Shining brightly in the constellation
Leo is a fast-spinning star that shoots through the cosmos like an
extra-wide bullet, perplexing astronomers as it moves through space in the
same direction as its polar axis.
Researchers have long known
that Regulus, the brightest star in Leo, spins much faster than the Sun,
but new observations with an array of telescopes pinned down the star's odd
motion and a host of other characteristics.
"We don't have any idea why
it's really doing that," said Georgia State University astronomer Hal
McAlister, who led the study of the star at the university's Center
for High Angular Resolution (CHARA). "The picture makes me
wonder what it would be like to be in a solar system with this type of
star."
Regulus' axis is tilted about 86 degrees, presenting
astronomers on Earth with an askew view of the star.
Using the CHARA array of telescopes atop
California's Mount Willson, McAlister and his team were able to make the first
observations of how Regulus is shaped by its high-speed rotation: 700,000
miles (1.1 million kilometers) an hour spin at its
equator.
With such a high
rate of rotation -- the Sun, for comparison, has an equatorial spin of about
4,500 miles (7,242 kilometers) an hour -- Regulus bulges out at the center to a
diameter about 4.2 times that of Earth's home star. If Regulus spun just 10
percent faster it would rip itself apart, but that's not likely, researchers
said.
"There's nothing that we
know of that can speed this star up," McAlister told
SPACE.com.
Although Regulus shines
about 350 times brighter than the Sun, it burns hotter at its poles (15,100
degrees Celsius) than at the equator (10,000 degrees Celsius), where
the pull of gravity is diminished by the star's distorted shape which in turn
lowers the temperature, researchers said, adding that the poles shine five times
brighter than the equator.
Researchers used
measurements of the CHARA array's six telescopes to determine Regulus'
temperature, speed spin axis orientation along with a light-combining method
called interferometry.
McAlister said that the
Regulus study is just the start of observations with the CHARA array.
"Literally we have
thousands of other targets to choose from for future study," he said, adding
after studying the young, hot Regulus, he'd like to measure the diameters of
cooler, older stars. "We're only beginning to dip our toes in this
ocean."
This
article is part of SPACE.com's weekly Mystery Monday
series.