Slashdot Mirror
Astronomers Detect Four Earth-Sized Planets Orbiting The Nearest Sun-Like Star (ucsc.edu)
Tim Stephens reports via The University of California in Santa Cruz: A new study by an international team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby sun-like stars. Two of them are super-Earths located in the habitable zone of the star, meaning they could support liquid surface water. The planets were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimeters per second. The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.
Fir those who wonder, 30 cm/s is roughly 10km/h, so about the speed of a jogger.
You are off by a factor of 10. It is about 1 km/h, so about the speed of a fast tortoise.
Our best bet to get a closer look any sooner is to use our Sun as a gravitational lens. It is still a challenge, because we would need to put a telescope at the correct side of the Sun at about 550 AU, far beyond the orbit of Pluto, but it is much closer to our technological reach than actual interstellar probes. NASA is thinking about this project: https://www.technologyreview.c...
It is the radial speed of the star b ing measured via doppler shift. It is the speed that the star is moving toward and away from Earth as a result of the orbiting planets' gravitational tug on the star.