Dyson sphere look alikes updated December 7, 2005 D. Carrigan carrigan@fnal.gov (subject line must be sensible)

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Infrared/Dyson

Introduction

A number of astronomical objects have infrared signatures somewhat like a Dyson Sphere. These include stars with thick dust shells, regions of dust, very young stars that form in regions of dust, Miras stars, planetary nebula, AGB, and post AGB stars. A Dyson sphere search has to rule out these more conventional and plausible classifications to identify interesting Dyson sphere candidates. The Calgary Group has complied a comprehensive atlas of all of the available IRAS Low Resolution Spectra. This is discussed in "Classification and Identification of IRAS Sources with Low-Resolution Spectra", Kwok, Volk, and Bidelman, ApJS, 112, 557 (1997). They break LRS sources into a number of categories including the ones below (U, F, C, and H) that might identify Dyson Sphere candidates. While comprehensive, this is not necessarily the last word on IR spectra and identification since more data is now available from facilities such as the Spitzer Space Telescope and 2MASS. The first table gives some of the characteristics of the classifications that might contain Dyson Spheres. The second table list some interesting objects with infrared features that would not pass as Dyson Spheres.

Calgary Classification

Description

Astronomical objects

U

"Unusual spectra showing a flat continuum"

Type of object generally unkown according to Calgary Atlas of LRS sources

F

Featureless

O or C rich stars with small amounts of dust

C

Carbon stars

Late type stars such as evolved cool giants with circumstellar shells or clouds of carbon dust material. Typically these have small optical depths so a percent or so of the emission is in the infrared.

H

Red continuum with absorption

H II regions, planetary nebula, reflection nebula

IRAS 06176-1036 "Red Rectangle">>>

Miras	Named after the famous long period variable Mira. Miras are old stars that have evolved into so-called asymptotic giant branch stars (AGBs). This is not the signature of a pure Dyson sphere. More on Miras...
OH/IR Maser	The gas cloud from a Miras star can give rise to hydoxyl ions (OH) and SiO (silicon monoxide) which forms a maser. This is not the signature of a pure Dyson sphere. More on OH/IR masers...
Protostars and young stars	Characteristically star formation occurs in regions where there is lots of dust such as Orion. A typical spectral distribution would be the combination of many Planck spectra. This is not the signature of a pure Dyson sphere.
Brown dwarfs	Brown dwarfs are failed stars with masses less than 0.075 the mass of the sun. This is not the signature of a pure Dyson sphere. More on Brown Dwarfs... VV MORE VV
Galaxies	Characteristically galaxies detected by the IRAS satellite are relatively nearby and are not point sources. Even a nearby Dyson sphere should be a point source in any infrared telescope. This is not the signature of a pure Dyson sphere.