April 06, 2016
Gene Stowe
A team led by Justin Crepp has discovered HD 4747 B, a rare brown dwarf. As a new mass, age and metallicity benchmark, HD 4747 B will serve as a laboratory for precision astrophysics to test theoretical models.
A team led by Justin Crepp, the Frank M. Freimann Assistant Professor of Physics at the University of Notre Dame, has discovered a rare brown dwarf, a faint object with properties in between that of a star and planet.
![Artist's concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech](https://sciencesprings.files.wordpress.com/2016/02/brown-dwarf.jpg?w=1100)
Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech
In addition to taking its picture for the first time, Crepp’s team also determined the brown dwarf’s mass, age and composition — essential information that can be used to “benchmark” the study of these elusive objects.
Brown dwarfs are objects thought to have initially begun the process of forming a star but were somehow interrupted before they accumulated sufficient mass and core pressure to ignite nuclear fusion — the process by which the Sun ultimately releases energy in the form of light. An important developmental bridge between bona fide stars and exoplanets, brown dwarfs are very difficult to study because their faint glow fades with time due to a lack of sustained nuclear reactions. The discovery of the object, which goes by the name HD 4747 B, was facilitated by 18 years of precise spectral measurements of the star that indicated it hosts an orbiting companion.
“We suspect that these companions form at the same time and from the same material,” Crepp said. “As such, you can infer physical properties of the brown dwarf from its parent star, like age and composition. There are no other objects for which we know the mass, age and the metallicity simultaneously and also independent of the light that the companion gives off. We can therefore use HD 4747 B as a test-bed to study brown dwarfs, enabling precision astrophysics studies for a directly imaged substellar object.”
In the past, brown dwarf masses have been estimated using theoretical evolutionary models. Crepp’s team instead calculated the mass of HD 4747 B directly using observations of its orbit in an attempt to help refine brown dwarf models. It is expected that this work will in turn help to inform models for extrasolar planets. Based on a three-dimensional orbit analysis, HD 4747 B has a mass of about 60 Jupiters (a mass of 80 Jupiters is required to ignite nuclear fusion), well below the theoretical estimate of 72 Jupiters, although still within uncertainties. Forthcoming measurements acquired by Crepp’s team will provide yet more stringent tests of the models used by astronomers for brown dwarfs.
“This field is transitioning from ‘Hey, I found something neat’ to ‘Hey, I know the mass to within a few percent.’ Now, we can test theoretical models,” Crepp said.
The team detected the object using the Keck telescopes in Hawaii, and published their results in a paper describing the discovery.
Keck Observatory, Mauna Kea, Hawaii, USA
The study has been submitted to the Astrophysical Journal. Co-authors of the study include Erica Gonzales and Eric Bechter, both in the Department of Physics at the University of Notre Dame; Benjamin Montet at the Harvard-Smithsonian Center for Astrophysics and the California Institute of Technology; John Asher Johnson at the Harvard-Smithsonian Center for Astrophysics; Danielle Piskorz at the Division of Geological and Planetary Sciences at the California Institute of Technology; Andrew Howard at the Institute for Astronomy at the University of Hawaii; and Howard Isaacson at the University of California Berkeley.
Science paper:
The TRENDS High-Contrast Imaging Survey. VI. Discovery of a Mass, Age, and Metallicity Benchmark Brown Dwarf
Science team:
Justin R. Crepp 1, Erica J. Gonzales 1, Eric B. Bechter 1, Benjamin T. Montet 2,3, John Asher
Johnson 2, Danielle Piskorz 3, Andrew W. Howard 4, Howard Isaacson 5
Affiliations:
1 Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN, 46556, USA
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
3 Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125
4 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822
5 Department of Astronomy, University of California, Berkeley, CA 94720
See the full article here .
Please help promote STEM in your local schools.
The University of Notre Dame du Lac (or simply Notre Dame /ˌnoʊtərˈdeɪm/ NOH-tər-DAYM) is a Catholic research university located near South Bend, Indiana, in the United States. In French, Notre Dame du Lac means “Our Lady of the Lake” and refers to the university’s patron saint, the Virgin Mary.
The school was founded by Father Edward Sorin, CSC, who was also its first president. Today, many Holy Cross priests continue to work for the university, including as its president. It was established as an all-male institution on November 26, 1842, on land donated by the Bishop of Vincennes. The university first enrolled women undergraduates in 1972. As of 2013 about 48 percent of the student body was female.[6] Notre Dame’s Catholic character is reflected in its explicit commitment to the Catholic faith, numerous ministries funded by the school, and the architecture around campus. The university is consistently ranked one of the top universities in the United States and as a major global university.
The university today is organized into five colleges and one professional school, and its graduate program has 15 master’s and 26 doctoral degree programs.[7][8] Over 80% of the university’s 8,000 undergraduates live on campus in one of 29 single-sex residence halls, each of which fields teams for more than a dozen intramural sports, and the university counts approximately 120,000 alumni.[9]
The university is globally recognized for its Notre Dame School of Architecture, a faculty that teaches (pre-modernist) traditional and classical architecture and urban planning (e.g. following the principles of New Urbanism and New Classical Architecture).[10] It also awards the renowned annual Driehaus Architecture Prize.
sciencesprings 