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NASAβs Fermi Mission Uncovers Possible Sibling Supernova Remnants
A new study of two supernova remnants, the debris left behind after stars explode, suggests the explosions came from stellar siblings that once orbited each other. The first starβs detonation sent its binary companion hurtling through space, and then, after traveling for thousands of years, the surviving star blew up too.
This multiwavelength scene shows the Jellyfish Nebula supernova remnant (right), the interstellar cloud itβs interacting with, and a distinctive curving filament to its upper left. The filament, which is shown here both in optical and ultraviolet (UV) light, is the visible part of an overlapping supernova remnant, G189.6+3.3, that is more prominent in radio and X-rays. Visible light is shown in yellow, UV from NASAβs Neil Gehrels Swift Observatory is shown in violet, and infrared light from NASAβs retired WISE (Wide-field Infrared Survey Explorer) mission appears in cyan, red, and orange. Both remnants are located about 6,000 light-years away in the constellation Gemini. The brilliant star at far right is Propus, also known as Eta Geminorum.
NASA Goddard Space Flight Center and M. Michailidis et al. 2026; optical: DSS; infrared: NASA/WISE/JPL-Caltech/UCLA; ultraviolet: NASA/Swift
βUsing 16 years of data from NASAβs Fermi Gamma-ray Space Telescope, our analysis uncovered gamma rays associated with a supernova remnant that was hidden in the glare of its neighbor, the Jellyfish Nebula, one of the brightest gamma-ray-emitting supernova remnants known,β said Miltiadis Michailidis, a postdoctoral fellow in the physics department at Stanford University in California. βThere are so many striking connections between the two remnants that we conclude theyβre likely related, giving us the first known example of a binary system where both stars have undergone supernova explosions.β
Michailidis presented the findings Wednesday at the 248th meeting of the American Astronomical Society in Pasadena, California. A paper describing the results will appear in a future edition of Nature Communications.
The study focused on a faint supernova remnant called G189.6+3.3, which is mainly visible in X-rays. It is upstaged by its brighter and better-known neighbor, the Jellyfish Nebula (IC 443). The two star wrecks, both located in the constellation Gemini, appear to partially overlap as seen in X-rays. Recent X-ray evidence suggests that hot plasma likely associated with G189.6+3.3 may extend across the entire region, a hint that the overlap may be nearly total.
A massive star explodes when its energy-producing core runs out of fuel and collapses under its own weight, triggering an explosion that blows the star apart. The explosionβs shock wave encloses a hot cloud of debris that rapidly expands into space. So far, astronomers have cataloged about 300 supernova remnants in our galaxy. Β
The Fermi mission is part of NASAβs fleet of observatories monitoring the changing cosmos to help humanity better understand how the universe works. More than a decade ago, observations from Fermiβs LAT (Large Area Telescope) showed that the shock waves of supernova remnants accelerated particles to within a fraction of the speed of light, a process first proposed by physicist Enrico Fermi β the missionβs namesake β in 1949.
These high-speed particles, called cosmic rays, interact with interstellar gas to produce gamma rays, the highest-energy form of light. Protons make up 99% of cosmic ray particles. To prove that accelerated protons are responsible for the glow, astronomers search for a specific gamma-ray feature. When cosmic-ray protons smash into interstellar gas, they produce a short-lived particle called a neutral pion, which almost immediately decays into a pair of gamma rays. This emission occurs within a specific band of energies associated with the neutral pionβs mass and lies within the range detected by Fermiβs LAT instrument.
In 2013, Fermi observations proved that the Jellyfish Nebula, which is interacting with part of a glowing cloud of hydrogen gas known as Sharpless 249, produced gamma rays through this mechanism. Its neighbor, G189.6+3.3, was discovered in 1994 as part of an X-ray survey by the German-led ROSAT (Roentgen Satellite) mission.
A bright filament of gas lies between the overlapping remnants. New observations of this feature reveal that the shock wave from G189.6+3.3 slammed into dense interstellar gas there and dramatically slowed, key evidence that both remnants are interacting with the same cloud system.
The well-known supernova remnant IC 443 (right) has an older, fainter neighbor (shown here in blue-green and magenta) called G189.6+3.3. A filament of gas between them, glowing in visible and ultraviolet light (violet arc at center), traces the neighborβs shock wave and shows that both remnants are interacting with the same molecular cloud, shown in red, orange, brown for infrared and radio data and yellow for visible light. Blue-green shows X-rays from the fainter remnant, while magenta shows gamma rays with energies greater than 10 billion electron volts; for comparison, visible light has energies between about 2 and 3 electron volts. In this view, high-energy light from the much brighter IC 443 has been removed for clarity. Gamma-ray emission near the filament stems from protons accelerated in the supernovaβs shock wave as it expands into the cloud.
NASA Goddard Space Flight Center and M. Michailidis et al. 2026; radio, MWISP and ESA/Planck; infrared: NASA/WISE/JPL-Caltech/UCLA; optical: DSS; ultraviolet: NASA/Swift; X-ray: SRG/eROSITA; gamma ray: NASA/DOE/Fermi LAT Collaboration
Astronomers think the Jellyfish Nebula is also a candidate PeVatron, a cosmic particle accelerator capable of boosting protons to energies so high they could nearly escape our galaxy. Such particles can produce gamma rays with trillions of times more energy than visible light. Finding a second particle accelerator near the Jellyfish Nebula could offer scientists new clues for how supernova remnants develop into PeVatrons.
βThe overlapping remnants, a connecting gas filament, and the availability of data from Fermi and other facilities motivated us to delve into this complex but little-studied region,β said co-author Marianne Lemoine-Goumard, an astrophysicist at the FrenchΒ National Centre for Scientific ResearchΒ (CNRS) based at theΒ University of Bordeaux. βWith Fermiβs LAT instrument, we found gamma-ray emission associated with accelerated protons in the northern part of the fainter remnant. If both remnants are interacting with the same structure, then they must share a common distance from us.β
The team concludes the remnants lie about 6,000 light-years away, their explosion centers are separated by roughly 40 light-years projected onto the plane of the sky, and the original stars may have been 20 or more times the Sunβs mass.
Estimates of the remnantsβ ages vary widely, but the team concludes that the age of the Jellyfish Nebula is 8,000 to 9,000 years, while G189.6+3.3 is between 20,000 to 110,000 years old. This means the delay between the explosions could have extended for up to 100,000 years.
In addition, the team conducted computer simulations of a million massive binary systems. They show that systems where the stars orbit close enough to exchange matter and interact during their lives can readily produce dual supernova explosions with similar separations and time delays as those found for the remnants. The team also estimated that the chance of randomly encountering this combination of observed spatial alignment and compatible distances to be less than 1%, strongly supporting a physical association.
βThe evidence weβve compiled β including observations across the spectrum, the chemical and physical properties of the remnants, simulations, and more β paints a compelling picture of a dual supernova event,β said Michailidis.
This study identifies a unique possible example of a binary system where both stars exploded as supernovae and left behind separate, detectable supernova remnants. Astronomers think that most massive stars form in binary or multiple-star systems. The Jellyfish Nebula/G189.6+3.3 complex offers astronomers a rare opportunity to study how massive binary stars evolve, exchange matter, explode, and experience velocity changes β called kicks β induced by the supernova blast. It also provides a powerful new laboratory for understanding how coupled supernova remnants behave, including how they accelerate particles, generate gamma rays, and shape their surrounding environments.
βFermiβs gamma-ray observations of supernova remnants continue to reveal the dynamic lives of stars,β said Elizabeth Hays, the Fermi project scientist at NASAβs Goddard Space Flight Center in Greenbelt, Maryland.Β βWe can now connect the glowing remains of two massive stars to a powerful pair that evolved together over thousands of years.β
On June 17, in the year 2 B.C.E, a significant planetary conjunction occurred involving Venus and Jupiter. From Earthβs perspective, these two bright planets appeared to draw so close that they would have seemed to merge into nearly a single, brilliant object in the sky. This type of celestial alignment occurs because planets move inContinue reading "June 17, 2 BCE: A conjunction between Venus and Jupiter"
NASA's MAVEN Mars mission ended after 11 years, having revealed how the planet lost its atmosphere and served as a key communications relay for surface missions.
Today (June 17), for the first time in 11 years, people across North America will be able to look up in the daytime sky and see Venus temporarily vanish behind the faint crescent moon.
The rare skywatching spectacle can be viewed with the naked eye and recorded without any special equipment, as long as the weather cooperates β however, using a good pair of binoculars or a backyard telescope will make it much easier to see the faint light of Venus in the daytime sky. No matter how you go about skywatching, you must take great care not to stare directly at the sun while doing so.
During the event, known as a lunar occultation, the moon will briefly pass between Earth and Venus, which has been shining especially bright over the past few weeks while hanging out alongside Jupiter in the evening sky. As a result of the occultation, the hellish planet will appear to blink out of existence, before reappearing around an hour later, allowing for two separate skywatching experiences. The last time this happened was on Dec. 7, 2015, and you will not be able to see it again until 2029.
How to see Venus disappear
The occultation will be visible from the 48 contiguous U.S. states, as well as from large parts of Canada and some countries in the northern half of South America β assuming there are clear skies at the time of the event. (The latest forecast suggests that weather conditions will be most favorable along the West Coast.)
As with most skywatching events, such as solar eclipses, not everyone will see it at the same time. For example, people in San Francisco will observe Venus vanish at around 11:34 a.m. PDT, while those in Miami will watch the planet disappear at about 4:06 p.m. EDT (around 92 minutes later when disregarding time zones).
The duration of the occultation will also vary with location. For example, Venus will reappear after around 58 minutes for viewers in San Antonio, but people in Philadelphia will have to wait roughly 80 minutes to see the planet again.
The best place to watch both the disappearance and reappearance of Venus will be from within the shadow of a large tree or building. Blocking out the sun will not only make it easier to see both the moon and Venus but also reduce the risk of sustaining eye damage by looking directly at the sun.
If you are struggling to see the occultation, try using your phone camera to zoom in on the waxing crescent to better locate and record Venus, Spaceweather.com recommends.
What the June 17 lunar occultation will look like
During the event, around 11% of the moon will be faintly visible in the daytime sky, according to Sky & Telescope. Around three-quarters of Venus will be visible β although it will look like a single spot to the naked eye β so the planet will shine much brighter than the moon. The pair will be collectively located around 38 degrees from the sun in the sky.
Venus will vanish behind the side of the moon opposite the illuminated crescent and will take around 30 seconds to disappear completely. It will then reappear above the crescent, similar to the iconic "Earthrise" photos taken by lunar astronauts, such as the Artemis II crew. (The exact spot where Venus disappears and reappears will depend on where you are in the world.)
If you miss this occultation or fancy another skywatching spectacle, be sure to head back outside later the same day, around an hour after sunset, when Venus, Jupiter and Mercury will shine alongside the crescent moon as it passes in front of the Beehive Cluster (also called M44).
On June 16, 1963, 26-year-old Soviet cosmonaut Valentina Tereshkova made history by becoming the first woman to travel into space. A former factory seamstress, Tereshkova was an accomplished amateur parachutist with over 100 jumps β a vital skill, since Vostok cosmonauts ejected before landing. Selected from over 400 applicants in 1962, she underwent months ofContinue reading "June 16, 1963: Valentina Tereshkova is the first woman in space"
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