telescope, which is named after Edwin Hubble.

This galaxy appears as it did "only" a few hundred million years after the big bang (the beginning of the universe). This galaxy was barely formed and its first generation of stars were dying off.

We have just reached the current visible limit of our universe. But this doesn't mean that it is the edge of the universe. The universe may be much larger. The edge of the observable universe only comes about because light takes time to reach us from distant galaxies.

Many galaxies are just too far away for light to have reached us yet. In fact, we'll never see the light from the more distant galaxies because the universe is expanding too quickly.

Some astronomers believe that we can see only four percent of the universe, while others think that there may be an infinite number of universes like ours popping into existence.

These mind-stretching theories and ideas are at the edge of what is known about this bizarre universe we find ourselves living in. Although the grand distances involved are impossible to visualize, it's easy to appreciate the astonishing scale of universe and the beauty within.

A National Geographic poster that may help to visualize the size of the universe.
The true size of the universe will take many years to figure out. Until then, let's see what's up in this month's night sky.

There will be a new moon on Nov. 6 which will swell to a full moon by Nov. 21.

The Leonid meteor shower will peak on Nov. 17, so make sure to keep an eye out and you may spot a few Leonid meteors streaking across the sky.

Jupiter will be the brightest star-like object in the sky shining somewhat low in the southern sky throughout the month.

The Athena Community Astronomy Club will have its monthly meeting on Nov. 21 at the Wilmot Community Centre. The meeting runs from 7pm to 9pm and guests are always welcome.

Until next month, just look up!

Hey Kids...
What do you see when you look at the moon? It's a bit like looking at the clouds and picking out shapes. Although there is no Man in the Moon, our brains are very good at picking out shapes. The brain is so good, that sometimes, when a shape doesn't match what we know, our brain chooses something and uses that shape. A lot of people see the "Man in the Moon", but everyone sees something different. Some see a woman singing, a rabbit, or even a man carrying sticks next to a dog. A little imagination can go a long way.