Friday, 24 April 2015

Happy 25th Birthday Hubble Space Telescope!

On this day 25 years ago the Space Shuttle Discovery was launched from the Kennedy Space Centre on Cape Canaveral in Florida. After launch the Space Shuttle rose to an altitude of 380 miles and began to orbit the Earth. In the days that followed the crew of the Space Shuttle opened the shuttle's cargo bay doors and deployed its valuable payload, the Hubble Space Telescope.
The launch of Space Shuttle Discovery, with the
Hubble Space Telescope on board (Credit: Wikipedia)

That was 25 years ago, and ever since then the Hubble Space Telescope has acted as the world's premier astronomical observatory. In that time Hubble has made an immeasurable contribution to our understanding of the cosmos, from measuring the speed of the expansion of the Universe, finding the first evidence for dark energy, and discovering planetary systems forming in the Orion Nebula.

The Hubble Space Telescope is not the only astronomical observatory in space, in fact there are dozens of them. It wasn't the first such observatory and it certainly won't be the last, but it is probably the most important, not just for the scientific discoveries it has made, but also for how it has brought those discoveries, as well as thousands of beautiful images of the cosmos, to the public. In this article I want to share some of those images, and the science behind them, with you all.

The Pillars of Creation in the Eagle Nebula, imaged by the
Hubble Space Telescope in 1995
(Credit: Hubble Space Telescope)
Perhaps one of the most famous images taken by the Hubble Space Telescope, and one of the first to lodge itself firmly in so many people's hearts, is the magnificent image of forming stars in the Eagle Nebula. The image, which was quickly dubbed the Pillars of Creation because of the stars being created within the nebula, showed for the first time the amazing detail in star forming regions such as this. The pillars themselves, sometimes referred to as elephant trunks, are giant clouds of gas and dust that are being slowly eroded by a cluster of massive stars just above this image. Those stars are sculpting and eroding this cloud of gas and dust, and potentially, as was later shown, halting the star formation process within them. The Hubble Space Telescope revisited this image as part of the 25th Anniversary celebrations this year, producing a new, larger and higher-resolution image of this amazing nebula.
The merging Antennae Galaxies, imaged by the
Hubble Space Telescope in 2006
(Credit: Hubble Space Telescope)

The Hubble Space Telescope didn't just spend its time imaging star forming regions like this, it also produced a huge number of very detailed images of distant galaxies. One of my favourite images of these galaxies is that of the Antennae Galaxies that has been imaged by Hubble multiple times, most recently in 2006. The Antennae are actually two galaxies that are in the process of merging as they interact, and this interaction has quite radically torn these galaxies apart, as the image shows. This apparent destruction has, rather paradoxically, led to a very brief but intense period of star formation that astronomers refer to as a starburst. The Hubble Space Telescope images are so detailed that they have allowed astronomers to study the star formation in these distant galaxies and even resolve individual star clusters within them. Getting such a detailed view of this important phase of galaxy evolution has been really useful for astronomers to understand how galaxies merge.

The Hubble Deep Field, imaged by the
Hubble Space Telescope in 1995
(Credit: Hubble Space Telescope)
Perhaps one of the most unique images taken by the Hubble Space Telescope is that of the Hubble Deep Field, which was imaged in 1995 from 6 days of exposure of an apparently empty patch of sky. This tiny area, one 24-millionth of the entire sky, was chosen because it was almost completely devoid of any stars and galaxies. The questions astronomers were effectively asking by taking this image was, what will we find in the darkest and emptiest areas of space?

The answer was that this apparently empty area of space was actually full of galaxies! Almost all of the 3000 objects in this image are distant galaxies, billions of miles away. Some of the galaxies are so distant that it has taken almost the entire age of the Universe for their light to reach us, allowing us to see what they looked like when the Universe was very young. Images like this have been vital for helping astronomers understand both the large-scale structure of our Universe as well as how galaxies have changed over the lifetime of the Universe.

Finally I want to end with a new image taken by the Hubble Space Telescope very recently. This image was released to the public yesterday to celebrate the 25th Anniversary of the launch of the Hubble Space Telescope, and you can see this amazing image below.

The Hubble Space Telescope's 25th Anniversary special image release showing the massive star cluster
Westerlund 2 and surrounding nebulosity (Credit: Hubble Space Telescope)

The image shows the massive star cluster Westerlund 2, one of the most massive clusters of young stars in our Galaxy (and one which I have studied in the past and talked about before on this blog). This image is so large and detailed that not only can you make out many hundreds of young and massive stars in this cluster, but you can also see the beautiful nebula that surrounds the cluster and make out young stars forming within it! This is an amazingly detailed image, which I encourage you all to have a look at in more detail here.

You can see more images like these on the Hubble Space Telescope's gallery webpage, or follow the various events celebrating this anniversary on the Hubble Space Telescope's 25 Years webpage. Over the next few months I'll talk more about some of the amazing discoveries from the Hubble Space Telescope, the history of how this great observatory came to be, and the exciting telescope being built to replace Hubble in the next few years.

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