Tag Archive for Redfield

“Evaporating” Planet May Hold Clues to Gas Giants, Other Exoplanets

Seth Redfield, assistant professor of astronomy and Adam Jensen, visiting assistant professor of astronomy, documented an exoplanet that is slowly evaporating “hot hydrogen.”

In a nearby solar system, a planet the size of Jupiter orbiting a star similar to our own sun is doing something that has astrophysicists very intrigued: It’s dissolving–albeit very, very slowly.

The findings are detailed in a study by primary investigators Adam Jensen, visiting assistant professor of astronomy, and Seth Redfield, assistant professor of astronomy. They made the majority of their observations using the 9.2 meter telescope at The University of Texas’s McDonald Observatory. The paper, “A Detection of Ha In An Exoplanetary Exosphere,” will appear in the June 1 issue of The Astrophysical Journal.

Jensen and Redfield studied the planet, HD 189733b which is about the size of Jupiter, orbiting a star 63 light years from Earth.

The planet in question, a gas giant similar in size to Jupiter called HD 189733b, orbits a class K star, which is about 63 light years from Earth–a virtual next-door neighbor in astronomical terms.

What Jensen and Redfield observed was HD 189733b discharging significant amount of atomic hydrogen into space.

“This type of evaporation of atomic hydrogen, or what is called ‘hot hydrogen,’ is something that has never been observed before,” says Redfield. “When we first saw the evidence we thought, ‘Wow, can that be right?’ But more careful analysis and cross-checks confirmed it. At that point we got really excited because we knew we’d found an important phenomenon.”

The orbital path of HD 189733b is 12 times closer to its star (HD 189733) than Mercury is to our own sun (a class G star, and 32 times closer than the Earth is to the sun. While somewhat smaller than the sun, the star HD 189733 is more volatile–often discharging massive solar flares hundreds of miles into space–and dangerously close to HD 189733b.

The astronomers’ observations indicate an interaction between the stellar activity and the planet’s atmosphere. This can have implications for understanding other planetary systems, especially those which may have potentially habitable planets.

That is not the case with HD 189733b, a gas giant orbiting very close to a somewhat volatile star. But is it that very degree of proximity that is causing the planet to slowly evaporate?

“This mass loss is almost certainly due to the proximity of the planet HD 189733b relative to its central star, HD 189733, along with the star’s radiation,” says Jensen. “This isn’t to imply it’s not going to last much longer. It is a very slow evaporation, and ultimately the planet will lose only 1 percent of its mass. Still, that is significant.”

What Jensen, Redfield and other observers contributing to the paper saw to indicate this was a significant spike in spectrographic readings suggesting the planet was shedding significant amounts of hydrogen. They were also able to detect it using visible light–another first. Past detections of hydrogen dissipation, which have been rare, used ultraviolet light.

“We’ve only been able to observe exoplanets for about 20 years, and we’ve detected atmospheres in just a few dozen of those, so this is an exciting finding,” Redfield says. “We’re hoping to do more observations of this planet and others that are similar in their composition and positioning to their stars. This will help us determine how rare of a phenomenon this is.”

The astronomers hope to do further studies at the McDonald Observatory, and perhaps try to book time on the Hubble Telescope, which would afford them the clearest view of HD 189733b.

The astronomers were supported in this study by a grant from the National Science Foundation.

Redfield Participates in NASA’s IBEX Mission Press Conference

Seth Redfield, assistant professor of astronomy, speaks at a press briefing about NASA's IBEX (Interstellar Boundary Explorer) spacecraft, which sampled multiple heavy elements from within our solar system and beyond. IBEX found some astonishing data in the process.


Seth Redfield had to cut short his first Astronomy 224 class of the 2012 spring semester, but he had a good excuse: he was presenting at an international press conference being held by NASA on one of its recent missions.

Redfield, an assistant professor of astronomy, was chosen by NASA to be a non-mission expert to help verify results from the space agency’s ongoing IBEX (Interstellar Boundary Explorer) mission, an unmanned probe that analyzes the interstellar boundary that protects much of our solar system, including the Earth, from deadly cosmic rays from interstellar space.

One of Redfield’s primary areas of research deals with these types of clouds, more generally known as local interstellar medium (LISM), and his models had been used by NASA in the past,

Institute Supports Redfield’s Cool Star Winds Research

Seth Redfield

Seth Redfield, assistant professor of astronomy, received a grant worth $65,932 from the Space Telescope Institute to support a project titled, “Cool Star Winds and the Evolution of Exoplanetary Atmospheres.” The grant expires in October 2014.

Redfield is observing stars that are host to their own planetary systems.  These “exoplanets” were only discovered in the last decade or so, and since their discovery, astronomers are very interested in learning more about the properties of these planets and their atmospheres.

“Invariably, the study of exoplanets is really an exercise in putting life on Earth into a cosmic context.  How common are planets?  Are these planets ‘habitable,’ which is just shorthand for, could liquid water exist on this planet? This project seeks to address the important relationship between a planet/atmosphere and its host star,” Redfield explains.

Scientists know that the host star plays a major role planets and their atmospheres, and the diversity of stars in our galaxy is quite extreme.  One way that stars influence their planets is through a stellar “wind,” which is composed of charged particles that escape the gravitational field of the Sun and travel out into interplanetary space. When solar wind interacts with the Earth’s magnetic field, it creates aurora borealis.The solar wind might have been so strong when the Sun was young, that it could have effectively sand-blasted an entire planetary atmosphere away, particularly if that planet did not have a strong magnetic field,” Redfield says. This may have happened with Mars, which does not have a strong global magnetic field like Earth does.
This would explain why we see ancient evidence of surface water, which implies Mars had a substantial atmosphere at the time, but today, Mars is arid and has a very minimal atmosphere.
“The observations I plan to do will measure the interaction of stellar winds with the surrounding interstellar gas and dust.  This will give us a handle on the strength of the stellar wind, and enable us to explore the impact of these winds on the planets that are currently around these stars,” he says. “These stars are ‘cool’ not only because they are incredibly amazing to study, but because their surface temperatures are on the lower side compared to other stars we observe.”
The Sun is also a cool star.

Malamut’s Astronomy Research has been Out of this World

Craig Malamut ’12

In the summer of 2010 Craig Malamut traveled to the Easter Islands to study and photograph a rare solar eclipse. Soon after his eclipse observations were completed, NASA used one of his photographs in their official materials on the event. He also spent a week collaborating with astronomers from the University of Chile in Santiago to study Pluto’s atmosphere as it obscured the light from a faint star. This year, Malamut has coauthored two papers for astronomical journals and is analyzing data from the Hubble Space Telescope on gas and dust clouds lying near the sun and other nearby stars.

It’s the kind two-year research run that many scientists would be proud and excited to have accomplished. But Craig Malamut is not a paid researcher or a member of any faculty. He’s a college student who is still working through his senior year at Wesleyan.

Malamut, an astronomy major, has been working at an advanced level for someone who has yet to earn a bachelor’s degree. While the experience has been intense, he hasn’t been intimidated by the complexity of the work or felt limited by his undergraduate standing. “I’ve felt very prepared for this level of research from the courses, discussions, and advising I received from the astronomy department,” he says. “Professors Herbst, Moran, Redfield, and Kilgard do a great job getting their students involved early in astronomy research, whether at Wesleyan or abroad.”

He also took part in the Keck Northeast Astronomy Consortium Research Experience for Undergraduates (KNAC REU) Williams College. Several members of astronomy faculty also recommended him for the Keck-sponsored program in the Easter Islands.

Telescope Science Institute to Support Redfield’s Cool Stars Project

Seth Redfield

Seth Redfield, assistant professor of astronomy, received a $55,973 grant from the Space Telescope Science Institute to support the Advanced Spectra Library Project: Cool Stars.

The grant will allow Redfield to facilitate the analysis of data collected on the Hubble Space Telescope and travel to meetings to present the results. He will collaborate with 20 other researchers from around the world on the project.

“All astronomers, worldwide, put in proposals once a year to use the Hubble to get observations.  They get about 10 times more requests than they have time to give,” Redfield explains. “If you are approved, you send the details of the observations to them, they program them into the computer onboard the spacecraft, and then a couple weeks later you get an e-mail to download your data from the Space Telescope Science Institute web site.”

The project will receive data  from 150 orbits, which is 6 percent of all the time on the Hubble allocated to astronomers worldwide this year. These observations will produce a high quality spectroscopic atlas of eight sun-like, or “cool” stars, which will be used by the wider community for decades to come.

The immediate scientific research enabled by this project will involve magnetic activity, space weather, disk winds of young stars, red dwarf flares, erosion of exoplanet atmospheres, and the properties of the intervening gas and dust in Earth’s cosmic neighborhood.

The grant will support the Cool Stars program through Nov. 30, 2013.

Herbst, Redfield Published in Astronomy Publications

Bill Herbst, the John Monroe Van Vleck Professor of Astronomy, and Seth Redfield, assistant professor astronomy, are co-authors of the article, “Gas Absorption in the KH 15D System: Further Evidence for Dust Settling in the Circumbinary Disk,” published in The Astrophysical Journal, Volume 711, Issue 2, pp. 1297-1305 in March 2010. Their data supports a picture of a particular circumbinary disk as being composed of a very thin particulate grain layer composed of millimeter-sized or larger objects that are settled within whatever remaining gas may be present.

Herbst also is the author of “Periodic variability in the emission spectrum of T Tauri,” published in Astronomy and Astrophysics, Volume 511 in February 2010.