News from Space: First Earth-Sized Exoplanet Found!

kepler78bFor the past three and a half years, the Kepler space telescope has been hurtling through space and searching the Milky Way for signs of of other planets orbiting distant stars. In that time, Kepler has identified many Earth-like exoplanets, many of which reside within our own stellar neighborhood. However, it has found only one planet in recent months that is Earth-sized.

That planet is known as Kepler-78b, the existence of of which was recently verified by NASA scientists at Cape Canaveral. Of all the planets discovered beyond our Solar System, this one is both rocky in composition and weighs in at roughly 1.2 times Earth’s mass. Beyond that, however, the similarities between this planet and our own end.

kepler78b2In addition to having an orbital period of 8.5 hours, the planet also rotates around its parent star at a distance of about 1.5 million kilometers (approx. 93205 miles). Basically, this means that Kepler-78b is thirty to forty-five times closer to its Sun than Mercury is to ours, and experiences a full year in under nine days. This makes Kepler 78b an extremely hostile environment, unsuitable for life as we know it.

Andrew Howard, of the University of Hawaii at Manoa’s Institute for Astronomy and the lead author on one of two papers published in Nature magazine about the discovery of the new planet, said in recent webcast:

We’ve been hearing about the sungrazing Comet ISON that will go very close to the Sun next month. Comet ISON will approach the Sun about the same distance that Kepler-78b orbits its star, so this planet spends its entire life as a sungrazer.

Kepler78b1A handful of planets the size or mass of Earth have been discovered, but Kepler-78b is the first to have both a measured mass and size. At 1.2 times the size of Earth with a diameter of 14,800 km (9,200 miles), astronomers say it has a density similar to Earth’s, which suggests an Earth-like composition of iron and rock. Its star is slightly smaller and less massive than the sun and is located about 400 light-years from Earth in the constellation Cygnus.

Verification of the planet’s existence and characteristics was made by two independent research teams that used ground-based telescopes for follow-up observations. The team led by Howard used the W. M. Keck Observatory atop Mauna Kea in Hawaii. The other team led by Francesco Pepe from the University of Geneva, Switzerland, did their ground-based work at the Roque de los Muchachos Observatory on La Palma in the Canary Islands.

exoplanet_hotAnd while the discovery is exciting, the close proximity of Kepler-78b to its star poses a challenge to theorists. According to current theories of planet formation, it couldn’t have formed so close to its star, nor could it have moved there. Given that its star would have surely been larger when the system was in formation, Kepler-78b’s orbit would have put in inside the swollen star. Hence, the planet’s existence is an enigma.

To make matters worse, Kepler-78b is a doomed world. Gravitational tides will continue to pull Kepler-78b even closer to its star, and eventually it will move so close that the star’s gravity will rip the world apart. Theorists predict that the planet will vanish within three billion years. And while this may sounds like an eternity to us, in astronomical terms it represents a life cut short.


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