Josh Simon uses observations of nearby galaxies to study problems related to dark matter, chemical evolution, star formation, and the process of galaxy evolution.

In one area he looks at peculiarly dark galaxies. Interestingly, some galaxies are so dark they glow with the light of just a few hundred Suns. Simon and colleagues have determined that a tiny, very dim galaxy orbiting the Milky Way, called Segue 1, is the darkest galaxy ever found and has the highest dark matter density ever found. His team has also laid to rest a debate about whether Segue 1 really is a galaxy or a globular cluster—a smaller group of stars that lacks dark matter. Their findings make Segue 1 a promising laboratory to study dark matter, particularly the possibility that dark matter could be seen for the first time via a detection of gamma rays emanating from colliding dark matter particles.

Dark matter is the mysterious nonluminous material that makes up about most of the universe.  Dark energy is a mysterious repulsive force. Together they make up  about 95% of the universe. The rest--all observable matter--adds up to less than 5% of the universe.  Nearby dwarf galaxies have the highest measured densities of dark matter, making them ideal for dark matter studies, but that proximity also has a downside. Star systems so close to the massive Milky Way are subject to the acceleration of their stars by our galaxy’s tidal forces, an effect that can mimic the presence of dark matter. The lack of bright stars in dim dwarfs also makes it difficult to measure the velocities of enough stars for sufficient certainty. Simon and company overcame these hurdles with a comprehensive program that measured and analyzed the speed and chemistry of 397 stars in the vicinity of Segue 1.

 A major difference between galaxies and globular clusters--spherical collections of stars that are gravitationally bound--is that the stars in galaxies contain widely varying amounts of iron and other heavy elements, while stars in clusters do not. The new observations revealed that some Segue 1 stars have 50 times less iron than others in the galaxy, demonstrating conclusively that Segue 1 cannot be a globular cluster.

In collaboration with astronomers, Simon also showed that the high speeds of the Segue 1 stars are not caused by invisible binary companion stars, firming up the estimates of the amount of dark matter in the galaxy. Ongoing observations with NASA’s Fermi Gamma-ray Space Telescope are searching for signals from Segue 1 and other dwarfs, which would provide astronomers with concrete proof that their dark matter theories are on the right track\

Simon received his B.S. in physics from Stanford University and his M.A. and Ph. D. in astrophysics from UC-Berkeley. He was a postdoctoral scholar at Caltech from 2005-2008 and  the Vera Rubin Fellow at Carnegie from  2008 to 2010. For more information see http://obs.carnegiescience.edu/users/jsimon

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Kit Whitten in the plate analysis room. Photo by Cynthia Hunt
May 3, 2018

Cataloging Reflections by Kit Whitten, Carnegie Observatories Library Intern

It is commonly believed that when looking for valuable treasure, the best place to look is the attic—after all, works by Caravaggio, Van Gogh, Rembrandt, and Jackson Pollack have been discovered in attics—but not everyone thinks to look in the basement. Yet institutions like Carnegie Observatories often keep the best stuff in the basement.

The underground vault at the Observatories houses the nation’s second-largest, single-institution collection of astronomical glass plates, which are thin sheets of glass with an emulsion image of celestial bodies.  Photographic plates preceded plastic

April 27, 2018

Former Carnegie fellow and current trustee Sandy Faber has been selected to receive the 2018 American Philosophical Society’s Magellanic Premium Medal.  The medal is the nation’s oldest for scientific achievement. It was established in 1786. It is awarded from time to time “ to the author of the best discovery or most useful invention related to navigation, astronomy, or natural philosophy…”

Dr. Faber is the University of California, Santa Cruz, University Professor of Astronomy and Astrophysics and has been a Carnegie trustee since 1985.  After receiving a B.A. in physics from Swarthmore College, she pursued her Ph.D. in astronomy at Harvard, which she received in 1972. Much of

April 5, 2018

Pasadena, CA—Pomona College junior and returning Carnegie Observatories intern Sal Fu was awarded a Barry M. Goldwater Scholarship in recognition of her academic and research success and to support her continued “academic study and research in the fields of science, mathematics, and engineering.” Fu has participated in the Carnegie Summer Undergraduate Research program over the past two summers, working with staff astronomer Josh Simon studying dwarf galaxies and streams of stars surrounding our Milky Way using data from the Sloan Digital Sky Survey.

“The Summer Undergraduate Research Program at the Carnegie Observatories provides undergraduate students the exciting opportunity to

Carnegie Science, Carnegie Institution, Carnegie Institution for Science, Las Campanas Observatory
March 23, 2018

La Serena, Chile—Last week, scientists and staff from Carnegie’s Las Campanas Observatory volunteered for Astroday 2018 at a 170-year-old school in the nearby city of Las Serena, the Colegio Seminario Conciliar.

Organized by the Gemini Observatory, the daylong outreach event features activities including a planetarium, science projects, a 3-D movie, and night sky viewing. Several Chile-based astronomy facilities participated, both from the research and tourist sectors, all sharing the wonders of the universe with the community.

Since its inception in 2006, thousands of La Serena residents have participated in Astroday.

Led by Roberto Bermúdez, the Las Campanas

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The fund supports a postdoctoral fellowship in astronomy that rotates between the Carnegie Science departments of Terrestrial Magnetism in Washington, D.C., and the Observatories in Pasadena California. 

The Earthbound Planet Search Program has discovered hundreds of planets orbiting nearby stars using telescopes at Lick Observatory, Keck Observatory, the Anglo-Australian Observatory, Carnegie's Las Campanas Observatory, and the ESO Paranal Observatory.  Our multi-national team has been collecting data for 30 years, using the Precision Doppler technique.  Highlights of this program include the detection of five of the first six exoplanets, the first eccentric planet, the first multiple planet system, the first sub-Saturn mass planet, the first sub-Neptune mass planet, the first terrestrial mass planet, and the first transit planet.Over the course of 30 years we have improved the

The Giant Magellan Telescope will be one member of the next class of super giant earth-based telescopes that promises to revolutionize our view and understanding of the universe. It will be constructed in the Las Campanas Observatory in Chile. Commissioning of the telescope is scheduled to begin in 2021.

The GMT has a unique design that offers several advantages. It is a segmented mirror telescope that employs seven of today’s largest stiff monolith mirrors as segments. Six off-axis 8.4 meter or 27-foot segments surround a central on-axis segment, forming a single optical surface 24.5 meters, or 80 feet, in diameter with a total collecting area of 368 square meters. The GMT will

Along with Alycia Weinberger and Ian Thompson, Alan Boss has been running the Carnegie Astrometric Planet Search (CAPS) program, which searches for extrasolar planets by the astrometric method, where the planet's presence is detected indirectly through the wobble of the host star around the center of mass of the system. With over eight years of CAPSCam data, they are beginning to see likely true astrometric wobbles beginning to appear. The CAPSCam planet search effort is on the verge of yielding a harvest of astrometrically discovered planets, as well as accurate parallactic distances to many young stars and M dwarfs. For more see  http://instrumentation.obs.carnegiescience.edu/ccd/caps.

Staff member Nick Konidaris joined Carnegie in October 2017. He works on a variety of new optical instrumentation projects in astronomy. He  recently began working on a new development platform for the 40-inch Swope telescope at Carnegie's Las Campanas Observatory. It is called the Rapid Response Swope Spectrograph and Imager (R2S2I). When operational, it will be a workhorse instrument and development platform.

Prior to Carnegie, he was director of product management at Kairos Aerospace in Mountain View, CA. Konidaris received a B.S. in physics from Carnegie Mellon University, and conducted coursework in electrical engineering before obtaining a Ph.D. in astrophysics from the

Experimental petrologist Michael Walter became director of the Geophysical Laboratory beginning April 1, 2018. His recent research has focused on the period early in Earth’s history, shortly after the planet accreted from the cloud of gas and dust surrounding our young Sun, when the mantle and the core first separated into distinct layers. Current topics of investigation also include the structure and properties of various compounds under the extreme pressures and temperatures found deep inside the planet, and information about the pressure, temperature, and chemical conditions of the mantle that can be gleaned from mineral impurities preserved inside diamonds.

Walter had been at

Guoyin Shen's research interests lie in the quest to establish and to examine models for explaining and controlling the behavior of materials under extreme conditions. His research activities include investigation of phase transformations and melting lines in molecular solids, oxides and metals; polyamorphism in liquids and amorphous materials; new states of matter and their emergent properties under extreme conditions; and the development of enabling high-pressure synchrotron techniques for advancing compression science. 

He obtained a Ph.D. in mineral physics from Uppsala University, Sweden in 1994 and a B.S. in geochemistry from Zhejiang University, China in 1982. For more

Leopoldo Infante became the director of the Las Campanas Observatory on July 31, 2017.

Since 2009, Infante has been the founder and director of the Centre for Astro-Engineering at the Chilean university. He joined PUC as an assistant professor in 1990 and has been a full professor since 2006. He was one of the creators of PUC’s Department of Astronomy and Astrophysics, and served as its director from 2000 to 2006. He also established the Chilean Astronomical Society (SOCHIAS) and served as its president from 2009 to 2010.

Infante received his B.Sc. in physics at PUC. He then acquired a MSc. and Ph.D. in physics and astronomy from the University of Victoria in Canada.