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By NASA
Explore This Section Exoplanets Home Exoplanets Overview Exoplanets Facts Types of Exoplanets Stars What is the Universe Search for Life The Big Questions Are We Alone? Can We Find Life? The Habitable Zone Why We Search Target Star Catalog Discoveries Discoveries Dashboard How We Find and Characterize Missions People Exoplanet Catalog Immersive The Exoplaneteers Exoplanet Travel Bureau 5 Ways to Find a Planet Strange New Worlds Universe of Monsters Galaxy of Horrors News Stories Blog Resources Get Involved Glossary Eyes on Exoplanets Exoplanet Watch More Multimedia ExEP This artist’s concept pictures the planets orbiting Barnard’s Star, as seen from close to the surface of one of them. Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld The Discovery
Four rocky planets much smaller than Earth orbit Barnard’s Star, the next closest to ours after the three-star Alpha Centauri system. Barnard’s is the nearest single star.
Key Facts
Barnard’s Star, six light-years away, is notorious among astronomers for a history of false planet detections. But with the help of high-precision technology, the latest discovery — a family of four — appears to be solidly confirmed. The tiny size of the planets is also remarkable: Capturing evidence of small worlds at great distance is a tall order, even using state-of-the-art instruments and observational techniques.
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Watching for wobbles in the light from a star is one of the leading methods for detecting exoplanets — planets orbiting other stars. This “radial velocity” technique tracks subtle shifts in the spectrum of starlight caused by the gravity of a planet pulling its star back and forth as the planet orbits. But tiny planets pose a major challenge: the smaller the planet, the smaller the pull. These four are each between about a fifth and a third as massive as Earth. Stars also are known to jitter and quake, creating background “noise” that potentially could swamp the comparatively quiet signals from smaller, orbiting worlds.
Astronomers measure the back-and-forth shifting of starlight in meters per second; in this case the radial velocity signals from all four planets amount to faint whispers — from 0.2 to 0.5 meters per second (a person walks at about 1 meter per second). But the noise from stellar activity is nearly 10 times larger at roughly 2 meters per second.
How to separate planet signals from stellar noise? The astronomers made detailed mathematical models of Barnard’s Star’s quakes and jitters, allowing them to recognize and remove those signals from the data collected from the star.
The new paper confirming the four tiny worlds — labeled b, c, d, and e — relies on data from MAROON-X, an “extreme precision” radial velocity instrument attached to the Gemini Telescope on the Maunakea mountaintop in Hawaii. It confirms the detection of the “b” planet, made with previous data from ESPRESSO, a radial velocity instrument attached to the Very Large Telescope in Chile. And the new work reveals three new sibling planets in the same system.
Fun Facts
These planets orbit their red-dwarf star much too closely to be habitable. The closest planet’s “year” lasts a little more than two days; for the farthest planet, it’s is just shy of seven days. That likely makes them too hot to support life. Yet their detection bodes well in the search for life beyond Earth. Scientists say small, rocky planets like ours are probably the best places to look for evidence of life as we know it. But so far they’ve been the most difficult to detect and characterize. High-precision radial velocity measurements, combined with more sharply focused techniques for extracting data, could open new windows into habitable, potentially life-bearing worlds.
Barnard’s star was discovered in 1916 by Edward Emerson Barnard, a pioneering astrophotographer.
The Discoverers
An international team of scientists led by Ritvik Basant of the University of Chicago published their paper on the discovery, “Four Sub-Earth Planets Orbiting Barnard’s Star from MAROON-X and ESPRESSO,” in the science journal, “The Astrophysical Journal Letters,” in March 2025. The planets were entered into the NASA Exoplanet Archive on March 13, 2025.
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Last Updated Apr 01, 2025 Related Terms
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Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Posters Hubble on the NASA App Glossary More 35th Anniversary Online Activities 5 Min Read 20-Year Hubble Study of Uranus Yields New Atmospheric Insights
The image columns show the change of Uranus for the four years that STIS observed Uranus across a 20-year period. Over that span of time, the researchers watched the seasons of Uranus as the south polar region darkened going into winter shadow while the north polar region brightened as northern summer approaches. Credits:
NASA, ESA, Erich Karkoschka (LPL) The ice-giant planet Uranus, which travels around the Sun tipped on its side, is a weird and mysterious world. Now, in an unprecedented study spanning two decades, researchers using NASA’s Hubble Space Telescope have uncovered new insights into the planet’s atmospheric composition and dynamics. This was possible only because of Hubble’s sharp resolution, spectral capabilities, and longevity.
The team’s results will help astronomers to better understand how the atmosphere of Uranus works and responds to changing sunlight. These long-term observations provide valuable data for understanding the atmospheric dynamics of this distant ice giant, which can serve as a proxy for studying exoplanets of similar size and composition.
When Voyager 2 flew past Uranus in 1986, it provided a close-up snapshot of the sideways planet. What it saw resembled a bland, blue-green billiard ball. By comparison, Hubble chronicled a 20-year story of seasonal changes from 2002 to 2022. Over that period, a team led by Erich Karkoschka of the University of Arizona, and Larry Sromovsky and Pat Fry from the University of Wisconsin used the same Hubble instrument, STIS (the Space Telescope Imaging Spectrograph), to paint an accurate picture of the atmospheric structure of Uranus.
Uranus’ atmosphere is mostly hydrogen and helium, with a small amount of methane and traces of water and ammonia. The methane gives Uranus its cyan color by absorbing the red wavelengths of sunlight.
The Hubble team observed Uranus four times in the 20-year period: in 2002, 2012, 2015, and 2022. They found that, unlike conditions on the gas giants Saturn and Jupiter, methane is not uniformly distributed across Uranus. Instead, it is strongly depleted near the poles. This depletion remained relatively constant over the two decades. However, the aerosol and haze structure changed dramatically, brightening significantly in the northern polar region as the planet approaches its northern summer solstice in 2030.
The image columns show the change of Uranus for the four years that STIS observed Uranus across a 20-year period. Over that span of time, the researchers watched the seasons of Uranus as the south polar region darkened going into winter shadow while the north polar region brightened as northern summer approaches. NASA, ESA, Erich Karkoschka (LPL) Uranus takes a little over 84 Earth years to complete a single orbit of the Sun. So, over two decades, the Hubble team has only seen mostly northern spring as the Sun moves from shining directly over Uranus’ equator toward shining almost directly over its north pole in 2030. Hubble observations suggest complex atmospheric circulation patterns on Uranus during this period. The data that are most sensitive to the methane distribution indicate a downwelling in the polar regions and upwelling in other regions.
The team analyzed their results in several ways. The image columns show the change of Uranus for the four years that STIS observed Uranus across a 20-year period. Over that span of time, the researchers watched the seasons of Uranus as the south polar region (left) darkened going into winter shadow while the north polar region (right) brightened as it began to come into a more direct view as northern summer approaches.
The top row, in visible light, shows how the color of Uranus appears to the human eye as seen through even an amateur telescope.
In the second row, the false-color image of the planet is assembled from visible and near-infrared light observations. The color and brightness correspond to the amounts of methane and aerosols. Both of these quantities could not be distinguished before Hubble’s STIS was first aimed at Uranus in 2002. Generally, green areas indicate less methane than blue areas, and red areas show no methane. The red areas are at the limb, where the stratosphere of Uranus is almost completely devoid of methane.
The two bottom rows show the latitude structure of aerosols and methane inferred from 1,000 different wavelengths (colors) from visible to near infrared. In the third row, bright areas indicate cloudier conditions, while the dark areas represent clearer conditions. In the fourth row, bright areas indicate depleted methane, while dark areas show the full amount of methane.
At middle and low latitudes, aerosols and methane depletion have their own latitudinal structure that mostly did not change much over the two decades of observation. However, in the polar regions, aerosols and methane depletion behave very differently.
In the third row, the aerosols near the north pole display a dramatic increase, showing up as very dark during early northern spring, turning very bright in recent years. Aerosols also seem to disappear at the left limb as the solar radiation disappeared. This is evidence that solar radiation changes the aerosol haze in the atmosphere of Uranus. On the other hand, methane depletion seems to stay quite high in both polar regions throughout the observing period.
Astronomers will continue to observe Uranus as the planet approaches northern summer.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
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20 Years of Uranus Observations
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Last Updated Mar 31, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center
Contact Media Claire Andreoli
NASA’s Goddard Space Flight Center
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claire.andreoli@nasa.gov
Ann Jenkins
Space Telescope Science Institute, Baltimore, Maryland
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
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By NASA
On March 24, 1975, the last in a long line of super successful Saturn rockets rolled out from the vehicle assembly building to Launch Pad 39B at NASA’s Kennedy Space Center in Florida. The Saturn IB rocket for the Apollo-Soyuz Test Project was the 19th in the Saturn class stacked in the assembly building, beginning in 1966 with the Saturn V 500F facilities checkout vehicle. Thirteen flight Saturn V rockets followed, 12 to launch Apollo spacecraft and one to place the Skylab space station into orbit. In addition, workers stacked four flight Saturn IB rockets, three to launch crews to Skylab and one for Apollo-Soyuz, plus another for the Skylab rescue vehicle that was not needed and never launched. Previously, workers stacked Saturn I and Saturn IB rockets on the pads at Launch Complexes 34 and 37. With the successful liftoff in July 1975, the Saturn family of rockets racked up a 100 percent success rate of 32 launches.
Workers lower the Apollo command and service modules onto the spacecraft adaptor.NASA Technicians in the assembly building replace the fins on the Saturn IB rocket’s first stage. NASA Workers in the assembly building prepare to lower the spacecraft onto its Saturn IB rocket.NASA Inspections of the Saturn IB rocket’s first stage fins revealed hairline cracks in several hold-down fittings and managers ordered the replacement of all eight fins. While the cracks would not affect the flight of the rocket they bore the weight of the rocket on the mobile launcher. Workers finished the fin replacement on March 16. Engineers in Kennedy’s spacecraft operations building prepared the Apollo spacecraft for its historic space mission. By early March, they had completed checkout and assembly of the spacecraft and transported it to the assembly building on March 17 to mount it atop the Saturn IB’s second stage. Five days later, they topped off the rocket with the launch escape system.
The final Saturn IB begins its rollout from the vehicle assembly building. NASA The Saturn IB passes by the Launch Control Center. NASA Apollo astronauts Thomas Stafford, left, Vance Brand, and Donald “Deke” Slayton pose in front of their Saturn IB during the rollout.NASA On March 23, workers edged the mobile transporter carrying the Saturn IB just outside the assembly building’s High Bay 1, where engineers installed an 80-foot tall lightning mast atop the launch tower. The next morning, the stack continued its rollout to Launch Pad 39B with the prime crew of Thomas Stafford, Vance Brand, and Donald “Deke” Slayton and support crew members Robert Crippen and Richard Truly on hand to observe. About 7,500 people, including guests, dependents of Kennedy employees and NASA Tours patrons, watched as the stack moved slowly out of the assembly building on its five-mile journey to the launch pad.
Mission Control in Houston during the joint simulation with Flight Director Donald Puddy in striped shirt and a view of Mission Control in Moscow on the large screen at left. NASA A group of Soviet flight controllers in a support room in Mission Control in Houston during the joint simulation. NASA On March 20, flight controllers and crews began a series of joint simulations for the joint mission scheduled for July 1975. For the six days of simulations, cosmonauts Aleksei Leonov and Valeri Kubasov and astronauts Stafford, Brand, and Slayton participated in the activity in spacecraft simulators in their respective countries, with both control centers in Houston and outside Moscow fully staffed as if for the actual mission. The exercises simulated various phases of the mission, including the respective launches, rendezvous and docking, crew transfers and joint operations, and undocking.
Astronauts Thomas Stafford, left, Vance Brand, and Donald “Deke” Slayton in a boilerplate Apollo command module preparing for the water egress training. NASA Stafford, left, Slayton, and Brand in the life raft during water egress training. NASA Astronauts Stafford, Brand and Slayton participated in a water egress training activity on March 8, completing the exercise in a water tank in Building 260 at NASA’s Johnson Space Center in Houston. The astronauts practiced egressing from their spacecraft onto a lift raft and being lifted up with the use of a Billy Pugh rescue net. They practiced wearing their flight coveralls as well as their spacesuits.
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
A NASA researcher and innovation architect from the Convergent Aeronautics Solutions project Discovery team collaborating at a whiteboard during a visit to Chapel Hill, N.C. on Aug. 13, 2024.NASA / Ariella Knight Convergent Aeronautics Solutions (CAS) Discovery identifies problems worth solving for the benefit of all.
We formulate “convergent” problems—across multiple disciplines and sectors—and build footholds toward potentially transformative opportunities in aeronautics. As aeronautics rapidly advances, it is increasingly intersecting with other sectors like energy, healthcare, emergency response, economic resilience, the space economy, and more.
CAS Discovery builds new innovation tools and methods, a workforce adept at innovation methods, and transdisciplinary teams of researchers within and beyond NASA that conduct regular “Discovery sprints”—expeditions into cross-sector topic areas that could beneficially transform aeronautics and humanity.
WHAT is Discovery?
Participatory
It is difficult to understand and effectively address stakeholders’ needs & capabilities without engaging them. Discovery, in consultation with key NASA offices and other government agencies, has honed mechanisms to lawfully and respectfully engage and invite participation from stakeholders, communities, industry, NGOs and government to collaboratively formulate complex societal challenges tied to aviation.
Convergent
Typical organizational structures limit convergence across knowledge boundaries. CAS Discovery is intentionally cross-sector and transdisciplinary because the most impactful ideas often lie at the intersection of boundaries, the borderlands where multiple disciplines and communities come together. We work to emerge multi-sector, system-of-systems challenges that integrate political, economic, social, technological, environmental, legal and ethical trends, needs, and capabilities.
Future-Focused
Organizations have a tendency of being driven by short-term thinking and relatively short time horizons. CAS Discovery uses strategic foresight methods to examine 20 to 50-year time horizons, systematically ingesting and synthesizing signals and trends from aero and non-aero sources to envision a variety of scenarios to uncover opportunities for the future of aeronautics.
Ecosystemic
We study the ecosystems that are part of aeronautics and aerospace. This helps in broadening consideration of impacts while practicing foresight. It enhances our awareness of the environment and gives stakeholders the ability to see ripple effects across technologies, economies, communities, etc. We seek to benefit the wellness of the entire ecosystem while also benefiting the constituents.
A group of NASA researchers and leaders from the Convergent Aeronautics Solutions project Discovery team at the agency’s Glenn Research Center in Cleveland, on April 30, 2024.NASA / Ricaurte Chock WHO is Discovery?
NASA Researchers
They are the engine that propels CAS Discovery. Our cross-center Discovery sprint and foresight teams are composed of researchers from NASA’s Ames Research Center and Armstrong Flight Research Center in California, Glenn Research Center in Cleveland, and Langley Research Center in Virginia.
Researchers from Outside of NASA
They collaborate with us as subject matter experts or Discovery sprint team members to contribute their backgrounds in fields less common within NASA, such as energy, economics, anthropology, and other areas. This collaboration happens through many mechanisms, such as freelancing, crowdsourcing, interviews, webinars, and podcasts.
Stakeholders
They are engaged in various ways and to different degrees, often co-envisioning potential futures, co-formulating problems, and co-designing solutions.
Innovation Architects
They are the glue that holds CAS Discovery together and the anti-glue that keeps our teams from getting stuck. They come from a wide range of experience, each bringing deep expertise in leading transdisciplinary teams and stakeholders through processes and methods from strategic foresight, complex systems design, human-centered design, and more.
CAS Center Integration Leads (CILs)
They work with NASA line management at each Aeronautics center to bring NASA researchers and potential new PIs into CAS. CILs also host annual Wicked Wild idea pitch events to bring new problem areas and solution ideas into CAS Discovery and early Execution phases.
Ames Research Center CIL: Ty Huang Armstrong Flight Research Center CIL: Matt Kearns Glenn Research Center CIL: Jeffrey Chin Langley Research Center CIL: Devin Pugh-Thomas CAS Discovery Leads
They oversee Discovery sprint and strategic foresight teams, topics, and processes; new tools and continuous improvement experiments; and the overall health of the CAS innovation front-end pipeline and related strategic outputs.
Discovery Lead: Eric Reynolds Brubaker, Langley Research Center Foresight Lead: Vikram Shyam, Glenn Research Center Sample Discovery Publications
COMING SOON: Links to Technical Memorandums and conference papers.
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Last Updated Mar 21, 2025 EditorJim BankeContactDiana Fitzgeralddiana.r.fitzgerald@nasa.gov Related Terms
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By NASA
Artist’s rendering of a potentially habitable super-Earth orbiting a star called HD 20794. Illustration credit: Gabriel Pérez Díaz, SMM (IAC) The Discovery
A possible “super-Earth” orbits a relatively close, Sun-like star, and could be a habitable world – but one of extreme temperature swings, from scorching heat to deep freeze.
Key Facts
The newly confirmed planet is the outermost of three detected so far around a star called HD 20794, just 20 light-years from Earth. Its 647-day orbit is comparable to Mars in our solar system. But this planet’s orbit is highly eccentric, stretched into an oval shape. That brings the planet close enough to the star to experience runaway heating for part of its year, then carries it far enough away to freeze any potential water on its surface. The planet has been bouncing between these extremes roughly every 300 days – perhaps for billions of years.
Details
The planet spends a good chunk of its year in the “habitable zone” around its star, the orbital distance that would allow liquid water to form on the surface under the right atmospheric conditions. But because of its eccentric orbit, it moves to a distance interior to the inner edge of the habitable zone when closest to the star, and outside the outer edge when farthest away. At its closest, the planet’s distance from the star is comparable to Venus’s distance from the Sun; at its farthest point, it is nearly twice the distance from Earth to the Sun. The planet is possibly rocky, like Earth, but could be a heftier version – about six times as massive as our home planet.
Star HD 20794 and its posse of possible planets have been extensively studied, but the international team of astronomers that confirmed the outer planet, led by Nicola Nari of Light Bridges S.L. and the Instituto de Astrofisica de Canarias, examined more than 20 years worth of data to pin down all three planets’ orbits and likely masses.
The scientists relied on data from two ground-based, precision instruments: HARPS, the High Accuracy Radial velocity Planet Searcher in La Silla, Chile, and ESPRESSO, the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations in Paranal, Chile. Both instruments, connected to powerful telescopes, measure tiny shifts in the light spectrum of stars, caused by the gravity of planets tugging the star back and forth as they orbit.
But such tiny shifts in the star’s spectrum also can be caused by imposters – spots, flares, or other activity on the star’s surface, carried along as the star rotates and masquerading as orbiting planets. The science team spent years painstakingly analyzing the spectrum shifts, or “radial velocity” data, for any sign of background noise or even jitters from the instruments themselves. They confirmed the reputation of HD 20794 as a fairly quiet star, not prone to outbursts that might be confused for signs of orbiting planets.
Fun Facts
The elliptically orbiting super-Earth appears to be an ideal target for future space-based telescopes designed to search for habitable worlds, seeking possible signs of life. High on the list is NASA’s Habitable Worlds Observatory, which will someday examine the atmospheres of Earth-sized planets around Sun-like stars. When launched in the decades ahead, the observatory would spread the light from such planets into a spectrum to determine which gases are present – including those that might reveal some form of life. The relative closeness of HD 20974, only 20 light-years away, its brightness, and its low level of surface activity – not to mention the third planet’s wild temperature swings – could make this system a prime candidate for scrutiny by HWO.
The Discoverers
The international science team that confirmed the eccentric super-Earth was led by researcher Nicola Nari of the Light Bridges S.L. and the Instituto de Astrofisica de Canarias, and included Dr. Michael Cretignier of the University of Oxford, who first picked up the potential planet’s signal in 2022. Their paper, “Revisiting the multi-planet system of the nearby star HD 20794,” was published online by the journal, Astronomy and Astrophysics, in January 2025.
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