It's not easy to weigh a star, but an international team of astronomers has done just that.
In fact, they've measured the masses of both stars in an odd binary star system some 25,000 light-years from Earth--and gauged the space-time warp resulting from the system's intense gravitation.
"Our result is important because weighing stars while they freely float through space is exceedingly difficult," Dr. Joeri van Leeuwen, a University of Amsterdam astrophysicist and the leader of the team, said in a written statement. "That is a problem because such mass measurements are required for precisely understanding gravity, the force that is intimately linked to the behavior of space and time on all scales in our universe."
The binary system under study is known to astronomers as J1906. It features a fast-spinning neutron star, or pulsar, in orbit around another star that is believed to be either another neutron star or a white dwarf. Neutron stars are the smallest, densest stars known to exist. Each of the stars in the system is more massive than our sun, and they are 100 times nearer to each other than the Earth is to the sun.
To gauge the pulsar's mass and measure the warping of space within the system, the team tracked the pulsar's rotations using observations from the Arecibo Observatory in Puerto Rico (where the original observations were made) and four other radio telescopes around the world.
The measurements showed that the pulsar's mass is about 1.29 times the mass of the sun, Dr. Ingrid Stairs, a professor of physics and astronomy at The University of British Columbia in Vancouver, told The Huffington Post in an email. Its companion star is about 1.32 times as massive as the sun.
The extreme gravity within the system causes a wobble in the axis of the pulsar's spin (see video above), meaning the portion of the pulsar's emission that we are able to see changes over time.
"We have observed this, and in fact it turns out that we are starting to get close to the edge of the emission region, so that the pulsar is getting fainter and fainter," Stairs told The Huffington Post in an email. "We were lucky to catch it before it disappeared."
But the pulsar isn't gone forever.
"This cosmic spinning top is expected to wobble back into view," van Leeuwen said in the statement, "but it might take as long as 160 years."
A paper describing the research was published Jan. 8, 2015 in The Astrophysical Journal. The research was presented in Seattle on Jan. 8 at a meeting of the American Astronomical Society.