Tag Archives: Elizabeth Tasker

The search for Earth 2.0

Astronomers have to date discovered more than 3,700 exoplanets—planets in orbit around stars other than our Sun. With each discovery, someone wants to know if the newly discovered planet is like Earth.

Elizabeth Tasker

Elizabeth Tasker at Astronomy on Tap Seattle.

Elizabeth Tasker thinks that’s not a very good question. Tasker, associate professor at the Japan Aerospace Exploration Agency, Institute of Space and Aeronautical Science and author of The Planet Factory: Exoplanets and the Search for a Second Earth (Bloomsbury Sigma, 2017) gave a talk at the most recent edition of Astronomy on Tap Seattle. She said that some of the exoplanets confirmed so far have at least a little resemblance to Earth.

“Roughly one third of those are approximately Earth-sized, by which I mean their physical radius is less than twice ours,” Tasker said. News media often wish to leap from that to describing a planet as Earth-LIKE, but Tasker said we don’t have nearly enough information to make that sort of call. Our current methods of detecting an exoplanet can give us either its radius or its minimum mass, and a pretty good read of its distance from its host star.

“The problem is neither of those directly relates to what’s going on on the surface,” Tasker noted. Part of the challenge is what Tasker feels is the somewhat oversimplified notion of the “habitable zone” around a star, a band of distance in which liquid water—a key to life as we know it—could exist on a planet’s surface.

“Like all real-estate contracts, there is small print,” Tasker said. “Just because you’re inside the habitable zone doesn’t mean you’re an Earth-like planet. Indeed, of all the planets we’ve found in the habitable zone around their stars, there are five times as many planets that are very likely to be gas giants like Jupiter than have any kind of solid surface.”

Another misleading metric that has been used is something called the “Earth similarity index.” This method compared exoplanets to Earth on the basis of properties such as density, radius, escape velocity, and surface temperature.

“None of these four conditions actually measure surface conditions at all,” Tasker said, pointing out that the index didn’t take into account such features as plate tectonics, a planet’s seasons, it’s magnetic fields, greenhouse gases, or existence of water. We can’t observe any of those things about exoplanets yet. As an example of the flaws of the index, Venus came out at 0.9, pretty similar to Earth, which is at 1.0 on the zero-to-one scale. While Venus is about the size of Earth and is around the inner edge of the Sun’s habitable zone, its surface temperature could melt lead. Not very Earth-like, or habitable. It’s one of the reasons that the index is seldom used these days. So we don’t have much of a clue about conditions on any of the known exoplanets.

“Our next generation of telescopes is going to change that,” Tasker said. She noted that NASA’s James Webb Space Telescope is scheduled to launch next year, the ESA’s Ariel in 2026, and the UK’s Twinkle in the next year or so.

“All of these are aiming at looking at atmospheres, and these may be able to tell us what is going on on the surface, and may even give us the first sniff of life on another planet,” Tasker said. “Maybe then we’ll be able to talk seriously about Earth 2.0.”

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Calendar: UW colloquium and AOT Seattle this week

A couple of interesting talks and no less than five club meetings fill the astronomy event calendar for this week.

UW Astronomy Colloquium

Juno at Jupiter

Juno at Jupiter. Image: NASA

Come learn about what the Juno mission is accomplishing at Jupiter. Sam Gulkis of the NASA Jet Propulsion Laboratory, one of the co-investigators for Juno, will speak at the University of Washington astronomy colloquium at 4 p.m. Thursday, February 15 in the Physics/Astronomy Auditorium on the UW campus in Seattle. Often the colloquia are a little heavy for the non-scientist audience, but this one sounds approachable. Gulkis will discuss how Juno peeks under Jupiter’s clouds using microwaves and other techniques, and he’ll fill us in on some of the mission’s early findings.

Astronomy on Tap Seattle

AOT Feb 2018Astronomy on Tap Seattle has an unusual Friday gathering this month, with two talks, astronomy trivia, and great prizes on the docket for 7 p.m. February 16 at Peddler Brewing Company in Ballard. The topic for the evening will be Cosmic Explorers. Dr. Jen Sobeck, a senior research scientist in the UW Department of Astronomy, will talk about the Harvard Computers—the women who mapped the sky! Dr. Elizabeth Tasker, author of The Planet Factory: Exoplanets and the Search for a Second Earth (Bloomsbury Sigma, 2017) will talk about “Earth 2.0” and the search for a habitable world. (By the way, if you buy the book from that link, Seattle Astronomy gets a small royalty at no cost to you! It helps us do what we do. Thanks!)

AOT is free, but remember to buy beer. Bring a lawn chair to create your own front-row seating!

Cosmic love

The Washington State University Planetarium in Pullman has a special show planned for Valentine’s Day, Wednesday, February 14. “Some Like It Hot” will show at 7 p.m. and again at 8:30. It’s not the movie with Marilyn Monroe, and Tony Curtis; this planetarium show is all about temperature—from the frigid to the muy caliente, the universe has it all.

Admission is $5 cash or check at the door. No credit cards are accepted at the planetarium.

Check our calendar page for a list of links to other planetaria in the area.

Astronomy club meetings

The Island County Astronomical also plans a public star party for 7 p.m. Friday, February 16 at Fort Nugent Park in Oak Harbor.

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