by Ann » Wed Mar 30, 2022 4:48 am
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johnnydeep wrote: ↑Tue Mar 29, 2022 2:05 pm
Cousin Ricky wrote: ↑Mon Mar 28, 2022 10:55 pm
johnnydeep wrote: ↑Mon Mar 28, 2022 9:22 pm
"Seen from Alpha Centauri, our own Sun would be a bright yellowish star in the otherwise recognizable constellation Cassiopeia."
Is this really saying the Cassiopeia would look about the same to us if we were standing on a planet around Alpha Centauri? At first think, that seems like it would be quite a coincidence. But on second thought, all it really means is that all the stars in Cassiopeia are much farther away from both the Sun and Alpha Centauri than they are from each other. And it also means that ALL familiar constellations would look pretty much the same from either star!
Except Cassiopeia and Centaurus, of course. And Canis Major, too; Sirius is close enough to both stars to show in greatly different directions.
What do you mean? Here's a list of stars in the constellation Cassiopeia -
https://en.wikipedia.org/wiki/List_of_s ... Cassiopeia. And these are the 5 main stars that make up the "W":
Code: Select all
Name B F Var HD HIP RA Dec v.mag. a.mag. Dist.ly Sp.class Notes
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α Cas α 18 3712 3179 00h 40m 30.39s +56° 32′ 14.7″ 2.24 −1.99 228 K0II-IIIvar Schedar
β Cas β 11 432 746 00h 09m 10.09s +59° 09′ 00.8″ 2.28 1.17 54 F2III-IV Caph; δ Sct variable, Vmax = 2.25m, Vmin = 2.29m, P = 0.10 d
γ Cas γ 27 5394 4427 00h 56m 42.50s +60° 43′ 00.3″ 2.47 −4.22 613 B0IV:evar Tsih, Navi; prototype γ Cas variable, Vmax = 1.6m, Vmin = 3.0m
δ Cas δ 37 8538 6686 01h 25m 48.60s +60° 14′ 07.5″ 2.68 0.26 99 A5Vv SB Ruchbah; Algol variable, Vmax = 2.68m, Vmin = 2.76m, P = 759 d
ε Cas ε 45 11415 8886 01h 54m 23.68s +63° 40′ 12.5″ 3.35 −2.31 442 B2pvar Segin; variable star, ΔV = 0.002m, P = 0.09 d
Is β Cas, at 54 ly, close enough to show a marked difference in position when viewed from Sol versus Alpha Centauri?
And all but one (Sirius) of the 10 brightest stars in Canis Major are closer than 60 ly to us. See
https://en.wikipedia.org/wiki/List_of_s ... anis_Major. Would any of them except Sirius show a marked difference in position when viewd from Sol versus Alpha Centauri?
I don't think that the "W" of Cassiopeia would change much as seen from Alpha Centauri, except for the addition of our own Sol:
Note that in the picture at left, the Sun is nearly as yellow as the yellowest star in Cassiopeia, Alpha Cas. That's not how it would be in reality. Alpha Cas is a star of spectral class K0III, with a B-V index of +1.12, whereas the Sun is spectral class G2V, with a B-V index of +0.656. That's a very obvious difference.
Note in the terribly tiny and blurry image at right of the skyscape as seen from Alpha Centauri that Sirius is right next to Betelgeuse in Orion. Note, too, that Sirius is markedly fainter as seen from Alpha Cas than when seen from the Earth. This may very well be true, because Sirius is one of the closest stars to the Earth, and it owes its high brightness as well as its position as seen from the Earth from its proximity to us. If Sirius is closer to us than to Alpha Centauri, the difference in its brightness as seen from Alpha Centauri would be noticeable right away.
But you have to admit that it would be fun to see still-bright blue-white Sirius right next to bright deeply golden-orange Betelgeuse. What a pair!
Ann
[float=][quote=johnnydeep post_id=321708 time=1648562758 user_id=132061]
[quote="Cousin Ricky" post_id=321696 time=1648508156 user_id=141376]
[quote=johnnydeep post_id=321689 time=1648502548 user_id=132061]
"Seen from Alpha Centauri, our own Sun would be a bright yellowish star in the otherwise recognizable constellation Cassiopeia."
Is this really saying the Cassiopeia would look about the same to us if we were standing on a planet around Alpha Centauri? At first think, that seems like it would be quite a coincidence. But on second thought, all it really means is that all the stars in Cassiopeia are much farther away from both the Sun and Alpha Centauri than they are from each other. And it also means that ALL familiar constellations would look pretty much the same from either star!
[/quote]
Except Cassiopeia and Centaurus, of course. And Canis Major, too; Sirius is close enough to both stars to show in greatly different directions.
[/quote]
What do you mean? Here's a list of stars in the constellation Cassiopeia - https://en.wikipedia.org/wiki/List_of_stars_in_Cassiopeia. And these are the 5 main stars that make up the "W":
[code]Name B F Var HD HIP RA Dec v.mag. a.mag. Dist.ly Sp.class Notes
----------------------------------------------------------------------------------------------------------------------------------------------------------
α Cas α 18 3712 3179 00h 40m 30.39s +56° 32′ 14.7″ 2.24 −1.99 228 K0II-IIIvar Schedar
β Cas β 11 432 746 00h 09m 10.09s +59° 09′ 00.8″ 2.28 1.17 54 F2III-IV Caph; δ Sct variable, Vmax = 2.25m, Vmin = 2.29m, P = 0.10 d
γ Cas γ 27 5394 4427 00h 56m 42.50s +60° 43′ 00.3″ 2.47 −4.22 613 B0IV:evar Tsih, Navi; prototype γ Cas variable, Vmax = 1.6m, Vmin = 3.0m
δ Cas δ 37 8538 6686 01h 25m 48.60s +60° 14′ 07.5″ 2.68 0.26 99 A5Vv SB Ruchbah; Algol variable, Vmax = 2.68m, Vmin = 2.76m, P = 759 d
ε Cas ε 45 11415 8886 01h 54m 23.68s +63° 40′ 12.5″ 3.35 −2.31 442 B2pvar Segin; variable star, ΔV = 0.002m, P = 0.09 d[/code]
Is β Cas, at 54 ly, close enough to show a marked difference in position when viewed from Sol versus Alpha Centauri?
And all but one (Sirius) of the 10 brightest stars in Canis Major are closer than 60 ly to us. See https://en.wikipedia.org/wiki/List_of_stars_in_Canis_Major. Would any of them except Sirius show a marked difference in position when viewd from Sol versus Alpha Centauri?
[/quote]
I don't think that the "W" of Cassiopeia would change much as seen from Alpha Centauri, except for the addition of our own Sol:
[float=left][img3="Cassiopeia as seen from Alpha Centauri. Photo: I don't know."]https://pbs.twimg.com/media/CqrIJpKWcAAMcRu?format=jpg&name=large[/img3][/float][float=right][img3="Small and blurry picture of a larger piece of sky as seen from Alpha Centauri. Note Sirius in Orion right next to Betelgeuse. Image: I don't know."]https://www.learnastronomyhq.com/_Media/sky-from-alpha-centauri_med.jpeg[/img3][/float]
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Note that in the picture at left, the Sun is nearly as yellow as the yellowest star in Cassiopeia, Alpha Cas. That's not how it would be in reality. Alpha Cas is a star of spectral class K0III, with a B-V index of +1.12, whereas the Sun is spectral class G2V, with a B-V index of +0.656. That's a very obvious difference.
Note in the terribly tiny and blurry image at right of the skyscape as seen from Alpha Centauri that Sirius is right next to Betelgeuse in Orion. Note, too, that Sirius is markedly fainter as seen from Alpha Cas than when seen from the Earth. This may very well be true, because Sirius is one of the closest stars to the Earth, and it owes its high brightness as well as its position as seen from the Earth from its proximity to us. If Sirius is closer to us than to Alpha Centauri, the difference in its brightness as seen from Alpha Centauri would be noticeable right away.
But you have to admit that it would be fun to see still-bright blue-white Sirius right next to bright deeply golden-orange Betelgeuse. What a pair!
Ann