SF State Observatory

Fall 2024 Public Open Nights

September & October: Mondays, Wednesday, Thursdays only.

November & December: Mondays, Wednesdays, Thursdays, and Fridays.

How to get to the observatory

1.    Take the elevator to the 9th floor of Thornton Hall.
2.    Find the stairwell close to the elevator.
3.    Walk to the top of the stairs.
4.    The door to the observatory will be on your LEFT.

Weather updates

For up-to-date information about whether the skies are clear and the Observatory is open, check Instagram: SF State Observatory on Instagram

RECOMMENDED TARGETS FOR FALL 2024

PLANETS 

  Saturn  (all semester!)
  Venus  (Nov/Dec, possibly also in October though it will be low in the west)
  Jupiter (Nov/Dec)
  Uranus (Oct-Dec)
  Neptune (all semester)

BINARY STARS 

  Albireo  ("eye of the swan" in Cygnus)
  eta Cassiopeiae (a solar twin with a low-mass, faint stellar companion just 70AU away from it)
  gamma Andromedae (two colors, very nice)
  epsilon Lyrae  ("double double star";  quadruple... in very good conditions you can see all four!)
  Mizar and Alcor (Mizar is the visual binary that splits into Mizar A and Mizar B)

OPEN STAR CLUSTERS

  M11 ("Wild Duck" cluster in Scutum)
  double cluster in Perseus, 
  Pleiades (in Taurus)
  Hyades (in Taurus; point at Aldebaran to find it)

GLOBULAR STAR CLUSTERS

  M22 (in Sagittarius)
  M4 (in Scorpius near Antares; 2nd nearest globular cluster to the Sun)
  M13  (in Hercules)
  M92 (also in Hercules)
  M15 (in Pegasus; some studies suggest it harbors a central black hole; still controversial)

NEBULAE

  M57  (Ring Nebula in Lyra, a planetary nebula)
  M27  (Dumbell Nebula in Vulpecula, a planetary nebula)
  M42  (Orion Nebula, a star-forming region–late in the semester only)

GALAXIES

  M31  (Andromeda galaxy)
  M32  (dwarf elliptical galaxy that is a satellite of M31)
  M110 (another fainter dwarf elliptical galaxy that is also a satellite of M31)
  M33  (in Triangulum)

SINGLE STARS OF INTEREST

1.  Barnard's star  (nearest star to sun visible from northern hemisphere!)
  
        RA =  17h 57m 48.5     Dec = +4d 41' 36"

It's in Ophiuchus, so you need to catch it early in the semester.  At a distance of just 1.8 pc (6.0 lightyears), this is the nearest star to the Sun after Proxima and alpha Cen (neither of which are visible from SF).  It is quite faint, with magnitude = 9.5, but should be visible in 12" telescopes.

       m_V = 9.5
       B-V = 1.7  (similar to Antares --> reddish hue will hopefully be noticeable)
       spectral type = M4V  (M dwarf)
       mass = 0.14 Msun  (very low mass!)
       surface temp = 3100 K  (very cool for a star)
       luminosity = 0.0004 Lsun (intrinsically VERY faint!)

 2.  Antares  (red supergiant)  in Scorpius  ("rival of Mars")

      radius ~ 880 Rsun   
      mass ~ 12 Msun       
      spectral type M1.5Iab    
      L ~ 58,000 Lsun    
      distance ~ 170 pc

 3.  Betelgeuse  (red supergiant) (late in the semester only)

      radius ~ 890 Rsun   
      mass ~ 12 Msun       
      spectral type M1–M2 Ia–ab    
      L ~ 100,000 Lsun (!!)        
      distance ~ 200 pc

 4.  mu Cephei  (known as the "garnet star" for is deep orange/red hue)

          RA =  21h 43m 30.5s    Dec = +58d 46' 48"

    This is one of the largest and most luminous stars known in the Milky Way.  Check it out!
          L ~ 280,000 Lsun (!!)     R ~ 1300 Rsun (!!!)
          mass ~ 19 Msun
          distance ~ 1800 pc  (~6000 ly) (!!)  probably one of most distant naked eye stars...
          m_V = 4.1  (just barely naked eye in SF? see easily with binoculars, but use 12" to see it well)

5.  sigma Orionis  (a rare O-type star) (late in the semester only)

The brightest star in this group of 6 stars is one of the hottest, youngest, most massive stars around.
Actually, it's an unresolved triple system, made up of three massive main-sequence stars (18, 14 and 13 Msun) (!)   The hottest one is an "O" star with:

         m_V = 4.1
         spectral type O9.5V
         T ~35,000 K 
          L ~ 42,000 Lsun  (!!)

This will only be visible late in the semester.    

6.  40 Eridani B   (a white dwarf !)

    This is a white dwarf that we have a shot at seeing from the SF State Observatory!
    It's a member of a triple system, in a wide enough orbit that the three stars are
    all well separated from one another.  It's faint, so it will be challenging, but worth 
    the effort!  It also happens to be the first white dwarf ever to have been discovered...

    This object rises about an hour before Rigel in Orion, so catch it late in the semester.
    Here are details about the three components of the triple system.  

            40 Eri A:   mV = 4.4    K0.5V      B-V = 0.82    0.8 Msun   T ~  5,300 K
            40 Eri B:   mV = 9.5     DA4        B-V = 0.03    0.5 Msun   T ~ 16,500 K
            40 Eri C:   mV = 11.2  M4.5eV    B-V = 1.67    0.2 Msun   T ~  3,100 K

40 Eri A is a naked-eye star.  The two other members of the system, B and C, are much fainter and about 83" away from 40 Eri A.  B/C separation is about 9".  We may or may not be able to see 40 Eri C, but it would be neat if we could.   Worth trying in the 16" as well as in the 12" to try for that.   The color contrast between B/C is huge (a hot white dwarf vs. a very red main-sequence star).

Sources:  

   http://stars.astro.illinois.edu/sow/keid.html
   https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs
   https://en.wikipedia.org/wiki/List_of_white_dwarfs#Nearest

Fun reading re: Albireo:   http://www.skyandtelescope.com/observing/will-the-real-albireo-please-s…

 
THINGS TO LOOK FOR WITH UNAIDED EYES

       *  Summer Triangle

       *  Cygnus and the "eye of the swan" (Albireo)

       *  Big Dipper and the north star (and how to get from one to the other)
            (dipper visible only early in semester)
  
       *  Great Square of Pegasus

       *   Cassiopeia  (point out solar twin "eta Cas" and tell them it's about 
           20 lightyears from Earth... that's a little over 100 trillion miles :)

       *  Orion (including belt and sword); see if visitor can notice the difference
             in color between Betelgeuse (left shoulder) and Rigel (right foot).
         (toward end of semester)

       *  Pleiades star cluster in Taurus (~400 lightyears away and about 100 million yrs old)
                (late in semester)

       *  Aldebaran and the V-shaped "face of the bull"  (about 150 ly away and 600 Myr old)
            (itself a beautiful star cluster called the Hyades, excellent in binoculars)
       (late in semester)

       *  "Winter Hexagon"  (very late in semester, very end of night)
             Rigel --> Aldebaran --> Capella --> Pollux --> Procyon --> Sirius
            (Orion)    (Taurus)     (Auriga)    (Gemini)  (Canis Minor)(Canis Major)