Numerous rocky, Earth-like worlds have been discovered by transit surveys such as the Kepler mission. For those familiar with the transit of Venus last year, exoplanet transits are the same idea – an exoplanet crosses the face of its parent star as perceived by observers on Earth. By comparing the amount of starlight the transiting planet blocks and the total starlight emitted by the host star, astronomers can determine the radius of a transiting planet.
Recent surveys have hinted at the existence of exoplanets with rocky surfaces, making them similar to our own “terrestrial” planets Mercury, Venus, Earth and Mars. However, a number of the exoplanets thought to have rocky surfaces appear to not have any significant atmospheres. One such exoplanet is Corot-7b, which orbits very close to its parent star. Exoplanet 55 Cancri e, estimated to have roughly twice Earth’s radius and roughly eight times Earth’s mass, also may be a rocky planet, and perhaps even made of diamond.
Read my full article on how researchers hope to better understand the surfaces of distant planets at: http://www.astrobio.net/exclusive/5493/investigating-exoplanet-surfaces
Using publicly available data from NASA’s Kepler space telescope, astronomers at the Harvard-Smithsonian Center for Astrophysics estimate that six percent of red dwarf stars in the galaxy have Earth-size planets in the “habitable zone,” the range of distances from a star where the surface temperature of an orbiting planet might be suitable for liquid water.
The majority of the sun’s closest stellar neighbors are red dwarfs. Researchers now believe that an Earth-size planet with a moderate temperature may be just 13 light-years away. “We don’t know if life could exist on a planet orbiting a red dwarf, but the findings pique my curiosity and leave me wondering if the cosmic cradles of life are more diverse than we humans have imagined,” said Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center in Moffett Field, Calif.
Detecting water on the surface of exoplanets is becoming a high priority for researchers, as surface water is considered a requirement for habitability. New research examines whether or not the “glint” of light from a planet can be interpreted as evidence for surface oceans.
Given the plethora of confirmed exoplanets, many researchers have turned their attention to studying these strange new worlds in greater detail. With several exoplanets thought to orbit in the “habitable zone” of their host star where liquid water might be stable, different methods of detecting surface water are under development. One such proposed method of detecting water oceans on an exoplanet is via specular reﬂection, also known as “glint”. If you’ve seen a bright reflection of sunlight on a lake or ocean here on Earth, you’ve seen an example of the glint effect.
Scientists posit that surface oceans of exoplanets would affect the planet’s apparent reflectivity, also known as albedo. This increase of albedo should be detectable during the crescent phase of a planet.
Check out the full Astrobiology Magazine article at: http://www.astrobio.net/exclusive/4882/can-astronomers-detect-exoplanet-oceans
Astronomers use the term “metallicity” in reference to elements heavier than hydrogen and helium, such as oxygen, silicon, and iron. In the “core accretion” model of planetary formation, a rocky core gradually forms when dust grains that make up the disk of material that surrounds a young star bang into each other to create small rocks known as “planetesimals”. Citing this model, Johnson and Li stress that heavier elements are necessary to form the dust grains and planetesimals which build planetary cores.
Additionally, evidence suggests that the circumstellar disks of dust that surround young stars don’t survive as long when the stars have lower metallicities. The most likely reason for this shorter lifespan is that the light from the star causes clouds of dust to evaporate.
You can read my full Astrobiology Magazine article at: http://www.astrobio.net/exclusive/4681/when-stellar-metallicity-sparks-planet-formation