Across a distance of 28 million light-years, humanity's gaze has reached beyond its own galactic home for the first time. Using the Chandra X-ray Observatory, astronomers detected a fleeting dimming in the Whirlpool Galaxy that may be a Saturn-sized planet transiting a black hole or neutron star — a signal lasting just three hours, yet carrying implications that stretch across the whole of cosmic history. Though confirmation may take decades, the discovery reminds us that the universe's two trillion galaxies may each harbor worlds as numerous and varied as our own.
NASA detects first potential exoplanet outside Milky Way in distant galaxy
The first hint that planets exist far beyond our own
Mark
Why does finding a planet outside the Milky Way matter so much? We've found thousands of exoplanets already.
Mimi
Because those 4,000-plus planets are all in our backyard, cosmically speaking. This one is 28 million light-years away. It's the first evidence that planets aren't just a Milky Way phenomenon—they're everywhere.
Luke
But it's still just a candidate, right? One transit observation?
Mimi
Yes. One three-hour transit that showed up as a dip in X-rays. That's the entire evidence base.
Mark
How confident are they that it's actually a planet?
Mimi
Confident enough to publish, but not confident enough to call it confirmed. They're being careful with the language.
Luke
And we won't know for 70 years if they're right?
Mimi
Not unless the planet transits again. The orbit is so wide that it won't cross in front of the star for seven decades.
Mark
So this is really a beginning, not an ending.
Mimi
Exactly. It's a door opening. It suggests the method works, that we can detect planets in other galaxies if we look hard enough.
Luke
Using X-rays instead of visible light—is that a new technique?
Mimi
New application, anyway. Most exoplanet detection looks for dips in visible light. This team realized X-ray transits might be easier to spot in distant galaxies.
Le Pouls
- A three-hour dip in X-ray brightness from a galaxy 28 million light-years away has set the astronomy community alight with a possibility no one has confirmed before: a planet beyond the Milky Way.
- Every one of the 4,000-plus exoplanets catalogued since 1988 has been a neighbor by cosmic standards — all within 3,000 light-years — making this candidate an almost incomprehensible leap in scale.
- The planet's suspected orbit around a black hole or neutron star adds another layer of strangeness, placing it in one of the most extreme environments scientists have ever considered as a home for a world.
- Verification is the cruel catch: the planet won't cross its host again for roughly 70 years, leaving researchers to sit with a tantalizing signal they cannot quickly corroborate.
- The team is pressing forward with additional observations, knowing that even the act of watching — and waiting — is itself a milestone in the long human project of mapping what lies beyond.
Across a distance of 28 million light-years, humanity's gaze has reached beyond its own galactic home for the first time. Using the Chandra X-ray Observatory, astronomers detected a fleeting dimming in the Whirlpool Galaxy that may be a Saturn-sized planet transiting a black hole or neutron star — a signal lasting just three hours, yet carrying implications that stretch across the whole of cosmic history. Though confirmation may take decades, the discovery reminds us that the universe's two trillion galaxies may each harbor worlds as numerous and varied as our own.
For the first time, astronomers believe they have glimpsed a planet orbiting a star in another galaxy. The signal came through NASA's Chandra X-ray Observatory, which detected a brief dip in X-ray brightness within the Whirlpool Galaxy — Messier 51 — some 28 million light-years from Earth. Unlike the visible-light transits used to find planets closer to home, this detection relied on X-ray emissions, revealing what may be a Saturn-sized world passing in front of a black hole or neutron star at roughly twice Saturn's distance from our Sun.
The research team, led by Rosanne Di Stefano at the Center for Astrophysics in Cambridge, Massachusetts, had been searching precisely for this kind of interruption in high-energy radiation. The transit lasted about three hours — a fleeting whisper from an almost unimaginable distance.
The significance is hard to overstate. More than 4,000 exoplanets have been confirmed within the Milky Way, yet all of them lie within 3,000 light-years of Earth. In a universe that may contain two trillion galaxies, each potentially harboring hundreds of billions of planets, finding even one candidate beyond our own galaxy feels like a threshold crossed.
Yet patience will be the price of certainty. The candidate planet won't transit its host again for approximately 70 years, and catching that future crossing will require knowing exactly when and where to look. For now, the discovery stands as a first hint — provisional, extraordinary, and quietly humbling — that the universe's other galaxies are not empty stages, but worlds waiting to be found.
For the first time, astronomers believe they have spotted a planet orbiting a star beyond the Milky Way. The detection came through the Chandra X-ray Observatory, which captured what appears to be a planetary transit in the Whirlpool Galaxy, a spiral galaxy situated roughly 28 million light-years from Earth. The transit—the moment when a planet passes in front of its star and dims the light reaching us—lasted about three hours and showed up as a dip in X-ray brightness rather than visible light.
The research team, led by Rosanne Di Stefano at the Center for Astrophysics in Cambridge, Massachusetts, was hunting for exactly this kind of signal. When a planet crosses in front of a star, it blocks some of the radiation streaming toward Earth. By watching for these interruptions in X-ray emissions, the team identified what could be an exoplanet candidate in Messier 51, more commonly known as the Whirlpool Galaxy for its distinctive rotating shape. Based on the duration and characteristics of the transit, researchers estimate the candidate is roughly Saturn-sized and orbits either a black hole or a neutron star at a distance about twice as far as Saturn sits from our Sun.
This discovery matters partly because of how rare it is. Since astronomers first detected an exoplanet candidate in 1988 and confirmed it years later, they have catalogued more than 4,000 confirmed exoplanets. Yet every single one resides within our own galaxy, and the vast majority sit within 3,000 light-years of Earth. The sheer scale of the universe—a 2016 study suggested there could be as many as two trillion galaxies in the observable universe alone—makes finding even one planet beyond our galactic neighborhood feel like an extraordinary achievement. Within the Milky Way itself, scientists estimate there are upwards of 100 billion planets.
But confirmation will not come quickly. Because the candidate planet orbits at such a great distance from its star, it will not pass in front of that star again for approximately 70 years. Even then, astronomers would face the challenge of knowing precisely when to point their instruments at the right moment to catch the brief transit. The team will need additional observations and data to move this candidate from possibility to confirmed discovery. For now, it remains what it is: the first hint that planets exist in galaxies far beyond our own, waiting for technology and time to reveal their secrets.
Citations marquantes
The team estimates the exoplanet candidate could be roughly the size of Saturn and orbit a black hole or neutron star at about twice the distance that Saturn is from our Sun.— Research findings led by Rosanne Di Stefano, Center for Astrophysics
Envie de l'histoire complète ?
Lire l'original sur TechSpot ↗
Science & Space