Imagine the thrill of giving a pioneering space telescope a second chance at glory—Euclid, currently charting the mysterious realms of dark energy and dark matter, has an unexpected gift: eight extra years of fuel on board. And get this: a brilliant scientist has proposed a plan to transform it into the ultimate astrometric powerhouse, potentially revolutionizing our understanding of the cosmos. But here's where it gets controversial—what if the real innovation lies in simply doing the same job twice?
Space missions often get a second life through 'extended missions,' and it's become almost routine. Think of the Voyager probes, still beaming back data more than four decades after their original five-year assignments wrapped up. Deciding how to repurpose these spacecraft, however, requires careful planning and negotiation. Euclid, scheduled to conclude its primary mission in 2030, is one such example. Its core task has been to create a detailed map of the 'dark universe'—that enigmatic part of our reality made up of dark energy, which is thought to be accelerating the expansion of the universe, and dark matter, an invisible substance that provides the gravitational glue holding galaxies together. Now, a fresh paper by Luigi 'Rolly' Bedin from the Astronomical Institute of Padova (available as a preprint on arXiv) suggests an exciting encore: repurposing Euclid as the most advanced astrometry telescope ever built.
Thanks to its surplus fuel, Euclid could extend its operational lifespan by roughly eight years, effectively doubling the duration of its initial six-year mission, which is already well underway. With this bonus time, Dr. Bedin proposes something that might seem outrageous at first glance—having Euclid repeat its original observations exactly. Why, you might ask, would we want to redo what the telescope just spent years accomplishing? And this is the part most people miss—it all comes down to capturing a second set of data points to reveal movement over time, known as 'proper motion.' For beginners, proper motion is basically how closer objects, like stars in our Milky Way galaxy, appear to shift against a backdrop of more distant ones, such as far-off galaxies, when observed at different times. To calculate this accurately, you need a significant gap between observations—about six years in Euclid's case—to ensure the shifts are noticeable and measurable.
Of course, if you're familiar with current astronomical tools, you might be thinking, 'But what about Gaia?' That's a fair point, and here's where things get really intriguing. Gaia, another ESA mission, is designed to build a 3D map of our galaxy by measuring the proper motion of stars through multiple images taken at different times. The issue is that Gaia has limitations on how faint the objects it can detect. Euclid, on the other hand, excels at spotting extremely dim targets—up to five or six orders of magnitude fainter than what Gaia can manage. By turning Euclid into an astrometric observatory, scientists could uncover billions of additional sources that are too faint for Gaia alone, no matter how long Gaia's mission lasts. Interestingly, Gaia's data is already helping to calibrate Euclid, and there's some overlap in what both telescopes can observe, which could boost the accuracy of Gaia's measurements by a factor of 10 for shared objects. This collaboration could lead to groundbreaking discoveries, like identifying new stars or even exotic phenomena we haven't imagined yet.
But Dr. Bedin doesn't stop there—he envisions pushing Euclid even further. With the remaining fuel, he suggests adding a third round of observations to measure the 'parallax' of a select group of stars. Parallax, in simple terms, is like how your brain uses the slight difference in images from your two eyes to judge depth and distance. For astronomers, it involves capturing images about six months apart, when the telescope is on opposite sides of the Sun, to estimate the true distances of celestial objects. This could provide crucial insights into the scale of the universe, helping us better understand everything from nearby stars to distant cosmic structures.
Now, let's address the elephant in the room: there are engineering hurdles for this parallax idea, since Euclid wasn't originally built for that purpose. Dr. Bedin believes these challenges are surmountable, especially compared to the straightforward task of just repeating the primary observations for proper motion—that's essentially doing what Euclid was made for. With several years left in its current mission, there's ample opportunity to run the necessary simulations and tests. At the very least, ESA's project managers overseeing this flagship telescope should seriously consider Dr. Bedin's ideas; they represent a smart, resourceful way to squeeze more groundbreaking science from an already impressive asset.
What do you think? Is repeating Euclid's mission a brilliant hack or a missed opportunity for fresh exploration? Could this astrometry extension upstage Gaia, or should we invest in entirely new telescopes instead? Share your thoughts in the comments—do you agree with Dr. Bedin, or do you have a counterpoint? Let's discuss!
Learn More:
L. Bedin - The case for an Astrometric Mission Extension of Euclid. Extending Gaia by 6 magnitudes with Euclid covering one-third of the sky (https://arxiv.org/abs/2510.23694)
UT - The ESA's Euclid Space Telescope Gives Glimpses of its Deep Field (https://www.universetoday.com/articles/the-esas-euclid-space-telescope-gives-glimpses-of-its-deep-field)
UT - Euclid Could Find 170,000 Strong Gravitational Lenses (https://www.universetoday.com/articles/euclid-could-find-170000-strong-gravitational-lenses)
UT - Euclid Recovers From a Navigation Problem and Finds its Guide Stars Again (https://www.universetoday.com/articles/euclid-recovers-from-a-navigation-problem-and-finds-its-guide-stars-again)
