The planets of the Kepler-30 system, seen here in an artist's impression, all transit the same starspot, indicating that they lie in the same geometric plane. Sanchis-Ojeda et al.
- Planets circling Kepler-30 transit the same sunspot, indicating they lie in the same geometric plane.
- The finding suggests a common birth in a rotating disk of gas, much like the suspected origins of our solar system.
- Kepler-30's brood may also include moonlets, asteroids and other bodies circling in the same plane.
When NASA's Kepler space telescope started finding planets at odd angles to their parent stars, scientists wondered if our solar system's tidy geometry, with the planets neatly orbiting around the sun's equator, was an exception to the rule.
That idea can be laid to rest thanks to an innovative use of the Kepler data which aligned three planets circling the sun-like star Kepler-30 with a giant spot on the star's surface.
The study showed the trio of planets orbiting within one degree, relative to each other and relative to the star's equator. That finding is an indication that Kepler-30, like our own solar system, formed from a rotating disk of gas.
"The planets themselves are not all that remarkable -- two giant Jupiters and one super-Earth -- but what is remarkable is that they aligned so perfectly," astronomer Drake Deming, with the University of Maryland, told Discovery News.
"The dynamics of the system are important for the possible development of life," he added.
The alignment of the Kepler-30 brood is the most precise found yet.
The Kepler telescope is studying about 150,000 sun-like stars for signs of Earth-like planets. Multi-planet systems would have to be somewhat aligned to fall into the telescope's narrow and deep field of view.
Kepler's targets are all hundreds to thousands of light years away. One light-year is about 5.9 trillion miles.
Future missions to probe stars closer to Earth most likely would need a wider-angle view, so using starspots as reference points could be a valuable tool for homing in on systems geometrically similar to ours.
"By chance, and because we have good data on our hands, we came up with the idea to measure obliquity (slant) with spots," lead researcher Roberto Sanchis-Ojeda, with the Massachusetts Institute of Technology, told Discovery News.
The research appears in this week's Nature.