The Hubble Telescope, Two Decades of Discovery

The Hubble Telecope in Earth orbit in 1997

The Hubble Telescope, possibly the most important scientific instrument ever built. Just hearing the word Hubble conjures up images of the universe, majestic spiral galaxies, vast pillars of gas and dust, nebulae, and planets in exquisite detail. The $1.5 billion Hubble Space Telescope, orbiting 600 kilometres above the Earth and far above it’s hindering atmosphere, has shown us our solar system and the universe in a clarity that was never seen before it’s launch in 1990. It has “burrowed” through space and time to take pictures of galaxies and galaxy clusters that show us how they were millions and even billions of years in the past. The terms “Hubble Deep Field”, and “Hubble Ultra Deep Field” are now are now in our common language, and even familiar to people who just about have a passing interest in astronomy. Hubble has enriched our lives and opened a window to the immense beauty and grandeur of the universe. Hubble images can be found everywhere from cd covers to screen savers, to framed pictures and postcards.

The telescope is named after a brilliant American astronomer called Edwin Hubble. In the early 20th century he was responsible for, among other things, demonstrating that the Milky Way Galaxy was not the entire universe but that more galaxies actually existed outside it. He also discovered redshift, the way by which light is stretched towards the red end of the spectrum depending on how fast an astronomical object is travelling away from us. He fundamentally changed our ideas about our place in the cosmos, and it’s true scale.

The Hubble Telescope was the result of 20 years work between scientists and engineers from Nasa and ESA. They knew full well that our atmosphere does a great job of blurring the pristene light that has travelled undisturbed for millions and billions of years across the universe. The swirling layers of warm and cold air, dust, and water vapour in our atmosphere make stars “dance around” in a telescope and twinkle to the naked eye. The twinkling isn’t the star itself, it’s just out thin atmosphere effecting the starlight. As early as 1923 it was suggested that putting an observatory into space would be a huge leap forward. But it wasn’t until the late 20th century that the technology existed to actually realise this.

On 24th of April 190 the Hubble was blasted off from Cape Canaveral on board the Space Shuttle Discovery.

It was deployed 600 kilometres above the Earth in an orbit taking 97 minutes. Initially the images sent back from the Hubble Space Telescope failed to impress and were a huge disappointment to astronomers, the pictures just weren’t as sharp as expected.

An initial image of spiral galaxy M100 taken by Hubble

The images were actually no better than from Earth based observatories, something wasn’t right. It was discovered that Hubble’s 2.4 metre mirror was not perfect, it was flattened at the edges by an amount of 22 microns, equal to 1/50th the thickness of a human hair. Even this tiny flaw was causing images of astronomical images to be fuzzy, a solution had to be found. Scientists came up with COSTAR (Corrective Optics Space Telescope Axial Replacement), kind of like a contact lens for the telescope. In December 1993 astronauts aboard the Space Shuttle Endeavour arrived at Hubble for a service job in order to correct it’s optics.

M100 after the COSTAR mission to correct the Hubble’s optics

The images sent back were astounding, even better than astronomers had dared hope for, the mission was a great success. The groundbreaking telescope soon started returning fantastic images from space with it’s razor sharp vision.

The Cone Nebula, a 7 light year long pillar of gas and dust 2,500 light years away that is an incubator for newly forming stars.

The famous Horse Head Nebula

But one of the most stunning moments in the Hubble Space Telescope’s history was the time in December 1995 when for 10 consecutive days it stared at a tiny patch of sky, a “keyhole” equal to the size covered by a tennis ball at 100 metres away. This was a seemingly black part of the sky with no real objects of interest, or so we thought. Some even questioned it’s usefulness and said it was a waste of the telescope’s valuable observing time. Taking 342 exposures over 10 days, it gazed at the same patch of sky. The weak light coming from galaxies billions of light years away, stretching back to near the beginning of time, dribbled into the Hubble’s sensors, and astronomers unveiled an amazing scene.

The tiny area of sky covered by the Hubble Deep Field image

The Hubble Deep Field,a startling assortment of galaxies including ones as faint as 30th magnitude, 4 billion times fainter than the limits of the human eye.

Around 3,000 objects are contained in this image, most are entire galaxies. The very fainter and redder ones are also the very youngest, showing galaxies at earlier stages of formation than those in the foreground. This image was met with astonishment around the world as it became apparent just how vast and stunning the universe really is, more unbelievable than anyone could imagine. This was a truly humbling image for humanity. How could such a small and insignificant bit of the sky contain so many galaxies? The Hubble had set the benchmark and this was only the start of the story. The telescope gave us thrilling views of the planets and moons in our solar system, seeing weather patterns, aurora, erupting volcanoes, comet impacts, and changing seasons. Further afield it has returned images of the cosmos that often look like unforgettable works of art. Colourful and intricate nebulae, star factories in our Galaxy and others, star clusters, galaxy collisions, gas clouds, galaxy clusters, gravitational lensing, supernovae, black holes and more. As aesthetically pleasing as these images are, they are based in pure science and are incredibly valuable. In 1999 Hubble observations were paramount in the discovery that gamma ray bursts were coming from distant galaxies. In 2001 the Hubble made the first detection of the atmosphere of an extra solar planet, and partially determined it’s make up. It was the very first telescope to see details in the thin arcs of light created by a gravitational lens, and also determine the form in the galaxy’s smeared light. But the Hubble Space Telescope hadn’t finished yet and was still set to amaze, with the deepest image of the universe ever taken, looking back 13 billion years to the very edge of time itself. From September 2003 to through to January 2004 it again gazed at the sky. This time it peered at a patch of sky in the constellation Fornax, equal to a 1 millimetre square piece of paper held 1 metre away. This was the Hubble Ultra deep Field, an image containing up to 10,000 galaxies including among ones that were the first to light up the infant universe in the so called “dark ages”. Some of the smallest and reddest galaxies in this image show them at a time just 400 million years after the Big Bang itself.

The Hubble Ultra Deep Field, showing galaxies back to near the beginning of time.

The scientific results from the Ultra deep field include the realisation that star formation was at a high rate in the development of early galaxies, under a billion years after the Big Bang. Also that galaxies with higher redshifts are smaller and less symmetrical than those with lower redshifts, showing that early galaxies evolved at a faster rate. It was also realised that this was the typical distribution of galaxies in the universe no matter what direction you look in. At the time of writing the Hubble is 19 years old, already 4 years past it’s original foreseen lifetime. But the telescope was designed to be serviced and upgraded with new and improved scientific instruments. The aging telescope that started out as a design drawing in 1981 was given a boost in May of 2009, making it even more sensitive to light than ever. Astronauts aboard the Space Shuttle added the Wide Field Camera 3, making it even more powerful and stretching it’s life to 2014. They also removed the original COSTAR equipment. The telescope recently showed off it’s new capabilities with stunning images of the cosmos, and is hopefully destined for more scientific breakthroughs to come.

Hubble’s achievements over the years include helping astronomers come up with an age for the universe, between 13 and 14 billion years old. The discovery of dark energy, an unseen force in the space that is causing the universe to accelerate in it’s expansion. Of course the Hubble Deep Field images that have allowed astronomers to probe the structure and development of galaxies in the infant universe. The telescope has helped astronomers in their search for even more extra solar planets, and has detected the chemical composition of their atmospheres. The Hubble Space Telescope has provided the proof of mammoth black holes that inhabit most galaxies. That gamma ray bursts, extremely powerful but short blasts emanate in far off galaxies. Providing astronomers with data to understand more about quasars at the centres of galaxies. Showing astronomers the proto-planetary disks around newly forming stars, and that this process is very common. Showing Science the intricate structure of planetary nebulae, and also determining that no two are the same. We had a ringside seat when Comet Shoemaker-Levy 9 slammed into Jupiter in 1994, the Hubble gave us amazing pictures of the comet and the impact scars. At the time of writing Hubble is on course to operate for a little over 4 years more, taking it’s lifetime to 24 years, 9 years longer than originally expected. Eventually the working parts of the Hubble Space Telescope will cease after no more service missions are made, and Nasa will de-orbit the telescope using soft capture. this will be performed using the next generation of space transportation vehicles, “grabbing” the Hubble and pulling it safely from it’s orbit. A ring like device has already been fitted to the Hubble’s bulkhead for when that time comes.

With the eventual demise of the most successful telescope ever constructed, an even more sophisticated peice of hardware is destined to take it’s place. The James Webb Space Telescope is set for launch in 2014 and will mainly operate in the infrared end of the spectrum, but also have capabilities in the visible. But until then we can look forward to more astounding images and science with the new improved Hubble Space Telescope.

DISCUSS this, or go to the HOME PAGE

Comments are closed.

© 2012 Astronomy Central
Proudly powered by WordPress Top ↑