This diagram shows the approximate relative sizes of the terrestrial planets, from left to right: Mercury, Venus, Earth and Mars. Distances are not to scale. A terrestrial planet is a planet that is primarily composed of silicate rocks. The term is derived from the Latin word for Earth, “Terra”, so an alternate definition would be that these are planets which are, in some notable fashion, “Earth-like”. Terrestrial planets are substantially different from gas giants, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. Terrestrial planets have canyons, craters, mountains, volcanoes and secondary atmospheres.
This is a real image taken by the robotic spacecraft Cassini of Saturn eclipsing the sun (via).
Amazing. There is a little blue dot on the left side of the image just above the bright main rings. That is Earth, approximately a billion miles away.
Not psychology related, just an incredible image. Click for high resolution to see Earth.
Super Earth Found in Habitable Zone
by Govert Schilling
The Milky Way abounds with low-mass planets, including small, rocky ones such as Earth. That’s the main conclusion of a team of European astronomers, based on their latest haul of extrasolar planets. The new discoveries—55 new planets, including 19 “super-Earths”—were presented here today at the Extreme Solar Systems II conference by team leader Michel Mayor of the University of Geneva in Switzerland. “We find that 40% of all Sun-like stars are accompanied by at least one planet smaller than Saturn,” he says. The number of Earth-like planets is expected to be even higher.
The new planets were found with HARPS (High Accuracy Radial velocity Planet Searcher), an extremely sensitive instrument used to analyze starlight, mounted on the 3.6-meter telescope of the European Southern Observatory (ESO) at Cerro La Silla in northern Chile. HARPS detects the minute periodic wobbles of stars, caused by the gravity of orbiting planets. So far, HARPS has discovered 155 exoplanets, including two-thirds of all planets less massive than Neptune.
Of the 19 newly found super-Earths (exoplanets between a few and 10 times the mass of Earth), the most intriguing is HD 85512b, which weighs in at only 3.6 Earth masses. Its orbit lies in the habitable zone of its parent star, which means temperatures are just right for liquid water to exist on its surface, says Lisa Kaltenegger of the Max Planck Institute for Astronomy in Heidelberg, Germany. “We’re entering an incredibly exciting period in history.”…
(read more: Science NOW) (image: ESO)