Astronomy Stories
Dr. John Mulchaey Staff Scientist Carnegie Observatories The light we see with our eyes only tells a small part of the Universe's story. To get a complete picture of how the Universe works,...
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Pasadena, CA— The Giant Magellan Telescope (GMT) has passed a major milestone as 11 international partners—including Carnegie—approved its construction, which secures the project...
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Pasadena, CA— Type Ia supernovae are violent stellar explosions that shine as some of the brightest objects in the universe. But there are still many mysteries surrounding their origin—...
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Type Ia supernovae are violent stellar explosions that shine as some of the brightest objects in the universe. But there are still many mysteries surrounding their origin—what kind of star...
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Two nights ago, for the first time in history, astronomers from University of Arizona and Carnegie's Yuri Beletsky at Las Campanas Observatory used the Clay Magellan telescope together with...
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Pasadena, CA- John Mulchaey has been appointed the new Crawford H. Greenewalt Director of the Carnegie Observatories. He is the eleventh director of the historic department, which was founded in 1904...
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Carnegie's John Mulchaey talks to NPR's Morning Edition about Edwin Hubble's work at the Mount Wilson Obeservatory and his famous Andromeda plates....
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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...
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The Carnegie Irvine Galaxy Survey is obtaining high-quality optical and near-infrared images of several hundred of the brightest galaxies in the southern hemisphere sky, at Carnegie’s Las Campanas Observatory to investigate the structural properties of galaxies. For more see    http...
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The Carnegie Hubble program is an ongoing comprehensive effort that has a goal of determining the Hubble constant, the expansion rate of the universe,  to a systematic accuracy of 2%. As part of this program, astronomers are obtaining data at the 3.6 micron wavelength using the Infrared Array...
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Alycia Weinberger wants to understand how planets form, so she observes young stars in our galaxy and their disks, from which planets are born. She also looks for and studies planetary systems. Studying disks surrounding nearby stars help us determine the necessary conditions for planet formation....
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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...
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John Mulchaey is the director and the Crawford H. Greenewalt Chair of the Carnegie Observatories. He investigates groups and clusters of galaxies, elliptical galaxies, dark matter—the invisible material that makes up most of the universe—active galaxies and black holes. He is also...
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Pasadena, California— El universo está lleno de miles de millones de galaxias—pero su distribución en el espacio está lejos de ser uniforme. ¿Por qué vemos tantas estructuras en el universo hoy y...
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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...
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Pasadena, CA— Astronomers, including Carnegie’s Yuri Beletsky, took precise measurements of the closest pair of failed stars to the Sun, which suggest that the system harbors a third, planetary-mass...
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This artist's impression of the quasar P172+18. Credit: ESO/M. Kornmesser.
March 8, 2021

Pasadena, CA— The Magellan Baade telescope at Carnegie’s Las Campanas Observatory played an important role in the discovery of the most-distant known quasar with a bright radio emission, which was announced by a Max Planck Institute for Astronomy in Heidelberg and European Southern Observatory-led team and published in The Astrophysical Journal. One of the fastest-growing supermassive black holes ever observed, it is emitting about 580 times the energy as the entire Milky Way galaxy.

Quasars are incredibly luminous supermassive black holes accreting matter at the centers of massive galaxies. Their brightness allows astronomers to study them in detail even at great

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

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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 Carnegie Irvine Galaxy Survey is obtaining high-quality optical and near-infrared images of several hundred of the brightest galaxies in the southern hemisphere sky, at Carnegie’s Las Campanas Observatory to investigate the structural properties of galaxies. For more see    http://cgs.obs.carnegiescience.edu/CGS/Home.html

The Carnegie-Spitzer-IMACS (CSI) survey, currently underway at the Magellan-Baade 6.5m telescope in Chile, has been specifically designed to characterize normal galaxies and their environments at a distance of about 4 billion years post Big Bang, expresses by astronomers as  z=1.5.

The survey selection is done using the Spitzer Space Telescope Legacy fields, which provides as close a selection by stellar mass as possible.

Using the IMACS infrared camera, the survey goal is to study galaxies down to low light magnitudes. The goal is to reduce the variance in the density of massive galaxies at these distances and times to accurately trace the evolution of the galaxy mass

The recent discovery that the universe is expanding at an accelerating rate has profoundly affected physics. If the universe were gravity-dominated then it should be decelerating. These contrary results suggest a new form of “dark energy”—some kind of repulsive force—is driving the universe. To get a grasp of dark energy, it is extremely important that scientists get the most accurate measurements possible of Type Ia supernovae. These are specific types of exploring stars with exceptional luminosity that allow astronomers to determine distances and the acceleration rate at different distances. At the moment, the reality of the accelerating universe remains

While the planets in our Solar System are astonishingly diverse, all of them move around the Sun in approximately the same orbital plane, in the same direction, and primarily in circular orbits. Over the past 25 years Butler's work has focused on improving the measurement precision of stellar Doppler velocities, from 300 meters per second in the 1980s to 1 meter a second in the 2010s to detect planets around other stars. The ultimate goal is to find planets that resemble the Earth.

Butler designed and built the iodine absorption cell system at Lick Observatory, which resulted in the discovery of 5 of the first 6 known extrasolar planets.  This instrument has become the de

Galacticus is not a super hero; it’s a super model used to determine the formation and evolution of the galaxies. Developed by Andrew Benson, the George Ellery Hale Distinguished Scholar in Theoretical Astrophysics, it is one of the most advanced models of galaxy formation available.

Rather than building his model around observational data, Benson’s Galacticus relies on known laws of physics and the so-called N-body problem, which predicts the motions of celestial bodies that interact gravitationally in groups. Galacticus’ now an open- source model produces results as stunning 3-D videos.

Some 80% of the matter in the universe cannot be seen. This unseen

The entire universe—galaxies, stars, and planets—originally condensed from a vast network of tenuous, gaseous filaments, known as the intergalactic medium, or the gaseous cosmic web. Most of the matter in this giant reservoir has never been incorporated into galaxies; it keeps floating about in intergalactic space, largely in the form of ionized hydrogen gas.

 Michael Rauch is interested in all aspects of the intergalactic medium. He uses large telescopes, like the Magellans, to take spectra—light that reveals the chemical makeup of distant objects— of background quasars, which are highly energetic and extremely remote. He is looking for evidence of

Staff member emeritus François Schweizer studies galaxy assembly and evolution by observing nearby galaxies, particularly how collisions and mergers affect their properties. His research has added to the awareness that these events are dominant processes in shaping galaxies and determining their stellar and gaseous contents.

When nearby galaxies collide and merge they yield valuable clues about processes that occurred much more frequently in the younger, distant universe. When two gas-rich galaxies collide, their pervasive interstellar gas gets compressed, clumps into dense clouds, and fuels the sudden birth of billions of new stars and thousands of star clusters.