Planet-sized object as cool as Earth revealed in record-breaking photo

ScienceDaily (Oct. 19, 2011) — The photo of a nearby star and its orbiting companion -- whose temperature is like a hot summer day in Arizona -- will be presented by Penn State Associate Professor of Astronomy and Astrophysics Kevin Luhman during the Signposts of Planets conference at NASA's Goddard Space Flight Center on Oct. 20, 2011.

A paper describing the discovery will be published in the Astrophysical Journal.

"This planet-like companion is the coldest object ever directly photographed outside our solar system," said Luhman, who led the discovery team. "Its mass is about the same as many of the known extra-solar planets -- about six to nine times the mass of Jupiter -- but in other ways it is more like a star. Essentially, what we have found is a very small star with an atmospheric temperature about cool as the Earth's."

Luhman classifies this object as a "brown dwarf," an object that formed just like a star out of a massive cloud of dust and gas. But the mass that a brown dwarf accumulates is not enough to ignite thermonuclear reactions in its core, resulting in a failed star that is very cool. In the case of the new brown dwarf, the scientists have gauged the temperature of its surface to be between 80 and 160 degrees Fahrenheit -- possibly as cool as a human.

Ever since brown dwarfs first were discovered in 1995, astronomers have been trying to find new record holders for the coldest brown dwarfs because these objects are valuable as laboratories for studying the atmospheres of planets with Earth-like temperatures outside our solar system.

Astronomers have named the brown dwarf "WD 0806-661 B" because it is the orbiting companion of an object named "WD 0806-661" -- the "white dwarf" core of a star that was like the Sun until its outer layers were expelled into space during the final phase of its evolution. "The distance of this white dwarf from the Sun is 63 light years, which is very near our solar system compared with most stars in our galaxy," Luhman said.

"The distance of this white dwarf from its brown-dwarf companion is 2500 astronomical units (AU) -- about 2500 times the distance between the Earth and the Sun, so its orbit is very large as compared with the orbits of planets, which form within a disk of dust swirling close around a newborn star," said Adam Burgasser at the University of California, San Diego, a member of the discovery team. Because it has such a large orbit, the astronomers say this companion most probably was born in the same manner as binary stars, which are known to be separated as far apart as this pair, while remaining gravitationally bound to each other.

Luhman and his colleagues presented this new candidate for the coldest known brown dwarf in a paper published in spring 2011, and they now have confirmed its record-setting cool temperature in a new paper that will be published in the Astrophysical Journal.

To make their discovery, Luhman and his colleagues searched through infrared images of over six hundred stars near our solar system. They compared images of nearby stars taken a few years apart, searching for any faint points of light that showed the same motion across the sky as the targeted star. "Objects with cool temperatures like the Earth are brightest at infrared wavelengths," Luhman said. "We used NASA's Spitzer Space Telescope because it is the most sensitive infrared telescope available."

Luhman and his team discovered the brown dwarf WD 0806-661 B moving in tandem with the white dwarf WD 0806-661 in two Spitzer images taken in 2004 and 2009. The images, which together show the movement of the objects, are available online (http://science.psu.edu/alert/photos/research-photos/astro/Luhman-moving-labels.gif). "This animation is a fun illustration of our technique because it resembles the method used to discovery Pluto in our own solar system," Luhman said.

In a related new discovery involving a different cool brown dwarf, Penn State Postdoctoral Scholar John Bochanski and his colleagues have made the most detailed measurement yet of ammonia in the atmosphere of an object outside our solar system. "These new data are much higher quality that previously achieved, making it possible to study, in much more detail than ever before, the atmospheres of the coldest brown dwarfs, which most closely resemble the atmospheres that are possible around planets," Bochanski said.

"Brown dwarfs that are far from their companion stars are much easier to study than are planets, which typically are difficult to observe because they get lost in the glare of the stars they orbit," Burgasser said. "Brown dwarfs with Earth-like temperatures allow us to refine theories about the atmospheres of objects outside our solar system that have comparatively cool atmospheres like that of our own planet."

This research was sponsored by grants from the National Science Foundation and the NASA Astrophysics Theory Program.

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Hot springs microbe yields record-breaking, heat-tolerant enzyme

ScienceDaily (July 5, 2011) — Bioprospectors from the University of California, Berkeley, and the University of Maryland School of Medicine have found a microbe in a Nevada hot spring that happily eats plant material -- cellulose -- at temperatures near the boiling point of water.

In fact, the microbe's cellulose-digesting enzyme, called a cellulase, is most active at a record 109 degrees Celsius (228 degrees Fahrenheit), significantly above the 100oC (212oF) boiling point of water.

This so-called hyperthermophilic microbe, discovered in a 95oC (203oF) geothermal pool, is only the second member of the ancient group Archaea known to grow by digesting cellulose above 80oC. And the microbe's cellulase is the most heat tolerant enzyme found in any cellulose-digesting microbe, including bacteria.

"These are the most thermophilic Archaea discovered that will grow on cellulose and the most thermophilic cellulase in any organism," said coauthor Douglas S. Clark, UC Berkeley professor of chemical and biomolecular engineering. "We were surprised to find this bug in our first sample."

Clark and coworkers at UC Berkeley are teaming with colleagues, led by Frank T. Robb, at the University of Maryland (U-Md) School of Medicine in Baltimore, to analyze microbes scooped from hot springs and other extreme environments around the United States in search of new enzymes that can be used in extreme industrial processes, including the production of biofuels from hard-to-digest plant fiber. Their team is supported by a grant from the Energy Biosciences Institute (EBI), a public-private collaboration that includes UC Berkeley, in which bioscience and biological techniques are being applied to help solve the global energy challenge.

"Our hope is that this example and examples from other organisms found in extreme environments -- such as high-temperature, highly alkaline or acidic, or high salt environments -- can provide cellulases that will show improved function under conditions typically found in industrial applications, including the production of biofuels," Clark said.

Clark, Robb and their colleagues, including UC Berkeley professor Harvey W. Blanch and postdoctoral researcher Melinda E. Clark, and U-Md postdoctoral researcher Joel E. Graham, will publish their results on July 5, in the online-only journal Nature Communications.

Many industrial processes employ natural enzymes, some of them isolated from organisms that live in extreme environments, such as hot springs. The enzyme used in the popular polymerase chain reaction to amplify DNA originally came from a thermophilic organism found in a geyser in Yellowstone National Park.

But many of these enzymes are not optimized for industrial processes, Clark said. For example, a fungal enzyme is currently used to break down tough plant cellulose into its constituent sugars so that the sugars can be fermented by yeast into alcohol. But the enzyme's preferred temperature is about 50oC (122oF), and it is not stable at the higher temperatures desirable to prevent other microbes from contaminating the reaction.

Hence the need to look in extreme environments for better enzymes, he said.

"This discovery is interesting because it helps define the range of natural conditions under which cellulolytic organisms exist and how prevalent these bugs are in the natural world," Clark said. "It indicates that there are a lot of potentially useful cellulases in places we haven't looked yet."

Robb and his colleagues collected sediment and water samples from the 95oC (203oF) Great Boiling Springs near the town of Gerlach in northern Nevada and grew microbes on pulverized Miscanthus gigas, a common biofuel feedstock, to isolate those that could grow with plant fiber as their only source of carbon.

After further growth on microcrystalline cellulose, the U-Md and UC Berkeley labs worked together to sequence the community of surviving microbes to obtain a metagenome, which indicated that three different species of Archaea were able to utilize cellulose as food. Using genetic techniques, they plucked out the specific genes involved in cellulose degradation, and linked the most active high-temperature cellulase, dubbed EBI-244, to the most abundant of the three Archaea.

Based on the structure of the enzyme, "this could represent a new type of cellulase or a very unusual member of a previously known family," Clark said.

The enzyme is so stable that it works in hot solutions approaching conditions that could be used to pretreat feedstocks like Miscanthus to break down the lignocelluloses and liberate cellulose. This suggests that cellulases may someday be used in the same reaction vessel in which feedstocks are pretreated.

The newly discovered hyperthermophilic cellulase may actually work at too high a temperature for some processes, Clark said. By collecting more hyperthermophilic cellulases, protein engineers may be able to create a version of the enzyme optimized to work at a lower temperature, but with the robust structural stability of the wild microbe.

"We might even find a cellulase that could be used as-is," he said, "but at least they will give us information to engineer new cellulases, and a better understanding of the diversity of nature."

The EBI partnership, which is funded with $500 million for 10 years from the energy company BP, includes researchers from the UC Berkeley; the University of Illinois at Urbana-Champaign; and the Lawrence Berkeley National Laboratory.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Berkeley.

Journal Reference:

Joel E. Graham, Melinda E. Clark, Dana C. Nadler, Sarah Huffer, Harshal A. Chokhawala, Sara E. Rowland, Harvey W. Blanch, Douglas S. Clark, Frank T. Robb. Identification and characterization of a multidomain hyperthermophilic cellulase from an archaeal enrichment. Nature Communications, 2011; 2: 375 DOI: 10.1038/ncomms1373

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