There are many stars to be seen in the night sky but many people do not realize that there is one, which we can study during the daytime (weather permitting).  

The Sun is our closest star, an enormous ball of plasma (very hot gas) that gives out light and heat energy through a process of nuclear fusion in its core. Nearly 5 billion years old, it has enough fuel to live for another 5 billion years or so.

The Sun is over 1 million kilometers across and contains over 99.8% of the mass of the Solar System (Jupiter makes up most of the rest). The Earth is on average 150,000,000 km from the Sun (as we have an elliptical orbit around the Sun) in an area known as ‘the Goldilocks zone’. This is the area that is considered ‘just right’ for liquid water on a planetary surface and possibly life in the forms that we know it.

 

Relative sizes of the Sun and the Earth

 

The visible surface of the Sun, the Photosphere, has a temperature of around 6000 K (K = Kelvin and is the unit in which temperature is measured in Science, in particular, Astronomy). There are cooler patches on the surface, at around 3800 K, which are called sunspots. These appear darker than the rest of the surface, although they are still glowing incredibly hot.

 

Sunspots Image Credit: NASA - Marshall Spaceflight Centre - Solar Physics Group

Sunspots are not very well understood yet. They are caused by interactions with the Suns magnetic field and follow a roughly 11-year cycle. At solar maximum there are many sunspots and lots of solar activity.  At solar minimum there are very few spots and sometimes none at all. Individual sunspots can last for several days or weeks. Sunspots vary in size and shape, often forming groups that can be associated with flares and prominences.   

A challenging project is to follow sunspots, watching their shape and size change over a period of time.  It is also possible to work out the period of solar rotation by plotting the movement of sunspots day by day. The Sun is not a solid body, so different parts of it rotate at different rates. It is an interesting undertaking to try and measure this rotation.

 

Sunturn

Image Credit: NASA - Marshall Spaceflight Centre - Solar Physics Group

Solar flares and prominences are violent ejections of matter and energy from the Sun.  Flares are rapid and intense, lasting only a few minutes. Prominences  (also known as filaments) can last for days or months and are massive arcs of gas that erupt from the surface of the Sun, looping thousands of miles into space. Prominences appear bright compared to space, as they are very hot. However they are cooler than the solar surface, so appear like dark twisted strands when viewed against the hot Photosphere. In order to see flares or prominences you need a specialist telescope. The image below shows a view of the Sun in Hydrogen Alpha.

 

Solar Flare and Prominences

Original Image Credit: NASA - GRIN system

 

During total solar eclipses it is possible to see the Sun’s atmosphere, the Corona. The next total eclipse visible from the UK is not until 2090 but will not be visible as a total eclipse from Woodlands View. However there is a partial eclipse on 20th March 2015. It will not be possible to see the Corona at this time but will still be an event worth watching.

 

Update: Below is a photograph of the partial solar eclipse of March 2015, taken at 09:30 a.m.

Partial Solar Eclipse

Partial Solar Eclipse as seen from Woodlands View - March 20th 2015

 

The Sun is the brightest object in the sky and is very dangerous to look at, even with the naked eye. You should never look directly at the Sun without proper eye protection, nor should you observe its reflection in glass, mirrors or water. Sunglasses, clouds and welding goggles do not cut out enough of the Sun’s light to make it safe to observe.   You should certainly never look directly at the Sun through a normal telescope or other optical device. To do so almost certainly means painful eye damage and in many cases blindness. It is not a risk worth taking.

However, there are some safe ways to observe the Sun either directly using special telescopes and filters, or indirectly using projection.

It is possible to purchase special ‘eclipse glasses’ that allow you to observe the Sun safely. These need buying from a certified dealer, and will need checking regularly for holes and rips. 

You can buy special solar filters for small telescopes but these are expensive and we recommend that this activity is not undertaken until you have some observing experience, especially as you can see just as much detail by safely projecting an image of the Sun. If you do decide to buy a filter, please get one from a specialist telescope shop and make sure that it is regularly checked for damage.

Even the smallest pinhole in a filter can let through enough light to cause severe damage to your eyes.

Nettie has purchased a special (expensive) Hydrogen Alpha telescope solely for solar observing. This cuts out all light except a certain wavelength given off by hydrogen. This allows detail such as solar flares, granulation and prominences to be seen. 

The best, easiest and safest way to observe the Sun is by projection. You can build a simple pin-hole camera or project an image of the Sun onto a screen using a small telescope (with larger telescopes you risk overheating them).

Below are three images of the sun taken on the same day, within a three hour time period using different methods of observing.