The mystery object in Ophiuchus seen last month. It looked like a 3rd magnitude star (one level fainter than the Big Dipper stars) that “didn’t belong” there. Photo: Bob King
One night last month while setting up the telescope for a night of observing I noticed a “new” star in the southern constellation Ophiuchus. I first thought it was a satellite but it appeared stationary and didn’t fade away. Hmmmm. Could this be a new nova? It was in the Milky Way band where most novae (explosive outbursts of stars) are discovered. Just in case the object proved to be something interesting, I fired off a few photos.
Close up view of Ophiuchus and Galaxy 11. In 30 seconds time, the satellite barely moved while the stars show obvious trails from Earth’s rotation. Photo: Bob King
The longer the light remained the more excited I became until I noticed that it was moving very slowly to the east. Well, there went my novae hypothesis. The mystery object soon began to fade; five minutes later was barely visible to the naked eye.
Feeling slightly deflated, I realized I’d been watched a long, slow flare from a satellite. The sun, satellite and my spot on the hill were lined up just right for sunlight to reflect off an antenna and back to my eye.
Later that night I fished around and discovered my nova was Galaxy 11, an active communications satellite serving both the U.S. and Brazil.
Galaxy 11 is a communications satellite in geosynchronous orbit around Earth.
Galaxy 11 relays TV programming like the Celebrity Shopping Network and National Geographic to widely separated points on Earth.
Most of the satellites we see like the space station are in low-Earth orbit or LEO. Being relatively close to the planet they circle around it faster than the Earth rotates. That’s why we see the 240-mile-high space station cross the sky in only five minutes. Every 90 minutes it completes another orbit.
A satellite in geostationary orbit (shown above) remains in exactly one spot in the sky. Credit: Francisco Esquembre
The farther a satellite is from Earth, the slower it moves across the sky. If you ever see one slowly creeping its way through the heavens, you know it’s much higher than the space station located some 240 miles up in LEO.
It’s possible to send a satellite far enough away – 22,236 miles to be exact – so that it appears to stay fixed or nearly so in just one place in the sky, hovering over the planet like an all-seeing eye.
Birds at this towering altitude are said to be in geosynchronous orbit. You may have also heard of geostationary satellites. Geostationary is a more specific term and refers to a satellite in a geosynchronous circular orbit directly over the equator. These remain in exactly the same spot in the sky; geosynchronous satellites are in slightly inclined orbits and remain in the same small area of sky.
Arthur c. Clarke at his home in Colombo, Sri Lanka in 2005
It was the late science fiction writer Arthur C. Clarke who in 1945 first suggested that a global communications network would be possible using three equally spaced geostationary satellites orbiting above Earth’s equator. NASA finally tested Clarke’s idea in 1963, and lo and behold in 2012 we can hardly live without them.
Geosynchronous satellites are essential for TV broadcasting, satellite radio, weather forecasting and global communications.
Most geosynchronous satellites are faint because they’re far away and require binoculars or a telescope to see. One in while however they flare in sunlight like Galaxy 11 and become easily visible with the naked eye.
Illustration showing space debris and active satellites orbiting Earth. Geosynchronous satellites responsible for relaying communications around the world define the distinct outer ring. The dense inner circle are satellites in low Earth orbit. Credit: NASA
It’s a real treat to bump into a geosynchronous satellite in the telescope. They hang out near the celestial equator in the sky. Once found, a “geosync” stays put in the field of view while all the other stars drift by, carried along by Earth’s rotation. Even though I didn’t discover a nova that May night, I’m remain in admiration of Clarke’s genius and mankind’s ingenuity.