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Does life exist outside of the solar system?

Since humans first looked to the cosmos, we have wondered if life exists elsewhere in the Universe. Scientists and engineers at the Center for Astrophysics | Harvard & Smithsonian may soon be able to answer that question.

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How We Search

Exoplanets, or planets in solar systems other than our own, sometimes orbit directly between the Earth and their host star. When the planet orbits in front of its star, it blocks a small amount of light. CfA scientists use the Transiting Exoplanet Survey Satellite (TESS) and the Kepler space telescopes as well as the ground-based robotic telescopes of the MEarth project to look for dips in starlight. This “transit” method of planet hunting has revealed thousands of exoplanets.

During a transit, a small amount of starlight is absorbed by the planet’s atmosphere, yielding clues to the chemical makeup of the atmosphere. A massive, technologically advanced telescope is crucial for detecting the composition of an Earth-like planet’s atmosphere, including the subtle chemical signatures that life is expected to produce.

Thanks to next generation telescopes like the planned Giant Magellan Telescope (GMT), we are approaching a point in our observational capabilities that may allow us to make previously unthinkable discoveries. One of these breakthroughs is the detection of life on a distant planet, light years away from Earth.

Juliana Garcia-Mejia working on the GMT-Consortium Large Earth Finder (G-CLEF) spectrograph for the Giant Magellan Telescope, in a lab at CfA in Cambridge, MA.

Credit: CfA/Casey Atkins

 

Theory of Life

Institute for Theory and Computation scientists at the CfA work on identifying the exoplanets that are most likely to harbor life. The orbit must lie in the “habitable zone” where the exoplanet’s surface is just the right temperature for liquid water to exist. Every form of life we know requires liquid water, so an exoplanet too close or too far from its host star is less likely to contain life. Additionally, ultraviolet light may be needed to form some necessary prebiotic molecules, but an overactive host star can blast the young planet, stripping away its atmosphere. When searching for extraterrestrial life, finding the perfect star could be as important as finding the perfect exoplanet.

 

Our Next Tool 

The G-CLEF or GMT-Consortium Large Earth Finder, a next-generation spectrometer planned for use on the GMT, is our newest tool for measuring the starlight filtered through the atmosphere of an orbiting exoplanet. Using this instrument, scientists will soon be able to measure the chemical composition of a small rocky exoplanet’s atmosphere. Such an extraordinary feat is like trying to see through and study the antennae of a moth flying in front of a spotlight.

Based on our current understanding of the conditions necessary for life, the detection of biomarkers like oxygen in the atmosphere of a remote world through such observations would hint towards the presence of living organisms.

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Our Work

1.3%
Approximate percentage of known exoplanets that might have liquid water on their surface

Scientists and engineers from the Center for Astrophysics aim to achieve the following advances to enable the discovery of life on other planets:

  • Understand the Origins of Life: We investigate the conditions of planetary development that made life’s emergence on Earth possible.
  • Modeling and Instrumentation: We develop new models for the spectroscopic signatures that identify the composition of planetary atmospheres, and build new instruments to detect them.
  • Search and Observation: We identify targeted exoplanet candidates for observation, and continually refine the search process.
  • Data Analysis: We use observational data to infer planetary mass, orbit, size, and composition.

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When we look at our own planet Earth, we see life that abounds everywhere. Do these same conditions exist elsewhere in the Universe? Remarkably, 21st Century science and engineering may soon answer that question.
Dr. Charles Alcock, Director, The Center for Astrophysics

Telescopes and Instruments

1.2 Meter (48-inch) Telescope

The 1.2-Meter (48 Inch) Telescope is a general purpose visible-light telescope located at the Fred Lawrence Whipple Observatory (FLWO), a major observational facility of the Center for Astrophysics | Harvard & Smithsonian located in southern Arizona. Astronomers use this telescope to observe objects in the Solar System and the Milky Way, as well as other galaxies, including the supermassive black holes known as quasars. Astronomers also use the 1.2-Meter Telescope to observe star systems that might contain exoplanets, which is a major program for the observatory.

Visit the 1.2-Meter (48 Inch) Telescope Website
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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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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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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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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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