With the US shutdown there has been a lack of images coming from NASA, which is particularly disappointing as last week Ison made her closest pass to Mars. Luckily the European Space Agency (ESA) is still up and running and releasing images! The ESA's Solar and Heliospheric Observatory or SOHO for short is a satellite that was launched in 1995 to study the Sun with a variety of on board instruments.Originally the SOHO mission was only going to last a couple of years but due to the amazing results it was producing it is still running today.
The SOHO craft is fitted with a special instrument called SWAN (Solar Wind ANisotrpies) which is the only instrument on board not to be pointed at the Sun, instead it looks at everything else! Swan watches the rest of the sky, measuring hydrogen that is ‘blowing’ into the Solar System from interstellar space.
By studying the interaction between the solar wind and this hydrogen gas, SWAN determines how the solar wind is distributed. The ESA have used SWAN to detect the hydrogen in Ison's coma, which should be able to tell us how much water is being produced and at what rate. The data from SWAN should give us great new insights in to the emissions given off by sun grazing comets like Ison.
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| Ison captured by European Space Agency's SOHO craft using the SWAN instrument |
The image above is the first image of Ison taken by SWAN to be released by the ESA, over the next few weeks as Ison brightens we should get ever more impressive pictures. Swan takes 360 degree images of space the only thing it doesn't picture is the Sun and the Earth, which are the dark spots on the image. What SWAN is photographing is the effect that solar wind has on the element hydrogen. Sounds complicated but its quite simple really, imagine you wanted to take a picture of the wind, but you cant see it. So you photograph the effect the wind has blowing dust on the ground or on the leaves of a tree, this is basically what SWAN does! Instead of dust and leaves it photographs the effect on hydrogen by the solar wind. What makes this camera particularly important for studying Ison is that because it basically photographs hydrogen, we can tell how much hydrogen is being given off by Ison, which is the main make up of a comets coma and tail. Now even we will admit that this image is not the most spectacular of Ison we've seen, but as Ison gets closer to the sun and more hydrogen is given off her coma and tail will expand and the images by SWAN will get bigger and better and the data will be invaluable!
