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I Are almost all stars in the night sky brighter than the Sun?

  1. Mar 15, 2016 #1
    I was thinking about adding another page to my website concerning the nearest stars, the brightest stars, etc. In a list of the nearest stars, the vast majority are brighter than the Sun. (I looked for stars with an absolute magnitude that was greater than the Sun's (4.85) and had a visual magnitude less than 6.) Such stars are not well-known and among them are:
    alpha Centauri B
    epsilon Eridani
    61 Cygni A
    tau Ceti

    Does anyone know if there is a statistic for this? (I doubt I'm the first one of think of this.)
     
  2. jcsd
  3. Mar 15, 2016 #2

    russ_watters

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  4. Mar 15, 2016 #3

    Drakkith

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    Huh? Wikipedia's list of nearest stars and brown dwarfs has only three out of around fifty that are brighter than the Sun. Are you looking at only the stars that can be seen visually?

    Nope. The vast majority of stars are smaller and dimmer than the Sun.
     
  5. Mar 15, 2016 #4

    DaveC426913

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    The link Russ posted seems to suggest otherwise. Though I think the issue is one of sampling. They mention the sun's neighborhood.
     
  6. Mar 15, 2016 #5

    Drakkith

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    That's not how I'm reading that graph. Larger numbers are dimmer, right?
     
  7. Mar 15, 2016 #6

    DaveC426913

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    Ah. My bad.
    I assumed absolute mags would be positively increasing.
     
  8. Mar 15, 2016 #7
    Drakkith you asked "Are you looking at only the stars that can be seen visually?"
    Yes - geez I should have stated that question more clearly.
    Apparently, this site does not like long questions so I kept editing my question until it "fit", thereby editing out the part about "stars of visual magnitude".
     
  9. Mar 15, 2016 #8

    russ_watters

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    Hehe - while what I posted was vague enough not to be wrong, I read it backwards! D'oh! :oops:
     
  10. Mar 15, 2016 #9

    russ_watters

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    You mean the title of the thread? That should just be a brief subject: the detailed question should be in the post.
     
  11. Mar 15, 2016 #10
    Yes, I did ask in the posting (I looked for stars with an absolute magnitude that was greater than the Sun's (4.85) and had a visual magnitude less than 6.) but it would have helped if the topic title (or thread title is stated clearly). :frown:
     
  12. Mar 15, 2016 #11

    Fervent Freyja

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    Maybe this will help. It includes some charts, gives useful instruction, and is loaded with plenty of resource links:

    http://pumas.jpl.nasa.gov/files/03_05_10_2.pdf

    "Studies of a Population of Stars: How Bright Are the Stars, Really?
    OBJECTIVE: Make night sky observations of star brightness and color and use available data and simple calculations to correlate these observations with the characteristics of stars. In this activity, the distances to bright stars are calculated. The apparent brightnesses of these stars are then adjusted for distance to see which stars are intrinsically bright and which only appear bright because of their proximity to Earth."
     
  13. Mar 16, 2016 #12

    Janus

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    If I understand your question correctly, you are asking if the vast majority of the naked-eye visible stars we see in the night sky are more luminous than the Sun. The answer is yes. Our sun would only be naked eye visible (have a visual magnitude of >6) if its distance was less than 55.33 ly away. The vast majority of stars we see in the sky are further away than that.
    However, most actual stars are dimmer than the Sun.
    For instance, here are two images, one shows all the naked-eye visible stars within 17.75 ly from Earth, the other shows all the stars in that same volume (50)
    Our Sun is in the center of this image.
    stars3v001.png
    Stars visible mag <6

    stars3a001.png
    All stars
     
  14. Mar 16, 2016 #13
    Within 10 pc, the stars brighter than +6 and absolute magnitude dimmer than Sun are:
    (Not Alpha Centauri B, because not resolved from A which is brighter than Sun)
    1. Epsilon Eridani 3,72/6,18
    2. 61 Cygni AB about 4,8/7,49+8,31, dimmest visible star
    3. Epsilon Indi 4,69/6,89
    4. Tau Ceti 3,49/5,68, brightest star dimmer than Sun
    5. Omicron Eridani 4,43/5,92
    6. 70 Ophiuchi 4,24/5,71
    7. Sigma Draconis 4,67/5,87
    8. 36 Ophiuchi ABC about 4,2/6,18+6,22+7,45
    9. 82G Eridani 4,26/5,35
    10. Xi Bootis AB about 4,6/5,59+7,84
    11. Gliese 105 5,79/6,50
    12. HD 4628 5,74/6,38
    13. 107 Piscium 5,24/5,87
    14. Mu Cassiopeiae 5,17/5,87
    15. P Eridani AB about 5,1/6,27+6,40
    16. 61 Virginis 4,74/5,09
    17. G Arae 5,55/5,83
    18. HD 192310 5,73/6,00
    19. Kappa1 Ceti 4,84/5,03
    20. HD102365 4,89/5,06
    21. 61 Ursae Majoris 5,31/5,41
    22. HR 4458 5,96/6,06
    23. 12 Ophiuchi 5,77/5,82
     
  15. Mar 16, 2016 #14
    Well those were very good replies (especially, snorkack's list of 23 stars).
    There are about 6,000 stars visible in the night sky. (apparent magnitude 6 or brighter).
    Then, it's safe to say that of all the stars that can be seen with the unaided eye in the night sky, more than 99% of those are brighter than the Sun.
    Thanks again everyone. :oldsmile:
     
  16. Mar 16, 2016 #15
    That makes sense, while most of the stars in the universe are smaller and dimmer than the sun, the ones that are visible to us will obviously be brighter. Barnard's Star, one of the closest to us isn't visible at all with the eye.
     
  17. Mar 16, 2016 #16
    Continuing the list past 10 pc
    1. HR 511 5,63/5,64
    2. Alpha Mensae 5,08/5,05
    3. 54 Piscium 5,88/5,65
    4. 11 Leonis Minoris 5,40/5,16
    5. Zeta1 Reticuli 5,53/5,11
    6. 85 Pegasi 5,81/5,34
    7. 55 Cancri 5,96/5,47
    8. HD 69830 5,95/5,45
    9. HD 104304 5,54/4,99
    10. HD 172051 5,85/5,28
    11. 58 Eridani 5,63/5,01
    12. HD 166 5,92/5,23
    13. Pi1 Ursae Majoris 5,63/4,86
    14. Psi Serpentis 5,86/5,03
    15. HD 4391 5,80/4,93
    That´s up to 15 pc. Total 38.
    Checking the list for the range 15 to 17 pc is a bit more complicated, need a different source.
     
  18. Mar 16, 2016 #17

    Janus

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    And for comparison, there are a total of 47 stars within that same distance, which have a visible magnitude of <6, which means that 14 of them have absolute magnitudes brighter than the Sun. This is out of a total of 184 total known stars in that same volume.
     
  19. Mar 16, 2016 #18

    Janus

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    Which is out of a total of ~71 stars of <6 visual magnitude from 10 to 15 pc or a total of 118 <6 magnitude stars and a total of 513 stars in all.
     
  20. Mar 16, 2016 #19

    Janus

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    It's funny, another post sent me off on a tangent which led to me creating the images I posted above. They are single frames from an animation I was working on. I wasn't sure where I'd find a use for it, and then this thread starts. I just finished loading the video to YouTube. It isn't as clear as the images and in the upload, the colors were washed out, (the colors were to show the actual black body colors of each star by spectral class, and I put quite a bit of work into converting black body temp to RGB values and entering them for each individual star, so this bummed me out a bit.), but at least the brightness of the stars still represents absolute magnitude.
    It starts out with just the stars of <6 visual magnitude and then brings in all 50 stars.
     
  21. Mar 16, 2016 #20
    Um... 24?
    1. Alpha Centauri AB -0,27/4,34+5,71
    2. Sirius -1,46/1,42
    3. Procyon 0,34/2,65
    4. Altair 0,76/2,20
    5. Eta Cassiopeiae 3,46/4,59
    6. Delta Pavonis 3,55/4,62
    7. Beta Hydri 2,82/3,45
    8. Vega 0/0,58
    9. Fomalhaut 1,17/1,74
    10. Pi3 Orionis 3,19/3,67
    11. Chi Draconis AB 3,57/4,15+6,14
    12. Mu Herculis 3,42/3,80
    13. Beta Canum Venaticorum 4,24/4,63
    14. Zeta Tucanae 4,23/4,56
    15. Chi1 Orionis 4,23/4,70
    16. Xi Ursae Majoris AB 3,79/4,25+5,07
    17. Gamma Leporis A 3,59/3,83
    18. Delta Eridani 3,52/3,74
    19. Beta Comae Berenices 4,23/4,42
    20. Gamma Pavonis 4,23/4,39
    That´s it. My list does not match yours.
    Note that out of the 20, 9 have absolute magnitudes over +4,10. The significance of that threshold being that it is double the brightness of Sun.
    My list of 23 contains 6 stars with absolute magnitudes under 5,60. Which is half the brightness of Sun.
     
  22. Mar 16, 2016 #21

    marcus

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    I cant tell but you might be missing the crucial fact that the "absolute magnitude" scale is backwards---a higher magnitude number means dimmer (not brighter).
    If not, fine. This may be obvious but it hasn't been explicitly mentioned in the thread so just in case any reader is confused I'll say it.
    Really really bright objects have to have NEGATIVE absolute magnitude numbers.
    ==quote Wikipedia https://en.wikipedia.org/wiki/Absolute_magnitude ==
    A difference of 1.0 in absolute magnitude corresponds to a difference of 2.512 ≈ 100.4 of absolute brightness.
    ==endquote==
    Therefore a star of magnitude 2 is 2.512 times brighter than a star of magnitude 3, in output watts that is.
    and therefore a star of magnitude -2 is 100 (or 2.5125) times brighter than a star of magnitude 3.
    The abs mag 2 star is about 2.5 time brighter than the abs mag 3 star, in terms of real wattage output.
    So brightness (watts) is NOT the same as magnitude

    FWIW here are some figures from Wikipedia on APPARENT magnitude.
    −0.27 The total magnitude for the Alpha Centauri AB star system. (Third-brightest star to the naked eye)
    −0.04 Fourth-brightest star to the naked eye Arcturus[21]
    −0.01 Fourth-brightest individual star visible telescopically in the sky Alpha Centauri A
    +0.03 Vega, which was originally chosen as a definition of the zero point[22]
    +0.50 Sun as seen from Alpha Centauri

    So the sun is a dimmer star than Alpha Centauri A. At their separation distance Sun has apparent magnitude 0.5 while Alpha Centauri A has apparent magnitude close to zero---i.e. is brighter, more wattage.
    I see that VEGA was originally chosen to be the standard zero on the apparent magnitude scale.
     
    Last edited: Mar 16, 2016
  23. Mar 16, 2016 #22

    Janus

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    right, 24. Though not really, check below)
    Going over our lists, this is the comparison I got. Below Is my list. Blue represent stars with an absolute magnitude brighter than the Sun, and seems to match up with yours. The red highlighted stars are ones that are on my list but not yours (we used different designations for some stars, but I was able to cross-match.)
    All 4 are dimmer than the Sun stars (which is Why I came up with 24 rather than 20; I didn't check my list of dimmer stars against yours.).
    I queried the Hipparcos Main Catalogue, using the VizieR system, setting the constraints to <6 visual magnitude and >100 milliarcseconds of parallax. The system only listed the visual magnitude and I had to calculate the absolute mag from that and the parallax.
    alpha Centauri A -0.01/ 4.34
    Sirius (Alpha Canis Majoris) -1.44/ 1.45
    Epsilon Eridani b 3.72/ 6.18
    61 Cygni 5.2/ 7.49
    Procyon( Alpha Canis Minoris) 0.4/ 2.68
    Episilon Indi 4.69/ 6.89
    Tau Ceti 3.49/ 5.68
    40 Eridani 4.43/ 5.92
    70 Ophiuchi 4.03/ 5.50
    Altair( Alpha Aquilae) 0.76/ 2.20
    Sigma Draconis 4.67/ 5.87
    Gliese 570(33 G. Librae) 5.72/ 6.86
    Eta Cassiopeiae 3.46/ 4.59
    36 Ophiuchi 4.33/ 5.44
    Gliese 783(279 G. Sagittaii) 5.32/ 6.41
    82 G. Eridani 4.26/ 5.35
    Delta Pavonis 3.55/ 4.62
    BD+56 2966 5.57/ 6.50
    Xi Bootis 4.54/ 5.41
    Gliese 667(142 G. Scorpii) 5.91/ 6.69
    Gliese 105(268 G.Ceti) 5.79/ 6.50
    96 G. Piscium 5.74/ 6.38
    107 Piscium 5.24/ 5.87
    Beta Hydri 2.82 3.45
    Mu Cassiopeiae 5.17/ 5.78
    Fomalhaut(Alpha Piscis Austrini) 1.17/ 1.74

    Vega(Alpha Lyrae) 0.03/ 0.58

    Tabit(Pi3 Orionis) 3.19/ 3.67

    Chi Draconis 3.55/ 4.02

    p Eridani 5.76/ 6.21
    Chara(Beta Canum Venaticorum) 4.24/ 4.63

    Mu Herculis 3.42/ 3.80

    61 Virginis 4.74/ 5.09
    Zeta Tucanae 4.23/ 4.56

    Chi1 Orionis 4.39/ 4.70

    41 G.Arae 5.47/ 5.75
    Gliese 785 5.73/ 6.00
    Gamma Leporis 3.59/ 3.83

    Delta Eridani 3.52/ 3.74

    Beta Comae Bernices 4.23/ 4.42

    Kappa 1 Ceti 4.84/ 5.03
    Gamma Pavonis 4.21/ 4.39
    66 G. Centauri 4.89/ 5.06
    289 G. Hydrae 5.96/ 6.06
    61 Ursae Majoris 5.31/ 5.41
    12 Ophiuchi 5.77/ 5.82
    Gliese 75 5.63/ 5.64
     
  24. Mar 16, 2016 #23

    marcus

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    I don't follow. Wiki says the absolute magnitude of the Sun is 4.83
    If something has abs mag MUCH over 4, say it has abs mag 5, then it would be LESS BRIGHT than the sun. If abs mag 6, then even dimmer.
    can someone explain? are we using different terminology.

    greater magnitude means dimmer, apparent magnitude takes account of the distance, absolute magnitude is what it would be at a standard distance of 10 parsecs. so if the distance is more than 10 parsecs (32.6 LY)
    and you see two numbers like "4,10" the second number is probably the apparent magnitude (dimmer because farther away)
     
    Last edited: Mar 16, 2016
  25. Mar 16, 2016 #24
    marcus, I would assume that when a number is written such as "4,10" (as snorkack did in his lists) it is just one number and not two and it actually means 4.10.
    Anyway, since snorkack went through so much wok, I figured I'd combine both lists and put those on my website:
    http://www.1728.org/starsvis.htm
     
  26. Mar 17, 2016 #25
    Most of the stars visible to the naked eye are brighter than the Sun.
    However most stars are less bright than the Sun.
     
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