Silent as the night: Why radio astronomy doesn’t listen to the sky

Within the 1997 film “Contact,” Ellie Arroway is a younger radio astronomer performed by Jodie Foster. Ellie’s on a mission to find alien life, and in a single well-known scene filmed on the Very Massive Array, she sits on the fringe of the observatory, listening to the radio sounds of the sky with antenna dishes within the background.

It is a fantastic cinematic second highlighting Ellie’s lonely seek for fact and has change into so iconic that many guests to the VLA take “that shot” of themselves carrying headphones in entrance of a radio dish. However as superbly poetic because the scene is, it’s Hollywood magic, not laborious science. The radio signals from Ellie’s headphones and laptop would intervene with the observatory’s delicate tools and radio astronomers do not take heed to the sky.

The concept that radio astronomers take heed to celestial objects is probably the most important false impression in radio astronomy. And to some extent it is comprehensible. Folks take heed to the radio on a regular basis, so certainly radio astronomers should do the identical. However the sounds we hear on the radio aren’t the sounds of radio itself. They’re transformed from electrical indicators. Sound waves require a medium equivalent to air to journey by, and since space is actually a vacuum, sounds cannot journey by space. If astronomers did take heed to the sky, all they’d hear is silence.

Radio is a type of gentle. It is similar to seen gentle, however with a for much longer wavelength. Whereas seen gentle has a wavelength on the dimensions of atoms, radio gentle has wavelengths starting from concerning the thickness of a pencil result in greater than the size of a bus.

As a result of radio wavelengths are on the human scale, the know-how of radio astronomy is commonly very totally different from that of optical astronomy. There are broad similarities. Each optical and radio astronomy use reflective surfaces to focus gentle onto a detector or receiver, which then converts the sunshine right into a digital sign. Astronomers can then use this digital sign to create astronomical photographs. However as a result of radio wavelengths are a lot longer than visible wavelengths, we now have to attain this feat in several methods.

One key issue is the scale of the reflector. Typically, the bigger your reflector or mirror, the extra gentle you possibly can focus and the sharper and brighter your picture. Because of this the perfect optical telescopes have mirrors a number of meters in diameter. However the dimension of your reflector should scale to that of your wavelength. Since radio waves are 1000’s of occasions longer than seen waves, a radio telescope mirror would have to be bigger than Manhattan. That is not one thing we are able to construct, so as a substitute, we create arrays of smaller dishes. Every antenna dish acts like a bit of a bigger mirror. Astronomers can then simulate a city-wide dish by combining information from the array of smaller dishes.

One other issue is that radio gentle is commonly a lot fainter than visible light, and there are numerous issues that create radio gentle. Which means that radio telescopes have to be protected against on a regular basis objects equivalent to cell telephones and laptop tools that emit radio gentle. The antenna receivers should even be extraordinarily chilly. Objects at room temperature emit a number of faint radio gentle which might have an effect on the accuracy of observational information, so the receivers and different electronics of a radio telescope have to be supercooled to transform radio gentle right into a digital sign.

In fact, as soon as astronomers have their information, they will at all times convert that information into sound. That is most famously performed with pulsars, the place the electrical bursts of power from a neutron star are transformed to audible pops. Astronomers have additionally transformed phenomena such because the turbulent aurora of Jupiter, or the wail of a distant nebula. These sounds can provide us an emotional connection to the cosmos, however similar to the scene from “Contact,” they’re merely a poetic interpretation of the radio gentle we seize.