UF-led team use new observatory to characterize low-mass planets orbiting a nearby star

Published in University of Florida News on Thursday, April 9, 2012.

The narrow dust ring around Fomalhaut. Yellow at top is the ALMA image, and the blue at bottom is Hubble Space Telescope image. The star is at the location of the bright emission at the center of the ring.

CREDIT: A.C. Boley (University of Florida, Sagan Fellow), M.J. Payne, E.B. Ford, M. Shabran (UF), S. Corder (North American ALMA Science Center, NRAO), and W. Dent (ALMA, Chile), NRAO/AUI/NSF; NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite (UC, Berkeley), M. Clampin (NASA Goddard Space Flight Center), M. Fitzgerald (Lawrence Livermore National Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion Laboratory).

University of Florida astronomers have found compelling evidence for two low-mass planets orbiting the nearby star Fomalhaut, just 25 light years from Earth.

Twice as massive as the sun and 20 times brighter, Fomalhaut is surrounded by a ring of dust and debris, making it a favorite system for astronomers to study and a natural laboratory for testing planet formation theories.

In 2008, images of Fomalhaut taken by the Hubble Space Telescope led to the discovery of “Fomalhaut b,” the first extrasolar planet to be directly detected in visible light. At the time, astronomers believed it to be a giant planet, akin to Jupiter or Saturn, but later infrared images failed to detect the planet, meaning that it had to be smaller than Saturn.

UF astronomers, along with scientists from the new Atacama Large Millimeter Array in Chile, known as ALMA, and the National Radio Astronomy Observatory, used ALMA’s superior resolution and sensitivity to study the system in unprecedented detail. Their results indicate that there are not one, but two planets, with masses between that of Mars and a few times larger than Earth, working together to shape the ring of dust.

The new study reveals that the ring is sharply truncated in the inner and outer edges and is only about 16 astronomical units, or AU, wide, or about 16 times the distance between the Earth and the sun. That may seem large, but the center of the ring is about 140 AU, making the ring relatively very narrow. It also finds that the ring is vertically thin, about one-seventh as tall as it is wide. Those properties give important clues to explain the planetary system of Fomalhaut.

The results are described in a paper to appear this month in the Astrophysical Journal Letters.

“Combining ALMA observations of the ring’s shape with computer models, we can place very tight limits on the mass and orbit of any planet near the ring.” said Aaron Boley, a Sagan Postdoctoral Fellow at UF and leader of the study. “The masses of the planets must be small so they do not destroy the ring, but their masses cannot be too low or they would not shape the ring.”

Although Fomalhaut is a much hotter star than the sun, the planets are so far from their host star that they are among the coldest planets known around a normal star. They are thought to be low-mass bodies, but astronomers do not have enough data to tell whether they have a significant amount of hydrogen gas or are mostly rock and ice.

“ALMA observations show that Fomalhaut’s ring is even more narrow and thinner than previously known,” said Matthew Payne, an astronomer at the University of Florida who contributed to the study. “Fomalhaut b alone only explains the ring's sharp inner edge. Our analysis suggests that two planets, one interior and one exterior, are shepherding the ring, analogous to how Uranus’ moons Cordelia and Ophelia confine Uranus’ brightest ring.”

Credit: ALMA (ESO/NAOJ/NRAO). Visible light image: the NASA/ESA Hubble Space Telescope A. Fujii/Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble). Music: John Dyson (from the album Moonwind).

The Atacama Large Millimeter/submillimeter Array, located in the Atacama desert of northern Chile at an altitude of 16,400 feet is the largest astronomical project in existence. Still under construction, ALMA began scientific operations in September.

“ALMA may still be under construction, but it has already proved to be the world’s most powerful telescope for observing the universe at millimeter and submillimeter wavelengths of light.” said Stuartt Corder, an astronomer at the National Radio Astronomy Observatory and co-author of the study.

“Once ALMA is completed, we will be able to study systems like Fomalhaut with even greater detail, and see through the veil of dust that hides the early stages of planet formation,” said co-author Bill Dent, an astronomer at ALMA.

This research was supported by the NASA Sagan Fellowship Program, the National Radio Astronomy Student Observing Support Program and the University of Florida's College of Liberal Arts and Sciences. The Joint ALMA Observatory is a partnership of the European Organization for Astronomical Research in the Southern Hemisphere, the National Astronomical Observatory of Japan (on behalf of the National Institutes of Natural Sciences and Academia Sinica), and the NRAO (managed by Associated Universities, Inc. on behalf of the NSF and the National Research Council of Canada) in cooperation with the Republic of Chile.

Professor Eric Ford TEDxUF talk

TEDxUF talk by UF Astronomy Professor Eric Ford is available online, for those who missed it and for those who want to enjoy it again.

CanariCam is ready for science!

CanariCam, the infrared instrument onboard the world’s biggest optical-infrared telescope is officially ready for scientific research.

The instrument was built in UF by a team of astronomers and engineers led by astronomy professor Charles Telesco. Basically, it's a high-tech, heat-sensitive camera that will allow researchers to look for planets outside our own solar system and better explore hidden black holes at the centers of galaxies, among other tasks.

The Great Telescope CANARIAS, also known as GTC is the biggest optical-infrared telescope in the world, with a primary mirror of 10.4 meters (34.12 feet). The unique specifications of CanariCam, combined with this mighty telescope, form a cutting-edge scientific tool.

University of Florida is a 5% partner in the GTC, in operation since 2009. UF is developing and using instruments such as CanariCam to maximize the telescope’s scientific productivity for all the scientific community. In return, the University of Florida gets observation time for its own projects.

CanariCam capabilities include high-resolution imaging, spectrography, coronography and polarimetry. The latter is an exclusive feature in 8 to 10 meter class telescopes. This is a unique combination in a single instrument, according to professor Telesco.

“With this instrument, the GTC will allow projects impossible to do with other smaller telescopes and will be in the forefront of infrared astronomy for a very long time.” Telesco said.

Some bodies or regions of the universe emit infrared radiation, or heat, which is detected by CanariCam. This capability will spearhead research exploring planets outside our solar system and regions where planets and stars are forming. Also, the fact that infrared radiation can pierce easily cosmic dust clouds means that CanariCam would be able to see objects that are totally obscured at visible wavelengths.

UF Astronomy Professor, quoted in National Geographic

Astronomy Professor Eric Ford was quoted in National Geographic, last February 24th.

You can read it following this link: http://goo.gl/LNhj7

Reflections on Kepler's 3rd birthday



Artist's rendition of Kepler spacecraft. Credit: NASA/Kepler mission/Wendy Stenzel

Three years ago, I witnessed the launch of NASA's Kepler mission. As the first space mission designed from the ground-up to study exoplanets, it was a major juncture in the search for other worlds and all of astronomy. Yet, the launch was really one more opportunity to practice patience. As a part of the Kepler Science Team, I waited to learn of the spacecraft's health, then the pointing and focus, then the data quality, then enough data to begin to do science, then the first planet candidates, then the progress of our colleagues in improved data analysis techniques. Now, we wait for Kepler to observe long enough to find Earth-size planets in the habitable zones of solar-like stars.

As a member of the transiting timing variations working group, I'm also anxiously waiting for enough data to measure the masses of small planets, so we can map the transition between "super-Earth's" and "mini-Neptunes". These new classes of planets for which there is no analog in our solar system are actually quite common for other stars. Why doesn't our own solar system have any super-Earths (or mini-Neptunes)? How did Earth resist Icarus's urge to fly too close too the Sun for life, like most of the thousands of planets being discovered by Kepler? Is there something special about our solar system? Continued observations and analysis of the Kepler data provide best chance to address questions like these.

At the launch, several mission's founders were already a tight nit team. Over the last three years, I and my small research group at UF have become part of the Kepler family. I can't guess how many emails, telecons, heated debates we've had. Those have pushed us to work many late nights to search for planets, to vet planet candidates, to optimize the next quarter's target list, to provide some analysis in time for another team member's paper, to explain why NASA should keep the mission alive beyond 2012, and to convey results and the sense of wonder to the public. It's been an exhausting, but exhilarating ride. I hope we can hang on for a few more years.

Prof. Ford during the Kepler launch, 2009. Credit: NASA/Kepler Mission.

Kepler has opened our eyes to the power of time-domain astronomy, providing nearly-continuous, long-term and ultra-high precision photometry. The only analogy I can offer is to how much we learned about the universe when previous NASA missions made it possible to see the sky in wavelengths previously inaccessible due to Earth's atmosphere hanging over telescopes on the ground. Far above Earth's atmosphere, Kepler's data quality is so much better than anything before it that most astronomers are just beginning to appreciate the possibilities for studying planets and stars in ways never before possible. Kepler has already returned a treasure trove of data, one that will be mined by astronomers for many years if not decades into the future.

Kepler was always intended to be a stepping stone towards future missions that could study the atmospheres and surfaces of potentially Earth-like planets. I hope that humans will muster another great observatory optimized for exoplanet science, so we can realize those goals during my career, or at least my lifetime. If not, at least we have the Kepler Mission.

Professor Eric B. Ford.

Kepler Mission facebook page