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					                                                           IAC-04-IAA-1.1.1.06



                                                         SEARCHING FOR
                                                         DYSON SPHERES
                                                          WITH PLANCK
                                                        SPECTRUM FITS TO
                                                              IRAS
                                                           Dick Carrigan
                                                             Fermilab


Infrared Processing and Analysis Center, Caltech/JPL.
IPAC is NASA's Infrared Astrophysics Data Center.
The radio SETI paradigm

                                       A substantial fraction of sun-like stars out to
                                       several hundred light years have been
                                       monitored for ETI with radio SETI.


                                       SETI radio beacon (acquisition signal)
                                       –but why?


                                       Material and electromagnetic ET
                                       artifacts like a Dyson Sphere don’t require
                                       reason to communicate

 Credit: Allen Telescope
International Astronautical Congress              Vancouver
                                                                                2
D. Carrigan - Fermilab                       Oct. 4 – Oct. 8, 2004
Cosmic archaeology
Kardashev civilizations: I-planet, II-star,
  III-galaxy
 Annis-JBIS 52, 33 (1999)-elliptical gal
    log(v dispersion)+sur bright (mag) vs
       log radius
    outlier line 1.5 mag or 75% of energy
Salting with unusual atomic lines –
         Technetium-Drake and Shklovskii – 105 tons.
Nuclear waste disposal
Star lifting (D. Criswell)
Salting star to change Hertzsprung-Russell curve-
   unlikely
   may require too much material
… and Dyson Spheres
G. Lemarchand, SETIQuest, Volume 1, Number 1, p. 3. On the web at http://www.coseti.org/lemarch1.htm


  International Astronautical Congress                   Vancouver
                                                                                                       3
  D. Carrigan - Fermilab                            Oct. 4 – Oct. 8, 2004
     Dyson spheres                                           Rigid Dyson sphere is unstable
                                                               instead swarm of smaller pieces
                                                             Energy to assemble
                                                               800 solar years to take Jupiter apart
                                                             Types
                                                               pure – star completely obscured
                  Venus        Sun                             partial
              Types of Dyson Spheres -
                     R=1.5*108 km                            Signature
                …pure, partial, rings,                         infrared
                     Dyson Sphere                              stellar luminosity (distance problem)
                      4 mm thick                               pure Planck
                                         Infrared
                                                               no star for pure DS
                                         radiation
                                                             Searches-problem fixing distance
Based on www.daviddarling.info/encyclopedia/D/Dysonsp.html


  Sagan and Walker, Astrophysical Journal 144(3), 1216 (1966)
    search feasible even with sixties technology but that the possible confusion
    with natural signatures could require searches for other artifacts of intelligence
Dyson Sphere surrogates

                           ←Planetary nebula from IRAS dumbbell M22.
                             IRAS 06176-1036 “Red Rectangle” →


                             Mira (Omicron Ceti) in visible (Hubble image)
                              Miras variables, short-lived, circumstellar dust
                              Sum of many Planck spectra
                              Also C stars


                             Protostars forming in Orion dust cloud
                               (IRAS image)

                              Brown dwarfs but temperature is typically higher
                                absolute luminosity is lower
International Astronautical Congress          Vancouver
                                                                                 5
D. Carrigan - Fermilab                   Oct. 4 – Oct. 8, 2004
Earlier searches
Jugaku and Nishimura, Bioastronomy 2002: Life Among the Stars,
  Norris and Stootman, eds, IAU Symposium, 213, 437 (2002) and earlier
  use the 2.2 μm K band as an indicator of the photospheric radiation
  of a star hosting a partial Dyson Sphere and then look for an
  infrared excess in the IRAS infrared satellite 12 μm band
  1 mag difference for 1% sphere. See less than 0.3 mag for 384 stars inside 25 pc.
Slysh, in The Search for Extraterrestrial Life: Recent Developments, Papagiannis (Ed)
1985. Timofeev, Kardashev, and Promyslov, AAJournal, 46, 655 (2000) [TKP]
  Four band IRAS Planck fit. Several candidates, limited sky. 100, 300 °K. 98 stars
Conroy and Werthimer, preprint (2003)
  Jugaku technique to older stars. 1000 nearby older stars from Wright and Marcy
  Older stars eliminate thick dust clouds around young stars
  Correlate with the K band near-infrared ground based data from 2MASS
  33 candidates in the 12 μm IRAS band with 3 σ excesses from mean.
Globus, Backman, and Witteborn, preprint (2003)
  look for a temperature/luminosity anomaly due to the fact that the luminosity of a star
  surrounded by a partial DS would be lowered compared to naked star with same T
IRAS
                                                                     Requirement for Dyson Sphere search
                                                                       all sky – useful
                                                                       100 < T < 600 °K

                                                                     Only available all-sky survey at 12 μm
                                                                       12, 25, 60, 100 μm micron filters
                                                                      A main purpose – dust, mirror only 0.6 m
                                                                         cosmic cirrus problems in 100, 60 μm

                                                                     Performance
                                                                       sensitivity – 0.5 Jy 12 – 60 μm,
2MASS                                                                     1 Jy for 100 μm
  much more sensitive,                                                 250 K point sources
    500 M point sources
                                                                       angular resolution – O(1')
  IRAS 12 μm must be at least 10 Jy to
    register in the 2MASS 2.17 μm filter                               positional – 2 to 6" in-scan, 8 – 16" cross

Picture from Infrared Processing and Analysis Center, Caltech/JPL.
IPAC is NASA's Infrared Astrophysics Data Center.
  International Astronautical Congress                      Vancouver
                                                                                                         7
  D. Carrigan - Fermilab                               Oct. 4 – Oct. 8, 2004
Analysis

      Infrared cirrus
         significant presence of emission in the 100 μm band
           on a wide range of angular scales from so-called
           infrared cirrus due to interstellar dust
        often well above Planck
        do not use 100 μm for fit
           (Slysh and TKP used all four filters)


      Flux quality factors, FQUAL(i)
        do not use if only an upper limit
           leaves 19572 sources
        limits upper temperature range
           e. g. missing 60 μm looks like high temperature DS

     Temperature range
       limited to 150 to 500 °K

International Astronautical Congress        Vancouver
                                                                8
D. Carrigan - Fermilab                 Oct. 4 – Oct. 8, 2004
             Planck fitting (IRAS 06176-1036 “Red Rectangle”)

                                 LSQ                                                                  Planck fit
             4.0                                                                       1.6
                                                                                                                   Flux/k
             3.6
                                                                                       1.4                         P*amin
             3.2
                                                                                       1.2                         2MASS
             2.8




                                                                        F/K, P*a min
LSQ(T)*1E6




                                                                                                                   Planck
             2.4                                                                       1.0
                               T = 313 °K                                                                          Planck inter
             2.0
                                                                                       0.8
             1.6
             1.2                                                                       0.6
             0.8                                                                       0.4
             0.4
                                                                                       0.2
             0.0
                   100   200    300           400   500        600                     0.0
                                                                                             0   20   40     60    80         100
                                      T(°K)
                                                                                                         (m)



                              F / K  a P  
                                                          2

              LSQn (Tm )    nk km 2 nm km 
                                             
                                                                        Solid red is trial fit to three points
                           k         km                              Dotted is final fit
     F is IRAS flux, K is Planck color correction,
     P is Planck dist., sigma is weight, and a is fit para

International Astronautical Congress                           Vancouver
                                                                                                                                  9
D. Carrigan - Fermilab                                    Oct. 4 – Oct. 8, 2004
      Color color fitting                                   Follow Pottasch et al. AA 205, 248 (88), Fig. 1

                 Left is 12/25, rt 25/60
                                                                                                                           500
    1000                                                                                                                   400
                                                                                  1
                                                                                                                           300




                                                                  F(12)/F(25)
T



                                                                                                                           200
    100
           0                                         5
                   f(12)/f (25), f (25)/f (60)

               Fit with arbitrary polynomial                                0.1
                                                                                       0.4   0.6 0.8 1            3
       Tel  c0   ckl ( f a / f b )                k
                                                                                                F(25)/F(60)
                               k
                                                                                      Diamonds are extragalactic
Each pair gives a black body temperature
                                                                                      Dots - no catalog entry, pure DS
  line shows equal pairs, dots BB temp
                                                                                      Dyson Spheres along BB line
      International Astronautical Congress                    Vancouver
                                                                                                                      10
      D. Carrigan - Fermilab                             Oct. 4 – Oct. 8, 2004
       Relation of color-color fits to Planck fits: no star
                                              2T 12 / 25   T 25 / 60 
                                   dT / T 
                                              T 12 / 25  T 25 / 60 
                               ↓blackbody




              The lowest LSQ rises quickly as dT/T moves away from 0
                 By dT/T = 0.2 LSQ almost half of the maximum LSQ at dT/T = 0
                 may be possible to rule out LSQ values greater than 1-2E-7
              There is a direct relation between dT/T and LSQ

International Astronautical Congress               Vancouver
                                                                                11
D. Carrigan - Fermilab                        Oct. 4 – Oct. 8, 2004
              dT/T distribution from color color fitting
                                                ↓blackbody line




    No obvious peaking at dT/T = 0 where pure Dyson Sphere should be
    370 sources with no catalog entry between -0.1 < dT/T < 0.1
      so that 1 out of every 600 IRAS sources in interval
      However distribution statistically flat in the region of dT/T = 0
    A 3 σ peak in one bin might require about 25 sources
      or one in 10,000 of the IRAS sources.
International Astronautical Congress        Vancouver
                                                                    12
D. Carrigan - Fermilab                 Oct. 4 – Oct. 8, 2004
Future plans
Determining the absolute luminosity
   need distance to source
   possible ways to determine distance
     clusters like Pleiades
     multiple star system
     center of galaxy at 8 kpc
     partial of Jugaku or Dyson Sphere – use source distance of companion
The Pleadies
  at 125 pc contains about 1200 objects
  subtends a field of roughly four square degrees or approximately 10-4 of the sky
  contain about 25 members of a randomly distributed sample of 250K sources
Thus association with a nearby cluster will be a useful tool for less than 0.1%
  of the objects in IRAS sample
Small dT/T Dyson Sphere candidates
  individual cases need to be matched with other information available on the source
  Following TKP one can look for further information from mm wave measurements,
     2MASS, or even additional measurements using SIRTF

International Astronautical Congress        Vancouver
                                                                                13
D. Carrigan - Fermilab                 Oct. 4 – Oct. 8, 2004
                 Summary
      Artifacts like pyramids, Dyson
      Spheres and Kardashev civilizations                              Dyson Sphere
      are “natural” and don’t require
      purposeful signals                                                        Ir rad


      IRAS good-whole sky, problems-angular
        resolution. Still-best compromise.
      At 3 σ in one bin is 1 in 10,000 of IRAS
                                                                      1.6




   Can get good black body fits and do find                           1.4

                                                                      1.2




                                                       F/K, P*a min
                                                                      1.0


     candidates but there are surrogates like the                     0.8

                                                                      0.6



     planetary nebula “Red Rectangle”                                 0.4

                                                                      0.2

                                                                      0.0
                                                                            0   20   40            60   80   100
                                                                                           (m)




For pure Dyson Spheres do need distance
to get luminosity. Clusters, galactic center, Virgo?
                                                                                           14
                                       Questions?




International Astronautical Congress         Vancouver
                                                                15
D. Carrigan - Fermilab                  Oct. 4 – Oct. 8, 2004
International Astronautical Congress        Vancouver
                                                               16
D. Carrigan - Fermilab                 Oct. 4 – Oct. 8, 2004

				
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