James R. Graham
Encyclopedia
James R. Graham is an Irish
astrophysicist who works primarily in the fields of infrared astronomy
instrumention and adaptive optics
.
as his undergraduate major at Imperial College London
, graduated with a BSc
in 1982. He went on at Imperial College London to receive his PhD
in physics in 1985. After receiving his PhD, Graham first held a research position at Lawrence Berkeley Lab, followed by a position at the California Institute of Technology
. Since 1992, he has been a professor
of astronomy
at University of California, Berkeley
.
in the Pleiades
open cluster
, which was also one of the first important discoveries made using the Keck telescopes. In the preceding years, other claims of brown dwarf detections were made and then often retracted or disputed. Graham's team looked for the signature of lithium
absorption lines in the spectrum of the object. Lithium is quickly depleted in low mass star
s due to mixing that brings the lithium in to contact with the hydrogen
fusing
core. As brown dwarfs by definition lack hydrogen fusion, the presence of lithium in the atmosphere of a low mass object is either an indicator of extreme youth or the absence of fusion. As such, the abundance of lithium in the atmosphere of PPL 15, along with the estimated age of the stars in Pleaides, indicate that PPL 15 is a brown dwarf.
Graham was involved in another first in 2008, when he was a member of the team which announced the detection of Fomalhaut b
, the first exoplanet detected in visible light. Graham had first used the Hubble Space Telescope
to take images of the debris disk
around Fomalhaut
in 2004, and from the structure of the disk, he and his team inferred the presence of a planet. Follow-up observations of the disk showed that a tiny speck of light at the inner edge of the disk was moving in orbit about Fomalhaut, as predicted.
Currently, Graham is working to detect many more planets by direct imaging. Graham is the project scientist for the Gemini Planet Imager
, an extreme adaptive optics
instrument that is on schedule to begin operation in 2011 at the Gemini Observatory
in Chile
. Imaging extrasolar planets is complicated primarily by the overwhelming brightness of the host star as compared to the planet, which Graham likens to "seeing a firefly next to a searchlight," and the distortions
caused by random movement of air in the Earth
's atmosphere
. By using a coronagraph
and adaptive optics, Graham hopes to overcome both difficulties and discover many more planets by the light they emit, and in doing so, learn directly about the composition of extrasolar planets.
Irish people
The Irish people are an ethnic group who originate in Ireland, an island in northwestern Europe. Ireland has been populated for around 9,000 years , with the Irish people's earliest ancestors recorded having legends of being descended from groups such as the Nemedians, Fomorians, Fir Bolg, Tuatha...
astrophysicist who works primarily in the fields of infrared astronomy
Infrared astronomy
Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers...
instrumention and adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
.
Biography
Graham pursued physicsPhysics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
as his undergraduate major at Imperial College London
Imperial College London
Imperial College London is a public research university located in London, United Kingdom, specialising in science, engineering, business and medicine...
, graduated with a BSc
Bachelor of Science
A Bachelor of Science is an undergraduate academic degree awarded for completed courses that generally last three to five years .-Australia:In Australia, the BSc is a 3 year degree, offered from 1st year on...
in 1982. He went on at Imperial College London to receive his PhD
PHD
PHD may refer to:*Ph.D., a doctorate of philosophy*Ph.D. , a 1980s British group*PHD finger, a protein sequence*PHD Mountain Software, an outdoor clothing and equipment company*PhD Docbook renderer, an XML renderer...
in physics in 1985. After receiving his PhD, Graham first held a research position at Lawrence Berkeley Lab, followed by a position at the California Institute of Technology
California Institute of Technology
The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...
. Since 1992, he has been a professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
of astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
at University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
.
Research
In 1994, Graham was a member of a team which made one of the first definitive identifications of a brown dwarfBrown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
in the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...
open cluster
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
, which was also one of the first important discoveries made using the Keck telescopes. In the preceding years, other claims of brown dwarf detections were made and then often retracted or disputed. Graham's team looked for the signature of lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
absorption lines in the spectrum of the object. Lithium is quickly depleted in low mass star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s due to mixing that brings the lithium in to contact with the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
fusing
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
core. As brown dwarfs by definition lack hydrogen fusion, the presence of lithium in the atmosphere of a low mass object is either an indicator of extreme youth or the absence of fusion. As such, the abundance of lithium in the atmosphere of PPL 15, along with the estimated age of the stars in Pleaides, indicate that PPL 15 is a brown dwarf.
Fomalhaut b
Fomalhaut b is an extrasolar planet approximately 25 light-years away in the constellation of Piscis Austrinus. The planet was discovered orbiting the A-type main sequence star Fomalhaut in 2008 in photos taken by the Hubble Space Telescope...
, the first exoplanet detected in visible light. Graham had first used the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
to take images of the debris disk
Debris disk
A debris disk is a circumstellar disk of dust and debris in orbit around a star. Sometimes these disks contain prominent rings, as seen in the image of Fomalhaut on the right. Debris disks have been found around both evolved and young stars, as well as at least one debris disk in orbit around a...
around Fomalhaut
Fomalhaut
Fomalhaut is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in the sky. Fomalhaut can be seen low in the southern sky in the northern hemisphere in fall and early winter evenings. Near latitude 50˚N, it sets around the time Sirius rises, and does not...
in 2004, and from the structure of the disk, he and his team inferred the presence of a planet. Follow-up observations of the disk showed that a tiny speck of light at the inner edge of the disk was moving in orbit about Fomalhaut, as predicted.
Currently, Graham is working to detect many more planets by direct imaging. Graham is the project scientist for the Gemini Planet Imager
Gemini Planet Imager
The Gemini Planet Imager is a high contrast imaging instrument being built for the Gemini South Telescope in Chile. The instrument will achieve high contrast at small angular separations, allowing for the direct imaging and integral field spectroscopy of extrasolar planets around nearby stars...
, an extreme adaptive optics
Adaptive optics
Adaptive optics is a technology used to improve the performance of optical systems by reducing the effect of wavefront distortions. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, and in retinal imaging systems to reduce the...
instrument that is on schedule to begin operation in 2011 at the Gemini Observatory
Gemini Observatory
The Gemini Observatory is an astronomical observatory consisting of two telescopes at sites in Hawai‘i and Chile. Together, the twin Gemini telescopes provide almost complete coverage of both the northern and southern skies...
in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. Imaging extrasolar planets is complicated primarily by the overwhelming brightness of the host star as compared to the planet, which Graham likens to "seeing a firefly next to a searchlight," and the distortions
Astronomical seeing
Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by turbulent mixing in the Earth's atmosphere varying the optical refractive index...
caused by random movement of air in the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
. By using a coronagraph
Coronagraph
A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved...
and adaptive optics, Graham hopes to overcome both difficulties and discover many more planets by the light they emit, and in doing so, learn directly about the composition of extrasolar planets.
Honors
- Alfred P. SloanAlfred P. Sloan FoundationThe Alfred P. Sloan Foundation is a philanthropic non-profit organization in the United States. It was established in 1934 by Alfred P. Sloan, Jr., then-President and Chief Executive Officer of General Motors.-Overview:...
Fellow (1992) - PackardDavid and Lucile Packard FoundationThe David and Lucile Packard Foundation is a private foundation that provides grants to not-for-profit organizations. It was created in 1964 by David Packard and his wife Lucile Salter Packard. Following David Packard's death in 1996, the Foundation became the beneficiary of part of his estate...
Fellow (1993) - Noyce Prize for Excellence in Undergraduate Teaching (2007)
- Newcomb Cleveland PrizeNewcomb Cleveland PrizeThe Newcomb Cleveland Prize of the American Association for the Advancement of Science is annually awarded to author of outstanding scientific paper published in the Research Articles or Reports sections of Science...
of the American Association for the Advancement of ScienceAmerican Association for the Advancement of ScienceThe American Association for the Advancement of Science is an international non-profit organization with the stated goals of promoting cooperation among scientists, defending scientific freedom, encouraging scientific responsibility, and supporting scientific education and science outreach for the...
(2009)