Scott Sheppard studies the dynamical and physical properties of small bodies in our Solar System, such as asteroids, comets, moons and trans-neptunian objects (bodies that orbit beyond Neptune).  These objects have a fossilized imprint from the formation and migration of the major planets in our Solar System, which allow us to understand how the Solar System came to be.

The major planets in our Solar System travel around the Sun in fairly circular orbits and on similar planes. However, since the discovery of wildly varying planetary systems around other stars, and given our increased understanding about small, primordial bodies in our celestial neighborhood, the notion that our Solar System has always been so orderly is changing.

To understand solar system evolution in general and how ours came to be, Carnegie’s Department of Terrestrial Magnetism astronomer Scott Sheppard studies the dynamical and physical properties of small bodies, such as asteroids, comets, moons, trans-neptunian objects (bodies that orbit beyond Neptune), and free floating substellar objects. These small bodies in our Solar System have a fossilized imprint from the formation and migration of the major planets in our Solar System.

The known Solar System can be divided into three parts: the rocky planets like Earth, which are close to the Sun; the gas giant planets, which are further out; and the frozen objects of the Kuiper belt, which lie just beyond Neptune's orbit. Beyond this, there appears to be an edge to the Solar System where only one object, Sedna, was known to exist for its entire orbit until Sheppard and colleagues discovered a second object, dwarf planet 2012 VP113. It has a very eccentric orbit that is even more distant than Sedna. Sheppard has determined that the total population of these so called inner Oort cloud objects is likely bigger than the Kuiper Belt and main asteroid belt. Some of these inner Oort cloud objects could rival the size of Mars or Earth.

There are several competing theories for how the inner Oort cloud might have formed, but all require the Solar System to have been in a state vastly different than now since the inner Oort cloud objects are currently decoupled from any known major planet, yet have disturbed inclined, eccentric orbits. Thus the inner Oort cloud is a window into our Solar System's past. Sheppard and colleague are currently obtaining the widest and deepest survey for Solar System objects ever obtained to discover more inner Oort cloud members.

Active asteroids have stable orbits between Mars and Jupiter like other asteroids. However, unlike other asteroids, they sometimes have the appearance of comets, when dust or gas is ejected from their surfaces. The reasons for this loss of material and subsequent tail in active asteroids are unknown, although there are several theories such as recent impacts or sublimation of exposed ices. Sheppard and colleagues discovered an unexpected tail on asteroid 62412, an object which had been known as a typical asteroid for over a decade. Using Magellan Telescopic observations, Sheppard found 62412 to have a very fast rotation. It thus appears the activity in this asteroid is created by rotational fissioning of material off the surface of 62412. Sheppard and colleagues estimate that there are likely about 100 active asteroids in the main asteroid belt, based on their discovery.

Sheppard is also the co-discoverer of the first trailing Neptune Trojan and first high inclination leading Neptune Trojan. Trojans are asteroids that are locked into the same orbital period as a planet but lead or follow the planet by about 60 degrees. At these spots, the gravitational pull of the planet and the Sun combine to lock the asteroids into synchronized orbits with the planet. The presence of high inclination Trojans implies that Neptune was on a much more eccentric orbit in the past. As Neptune went through the process of becoming more circular in orbit, it gained the ability to capture high-inclination objects. Sheppard has also learned that Neptune Trojans share many similarities with their Jupiter counterparts.

In another research area, Sheppard surveys our Solar System for so-called irregular satellites. These bodies have been captured by their respective planets. Regular satellites, on the other hand, were created during disk accretion. Sheppard and colleagues have discovered over 70 of the irregular moons around Jupiter, Saturn, Uranus, and Neptune. During the survey, Sheppard determined that the giant planets all possess about the same number of irregular satellites, despite large differences in planetary mass and formation scenarios.

Sheppard discovered the first contact binary Kuiper belt object. A contact binary contains two objects that are drawn together by tidal friction like the Earth and the Moon to orbit about one another. The large amount of angular momentum in the Kuiper Belt suggests it was much denser in the distant past. Similar observations by Sheppard and his colleagues also yielded one of the first measurements of the bulk density of a KBO; the value is sufficiently low that a volatile-rich, porous structure is indicated.

Sheppard received his B.A. in physics from Oberlin College and his M.S. and Ph. D. from the University of Hawaii, where he was also a teaching assistant and a research assistant. Before becoming a staff scientist at Carnegie in 2007, he was a Carnegie Hubble Fellow. For more see http://dtm.carnegiescience.edu/people/scott-s-sheppard

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Illustration by James Josephides, courtesy of Swinburne Astronomy Productions.
November 12, 2019

Pasadena, CA—A star traveling at ultrafast speeds after being ejected by the supermassive black hole at the heart of our galaxy was spotted by an international team of astronomers including Carnegie’s Ting Li and Alex Ji. Their work is published by Monthly Notices of the Royal Astronomical Society. Hurtling at the blistering speed of 6 million kilometers per hour, the star is moving so fast that it will leave the Milky Way and head into intergalactic space.

Called S5-HVS1, the star was discovered in the Grus, or Crane, constellation by lead author Sergey Koposov of Carnegie Mellon University as part of the Southern Stellar Stream Spectroscopic Survey led by Carnegie

Ancient gas cloud courtesy of the Max Planck Society.
November 8, 2019

Washington, DC— The discovery of a 13 billion-year-old cosmic cloud of gas enabled a team of Carnegie astronomers to perform the earliest-ever measurement of how the universe was enriched with a diversity of chemical elements.  Their findings reveal that the first generation of stars formed more quickly than previously thought. The research, led by recent Carnegie-Princeton fellow Eduardo Bañados and including Carnegie’s Michael Rauch and Tom Cooper, is published by The Astrophysical Journal.

The Big Bang started the universe as a hot, murky soup of extremely energetic particles that was rapidly expanding.  As this material spread out, it cooled,

Patrick McCarthy courtesy of GMTO
October 1, 2019

Pasadena, CA—Carnegie astronomer and Vice President of the Giant Magellan Telescope (GMT), Patrick McCarthy, has been appointed as the first Director of the National Science Foundation’s newly formed National Optical-Infrared Astronomy Research Laboratory (NSF’s OIR Lab).

McCarthy has been a member of the GMT project since its inception 15 years ago, helping to bring it from a sketch on a napkin to a 100-plus person organization with 12 U.S. and international partners. In 2008, 20 years into his tenure at Carnegie, McCarthy officially expanded his role when he accepted his current leadership position at GMT.

Working with then-Carnegie Observatories

lustración por Robin Dienel, cortesía de Carnegie Institution for Science.
September 26, 2019

Washington, DC—El satélite Transiting Exoplanet Survey Satellite (TESS) de la NASA ha observado por primera vez las secuelas de una estrella que fue violentamente desgarrada por un agujero negro supermasivo. El haber capturado en pleno desarrollo un evento tan poco común ayudará a los astrónomos a entender estos misteriosos fenómenos.

Las observaciones fueron publicadas en la revista científica The Astrophysical Journal y el estudio fue liderado por el astrónomo de la Institución Carnegie, Thomas Holoien. Holoien es uno de los miembros fundadores de la red internacional de telescopios que realizó el

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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/

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

Staff Associate Kamena Kostova joined the Department of Embryology in November 2018. She studies ribosomes, the factory-like structures inside cells that produce proteins. Scientists have known about ribosome structure, function, and biogenesis for some time. But, a major unanswered question is how cells monitor the integrity of the ribosome itself. Problems with ribosomes have been associated with diseases including neurodegeneration and cancer. The Kostova lab investigates the fundamental question of how cells respond when their ribosomes break down using mass spectrometry, functional genomics methods, and CRISPR genome editing.

Kostova received a B.S. in Biology from the

Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level.  Tracy received her Ph.D. from the California Institute of

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly  Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments.