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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.
     
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