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UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Tue Sep 19, 2017 6:24 pm
by bystander
Secrets of the Bright Star Regulus Revealed
University of New South Wales | 2017 Sep 19
Almost 50 years after it was first predicted that rapidly rotating stars would emit polarised light, a UNSW-led team of scientists has observed the phenomenon for the first time.
They used a highly sensitive piece of equipment designed and built at UNSW Sydney and attached to the Anglo-Australian Telescope at Siding Spring Observatory in western NSW to detect the polarised light from Regulus, one of the brightest stars in the night sky.
The research has provided unprecedented insights into the star, which is in the constellation Leo, allowing the scientists to determine its rate of spinning and the orientation in space of the star’s spin axis. ...
Polarization Due to Rotational Distortion in the Bright Star Regulus - Daniel V. Cotton
et al
Re: UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Wed Sep 20, 2017 8:00 am
by Ann
www.nature.com wrote:
The rotation axis of the star is at a position angle of 79.5 ± 0.7°.
Please! Those of you who understand math, what does this mean? A position angle of 79.5 ± 0.7°?
Do we see Regulus "moderately pole on" or does Regulus mostly present its equator belly to us?
Ann
Re: UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Wed Sep 20, 2017 11:24 am
by MargaritaMc
Ann wrote:www.nature.com wrote:
The rotation axis of the star is at a position angle of 79.5 ± 0.7°.
Please! Those of you who understand math, what does this mean? A position angle of 79.5 ± 0.7°?
Do we see Regulus "moderately pole on" or does Regulus mostly present its equator belly to us?
Ann
"Moderately pole on".
A 90° angle would be with its "north" pole pointing directly at us.
Re: UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Wed Sep 20, 2017 1:05 pm
by Ann
Thank you, Margarita!
I find this property so interesting in hot stars, because they are often hotter at the poles than at the equator - and that is most certainly true for fast-rotating stars. And Regulus is rotating incredibly fast. So, if we see more of one of its poles than of its equator, so to speak, then maybe Regulus appears to be "a little hotter than it really is".
The B-V of Regulus is -0.087. It could be that the average temperature of Regulus is a bit cooler than this B-V index would indicate.
Ann
Re: UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Wed Sep 20, 2017 1:12 pm
by geckzilla
The article doesn't state as much, but usually angles of inclination will be in respect to our position here on Earth, or maybe the barycenter of the Solar system. Another way to say it might be that it is around 10° from having its pole face directly at us.
Re: UNSW: Secrets of the Bright Star Regulus Revealed
Posted: Wed Sep 20, 2017 2:07 pm
by neufer
http://www.etymonline.com/index.php?allowed_in_frame=0&search=oblate wrote:
oblate (adj.) "flattened on the ends," 1705, from Medieval Latin oblatus "flattened," from Latin ob "toward" (see ob-) + latus, abstracted from its opposite, prolatus "lengthened," from latus (adj.) "broad, wide, extensive, large," from Old Latin stlatus (source also of Old Church Slavonic steljo "to spread out," Armenian lain "broad").
oblate (n.) "person devoted to religious work," 1756, from Medieval Latin oblatus, noun use of Latin oblatus, variant past participle of offerre "to offer, to bring before," from ob- (see ob-) + latus "carried, borne" (used as suppletive past participle of ferre "to bear").
oblation (n.) early 15c., from Old French oblacion "offering, pious donation" and directly from Latin oblationem (nominative oblatio) "an offering, presenting, gift," in Late Latin "sacrifice," from Latin oblatus.
