New observations show the sun is slowly losing its mass over time

A group of astronomers have discovered definitive evidence that the sun is slowly losing mass over time.
By Joseph Scalise | Jan 24, 2018
The sun is slowly losing mass over time, which is weakening its gravitational pull and slowly allowing the planets in our solar system to expand their orbits, a new study published in the journal Nature Communications reports.

This discovery comes from researchers at NASA and the Massachusetts Institute of Technology, who studied Mercury's orbit in order to determine different shifts in our host star.

To begin the study, the researchers first refined Mercury's ephemeris -- its course around the Sun, charted over time -- and studied its position in space. Years of records showed that Mercury tends to shift its closest position to the sun over time in a process known as precession. Some of that shift is the result of other planets in the solar system pulling at Mercury. However, that does not account for all of the changes.

Another part comes from tiny alterations in the Sun's processes and internal structure. One such characteristic is the Sun's oblateness -- the amount it bulges at the equator due to its spin.

The team focused on that oblateness in their research by drawing on radio data that tracked the position of NASA's Messenger spacecraft. The vessel made three flybys over Mercury in 2008 and 2008, and then orbited the planet between March 2011 and April 2015. Studying information collected from those periods allowed astronomers to figure out how the Sun's physical shape has influenced Mercury.

"Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun," said lead author Antonio Genova, a researcher at the Massachusetts Institute of Technology, according to ZME Science

That information allowed the team to develop a new analytical method that simultaneously estimated and integrated the orbits of Mercury and the Messenger craft. The end result is a solution which takes into account both relativistic effects and processes inside the sun.

This study is the first time researchers estimated the sun's oblateness through observation rather than secondary data. In past research, scientists predicted the sun loses one-tenth of a percentage of its mass over 10 billion years. The team in the new study found that the sun loses a bit less mass, and they did so with much more accurate measurements.

"We're addressing long-standing and very important questions both in fundamental physics and solar science by using a planetary-science approach," said study co-author Erwan Mazarico, a researcher at NASA. "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."

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