A UNIVERSE WITHOUT A CENTER?

Image Credit: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb.

According to the standard theories of cosmology, there is no center of the universe.
In a conventional explosion, material expand out from a central point and the instinct suggests that with the Big Bang happened something similar.
But the Big Bang was not an explosion like that at all: it was an explosion of space, not an explosion in space. The Big Bang happened everywhere in the Universe.

Current theories which are based for example on the observation of uniformity in all directions of the cosmic background radiation suggest this hypothesys.
The universe can be compared to the two-dimensional surface of an expanding balloon (this is the classic example used to explain its expansion). The whole universe would be limited to surface alone and would not include the space inside or outside of the surface of the balloon. Therefore there is no center, because on the surface of the balloon is not possible to identify a center.
In this analogy it is important to remember that, unlike the ballon, the universe is three-dimensional and not two-dimensional, that the size can be finite or infinite and that galaxies do not expand although are moving away because they are gravitationally bound.

► Read more>>
http://phys.org/news/2015-02-big.html

► Image Credit:
Eugenio Bianchi, Carlo Rovelli & Rocky Kolb.

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ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

RADIATIVE CLEARING OF PROTOPLANETARY DISCS

Image: protoplanetary disc surrounding the young star HL Tauri, a very young T Tauri star in the constellation Taurus, approximately 450 light-years (140 pc) from Earth in the Taurus Molecular Cloud. These new ALMA observations reveal substructures within the disc that have never been seen before and even show the possible positions of planets forming in the dark patches within the system. Credit: ALMA (ESO/NAOJ/NRAO) T Tauri stars are pre-main-sequence stars in the process of contracting to the main sequence. Their central temperatures are too low for hydrogen fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving towards the main sequence, which they reach after about 100 million years. Roughly half of T Tauri stars have circumstellar disks, which in this case are called protoplanetary discs because they are probably the progenitors of planetary systems like the Solar System.

CONSTRAINTS ON THE LOCATION OF A POSSIBLE 9TH PLANET

Image: The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Such an orbital alignment can only be maintained by some outside force, Batygin and Brown say. Their paper argues that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech The astronomers have noticed some of the dwarf planets and other small, icy objects tend to follow orbits that cluster together. To explain the unusual distribution of these Kuiper Belt objects, several authors have advocated the existence of a superEarth planet in the outer solar system ( planet Nine or planet X ).

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