NASA researchers have, for the first time in history, weighing the mass of a lone white dwarf using a strange phenomenon that was predicted by Albert Einstein's Theory of General Relativity.
The study's results confirm astronomers' predictions of exactly how massive white dwarfs can be and could help provide information about the strange, ultra-dense matter that makes up these shriveled husks of dead stars.
Weighing a Lone White Dwarf
In the latest study, the team utilized the Hubble Space Telescope to measure a white dwarf's mass. The long star is called LAWD 37, and the study findings were published in the March issue of the journal Monthly Notices of the Royal Astronomical Society.
While astronomers have previously weighed white dwarfs in binary star systems, where two stars are orbiting a common center of mass, LAWD 37 is the first white dwarf to be weighed in isolation.
An astronomer from the University of California Santa Cruz, Peter McGill, led the research team that used a quirky property of the universe to make the historical finding. This is the fact that gravity warps space-time, as per Live Science.
As the lone white dwarf passed in front of a distant bright star, the light from the star in the background was bent around LAWD 37 in a process that astronomers call gravitational microlensing, which Einstein initially predicted.
When the nearby white dwarf warped the farther star's light, the cosmic object appeared to shift ever so slightly in the sky, which is an effect that Hubble can detect with incredible precision using its highly advanced instruments.
In a statement, McGill said that such events are rare and noted that the effects are minuscule. For example, the size of the team's measured offset was like measuring the length of a car on the moon while looking at it from the surface of our planet.
Utilizing Einstein's Theory of Predictions
The team then did the calculations and discovered that LAWD 37 has roughly 56% of the mass of our Sun. The study's results also agree with previous white dwarf mass predictions and provide information into the evolutionary processes of dead stars, according to ADAFruit.
Before the recent study, mass measurements of white dwarfs in the past were made by observing stars in binary systems. Astronomers used straightforward Newtonian physics to measure the masses of these cosmic bodies.
However, such calculations can be uncertain and inaccurate if the companion of the white dwarf is in a long-period orbit of hundreds or thousands of years. Scientists can only measure orbital motion using telescopes for a short period of the dwarf's orbital motion.
Kailash Sahu from the Space Telescope Science Institute in Baltimore, Maryland, was the principal Hubble investigator on the recent study. They first used microlensing in 2017 when they measured the mass of another white dwarf known as Stein 2015 B.
However, that particular cosmic object was located inside a widely separated binary system. Sahu noted that their latest observation provides a new benchmark because LAWD 37 was a lone white dwarf, said NASA.
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