Spitzer sniffs out alien super-Earth

Artist impression of the steamy super-Earth 55 Cancri e compared to our own planet. Credit: NASA

Astronomers have spied the light of big, Jupiter-sized alien planets but never one as small as 55 Cancri e,  a “super-Earth” orbiting the star 55 Cancri 41 light years away in Cancer the Crab. Super-Earths are extrasolar planets more massive than Earth that bridge the gap between little planets like our own and larger ones like Neptune and Uranus.

55 Cancri e is twice as big and 8 times as massive as Earth. It’s believed to have a rocky core surrounded by an ocean that’s simultaneously liquid and vapor and topped with a layer of steam. Orbiting in just 18 hours, the planet is tidally locked in its host star’s gravitational embrace. One hemisphere faces the chill of outer space while the other roasts in starlight.

With a surface temperature of 3,140 degrees Fahrenheit on the sun-facing side, “e” will probably never be an oasis for life.

Extrasolar planet 55 Cancri e is too faint to see in the glare of its host star, but using the Spitzer Space Telescope, which picks up the planet's intense heat, astronomers were able to measure its light and temperature. Credit: NASA/JPL-CalTech

The Spitzer Space Telescope, built to observe in the infrared or heat-radiating end of the spectrum, picked up the planet’s light signature because it blazes like a bonfire. Humans are also warm creatures. If our eyes were adapted to see infrared light, we’d easily spot one another at night  from blocks away. 55 Cancri e’s infrared outpouring makes it stand out from the glare of its host star. In visible light, it’s invisible.

The plot shows how the infrared light from the 55 Cancri system changed as the planet passed behind its star. When the planet disappeared, the total light dropped, and then increased back to normal levels as the planet circled back into view. Credit: NASA

Spitzer can’t actually see the planet as a separate point of light next to the star. The two are much too close for that. Instead it measures the dip in brightness of the entire system as “e” passes behind the star during half of its orbit. Based on how the system’s light changes, astronomers can determine the planet’s temperature, apparent brightness and sometimes even its composition.

55 Cancri e is very dark and very hot. “It could be very similar to Neptune, if you pulled Neptune in toward our sun and watched its atmosphere boil away,” said Michaël Gillon of Université de Liège in Belgium, principal investigator of the research.

The “e’ by the way tells us this is the 5th planet discovered around 55 Cancri. Extrasolar planets are named after the letters of the alphabet starting with “a”.

Globular cluster M55 photographed in infrared light by the 4.1-meter (161-inch) Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal Observatory in Chile. The time exposure also recorded many background galaxies - the easiest to see is at upper right at 2 o'clock. See closeup below. Credit: ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit

Someday we’ll find planets inside the massive balls of stars called globular clusters that dot the outskirts of the Milky Way galaxy. Globulars contains hundreds of thousands up to 10 million stars. Although photographs show the clusters as flat, try to picture them as they really are – great spheres of stars all in motion around the center like a swarm of bees. Think of all those potential planets!

This cropped version of the photo above shows the background galaxy more clearly. Click the image for a large version where you can explore for more galaxies. Credit: ESO

The European Southern Observatory (ESO) released pictures today of one of the largest, richest globular clusters, M55 in Sagittarius the Archer. At 2/3 the diameter of the full moon, this gemmy bunch is one of the largest in the sky and easy to resolve into stars in a 6″-8″ inch telescope.

M55 packs approximately 100,000 stars into a sphere about 100 light years across or 25 times the distance between the sun and Alpha Centauri, the nearest star system. To learn more about M55 and globular clusters in general, click HERE.

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