Why look up at the night sky?

Another article in the series where Milky-Way.kiwi explores why we look up, what inspires us to observe and be interested in space. This time we consider how inspiring and amazing galaxies are.

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Galaxies are amazing.

If there is one reason to look up at the night sky it’s to fill your eye ball with ancient photons from millions of light years away.

Even though they may not look that impressive in the eye piece of the standard backyard telescope, galaxies are truly mind boggling. They are the only things that allow us to conceptualise how our own galaxy, the Milky Way, might look like. The scale of the distances are immense and the shapes and varieties of these enormous structures are enough to push the limits of anyone’s imagination.

The amazing thing is that we didn’t know there were other objects external to our own galaxy until Edwin Hubble made some astonishing observations of Cepheid variables. These observations enabled him to determine that some of the smudges, known at the time as nebulae, were in fact from outside of our own galaxy. Up until that time we just thought that our galaxy was the one and only, no others, just us.

Now that we know there are billions and billions of galaxies, nowhere is this more amazing than when you consider that the Hubble Space Telescope (HST) deep field and ultradeep field images were deliberately taken of a patch of sky chosen to be “as empty as possible“. It is fascinating that in any direction there are millions and millions of galaxies all stretching back to the dawn of the universe. The below image is the Extreme Ultra Deep Field image from NASA, which is a combination of ten years worth of data and contains about 5500 galaxies in its tiny field of view. The brightness of the objects are as little as 1 in 10 billion of the brightness of what the human eye can detect.

The distances between galaxies are truely mind boggling and its not hard to to come to the conclusion that it would be almost impossible to travel between them. Aside from the small galaxies such as the Small and Large Magellanic Clouds, the nearest galaxy to us is the impressively huge Andromeda Galaxy. This is about 2 million light years away, which is an extraordinary distance when you consider that the photons that enable us to “see” this galaxy set out on their journey long before humans even existed.

There’s some time-dilation effects that make it seem it might be possible to travel as far as Andromeda. Imagine you have a spacecraft that can accelerate constantly at 1G, and imagine you are on the spacecraft – don’t worry about any observers on Earth, as you will never see them again. If you accelerated your ship for 14 years at 1G you would be half way to Andromeda Galaxy, and almost at the speed of light. So at this point you need to decelerate your space ship at 1G, quite a comfortable ride really. So once you get to Andromeda, it’s been 28 years on your space ship. If you decide you don’t really like it and turn around to do the same trip home it will also take you 28 years, so 56 years for the round trip. Unfortunately you probably won’t be too happy at what you return to as that would be millions of years into the future, what you would return to would be completely unrecognisable, such is the weirdness of time dilation when travelling near the speed of light. Now that’s the problem of travelling to the closest big galaxy to us.
I took this photo of Stephen’s Quintet and the some of the galaxies in this group are 340 million light years away. That means that when the light that was captured in this photo started its journey, life on earth was radically different, amphibians were just branching off into reptiles – dinosaurs were still a long way off. Travelling to this group as above would put you closer to a billion years into the future if you decided to come back.

My own photo of Stephen’s Quintet

Galaxies are aesthetically pleasing

The most impressive looking galaxies are the face on spirals, and hence why they are the most photogenic. What is amazing about them is that they show the effects of rotation through their spiral arms. The stars orbit the centre, generally, and the spirals arms kind of migrate their way around as well. The spiral arms are sort of waves of star formation areas where the gases are slightly more compressed than the areas between and hence appear more active and have more stars and nebulae. This photo is of IC342, a really beautiful face on spiral that’s not often imaged because it sits along the plane of the Milky Way so is difficult to see.

My own photo of IC432

The variety of galaxies are amazing and when you think about what you are looking at then the it is truely mind boggling to think about the scale of the distances and the number of stars. Many of the galaxies that are visible to reasonably powerful telescopes have billions and billions of stars so it is staggering to consider how many of those stars may have planets and how many long lost civilisations you could be looking at all those millions of light years away.