As Carl Sagan once said, “Heaven is calling us. If we don’t self-destruct we will one day venture to the stars. “And our first emissaries to the stars will be robotic probes. These interstellar probes will be largely autonomous, but we will want to communicate with them. At least we want them to phone home and tell us what they discovered. The stars are far away, so the probes will need to make a long distance call.
We are currently communicating with space probes across the solar system via the Deep Space Network (DSN). This is a collection of antenna stations around the world. Each station has a large 70-meter bowl and several smaller dishes. Such large radio dishes are necessary because the signals from a space probe are rather weak and weaken with increasing distance.
When we send probes to other stars, we need an interstellar communication network. Maybe a galaxy-wide internet. But we still don’t know how to do one. Although we can transmit strong radio signals into space, the strength of these signals becomes weaker over star distances. Most of what we transmit could only be recognized after a few light years due to our current technology. Various solutions have been proposed, such as the use of focused laser light. However, a new study looks at using gravitational lenses to get the job done.
Magnification of a radio signal with gravitational lenses. Photo credit: Claudio Maccone
Radio signals are a good choice for interstellar distances because they can carry a good amount of data with relatively little power. That is why we use radio for interplanetary communication. The disadvantage is that radio waves are difficult to focus in one direction due to their long wavelength. We can point a narrow beam of laser light at a particular star, but we cannot just focus a narrow beam of radio. And our radio signals need to be focused to transmit light years.
This new study examines how radio signals from the sun or nearby stars can be focused. Since stars warp space around them by gravity, light passing near a star can be viewed through gravitational lenses. This effect can be used to focus radio light, much like a glass lens focuses optical light. In this new article, Claudio Maccone did some basic calculations of the bandwidth that can be achieved between the Sun and nearby stars like Alpha Centauri and Barnard’s Star. The data rate could be in the order of magnitude of kilobits / second, which is in the order of magnitude of the old dial-up days of the Internet. Not great by modern standards, but certainly enough to transfer useful images and data from another planet.
Reference: Maccone, Claudio. “Galactic Internet possible through star gravity lenses.” Acta Astronautica 82.2 (2013): 246-246; 250.
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