Happy 25th Birthday Hubble!
The 25th anniversary of the Hubble Space Telescope’s launch marks a transition in astronomy. As one symbol of mankind’s leap forward in space exploration winds down, it’s time to look at what it’s successor will offer and what legacy Hubble will leave behind. That successor will be the James Webb Space Telescope, named after NASA’s second Administrator.
To understand the potential that Webb has we need to look back to the beginnings of Hubble to see what made this the most successful telescope on the planet. During the last 25 years Hubble has captured some of the most iconic images of our Universe, and supplied scientific data for thousands of pieces of research. But more than that, it has revealed the vast, breathtaking and rich tapestry of space around us from warm, glowing galaxies to towering pillars of dust in far off nebulae.
Hubble was launched in 1990 to measure the size and age of the Universe, a puzzle that has occupied astronomers since we first started to observe the stars around us and our place within them. In doing so, the images it recorded could be used to test theories about the origins of the Universe. How? By looking back in time.
Time machine
Land-bound telescopes face the challenge of peering into space through the Earth’s atmosphere. As light from space reaches us on Earth it is distorted and filtered by particles in the air, causing the twinkling effect we can see with our eyes when we look at the stars from Earth. This means that the faintest signals from deep space are lost a long time before they even reach us.
By orbiting the Earth at an altitude of 570km, Hubble avoids interference from the atmosphere, allowing it to see deeper into space with greater fidelity. Because of this we have the stunning images that have made this instrument so iconic.
The atmosphere also filters by wavelength, with infrared radiation lost before ultraviolet radiation. This infrared radiation is very important to proving that the Universe is expanding. Scientists observed that the wavelength of light travelling from the furthest reaches of space was changing – the light was being stretched.
Redshift
This effect could only happen if the Universe is expanding. As the light travels through space, the space expands stretching the light waves too, albeit only by very small amounts. The stretched waves reach us at a lower frequency than the one with which they left their home star. This distorts the information almost like sound being played at half speed, except that light cannot change its speed, instead it shifts in the colour spectrum towards red. The greater the distance the light waves travel, the closer they get to red, and over very great distances the waves move entirely into the infrared end of the spectrum. This is called ‘redshift’.
So if Earth’s atmosphere filters out infrared radiation, our telescopes will never be able to look into the further corners of the Universe. And this is where we can see our origins. Because light takes a long time to reach us from distant stars the waves we can detect now actually left the stars millions of years ago. The stars whose light has been shifted into infrared radiation are those that are furthest away from us, and whose light originated closest to the Big Bang. Hubble’s sensitive instruments were able to detect light from 13.2 billion years ago – farther than ever before in time and space – and to within 600-700 million years of the Big Bang. Anything beyond this is out of Hubble’s reach, and this is where Webb comes in.
Hubble vs Webb
Webb will be a specialist infrared detecting instrument able to delve even further back to within 100-200 million years of the start of our young universe, at a time of great activity. It should reveal fascinating insights into the unsettled adolescence
Webb will not actually orbit the Earth – instead it will sit in a small orbit around the Earth-Sun L2 Lagrange point, 1.5 million km away. At this point Webb will be shielded from radiation from the Sun, Earth and Moon which would otherwise throw off the very sensitive infrared detecting instruments. In order to take very accurate measurements the instruments must be kept cold so Webb’s operating temperature is less than 50 degrees above absolute zero (-223° C).
Webb will have a 6.5 meter diameter primary mirror, which would give it a significant larger collecting area than the mirrors available on the current generation of space telescopes. Hubble’s mirror is a much smaller 2.4 meters in diameter and its corresponding collecting area is 4.5 m2, giving Webb around 7 times more collecting area.
Here at team VISU.AL, we were of the opinion that an infographic would help explain and contextualise the differences between the Hubble and Webb, so with the magnificent research provided by Will and information design by Nigel, we went ahead and created one.
Big Bang to Big Science
Since the World War II, the huge, publicly-funded science projects that define generations of scientific research – projects like the Gemini and Apollo space missions, Human Genome Project and more recently CERN – have come to be known as Big Science. When we look back at the timeline of scientific advance the second half of the 20th Century is divided into epochs defined by these Big Science projects. For the 1990s this was Hubble.
Hubble invites a mixture of feelings. On the one hand, it shows the tremendous advancements we have made in space technology to not only launch and control a telescope orbiting our planet at 19,000 mph but to fix it, modifying and give it a new life when it falls into disrepair. However, the work that it does goes only to show how small and remote we are in the grand scheme of things.
The decision to retire Hubble was made in 2003 after the space shuttle Columbia disaster, but it was briefly reprieved. Hubble was serviced for one final time in 2009 and expected to run for only another 5 years with those modifications, so at this stage every day is ‘extra’ time.
The launch of Webb can’t come soon enough for astronomists. Hubble showed us what is out there, it showed us the beauty of planet nurseries, it revealed the power of the supermassive black holes at the centre of the largest galaxies. Now the next step is to learn why. The success of Webb will be measured by how close it can get us to answers about the earliest moments of our universe.
For now let’s celebrate the past, embrace the present and anticipate the future.
