Director Emeritus, George Preston has been deciphering the chemical evolution of stars in our Milky Way for a quarter of a century. He and Steve Shectman started this quest using a special technique to conduct a needle-in-the-haystack search for the few, first-generation stars, whose chemical compositions sketch the history of element formation in the galaxy. These earliest stars are very rare and they are characteristically low in heavy metals because of their age. They were made of Big Bang material, mostly hydrogen and helium. It was only later that heavier elements were formed in the nuclear furnaces of newer stars.

 In their first study, Preston and Shectman compiled a list of hundreds of candidate so-called low-metal/old stars. They followed it with a more detailed analysis confirming their status, one by one. Over the years, others joined the effort.

Preston explores the consequences of the very first survey using the facilities at Carnegie’s  Las Campanas Observatory. He is tracing the rates of atomic enrichment of different types of atoms produced by various nuclear mechanisms. He uses the decay rate of radioactive thorium in some of the oldest stars to measure their ages. By discovering traces of the heaviest stable elements, lead and bismuth, he is also looking into the processes in other stars to refine theories of special nucleosynthesis—a process that creates and expels elements in certain dying stars. He also explores the mysteries of mass exchange between members of old binary star systems that contain these dying stars.

 More recently he has turned his attention to a surprising find—a recently-discovered pulsating (RR Lyrae) star highly enriched in carbon, a characteristic that defies experience and prior expectations.

Preston received his degree in physics from Yale University and his Ph.D. in astronomy from the University of California, Berkeley. He was a Carnegie Fellow with the Mount Wilson Observatory from 1959 to 1960. In 1965 he won the Helen B. Warner Prize for astronomy from the American Astronomical Society. Preston has been a Carnegie staff member since 1968 and served as director of the Observatories from 1981 to 1986. For more  information see

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 "Blue Snowball" planetary nebula, courtesy of Eric Hsiao.
September 10, 2020

Pasadena, CA—An unusual stellar explosion is shining new light on the origins of a specific subgroup of Type Ia supernovae.

Called LSQ14fmg, the exploding star exhibits certain characteristics that are unlike any other supernova. For example, its brightness increases at an extremely slow rate compared to other Type Ia supernovae. Despite this, it is also one of the brightest explosions in its class.

“Type Ia supernovae are violent, fantastically bright explosions of a white dwarf—the remnant of a star that has exhausted its nuclear fuel—which is part of a binary system with another star,” said Carnegie astronomer Mark Phillips, an expert in

Widmanstatten pattern characteristic of iron meteorites, courtesy of Peng Ni.
August 3, 2020

Washington, DC— Work led by Carnegie’s Peng Ni and Anat Shahar uncovers new details about our Solar System’s oldest planetary objects, which broke apart in long-ago collisions to form iron-rich meteorites.  Their findings reveal that the distinct chemical signatures of these meteorites can be explained by the process of core crystallization in their parent bodies, deepening our understanding of the geochemistry occurring in the Solar System’s youth. They are published by Nature Geoscience.

Many of the meteorites that shot through our planet’s atmosphere and crashed on its surface were once part of larger objects that broke up at some point in our

Phoenix Stellar Stream illustration courtesy of Geraint F. Lewis.
July 29, 2020

Pasadena, CA—A team of astronomers including Carnegie’s Ting Li and Alexander Ji discovered a stellar stream composed of the remnants of an ancient globular cluster that was torn apart by the Milky Way’s gravity 2 billion years ago, when Earth’s most-complex lifeforms were single-celled organisms. This surprising finding, published in Nature, upends conventional wisdom about how these celestial objects form.

Imagine a sphere made up of a million stars bound by gravity and orbiting a galactic core. That’s a globular cluster. The Milky Way is home to about 150 of them, which form a tenuous halo that envelops our galaxy.

But the globular cluster

The du Pont telescope, courtesy Matias del Campo
July 20, 2020

Pasadena, CA— Filling in the most-significant gaps in our understanding of the universe’s history, the Sloan Digital Sky Survey (SDSS) released Sunday a comprehensive analysis of the largest three-dimensional map of the cosmos ever created.

The survey, of which Carnegie is an integral member, has been one of the most successful and influential in the history of astronomy. It operates out of both Apache Point Observatory in New Mexico, home of the survey’s original 2.5-meter telescope, and Carnegie’s Las Campanas Observatory in Chile, where it uses Carnegie’s du Pont telescope.

The new results come from the extended Baryon Oscillation

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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

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

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

Johanna Teske became the first new staff member to join Carnegie’s newly named Earth and Planets Laboratory (EPL) in Washington, D.C., on September 1, 2020. She has been a NASA Hubble Fellow at the Carnegie Observatories in Pasadena, CA, since 2018. From 2014 to 2017 she was the Carnegie Origins Postdoctoral Fellow—a joint position between Carnegie’s Department of Terrestrial Magnetism (now part of EPL) and the Carnegie Observatories.

Teske is interested in the diversity in exoplanet compositions and the origins of that diversity. She uses observations to estimate exoplanet interior and atmospheric compositions, and the chemical environments of their formation

Phillip Cleves’ Ph.D. research was on determining the genetic changes that drive morphological evolution. He used the emerging model organism, the stickleback fish, to map genetic changes that control skeletal evolution. Using new genetic mapping and reverse genetic tools developed during his Ph.D., Cleves identified regulatory changes in a protein called bone morphogenetic protein 6 that were responsible for an evolved increase in tooth number in stickleback. This work illustrated how molecular changes can generate morphological novelty in vertebrates.

Cleves returned to his passion for coral research in his postdoctoral work in John Pringles’ lab at Stanford

Brittany Belin joined the Department of Embryology staff in August 2020. Her Ph.D. research involved developing new tools for in vivo imaging of actin in cell nuclei. Actin is a major structural element in eukaryotic cells—cells with a nucleus and organelles —forming contractile polymers that drive muscle contraction, the migration of immune cells to  infection sites, and the movement of signals from one part of a cell to another. Using the tools developed in her Ph.D., Belin discovered a new role for actin in aiding the repair of DNA breaks in human cells caused by carcinogens, UV light, and other mutagens.

Belin changed course for her postdoctoral work, in

Evolutionary geneticist Moises Exposito-Alonso joined the Department of Plant Biology as a staff associate in September 2019. He investigates whether and how plants will evolve to keep pace with climate change by conducting large-scale ecological and genome sequencing experiments. He also develops computational methods to derive fundamental principles of evolution, such as how fast natural populations acquire new mutations and how past climates shaped continental-scale biodiversity patterns. His goal is to use these first principles and computational approaches to forecast evolutionary outcomes of populations under climate change to anticipate potential future