Gibor Basri | |
|---|---|
 |
Gibor Basri is an American astrophysicist, now Professor Emeritus in the Astronomy department at U.C. Berkeley. His research focused on stellar magnetic activity, star formation, and low mass stars and brown dwarfs. He was also the founding Vice Chancellor for Equity & Inclusion at UC Berkeley.
Gibor Basri was born in New York City on May 3, 1951, the son of Saul Basri, professor of physics at the University of Colorado, and Phyllis Basri, a teacher of modern dance and ballet. His father was an Iraqi Jew who grew up in Basra and Baghdad and came to MIT in 1944, remaining in America since then. His mother was Jamaican, and came to New York just before WWII to study dance (she was in Martha Graham's troupe for a little while). They met while both graduate students at Columbia University. Gibor grew up in Fort Collins, Colorado, together with his younger brother David. The family lived for brief periods in Burma (1957) and Sri Lanka (1965). [1] In 1974 he met his wife Jessica Broitman, who became a psychoanalyst and learning disability specialist. Their son was born in 1991.[ citation needed ]
Basri graduated in physics at Stanford University in 1973, and received his Ph.D. in astrophysics at the University of Colorado in 1979. His thesis, under the supervision of Jeffrey Linsky, was on radiative transfer theory and stellar activity. It was partially based on observations by the International Ultraviolet Explorer (IUE) satellite, of which Linsky's group was one of the first users. A postdoctoral award took him to the U.C. Berkeley astronomy department in 1979. In 1982 he joined the faculty of the Astronomy Department where he has been ever since, becoming a full professor in 1994 and formally retiring in 2015 (though he remains active). GB was awarded a Miller Research Professorship in 1997, and became a Sigma Xi Distinguished Lecturer in 2000. He held a NASA Faculty Fellowship in 2002 and became a Fellow of the California Academy of Science in 2011. Awards from the Berkeley campus include the Chancellor's Award for Increasing Institutional Excellence in 2005 and the Berkeley Citation (highest honor) in 2015. He was the recipient of the Carl Sagan Prize for Science Popularization in 2016. In 2023 he was elected a Fellow of the American Astronomical Society.
His work there originally focused on high-energy observations of stars (with Stuart Bowyer) in preparation for the eventual launch of the Extreme Ultraviolet Explorer (EUVE). In the 1980s, he turned to studies of star formation and the study of T Tauri stars as well as continuing investigations into stellar magnetic activity. In the 1990s he was one of the discoverers of brown dwarfs (substellar objects) and became recognized as a world expert on them. As part of that work he invented the method of “lithium dating” that revised the ages of young star clusters upward by 50% or more. These discoveries are described in the book 50 Years of Brown Dwarfs. [2] He was also lead author on the article Brown Dwarfs to Planetesimals: What is a Planet? [3] with Michael Brown. In the 2000s he became a Co-Investigator on NASA's Kepler Mission. He used the precision light curves available for large numbers of stars to study the behavior of starspots and learn more about stellar magnetic activity, In 2022 he published a technical book An Introduction to Stellar Magnetic Fields. [4]
Basri's extensive work on diversifying the academy (and STEM disciplines in particular is summarized here [5] ). He was hired by Robert Birgeneau (Chancellor) as the founding Vice Chancellor for Equity and Inclusion for the U.C. Berkeley campus from 2007 to 2015. [6] He led the campus to a strategic plan for equity and inclusion, [7] played a key role in a number of climate surveys (culminating in one for the whole University of California system [8] ), and brought diversity considerations to a stronger role in hiring and search practices, advancement and retention practices, and programmatic review for the campus.
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2H). The most massive ones can fuse lithium (7Li).
Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in general much larger than those on the Sun: up to about 30% of the stellar surface may be covered, corresponding to starspots 100 times larger than those on the Sun.
Ross 154 is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44, making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of 6.5 cm (3 in) under ideal conditions. The distance to this star can be estimated from parallax measurements, which places it at 9.71 light-years away from Earth. It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.
Groombridge 34 is a binary star system in the northern constellation of Andromeda. It was listed as entry number 34 in A Catalogue of Circumpolar Stars, published posthumously in 1838 by British astronomer Stephen Groombridge. Based upon parallax measurements taken by the Gaia spacecraft, the system is located about 11.6 light-years from the Sun. This positions the pair among the nearest stars to the Solar System.
DX Cancri is a variable star in the northern zodiac constellation of Cancer. With an apparent visual magnitude of 14.81, it is much too faint to be seen with the naked eye. Visually viewing this star requires a telescope with a minimum aperture of 16 in (41 cm). Based upon parallax measurements, DX Cancri is located at a distance of 11.8 light-years from Earth. This makes it the 18th closest star to the Sun.
LHS 292 is a red dwarf in the constellation Sextans. It is far too faint to be seen with the unaided eye and requires a large amateur telescope to be seen visually. It lies relatively close to the Solar System at a distance of about 14.9 light years. It is a flare star, which means it can suddenly increase in brightness for short periods of time.
Sigma Boötis, its name Latinized from σ Boötis, is a single star in the northern constellation of Boötes. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude of 4.46. Located to the southeast of Rho Boötis, the dwarf Sigma may at first appear as a naked-eye double, but the angular proximity with Rho is merely line-of-sight. Sigma Boötis is located at a distance of 51.1 light years from the Sun based on parallax. The star has a relatively high proper motion and is traversing the sky at the rate of 0.230″ yr−1.
AD Leonis (Gliese 388) is a red dwarf star. It is located relatively near the Sun, at a distance of 16.2 light-years, in the constellation Leo. AD Leonis is a main sequence star with a spectral classification of M3.5V. It is a flare star that undergoes random increases in luminosity.
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a planetary mass, therefore by definition below the limiting mass for thermonuclear fusion of deuterium . Some researchers call them rogue planets whereas others call them planetary-mass brown dwarfs. They are sometimes categorized as Y spectral class brown dwarfs.
Sigma Orionis or Sigma Ori is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates. The combined brightness of the component stars is magnitude 3.80.
LP 944-20 is a dim brown dwarf of spectral class M9 located 21 light-years from the Solar System in the constellation of Fornax. With a visual apparent magnitude of 18.69, it has one of the dimmest visual magnitudes listed on the RECONS page. It is one of the brightest brown dwarfs, if not the brightest at JMKO=10.68±0.03 mag.
HR 6806 or HD 166620 is a solitary, orange, main sequence, and Sun-like star located thirty-six light-years away, in the constellation Hercules. The star is smaller than the Sun, with around 79% of the solar mass and radius, and 35% of the solar luminosity. It appears to be rotating slowly with an estimated period of 42 days. In 1988, it was noticed that the star had an inactive chromosphere, with a surface magnetic field strength of only 1,500 G. From 1990 activity in the chromosphere increased, inline with a 16 year stellar cycle previously observed. But, sometime after 1994 chromospheric activity greatly reduced, and has stayed flat for more than 16 years. As of 2022, the star appears to have entered the equivalent of a Maunder minimum. The star is around six billion years of age.
GJ 3379 is the nearest star in the Orion constellation, located at a distance of 17 light years from the Sun based on parallax. It is a single star with an apparent visual magnitude of +11.31 and an absolute magnitude of +12.71, therefore, the star is not visible with the naked eye. It is positioned in the upper left part of the Orion constellation, to the SSE of Betelgeuse. This star is drifting further away with a radial velocity of +30.0 kilometers per second. In the past, this star had a relatively close encounter with the Solar System. Some 161,000±6,000 years ago, it achieved a minimum distance of 4.08 ± 0.20 ly (1.25 ± 0.06 pc).
LSR J1835+3259 is a nearby ultracool dwarf of spectral class M8.5, located in constellation Lyra, the discovery of which was published in 2003. Previously it was concluded that this star is a young brown dwarf, but no lithium absorption lines are detected for this object, which is a strong indicator for young brown dwarfs that need 10-100 million years to deplete lithium.
HD 79498 is a double star in the northern constellation of Cancer. The primary component of this pair has an orbiting exoplanet companion. This star is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.05. The system is located at a distance of 159 light years based on parallax measurements, and is drifting further away with a heliocentric radial velocity of 20 km/s. It has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.2″·yr−1.
2MASS J0523−1403 is a very-low-mass red dwarf or high-mass brown dwarf about 40 light-years from Earth in the southern constellation of Lepus, with a very faint visual magnitude of 21.05 and a low effective temperature of 2074 K. It is visible primarily in large telescopes sensitive to infrared light. 2MASS J0523−1403 was first observed as part of the Two Micron All-Sky Survey (2MASS).
LP 71-82 is a red dwarf star, located in constellation Draco at 25.42 light-years from Earth. Kinematically, it is probably belongs to the Ursa Major Moving Group.
GL Virginis, also known as G 12-30, is a star in the constellation of Virgo. It is a faint red dwarf, like more than 70% of the stars located within 10 parsecs of the Solar System; its magnitude visual magnitude is 13.898, making it impossible to see with the naked eye.
HD 2454 is a probable binary star system in the zodiac constellation of Pisces. With an apparent visual magnitude of 6.04, it is near the lower limit of visibility to the naked eye under good seeing conditions. An annual parallax shift of 26.3 mas as measured from Earth's orbit provides a distance estimate of 124 light years. It has a relatively high proper motion, traversing the celestial sphere at a rate of 0.208 arcseconds per year, and is moving closer to the Sun with a heliocentric radial velocity of −10 km/s.
{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link){{cite book}}: CS1 maint: location missing publisher (link)| International | |
|---|---|
| National | |
| Academics | |
| Other | |
