SkyWord

Skyword: June 2016

JUNE 2016

Director’s Message

Director's Message

Taft Armandroff

Taft Armandroff, Director

Frank and Susan Bash Endowed Chair

Welcome to this June issue of SkyWord. I feel privileged to share with you some of the recent exciting research happening on McDonald Observatory telescopes as well as unique scholarly and outreach accomplishments of esteemed colleagues and alumni.

In research news, this issue is bringing you details of UT Austin astronomer Howie Marion's study of a distant supernova with the Hobby-Eberly Telescope, work that is helping scientists better understand the origins of these exploding stars. We also tell how UT Austin Hubble Fellow Andrew Mann has used the Harlan J. Smith Telescope and its IGRINS instrument to discover a planet in the Hyades cluster, the closest open star cluster to Earth.

In outreach news, Assistant Director Anita Cochran and I represented McDonald Observatory in a public forum called “Searching for Earth 2.0” at the 2016 South by Southwest Interactive Festival held in Austin on March 13. The one-hour video is posted on our YouTube site, which is available at the end of the article.

In the Spotlight section, we congratulate Brendan Bowler on winning one of the most prestigious fellowships in astronomy — the highly-competitive Hubble Fellowship from NASA and the Space Telescope Science Institute (STScI). We are thrilled for him to continue his work at McDonald Observatory, which will include using the Smith Telescope with IGRINS and also the Hobby-Eberly Telescope.

The Featured Image is that of UT alumnus Alan Stern giving a talk at the Board of Visitors February dinner with the image of NASA’s New Horizons mission, that he leads, in the background.

Research

First Discovery of a Binary Companion for a Type Ia Supernova

The blue-white dot at the center of this image is supernova 2012cg, seen by the 1.2-meter telescope at Fred Lawrence Whipple Observatory. This supernova is so distant that its host galaxy appears here as only an extended smear of purple light. Credit: Peter Challis/Harvard-Smithsonian CfA

by Rebecca Johnson

AUSTIN — A team of astronomers led by The University of Texas at Austin’s Howie Marion has detected a flash of light from the companion to an exploding star. This is the first time astronomers have witnessed the impact of an exploding star on its neighbor. It provides the best evidence on the type of binary star system that leads to Type Ia supernovae. This study reveals the circumstances for the violent death of some white dwarf stars and provides deeper understanding for their use as tools to trace the history of the expansion of the universe. These types of stellar explosions enabled the discovery of dark energy, the universe’s accelerating expansion that is one of the top problems in science today. The work is published in a recent issue of The Astrophysical Journal.

The subject of how Type Ia supernovae arise has long been a topic of debate among astronomers.

“We think that Type Ia supernovae come from exploding white dwarfs with a binary companion,” Marion said. “The theory goes back 50 years or so, but there hasn’t been any concrete evidence for a companion star before now.”

Astronomers have battled over competing ideas, debating whether the companion was a normal star or another white dwarf.

“This is the first time a normal Type Ia has been associated with a binary companion star,” team member J. Craig Wheeler said. “This is a big deal.” Wheeler is a supernova expert and professor of astronomy at the university.

The binary star progenitor theory for Type Ia supernovae starts with a burnt-out star called a white dwarf. Mass must be added to that white dwarf to trigger its explosion — mass that the dwarf pulls off of a companion star. When the influx of mass reaches the point that the dwarf is hot enough and dense enough to ignite the carbon and oxygen in its interior, a thermonuclear reaction starts that causes the dwarf to explode as a Type Ia supernova.

For a long time, the leading theory was that the companion was an old red giant star that swelled up and lost matter to the dwarf, but recent observations have virtually ruled out that notion. No red giant is seen. The new work presents evidence that the star providing the mass is still burning hydrogen at its center, that is, that this companion star is still in the prime of life.

According to team member Robert P. Kirshner of the Harvard-Smithsonian Center for Astrophysics, “If a white dwarf explodes next to an ordinary star, you ought to see a pulse of blue light that results from heating that companion. That’s what theorists predicted and that’s what we saw.

“Supernova 2012cg is the smoking — actually glowing — gun: some Type Ia supernovae come from white dwarfs doing a do-si-do with ordinary stars.”

Located 50 million light-years away in the constellation Virgo, Supernova 2012cg was discovered on May 17, 2012 by the Lick Observatory Supernova Search. Marion’s team began studying it the next day with the telescopes of the Harvard-Smithsonian Center for Astrophysics.

“It’s important to get very early observations,” Marion said, “because the interaction with the companion occurs very soon after the explosion.”

The team continued to observe the supernova’s brightening for several weeks using many different telescopes, including the 1.2-meter telescope at Fred Lawrence Whipple Observatory and its KeplerCam instrument, the Swift gamma-ray space telescope, the Hobby-Eberly Telescope at McDonald Observatory, and about half a dozen others.

“This is a global enterprise,” Wheeler said. Team members hail from about a dozen U.S. universities, as well as institutions in Chile, Hungary, Denmark, and Japan.

What the team found was evidence in the characteristics of the light from the supernova that indicated it could be caused by a binary companion. Specifically, they found an excess of blue light coming from the explosion. This excess matches with the widely accepted models created by U.C. Berkeley astronomer Dan Kasen for what astronomers expect to see when a star explodes in a binary system.

“The supernova is blowing up next to a companion star, and the explosion impacts the companion star,” Wheeler explained. “The side of that companion star that’s hit gets hot and bright. The excess blue light is coming from the side of the companion star that gets heated up.”

Combined with the models, the observations indicate that the binary companion star has a minimum mass of six suns.

“This is an interpretation that is consistent with the data,” said team member Jeffrey Silverman, stressing that it is not concrete proof of the exact size of the companion, like would come from a photograph of the binary star system. Silverman is a postdoctoral researcher at UT Austin.

Only a few other Type Ia supernovae have been observed as early as this one, Marion said, but they have not shown an excess of blue light. More examples are needed.

“We need to study a hundred events like this and then we’ll be able to know what the statistics are,” Wheeler said.

This work is sponsored by National Science Foundation grants AST-1109801, AST-1211196, and AST-1302771.

— END —

Media Contacts:

Rebecca Johnson
The University of Texas at Austin
+1 512-475-6763

Christine Pulliam
Harvard-Smithsonian Center for Astrophysics
+1 617-495-7463

Science Contacts:

Dr. G.H. (Howie) Marion
Research Fellow
The University of Texas at Austin

Dr. J. Craig Wheeler
Samuel T. and Fern Yanagisawa Regents Professor in Astronomy
The University of Texas at Austin
+1 512-471-6407

Dr. Jeffrey M. Silverman
NSF Astronomy and Astrophysics Postdoctoral Fellow
The University of Texas at Austin
+1 512-471-7216

Dr. Robert P. Kirshner
Clowes Professor of Science, Harvard University
Harvard-Smithsonian Center for Astrophysics
+ 1 617-495-7519

Newly Discovered Planet in the Hyades Cluster Could Shed Light on Planetary Evolution

Smith Telescope with clouds

by Rebecca Johnson

AUSTIN — University of Texas at Austin astronomer Andrew Mann and colleagues have discovered a planet in a nearby star cluster which could help astronomers better understand how planets form and evolve. The discovery of planet K2-25b used both the Kepler space telescope and the university’s McDonald Observatory, and is published in a recent issue of The Astrophysical Journal.

The planet orbits a red dwarf star, a star smaller and dimmer than the Sun. Red dwarfs are the most abundant stars in our galaxy. The star is located in the Hyades star cluster, the closest open star cluster to Earth. Its stars are young, so their planets must be young, too.

“Open clusters are powerful tools as all the stars formed with the same age and composition,” Mann said. Once many planets are found orbiting young cluster stars, “we can compare those to planets orbiting older stars elsewhere to see if they are different in some fundamental way — to see how planets change with time.”

For instance, he said, if planets orbiting young stars are farther from their host stars than their older counterparts, it suggests that planets migrate over their lifetimes. They may form farther out and migrate inward. Many exoplanetary systems have large planets orbiting close to their stars, unlike our own solar system. This kind of research could test the theory of planetary migration.

After finding many more examples of planets orbiting young stars, “we can put numbers on this,” Mann said. “This could even give us a glimpse into what our solar system looked like” in the past.

The planet in the Hyades is four times the size of Earth, or about the size of Neptune. Compared to almost all other planets found orbiting red dwarf stars, it’s extremely large. “Almost all of those are less than twice the size of Earth,” Mann said.

The planet’s large size for its parent star suggests that the planet might have a puffy hydrogen and helium atmosphere. Radiation from the star could slowly strip away this atmosphere over time, he said.

“This could have major implications for our understanding of how planets evolve, including Earth-like planets, as we need to know how well a planet can hold an atmosphere given a certain set of conditions to tell how long it remains habitable.”

Amateur astronomers Thomas Jacobs and Daryll LaCourse found this planet candidate in the freely available K2 data from the Kepler space telescope’s extended mission. They contacted Mann, who followed up the tip by observing this red dwarf star with the new IGRINS instrument on the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory.

“Young stars are hard to follow up without something like IGRINS,” Mann said. Because it’s a red dwarf, the star is cool and needed to be studied in infrared light with high spectral resolution. The instrument’s high resolution allows astronomers to rule out the chance that the star has a stellar companion, rather than an orbiting planet. It also helps to confirm that the star is a member of the Hyades cluster, by measuring the star’s velocity and making sure it matches that of the cluster.

— END —

Media contact:

Rebecca Johnson
McDonald Observatory
The University of Texas at Austin
rjohnson@astro.as.utexas.edu
512-475-6763
 

Science contact:

Dr. Andrew Mann
McDonald Observatory
The University of Texas at Austin
amann@astro.as.utexas.edu
512-471-6493

Education & Outreach

Searching for Earth 2.0 at SXSW 2016

"Searching for Earth 2.0 at SXSW 2016" panel

From left: Taft Armandroff, Anita Cochran, Cyril Grima, David Hoffman, and Dan Jaffe. Credit: Marsha Miller/UT Austin.

by Rebecca Johnson

The hunt for Earthlike planets is in full swing! Five UT Austin scientists appeared before an eager audience on March 13 to give their insights on “Searching for Earth 2.0” at the 2016 South by Southwest (SXSW) Interactive Festival. Held in downtown Austin at the university’s Launch Pad site, the panel discussion gave audience members a chance to ask a plethora of questions relating to finding another Earth, and about finding intelligent life on another planet. Topics ran the gamut from technology, to aliens, to politics.

Organized by Dan Jaffe, astronomy professor and the university’s Vice President for Research, the panel featured Jaffe, McDonald Observatory director Taft Armandroff, assistant director and comet expert Anita Cochran, planetary scientist Cyril Grima of the Jackson School of Geosciences, and professor David Hoffman of the Department of Molecular Biosciences.

The panelists discussed different aspects of the search for Earthlike planets, and talked about their hopes for the future.

Hoffman, an expert on life in Earth’s extreme environments, said he was looking forward to scientists being able to decode the contents of the atmospheres of extrasolar planets, as atmospheres hold clues to what kind of life may be present.

Armandroff, in turn, emphasized technology — both what is needed for the future as well as the recent advances that led to the discoveries of the thousands of exoplanets now confirmed. UT Austin is involved in the future of the hunt for Earth 2.0, both at McDonald Observatory and as a partner in the forthcoming Giant Magellan Telescope, Armandroff said. “And in both places, we’re working to optimize the technology to participate strongly in this exoplanet revolution and to push the frontiers forward.”

Addressing a question about searching for or identifying life that is not carbon-based, Cochran said “What we’ve learned in looking at other planetary systems is that nature is way more clever than we are and has come up with more variety. So, yes, it’s very possible that there’s life out there that runs by a different mechanism,” she said, “but we don’t know what it is. So we can’t study it because our imaginations aren’t good enough — yet.”

Jaffe agreed, adding that “Astronomy is simple and yet we’ve been astounded by the complexity of the other [planetary] systems we find. Biology is complicated. And you can extrapolate from that and figure that things are going to be different and more complicated elsewhere.”

Asked about NASA’s changing decisions regarding funding a mission to Jupiter’s moon Europa, long thought a possible harbor for life, Grima noted that these things depend on politics. “The problem in the U.S. … is that once a mission is started, you have the possibility that year after year, government after government, the [politicians] might not want the mission, so they stop. The current U.S. Congress wants a Europa mission,” he said. “So far it’s going pretty good.”

When asked whether the next generation of large telescopes will be able to analyze the atmospheres of large extrasolar planets, Armandroff said they will. “But … we are moving from the era [of] 20 years ago, [when] the question was ‘Are there planets around other stars? How common are they?’ And astronomers have done a really great job with that. We know that planets are very common and Earth-mass planets are common. And now we’re moving into the realm where this spectroscopy that you asked about will give us much more information about the properties of planets, and greater physical insight into what’s happening on exoplanets.”

Several audience members expressed their enthusiasm for astronomy and their wish to understand more, and even to participate in a meaningful way in astronomical research. “I’m a basic person, and I’m amazed by all this stuff,” one woman said. “How can we become a part of what you’re doing?”

Cochran described the popular online platform Zooniverse that allows any interested person to help with research. “It’s used in the field of galaxies; it’s used in the field of exoplanets,” she explained. Datasets that would be “almost impossible for us to look through as astronomers,” are made available and can be searched by anyone after some online training. She noted that the Kepler exoplanet mission has benefited from public help in making some recent discoveries.

Reaching out to the public is important, Cochran said, “because the public are funding these missions. It’s very important to keep the public involved.” Jaffe added that keeping the public up-to-date on research is not only informational, but inspirational: “When you know that there are other planets around other stars, it changes your picture of your own existence and where you live,” he said. “We try to share with everyone what we know as soon as we know it, to expand people’s horizons, people’s view of our own place in the universe.”

To hear the panelists’ in-depth answers to all of the questions, and to find out what each panelists’ dream discovery would be, you can watch the one-hour video of the panel on our YouTube channel.

Spotlight

Brendan Bowler Wins Hubble Fellowship

Brendan Bowler

by Rebecca Johnson

AUSTIN — Astronomer Brendan Bowler of The University of Texas at Austin has been awarded a competitive Hubble Fellowship from NASA and the Space Telescope Science Institute (STScI), science center for the Hubble Space Telescope.

“I congratulate Brendan Bowler on winning one of the most prestigious fellowships in astronomy to continue his work at McDonald Observatory," said Taft Armandroff, the observatory’s director.

Hubble Fellows conduct research related to the mission of NASA’s Cosmic Origins Program, which aims to examine the origins of galaxies, stars, and planetary systems, and the evolution of these structures with cosmic time. Bowler studies various aspects of planetary systems.

“I like to boil it down to studying the origin, the atmospheres, and the architectures of giant planets orbiting other stars,” Bowler said. His three-year Hubble fellowship, which he will undertake at UT Austin, will fund his project “Probing the Origins of Giant Planets on Wide Orbits.” He will be looking at massive, Jupiter-sized planets that orbit their stars many times farther away than Jupiter does the Sun.

“How did they form, and how did they arrive there?” he asks. For this work, he will use many different tools, including the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory with its IGRINS instrument, and later, the Hobby-Eberly Telescope at McDonald.

"Hubble Fellows are the future leaders of our field, and these prestigious fellowships give them a wonderful opportunity to grow professionally and establish their credentials,” said STScI director Ken Sembach. “This impressive class of Fellows will surely make major contributions to astronomical research for years to come. Congratulations to all of them."

Bowler received his Ph.D. in astronomy from The University of Hawaii, followed by a postdoctoral fellowship at Caltech. For the past year, he has held a W.J. McDonald Prize Postdoctoral Fellowship with McDonald Observatory.

— END —

Science Contact:
Dr. Brendan Bowler
512-471-1402
The University of Texas at Austin

Featured Image

Close Encounters with Pluto through Alan Stern

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute and Anita Cochran

Composite Credit: NASA/JHUAPL/SwRI and Anita Cochran

by Marilyn Harris

On February 19, Alan Stern presented the work of NASA’s historic New Horizons mission to the Board of Visitors and other invited guests at the February Board of Visitors meeting dinner held at the Hyatt Regency in Austin.

Stern, who leads the New Horizons mission to Pluto and the Kuiper Belt, holds four degrees from UT Austin — including his B.S. in physics, B.A. in astronomy, and M.S. degrees in both aerospace and civil engineering.

New Horizons, the fastest spacecraft ever launched, left Earth in January of 2006, and changed the way scientists and the world see Pluto forever with amazing images that began arriving back to Earth in July of 2015. The flyby of another dwarf planet known as 2014 MU69 is planned for January 1, 2019.

Stern appears on Time magazine’s 2016 list of the 100 most influential people in the world. We were honored to witness the inside story of the New Horizons mission as well as more technical details of the exploration of Pluto during the Special Colloquium held earlier the same day.

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