Why this galaxy on this particular night? Simply because it was a relatively bright object that was high in the sky within Leo and facing south, the direction of least obstruction from my local observing position. One of the best tips I learned about observing deep sky objects, in particular galaxies, is to never underestimate the benefits of superior elevation.
Setting up my video telescope at its maximum integration time of 10 seconds, I wasn’t holding too much hope of anything spectacular appearing from these semi light polluted skies. I was thankfully mistaken.
Despite its staggering distance of nearly 30 million light years, the video screen began resolving a beautifully presented barred spiral galaxy with easily discernible spiral pathways, surrounding a very bright core. I’m always in awe when viewing distant galaxies like this in real time. The main idea that captures my imagination is the understanding of what makes up those dim dust lanes – billions of suns!
NGC 2903 is only slightly smaller than our own Milky Way at over 80,000 light years across and is very similar in structure to our own island universe. Its central bar is a common feature in spiral galaxies found in around two thirds of them. The formation of these bar structures is still poorly understood. The most popular hypothesis is due to a density wave propagating from the galactic core, reshaping surrounding dust into a long column. In general these structures indicate relative maturity for a galaxy – younger galactic siblings don’t have them.
They say good things come to those who wait. Never was this more exemplified than this evening after several hours in bitterly cold conditions on Culloden moor with my video telescope. The cold made setup and targeting much more fraught than usual, and the small gas stove I’d balanced pecariously beside the monitor did little to help.
However, near the end of my session I hit the jackpot when this stunning image of the Whirlpool galaxy, over 23 million light years away, materialised from the video screen.
This image is a true testament to the power of video astronomy and the huge increase in aperture it lends to amature telescopes. Dust lanes and connective spiral arms are clearly in evidence here. The best naked eye views of the Whirlpool I’ve seen have only really resolved the two central cores of the interacting galaxies. You generally need a scope of 16 inches or more to reveal dust tendrils in this much detail.
This is how the Earl of Rosse sketched the galaxy back in 1845 with his monstrous 72 inch dobsonian from the grounds of Birr Castle in Ireland.
Of course back then these structures were given the loose classification of ‘nebulae’ and were assumed part of our local galaxy. It wasn’t until the 1920s when Edwin Hubble observed cepheid variable stars within each bright core of the Whirlpool that this image was understood to be two distinct but interacting galaxies, the larger of which has been estimated to be 35% the size of our own Milky Way galaxy.
M51 is still a hot target for professional astronomers, not least because of the black hole that exists within the heart of the larger galaxy. This central region is undergoing rapid stellar changes and star formation.