Exciting Exoplanet News from AAS: How Rocky Worlds are Made; Oceans on Super-Earths

Tuesday, January 6, 2015

Exciting Exoplanet News from AAS: How Rocky Worlds are Made; Oceans on Super-Earths

Exciting Exoplanet News from AAS: How Rocky Worlds are Made; Oceans on Super-Earths:

This artist's depiction shows a gas giant planet rising over the horizon of an alien waterworld. New research shows that oceans on super-Earths, once established, can last for billions of years. David A. Aguilar (CfA)

This artist’s depiction shows a gas giant planet rising over the horizon of an alien waterworld. Image Credit: David A. Aguilar (CfA)

Astronomers from around the world gathered in Seattle today for the 225^th meeting of the American Astronomical Society. Although it’s just past noon on the West Coast, the discoveries are already beginning to unfurl. Here are some of the highlights from this morning’s exoplanet session. And the keyword seems to be “water.”

A Recipe for Earth-like Planets?

There’s no doubt that the term “Earth-like” is a bit of a misnomer. It requires only that a planet is both Earth-size and circles its host star within the habitable zone. It says nothing about the composition of that planet.

Now, Courtney Dressing from the Harvard-Smithsonian Center for Astrophysics (CfA) and her colleagues have taken detailed observations of small exoplanets in order to nail down a digestible recipe.

Dressing and her colleagues focused on only a handful of exoplanets because they had to take painstakingly long, but accurate measurements. They used the HARPS-N instrument on the 3.6-meter Telescope in the Canary Islands to precisely determine the planets’ densities.

Most recently the team targeted Kepler-93b, a planet 1.5 times the size of Earth and 4.01 times the mass of Earth. Kepler 93-b, as well as all other exoplanets with sizes less than 1.6 times Earth’s size and six times Earth’s mass, show a tight relationship between size and mass. In other words, when plotted by size vs. mass, they fit onto the same line as Venus and the Earth, suggesting they’re all rocky planets.

Larger and more massive exoplanets do not follow the same trend. Nature simply doesn’t want to make rocky planets that are more massive than six Earth masses. Instead, their densities are significantly lower, meaning their recipes include a large fraction of water or hydrogen and helium.

“Today if you’re not too worn out from all the holiday baking, when you get back home, I’d encourage you to check out this new recipe for rocky planets” said Dressing at the AAS press conference. The playful recipe requires one cup of magnesium, one cup of silicon, two cups of iron, two cups of oxygen, ½ teaspoon aluminum, ½ teaspoon nickel, ½ teaspoon calcium, and ¼ teaspoon sulfur.

Now you have to be patient. “Bake this for a couple million years until you start to see a thin, light brown crust form on the surface of the planet,” said Dressing. Then season it with a dash of water. “If you check back in a couple million years, maybe you’ll see some intelligent life on your planet.”

Super-Earths Have Long Lasting Oceans

Another team of astronomers took a closer look at that dash of water. There’s no doubt that life, as we know it, needs liquid water. The Earth’s oceans cover about 70 percent of the surface and have for nearly the entire history of our world. So the next logical step suggests that for life to develop on other planets, those planets would also need oceans.

Water, however, isn’t just on Earth’s surface. Studies have shown that Earth’s mantle holds several oceans’ worth of water that was dragged underground. If water weren’t able to return to the surface via volcanism, it would disappear entirely.

Laura Schaefer, also from the CfA, used computer simulations to see if this so-called deep water cycle could take place on Earth-like planets and super-Earths.

She found that small Earth-like planets outgas their water quickly, while larger super-Earths form their oceans later on. The sweet spot seems to be for planets between two and four times the mass of Earth, which are even better at establishing and maintaining oceans than our Earth. Once started, these oceans could persist for at least 10 billion years.

“If you want to look for life, you should look at older super-Earths,” said Schaefer. It’s a statement that applies to both realms of research presented today.

The AAS will continue throughout the week. So stay tuned because Universe Today will continue bringing you the highlights.

About Shannon Hall

Shannon Hall is a freelance science journalist. She holds two B.A.'s from Whitman College in physics-astronomy and philosophy, and an M.S. in astronomy from the University of Wyoming. Currently, she is working toward a second M.S. from NYU's Science, Health and Environmental Reporting program. You can follow her on Twitter @ShannonWHall.

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The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

UFO SIGHTINGS PHOTO PHOTOGRAPHY

The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe

Photos of Nature | Nature Photography What is The Universe

Tuesday, January 6, 2015