Seeing the nearest stars

[LeonardRenner]

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?

[neufer]

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

[geckzilla]

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.

[neufer]

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.

A drawing of a sunspot in the Chronicles of John of Worcester

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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

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.>>

[Chris Peterson]

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.

[Jerome68]

I think the idea of combining the data from the different telescopes is pretty clever, actually, something similar was used to catch the first image from a black hole[1] making it official in Apr 2019. So, in theory, it is possible and has been done, the point is giving the huge distance between Earth and the closest star, and how small it is in comparison, it will require a huge effort with all of our current instruments, a lot of software to process and combine the images (and not sure if even though we could catch the Start marks like SOHO shows from our sun).

[1] https://www.jpl.nasa.gov/edu/news/2019/ ... lack-hole/

[Chris Peterson]

I think the idea of combining the data from the different telescopes is pretty clever, actually, something similar was used to catch the first image from a black hole[1] making it official in Apr 2019. So, in theory, it is possible and has been done, the point is giving the huge distance between Earth and the closest star, and how small it is in comparison, it will require a huge effort with all of our current instruments, a lot of software to process and combine the images (and not sure if even though we could catch the Start marks like SOHO shows from our sun).

[1] https://www.jpl.nasa.gov/edu/news/2019/ ... lack-hole/

This is not currently possible with optical telescopes, except for ones that are close enough together (a few hundred meters or less) that their light can be directly combined. That's because our current technology does not allow capturing all of the phase information with light, so there's no way to combine the data from separate, isolated telescopes. We can do this with radio because of the much longer wavelength. VLBI is currently limited to submillimeter and longer wavelengths- about 1000 times longer than light.

[Jerome68]

yes, that is true, I just realized after reading you that my answer could lead to confusions, thanks for the clarification

[Fred the Cat]

Besides molecular biosignatures, detecting generated light seems an obvious method of finding advanced civilizations. Since we have a giant telescope that detects IR, could it help find heat generation of an alien nature?

Probably not campfires of alien neanderthals but ET’s may need to stay warm too.

[Fred the Cat]

Besides CO₂, O₂ is projected to look for those ETs.

Beings like us need our O₂.