CONTAMINATION BY SUPERNOVAE IN GLOBULAR CLUSTERS

Credit: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF)

Only a small amount of the supernovae products remains trapped within globular clusters and this "catch" only occurs in the most massive cases (mass cluster ≥ 10^6 solar masses).
In smaller clusters instead there is no contamination by supernovae (supernova explosions produce heavier elements such as iron, gold, etc.). A group of astrophysicists has shown that the shock wave and the metals produced by supernovae disperse outside the cluster. This inhibits the gas contamination used by the first stellar generation (a new stellar generation can arise from the "recycled gas" expelled by supernovae). Only the material ejected by the supernova at the center of a massive cluster remain trapped (the ejected material moves in a high-density medium and remains locked) and it is available to a stellar population of second generation.

To know more
http://arxiv.org/abs/1511.02918
http://iopscience.iop.org/article/10.1088/2041-8205/814/1/L8/pdf

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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 ).

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).

The neutron-star low-mass X-ray binary GX 9+1

Figure - An artist's impression of an accreting Low Mass X-ray Binary. The donor star fills its Roche lobe and its material overflows the inner Lagrangian points and accretes on the relativistic star. Due to the large angular momentum of the infalling material an accretion disk is formed around the compact object. Credit: ESA, NASA, and Felix Mirabel (French Atomic Energy Commission and Institute for Astronomy and Space Physics/Conicet of Argentina) A low-mass X-ray binary (LMXB) contains a neutron star which is accreting material via Roche lobe overflow from a companion star. Due to the high angular momentum of the accretion flow an accretion disc is formed around the compact object. In a recent paper ( van den Berg & Homan 2016 ) the authors have determined an improved position for the luminous persistent neutron-star low-mass X-ray binary and atoll source GX 9+1 from archival Chandra X-ray Observatory data and they have identified a new near-infrared (NIR) counterpar...

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