New map reveals just how enormous the supergiant star Antares really is

rod

Oct 22, 2019
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For some who enjoy geeky stats, this report is interesting, 'ALMA and VLA reveal the lukewarm chromospheres of the nearby red supergiants Antares and Betelgeuse', https://www.aanda.org/articles/aa/abs/2020/06/aa37756-20/aa37756-20.html

"Abstract We first present spatially resolved ALMA and VLA continuum observations of the early-M red supergiant Antares to search for the presence of a chromosphere at radio wavelengths. We resolve the free-free emission of the Antares atmosphere at 11 unique wavelengths between 0.7 mm (ALMA band 8) and 10 cm (VLA S band). The projected angular diameter is found to continually increase with increasing wavelength, from a low of 50.7 mas at 0.7 mm up to a diameter of 431 mas at 10 cm, which corresponds to 1.35 and 11.6 times the photospheric angular diameter, respectively..."

My note, Wikipedia reports Antares is 619.7 LY distance from earth or 190 pc. The mass listed is 11 to 14 solar masses. Using 12 solar masses and 700 solar radii, mean density is 4.927300E-08 g cm^-3. At 190 pc, 35 mas = 714.67 solar diameters for Antares, close to the values reported or 6.65 AU diameter. 50.7 mas = 1035.26 solar diameters or 9.633 AU seen in the abstract using ALMA.
 

rod

Oct 22, 2019
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FYI, some may find this interesting. My note, the size calculations obtained for some stars using the heliocentric solar system in the mid and later 1600s, was used as an argument against the heliocentric solar system. From the link and arxiv report, "Robert Hooke in his 1674 'An Attempt to Prove the Motion of the Earth' called attention to the ideas of one of the people he identified as being among the “great anti-Copernicans”: André Tacquet. Hooke was describing— ...a grand objection alleged by divers of the great Anti-copernicans with great vehemency and insulting; amongst which we may reckon Ricciolus and Tacquet, who would fain make the apparent Diameters of the Stars so big, as that the body of the Star should contain the great Orb [Earth’s orbit] many times, which would indeed swell the Stars to a magnitude vastly bigger then the Sun, thereby hoping to make it seem so improbable, as to be rejected by all parties.1", ref - https://ui.adsabs.harvard.edu/abs/2019arXiv190912074G/abstract
 
Jun 1, 2020
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I wonder if the outer atmosphere for Antares extends much farther than our own Heliosphere? The Sun's higher wind speeds -- I assume they are -- makes this a fair question, I think. It's interesting to me that Earth and the other planets are orbiting within the outer solar atmosphere.

FYI, some may find this interesting. My note, the size calculations obtained for some stars using the heliocentric solar system in the mid and later 1600s, was used as an argument against the heliocentric solar system. From the link and arxiv report, "Robert Hooke in his 1674 'An Attempt to Prove the Motion of the Earth' called attention to the ideas of one of the people he identified as being among the “great anti-Copernicans”: André Tacquet. Hooke was describing— ...a grand objection alleged by divers of the great Anti-copernicans with great vehemency and insulting; amongst which we may reckon Ricciolus and Tacquet, who would fain make the apparent Diameters of the Stars so big, as that the body of the Star should contain the great Orb [Earth’s orbit] many times, which would indeed swell the Stars to a magnitude vastly bigger then the Sun, thereby hoping to make it seem so improbable, as to be rejected by all parties.1", ref - https://ui.adsabs.harvard.edu/abs/2019arXiv190912074G/abstract
I think Galileo was also intimidated with this argument but he early-on favored Copernicus and set aside the need for extreme distances for stars to address their lack of parallax, which was about the only argument against Cop's theory.

It's odd to me that they never seemed to take the time to determine if the eye itself was the issue. Given how lousy optics were back then, and the eye is also an optical device. You'd think they would simply light a flame, step-off beyond about 80 meters and recognize that the flame (now a spot) doesn't diminish in size but only intensity. The ~ 1 arcminute resolution of the eye would have been very useful information in those highly scientific debates. Experiments weren't that popular and some of that may have been because it was the college philosophers that were the top of the totem pole. Galileo, when starting as a math prof., was about the least paid.
 
Apr 6, 2020
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I'm not so much impressed by the luminosity "size" of a star is as by its mass.
Antares is only 15 times more massive but 680 times as large as the sun. Most of that is nebulous. An interesting comparison would be density as a function of radius.
 
Jun 1, 2020
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I'm not so much impressed by the luminosity "size" of a star is as by its mass.
Antares is only 15 times more massive but 680 times as large as the sun. Most of that is nebulous. An interesting comparison would be density as a function of radius.
That is pretty amazing. The Sun will in about 4 billion years become perhaps 200 times greater in radius than it is today.
 

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