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There is something new under the sun and three Villanova astronomers have confirmed it. The new celestial object is a twin sun which has a mass, diameter, temperature and age closely resembling our own sun. Dr. Edward F. Guinan, ’64 A&S, professor of astronomy and astrophysics, Laurence E. DeWarf, instructor in the department, assisted by Ryan T. Hamilton, a junior astronomy and astrophysics major, have discovered 18 Scorpii, a fifth magnitude star located in the left claw of the constellation Scorpius. The Villanova astronomy team reported their findings at the American Astronomical Society (AAS) Meeting held last January in Atlanta, Georgia. Ever since, the twin sun has been starring in the headlines.

The twin sun, 18 Sco (as it is called for short), is located some 46 light years away. A light year is about 6 trillion miles, the distance light travels in a year. In cosmological terms, that’s not so far. And although the solar twin resides in our solar neighborhood, sun worshippers on this planet won’t need to shield against higher doses of UV rays from too much star shine. While 18 Sco is located in our galaxy, it is a faint star, the astronomers say. From our perspective on Earth, 18 Sco is only dimly visible to the naked eye. You probably won’t notice it unless you know where to look because 46 light years is just too far off in space. To be as brightly visible as our sun it would have to be much closer. “The twin sun would have to be about 93 million miles away from Earth, the distance from our sun to Earth,” said DeWarf, who worked closely with Guinan on the project.

Closer to campus, the announcement generated a frenzy of media interest and made stars of the astronomers. The Villanova professors and their student were the subject of a national press conference at the AAS meeting, and the story ran in several newspapers, including The New York Times, The Philadelphia Inquirer, and Delaware County’s Daily Times, among others. Articles are slated to be published in future issues of Astronomy, Sky and Telescope (April 2004), Science, “Quest,” as well as the fall issue of Villanova’s new Academics magazine. Guinan also was interviewed on CN8 TV’s Comcast Newscasters last February.

Guinan has been studying the star since 1995 as part of an ongoing NASA-sponsored program called “The Sun in Time.” His goal is to identify and study sun-like stars, called solar analogues, to compare the similarities and differences. “The emphasis was actually to identify and study stars younger than the Sun—that is, find the youngest sun,” said Guinan. “You can’t go back in time with the sun and figure out what the young sun or its magnetic activity was like, so we observe stars that are just like the sun but younger. The age of the present sun is 4.6 billion years.”

Finding a solar twin, nevertheless, was actually a serendipitous discovery for the astronomers. “This star is just one of 20 stars nearby that have similar properties to our sun,” said Guinan. “To do a direct comparison among other stars and our sun, you need solar proxies. So, ascertaining a true solar proxy has been important for that,” he noted. Their observations have also included examining solar analogs (twins) representing every stage of activity from the sun’s birth 4.6 billion years ago.

Guinan, who is the senior investigator for the twin sun project, is still amazed by the media interest in 18 Sco. While the solar twin is important for scientific purposes, it doesn’t answer the questions frequently asked by reporters: Does a twin sun mean there is another planet like Earth? Does it mean there is life elsewhere in the universe?

The astronomers cannot answer those questions now. The technology that could probe for the data required for those answers does not exist yet but will in the next decade.

Still, Guinan and DeWarf both agree on one thing. It is possible the twin sun could have some kind of solar system and possibly planets around it. But at present, there’s no way for astronomers to confirm or deny the speculation. “The twin sun could have a planetary system with terrestrial planets orbiting around it, or even a planet like Earth, but at present we would not be able to detect them,” said Guinan. Right now, science and technology do not have the sophisticated astronomical instruments needed to observe the presence of an Earth-like planet orbiting 18 Sco. That doesn’t mean they are not trying to find planets.

“There are no really large planets orbiting around this star, but we can’t exclude there may be any small planets yet,” added DeWarf. One way that astronomers can detect the presence of a planet is by the gravitational influence a planet exerts on a star. “When a planet orbits a star, the star actually recoils—it wobbles a little bit because of the gravitational pull,” he explains. “We can measure a star’s wobbling motion to a very high precision. But it takes a pretty large planet to make a star wobble significantly to be detected.”

A large planet orbiting close to the host star would cause a significant wobble that astronomers could easily detect. “A massive planet like Jupiter would make the sun or star move in space just a little bit,” noted Guinan. “Its reflex orbital speed would be less than 15 meters per second—a tiny amount that the sun moves--but we have five years of observations and data so far shows no evidence of a massive planet, the size of Jupiter, orbiting near to 18 Sco.”

For now, it is safe to say humans may be as unique as some maintain. “We have only one example of how life works, and that’s the Earth,” said DeWarf. “Are we atypical or not, or are we alone or not? Those are the big questions. As soon as technology improves, we might see something that would give us a clue.”

In the meantime, Guinan, DeWarf and Hamilton recently reanalyzed all of the collected data before the team publishes their research on 18 Sco in a professional journal. After the AAS meeting, the astronomers scrupulously reexamined their data, double checked the numbers and re-determined the star’s intrinsic brightness. “We also ran a new stellar evolution computer model—a code that gives us its age and mass. We’ve done that already, but we did it again,” said Guinan. “I wanted to run a new computer iteration using a new, more sophisticated stellar evolution program, because we’re nearly ready to publish the major paper on it. Age and mass are the most important quantities in verifying the match to the sun. You can’t have a twin sun if it is not the same age. A major part of our contribution is that we were able to determine a precise age and show the best match to our sun in every way,” Guinan stated.
Valuable research

It’s great to have a twin sun. The discovery is an important find for astronomers looking for new planets and for those studying the sun itself. But the confirmation of a solar twin has generated a flood of professional interest from scientists worldwide (including astronomers in Austria, Germany and Spain and at the University of California, Berkeley, and University of Hawaii). Guinan has already been working with astronomers who were studying 18 Sco but were exploring different aspects of the star. As the result of 18 Sco’s publicity, he’s been contacted by other astronomers. For example, one group is directly measuring the star’s angular diameter using a prototype interferometer, a new powerful network of telescopes, and Dr. Robert Thompson of the Jet Propulsion Lab recently measured 18 Sco’s diameter to be exactly the same as our Sun.

In addition, scientists in related fields have contacted Guinan to share data or collaborate on his research. He is now working with astro-biologists and astero-seismologists (who work in an area called astero and helioseismology)--as well as with the astronomers at other institutions. “Astero-seismologists study the complex vibrations of stars and the sun. “The sun vibrates with thousands of frequencies; it’s quivering,” notes Guinan. There are satellites in orbit that can observe these oscillations in other stars. “One of the groups have adjusted their program to observe 18 Sco.”

Guinan began scrutinizing 18 Sco more intensely after attending a special “Solar Analogs” meeting in Flagstaff, Arizona, in 1997. At this meeting, Brazilian astronomers suggested that 18 Sco might be a good match for our sun. According to Guinan, Dr. Giusa Cayrel an astronomer from France and her Brazilian colleagues, Lucio de Silva and Porto de Mello, suggested 18 Sco as a very good match to the sun in a paper they presented there. The team was credited for their suggestion, but it seems they did not pursue the research further. Also, their research lacked supporting quantities and data. “It was good match but more work needed to be done before 18 Sco could be considered a true solar twin,” noted Guinan.

It was ultimately Guinan and DeWarf’s eight years of thorough research that confirmed the suggestion. “Studying this star within our Sun in Time Program, we were able to find how old is from the level of magnetic activity,” he said. “So we built upon their project by doing our own photometry, which is our specialty, and studying ultraviolet observations. We used data from the International Ultraviolet Expolorer, with observations of our own from our automatic telescopes, in Southern Arizona, to see if we could observe a cycle of magnetic activity or rotational effects.” Reexamining that data, the Villanova astronomers’ research yieleded more solid evidence. “Our research is pretty much iron-clad in that 18 Sco is so far the best match to our Sun. Finally, we ran more sophisticated models, collected more data that included the magnetic effects, which is what we specialize in.”

Several stars have been past candidates for a solar twin, but 18 Sco is the most recent and best candidate, according to Guinan. “It has the same color, temperature, mass, surface chemistry, and is about the same age. When you find a star that has about the same mass and same age as the sun that means the radius and temperature will be the same, because mass and age determine how big the star is will be. 18 Sco has a temperature within 20 degrees Fahrenheit of the Sun’s 9,943 Fahrenheit surface temperature. We think it has the same mass within two to three percent, and has the same luminosity within a two percent error. But age is the really important factor, because if the star isn’t the same age, it can’t be a twin. And we were able to calculate a good age and show that 18 Sco is a really close match. A better age estimate of 18 Sco is being made by Spanish colleague, Dr. Ignasi Ribas at the University of Barcelona,” added Guinan.

Guinan said he was contacted by a team astrobiologists from the Astrobiology Institute at Graz, Austria. After hearing an earlier paper he presented about the “Sun in Time” program, they realized they needed his material to further their research, and have been collaborating with him ever since. His findings have thus provided an opportunity for him to expand his research into another discipline, which he finds exciting.

“For intelligent life to exist, you don’t just have a sun-like star and an Earth-like planet. You also need a large moon,” Guinan noted. To make a short story of long science—i.e., complex scientific inquiry-- intelligent life requires more than a planet in a habitable zone orbiting a star like our sun. “For a long time, many scientists believed that’s all you needed, but it turns out you need the moon, and a big one, to fix the rotation axis of the planet, and to stabilize the Earth’s climate in order for intelligent life to evolve on a planet like Earth.”

Professionally, it’s also nice to have a twin sun. It not only serves as a substitute for astronomers to observe the Sun at night, but the solar twin holds enormous value and potential for science in general. “Scientists and observers are always looking for standards,” said Guinan. “The Sun is a standard, but isn’t visible at night. So this star because it really matches well, will serve as a “night sun”—as a standard star to which to compare your observations.”

Local astronomer

Guinan, a resident of Edgemont, Pa., graduated from Monsignor Bonner High School in Drexel Hill before enrolling at Villanova. He joined the faculty in 1969 and says still gets excited over astronomical discoveries. The Villanova professor has had more than a few major research finds. He and Frank Maloney, associate professor of astronomy and astrophysics at Villanova, are credited with discovering the rings around Neptune, in 1982.

Guinan also was a co-author of a recent paper theorizing how the young sun may have played a major role in the loss of water from Mars, titled “Loss of Water from Mars: Implications for the Oxidation of the Soil.” Last May (2004), Guinan and student Scott Engle presented a paper at the AAS meeting in Denver on the North Star, Polaris, discussing their research that proves the star may be changing very rapidly with time.

He feels lucky he is living in “a wonderful time for astronomy and astronomers.” “This is the golden age of astronomy,” he told a reporter recently. “We are learning fantastic things all the time. It’s an exciting time to be an astronomer. I made the right choice in going into this field.”
Having grown up in Upper Darby, Pa., as a youth he was fond of science in general, and he watched Flash Gordon, read science fiction, especially Arthur C. Clarke books, and later enjoyed Star Trek. He credits as his science mentor, Doug Aberle, a pharmacist at Shirley Court Pharmacy in Upper Darby, where Guinan worked after school. He fondly recounts how Aberle helped him mix fuel for the rockets they made in his parent’s basement or garage. With a chuckle Guinan jokingly recalls, “If the rocket blew up, it would have taken down the whole block.”

More recently, he traveled to several cities in Iran to consult with Iranian astronomers and students about the construction of a large robotic telescope in central Iran. Guinan is helping also in the selection of the best location for this observatory. Earlier, during 1975 to 1978, Guinan helped set up the first modern observatory in Shiraz, Iran.

Stellar research for astronomy major Ryan Hamilton ‘05

According to Guinan, astronomer Larry DeWarf, has been invaluable in directly assisting him by “meticulously collecting and confirming the data on the twin sun project since DeWarf arrived at Villanova in 1993.” He, also supervised undergraduate Ryan Hamilton over what became the undergraduate’s summer research project.

Hamilton will graduate with a degree in astronomy and astrophysics in 2005, and according to the news reports, he’s already a “rising star.” He’s also another reason why finding a twin sun is valuable research. It inspires protégé undergraduate astronomy majors. The cutting-edge research Hamilton conducted with Guinan and DeWarf has already helped to chart his future toward a stellar career. The astronomy major at Villanova requires students that conduct research with faculty members and that they publish their results in a paper accepted by a professional journal. At the AAS meeting last January, when Hamilton presented a poster paper and answered questions on the twin sun, as well as acting as a spokesperson on a panel session with his mentors Guinan and DeWarf, he was already performing like a professional. Since then, Hamilton also participated when the astronomers were invited to give a presentation of their research to Villanova’s board of trustees and University president, the Rev. Edmund J. Dobbin, O.S.A. ‘58. Hamilton will also be one of the authors listed on the final professional paper that will be submitted for publication this summer.

As a youngster Hamilton was fascinated by outer space and always enjoyed science fiction movies like “Star Trek” and “Star Wars.” Hamilton says he purchased his first telescope, a 4” instrument, after receiving a small inheritance from his grandfather. “When I came to Villanova, I was surprised to see that one of the small finder telescopes that we use to get ourselves around in the sky was the same size as the one I have at home,” said Hamilton. “My own telescope is now strapped to the side of another huge one.”

Hamilton decided to come to Villanova because he preferred to attend college close to his Bethel Township, Pa., home. But he didn’t always want to be astronomer. “After I got my telescope, I spent a lot of time in the backyard, looking at the moon and planets, but I didn’t know what I wanted to do with my life. It wasn’t until I got to Villanova that it really solidified. I had really great physics and calculus teachers in my freshman year: Drs. Morgan Besson and Robert Styer [respectively], and they were great classes. That let me on to say ‘OK, I really like doing this. Let’s see what else is good, and the astronomy classes just nailed it.’”

Thrilled with his experience, Hamilton said,” I didn’t realize what a fantastic program Villanova’s astronomy department has here. Villanova’s programs are incredibly strong. Just look up and down the hallways and see all the student poster papers that have been presented at AAS meetings. You’ll see the results of students doing research. Going to the AAS meeting and presenting my own poster, and participating a press conference is an experience that never would have happened had I gone somewhere else.”

Working on the twin sun project has been invaluable experience for the 20-year old. “The twin sun will help us understand our own sun,” said Hamilton. “At the AAS meeting, I had a chance to talk with other scientists, including one from an upcoming mission called Kepler. It’s designed to look for terrestrial-sized planets. There’s technology on the drawing boards that can detect planets the size of Earth around other stars, Kepler being one of them. So this work helps those projects along because they need stars to look at. Also we don’t understand a whole lot about our own sun. By studying another star—by comparing two similar stars--you always learn more. But just by looking at our own sun, you don’t really know what it’s about until you put it into place with everything else. And that’s what the project has helped to do.”

Hamilton has already submitted an abstract for a paper he has co-written with another Villanova astronomer, Dr. Edward Sion. He will travel with Sion and other astronomy majors to attend the next AAS meeting held in Denver last May where he will present another poster paper, this time on research he conducted for Dr. Sion (titled “Dwarf Novae in Outburst with Newly Determined Parallaxes Analyses of VY Aquari and RU Peg”).

DeWarf explained that “Hamilton is part of one the country’s largest and best astronomy program for undergraduates only.” He conducted his research for this project under a grant funded by NASA, the National Science Foundation, and the Delaware Space Grant Consortium through the Undergraduate Summer Research Assistance Program. And, astronomy is definitely in his future. After graduation, Hamilton hopes to enroll in a graduate program and continue on for a Ph.D. in the field.