TomV Posted February 20, 2021 Share Posted February 20, 2021 Hi. I was wondering if anyone could tell me which is the most reliable source of information about the distance of M51. I made my first tentative sighting the other night and want to log it but the variety of distance estimates is very confusing: I have a tick list of Messier objects which list it as 15 million light years, a NASA website and Wikipedia have 31 million while a lot of others seem to favour 27. Any ideas? Quote Link to comment Share on other sites More sharing options...
GazAstro Posted February 20, 2021 Share Posted February 20, 2021 I use Sky Safari, that says 28 mly or 8.6 MPC. I guess with such an incredible distance any source can only be a scientific educated guess. Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted February 20, 2021 Share Posted February 20, 2021 28 minutes ago, TomV said: Hi. I was wondering if anyone could tell me which is the most reliable source of information about the distance of M51. I made my first tentative sighting the other night and want to log it but the variety of distance estimates is very confusing: I have a tick list of Messier objects which list it as 15 million light years, a NASA website and Wikipedia have 31 million while a lot of others seem to favour 27. Any ideas? The latest data from the Hubble telescope calculates the distance to M51, as 8.58 ± 0.10 Mpc. A Parsec is calculated at 3.26 light years. The maths say that M51 is between 27.65 and 28.30 million light years away. Here is a link to the methods they used to calculate the distance. https://iopscience.iop.org/article/10.3847/0004-637X/826/1/21 Quote Link to comment Share on other sites More sharing options...
Jkulin Posted February 20, 2021 Share Posted February 20, 2021 Moved it Tom, welcome. Quote Link to comment Share on other sites More sharing options...
TomV Posted February 21, 2021 Author Share Posted February 21, 2021 (edited) Thanks for the replies. At 27 or 28 it still makes it a "best" for me. I will keep looking at it, though, because it was the absolute faintest of fuzzies ( on a far from perfect night and location, admittedly) (And thanks for moving the post) Edited February 21, 2021 by TomV Quote Link to comment Share on other sites More sharing options...
RPK_Astro Posted February 21, 2021 Share Posted February 21, 2021 The reason for the variability in estimated distances is that over time methods and technology have improved. Early guesses were based around assuming a standard brightness. The use of stars such as Cepheid variable improved on that. etc. Quote Link to comment Share on other sites More sharing options...
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