Scientists have conducted the first lab experiments on haze formation in simulated exoplanet atmospheres, an important step for understanding upcoming observations of planets outside the solar system with the James Webb Space Telescope.

The simulations are necessary to establish models of the atmospheres of far-distant worlds, models that can be used to look for signs of life outside the solar system. Results of the study appeared recently in Nature Astronomy.

“One of the reasons why we’re starting to do this work is to understand if having a haze layer on these planets would make them more or less habitable,” says the paper’s lead author, Sarah Hörst, assistant professor in the Krieger School’s Department of Earth and Planetary Sciences.

With telescopes available today, planetary scientists and astronomers can learn what gases make up the atmospheres of exoplanets.

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“Each gas has a fingerprint that’s unique to it,” says Hörst. “If you measure a large enough spectral range, you can look at how all the fingerprints are superimposed on top of each other.”

Current telescopes, however, do not work as well with every type of exoplanet. They fall short with exoplanets that have hazy atmospheres. Haze consists of solid particles suspended in gas, altering the way light interacts with the gas. This muting of spectral fingerprints makes measuring the gas composition more challenging.

Hörst believes this research can help the exoplanet science community determine which types of atmospheres are likely to be hazy. With haze clouding up a telescope’s ability to tell scientists which gases make up an exoplanet’s atmosphere—if not the amounts of them—our ability to detect life elsewhere is a murkier prospect.

Planets larger than Earth and smaller than Neptune, called super-Earths and mini-Neptunes, are the predominant types of exoplanets, or planets outside our solar system. As this class of planets is not found in our solar system, our limited knowledge makes them more difficult to study.

With the launch of the James Webb Space Telescope scheduled for 2020 (see p. 34), scientists hope to be able to examine the atmospheres of these exoplanets in greater detail. JWST will be capable of looking back even further in time than the Hubble Space Telescope can, with a light-collecting area around 6.25 times greater than Hubble’s. Orbiting around the Sun a million miles from Earth, JWST will help researchers measure the composition of extrasolar planet atmospheres and even search for the building blocks of life.

“Part of what we’re trying to help people figure out is basically where you would want to look,” says Hörst of future uses of the James Webb Space Telescope.

Given that our solar system has no super-Earths or mini-Neptunes for comparison, scientists don’t have “ground truths” for the atmospheres of these exoplanets. Using computer models, Hörst’s team was able to put together a series of atmospheric compositions that model super-Earths or mini-Neptunes. They assembled nine different “planets” by varying levels of three dominant gases: carbon dioxide, hydrogen, and gaseous water; four other gases: helium, carbon monoxide, methane, and nitrogen; and three sets of temperatures.

The computer modeling proposed different percentages of gases, which the scientists mixed in a chamber and heated. Over three days, the heated mixture flowed through a plasma discharge, a setup that initiated chemical reactions within the chamber.

“The energy breaks up the gas molecules that we start with. They react with each other and make new things, and sometimes they’ll make a solid particle [creating haze] and sometimes they won’t,” Hörst says.

She added: “The fundamental question for this paper was: Which of these gas mixtures—which of these atmospheres—will we expect to be hazy?”

The researchers found that all nine variants made haze in varying amounts. The surprise lay in which combinations made more. The team found the most haze particles in two of the water-dominant atmospheres.

“We had this idea for a long time that methane chemistry was the one true path to make a haze, and we know that’s not true now,” says Hörst, referring to compounds abundant in both hydrogen and carbon.

Furthermore, the scientists found differences in the colors of the particles, which could affect how much heat is trapped by the haze.

“Having a haze layer can change the temperature structure of an atmosphere,” Hörst says. “It can prevent really energetic photons from reaching a surface.”

Like the ozone layer that now protects life on Earth from harmful radiation, scientists have speculated a primitive haze layer may have shielded life in the very beginning. This could be meaningful in the search for external life.

For Hörst’s group, the next steps involve analyzing the different hazes to see how the color and size of the particles affect how the particles interact with light. They also plan to try other compositions, temperatures, and energy sources to examine the composition of the haze produced.

“The production rates were the very, very first step of what’s going to be a long process in trying to figure out which atmospheres are hazy and what the impact of the haze particles is,” Hörst says.

Legendary investor William H. “Bill” Miller III has committed a record $75 million to the Krieger School’s Department of Philosophy to broaden and intensify faculty research, graduate student support, and undergraduate study of philosophical thought.

Miller, founder and chairman of Miller Value Partners and formerly the longtime, highly successful manager of the Legg Mason Capital Management Value Trust, is himself a former Johns Hopkins philosophy graduate student.

“I attribute much of my business success to the analytical training and habits of mind that were developed when I was a graduate student at Johns Hopkins,” says Miller, who is best known for beating the Standard & Poor’s 500 with his Legg Mason fund for a record 15 consecutive years, from 1991 to 2005.

“I am delighted to be able to show my gratitude by helping to move the department to its rightful place among the best in the country,” he says.

Ronald J. Daniels, president of Johns Hopkins University, says Miller’s aim—and the university’s—is to set a new standard for excellence in philosophy and promote powerful, change-making collaboration between philosophers and other scholars.

“Philosophy matters,” Daniels says. “Philosophy defines what it is to be human, to lead lives that are meaningful, and to create societies that are just and humane. The contemporary challenges of the genomics revolution, the rise of artificial intelligence, the growth in income inequality, social and political fragmentation, and our capacity for devastating war all invite philosophical perspective. Bill Miller’s unprecedented commitment to our Department of Philosophy underscores the continuing vitality and relevance of the humanities.”

The university is recognizing Miller’s generosity by renaming the department in his honor.

“Bill’s dual perspective as a business leader and an intellectually curious lifelong student of philosophy is so important,” says Beverly Wendland, dean of the Krieger School. “Our talented faculty and the students who will study in the William H. Miller Department of Philosophy for generations to come will always be grateful, as I am, for Bill’s confidence in Johns Hopkins.”

Miller’s gift will help grow the department within 10 years to 22 full-time faculty members from its current 13. It will create an endowed professorship for the chair of the department, eight other endowed professorships,and endowed support for junior faculty members.

The gift will add $10 million to endowed support for philosophy graduate students and postdoctoral fellows. The university also aims to attract more undergraduates to the study of philosophy, in part through new introductory courses and additional interdisciplinary tracks.

“The study of philosophy has been central to Johns Hopkins from the university’s beginning in 1876,” says Richard Bett, professor and chair of the department. “Bill Miller knows that every student, no matter their major or intended career, can benefit from philosophical study.”

A new measurement recently reported in Nature provides evidence for a new cooling property of dark matter previously posited by a collection of JHU professors, postdoctoral fellows, and students.

The paper, authored by a group of radio-astronomers at Arizona State University, describes the first measurement of the temperature of intergalactic hydrogen atoms from only 180 million years after the Big Bang.

Surprisingly, that temperature reading is colder than expected in the standard cosmological model. An interpretation paper by a researcher at Tel Aviv University explains that this result can be understood if these hydrogen atoms have some small heat exchange with the abundant dark matter in the universe. If this result is correct, it tells us something new about the physics of dark matter: Not only does dark matter have a gravitational pull that prevents galaxies from flying apart, it also has the ability to absorb heat energy.

The theoretical research that suggested hydrogen might be cooled by dark matter, and thus produce the signal reported in Nature, was conducted at the Krieger School of Arts and Sciences.

The initial paper exploring the possibility of heat exchange between hydrogen and dark matter was authored in 2013 by Marc Kamionkowski, the William R. Kenan Professor and a theoretical physicist in the Department of Physics and Astronomy, and two of his collaborators. Two subsequent papers elaborated further this heat exchange and proposed to seek evidence for it in precisely the type of measurements reported in Nature. One of these papers was authored by Joseph Silk, a research professor in the department, and his collaborators; the other paper was written by JHU postdocs Yacine Ali-Haïmoud and Ely Kovetz and a graduate student, Julián Munoz.

“This newly reported result, if confirmed by subsequent measurements, may well turn out to be a Rosetta stone for the nature of dark matter,” Kamionkowski said. “Joe and his collaborators, and Julian, Ely, and Yacine, deserve significant credit for suggesting these neutral-hydrogen measurements could be used in this way.”

Vesla Weaver, a leading scholar on racial politics and criminal justice issues in America, joined Johns Hopkins last fall as a Bloomberg Distinguished Associate Professor in political science and sociology. She is perhaps best known as a leader in the movement to push the social sciences to understand punishment as a crucial site of governance in the U.S., as well as a forceful mechanism of racial inequity. With her research, she has informed one of the central questions facing policymakers today: how to grapple with the consequences of nearly four decades of state-enforced discipline for citizens and communities.

In the early years of her graduate studies at Harvard, Weaver bucked against the common thinking that punishment was not a core concern for political science, successfully arguing that incarceration and surveillance influenced America’s post-war institutions in ways that critically altered the racial politics and inequality of later decades.

Later, as a professor at Yale, Weaver embarked on the first large-scale empirical study of how seismic shifts in incarceration and policing shaped the political and civic realities in the communities most affected.

Weaver received her undergraduate degree in government studies from the University of Virginia. She earned a doctoral degree in government and social policy from Harvard, where she also worked on the university’s Civil Rights Project.

In 2012, Weaver became a tenured associate professor in African-American studies and political science at Yale.