Solar Storms

21 04 2009

The sun is our constant companion; it supplies heat and light to us and keeps our small blue/green world from freezing. However, as serene as the sun seems on a lazy summers day, a close look at its surface tells a very different story. Read the rest of this entry »

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The Sun – lifecycle

3 03 2009

Over the course of a human lifetime, the Sun is an unchanging, constant companion – bringer of light and heat and champion of the day. It is often tempting to believe that it will always be here and always has been here. The truth, however, is quite different.

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Variable stars

10 02 2009

Looking up in the sky on any given night and you’ll see thousands of stars. Each star appears to be slightly different in brightness – some are stunningly bright, whilst others are just on the edge of visibility. However, there are stars that, if you are very observant, seem to appear and disappear over a period of days, weeks or even months or years. These are known as variable stars. Read the rest of this entry »





Eclipses

27 01 2009

An eclipse (from the Greek ekleipô, “to vanish”) is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon’s shadow crosses Earth’s surface, or a lunar eclipse, when the Moon moves into the shadow of Earth. However, it can also refer to such events beyond the Earth-Moon system: for example, a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its parent planet, or a moon passing into the shadow of another moon. An eclipse is a type of syzygy (a line up of astronomical bodies), as are transits and occultations. Eclipses are impossible on Mercury and Venus, which have no moons. Read the rest of this entry »





Clusters

20 01 2009

Star clusters are groups of stars that are gravitationally bound. Two distinct types of star cluster can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars, while open clusters generally contain less than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a moving group. Read the rest of this entry »





The Planets and Stars size comparison

8 12 2008

We now know the order of sizes of the planets in our Solar System from tiny Pluto to giant Jupiter and even how Jupiter is dwarfed by our own sun. We also know that the sun is what we call a ‘dwarf’ star – it’s not particularly big by stellar standards, but how small is it? Well, it’s not the smallest star we know of – that honour falls to a star called OTS 44, a brown dwarf in the constellation Chamaeleon. Read the rest of this entry »