A study on Mercury’s orbit reveals the Sun is losing mass as it’s getting older. As a result, its gravitational pull is weakening and the orbits of all the planets in our solar system are expanding, like the “waistband of a couch potato in midlife,” according to NASA. Albert Einstein’s theory of general relativity, states that “massive objects, such as the sun, have the effect of warping the space-time continuum around them.” Researchers say this effect can clearly be seen on Mercury as its orbit is closest to the Sun.

“Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun,” explained Antonio Genova, the lead author of the study and a MIT researcher working at NASA’s Goddard Space Flight Center.

Researchers were able to make these calculations from the data gathered by NASA’s MESSENGER spacecraft which made three ‘flybys’ of Mercury in 2008 and 2009 and orbited Mercury between March 2011 and April 2015 before it crashed into Mercury in 2015, Mail noted. The Messenger team was still able to harness the data to determine how the sun’s gravity has changed over time – based on how much mass it has lost and how it has caused planets orbits to widen. Upon studying how the sun has been using up its hydrogen fuel, combined with seven years worth of data, researchers were able to come to conclusion that the sun is slowly, loosening its grasp on Mercury and other planets in the solar system.

“We’re addressing long-standing and very important questions both in fundamental physics and solar science by using a planetary-science approach,” said Erwan Mazarico, a geophysicist at NASA’s Goddard Space Flight Center in a statement. “By coming at these problems from a different perspective, we can gain more confidence in the numbers, and we can learn more about the interplay between the Sun and the planets.”

To earthlings, the effect of broadening of Earth’s orbit will likely remain minuscule as it’s expanding at the rate of less than an inch a year. “This kind of information is not a matter of concern,” Genova told Gizmodo. “But it could be very useful to monitor the sun itself. Perhaps it could give researchers another way to measure the behavior of the sun’s interior.”

The study, entitled “Solar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission” has been published in the journal Nature Communications.