Seeing the nearest stars

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LeonardRenner
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Seeing the nearest stars

Post by LeonardRenner » Fri Jun 12, 2020 7:47 am

Assuming it was scientifically possible to combine the capabilities of some of our most advanced instruments, say SOHO and Hubble, how large would the lens or mirror of a telescope need to be so that we could see Proxima Centauri, or preferably the nearest Sun-like star Alpha Centauri A, at the same level of detail, and at the same wavelengths, as SOHO shows us? I think it would be a neat "first" to see another star at such resolution, but could it ever be done?

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neufer
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Re: Seeing the nearest stars

Post by neufer » Fri Jun 12, 2020 11:46 am

LeonardRenner wrote:
Fri Jun 12, 2020 7:47 am

Assuming it was scientifically possible to combine the capabilities of some of our most advanced instruments, say SOHO and Hubble, how large would the lens or mirror of a telescope need to be so that we could see Proxima Centauri, or preferably the nearest Sun-like star Alpha Centauri A, at the same level of detail, and at the same wavelengths, as SOHO shows us? I think it would be a neat "first" to see another star at such resolution, but could it ever be done?
We can almost resolve Betelgeuse now:
https://apod.nasa.gov/apod/ap200217.html

While Proxima Centauri is 165 times closer than Betelgeuse
it is also 5,750 times smaller :!:
Art Neuendorffer

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geckzilla
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Re: Seeing the nearest stars

Post by geckzilla » Sun Jun 14, 2020 12:08 am

Back in the day Nitpicker helped me answer the question about how big a Hubble style mirror would have to be to resolve Proxima Centauri to just a few pixels: https://flic.kr/p/pFBTsR

We're talking kilometer range in size to resolve stars to at least a few pixels.
Just call me "geck" because "zilla" is like a last name.

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neufer
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Re: Seeing the nearest stars

Post by neufer » Sun Jun 14, 2020 12:16 pm

geckzilla wrote:
Sun Jun 14, 2020 12:08 am

We're talking kilometer range in size to resolve stars to at least a few pixels.
When we build those kilometer range telescopes the first thing we will observe will be star spots.
https://en.wikipedia.org/wiki/Solar_observation wrote: The earliest known record of a sunspot drawing was in 1128: In the third year of Lothar, emperor of the Romans, in the twenty-eighth year of King Henry of the English...on Saturday, 8 December, there appeared from the morning right up to the evening two black spheres against the sun. — John of Worcester
https://iopscience.iop.org/article/10.3847/1538-4357/ab7384 wrote:
Temporal Evolution of Spatially Resolved Individual Star Spots on a Planet-hosting Solar-type Star: Kepler-17

The Astrophysical Journal, Volume 891, Number 2
Kosuke Namekata1 et al., Published 2020 March 11

Abstract: <<Star spot evolution is visible evidence of the emergence/decay of the magnetic field on a stellar surface, and it is therefore important for the understanding of the underlying stellar dynamo and consequential stellar flares. In this paper, we report the temporal evolution of individual star spot areas on the hot-Jupiter-hosting, active solar-type star Kepler-17, whose transits occur every 1.5 days. The spot longitude and area evolution are estimated (1) from the stellar rotational modulations of Kepler data and (2) from the brightness enhancements during the exoplanet transits caused by existence of large star spots. As a result of the comparison, the number of spots, spot locations, and the temporal evolution derived from the rotational modulations are largely different from those of in-transit spots. We confirm that, although only two light-curve minima appear per rotation, there are clearly many spots present on the star. We find that the observed differential intensity changes are sometimes consistent with the spot pattern detected by transits, but at other times they do not match with each other. Although the temporal evolution derived from the rotational modulation differs from those of in-transit spots to a certain degree, the emergence/decay rates of in-transit spots are within an order of magnitude of those derived for sunspots as well as our previous research based only on rotational modulations. This supports the hypothesis that the emergence/decay of sunspots and extremely large star spots on solar-type stars occur through the same underlying processes.>>
Art Neuendorffer

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Chris Peterson
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Re: Seeing the nearest stars

Post by Chris Peterson » Tue Jun 16, 2020 6:16 pm

LeonardRenner wrote:
Fri Jun 12, 2020 7:47 am
Assuming it was scientifically possible to combine the capabilities of some of our most advanced instruments, say SOHO and Hubble, how large would the lens or mirror of a telescope need to be so that we could see Proxima Centauri, or preferably the nearest Sun-like star Alpha Centauri A, at the same level of detail, and at the same wavelengths, as SOHO shows us? I think it would be a neat "first" to see another star at such resolution, but could it ever be done?
Resolution scales linearly with aperture. The SOHO camera has an aperture of 0.1 m. Alpha Centauri is about 250,000 times farther from us than the Sun. So that means to achieve similar imaging resolution would require an objective 25 km in diameter.
Chris

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