APOD: Venus and the Sisters (2020 Apr 04)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3964
Joined: Fri Dec 04, 2009 3:27 am

APOD: Venus and the Sisters (2020 Apr 04)

Post by APOD Robot » Sat Apr 04, 2020 4:06 am

Image Venus and the Sisters

Explanation: After wandering about as far from the Sun on the sky as Venus can get, the brilliant evening star is crossing paths with the sister stars of the Pleiades cluster. Look west after sunset and you can share the ongoing conjunction with skygazers around the world. Taken on April 2, this celestial group photo captures the view from Portal, Arizona, USA. Even bright naked-eye Pleiades stars prove to be much fainter than Venus though. Apparent in deeper telescopic images, the cluster's dusty surroundings and familiar bluish reflection nebulae aren't quite visible, while brighter Venus itself is almost overwhelming in the single exposure. And while Venus and the Sisters do look a little star-crossed, their spiky appearance is the diffraction pattern caused by multiple leaves in the aperture of the telephoto lens. The last similar conjunction of Venus and Pleiades occurred nearly 8 years ago.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 10508
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by Ann » Sat Apr 04, 2020 5:42 am

The current magnitude of Venus is -4.4. The current distance to Venus is 96,755,805 kilometers. The apparent V magnitude of Alcyone, the brightest member of the Pleiades, is +2.87. The absolute V luminosity of Alcyone is some 2,000 L.

Some of the mathematically inclined members of Starship Asterisk* might want to calculate how much farther away Alcyone is compared to Venus, and how many times brighter Alcyone is compared to Venus. As icing on the cake, you might want to calculate how much brighter Venus is in our skies compared to Alcyone.

Ann
Color Commentator

User avatar
orin stepanek
Plutopian
Posts: 5504
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by orin stepanek » Sat Apr 04, 2020 12:39 pm

Even bright naked-eye Pleiades stars prove to be much fainter than Venus though]
Indeed Venus overwhelms the beauty of the Pleiades; of which I like so dearly! The Sisters will always hold a bright spot in my heart! 8-) 💖
VenusM45-2020Apr02-105x.jpg
You do not have the required permissions to view the files attached to this post.
Orin

Smile today; tomorrow's another day!

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17147
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by neufer » Sat Apr 04, 2020 2:23 pm

orin stepanek wrote:
Sat Apr 04, 2020 12:39 pm
Even bright naked-eye Pleiades stars prove to be much fainter than Venus though]
Indeed Venus overwhelms the beauty of the The Sisters will always hold a bright spot in my heart! 8-) 💖
  • Macbeth : Act IV, scene I
MACBETH: Saw you the weird sisters?

LENNOX: No, my lord.

MACBETH: Came they not by you?

LENNOX: No, indeed, my lord.

MACBETH: Infected be the air whereon they ride;
  • And damn'd all those that trust them!
-----------------------------------------------------------------
__ Hamlet (1603: "Bad" Quarto 1) Act 5 Scene 1
.........................................................
Hamlet: An excellent fellow by the Lord Horatio,
. This SEAUEN YEARES haue I noted it: the toe of the pesant,
. COMES so neere the heele of the courtier ,
. That hee gawles his kibe,
I prethee tell mee one thing,
. How long will a man lie in the ground before hee ROTS?

.
Clowne: I faith {SIR}, if hee be not rotten {B}efore
. HE BE laide in, {A}s we haue many pocky {C}orses,
. H(E) will last y{O}u, eight (Y)eares, *a TAN{N}ER*
. {WILL}(L)ast you eight yeare(S) full out, or nine.

Code: Select all

.             <= 17 =>
.
.  f a i t h {S I R} i f  h e e b  e n o
.  t R o t t e n [B] e f  o r e H  E B E
.  l A i d e i n [A] s w  E h a u  e m a
.  n Y p o c k y [C] o r  S e s H (E)w i
.  l L l a s t y [O] u e  I g h t (Y)e a
.  r E S A T A N [N] E R {W I L L}(L)a s
.  t Y o u e i g  h  t y  e a r e (S)a f
.  u l l o u t o  r  n i  n e.
.....................................................
[{SIR}BACON]   17: Francis [BACON] knighted in 1603
{WILL}(SLYE)  -17
Hamlet: And why A TANNER?
.
Clowne: Why his hide is so tanned with his trade,
. That it will holde out water, that's a parlous
. Deuourer of your dead body, a great soaker.

----------------------------------------------------
Art Neuendorffer

User avatar
Fred the Cat
Theoretic Apothekitty
Posts: 624
Joined: Mon Feb 22, 2016 4:09 pm
AKA: Ron
Location: Eagle, Idaho

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by Fred the Cat » Sat Apr 04, 2020 4:05 pm

The difference a day makes. :yes:
IMG_9449 (3).JPG
From a wider prospective - the view of the our winter constellations :thumb_up:
IMG_9449.JPG
I'll miss them as the days get longer :(
You do not have the required permissions to view the files attached to this post.
Freddy's Felicity "Only ascertain as a cat box survivor"

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17147
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by neufer » Sat Apr 04, 2020 7:46 pm

Ann wrote:
Sat Apr 04, 2020 5:42 am

The current magnitude of Venus is -4.4. The current distance to Venus is 96,755,805 kilometers. The apparent V magnitude of Alcyone, the brightest member of the Pleiades, is +2.87. The absolute V luminosity of Alcyone is some 2,000 L.

Some of the mathematically inclined members of Starship Asterisk* might want to calculate how much farther away Alcyone is compared to Venus, and how many times brighter Alcyone is compared to Venus. As icing on the cake, you might want to calculate how much brighter Venus is in our skies compared to Alcyone.
Alcyone Distance: 136 pc = 4,216,000,000‬ million km (vs. 96.756 million km for Venus)

Alcyone would be 38.2 magnitudes brighter (-35.33) if it was as close as Venus (-4.4).

From where it is, however, it is 7.27 magnitudes (~810 times) dimmer than Venus.
....................................................................................
Note: Alcyone is tens of millions of times more distant than Venus.
  • Venus is only hundreds of thousands of times more distant than the ISS.
If Alcyone were only hundreds of thousands of times more distant than Venus it would dominate the picture.
Last edited by neufer on Sat Apr 04, 2020 8:02 pm, edited 1 time in total.
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 10508
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by Ann » Sat Apr 04, 2020 7:56 pm

neufer wrote:
Sat Apr 04, 2020 7:46 pm
Ann wrote:
Sat Apr 04, 2020 5:42 am

The current magnitude of Venus is -4.4. The current distance to Venus is 96,755,805 kilometers. The apparent V magnitude of Alcyone, the brightest member of the Pleiades, is +2.87. The absolute V luminosity of Alcyone is some 2,000 L.

Some of the mathematically inclined members of Starship Asterisk* might want to calculate how much farther away Alcyone is compared to Venus, and how many times brighter Alcyone is compared to Venus. As icing on the cake, you might want to calculate how much brighter Venus is in our skies compared to Alcyone.
Alcyone Distance: 136 pc = 4,216,000,000‬ million km (vs. 96.756 million km for Venus)

Alcyone would be 38.2 magnitudes brighter (-35.33) if it was as close as Venus (-4.4).

From where it is, however, it is 7.27 magnitudes (~810 times) dimmer than Venus.
Thanks, Art, but how many times brighter is the absolute magnitude of Alcyone compared with the current magnitude of Venus?

Do the math, please? Please? Please?

Ann
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17147
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by neufer » Sat Apr 04, 2020 8:26 pm

Ann wrote:
Sat Apr 04, 2020 7:56 pm
neufer wrote:
Sat Apr 04, 2020 7:46 pm

Alcyone Distance: 136 pc = 4,216,000,000‬ million km (vs. 96.756 million km for Venus)

Alcyone would be 38.2 magnitudes brighter (-35.33) if it was as close as Venus (-4.4).

From where it is, however, it is 7.27 magnitudes (~810 times) dimmer than Venus.
Thanks, Art, but how many times brighter is the absolute magnitude of Alcyone compared with the current magnitude of Venus?
As stated above:

If Alcyone were as close as Venus its magnitude would be -35.33 or 30.93 magnitudes brighter than Venus.

Officially, however, absolute magnitude is defined differently for planets than for stars:
https://en.wikipedia.org/wiki/Absolute_magnitude wrote:
<<Absolute magnitude (M) is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly 10 parsecs (32.6 light-years), without extinction (or dimming) of its light due to absorption by interstellar matter and cosmic dust.

For planets and asteroids, the absolute magnitude (H) is defined as the apparent magnitude that the object would have if it were one astronomical unit (AU) from both the Sun and the observer, and in conditions of ideal solar opposition (an arrangement that is impossible in practice).>>
Art Neuendorffer

De58te
Science Officer
Posts: 296
Joined: Mon Sep 30, 2013 6:35 pm

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by De58te » Sat Apr 04, 2020 11:20 pm

Never mind how much brighter Venus is to Alcyone. I think it would be more interesting how much brighter the Sun is to Alcyone if the Sun was the same distance away as the Pleiades, or vice versa, how bright would Alcyone be if it was in the place of the Sun, 1 Astronomical Unit away?

User avatar
Ann
4725 Å
Posts: 10508
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by Ann » Sun Apr 05, 2020 6:45 am

De58te wrote:
Sat Apr 04, 2020 11:20 pm
Never mind how much brighter Venus is to Alcyone. I think it would be more interesting how much brighter the Sun is to Alcyone if the Sun was the same distance away as the Pleiades, or vice versa, how bright would Alcyone be if it was in the place of the Sun, 1 Astronomical Unit away?
According to Wikipedia, Alcyone is 2030 times brighter than the Sun. But Wikipedia also claims that Alcyone is 2,400 times brighter than the Sun.

The problem is that different sources disagree on how far away Alcyone is (the farther away it is, the intrinsically brighter it must be). But we must also define how we measure the brightness of stars.

Solar spectrum.png
The Sun's output of energy peaks in the visible part of the spectrum.
Spectrum for different kinds of stars.png
Hot stars peak in the ultraviolet part of the spectrum,
while cool stars peak in the infrared part of it.

















Alcyone is undoubtedly much brighter than the Sun even in the visible part of the spectrum. But Alcyone is also a hot star, with a temperature of about 13,000 K versus some 5,800 K for the Sun. My guess is that Alcyone is about 1,000 times brighter than the Sun in visible light. But the total (bolometric) brightness of Alcyone is certainly more than 2,000 times that of the Sun, because Alcyone emits so much ultraviolet light.

Ann
You do not have the required permissions to view the files attached to this post.
Last edited by Ann on Sun Apr 05, 2020 6:24 pm, edited 1 time in total.
Color Commentator

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17147
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by neufer » Sun Apr 05, 2020 4:25 pm

Ann wrote:
Sun Apr 05, 2020 6:45 am

Alcyone is undoubtedly much brighter than the Sun even in the visible part of the spectrum. But Alcyone is also a hot star, with a temperature of about 13,000 K versus some 5,800 K for the Sun. My guess is that Alcyone is about 1,000 times brighter than the Sun in visible light. But the total (bolometric) brightness of Alcyone is certainly more than 2,000 times that of the Sun, because Alcyone emits so much ultraviolet light.
Absolute magnitude (MV):
  • Alcyone: -2.62
    Sun: +4.83
Visual Magnitude Difference = 7.45

955 = 10(7.45/2.5)
Art Neuendorffer

TheZuke!
Science Officer
Posts: 165
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Venus and the Sisters (2020 Apr 04)

Post by TheZuke! » Mon Apr 06, 2020 2:16 pm

We've had overcast skies that past several evenings.
Alas and alack!