Date:  January 29, 2009

Title:  Telescopes in Space

Podcaster:  Pauline Barmby

Organization:  University of Western Ontario

Description:  Many people have heard of the Hubble Space Telescope. But it wasn’t the first telescope in space, and it’s not alone up there.  Why do we put telescopes in space? What kinds of space telescopes are there? How do they work, and what do they observe? What have we learned from space telescopes, and what can we expect from future space astronomy missions?

Bio: Pauline Barmby is an assistant professor at The University of Western Ontario in London, Canada. She studied at the University of British Columbia and Harvard University. As part of the team that developed one of the instruments for the Spitzer Space Telescope, she has used the telescope to study galaxies and star clusters.

Today’s Sponsor:  This episode of “365 Days of Astronomy” is sponsored by Cryo, hobby astronomer from Austria. Dedicated to every astronomer, from the the early days of humankind to the present and those who will come. Thank you for your endless efforts on expanding our view of the universe.

Transcript: 

Hello and welcome to 365 days of astronomy. I’m Pauline Barmby, an assistant professor of physics and astronomy at the University of Western Ontario in London, Canada. I’m happy to be doing today’s podcast to tell you about telescopes in space.

Lots of people have heard of the Hubble Space Telescope, which produces many of the beautiful astronomical pictures you see in newspapers and magazines. But the Hubble wasn’t the first space telescope, and it’s not currently alone in space either. In today’s podcast I’ll try to tell the story of space telescopes: why we build and launch them, what they do, and what we’ve learned from them.

Why do we put telescopes in space? Putting anything into space is very expensive, so there has to be a good reason for it. You might guess that we put telescopes in space to get them the closer to the objects we want to observe. But the only places we can really send our spacecraft to are the Sun and the other planets in our solar system. The stars and galaxies are just too far away, and putting telescopes into space just doesn’t get you closer in any useful way. So why space, then?

We put telescopes in space to get them away from the Earth’s atmosphere. You’ve probably seen the stars twinkling at night. If you look carefully, you might notice that the stars near the horizon are twinkling more – that’s because the twinkling is caused by the atmosphere, and near the horizon the light has to go through more atmosphere.  Putting a telescope in space means that it doesn’t have to look through the atmosphere, so the stars don’t twinkle. No twinkling means that the images made by a telescope in space are much less blurry than those from a telescope on the ground. And less blurry images mean that we can see more detail and fainter objects. So getting above the Earth’s atmosphere is a big help, and it’s why the Hubble Space Telescope has been so successful.

But making stars twinkle is not the only thing the Earth’s atmosphere does. It also blocks many wavelengths of light, including X-rays, ultraviolet, and infrared light. For those of us who live on Earth, this is a good thing: blocking X-rays and UV light keeps us from getting irradiated by the high-energy radiation from the Sun, and blocking outgoing infrared from the ground helps to keep the Earth warm. But for astronomers who want to find out what the universe looks like at X-ray, ultraviolet, and infrared wavelengths, this means that their telescopes have to go into space.

How do telescopes get into space? We put them on spacecraft and launch them, either with the Space Shuttle or unmanned rockets. The telescopes themselves often look quite a bit like telescopes on the ground; the spacecraft does the important job of pointing the telescope at the right place in the sky, and sending the data down to the ground by radio. Generally the schedule for what a space telescope will observe is planned out in great detail far in advance. Only a few of the astronomers who want to use space telescopes get to do so: every observation has to be justified in a written proposal to a committee, and the committee picks just the best observations to do. With some telescopes, only 10% of the proposed observations can be done.

The idea of launching telescopes into space had been around for quite a while, even before the first satellites were launched.  But the first telescopes to make it into space were launched in the early 1970s by the American and Soviet space programs. It takes a long to time plan and build space telescopes: both the Hubble and Spitzer Space Telescopes were proposed more than twenty years before they were eventually launched.

What telescopes are in space now? The famous Hubble Space Telescope has been in orbit around the Earth since 1990 – more than 18 years. As you might know, it was launched with a problem in its main light-gathering mirror. Astronauts installed corrective optics – think of them as “glasses” — in 1993, and the telescope has been taking great data ever since. It’s due for its final “servicing mission” in May 2009 – space shuttle astronauts will visit it to install new cameras, batteries, gyroscopes, and other equipment.

Many people have heard of Hubble, but you might not have heard of its sister telescopes – the other missions that make up NASA’s “Great Observatories”. The first of these was the Compton Gamma-Ray Observatory, which was launched in 1991 and finished its mission by being “de-orbited” into the Pacific Ocean in 2000. The next Great Observatory is the Chandra X-ray Observatory, launched in 1999 and still going strong. The last Great Observatory is the Spitzer Space Telescope, launched in 2003. I have a soft spot for Spitzer since I spent several years working on the team responsible for one of its cameras. There are at least half a dozen more space telescopes besides the great observatories; unfortunately I don’t have time to describe all of them. If you want more information, try looking up GALEX, MOST, COROT, XMM-Newton, Swift or Fermi-GLAST online.

So what have space telescopes done for us? Besides making absolutely fantastic pictures, Hubble has been used to make some very important scientific discoveries, such as the acceleration of the universe’s expansion, and the presence of black holes at the centers of nearly all galaxies. Chandra has measured the X-ray light that these black holes emit and helped to map dark matter in galaxy clusters. Spitzer has been used to find some of the most distant galaxies in the universe, and has also made the first detections of light from planets around other stars – which hadn’t even been imagined when Spitzer was first designed.

What’s next for space telescopes? Spitzer is almost out of the liquid helium used to cool its telescope and cameras to nearly absolute zero, but one of its cameras will continue to work for several more years. Hubble should also be good for several more years, although there are no plans to service it again after 2009. Chandra’s orbit is such that it’s not serviceable, but it seems to be working fine and could operate for another decade. There are many new and exciting space telescopes that will be launched soon: sometime in 2009, the Kepler mission will start looking for the shadows of Earth-sized planets crossing in front of their stars. Also in 2009, the European Herschel Space Observatory will be launched, observing the universe at infrared wavelengths mostly longer than those Spitzer was sensitive to. And in several more years, the James Webb Space Telescope – Hubble’s successor – will begin to look for the light from the first stars in the universe.

It’s an exciting time to be an astronomer, and I hope I’ve given you some idea of what the capabilities of space telescopes allow. For more information on any of the telescopes I’ve mentioned, you can look them up on the Internet with your favorite search engine. They all have websites with great pictures and lots of information, and many have podcasts with the latest news. Thanks for listening!

365 Days of Astronomy
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