[LINK] Three cautionary Kepler-452b links

[rfmcdonald]

Centauri Dreams featured Paul Gilster's post "Earth 2.0: Still Looking".

Kepler-452b, about 1400 light years from us, has now been confirmed as a planet, and it’s an interesting world, one that orbits a star much like the Sun, being about 5 percent more massive and 10 percent brighter. The planet itself is about 5 times the mass of the Earth, with a radius 50 to 60 percent larger. Moreover, Kepler-452b orbits only 5 percent farther from its parent star than Earth orbits the Sun, with a 385-day year. Jon Jenkins (NASA Ames) is lead author on the paper on this work. He pointed out at the NASA news briefing today that gravity on this world would be about 50 percent larger than that of Earth, on a world with a thicker atmosphere and a larger degree of cloud cover. The star is also older than our Sun[.]

This is a planet that has been in its star’s habitable zone for longer than the age of the Earth, ample time, as Jenkins noted, for life to begin. Although the size of the world — intermediate between Earth and Neptune — makes it too large to be a true Earth analogue, Jenkins believes that it has a “better than even chance of being rocky.” Thus we could be looking at a world that models changes our planet will be making in the remote future.

Imageo notes that the nature of the world is still open to debate.

It’s 6 billion years old, 1.5 billion more than Earth. It’s also about 60 percent larger in diameter, and its mass is may be five times that of Earth, give or take.

So, about that caveat: Astronomers can’t yet say what Kepler-452b is made of. For it truly to be just like Earth, it would have to be made of rock. And that’s why we still do not know for sure, despite today’s announcement, whether there really are other Earth-like planets circling stars like our Sun within a region where it’s not too hot or too cold for liquid water to exist on the surface. Liquid water is thought to be a requirement for life.

But Jon Jenkins of NASA’s Ames Research Center, home of the Kepler project, told the New York Times that there’s a 50 percent to 62 percent chance of Kepler-452b being rocky.

Or as NASA puts it, “previous research suggests that planets the size of Kepler-452b have a good chance of being rocky.”

The Dragon's Gaze notes that this world is one of twelve candidates.

Scientists analyzing four years of data from NASA's Kepler mission have released a new catalog of exoplanet candidates.

The catalog adds more than 500 new possible planets to the 4,175 already found by the famed space-based telescope.

"This catalog contains our first analysis of all Kepler data, as well as an automated assessment of these results," says SETI Institute scientist Jeffrey Coughlin who led the catalog effort. "Improved analysis will allow astronomers to better determine the number of small, cool planets that are the best candidates for hosting life."

The Kepler space telescope identifies possible planets by observing periodic dips in the brightness of stars. However, confirmation of their true planetary status requires observations by other instruments, typically looking for slight shifts in the motion of the host suns. Historically, the overwhelming majority of Kepler's discoveries have turned out to be actual planets.

The new catalog includes 12 candidates that are less than twice Earth's diameter, orbiting in the so-called habitable zone of their star. This zone is the range of distances at which the energy flux from the star would permit liquid water to exist on the planet's surface.