Thursday, September 26, 2013

Sardinia got ears!

Finally the Sardinia Radio Telescope (SRT) is ready to start its scientific mission, the inaugural ceremony will take place on September 30th (next Monday) in the presence of the Italian Minister of Education, University and Research, Prof. Carrozza.
The Sardinian Radio Telescope based in San Basilio

SRT is located in Sardinia near San Basilio, a small village about 35km from Cagliari, my hometown. SRT is the largest radiotelescope in Italy (diameter: 64 meters) and one of the most advanced in the world.

SRT will join the first Very Large Baseline Interferometer (VLBI) network in Italy, meaning that these 3 facilities will operate as a huge interferometer whose effective dimension is comparable to the size of our country! This allows to reach angular resolutions which would be simply impossible with a single instrument. As one of the most advanced radiotelescopes worldwide, SRT will also contribute as a node of the European VLBI Network.

But so, what is a radiotelescope
It's essentially an antenna that is sensitive to radio signals. The latter are a portion of the electromagnetic spectrum, similarly to microwaves, ultraviolet radiation and...even normal light. In this sense, their are close cousins of normal telescopes.

Indeed, standard (optical) telescopes are designed to observe visible light and they are usually located far from urbanized areas in order to minimize light pollution (modern telescopes are located at high altitude -like the European Southern Observatory located in Chile- or even launched in orbit around the Earth -like the famous Hubble Telescope- in order to avoid attenuation and distortion by Earth's atmosphere).

Usually radiotelescopes are big parabolic antennas similar to those used for satellite communications, but much bigger in size. They became popular to the general audience after the movie "Contact"(starring Jodie Foster as a brilliant radioastronomer). Unfortunately radioastronomy in the movie soon turns out to be an excuse to rave about spacetime travels and other science-fiction inventions, but it does show some nice scene like the following:

A scene taken from the movie "Contact", starring Jodie Foster and several radiotelescopes

Why are radiotelescopes important?

Think about the way we all perceive reality through our 5 senses. We can observe, touch, hear (and sometimes sniff and taste) and this is what produces our own sensorial perception of surrounding objects. If we were missing one of these sense, our perception of reality would be limited and deceptive.

The same happens in astronomy. Among other sciences, astronomy is one of a kind because there is no way to interact with the objects we want to study, we can only "observe" them. But fortunately we can do so in a variety of ways, pretty much a different way for each sector of the electromagnetic spectrum. Astronomers can use optical, X-ray, infrared, gamma-ray telescopes as well as radiotelescopes to capture as much information as possible from stars, galaxies and other objects.

One of the major limitations of optical astronomy is that normal light can be diffused/attenuated/scattered during its cosmic travel from the source to us. On the other hand, sources which are optically hidden due to attenuation can also be strong emitters of radio waves, which in some situation can travel almost unperturbed and reach those huge parabolic antennas as the one of the SRT.

To give you an idea, here are some snapshots of our Universe in different portions of the electromagnetic spectrum:

Taken from here
This picture (and especially the last microwave image) deserves at least another post, but it shows how the same "object" looks different at different wavelengths. The image corresponding to the neutral hydrogen is taken with radiotelescopes, because hydrogen emits a very characteristic radio signal whose wavelength is 21 cm. Hydrogen is also the most common element in the Universe and this gives an idea of the importance of radioastronomy.

PS: I now realize that the title of this post is misleading because, strictly speaking, telescopes and radiotelescopes allow us to have many different "eyes", all sensitive to different types of "light". This is not the complete story and, soon enough, we will be also able to "hear" the sound of the Universe. The instruments that will provide us with this new "sense" are gravitational-wave detectors, but this is material for another post....

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