UFO'S of UAP'S, ASTRONOMIE, RUIMTEVAART, ARCHEOLOGIE, OUDHEIDKUNDE, SF-SNUFJES EN ANDERE ESOTERISCHE WETENSCHAPPEN

A nontraditional life

Born in New York in 1944, Tarter (born Jill Cornell) spent her childhood with a father who encouraged her to dream, according to Scoles' book. Despite growing up in time where traditional gender roles were more regimented, she decided at a young age to be an engineer.

"Why do you want to take calculus? You're just going to get married and have babies," Tarter recalls a high school guidance counselor telling her. (She managed to do all three.) When she completed Cornell University's five-year undergraduate engineering program in 1965, she was the only woman out of 300 students.

Tarter's father, who told her she could accomplish anything as long as she worked hard enough, died when Tarter was 12. Her mother, who had encouraged her daughter toward more feminine roles, continued to provide her with quiet support after her father passed away, according to Scoles' book.

"I think that her mom being forced into this nontraditional role [of a single mother] maybe made her more accepting of [a nontraditional role for] her daughter," Scoles said.

And while her father had pushed young Jill to fulfill her dreams, "what she learned from her mom were the practicalities of how to work hard and get things done," Scoles said. "Her mom was the practical complement to her dad's dreaminess."

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In addition to her bachelor's degree in engineering physics, Tarter earned a master's degree from the University of California at Berkley, followed by a doctorate in astronomy in 1975. During her junior year at Cornell, she married Bruce Tarter. Between undergraduate and graduate school, she gave birth to their only child, a daughter, Shana.

Her marriage to Bruce struggled under the weight of her growing responsibilities. Eventually, the two divorced, and Tarter married fellow radio astronomer William "Jack" Welch.

The probability of success

Early in her career, Tarter came across a paper in the scientific journal Nature on the need to hunt for signals from advanced alien civilizations, according to Scoles. "The probability of success is difficult to estimate, but if we never search, the chance of success is zero," the paper read.

The idea sparked her imagination, and Tarter quickly became a proponent of SETI. The young field suffered a lot of blowback from scientists, according to Scoles, as researchers tried to determine if hunting for signals from alien civilizations was a serious scientific pursuit or a waste of time.

As a woman in astrophysics, which was (and continues to be) a male-dominated field, Scoles said it might have been easier for Tarter to get started in the fringe field "because she was already kind of a fringe character just by being a woman in this particular science." While some scientists may have been reluctant to enter the search for alien signals, Scoles said that Tarter wasn't as concerned because she was already unusual.

"There was a lot less stigma attached because everyone was already [saying], 'What [is] that girl doing?'" Scoles said.

Not long after its 1971 publication, Tarter received the NASA-sponsored Cyclops report, a 250-page document on humanity's ability to hunt for intelligent extraterrestrial life that was instrumental to SETI. According to Scoles' biography, Tarter didn't put the report down for two days. When she finished, she knew she wanted to be part of the search.

Tarter joined the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP), a project headed by fellow astronomer Stuart Bowyer, who had given her the Cyclops report. Today in its sixth iteration, SERENDIP hunts for signals from advanced civilizations by piggybacking on existing radio astronomy observations.

In 1984, Tarter wrote the charter for the SETI Institute, a nonprofit research organization. According to Scoles, the organization started out as a way to save NASA money, since the agency was funding the bulk of SETI research at the time. By separating them from the government, scientists could fundraise and accept donations while also applying for research grants that used federal funds. The divide also allowed SETI researchers to pursue what Scoles called "risky projects [that] NASA and the National Science Foundation didn't approve of but which turned the heads of the public and a few key philanthropists."

The institute proved a lifesaver once NASA began decreasing its budget for SETI research in the late 1980s. Tarter spent 1989 lobbying in Washington, D.C. Although some senators thought hunting for signals from other civilizations was "a fine idea," others found it irrelevant, since results couldn't be guaranteed in what Scoles called "a politically relevant time frame." In late 1993, the hunt for other civilizations was cut from NASA's budget. In her book, Scoles said the SETI Foundation is what saved SETI.

Today, the SETI Foundation not only hunts for signals from alien civilizations but also studies newly discovered exoplanets, hunts for hardy extremophiles on Earth that could give clues about how extraterrestrial life could evolve, and even studies our own planet.

Under Tarter's guidance, the SETI Institute built the Allen Telescope Array, relying on private donations to create a radio telescope that could hunt for signs of radio communications being transmitted by an intelligent alien civilization. The initiative to build a dedicated SETI array came from a series of 1997 workshops Tarter participated in, and culminated in the birth of 42 radio antennas, positioned in the Cascade Mountains in Northern California. The array began observations in October 2007. When funding dried up for the project, the array was sold to SRI International, a scientific nonprofit organization that uses it to probe objects orbiting Earth. Tarter negotiated evening use of the array for the SETI institute.

By the 1990s, Tarter had become a crusader for the cause, juggling both the science of the growing field and the challenges of politics and funding.

Tarter retired as director of the SETI Institute's Center for SETI Research in 2012, but she has continued to share her enthusiasm for the hunt. She's presented TED talks about SETI and been a guest on numerous podcasts. In 2004, she was named one of Time's 100 most influential people in the world.

"She's become more public in the last 10 to 15 years," Scoles said. "I feel like more people have heard of her now than before she was retired."

In researching the biography, Scoles said she spent a lot of time with Tarter, whom she describes in her book as "a fierce, stubborn, smart woman who asked big questions about the universe and didn't hear 'No' as 'No' but as 'Keep trying.'"

The key to Tarter's success, Scoles said, was her flexibility.

"Gradually, it became clear that she couldn't exactly set the path for how her life was going to go," she said. "She just became open to possibilities and, I guess, prepared for them.

"She was willing to abandon her own schedule for herself and see opportunities as they presented themselves rather than sticking very rigidly to a plan she had made before," Scoles said.

Astrophysicist Jill Tarter, shown here on a platform above the Arecibo radio telescope while she was working at NASA's Ames Research Center. Tarter went on to become a leader in the search for intelligent life beyond Earth.

An irreplaceable asset

Tarter's work in the hunt for extraterrestrial communications put her in contact with the well-known scientist and public figure Carl Sagan. According to Scoles' book, Tarter was surprised that their few brief professional meetings were enough to earn her a starring role in "Contact." Scoles said that the character of Ellie Arroway — in both the book and subsequent film — is very similar to Tarter.

"I think that, aside from the fact that [Arroway] finds aliens in the movie, it's pretty accurate to [Tarter's] personality," she said.

It was this movie that set Scoles on the path to becoming a radio astronomer when she was 12.

"I didn't know radio astronomy existed until I watched that movie," Scoles said. "I thought it was so cool that there was a science where you were essentially looking at space, but at the parts you couldn't see, and that there were some who were using it to look for aliens. That was like a double whammy of very cool things I didn't know people did for jobs."

Scoles studied radio astronomy at Agnes Scott College in Atlanta, serving an internship at Green Bank Observatory after her first year. Green Bank's radio telescopes was one of the first to hunt for SETI signals, and during her internship, Scoles stayed in the former house of SETI pioneer Frank Drake. Although Scoles ultimately decided to pursue a career communicating about science and astronomy, she credits "Contact" with kicking off her interest in the field.

"I think a lot of people had experiences like me," she said. "[Contact] inspired a lot of people of a certain generation."

Her fictional fame isn't something Tarter shies away from, Scoles said. When she asked the scientist how it felt to have such a well-known alter ego, she said that Tarter seemed glad to think that the movie inspired so many people to pursue a career in science.

By advancing the hunt for extraterrestrial life before there was even proof of planets existing beyond Earth's solar system, Scoles said that Tarter helped prepare researchers for a time when thousands of worlds would be known to exist around other stars. Her role as a researcher, combined with her ability to maneuver around bureaucratic hurdles, made her invaluable.

In the book, astronomer Margaret Turnbull testified to "the enormous impact that Jill has had — and that thanks to her we [exoplanet and SETI scientists] are all continuing to have — on the world, just by simply existing and being in the scientific community and pushing the frontiers in every direction."

"She's not replaceable," Turnbull said.

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Using a method first derived by astrophysicsts Sara Seager and Gabriela Mallen-Ornelas in 2003, Sandford and co-author David Kipping, also of Columbia, analyzed data on 66 Kepler stars to determine their densities. Their precision rivalled that of asteroseismology, a technique used on bright stars that uses oscillations in their shine to reconstruct their interior properties. While asteroseismology requires very precise brightness measurements, Sandford said, the new calculation needs less pristine data.

Essentially, the process works because how long a planet spends in front of its star is tied to the star's density. Planets that are far away from their stars spend less time in front of them — imagine a planet right at the star's surface, which would spend half of its orbit in front of it, versus one that is very far away, and only crosses in front for a quick part of its orbit, Sandford said. But at the same time, a planet has to move at a certain speed to maintain a steady orbit based on how massive the star is — if the planet is going too slowly, it will fall into the star, and if it's going too fast, it will fly away.

"We can then use that knowledge of [proportionally] how far the planet is from its star, combined with the duration of the transit, to solve for the stellar density," Sandford said. "If a planet is far away and yet takes a long time to transit, we know that the star must be big, puffy, and low-density; if a planet is close-in and yet transits quickly, we know that the star must be small, compact, and high-density."

In other words, the denser a star is — the more massive it is compared to its radius — the less time the planet spends in front of it.

Treasure trove

While researchers already knew about this relationship between transiting planets and their parent stars' densities, it's only since Kepler's launch in 2009 that more than a handful of transiting planets have been available for analysis, according to Sandford.

"We have this enormous treasure trove of data, and we can start to apply some of these ideas that people thought of way in advance before the data was ready," Sandford said. "That's what we've done here." [How Do You Spot an Alien Planet from Earth? (Infographic)]

This method requires that the researchers know the planet's orbit well, or that they can predict that it's circular. (Circular orbits tend to be common in systems with multiple planets.) It also requires researchers to know the planet's full orbit length — so it must have passed in front of the star more than once.

Once those criteria are established, researchers can use these calculations in two key ways: to determine if a transit is really caused by a planet or if it's a false positive, and to analyze the other planets in a multiplanet system.

That false-positive case was one of the uses Seager had in mind when the equation was first developed, she told Space.com: "If you get the stellar density from the light curve alone, and then if you get the stellar density because you already know something about its mass and size … and if those densities don't match up, the thing you're looking at is not a planet," said Seager, who was not involved in the new study. "It's a blended object; it's a false positive; it's something else."

"All the applications are exciting, whether you want to just measure the densities of the set of stars, or whether you're using it as a kind of comparison tool," she added.

During its primary mission, Kepler looked at the same set of stars for four years, but future exoplanet hunters such as NASA's Transiting Exoplanet Survey Satellite (TESS), set to launch in 2018, will spend a much shorter time on each part of the sky — just a month or so. In systems with multiple planets, if one orbits quickly enough for researchers to see more than one full orbit, that planet could act as an "anchor" to pin down the star's density, letting researchers learn about the orbits of the other planets, too.

"There's going to be a lot of habitable-zone planets that fall out in that window where their orbital period is longer than a month," Sandford said. "If we only see one transit, if we can't measure the period directly, it might be a very, very faraway planet, in which case it's too cold to have liquid water, or it might fall right in the middle of the habitable zone."

"If we can use our method to constrain the star, and from there to constrain the outer planet's period, that could be really interesting for prioritizing certain planets for follow-up if we know that they're likely to be habitable-zone, potentially the right temperature range for liquid water, type planets," she added.

Know the planet, know the star

According to Vincent Van Eylen, a researcher at Leiden University in the Netherlands who is uninvolved with the study, there's a saying that goes "Know thy star, know thy planet." Often, researchers use what they can glean about stars to identify what their planets might be made of and what the orbits look like.

Van Eylen's own research uses stars' densities and the durations of transits to learn about the planets' orbits — a reversal of Sandford's calculations.

"We don't know enough about stars, and everything we learn about planets somehow is indirect information that's related to stars," Van Eylen said. "In that way, it's kind of a sweet result that they can turn things around and actually learn about the planets, and thereby learn about the stars."

The new work has been accepted for publication in The Astronomical Journal and is available on ArXiv.org.

Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.