202 research outputs found
Dyson sphere
Some time ago, astronomers discovered a star with unusual brightness changes. The star is known as KIC 8462852, and is located in the constellation Cygnus. As a rule, slight and periodic changes in the brightness of a star is a normal process. Extinction of less than 1% says that the star passes the planet, which absorbs some of the light
A Dyson Sphere around a black hole
The search for extraterrestrial intelligence (SETI) has been conducted for
nearly 60 years. A Dyson Sphere, a spherical structure that surrounds a star
and transports its radiative energy outward as an energy source for an advanced
civilisation, is one of the main targets of SETI. In this study, we discuss
whether building a Dyson Sphere around a black hole is effective. We consider
six energy sources: (i) the cosmic microwave background, (ii) the Hawking
radiation, (iii) an accretion disk, (iv) Bondi accretion, (v) a corona, and
(vi) relativistic jets. To develop future civilisations (for example, a Type II
civilisation), () is expected to
be needed. Among (iii) to (vi), the largest luminosity can be collected from an
accretion disk, reaching , enough to maintain a Type
II civilisation. Moreover, if a Dyson Sphere collects not only the
electromagnetic radiation but also other types of energy (e.g., kinetic energy)
from the jets, the total collected energy would be approximately 5 times
larger. Considering the emission from a Dyson Sphere, our results show that the
Dyson Sphere around a stellar-mass black hole in the Milky Way (
away from us) is detectable in the ultraviolet,
optical, near-infrared(), and mid-infrared() wavelengths via the waste heat
radiation using current telescopes such as Galaxy Evolution Explorer
Ultraviolet Sky Surveys. Performing model fitting to observed spectral energy
distributions and measuring the variability of radial velocity may help us to
identify these possible artificial structures.Comment: This paper has been accepted for publication in MNRA
IRAS-based whole-sky upper limit on Dyson Spheres
A Dyson Sphere is a hypothetical construct of a star purposely cloaked by a
thick swarm of broken-up planetary material to better utilize all of the
stellar energy. A clean Dyson Sphere identification would give a significant
signature for intelligence at work. A search for Dyson Spheres has been carried
out using the 250,000 source database of the IRAS infrared satellite which
covered 96% of the sky. The search has used the Calgary database for the IRAS
Low Resolution Spectrometer (LRS) to look for fits to blackbody spectra.
Searches have been conducted for both pure (fully cloaked) and partial Dyson
Spheres in the blackbody temperature region 100 < T < 600 K. When other stellar
signatures that resemble a Dyson Sphere are used to eliminate sources that
mimic Dyson Spheres very few candidates remain and even these are ambiguous.
Upper limits are presented for both pure and partial Dyson Spheres. The
sensitivity of the LRS was enough to find Dyson Spheres with the luminosity of
the sun out to 300 pc, a reach that encompasses a million solar- type stars.Comment: 32 pages, 8 figure
Galileon Hairs of Dyson Spheres, Vainshtein's Coiffure and Hirsute Bubbles
We study the fields of spherically symmetric thin shell sources, a.k.a. Dyson
spheres, in a {\it fully nonlinear covariant} theory of gravity with the
simplest galileon field. We integrate exactly all the field equations once,
reducing them to first order nonlinear equations. For the simplest galileon,
static solutions come on {\it six} distinct branches. On one, a Dyson sphere
surrounds itself with a galileon hair, which far away looks like a hair of any
Brans-Dicke field. The hair changes below the Vainshtein scale, where the extra
galileon terms dominate the minimal gradients of the field. Their hair looks
more like a fuzz, because the galileon terms are suppressed by the derivative
of the volume determinant. It shuts off the `hair bunching' over the `angular'
2-sphere. Hence the fuzz remains dilute even close to the source. This is
really why the Vainshtein's suppression of the modifications of gravity works
close to the source. On the other five branches, the static solutions are all
{\it singular} far from the source, and shuttered off from asymptotic infinity.
One of them, however, is really the self-accelerating branch, and the
singularity is removed by turning on time dependence. We give examples of
regulated solutions, where the Dyson sphere explodes outward, and its
self-accelerating side is nonsingular. These constructions may open channels
for nonperturbative transitions between branches, which need to be addressed
further to determine phenomenological viability of multi-branch gravities.Comment: 29+1 pages, LaTeX, 2 .pdf figure
A1_2 Niven Rings
This article outlines the basic principles of a Niven Ring and with regards to harnessing a greater proportion of the Sun’s energy and as a stepping stone to a Dyson sphere
Starry Messages: Searching for Signatures of Interstellar Archaeology
Searching for signatures of cosmic-scale archaeological artifacts such as
Dyson spheres or Kardashev civilizations is an interesting alternative to
conventional SETI. Uncovering such an artifact does not require the intentional
transmission of a signal on the part of the original civilization. This type of
search is called interstellar archaeology or sometimes cosmic archaeology. The
detection of intelligence elsewhere in the Universe with interstellar
archaeology or SETI would have broad implications for science. For example, the
constraints of the anthropic principle would have to be loosened if a different
type of intelligence was discovered elsewhere. A variety of interstellar
archaeology signatures are discussed including non-natural planetary
atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson
spheres, as well as signatures of stellar and galactic-scale engineering. The
concept of a Fermi bubble due to interstellar migration is introduced in the
discussion of galactic signatures. These potential interstellar archaeological
signatures are classified using the Kardashev scale. A modified Drake equation
is used to evaluate the relative challenges of finding various sources. With
few exceptions interstellar archaeological signatures are clouded and beyond
current technological capabilities. However SETI for so-called cultural
transmissions and planetary atmosphere signatures are within reach.Comment: 29 pages including 4 figures and 1 tabl
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