# Eikonal Blog

## 2011.05.09

### Astronomy & Astrophysics

Filed under: astronomy, cosmology, physics — sandokan65 @ 10:16

## Articles

• “Kepler May Uncover Numerous Ring Worlds” 9SlashDot; 2011.05.08) – http://science.slashdot.org/story/11/05/08/2230208/Kepler-May-Uncover-Numerous-Ring-Worlds
“According to a new publication, NASA’s Kepler exoplanet-hunting space telescope may soon start discovering Saturn-like ringed alien worlds. So far, none have been positively identified, as Kepler has only detected exoplanets orbiting close to their parent stars; if these exoplanets have rings, they are most likely to have rings facing edge-on to their orbits, making them nearly impossible to detect. As more distant-orbiting exoplanets are detected, there’s more likelihood ringed worlds will be tilted, allowing Kepler to see them.”

Related here: Astronomic tables and calculators – https://eikonal.wordpress.com/2010/01/28/astronomic-tables-and-calculators/ | Solar planetary system – https://eikonal.wordpress.com/2011/02/17/solar-planetary-system/ | Inside black holes – https://eikonal.wordpress.com/2011/04/12/inside-black-holes/ | Physics Sites – https://eikonal.wordpress.com/2010/02/12/physics-sites/

## 2011.04.12

Filed under: astronomy, evolution, life, mind & brain, physics — Tags: , — sandokan65 @ 10:03

## Be quiet you stupid young species! (or else be gone)

• “Is ET avoiding us out of a fear of human galactic conquest?” (io9; 2011.04.10) – http://io9.com/#!5790567/is-et-avoiding-us-out-of-a-fear-of-human-galactic-conquest
• “Is ET Scared of Human Conquest?” (13point7 blog) – http://thirteenpointseven.wordpress.com/2011/04/11/is-et-scared-of-human-conquest/
• “Interstellar Predation Could Explain Fermi Paradox” (The Physics arXiv blog; 2011.04.08) – http://www.technologyreview.com/blog/arxiv/26622/
In a casual chat over lunch back in 1950, the Italian-American physicist Enrico Fermi posed a now famous question. If intelligent life has evolved many times in our galaxy and beyond, why do we see no sign of it?

Kent puts it like this: “If cosmic habitats are widely enough separated that they are very hard to ﬁnd, by far the best strategy for a typical species to avoid defeat in such competitions may be to avoid entering them, by being inconspicuous enough that no potential adversary identiﬁes its habitat as valuable.”

That raises important questions about whether humanity is wise to advertise its existence. Various attempts to send messages to the stars have already been made and many scientists have pointed out that this could be a serious mistake, even a suicidal one.

• “Too Damned Quiet?” by Adrian Kent (arXiv.org > physics > arXiv:1104.0624; 2011.04.04) – http://arxiv.org/abs/1104.0624
Abstract: It is often suggested that extraterrestial life sufficiently advanced to be capable of interstellar travel or communication must be rare, since otherwise we would have seen evidence of it by now. This in turn is sometimes taken as indirect evidence for the improbability of life evolving at all in our universe. A couple of other possibilities seem worth considering. One is that life capable of evidencing itself on interstellar scales has evolved in many places but that evolutionary selection, acting on a cosmic scale, tends to extinguish species which conspicuously advertise themselves and their habitats. The other is that — whatever the true situation — intelligent species might reasonably worry about the possible dangers of self-advertisement and hence incline towards discretion. These possibilities are discussed here, and some counter-arguments and complicating factors are also considered.

### Inside black holes

Filed under: astronomy, General relativity, physics — Tags: , — sandokan65 @ 09:47
• “Planets Could Orbit Singularities Inside Black Holes” (The Physics arXiv Blog; 2011.04.11) – http://www.technologyreview.com/blog/arxiv/26626/
The discovery of stable orbits inside certain kinds of black hole implies that planets and perhaps even life could survive inside these weird objects, says one cosmologist
• “Is there life inside black holes?” by Vyacheslav I. Dokuchaev (arXiv.org > gr-qc > arXiv:1103.6140; 2011.04.09) – http://arxiv.org/abs/1103.6140
Abstract: Inside the rotating or charged black holes there are bound periodic planetary orbits, which not coming out nor terminated at the central singularity. The stable periodic orbits inside black holes exist even for photons. We call these bound orbits by the orbits of the third kind, following to Chandrasekhar classification for particle orbits in the black hole gravitational field. It is shown that an existence domain for the third kind orbits is a rather spacious, and so there is a place for life inside the supermassive black holes in the galactic nuclei. The advanced civilizations of the third kind (according to Kardashev classification) may inhabit the interiors of supermassive black holes, being invisible from the outside and basking as in the light of the central singularity and the orbital photons.

Related here: Astronomy & Astrophysics – https://eikonal.wordpress.com/2011/05/09/astronomy-astrophysics/ | Astronomic tables and calculators – https://eikonal.wordpress.com/2010/01/28/astronomic-tables-and-calculators/ | Solar planetary system – https://eikonal.wordpress.com/2011/02/17/solar-planetary-system/ | Physics Sites – https://eikonal.wordpress.com/2010/02/12/physics-sites/

## Dwarf planets

Definitions (from “Pluto’s Dwarf Planet Family Could Get Bigger” by Ian O’Neill (Discovery News; 2010.04.09) – http://news.discovery.com/space/plutos-dwarf-planet-family-is-about-to-get-bigger.html)

• The 2006 IAU definition of a dwarf planet states that such a body should be massive enough to achieve hydrostatic equilibrium, it must orbit the sun, but it cannot “clear its own orbit.”
• The ‘potato-limit’: “the rule that they must be of certain brightness, dwarf planets have a minimum radius of 420 km (260 miles).”

All except Ceres are trans-Neptunians residing in the Kuipert belt.

Name Location Discovery details Orbit radius Orbital period Size (radius) Mass Length of the day Misc
Eris (= 2003 UB_313; initially called “Xena”) Kuipert belt
Pluto Kuipert belt 1930.02.18 by Clyde Tombaugh it has very excentric orbit, with $aphelion =$ $7.375 x10^9 km =$ $49.305 AU$ and $perihelion =$ $4.436 x10^9 km =$ $29.658 AU$ $90,613.305 days_{Earth} =$ $248.09 years_{Earth} =$ $14,164.4 days_{Pluto}$ $1,153 \pm 10 km =$ $0.18 R_{Earth}$ $(1.305 \pm 0.007)\times 1022 kg =$ $0.002 M_{Earth} =$ $0.178 M_{Moon}$ $6.387 230 day_{Earth} =$ $6 \ d \ 9 \ h \ 17 \ m \ 36 \ s$ Has four satellites:

• Hydra: discovered by Hubble telescope in 2005. 30 to 115km diameter.
• Charon: discovered in 1978 by the US Naval Observatory. 1,200km diameter.
• Nix: discovered by Hubble telescope in 2005. 30 to 115km diameter.
• P4 (yet unnamed): diameter 13 to 34 km [of 8 to 21 miles]
Makemake Kuipert belt
Haumea Kuipert belt
Quaoar (= 2002 LM60; = 50000 Quaoar) Kuipert belt announced 2002.02.07 by Michael Brown and Chadwick Trujillo of Caltech $~ 6.5 x10^9 km = 4 x10^9 miles$ $~ 288 years_{Earth}$ $~ 650 km = 400 miles$ likely composition: made mostly of low-density ices mixed with rock
Sedna (= 90377 Sedna) Kuipert belt discovered in 2003
Ceres asteroid belt

Sources:

## Oort Cloud

a sphere one light year in radius stretching a quarter of the distance to Alpha Centauri

## Potential planet: Tyche

Related here: Astronomy & Astrophysics – https://eikonal.wordpress.com/2011/05/09/astronomy-astrophysics/ | Astronomic tables and calculators – https://eikonal.wordpress.com/2010/01/28/astronomic-tables-and-calculators/ | Inside black holes – https://eikonal.wordpress.com/2011/04/12/inside-black-holes/ | Physics Sites – https://eikonal.wordpress.com/2010/02/12/physics-sites/