The European Euclid mission imaged the center of our galaxy using the microlensing method, thus allowing us to discover new planets and their characteristics. In the meantime, we can navigate through the most incredible of photos…
The European Space Agency’s Euclid mission made it possible to create the largest and most detailed image of the center of our galaxy, the Milky Way, using the so-called “visible” frequencies, i.e. those that our eyes can receive. With more than 60 million stars, this photo paves the way for scientists to confirm the existence of any exoplanets and measure their mass through the tiniest variations in starlight over time. For just one day, like a detective in the Dark Universe, Euclid turned his gaze toward the extremely bright inner region of the galaxy, known as the galactic bulb. Indeed, having been designed to observe billions of distant galaxies, the space telescope’s visible light camera is sensitive enough to distinguish individual stars without being dazzled. This rare ability is crucial to what scientists plan to use this image for: studying planets around other stars using a special technique called “microlensing.” By comparison, Euclid’s clarity and sensitivity in visible light are similar to that of the Hubble Space Telescope’s wide-field camera, however, each pointing that Euclid captures in just a few hours covers an area 270 times larger than the field of view of the famous space telescope, capturing more than 60 million stars along with nebulae and star clusters. Microlensing is a type of gravitational lensing and occurs when a foreground galaxy and its halo of dark matter act as a lens, distorting the image of a background galaxy. Thus Euclid will identify around 7,000 potential gravitational lenses to be included in the large publication of cosmological data scheduled for the end of 2026. This is a useful method for exploring massive and distant objects, such as galaxy clusters. The phenomenon is based on the random alignment of two stars with respect to an observer. When one star passes in front of another, the closer one acts like a cosmic magnifying glass, bending and intensifying the light of the background star. If a planet orbits the nearest star, its gravity also bends this light slightly. It is precisely this tiny additional variation in brightness that reveals the presence of a planet. Jean-Philippe Beaulieu of the Institute of Astrophysics in Paris, France, explains: “To detect microlensing, it is necessary to observe portions of the sky crowded with stars, such as those near the center of our galaxy; in the last twenty years, almost 300 exoplanets have been discovered using this technique, all with ground-based telescopes and all in the direction of the center of our galaxy. This Euclid image includes 51 known planetary systems – and will contribute to the study of many more that will be detected.” His colleague and researcher Natalia Rektsini, who led the publication of the Euclid galactic bulb survey data for the scientific community, said: “Within 24 hours, Euclid has already captured the stars involved in all future microlensing events that the Roman space telescope will detect, but before the stars and planets involved have aligned. This means that anyone who detects an event with this method, in the same region, will now be able to use the data of Euclid as a time reference in the past and see what the stars looked like before they overlapped. “Because Euclid is able to clearly separate individual stars, it is then possible to measure their speed of movement over time and use that information to confirm the existence of a planet and determine its mass. This would not be possible with data from a single moment in time.” Dr. Beaulieu recalls: “I led the team that discovered Ogle-2005-BLG-390Lb, an icy planet that looks a bit like Hoth from Star Wars, about twenty years ago. After all this time, I’m thrilled that Euclid can finally allow us to measure its mass precisely.” In just 24 hours, Euclid provided unique data on the center of the Milky Way, with a wide and clear view of this region. As time passes, the separation between sources and lenses increases. That’s why this Euclid data will provide a temporal benchmark for past and future missions and enable the study of exoplanets and their masses.” Euclid was launched in July 2023 and began its routine science observations on February 14, 2024. The mission’s goal is to reveal the hidden influence of dark matter and dark energy on the visible Universe. Over a six-year period, Euclid will observe the shapes, distances and motions of billions of galaxies up to 10 billion light years away. You can browse the photo of the Milky Way at this link: ESASky 7.9.0
