05 Nov Astronomy in the rain
It’s a beautiful summer night, the sky is clear and gazing at the firmament, you see billons of stars. Astronomers study these miracles of nature using telescopes, but what do they do when clouds hide the miraculous lights in the sky? If only there was a way to overcome this obstacle. Luckily there are magical telescopes that can look through the clouds: radio telescopes.
Looking through clouds
In autumn astronomers in the Netherlands have to be very lucky to see a clear sky. Does this mean the scientists just sit back, relax and eat apple pie while they wait for the rain to stop? No! They decided to build telescopes that can look through those dark clouds. Not only visible light, but also radiation in the radio spectrum is emitted by astronomical objects. This radiation travels easily through clouds and fog and can be detected by radio telescopes. The Netherlands has three of these telescopes: the Westerbork Radio Synthese Telescoop, the Dwingeloo-telescoop and since 2010 part of the biggest radio telescope in the world: LOFAR.
Information hidden in radio waves
Looking through clouds is a neat trick, but how useful is it? What information do radio waves carry that we can’t learn from visible light? Not only earthly clouds, but also nebula in our galaxy can hide astronomical secrets from our sight. It’s the radio waves with wavelengths of about a millimetre up to a few meters which can penetrate through all these clouds, to reveal the mysteries behind them. Visible light, with much shorter wavelengths, gets deflected in the clouds. The long radio waves do not suffer from this effect and travel through the (inter)galactic dust. So, the discovery of radio astronomy led to a more complete picture of previously hidden galaxies and our own Milky Way.
Furthermore, some information is only available in radio waves. Some examples of stellar “objects” that are studied using radio astronomy:
- Quasars (or quasi-stellar radio sources): a compact region in the centre of a massive galaxy surrounding a central supermassive black hole. As the name suggests, they send out radio waves. They also emit visible light, but this often does not reach us, because they are surrounded by dust.
- Cosmic Microwave Background radiation (CMB): the oldest “light” in our universe. It teaches us about the birth and first growth of everything we see around us today. The discovery of this famous radiation was made through radio astronomy.
- Pulsars (or pulsating radio star): a highly magnetized, rotating neutron star that emits a beam of radiation. Even though the first pulsar was found by a radio telescope, other pulsars have been found which emit visible or other radiation. Fun fact: Jocelyn Bell Burnell and Antony Hewish, who discovered the first one, nicknamed the signal LGM-1 (Little-Green-Men), because, as they explain it themselves: ‘We did not really believe that we had picked up signals from another civilization, but obviously the idea had crossed our minds and we had no proof that it was an entirely natural radio emission.’. Unfortunately for all alien-lovers it turned out that pulsars are “just” interesting astronomical objects and not little green men.
- Alien radio channels: radio waves are the same waves that are used to get music to your radio. These man-made radio waves differ substantially from those emitted by natural phenomena since they show patterns that can’t be explained by phenomena in nature. This difference makes radio telescopes suited to look for intelligent extra-terrestrial life, which is done by the SETI (search for extra-terrestrial intelligence) project. If aliens transfer their music with radio signals, we should be able to detect it!
(Radio) Astronomy in the Netherlands
The first telescope was presumably built in 1608 in Middelburg by Zacharias Jansen and Hans Lipperhey. However, some say Galileo Galilei was the first to get a closer look at the stars in 1609. We will never know for sure. Nevertheless, the Netherlands have always played an important role in astronomy, with famous scientists like Jan Hendrik Oort (who gave his name to the Oort cloud) and Anton Pannekoek (after whom the UvA research institute for astronomy API was named).
Because the Netherlands has more cloudy than clear nights, the Dutch turned to radio astronomy. Our tiny country now features the three radio telescopes mentioned above.
Radio wave research at the UvA
The Netherlands has a longstanding tradition in radio telescopes. How is that nowadays, at the UvA? At the Anton Pannekoek institute (API) in Amsterdam, several research groups use Dutch radio telescopes to probe the night sky. The topics they study are:
- Radio pulsars: to test gravity theories among others.
- Accretion and jet formation: radio astronomy is used to determine the different stages of accretion.
- Radio transients: these short radio pulses are studied using LOFAR. API serves as a main centre of research into radio transients in the Netherlands.
- Cosmic-rays: radio telescopes like LOFAR and WSRT are also used to study the highly energetic processes in which cosmic-rays (whose particles are detectable on earth) are formed.
- Formation of massive stars: the birth places of these stars are obscured by dust clouds, which hide the visible light, but not the radio waves.
Do you want to know more about radio astronomy? Leave your questions/comments below or visit the public star gazing nights at API (Dutch).