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.

Saturday, 18 April 2015

Lyrid Meteor Shower - Visible in the night sky now!

Next week the night sky will be graced with one of the most impressive meteor showers of the year, the Lyrids, which will be visible for all of next week, peaking on the 22nd and 23rd of April.

A Lyrid Meteor visible passing across the Milky Way (Credit: NASA)

Meteor showers are caused by lots of tiny particles colliding with the Earth's atmosphere, being heated up and briefly glowing brightly as they burn up. The Lyrid Meteors are caused by particles shed from a comet called C/1861 G1 Thatcher, which was discovered by A.E. Thatcher in 1861. While the comet itself has been known about for over 150 years, the Lyrids were first seen over 2,600 years ago, making them the oldest known meteor shower.

This year's Lyrid meteor shower promises to be a wonderful sight, not only because astronomers are expecting 10-20 meteors visible per hour, but also because the Moon will be a slender crescent on the 22nd and 23rd of April, making it much easier to observe the meteors.

The meteor shower should be visible (weather permitting!) from the entire Northern hemisphere, as well as much of the Southern hemisphere. While the meteors will emanate from the constellation of Lyra (hence the name Lyrids), they will pass across the entire sky, so wherever you look you should be able to see them. You don't even need a telescope, just get away from the bright city lights and look up!

Monday, 13 April 2015

Last week's Lunar Eclipse

Last week stargazers across the Pacific, from Australia and eastern Asia to the west coast of the USA were treated to a stunning lunar eclipse. A lunar eclipse occurs when the Earth blocks the path of the light from the Sun to the Moon, making the moon go dark.

Lunar eclipses are wonderful celestial events to watch, partly because they take longer to occur than a solar eclipse, so it can be easier to observe them, but also because at the moment of totality the Moon briefly appears a reddish-brown colour, leading to the nickname of such events as blood moons. This red colour is caused by a small amount of sunlight passing through the Earth's atmosphere, where it is refracted and reddened (much like the light from the Sun at sunset), and then illuminating the Moon. While this phase only lasts a few minutes, it can be very impressive!

A photographic montage showing the total Lunar Eclipse on April 4th, 2015 (Credit: Roger Clark)

The photograph above from Roger Clark shows a montage of photos of the moon taken during the eclipse, progressing from an un-eclipsed moon on one side, followed by a partially-eclisped moon, then a fully eclipsed blood moon, and then followed by partially and un-eclipsed moons as the eclipse finished. This sort of photographic montage not only shows the lunar eclipse happening, but also highlights the path of the moon across the night sky during the eclipse.

If you missed the eclipse then don't worry, the next total lunar eclipse will be on September 28th, 2015, and will be visible to stargazers in the Americas, Europe and Africa. It should be good!

Thursday, 2 April 2015

Milky Way Astrophysics from Wide Field Surveys - Part III

The final day of the Wide Field Surveys meeting started by focussing on the later stages of a star's life, including red giant stars (big, bright and red), asymptotic giant branch stars (bigger, brighter, and redder!), planetary nebulae (a type of dying star), and white dwarfs (the final remnant of a dying star).

The focus then shifted to star clusters, which is my area of interest, and in fact this was when I gave my own presentation to the audience, and then finally there were presentations and discussions about future surveys, which can be useful to think about what research might be possible in the future.

All in all its been a very interesting meeting, with a wide array of science topics covered, which has been useful to stay up to date in current research results in different areas. I'm now a little exhausted though, so I'm looking forward to the long weekend to relax!