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NASA’s Kepler Mission Discovers Its First Rocky Planet

By David Reneke

Dave Reneke brings news from the space and astronomy communities around the world.

NASA’s Kepler Mission Discovers Its First Rocky Planet

NASA’s Kepler mission has confirmed the discovery of its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it’s the smallest planet ever discovered outside our solar system. The discovery of this exoplanet is based on more than 8 months of data collected by the spacecraft from May 2009 to early January 2010.

“All of Kepler’s best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun,” said Natalie Batalha, a Kepler deputy science team leader at NASA’s Ames Research Centre in California.

The Kepler team resolved in 2010 to find these worlds, and their commitment is beginning to pay off. Kepler’s ultra-precise photometer measures the tiny decrease in a star’s brightness that occurs when a planet crosses in front of it.

Planetary sizes can be derived from these periodic dips in brightness, and the distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.

Kepler is the first NASA mission capable of finding Earth-sized planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet’s surface. “The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. Kepler-10 is one of the brighter stars being targeted and, as a result of this analysis, it’s one of the most well characterised planet-hosting stars in the universe.

The picture that emerges is of a rocky planet with a mass 4.6 times that of Earth and an average density of 8.8 g/cm3, which is similar to that of a heavy dumbbell.

Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come.

Are Solar Sails the Future of Space Travel?
In order to cross Earth’s oceans, humans learned to navigate its winds and currents. As we look to our future among the stars, solar sail technology gives us a similar opportunity – but this time we’ll be hitching a ride on sunlight.

The concept of solar sailing isn’t new. It dates back to the 16th century when astronomer Johannes Kepler noticed that comet tails always point away from the sun, implying that sunlight itself was pushing them around like cosmic windsocks.

Kepler suspected the presence of the solar breeze that modern spacecraft such as NASA’s NanoSail-D and Japan’s IKAROS sailed on. Scientists now know that sunlight is little more than a stream of photons, or tiny particles of light. When they bounce off a reflective surface, they push against that surface.

Solar sails are nothing more than highly reflective sheets of metal, or plastic coated with metal, that simply reflect sunlight. Mariner 10 successfully demonstrated the technology in 1974 when NASA used the probe’s solar arrays as an impromptu sail. Subsequent American, Russian, Indian and Japanese missions have further proven the technology’s feasibility.

It’s easy to imagine futuristic spacecraft traversing the solar system using solar sail technology to not only propel space probes but also to deliver supplies ahead of manned space missions – and even to nudge Earth-bound asteroids off course like a mini tug.

But sailing on the Sun’s solar wind certainly comes with its share of limitations. After all, a solar sail craft would have to start off very close to the sun to achieve its momentum, and the push would diminish the farther it travelled from the star. It would also take about 7000 years to reach the nearest star using current technology, and that’s a little too long to wait isn’t it?

Maybe one day we could generate our own solar wind with laser and particle beam technology. Future generations may develop a kind of “laser highway” to distant star systems by emitting a concentrated photon beam in the right direction. A solar sail vessel would merely enter the stream and hitch a ride, like a paper airplane drifting into the wind made by an electric fan.

With such a higher velocity, we may be able to send an expedition to the nearest star within a human lifetime, providing we use a large enough laser, a large enough sail and a light enough spacecraft. Captain Kirk would be impressed.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at