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By European Space Agency
Astronomers using the NASA/ESA/CSA James Webb Space Telescope have found strong evidence of a giant planet orbiting a star in the stellar system closest to our own Sun. At just 4 light-years away from Earth, the Alpha Centauri triple star system has long been a compelling target in the search for worlds beyond our solar system.
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By NASA
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This artist’s concept shows what a gas giant orbiting Alpha Centauri A could look like. Observations of the triple star system Alpha Centauri using NASA’s James Webb Space Telescope indicate the potential gas giant, about the mass of Saturn, orbiting the star by about two times the distance between the Sun and Earth. Full illustration and caption shown below. Credits:
Artwork: NASA, ESA, CSA, STScI, R. Hurt (Caltech/IPAC) Astronomers using NASA’s James Webb Space Telescope have found strong evidence of a giant planet orbiting a star in the stellar system closest to our own Sun. At just 4 light-years away from Earth, the Alpha Centauri triple star system has long been a compelling target in the search for worlds beyond our solar system.
Visible only from Earth’s Southern hemisphere, it’s made up of the binary Alpha Centauri A and Alpha Centauri B, both Sun-like stars, and the faint red dwarf star Proxima Centauri. Alpha Centauri A is the third brightest star in the night sky. While there are three confirmed planets orbiting Proxima Centauri, the presence of other worlds surrounding Alpha Centauri A and Alpha Centauri B has proved challenging to confirm.
Now, Webb’s observations from its Mid-Infrared Instrument (MIRI) are providing the strongest evidence to date of a gas giant orbiting Alpha Centauri A. The results have been accepted in a series of two papers in The Astrophysical Journal Letters.
If confirmed, the planet would be the closest to Earth that orbits in the habitable zone of a Sun-like star. However, because the planet candidate is a gas giant, scientists say it would not support life as we know it.
“With this system being so close to us, any exoplanets found would offer our best opportunity to collect data on planetary systems other than our own. Yet, these are incredibly challenging observations to make, even with the world’s most powerful space telescope, because these stars are so bright, close, and move across the sky quickly,” said Charles Beichman, NASA’s Jet Propulsion Laboratory and the NASA Exoplanet Science Institute at Caltech’s IPAC astronomy center, co-first author on the new papers. “Webb was designed and optimized to find the most distant galaxies in the universe. The operations team at the Space Telescope Science Institute had to come up with a custom observing sequence just for this target, and their extra effort paid off spectacularly.”
Image A: Alpha Centauri 3 Panel (DSS, Hubble, Webb)
This image shows the Alpha Centauri star system from several different ground- and space-based observatories: the Digitized Sky Survey (DSS), NASA’s Hubble Space Telescope, and NASA’s James Webb Space Telescope. Alpha Centauri A is the third brightest star in the night sky, and the closest Sun-like star to Earth. The ground-based image from DSS shows the triple system as a single source of light, while Hubble resolves the two Sun-like stars in the system, Alpha Centauri A and Alpha Centauri B. The image from Webb’s MIRI (Mid-Infrared Instrument), which uses a coronagraphic mask to block the bright glare from Alpha Centauri A, reveals a potential planet orbiting the star. Science: NASA, ESA, CSA, STScI, DSS, A. Sanghi (Caltech), C. Beichman (NExScI, NASA/JPL-Caltech), D. Mawet (Caltech); Image Processing: J. DePasquale (STScI) Several rounds of meticulously planned observations by Webb, careful analysis by the research team, and extensive computer modeling helped determine that the source seen in Webb’s image is likely to be a planet, and not a background object (like a galaxy), foreground object (a passing asteroid), or other detector or image artifact.
The first observations of the system took place in August 2024, using the coronagraphic mask aboard MIRI to block Alpha Centauri A’s light. While extra brightness from the nearby companion star Alpha Centauri B complicated the analysis, the team was able to subtract out the light from both stars to reveal an object over 10,000 times fainter than Alpha Centauri A, separated from the star by about two times the distance between the Sun and Earth.
Image B: Alpha Centauri 3 Panel (Webb MIRI Image Detail)
This three-panel image captures NASA’s James Webb Space Telescope’s observational search for a planet around the nearest Sun-like star, Alpha Centauri A. The initial image shows the bright glare of Alpha Centauri A and Alpha Centauri B, and the middle panel then shows the system with a coronagraphic mask placed over Alpha Centauri A to block its bright glare. However, the way the light bends around the edges of the coronagraph creates ripples of light in the surrounding space. The telescope’s optics (its mirrors and support structures) cause some light to interfere with itself, producing circular and spoke-like patterns. These complex light patterns, along with light from the nearby Alpha Centauri B, make it incredibly difficult to spot faint planets. In the panel at the right, astronomers have subtracted the known patterns (using reference images and algorithms) to clean up the image and reveal faint sources like the candidate planet. Science: NASA, ESA, CSA, STScI, A. Sanghi (Caltech), C. Beichman (NExScI, NASA/JPL-Caltech), D. Mawet (Caltech); Image Processing: J. DePasquale (STScI) While the initial detection was exciting, the research team needed more data to come to a firm conclusion. However, additional observations of the system in February 2025 and April 2025 (using Director’s Discretionary Time) did not reveal any objects like the one identified in August 2024.
“We are faced with the case of a disappearing planet! To investigate this mystery, we used computer models to simulate millions of potential orbits, incorporating the knowledge gained when we saw the planet, as well as when we did not,” said PhD student Aniket Sanghi of Caltech in Pasadena, California. Sanghi is a co-first author on the two papers covering the team’s research.
In these simulations, the team took into account both a 2019 sighting of the potential exoplanet candidate by the European Southern Observatory’s Very Large Telescope, the new data from Webb, and considered orbits that would be gravitationally stable in the presence of Alpha Centauri B, meaning the planet wouldn’t get flung out of the system.
Researchers say a non-detection in the second and third round of observations with Webb isn’t surprising.
“We found that in half of the possible orbits simulated, the planet moved too close to the star and wouldn’t have been visible to Webb in both February and April 2025,” said Sanghi.
Image C: Alpha Centauri A Planet Candidate (Artist’s Concept)
This artist’s concept shows what a gas giant orbiting Alpha Centauri A could look like. Observations of the triple star system Alpha Centauri using NASA’s James Webb Space Telescope indicate the potential gas giant, about the mass of Saturn, orbiting the star by about two times the distance between the Sun and Earth. In this concept, Alpha Centauri A is depicted at the upper left of the planet, while the other Sun-like star in the system, Alpha Centauri B, is at the upper right. Our Sun is shown as a small dot of light between those two stars. Artwork: NASA, ESA, CSA, STScI, R. Hurt (Caltech/IPAC) Based on the brightness of the planet in the mid-infrared observations and the orbit simulations, researchers say it could be a gas giant approximately the mass of Saturn orbiting Alpha Centauri A in an elliptical path varying between 1 to 2 times the distance between Sun and Earth.
“If confirmed, the potential planet seen in the Webb image of Alpha Centauri A would mark a new milestone for exoplanet imaging efforts,” Sanghi says. “Of all the directly imaged planets, this would be the closest to its star seen so far. It’s also the most similar in temperature and age to the giant planets in our solar system, and nearest to our home, Earth,” he says. “Its very existence in a system of two closely separated stars would challenge our understanding of how planets form, survive, and evolve in chaotic environments.”
If confirmed by additional observations, the team’s results could transform the future of exoplanet science.
“This would become a touchstone object for exoplanet science, with multiple opportunities for detailed characterization by Webb and other observatories,” said Beichman.
For example, NASA’s Nancy Grace Roman Space Telescope, set to launch by May 2027 and potentially as early as fall 2026, is equipped with dedicated hardware that will test new technologies to observe binary systems like Alpha Centauri in search of other worlds. Roman’s visible light data would complement Webb’s infrared observations, yielding unique insights on the size and reflectivity of the planet.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
To learn more about Webb, visit:
https://science.nasa.gov/webb
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By NASA
NASA/JPL-Caltech/MSSS The United States flag adorns an aluminum plate mounted at the base of the mast, or “head,” of NASA’s Perseverance Mars rover. This image of the plate was taken on June 28, 2025 (the 1,548th day, or sol, of the mission), by the WATSON (Wide Angle Topographic Sensor for Operations and eNgineering) camera on the end of the rover’s robotic arm.
WATSON, part of an instrument called SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals), was built by Malin Space Science Systems (MSSS) in San Diego and is operated jointly by MSSS and NASA’s Jet Propulsion Laboratory in Southern California. JPL, which is managed for the agency by Caltech, built and manages operations of the Perseverance rover.
Learn more about Perseverance’s latest science.
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By NASA
This artist’s concept animation shows the orbital dynamics of KOI-134 system which, in 2025, a paper revealed to have two planets: KOI-134 b and KOI-134 c. NASA/JPL-Caltech/K. Miller (Caltech/IPAC) The Planets
KOI-134 b and KOI-134 c
This artist’s concept shows the KOI-134 system which, in 2025, a paper revealed to have two planets: KOI-134 b and KOI-134 c. NASA/JPL-Caltech/K. Miller (Caltech/IPAC) The Discovery
A new investigation into old Kepler data has revealed that a planetary system once thought to house zero planets actually has two planets which orbit their star in a unique style, like an old-fashioned merry-go-round.
Key Facts
The KOI-134 system contains two planets which orbit their star in a peculiar fashion on two different orbital planes, with one planet exhibiting significant variation in transit times. This is the first-discovered system of its kind.
Details
Over a decade ago, scientists used NASA’s Kepler Space Telescope to observe the KOI-134 system and thought that it might have a planet orbiting, but they deemed this planet candidate to be a false positive, because its transits (or passes in front of its star) were not lining up as expected. These transits were so abnormal that the planet was actually weeded out through an automated system as a false positive before it could be analyzed further.
However, NASA’s commitment to openly sharing scientific data means that researchers can constantly revisit old observations to make new discoveries. In this new study, researchers re-analyzed this Kepler data on KOI-134 and confirmed that not only is the “false positive” actually a real planet, but the system has two planets and some really interesting orbital dynamics!
First, the “false positive” planet, named KOI-134 b, was confirmed to be a warm Jupiter (or a warm planet of a similar size to Jupiter). Through this analysis, researchers uncovered that the reason this planet eluded confirmation previously is because it experiences what are called transit timing variations (TTVs), or small differences in a planet’s transit across its star that can make its transit “early” or “late” because the planet is being pushed or pulled by the gravity from another planet which was also revealed in this study. Researchers estimate that KOI-134 b transits across its star as much as 20 hours “late” or “early,” which is a significant variation. In fact, it was so significant that it’s the reason why the planet wasn’t confirmed in initial observations.
As these TTVs are caused by the gravitational interaction with another planet, this discovery also revealed a planetary sibling: KOI-134 c. Through studying this system in simulations that include these TTVs, the team found that KOI-134 c is a planet slightly smaller than Saturn and closer to its star than KOI-134 b.
This artist’s concept shows the KOI-134 system which, in 2025, a paper revealed to have two planets: KOI-134 b and KOI-134 c. NASA/JPL-Caltech/K. Miller (Caltech/IPAC) KOI-134 c previously eluded observation because it orbits on a tilted orbital plane, a different plane from KOI-134 b, and this tilted orbit prevents the planet from transiting its star. The two orbital planes of these planets are about 15 degrees different from one another, also known as a mutual inclination of 15 degrees, which is significant. Due to the gravitational push and pull between these two planets, their orbital planes also tilt back and forth.
Another interesting feature of this planetary system is something called resonance. These two planets have a 2 to 1 resonance, meaning within the same time that one planet completes one orbit, the other completes two orbits. In this case, KOI-134 b has an orbital period (the time it takes a planet to complete one orbit) of about 67 days, which is twice the orbital period of KOI-134 c, which orbits every 33-34 days.
Between the separate orbital planes tilting back and forth, the TTVs, and the resonance, the two planets orbit their star in a pattern that resembles two wooden ponies bobbing up and down as they circle around on an old-fashioned merry go round.
Fun Facts
While this system started as a false positive with Kepler, this re-analysis of the data reveals a vibrant system with two planets. In fact, this is the first-ever discovered compact, multiplanetary system that isn’t flat, has such a significant TTV, and experiences orbital planes tilting back and forth.
Also, most planetary systems do not have high mutual inclinations between close planet pairs. In addition to being a rarity, mutual inclinations like this are also not often measured because of challenges within the observation process. So, having measurements like this of a significant mutual inclination in a system, as well as measurements of resonance and TTVs, provides a clear picture of dynamics within a planetary system which we are not always able to see.
The Discoverers
A team of scientists led by Emma Nabbie of the University of Southern Queensland published a paper on June 27 on their discovery, “A high mutual inclination system around KOI-134 revealed by transit timing variations,” in the journal “Nature Astronomy.” The observations described in this paper and used in simulations in this paper were made by NASA’s Kepler Space Telescope and the paper included collaboration and contributions from institutions including the University of Geneva, University of La Laguna, Purple Mountain Observatory, the Harvard-Smithsonian Center for Astrophysics, the Georgia Institute of Technology, the University of Southern Queensland, and NASA’s retired Kepler Space Telescope.
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By NASA
Artist’s concept of the star HIP 67522 with a flare erupting toward an orbiting planet, HIP 67522 b. A second planet, HIP 67522 c, is shown in the background. Janine Fohlmeister, Leibniz Institute for Astrophysics Potsdam The Discovery
A giant planet some 400 light-years away, HIP 67522 b, orbits its parent star so tightly that it appears to cause frequent flares from the star’s surface, heating and inflating the planet’s atmosphere.
Key Facts
On planet Earth, “space weather” caused by solar flares might disrupt radio communications, or even damage satellites. But Earth’s atmosphere protects us from truly harmful effects, and we orbit the Sun at a respectable distance, out of reach of the flares themselves.
Not so for planet HIP 67522 b. A gas giant in a young star system – just 17 million years old – the planet takes only seven days to complete one orbit around its star. A “year,” in other words, lasts barely as long as a week on Earth. That places the planet perilously close to the star. Worse, the star is of a type known to flare – especially in their youth.
In this case, the proximity of the planet appears to result in fairly frequent flaring.
Details
The star and the planet form a powerful but likely a destructive bond. In a manner not yet fully understood, the planet hooks into the star’s magnetic field, triggering flares on the star’s surface; the flares whiplash energy back to the planet. Combined with other high-energy radiation from the star, the flare-induced heating appears to have increased the already steep inflation of the planet’s atmosphere, giving HIP 67522 b a diameter comparable to our own planet Jupiter despite having just 5% of Jupiter’s mass.
This might well mean that the planet won’t stay in the Jupiter size-range for long. One effect of being continually pummeled with intense radiation could be a loss of atmosphere over time. In another 100 million years, that could shrink the planet to the status of a “hot Neptune,” or, with a more radical loss of atmosphere, even a “sub-Neptune,” a planet type smaller than Neptune that is common in our galaxy but lacking in our solar system.
Fun Facts
Four hundred light-years is much too far away to capture images of stellar flares striking orbiting planets. So how did a science team led by Netherlands astronomer Ekaterina Ilin discover this was happening? They used space-borne telescopes, NASA’s TESS (Transiting Exoplanet Survey Satellite) and the European Space Agency’s CHEOPS (CHaracterising ExoPlanets Telescope), to track flares on the star, and also to trace the path of the planet’s orbit.
Both telescopes use the “transit” method to determine the diameter of a planet and the time it takes to orbit its star. The transit is a kind of mini-eclipse. As the planet crosses the star’s face, it causes a tiny dip in starlight reaching the telescope. But the same observation method also picks up sudden stabs of brightness from the star – the stellar flares. Combining these observations over five years’ time and applying rigorous statistical analysis, the science team revealed that the planet is zapped with six times more flares than it would be without that magnetic connection.
The Discoverers
A team of scientists from the Netherlands, Germany, Sweden, and Switzerland, led by Ekaterina Ilin of the Netherlands Institute for Radio Astronomy, published their paper on the planet-star connection, “Close-in planet induces flares on its host star,” in the journal Nature on July 2, 2025.
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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 View the full article
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