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

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.

International Astronautical Congress Vancouver

D. Carrigan - Fermilab Oct. 4 – Oct. 8, 20042

The radio SETI paradigm

SETI radio beacon (acquisition signal) –but why?

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

A substantial fraction of sun-like stars out to several hundred light years have been

monitored for ETI with radio SETI.

Credit: Allen Telescope



Cosmic archaeology

… and Dyson Spheres

Nuclear waste disposal

Salting with unusual atomic lines –

Technetium-Drake and Shklovskii – 105 tons.

G. Lemarchand, SETIQuest, Volume 1, Number 1, p. 3. On the web at http://www.coseti.org/lemarch1.htm

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 star to change Hertzsprung-Russell curve-unlikelymay require too much material

Star lifting (D. Criswell)

http://www.coseti.org/sq_v1_n1.htm

http://www.coseti.org/sq_v1_n1.htm

Rigid Dyson sphere is unstable instead swarm of smaller pieces

Searches-problem fixing distance

Signature

infrared

stellar luminosity (distance problem)

pure Planck

no star for pure DS

Types of Dyson Spheres - …pure, partial, rings,

Dyson spheres

Dyson Sphere4 mm thick

Venus Sun

R=1.5*108 km

Infraredradiation

Based on www.daviddarling.info/encyclopedia/D/Dysonsp.html

Types

pure – star completely obscured

partial

Energy to assemble

800 solar years to take Jupiter apart

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

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

←Planetary nebula from IRAS dumbbell M22.

IRAS 06176-1036 “Red Rectangle” →

Earlier searchesJugaku 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

Picture from Infrared Processing and Analysis Center, Caltech/JPL. IPAC is NASA's Infrared Astrophysics Data Center.

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,

1 Jy for 100 μm

250 K point sources

angular resolution – O(1')

positional – 2 to 6" in-scan, 8 – 16" cross

Requirement for Dyson Sphere search all sky – useful 100 < T < 600 °K

2MASS much more sensitive, 500 M point sources IRAS 12 μm must be at least 10 Jy to register in the 2MASS 2.17 μm filter



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



Planck fitting (IRAS 06176-1036 “Red Rectangle”)

2

2

/)(

k km

kmnmkmnkmn

PaKFTLSQ

LSQ

0.0

0.4

0.8

1.2

1.62.0

2.4

2.8

3.2

3.6

4.0

100 200 300 400 500 600

T(°K)

LSQ

(T)*

1E6

T = 313 °K

Solid red is trial fit to three pointsDotted is final fit

Planck fit

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 20 40 60 80 100 (m)

F/K

, P*a

min

Flux/k

P*amin

2MASS

Planck

Planck inter

F is IRAS flux, K is Planck color correction,

P is Planck dist., sigma is weight, and a is fit para



Color color fitting

100

1000

0 5 f (12)/f (25), f (25)/f (60)

T

k

kbakll ffccTe )/(0

Left is 12/25, rt 25/60

Fit with arbitrary polynomial

Diamonds are extragalacticDots - no catalog entry, pure DSDyson Spheres along BB line

Follow Pottasch et al. AA 205, 248 (88), Fig. 1

Each pair gives a black body temperature line shows equal pairs, dots BB temp

0.1

1

0.4 0.6 0.8 1 3F

(12)

/F(

25)

F(25)/F(60)

500

400

300

200



Relation of color-color fits to Planck fits: no star 60/2525/12

60/2525/122/

TT

TTTdT

↓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



dT/T distribution from color color fitting

No obvious peaking at dT/T = 0 where pure Dyson Sphere should be370 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 = 0A 3 σ peak in one bin might require about 25 sources or one in 10,000 of the IRAS sources.

0

20

40

60

80

100

120

-0.50 -0.25 0.00 0.25 0.50

dT/T

f

↓blackbody line



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 sourcesThus 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

14

Summary

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

Artifacts like pyramids, Dyson Spheres and Kardashev civilizations are “natural” and don’t require purposeful signals

Dyson Sphere

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

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 20 40 60 80 100 (m)

F/K

, P*a

min

Can get good black body fits and do find candidates but there are surrogates like the planetary nebula “Red Rectangle”



Questions?



Documents

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