The great Andromeda galaxy shows its true size in this photo. It spans a whopping four degrees, which is eight times the apparent size of the full Moon. The outer
halo stretches out to its companion galaxy, M110, in the image below the Andromeda galaxy.
The widefield shot clearly shows the pronounced warp of the galaxy’s disk. On the left side, the grand spiral arm and the halo are elevated above Andromeda’s
galactic plane, whereas the right side looks tilted towards the center. The reason for this warp is uncertain. Scientists are still debating whether the warp was
caused by gravitational interaction with its small companions, with the Pinwheel galaxy M33 or by an ancient encounter with some other galaxy.
It took us almost a whole night to gather the data for this picture. The subframes for the image were shot on September 15/16, 2012, on a very crisp night, 1300
meters above sea level on La Palma island. The equipment used was a 135mm Zeiss Sonnar lens and a modified EOS body riding on an Astrotrac 320X-AG.
The dynamic range of the Andromeda galaxy is very high, with intensity gradually fading from the very bright core to the extremely faint outer halo. It would be
impossible to capture this brightness range with a single exposure setting. So several extended series of exposures of 4 minutes (outer halo), 1 minute (spiral arms)
and 15 seconds (central bulge) were digitally combined to produce the final result.
[Released May 1, 2014]