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Jaw-dropping Andromeda galaxy photo comprises 37 hours of exposure

A pair of "backyard" astrophotographers have collaborated to produce a stunning image of our nearest galactic neighbour.

We can't, for obvious reasons, take photos of our own Milky Way galaxy. Luckily, our closest major galactic neighbour, the Andromeda Galaxy, at 2.5 million light-years away in the constellation of Andromeda, is very photogenic indeed.

It has been the focus of a lot of attention. Its proximity makes it brilliant for studying spiral galaxy construction, which helps understand our own spiral galaxy. Space telescopes such as the Hubble and the Spitzer have spent a lot of time photographing it, and we've seen it in many forms: infrared, false-colour composite, even enormously high-resolution at 1.5 billion pixels.

The image you see here, showing the Andromeda Galaxy in visible light, was captured and processed by two astrophotographers right here on Earth, US-based David Lane and Finland-based J-P Metsavainio.

This image of the Andromeda Galaxy was taken right here on Earth. J-P Metsavainio. Used with permission

Using a STL-11000M, 35mm format, 11-megapixel CCD Camera by SBIG coupled with a William Optics Gran Turismo 81 telescope, data collection was Lane's contribution. For 37 hours (non-consecutive), he trained camera and telescope at the tiny section of sky wherein the Andromeda Galaxy lies. He shot 18 hours of visible light exposure, one hour through a hydrogen alpha filter to pick out ionised hydrogen details and six hours each with a red, green and blue filter.

The raw images obtained from these exposures were then sent to Metsavainio, who corrected the optical distortion caused by the telescope using CCDStack 2 software. He then combined the images and adjusted the levels and curves using PhotoShop CS3. This is similar to the processing applied to images obtained from space telescopes.

The resulting image shows Andromeda in all her glory.

The Andromeda Galaxy is a lot bigger than the Milky Way. It contains around a trillion stars, compared with the Milky Way's estimated 200 billion to 400 billion stars. It also measures around 220,000 light-years in diameter, compared with the Milky Way's 100,000 light-years. Because it's so big and so close, it's one of the brightest Messier objects in the night sky and can be seen with the naked eye on a moonless night from a dark location.

Here's its size relative to the moon as seen from Earth. Given that it's so much farther away, you can start to get some idea of how massive it is.

Fun fact: The Andromeda Galaxy is moving through space at a rate of around 400,000 kph (250,000 mph)... directly toward the Milky Way. In roughly four billion years, the two are going to meet in a galactic collision of epic proportions, and probably merge into a giant super-galaxy.

That's for future lifeforms to deal with, though. Right now here on Earth, you can learn more about this wonderful picture on Metsavainio's website.