The Center for Astrophysics | Harvard & Smithsonian
The Center for Astrophysics | Harvard & Smithsonian
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Planetary Systems

The Milky Way is home to hundreds of billions of planets, an estimate based on the thousands of known worlds discovered just within the last few decades. With this much information, astronomers work to understand the similarities and differences between planetary systems, including our Solar System. This field encompasses research on the planets, comets, and other inhabitants of the Solar System, as well as studies of exoplanets and newborn planetary systems.

Our Work

Center for Astrophysics | Harvard & Smithsonian scientists engage in many types of planetary systems research:

  • Finding and describing new exoplanets using TESS and other observatories. TESS is designed to observe stars closer to the Solar System than those studied by other observatories, providing targets for other telescopes for follow-up observations.
    NASA Prepares to Launch Next Mission to Search the Sky for New Worlds

  • Hunting for potentially habitable exoplanets using robotic observatories. Those include the CfA’s MEarth Project, which focuses on planets orbiting red dwarf stars, and the MINiature Exoplanet Radial Velocity Array (MINERVA), which locates planets orbiting Sun-like stars.
    MINERVA: Hunting for Earth's Twin

  • Identifying the chemical composition of newborn star systems, and comparing that to the Solar System. Using the Atacama Large Millimeter/submillimeter Array (ALMA), the CfA’s Submillimeter Array (SMA), and other observatories, astronomers have identified complex organic molecules in the regions around newborn stars. Similar chemicals have been found on comets, which are fragments left over from the era when the Solar System first formed.
    Astronomers Discover Traces of Methyl Chloride around Infant Stars and Nearby Comet

  • Finding infant planets that might be Earth-like. Exoplanets orbiting stars in Earth-like orbits are difficult to detect, but ALMA and other observatories are capable of identifying newborn worlds at ever-closer orbits around their host stars. Studying how potentially habitable planets form helps us understand our own origins, and how common Earth-like worlds might be in the galaxy.
    A Planet Is Forming in an Earth-like Orbit around a Young Star

3,700+
Number of confirmed exoplanets

The Diversity of Planets

The Solar System contains four rocky planets, two large gaseous planets, and two other giant worlds, along with five dwarf planets and a wealth of moons, comets, asteroids, and icy worlds. The challenges of observing other star systems means we mostly know about planets orbiting close in to their host stars, with very little information so far about planets orbiting farther out — much less moons, asteroids, and so on. However, a combination of theory and observation is bringing us to a fuller picture of the possible planetary systems, what they contain, and how they were formed.

  • In the early years of exoplanet research, astronomers were happy just to discover any planet. Today, the focus is on classifying all the systems discovered so far, and hunting for smaller planets orbiting farther out from their host stars. In particular, researchers want to find Earth-sized planets in the habitable zones of their stars: the range of distances where liquid water could conceivably exist. Next-generation observatories such as NASA's Transiting Exoplanet Survey Satellite (TESS) are designed for that purpose.

  • Many identified exoplanets are different from what we see in the Solar System. Planets more massive than Jupiter are common, but most exoplanets fall between Earth and Neptune in size or mass. These “super-Earths” are probably rocky, which raises questions about how they might differ from the inner planets of the Solar System and whether they could support life as we understand it.

  • Until the exoplanet revolution, our understanding of planet formation was based entirely on the Solar System. With the extra information from other planetary systems, researchers have a clearer picture of the complexities of how planets form and migrate in infant star systems. Researchers combine theoretical simulations with observations of newborn planetary systems to understand how the diverse worlds we see came into existence. That includes the distribution of atoms and molecules making planets, particularly those required for Earth-like life.

  • Of course, the best understood planetary system is our own Solar System. Comets and asteroids are remnants of the early years of the Solar System’s existence, providing us with a look at the environment before Earth formed. Astronomers have found similar chemical signatures on comets and in distant star systems, indicating some common processes.

  • Our best observations of atmospheres also come from planets in our Solar System, including the planet we know best: Earth. Understanding the differences between planets in our Solar System allows us to create models for exoplanet atmospheres. In addition, researchers are developing new methods to detect molecules in the atmospheres of distant worlds, particularly those like water or oxygen that are closely linked to life on Earth.

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Projects

AstroAI

Atomic and Molecular Physics, High Energy Astrophysics, Optical and Infrared Astronomy, Radio and Geoastronomy, Solar, Stellar, and Planetary Sciences, Theoretical Astrophysics, Harvard University Department of Astronomy, Science Education Department, Central Engineering, Director's Office, Chandra X-ray Center, Institute for Theoretical Atomic Molecular and Optical Physics, Institute for Theory and Computation
AstroAI is a institute dedicated to the development of artificial intelligence to enable next generation astrophysics at the Center for Astrophysics | Harvard & Smithsonian. Learn More
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GMACS

Optical and Infrared Astronomy, Central Engineering
GMACS - Moderate Dispersion Optical Spectrograph for the Giant Magellan Telescope is a powerful optical spectrograph that will unlock the power of the Giant Magellan Telescope for research ranging from the formation of stars and planets to cosmology.

For Scientists
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Telescopes and Instruments

1.3 Meter Telescope

The Two Micron All-Sky Survey (2MASS) was an ambitious project to map the entire sky in infrared light, providing a cosmic census of galaxies, star clusters, small Solar System bodies, and many more. 2MASS used two telescopes: the 1.3 Meter Telescope operated by the Center for Astrophysics | Harvard & Smithsonian, located at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona; and an identical instrument operated by the Cerro Tololo Inter-American Observatory in Chile. The survey was concluded in the late 1990s, making the telescope available to CfA astronomers and collaborators for new projects. The telescope was converted to automatic control, and renamed Peters Automated Infrared Imaging Telescope (PAIRITEL), for a program monitoring transient events such as supernovas and gamma-ray bursts. The PAIRITEL project ran from 2003 to 2012. Plans are underway in 2019 to reconfigure the telescope for visible-light measurements to hunt for exoplanets.

Visit the 1.3 Meter Telescope Website
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1.5-meter Tillinghast (60-inch) Telescope

The 1.5-Meter (60 Inch) Tillinghast Telescope is a general purpose visible-light telescope located at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, operated by the Center for Astrophysics | Harvard & Smithsonian. Astronomers use this telescope to measure the spectrum of light emitted by a wide variety of objects in the Solar System, the Milky Way, and in distant galaxies.

CfA Operated (OIR) | Open to CfA Scientists | Active

Visit the 1.5 Meter (60 Inch) Tillinghast Telescope Website
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Giant Magellan Telescope

Is Earth unique, or are there other planets with life in the Milky Way? To answer this question and many others, astronomers need larger and more sensitive observatories than anything we currently have. For that reason, the Center for Astrophysics | Harvard & Smithsonian is collaborating with a number of other institutions around the world to create the Giant Magellan Telescope (GMT), currently under construction in Chile. The GMT will consist of seven large mirrors acting in concert as one giant telescope 80 feet across. That large size provides an unprecedented view of the sky and the ability to detect the chemical composition of exoplanet atmospheres. Like NASA’s Hubble Space Telescope, the GMT will be a powerful tool across the field of astronomy, providing insights into the formation of planets, the structure of galaxies, and the evolution of the universe itself.

Visit the GMT Website
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High Accuracy Radial Velocity Planet Searcher-North (HARPS-N)

Measuring the mass of a distant exoplanet requires tracking the changes in light of the host star as the planet’s gravity tugs it slightly — a delicate process. The High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) is an instrument designed for that purpose. HARPS-N is installed on the Telescopio Nazionale Galileo at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands. The instrument provides valuable follow-up observations for the smaller exoplanets identified by NASA’s Kepler/K2 space telescope and other observatories. Astronomers at the Center for Astrophysics | Harvard & Smithsonian are part of the international collaboration operating the instrument. Using the high quality data from HARPS-N, astronomers hope to measure the masses of Earth-like worlds to sufficient accuracy to determine how much these planets resemble ours.

Visit the HARPS-N Website
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Hungarian-made Automated Telescope Network (HATNet)

The Hungarian-made Automated Telescope Network (HATNet) is a set of computer-controlled small telescopes located at various observatories around the world. Five of these telescopes are hosted at the Fred Lawrence Whipple Observatory (FLWO), a Center for Astrophysics | Harvard & Smithsonian facility in southern Arizona. HATNet is designed to look for planets in orbit around bright stars; since beginning operations in 2001, astronomers have used the network to identify 70 confirmed exoplanets and several hundred additional candidates that have not yet been confirmed as exoplanets or ruled out as false positives.

Visit the HATNet Website
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Kepler/K2

Since the early 1990s, astronomers have identified thousands of planets orbiting other stars. Most of those identifications have come thanks to one observatory: NASA’s Kepler space telescope. Until it lost its ability to point, Kepler observed a region of the sky containing about 150,000 stars with potential planets, monitoring them for the slight decrease in light caused by planets crossing in front of the star. After the spacecraft’s pointing control failed, the mission was renamed K2, and it continued to hunt for exoplanets as it tumbled slowly, with its field of view drifting slowly across the sky. The mission finally ended in 2018, though the data it produced continues to provide astronomers with valuable information about planets in our galactic neighborhood. Astronomers from the Center for Astrophysics | Harvard & Smithsonian were responsible for the preparation of the catalog for potentially interesting stars, and have participated extensively in follow-up observations of Kepler planetary discoveries.

Visit the Kepler/K2 Website
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Magellan Telescopes

The twin Magellan Telescopes in Chile are each 6.5 meter optical telescopes. These telescopes are both equipped with instruments to take images and spectra of light from a wide variety of astronomical sources, including exoplanet systems, star-forming regions, supernova remnants, and interacting galaxies. The Magellan Telescopes — named Baade and Clay —  are hosted at the Las Campanas Observatory and are operated by a consortium of institutions, including the Center for Astrophysics | Harvard & Smithsonian, Carnegie Institution for Science, University of Arizona, the University of Michigan, and the Massachusetts Institute of Technology. In addition, CfA scientists and engineers provided a wide field f/5 focal system (including secondary mirror and corrective optics), and a powerful astronomical camera for use at the Clay telescope.

Visit the Magellan Telescopes Website
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MEarth

How many Earth-sized planets are out there? How many of those might support life? Answering these questions is complicated because Earth-like worlds are small, making them hard to detect. The MEarth Project — pronounced “mirth” — simplifies the problem by looking for planets orbiting small, red M dwarf stars. Potentially habitable Earth-sized planets have smaller orbits around these stars than yellow Sun-like stars, allowing MEarth to identify them. The MEarth telescopes are operated by the Center for Astrophysics | Harvard & Smithsonian and located at the CfA’s Fred Lawrence Whipple Observatory (FLWO) in Arizona and the Cerro Tololo Inter-American Observatory (CTIO) in Chile. Astronomers have used MEarth to identify multiple planets, including the rocky planet GJ1132b.

Visit the MEarth Website
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MINiature Exoplanet Radial Velocity Array (MINERVA)

Finding potentially habitable exoplanets is a major goal of modern astronomy, but Earth-like worlds in Earth-like orbits are hard to detect. The MINiature Exoplanet Radial Velocity Array (MINERVA) project is a set of small telescopes designed to look at two related but simpler systems: Earth-size planets close to their host stars, and “super-Earths” in more Earth-like orbits. MINERVA is a collaboration between the Center for Astrophysics | Harvard & Smithsonian, the University of Montana, Penn State, the University of Southern Queensland, and the University of Pennsylvania. The telescopes are hosted at the CfA’s Fred Lawrence Whipple Observatory (FLWO) in Arizona.

Visit the MINERVA Website
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MMT Observatory

The MMT Observatory is the premier visible-light and infrared telescope jointly managed by the Smithsonian Astrophysical Observatory, part of the Center for Astrophysics | Harvard & Smithsonian, and the University of Arizona. Located at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona, this 6.5-meter (21 foot) telescope is used to study objects across the field of astronomy, from the Solar System to distant galaxies. The MMT has provided a testbed for new telescope technologies developed by scientists and engineers at the CfA and the University of Arizona.

Visit the MMT Website
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Spitzer Space Telescope

Infrared light is the key to studying a wide range of astronomical systems, including newborn stars and planets, dust in distant galaxies, and material swirling around black holes. The Spitzer Space Telescope was NASA’s orbiting infrared observatory, and part of NASA’s Great Observatories program, along with the Chandra X-ray Observatory and the Hubble Space Telescope. Scientists and engineers at the Center for Astrophysics | Harvard & Smithsonian led the design, testing, and construction of the Infrared Array Camera (IRAC). The Spitzer Space Telescope was launched in 2003 and retired in 2020.

Visit the Spitzer Space Telescope IRAC Page
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The Submillimeter Array - Maunakea, HI

Located near the summit of Maunakea on the Big Island of Hawaii, the Submillimeter Array (SMA) is one of the flagship observatories of the Center for Astrophysics | Harvard & Smithsonian. The observatory consists of eight radio dishes working together as one telescope, giving astronomers a window on a wide range of astronomical objects and phenomena: planets and comets in our own Solar System; the birth of stars and planets; and the supermassive black holes hidden at the centers of the Milky Way and other galaxies. The SMA is operated jointly by the CfA and the Academia Sinica in Taiwan.

Visit the Submillimeter Array Website
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Transiting Exoplanet Survey Satellite (TESS)

Astronomers have discovered thousands of planets orbiting other stars. Extrapolating from that knowledge, the Milky Way alone is probably home to hundreds of billions of planets, many of which are likely rocky, Earth-like worlds. NASA’s Transiting Exoplanet Survey Satellite (TESS) is a space observatory designed to look for exoplanets in orbit around 200,000 nearby bright stars, with a particular interest in identifying small planets. Astronomers from the Center for Astrophysics | Harvard & Smithsonian are part of the scientific team to analyze TESS data, as well as performing follow-up observations. The relative closeness of worlds in the TESS survey will allow astronomers to even study some of their atmospheres, using the future Giant Magellan Telescope (GMT) and other observatories. TESS observational program is complementary to NASA’s long-running Kepler/K2 mission, and could identify as many as 20,000 new exoplanet orbiting a wide variety of star types.

Visit the TESS Website
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