Looking far into space is looking back in time. Staff astronomer emeritus Alan Dressler began his career at Carnegie some years ago as a Carnegie Fellow. Today, he and colleagues use Magellan and the Hubble Space Telescope to study galaxy evolution—how galaxy structures and shapes change, the pace and character of star birth, and how large galaxies form from earlier, smaller systems.

Dressler is also intricately involved in instrumentation. He led the effort for the Inamori Magellan Areal Spectrogrph (IMACS), a wide-field imager and multi-object spectrograph which became operational in 2003 on the Baade telescope at Carnegie’s Las Campanas Observatory. Spectrographs take light collected by a telescope and disperse it into a spectrum of wavelengths, which reveals elements of celestial objects.

Dressler was also coprincipal in a project known as “the Morphs,” which focused on the evolution of spiral galaxies over the last 7 billion years. The group found that star formation was more common in galaxies 5 billion years ago than it is today, and that much of this star formation occurred in starbursts, in contrast to the more steady star formation seen today.

With colleagues, Dressler continues working on a new collaboration among others, called the IMACS Cluster Building Survey, which follows the evolution in stellar population and structure, of a large sample of galaxies in the outskirts of distant galaxy clusters. The survey provides spectra of some 2200 galaxies.

Dressler received his B.A. in physics from the University of California, Berkeley and his Ph.D. in astronomy from the University of California, Santa Cruz. He was then awarded a Carnegie fellowship, then a Las Campnas fellowship, before becoming a staff astronomer in 1981.For more information  see http://obs.carnegiescience.edu/users/dressler

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3D spatial distribution of 16 spectroscopically confirmed proto-clusters.
February 12, 2021

Las Campanas Observatory—When the universe was about 350 million years old it was dark: there were no stars or galaxies, only neutral gas—mainly hydrogen—the residue of the Big Bang. That foggy period began to clear as atoms clumped together to form the first stars and the first quasars, causing the gas to ionize and high-energy photons to travel freely through space. 

This epoch, called the “reionization” epoch, lasted about 370 million years and the first large structures in the universe appear as groups or clusters of galaxies. 

An international team of astronomers grouped in the LAGER consortium (Lyman Alpha Galaxies in the Epoch

Vicinity of Tucana II ultra-faint dwarf galaxy. Credit: Anirudh Chiti/MIT.
February 1, 2021

Pasadena, CA—An MIT-led team of astronomers that includes Carnegie’s Joshua Simon, Lina Necib, and Alexander Ji has discovered an unexpected outer suburb of stars on the distant fringes of the dwarf galaxy Tucana II. Their detection, published by Nature Astronomy, confirms that the cosmos’ oldest galaxies formed inside massive clumps of dark matter—what astronomers refer to as a “dark matter halo."

Our own Milky Way is surrounded by a cadre of orbiting dwarf galaxies—relics of the ancient universe. A new technique developed by lead author Anirudh Chiti of MIT extended the astronomers’ reach and revealed never-before-seen stars on the

A giant star being slowly devoured by a black hole courtesy of NASA Goddard.
January 12, 2021

Pasadena, CA—In a case of cosmic mistaken identity, an international team of astronomers revealed that what they once thought was a supernova is actually periodic flaring from a galaxy where a supermassive black hole gives off bursts of energy every 114 days as it tears off chunks of an orbiting star.

Six years after its initial discovery—reported in The Astronomer’s Telegram by Carnegie’s Thomas Holoien—the researchers, led by Anna Payne of University of Hawai’i at Mānoa, can now say that the phenomenon they observed, called ASASSN-14ko, is a periodically recurring flare from the center of a galaxy more than 570 million light-years away in the

An artist’s conception of GN-z11 courtesy of Jingchuan Yu.
December 14, 2020

Pasadena, CA— New work from an international team of astronomers including Carnegie’s Gregory Walth improves our understanding of the most-distant known astrophysical object— GN-z11, a galaxy 13.4 billion light-years from Earth.

Formed 400 million years after the Big Bang, GN-z11 was previously determined by space telescope data to be the most-distant object yet discovered. In two newly published Nature Astronomy papers, a team led by Linhua Jiang at the Kavli Institute for Astronomy and Astrophysics at Peking University took near-infrared spectra using ground-based telescopes that confirmed the galaxy’s distance. They also caught an ultraviolet flash

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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  http://instrumentation.obs.carnegiescience.edu/

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