Our own sun might represent the best communications device around, if only we could harness its power, scientists say.
If the sun's gravity could be used to create a giant telescope, people could send and receive intensely magnified signals that could allow us to call an alien civilization, some researchers propose.
According to Einstein's general relativity, the sun's behemoth mass warps space-time around it, which actually bends light rays passing by like a giant lens. If a detector was placed at the right focal distance to collect the light, the resulting image would be extremely magnified.
The only catch is, the nearest focal point is about 550 times the distance between the Earth and the sun.
Nonetheless, eventually harnessing this power might enable Earth to view distant objects, communicate with interstellar probes, and even contact aliens, scientists say. The technique could be applied to optical light, or longer-wavelength light in the radio spectrum, for example.
Plus, an even stronger network could be created by placing relay spacecraft near other stars to form "radio bridges" across the great voids between stars that weaken and distort cosmic communiques.
"If we use the sun as a gravitational lens, then we can keep in touch with our own probes even at considerable interstellar distances," said Claudio Maccone, technical director of the Paris-based International Academy of Astronautics, and author of a new study on the mechanics of the proposed technique.
"This is key to exploring the neighborhood of our galaxy in the centuries to come," he said.
And alien civilizations might have already discovered this means of long-distance calling, Maccone said. If so, we might be able to intercept their messages.
The research was detailed in a recent issue of the journal Acta Astronautica.
Phoning deep space
To guide NASA rovers on Mars or to tell the Cassini spacecraft to snap pictures of Saturn, scientists rely on the U.S. space agency's Deep Space Network.
The network's antenna arrays pack enough power to keep astronomers in contact with the twin Voyager probes some 10 billion miles (16 billion kilometers) from Earth and flying through our solar system's edge.
As far as that might sound, it is small potatoes when compared with the span between the sun and its nearest stellar neighbors, the triple-star Alpha Centauri system, located 4.37 light-years, or around 26 trillion miles (41 trillion km) afield.
Communicating with aliens that far away, or even with our own spacecraft sent on distant missions, is a real issue.
Over these celestial distances, our electromagnetic communications signals grow feeble and garbled by ambient "space noise," such as the cosmic microwave background radiation, the relic heat signature from the birth of the universe 13.7 billion years ago.
This interference could scramble half of the information exchanged between us and intrepid, Alpha Centauri-bound explorers or probes in the future, according to Maccone's calculations.
So even if humankind went star-hopping, staying connected might be impossible, Maccone said.
"For interstellar missions, the number one problem we normally face is that we don't know how to propel a spacecraft that far," Maccone said, yet "communication is equally important."