The Stars

Everything in the Universe comes down to stars. Stars were almost certainly the first large objects to form shortly after the Universe came into existence.

The majority of stars are, for the most part, hot balls of superheated gas. They give off heat and light, and act as a gravitational anchor for any objects which may be in orbit around it. Yes, that means planets. As we’ve recently discovered, a significant proportion of stars in the sky harbour planets, and many of those planets are just like or eerily similar to our own Earth.

All of the stars that we see in the sky, with one notable exception, are at a very great distance from us. Even with our wonderful modern view of the Universe, the Human Mind still finds it difficult to comprehend exactly how far away the nearest other star is from our humble solar system. And they are a long way away from us.

The Sun

The exception to the above rule is, of course, our Sun, which is a star just like all of the others. Comparatively speaking, it’s very close indeed.

We’ve learned a lot about the more distant stars simply by studying the Sun. We know that our Sun is about four billion years old and that it’s roughly half way through its life span. Yes, believe or not, our Sun is more or less middle aged.

What else do we know about the Sun? Well, we know it’s a variable star. What does this mean? It means that the Sun’s output, the amount of light and heat we receive on Earth, varies over time, we think over a period of about two hundred years.

We see this in historical weather records, and stories which talk about rivers freezing over. In England, the River Thames froze over completely on several occasions in Elizabethan times, and the residents of London held Winter Parties and Fairs on the frozen river. More so, there are reports of hot, balmy summers throughout the Stuart period followed by cold periods where, once again, the River Thames froze over completely.

After a prolonged period of inactivity, the Sun has just started another cycle, Solar Cycle 25. This is good news because we had thought that the sun might be moving into another prolonged cold period and who needs another mini ice age?

How does the Sun generate its energy?

The Sun does not burn fuel in the conventional sense, in the same way as you would burn wood on a fire. It generates energy by a complex process called Nuclear Fusion.

The Sun is composed of large amounts of hydrogen gas, which is contained under immense pressure right at the heart of the Sun. The interior of the Sun is also very, very hot and when you combine two hydrogen atoms under such conditions of extreme pressure and very high temperature, the two hydrogen atoms fuse into another atom, Helium, and give off a very small amount of energy. This might not seem enough to generate all of the heat and light that the Sun appears to give off but you have to remember that the Sun is very, very large and contains an awful lot of Hydrogen.

The Stars look very different...

The Sun is not a particularly big star. In fact, it’s quite small. It’s not the smallest by any stretch of the imagination but it is quite small.

When you look out into space, all of the stars looks pretty much the same. One or two might be slightly different in colour, perhaps a deep red or a brilliant blue but they all look roughly the same size.

This is because they’re at enormous distances.

Earlier on, we talked about how the stars all look the same, superficially at least. This is because, as we said, they’re very, very distant from us here on Earth.

However, close up, many of these stars would look very different indeed.

Take, for example, the bright star at the top left of the constellation Orion. Look closely and you might be able to discern that it’s not like the others nearby stars. In fact, it’s bright red. Now, this star has a name, Betelgeuse (pronounced Beetlejuice), which is actually Arabic in origin and means the centre one.

Betelgeuse is an unusual star. It’s a very young star - only ten million years old which, believe me, is very young astronomically - but it’s also nearing the end of its life. How do we know this?

When Betelgeuse formed, it acquired a lot of material and became very massive indeed. Now, we’ve recently discovered that the bigger a star is, the faster it ‘burns’ its fuel source and Betelgeuse was, originally, very big indeed so it burned through its fuel very, very quickly. If its evolution obeys the general principles which seem to apply else where in the Universe, then Betelgeuse could well end its life very shortly. There’s a possibility that it could do so within the next ten to one hundred years. If that does happen then Betelgeuse will simple blow up in one brilliant explosion, which astronomers call a Supernova. It will be so bright as to be visible during the day and would easily rival and possibly outshine the Moon at night.

Are we in any danger? No, there’s no need to worry because Betelgeuse is a long way from us, around 600 light years in fact. How big is a light year? Well, the light year is one of those useful units of measure that astronomers use to describe distances. It’s how far a photon of light can travel in a single year. Given that it takes light around eight minutes to travel from the Sun to the Earth, you can perhaps imagine that the light year is a pretty significant distance.

Betelgeuse is what we call a Red Super Giant star. There are lots of other types of star - Blue Giants, Red Dwarves, Neutron stars and Black Holes. We’ll come to these later on.

A solar flare on the surface of the Sun. The Earth could easily fit inside one of those loops. No need to worry though. This sort of phenomena happens all the time.