NASA's next big space telescope reaches a critical stage

The space telescope that will one day replace NASA's Hubble Space Telescope (HST) has reached a critical stage in its construction this month as work entered the final assembly phase. Engineers working on the James Webb Space Telescope (JWST) started installing its mirrors last fall and by December had fitted 9 of the 18 primary flight mirrors. This month they started on the 10th mirror and the final stage of the assembly process.

The team is using a precise robotic arm to carefully position the massive gold-coated mirrors onto the growing observatory. Inside the huge clean room at NASA's Goddard Space Flight Centre, the massive observatory is starting to take shape.

Engineers installing the 9th primary flight mirror onto JWST
(Credit: NASA)

The 18 hexagonal-shaped primary mirrors each weigh approximately 40kg and measure over a metre in diameter. They were built at the Ball Aerospace labs in Boulder, Colorado, and then transported to NASA's laboratory in Maryland. Together they will produce a single mirror 6.5 metres across, making JWST the largest space telescope ever constructed.

Construction work is on schedule for completion in time for a launch in 2018. Once constructed and launched JWST will have the light-gathering power to peer back in time to when the first stars and galaxies were forming in the Universe. By observing these objects astronomers hope to understand how the Universe that we see around us was constructed. JWST will also aid the ongoing search for habitable exoplanets, the study of nearby forming stars and star clusters, and the large-scale structure of the Universe.

Artist's impression of the completed James Webb Space Telescope with its 18
gold-coated mirrors and large sun shied at the bottom (Credit: NASA).

Look out for more news on JWST's construction, mirror installation, and testing!

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.

The Lagoon Nebula

This week I've been studying a young star cluster known as NGC 6530, which is embedded within a famous region known as the Lagoon Nebula. This is one of the most famous nebulae in the sky, and a very attractive target for astrophotographers. Below you can see an image of the Lagoon Nebula that I made, and I think you'll agree that the nebula really does look very lagoon-like!

The Lagoon Nebula as imaged by VPHAS+ (Credit: Nick Wright)

The data for this image comes from the VPHAS+ survey (the southern-hemisphere counterpart to the IPHAS survey), which is being run from the European Southern Observatory's VLT Survey Telescope (the VST) in Chile. We compiled this data for ESO last year to help them with a press release, which they used to produce their own image that you can see here. Their image is nice, but I greatly prefer my own because I think we've retained the lagoon-like swirling clouds of gas much better than they have. What do you think?

The NGC 6530 cluster in the centre of the Lagoon Nebula

The Lagoon Nebula is interesting for astronomers like myself because it's a region where stars are actively forming, and you can even see a cluster of stars that have already formed in the centre of the nebula. This cluster, known as NGC 6530 is about 2 million years old (which is quite young for stars!) and contains many thousands of stars, though only the brightest few dozen can be seen in this image.

The nebula can be found in the constellation of Sagittarius, and despite being about 5000 light years from Earth can actually be seen with the naked eye from a very dark sight (though you'd be better off with a pair of binoculars). Unfortunately, even with binoculars the nebula doesn't look as red and purple as these images suggest, but more of a greyish colour. The reason for this is that under low light conditions human eyes are not good at distinguishing colours, and so most faint things appear grey.

The reddish hue of the Lagoon Nebula seen in most astronomical images comes from the fact that most of the light we see comes from a bright emission line known as Hα ('H alpha'), which is a very prominent emission line from the element Hydrogen that can be found in the red part of the electromagnetic spectrum (hence why we astronomers colour these images red to reproduce their real colour).

The 'Hourglass Nebula" in the centre of the Lagoon Nebula

The nebula is illuminated by a number of very massive, young stars that ionise the hydrogen in the nebula and cause it to glow. It is amazing to think that this entire nebula, approximately 100 light years across, can be illuminated by just a handful of bright stars - but these stars are really bright!

There's a lot of small scale structures within the nebula that this image reveals, including a number of prominent dust globules that are silhouetted against the bright nebula. Perhaps the most famous structure within the Lagoon Nebula is the Hourglass Nebula at its heart. This is a very dense and compact ionised nebula where stars are still forming and which is being ionised by a very young and still embedded, massive star. The Hourglass nebula was actually discovered by the astronomer John Herschel, son of William Herschel, so it's quite exciting to be studying a region previously studied by such a famous astronomer!

This is all particularly timely because of a recent paper that presents high-resolution Hubble Space Telescope images of the hourglass nebula (see below). These observations are much higher resolution than our VPHAS+ images and they're much more detailed, but they only cover a small part of the entire Lagoon Nebula. That is one of the great advantages of large-scale surveys such as VPHAS+, they cover everything!

The Hourglass Nebula as seen by the Hubble Space Telescope
(Credit: Maiz Apellaniz et al. 2014)

The detail in this image is really impressive, and the authors of the paper have done some interesting science with it, detecting evidence of the massive star Herschel 36 being a binary system amongst other results. All of this makes the Lagoon Nebula a really interesting scientific target, which makes me feel very lucky to be studying it at the moment!