It’s hard to believe that until 1929, we were pretty sure that the Universe consisted entirely of our galaxy, and everything else was inside of us.
Hard to believe that you can look at something like this and not think it was another galaxy like our own, isn’t it?
Yet when you look in the visible light — which is all they knew how to do back then — this is what the pinwheel galaxy (above) looks like through a modern advanced amateur telescope.
Is it really so clear to your naked eye that this image is so different from the one below?
Believe it or not, this image is of a planetary nebula, or just the gas blown off by a single star as it dies and collapses into a white dwarf. It isn’t obvious to me that they should have known back then that these “spiral nebulae” are so different from planetary nebulae. Take a look at another spectacular one…
…and maybe a few more general ones.
Yup, they’re all just dying stars that form planetary nebulae, and they’re all within our own galaxy. Why couldn’t the spiral ones be in there too? Thankfully, we’ve learned a lot more, and our observing abilities simply dwarf what they were 80 years ago. Take a look at today’s Astronomy Picture of the Day, and see if you can’t tell instantly what’s a planetary nebula and what’s a galaxy.
But without the full power of what we have today, it isn’t obvious without doing some serious astronomical analysis, like measuring individual stars in these nebulae, which is what Hubble had to do. So enjoy the nearby planetary nebulae and the distant spiral nebulae, and enjoy the fact that we don’t have to get them confused anymore. (And, it’s always nice to give you some pretty pictures to look at on a Friday.)