There aren't many images of this galaxy on AstroBin but I felt it was an interesting target. Taken over 3 nights but the data on the second night had to be discarded due to thin cloud making colour calibration well...astonishingly difficult! The colour data in this image is only 30 minutes each channel which has led to more noise, but time moves on and I must look to imaging in the 'Winter pastures'
Wikipedia says:NGC 7217 is a
gas-poor system
[2] whose main features are the presence of several rings of stars concentric to its nucleus: three main ones –the outermost one being of the most prominent and the one that features most of the gas and
star formation of this galaxy –
[2] plus several others inside the innermost one discovered with the help of the
Hubble Space Telescope; a feature that suggests NGC 7217's central regions have suffered several
starbursts.
[3] There is also a very large and massive
spheroid that extends beyond its disk.
[4]Other noteworthy features this galaxy has are the presence of a number of stars rotating in the opposite direction around the galaxy's center to most of them
[5] and two distinct
stellar populations: one of intermediate age on its innermost regions and a younger,
metal-poor version on its outermost ones.
[6]It has been suggested these features were caused by a
merger with another galaxy[7] and, in fact, computer simulations show that NGC 7217 could have been a large
lenticular galaxy that merged with one or two smaller gas-rich ones of
late Hubble type becoming the spiral galaxy we see today.;
[6] however right now this galaxy is isolated in space, with no nearby major companions.
[6] More recent research, however, presents a somewhat different scenario in which NGC 7217's massive bulge and halo would have been formed in a merger and the disk formed later (and is still growing) either accreting gas from the intergalactic medium or smaller gas-rich galaxies, or most likely from a previously existing reserve.
[8]
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