Almost 50 years after fast-rotating stars were predicted to emit polarized light , a team of scientists led by researchers from the University of New South Wales (Australia) has observed the phenomenon for the first time. A new milestone in astronomy .
Taking this discovery into account, scientists confirm that Regulus A’s incredible rotational speed will bring the star to an end sooner than previously thought.
Its rotation speed is 320 kilometers per second , that is, it takes less than 15 hours to make a complete revolution on itself (our Sun takes about 25 days) and it rotates at 96.5% of its terminal speed (in the that the centrifugal force overcomes its own gravity).
What is polarized light?
Normally light waves travel in any direction they want, hitting and bouncing objects around us, but they can also be polarized, which means that they all rotate in a particular direction.
In 1968, astronomers J. Patrick Harrington and George W. Collins II predicted that a rapidly spinning star would emit polarized light because it spins so fast that its shape is distorted into a squashed oblique shape.
Although these ideas from more than 50 years ago prompted the development of a series of instruments designed to detect polarization in interstellar space, until now it has not been possible to capture the polarization of a star of this type.
This has been made possible by a new ultra-sensitive instrument called the High Precision Polarimetric Instrument or HIPPI. “The High Precision Polarimetric Instrument, HIPPI, is the most sensitive astronomical polarimeter in the world”, comments Daniel Cotton, co-author of the work.
The astronomers pointed the telescope at Regulus, a first-magnitude blue star 79 light-years distant from Earth , in a quadruple system alongside Regulus B and C, a red dwarf and an orange dwarf in the constellation Leo. and ranked as the 22nd brightest star in the night sky.
Now, thanks to this first detection of polarized light from a rapidly spinning star, we know that Regulus is spinning at 200 miles per second – so fast that the star is basically about to disintegrate.
This new measurement is useful not only to understand the star itself, but it opens new ways for us to reveal more details about some of the largest and hottest stars in existence, allowing us to discover more information about their life cycles.
“Previously, the field has been largely limited to studying material outside stars or those with extreme magnetic fields. We are now able to probe fundamental parameters of the stellar atmosphere itself,” the authors conclude in the journal Nature Astronomy.
Reference: Polarization due to rotational distortion in the bright star Regulus. Daniel V. Cotton, Jeremy Bailey, Ian D. Howarth, Kimberly Bott, Lucyna Kedziora-Chudczer, PW Lucas &. JH Hough. Nature Astronomy 2017 doi: 10.1038 / s41550-017-0238-6
Image credit: NASA
