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Hubble Space Telescope spots rogue planet with a little help from Einstein: 'It was a lucky break'
Hubble Space Telescope spots rogue planet with a little help from Einstein: 'It was a lucky break'

Yahoo

time01-08-2025

  • Science
  • Yahoo

Hubble Space Telescope spots rogue planet with a little help from Einstein: 'It was a lucky break'

When you buy through links on our articles, Future and its syndication partners may earn a commission. Astronomers discovered a new rogue planet lurking in archival data gathered by the Hubble Space Telescope, and the find is thanks to a little serendipity — and a little help from the genius himself, Albert Einstein. Rogue, or "free-floating," planets are worlds that don't orbit a star. They earn their rogue status when they are ejected from their home systems due to interactions with their sibling planets or via gravitational upheaval caused by passing stars. The most successful way of detecting an extrasolar planet, or exoplanet, in general is waiting until it crosses, or "transits," the face of its parent star. Being cosmic orphans without a stellar parent, however, rogue planets can't be detected in this way. Fortunately, a phenomenon first predicted by Einstein in 1915 offers a way to spot these rogue worlds. "Free-floating planets, unlike most known exoplanets, don't orbit any star. They drift alone through the galaxy, in complete darkness, with no sun to illuminate them. That makes them impossible to detect using traditional planet-detection techniques, which rely on light from a host star," Przemek Mroz, study team member and a professor at the University of Warsaw, told "To find these elusive objects, we use a technique called gravitational microlensing." How Einstein became a rogue planet hunter Einstein's 1915 theory of gravity, general relativity, suggests that objects with mass cause the very fabric of space to "warp." The bigger the mass, the greater the warp and thus the stronger the gravity that arises from the warp. Gravitational lensing arises when light from a background source passes by the warp. Its path gets curved. This can amplify that background source, an effect that astronomers use with Hubble and the James Webb Space Telescope (JWST) to study extremely distant galaxies that would usually be too faint to see. "This phenomenon occurs when a massive object, the lens, passes in front of a distant star (the source), magnifying the star's light due to the lens's gravity," Mroz explained. "The beauty of microlensing is that it works even if the lensing object emits no light at all. "During microlensing events, the source star gets temporarily magnified. We can estimate the mass of the lensing object by measuring the duration and other properties of the event." Mroz added that when microlensing events are generated by passing rogue planets, they are usually very short, lasting less than a day. The particular microlensing event the team studied to reveal this new rogue world is designated OGLE-2023-BLG-0524 and was observed by Hubble on May 22, 2023, remaining buried in data from the space telescope. "It was discovered in the direction of the Galactic bulge by the Optical Gravitational Lensing Experiment [OGLE] survey, and independently observed by the Korea Microlensing Telescope Network [KMTNet]," Mroz said. "The Einstein timescale of the event was just eight hours, making it one of the shortest microlensing events on record." Based on the microlensing event's properties, Mroz and colleagues were able to estimate that the lensing body object could be either a Neptune-mass planet located in the Milky Way's galactic disk, around 15,000 light-years away. Alternatively, the rogue world could be a larger but more distant Saturn-mass object in the Milky Way's galactic bulge, roughly 23,000 light-years away. "Both scenarios are consistent with the microlensing signal we observed," Mroz said. Hunting for planets in Hubble's archives One of the most important tasks that faced the team upon the discovery of the microlensing event OGLE-2023-BLG-0524 was determining that this was indeed caused by a rogue planet, and not by a planet associated with a star but on a wide orbit far from its stellar parent. They reasoned that if the planet had a nearby host star, within 10 times the distance between Earth and the sun (10 AU), they would have likely seen a second, longer-lasting microlensing signal from the star. The researchers saw no such signature, so they could rule out that the planet had a close stellar companion. However, if the planet orbits a star at a much wider separation, greater than 10 AU, the odds of detecting the host star are much lower. "This means we can't fully rule out the wide-orbit scenario, but here's where it gets interesting," Mroz said. "Because the lens and the background star are slowly moving relative to each other, they will eventually separate in the sky. "If we detect light from the lensing object at that point, we'll know it's not completely free-floating." Unfortunately, Mroz explained that the distance between the planet and the background star means their relative motion appears incredibly small, about 5 milliarcseconds per year. "It will take at least a decade before we can hope to resolve them with current instruments, such as the Hubble Space Telescope or large ground-based telescopes," Mroz said. Hubble was particularly useful in this rogue planet hunt because the region of the sky that hosts the microlensing event was observed by the long-serving space telescope way back in 1997. That's over 25 years before the microlensing event. "That gave us a unique opportunity to test whether there might be a star associated with the lens," Mroz said. "According to our model, by 1997, the lens and source should have been separated by 0.13 arcseconds. That's tiny, but within Hubble's capabilities. If the lens were a bright star, we would have seen it in those old images. But we didn't." The absence of detectable light at the expected lens position told the team that any potential host star would have to be very faint. "Depending on the stellar population model we use, that rules out around 25% to 48% of possible companion stars," Mroz said. "That pushes us further toward the conclusion that this may truly be a free-floating planet." Related Stories: — The mystery of how strange cosmic objects called 'JuMBOs' went rogue — These mysterious objects born in violent clashes between young star systems aren't stars or planets — James Webb Space Telescope dives into the atmosphere of a mystery rogue planet or failed star Mroz explained that OGLE-2023-BLG-0524 was discovered by team member Mateusz Kapusta by chance while the team was following up on microlensing events. "This discovery was partly serendipity!" Mroz said. "It was a lucky break, but we believe there are many more such opportunities hidden in the data. "Microlensing events occur all the time in dense stellar fields, and many of those fields have been observed by Hubble in the past. That means there could be more interesting events waiting to be discovered in the Hubble data." The team's research is available as a preprint on the paper repository arXiv. Solve the daily Crossword

Rare exoplanet discovered in outskirts of the Milky Way
Rare exoplanet discovered in outskirts of the Milky Way

Yahoo

time18-06-2025

  • Science
  • Yahoo

Rare exoplanet discovered in outskirts of the Milky Way

Astronomers have located a rare exoplanet on the edge of the Milky Way. The exoplanet, a gas giant named AT2021uey b, orbits a low-mass star and is located about 3,200 light-years away from Earth, according to a paper published last month in the journal Astronomy & Astrophysics. Its orbit around an M dwarf star -- a relatively small and cool star -- completes every 4,170 days. MORE: Exoplanet discovered in 2020 has the coldest temperatures ever measured, scientists say The researchers used a technique known as gravitational microlensing -- a method based on Albert Einstein's theory of general relativity -- to locate the planet. The presence of mass warps the fabric of space-time, similar to how a bowling ball would make a dent when placed on a trampoline, according to NASA. The effect is extreme around "very massive" objects, such as black holes and galaxies, but stars and planets can also cause a detectable degree of warping. The new exoplanet's mass is estimated to be slightly greater than Jupiter's, the researchers said. The unusual size ratio to the star it orbits led to its discovery, as detecting an Earth-type planet would have been "much more difficult," according to a press release by Vilnius University in Lithuania. Gravitational microlensing is a "rare phenomenon," the researchers said. There have only been three such cases of a planet being documented by microlensing in the history of observations, the researchers said. Astronomers search for a temporary light "pulsation" when analyzing a vast amount of data. The vast majority of observed stars -- about 90% -- pulsate for "various other reasons," with a minority of cases actually showing the microlensing effect, Marius Maskoliūna, an astronomy and astrophysics researcher at Vilnius University and co-author of the study, said in a statement. "This kind of work requires a lot of expertise, patience, and, frankly, a bit of luck," Maskoliūna said. "You have to wait for a long time for the source star and the lensing object to align and then check an enormous amount of data." MORE: Could our solar system have 9 planets after all? Astronomers may have confirmed possible existence. In addition, most microlensing efforts are recorded at the Galactic Center -- the densest part of the Milky Way, Edita Stonkutė, an associate professor of astronomy at Vilnius University, said in a statement. AT2021uey b was found quote far from the center, in the "galactic halo, on the outskirts of the galaxy, she said. "This is only the third planet in observational history to be discovered so far from the Galactic bulge," Stonkutė said. The microlensing technique is promising because it allows the detection of the "unexpected or even invisible," the researchers said. "What fascinates me about this method is that it can detect those invisible bodies," Maskoliūna said. In collaboration with researchers from the Astronomical Observatory of the University of Warsaw, the researchers analyzed data from the European Space Agency's "Gaia" telescope and supplemented it with ground-based observations from telescopes at the Vilnius University's Molėtai Astronomical Observatory. MORE: How astronomers used gravitational lensing to discover 44 new stars in distant galaxy The microlensing phenomenon was first spotted in 2021, which led the astronomers on a yearslong journey to "carefully" verify the existence of the new exoplanet, according to the release. The first discovery of an exoplanet orbiting a star was made in 1995, the researchers said. Since then, more than 6,000 exoplanets have been confirmed. However, the science is still considered "relatively young," the researchers said. "As data accumulated, we learned that many types of planetary systems are completely unlike ours -- the Solar System," Stonkutė said. "We've had to rethink planetary formation models more than once."

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