Einstein Was Right, Sun Is Losing Mass

Sunday, January 21, 2018 - 10:07

A team of researchers from the Massachusetts Institute of Technology, the University of Maryland and the NASA Goddard Space Flight Center have demonstrated that the aging sun is behaving according to Albert Einstein's theory of general relativity.

As our sun gets older, it's losing mass, and so its gravitational pull becomes weaker. As a result, the orbits of all the planets in our solar system are expanding, not unlike "the waistband of a couch potato in midlife," according to a new NASA press statement.

"Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun," said Antonio Genova, the lead author of the study published in Nature Communications and a Massachusetts Institute of Technology researcher working at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Mercury, being so affected by the sun’s gravity, offers a way for scientists to spot tiny differences between theoretical predictions of the sun’s gravity and what we actually observe, by measuring the orbit of Mercury for a long time. Thankfully, we had the MESSENGER probe orbiting Mercury to make these calculations (it crashed into Mercury in 2015).

The MESSENGER data showed that Einstein still isn’t wrong, of course. With better equipment, scientists can one day perform these tests with even more precision, and maybe find a place where measurements slightly differ from his theories. That hasn’t happened yet, though.

The MESSENGER team was also able to determine how the sun’s gravity changes over time—based on how it loses mass, and how that lost mass causes planets’ orbits to widen. Seven years of data, combined with observations of how the sun uses up its hydrogen fuel, reveal that the sun is slowly, every so slightly, loosening its grasp on Mercury. This was one of the “first experimental observations of the solar mass loss,” according to the paper published recently in Nature Communications.

As a reminder, all of this data comes with a spread—scientists can always achieve better certainty of the data with more measurements and better equipment.

More importantly, this should remind you that Mercury is an awesome, useful planet that you should not forget. After all, monitoring it continues to support the accuracy of one of physics most important theories: the one that describes gravity.

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