Imagine having a spaceship with a full tank of gas and nowhere to go! That's almost the situation with the Euclid space telescope. Originally slated to end its mission in 2030, Euclid, designed to map the "dark universe" of dark energy and dark matter, has enough fuel for another eight years of operation. But what should it do with all that extra time? One scientist has proposed a brilliant, and surprisingly simple, plan.
Space telescopes often outlive their initial missions. Think about the Voyager probes, still beaming back data more than 40 years after their primary five-year mission wrapped up. However, figuring out the best way to utilize these extended lifespans involves careful planning and negotiation. Now, a new paper from Luigi "Rolly" Bedin of the Astronomical Institute of Padova suggests a fascinating second act for Euclid: transforming it into the most powerful astrometric telescope ever created.
Euclid's extended lifespan, thanks to its surplus fuel, could more than double its original six-year mission, which is already underway. Dr. Bedin's proposal? To repeat Euclid's initial mission. Yes, you read that right. He suggests using the telescope to do essentially the same thing it was already designed to do.
Why would we want to do that? Because repeating the initial observations would allow scientists to measure something called "proper motion." This is where it gets interesting... Proper motion refers to how nearby objects, such as stars within our Milky Way galaxy, appear to move relative to more distant objects, like faraway galaxies, over time. To accurately calculate proper motion, astronomers need a significant time gap between observations. Dr. Bedin believes that six years is the sweet spot for Euclid to achieve precise measurements.
Now, you might be thinking, "Wait a minute! Doesn't the Gaia space telescope already do this?" And you'd be right. Gaia is specifically designed to create a 3D map of the Milky Way by precisely measuring the positions and motions of billions of stars.
But here's the part most people miss... Gaia has a limit to how faint the objects it can detect. Euclid, on the other hand, is designed to observe extremely faint objects. It can see things five to six magnitudes fainter than Gaia. That's a huge difference! By repurposing Euclid for astrometry, scientists could uncover billions of faint and distant sources that Gaia simply can't see, regardless of how long Gaia's mission lasts. In fact, data from Gaia is already used to calibrate Euclid, and overlapping observations could improve the accuracy of Gaia's measurements by a factor of ten!
And this is where it gets controversial... Dr. Bedin proposes an even more ambitious idea: a third "epoch" of observations focused on measuring the "parallax" of a select group of stars. Parallax is the apparent shift in an object's position when viewed from different locations. In astronomy, this means taking pictures six months apart, when the telescope is on opposite sides of the Sun. This mimics the effect of depth perception with our two eyes, allowing us to estimate the distance to these stars.
Fraser Cain has often praised Gaia's abilities, but Dr. Beldin points out that Euclid could provide complementary data.
Dr. Bedin acknowledges that this third use case presents significant engineering challenges, as Euclid wasn't originally designed for parallax measurements. But he believes these challenges are surmountable, especially compared to the relative simplicity of repeating the initial survey for proper motion measurements. Given the time remaining in Euclid's extended mission, there's ample opportunity to conduct the necessary engineering studies to determine the feasibility of this ambitious plan.
At the very least, the project managers of this flagship ESA mission should seriously consider Dr. Bedin's suggestions. They offer a simple and elegant way to unlock exciting new scientific discoveries using existing resources. What do you think? Should Euclid focus on proper motion measurements, attempt the more challenging parallax observations, or perhaps pursue a combination of both? Let us know your thoughts in the comments below!
