APOD: Andromeda in a Single Shot (2021 Jun 25)

[APOD Robot]

Andromeda in a Single Shot

Explanation: How far can you see? The Andromeda Galaxy, 2.5 million light years away, is the most distant object easily seen by the unaided eye. Other denizens of the night sky, like stars, clusters, and nebulae, are typically hundreds to thousands of light-years distant. That's far beyond the Solar System but well within our own Milky Way Galaxy. Also known as M31, the external galaxy poses directly above a chimney in this well-planned deep night skyscape from an old mine in southern Portugal. The image was captured in a single exposure tracking the sky, so the foreground is slightly blurred by the camera's motion while Andromeda itself looms large. The galaxy's brighter central region, normally all that's visible to the naked-eye, can be seen extending to spiral arms with fainter outer reaches spanning over 4 full moons across the sky. Of course in only 5 billion years or so, the stars of Andromeda could span the entire night sky as the Andromeda Galaxy merges with the Milky Way.

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[Joe Stieber]

Of course, M31's satellite galaxies, M32 and M110, are also present in the picture. M110 floats above M31 while M32 is like a puffy star below-right of M31's core. There's another galaxy too, NGC 404, the "Ghost of Mirach," which is a faint smudge just above the bright star Mirach (Beta Andromedae) to the right of the chimney near the bottom.

[Ann]

Of course, M31's satellite galaxies, M32 and M110, are also present in the picture. M110 floats above M31 while M32 is like a puffy star below-right of M31's core. There's another galaxy too, NGC 404, the "Ghost of Mirach," which is a faint smudge just above the bright star Mirach (Beta Andromedae) to the right of the chimney near the bottom.

Thanks, Joe, what a perfect description!

Bright star Mirach with the Ghost of Mirach at upper left. Star HD 6892 is to the right of Mirach's Ghost in this picture. Photo: Kent Wood.

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1) Mirach, 2) HD 6892, 3) Ghost of Mirach

In today's APOD, the Ghost of Mirach is just above Mirach, as Joe said, whereas star HD 6892 is to the left of Mirach. In other words:

1) Mirach

2) HD 6892

3) NGC 404, Ghost of Mirach

Isn't it just too funny that this galaxy is also called NGC 404, as in failure 404?

Anyway, it's a great APOD! I love it! Andromeda itself looks like a single puff of smoke that has been released by the tall chimney.

Ann

[JohnD]

Set the ccontrols for the heart of the Sun/Galaxy! Fire when she bears, Mr.Mate!

[Eclectic Man]

I wonder how different Western history would have been had Andromeda been easily visible in the sky when the Roman Catholic Church decided that the whole of creation orbited the Earth. It would have been obvious that Andromeda was a system all of itself.

[orin stepanek]

In 2 to 3 billion years; this Earth will go through so many changes that there may or may not be creatures as we know them inhabiting this planet!

[JohnD]

What do you mean, EM? That Andromeda should have been bigger in the sky? That would have screwed up the Milky Way, which it will do, one day in the future, as we rush towards it! It's the only galaxy that's naked eye visible, and was known when the Ptolomeic model of the Universe reigned, but as a 'nebula', a cloud. It was long after we realised that even the Sun wasn't the centre of the Universe at the beginning of the 20th, that the true nature of Andromeda was seen, so the earlier dogmatism may be forgiven!

[NCTom]

What was the duration of this single exposure and where would I need to look for that information?

[bystander]

What was the duration of this single exposure and where would I need to look for that information?

https://www.miguelclaro.com/wp/portfoli ... -exposure/

25 seconds

[neufer]

--------------------------------------------------------------------

• Henry IV, Part I [Act II, scene 1]

First Carrier:

• Heigh-ho! an it be not four by the day, I'll be
  hanged: Charles' wain is over the new chimney,
  and yet our horse not packed. What, ostler!

----------------------------------------------------------------------

[neufer]

What do you mean, EM? That Andromeda should have been bigger in the sky? That would have screwed up the Milky Way, which it will do, one day in the future, as we rush towards it! It's the only galaxy that's naked eye visible, and was known when the Ptolomeic model of the Universe reigned, but as a 'nebula', a cloud.

<<The Magellanic Clouds (or Nubeculae Magellani) are two irregular dwarf galaxies visible in the Southern Celestial Hemisphere. The Magellanic Clouds have been known since ancient times by indigenous people from South America and Africa, and from the first millennium in Western Asia. The first preserved mention of the Large Magellanic Cloud is believed to be in petroglyphs and rock drawings found in Chile. They may be the objects mentioned by the polymath Ibn Qutaybah (d. 889 CE), in his book on Al-Anwā̵’ (stations of the Moon in pre-Islamic Arabian culture).Later Al Sufi, a professional astronomer, in 964 CE, in his Book of Fixed Stars, mentioned the same quote, but with a different spelling. Under Argo Navis, he quoted that "unnamed others have claimed that beneath Canopus there are two stars known as the 'feet of Canopus', and beneath those there are bright white stars that are unseen in Iraq nor Najd, and that the inhabitants of Tihama call them al-Baqar [cows], and Ptolemy did not mention any of this so we [Al-Sufi] do not know if this is true or false." Both Ibn Qutaybah and Al-Sufi were probably quoting from the former's contemporary (and compatriot) and famed scientist Abu Hanifa Dinawari's mostly lost work on Anwaa. Abu Hanifa was probably quoting earlier sources, which may be just travelers stories, and hence Al-Sufi's comments about their veracity.>>

[Chris Peterson]

I wonder how different Western history would have been had Andromeda been easily visible in the sky when the Roman Catholic Church decided that the whole of creation orbited the Earth. It would have been obvious that Andromeda was a system all of itself.

If we were closer to Andromeda, it would be bigger. But no brighter. The spiral structure would still be largely invisible to the eyes. It would look like a blob sticking off of the northern Milky Way, and about the same brightness as the Milky Way. There would be nothing to give away its actual size or its actual distance. Just another fuzzy gray thing in the sky.

[neufer]

I wonder how different Western history would have been had Andromeda been easily visible in the sky when the Roman Catholic Church decided that the whole of creation orbited the Earth. It would have been obvious that Andromeda was a system all of itself.

If we were closer to Andromeda, it would be bigger. But no brighter. The spiral structure would still be largely invisible to the eyes. It would look like a blob sticking off of the northern Milky Way, and about the same brightness as the Milky Way. There would be nothing to give away its actual size or its actual distance. Just another fuzzy gray thing in the sky.

It might have helped if Sirius (distance = 2.64 pc) were a hundred times closer (~0.02 pc) so that Tycho Brahe might have detected an annual parallax in sync with the "Sun's orbit".

In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of fixed stars.

---

<<Tycho Brahe (14 December 1546 – 24 October 1601) aspired to a level of accuracy in his estimated positions of celestial bodies of being consistently within an arcminute of their real celestial locations, and also claimed to have achieved this level. But, in fact, many of the stellar positions in his star catalogues were less accurate than that. The median errors for the stellar positions in his final published catalog were about 1.5', indicating that only half of the entries were more accurate than that, with an overall mean error in each coordinate of around 2'. Although the stellar observations as recorded in his observational logs were more accurate, varying from 32.3" to 48.8" for different instruments, systematic errors of as much as 3' were introduced into some of the stellar positions Tycho published in his star catalog — due, for instance, to his application of an erroneous ancient value of parallax and his neglect of polestar refraction Incorrect transcription in the final published star catalogue, by scribes in Tycho's employ, was the source of even larger errors, sometimes by many degrees.>>

[Chris Peterson]

I wonder how different Western history would have been had Andromeda been easily visible in the sky when the Roman Catholic Church decided that the whole of creation orbited the Earth. It would have been obvious that Andromeda was a system all of itself.

If we were closer to Andromeda, it would be bigger. But no brighter. The spiral structure would still be largely invisible to the eyes. It would look like a blob sticking off of the northern Milky Way, and about the same brightness as the Milky Way. There would be nothing to give away its actual size or its actual distance. Just another fuzzy gray thing in the sky.

It might have helped if Sirius (distance = 2.64 pc) were a hundred times closer (~0.02 pc) so that Tycho Brahe might have detected an annual parallax in sync with the "Sun's orbit".

Except at that distance Sirius would be inside our own Solar System, and there would be no planets with stable orbits. So there would be no Brahe to have detected it.

[neufer]

It might have helped if Sirius (distance = 2.64 pc) were a hundred times closer (~0.02 pc) so that Tycho Brahe might have detected an annual parallax in sync with the "Sun's orbit".

Except at that distance Sirius would be inside our own Solar System, and there would be no planets with stable orbits. So there would be no Brahe to have detected it.

Code: Select all

Sirius:
Radial velocity (Rv)	−5.50 km/s
Proper motion (μ)	RA: −1.44 Parallax/yr
Proper motion (μ)	Dec.: −3.23 Parallax/yr

Sirius is incoming at about 1.8 x 10^-5 c so its quite recent gravitational effects on the Solar System would probably not be significant yet.

At (full moon) magnitude −11.46 would no doubt be made another god, however. (Perhaps, I should have said if Barnard's Star (Radial velocity= −110.6 km/s) were a hundred times closer.)

[NCTom]

Thanks, Bystander, for the information and the guidance.

[E Fish]

I wonder how different Western history would have been had Andromeda been easily visible in the sky when the Roman Catholic Church decided that the whole of creation orbited the Earth. It would have been obvious that Andromeda was a system all of itself.

I'm not sure that follows. Even in the early 20th century, with the aid of telescopic observations, it was not obvious that Andromeda was a galaxy on its own. It, along with other spirals, were called spiral nebulae and were assumed by many to be within the bounds of the Milky Way. And that's with telescopes to show detailed observations. We know they're galaxies and separate systems because we've been taught that they are. If you're looking at them without that prior instruction, it takes quite a bit to discern their true natures. Even the Great Debate in 1920 wasn't enough to settle it, although it did set the course toward that resolution.