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TOPIC: Milky Way


L

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RE: Milky Way
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Specialists created a principally new computer model of the Milky Way
The most overriding issue for all astronomers is the substance of the Universe. It is known that stars and planets comprise only the smallest part of the substance, while 85% is the hidden part called "dark matter". Scientists have not yet decoded its constitution.
Specialists have created a computer model of the Milky Way due to which they will be able to decode the substance.

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The Milky Way galaxy suspended in a glass cube

A laser was used to etch around 80,000 of the stars in the Milky Way, using three-dimensional data from the Japans National Astronomical Observatory.
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Smith's Cloud
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Massive Gas Cloud on Collision Course with the Milky Way
Don't panic, but there's a giant cloud of hydrogen gas on a collision course with the Milky Way. When it hits, 40 million years from now, it should generate vast regions of star formation.
In fact, we don't even need to wait; the leading edge of this gas cloud is already starting to interact with our galaxy. The fireworks are about to begin.
The cloud is called Smith's Cloud, after the astronomer who discovered it in 1963. It's 11,000 light-years long and 2,500 light-years wide, and contains enough hydrogen to make a million stars with the mass of the Sun.


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New, very precise measurements have shown that the rotation of the Milky Way is simpler than previously thought. A remarkable result from the most successful ESO instrument HARPS, shows that a much debated, apparent 'fall' of neighbourhood Cepheid stars towards our Sun stems from an intrinsic property of the Cepheids themselves.

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New simulations have shown that in galaxies similar to the Milky Way stars such as the sun can migrate great distances.
A long-standing scientific belief holds that stars tend to hang out in the same general part of a galaxy where they originally formed.

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Title: A Disk of Young Stars at the Galactic Centre as Determined by Individual Stellar Orbits
Authors: J. R. Lu, A. M. Ghez, S. D. Hornstein, M. R. Morris, E. E. Becklin, K. Matthews

We present new proper motions from the 10 m Keck telescopes for a puzzling population of massive, young stars located within 3.5" (0.14 pc) of the supermassive black hole at the Galactic Centre. Our proper motion measurements have uncertainties of only 0.07 mas/yr (3 km/s), which is ~7 times better than previous proper motion measurements for these stars, and enables us to measure accelerations as low as 0.2 mas/yr^2 (7 km/s/yr). Using these measurements, line-of-sight velocities from the literature, and 3D velocities for additional young stars in the central parsec, we constrain the true orbit of each individual star and directly test the hypothesis that the massive stars reside in two stellar disks as has been previously proposed. Analysis of the stellar orbits reveals only one of the previously proposed disks of young stars using a method that is capable of detecting disks containing at least 7 stars. The detected disk contains 50% of the young stars, is inclined by ~115 deg from the plane of the sky, and is oriented at a position angle of ~100 deg East of North. Additionally, the on-disk and off-disk populations have similar K-band luminosity functions and radial distributions that decrease at larger projected radii as \propto r^-2. The disk has an out-of-the-disk velocity dispersion of 28 ± 6 km/s, which corresponds to a half-opening angle of 7 ± 2 deg, and several candidate disk members have eccentricities greater than 0.2. Our findings suggest that the young stars may have formed in situ but in a more complex geometry than a simple, thin circular disk.

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Researchers say they have figured out how a mysterious clutch of massive stars could have come into existence a few trillion miles from the supermassive black hole at the centre of the Milky Way.
This group of starsabout 100 of them in an elongated diskhas posed a challenge to theories of star formation, which predict that stars emerge when clouds of hydrogen molecules coalesce under their collective gravitational attraction.

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Milky Way streams
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Eleven new streams of stars may have been spotted in the Milky Way in a survey of a quarter million stars. The streams may provide new forensic evidence of the Milky Way's violence, as they were likely ripped from dwarf galaxies that were gobbled up by our galaxy.
The eleven possible streams turned up during a study of the velocities of stars in the Milky Way's inner halo a bubble-like region that surrounds the galactic centre. Only two streams were previously known to exist in the area.

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A new map of the halo of stars that surrounds our Milky Way Galaxy has revealed a complicated structure of crisscrossing stellar streams, many of which have never been detected before.
While the bulk of our galaxy's stars are concentrated in a fairly flat disk and a bulbous central region, the halo is the first thing an intergalactic traveler would encounter upon approaching our home galaxy. The halo begins at the edge of the disk around 65,000 light years from the galactic centre and may extend out as far as 300,000 light years from the centre of the galaxy. The halo comprises star clusters, clouds of gas, dark matter, and a few lone stars. Some of these pieces were grabbed up by the Milky Way from dwarf galaxies as they passed by.

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Last year, astronomers got a shock when it emerged that our galaxy's brightest companion, the Large Magellanic Cloud (LMC), appeared to be speeding through space so fast that we wouldn't be able to hold onto it. Now two new measurements suggest the Milky Way will manage to keep its companion after all.
The first shows our galaxy to be spinning faster than we had thought. A star near the sun on a circular orbit round the galactic centre now appears to travel at 251 kilometres per second, compared with a previous figure of 220 km/s. And the centre of the galaxy now appears to be 27,400 light years from Earth, slightly further than the older figure of 26,100 light years.
Taken together, these findings imply that the Milky Way has about 50 per cent more mass than previously estimated.

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