|Mythology – Andromeda|
Galaxy’s near Planet Earth…!
The Andromeda Galaxy (/ænˈdrɒmɨdə/) is a spiral galaxy approximately 2.5 million light-years (2.4×1019 km) from Earth in the Andromeda constellation. Also known as Messier 31, M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our Milky Way galaxy, but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, the Andromeda Galaxy may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and could be the most massive in the grouping. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars: at least twice the number of stars in the Milky Way galaxy, which is estimated to be 200–400 billion.
This list contains all known stars and brown dwarfs at a distance of up to 5 parsecs (16.3 light-years) from the Solar System, ordered by increasing distance. In addition to the Solar System, there are another 51 stellar systems currently known lying within this distance. These systems contain a total of 61 hydrogen-fusing stars and nine brown dwarfs. Despite the relative proximity of these objects to the Earth, only nine of them have an apparent magnitude less than 6.5, which means only about 13% of these objects can be observed with the naked eye. Besides the Sun, only three are first-magnitude stars: Alpha Centauri, Sirius, and Procyon. All of these objects are located in the Local Bubble, a region within the Orion–Cygnus Arm of the Milky Way Galaxy.
ALPHA – CENTAURI
Alpha Centauri (α Centauri, α Cen; also known as Rigel Kent /ˈraɪdʒəl ˈkɛnt/—see Names) is the brightest star in the southern constellation of Centaurus and is currently inside the G-cloud. Although it appears to the unaided eye as a single object, Alpha Centauri is actually a binary star system (designated Alpha Centauri AB or α Cen AB) whose combined visual magnitude of −0.27 makes it the third-brightest star in the night sky after the −1.46 magnitude Sirius and the −0.72 magnitude Canopus.
Its individual component stars are named Alpha Centauri A (α Cen A), with 110% of the mass and 151.9% the luminosity of the Sun, and Alpha Centauri B (α Cen B), at 90.7% of the Sun’s mass and 44.5% of its luminosity. During the pair’s 79.91-year orbit about a common center, the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun. They are 1.34 parsecs or 4.37 light years from the Sun.
A third star, known as Proxima Centauri, Proxima or Alpha Centauri C (α Cen C), is probably gravitationally associated with Alpha Centauri AB. Proxima is at the slightly smaller distance of 1.29 parsecs or 4.21 light years from the Sun, making it the closest star to the Sun, even though it is not visible to the naked eye. The separation of Proxima from Alpha Centauri AB is about 0.06 parsecs, 0.2 light years or 13,000 astronomical units (AU); equivalent to 400 times the size of Neptune’s orbit.
The system may also contain at least one planet, the Earth-sized Alpha Centauri Bb, which if confirmed will be the closest known exoplanet to Earth. The possible planet has a mass at least 113% of Earth’s and orbits Alpha Centauri B with a period of 3.236 days. Orbiting at a distance of 6 million kilometers from the star, 4% of the distance of the Earth to the Sun and ten times closer than the orbit of Mercury, the planet has an estimated surface temperature of 1500 K (roughly 1200 °C), too hot to be habitable.
BARNARD’S [Bernard’s] STAR
Barnard’s Star (pron.: /ˈbɑrnərd/), also known occasionally as Barnard’s “Runaway” Star, is a very low-mass red dwarf star about six light-years away from Earth in the constellation of Ophiuchus, the Snake-holder. Barnard’s Star is the fourth-closest known individual star to the Sun, after the three components of the Alpha Centauri system. Despite its proximity, Barnard’s Star, at a dim apparent magnitude of about nine, is not visible with the unaided eye; however, it is much brighter in the infrared than it is in visible light. The star is named for American astronomer E.E. Barnard. He was not the first to observe the star, but in 1916 he measured its proper motion as 10.3 arcseconds per year, which remains the largest-known proper motion of any star relative to the Sun.
Barnard’s Star has been the subject of much study, and it has probably received more attention from astronomers than any other class M dwarf star due to its proximity and favorable location for observation near the celestial equator. Historically, research on Barnard’s Star has focused on measuring its stellar characteristics, its astrometry, and also refining the limits of possible extrasolar planets. Although Barnard’s Star is an ancient star, some observations suggest that it still experiences star flare events.
Barnard’s Star has also been the subject of some controversy. For a decade, from the early 1960s to the early 1970s, Peter van de Kamp claimed that there was a gas giant planet (or planets) in orbit around it. While the presence of small terrestrial planets around the star remains a possibility, Van de Kamp’s specific claims of large gas giant planets were refuted in the mid-1970s.
Barnard’s Star is also notable as the target for Project Daedalus, a study on the possibility of fast, unmanned travel to nearby star systems.
Refining planetary boundaries
While not completely ruling out the possibility of planets, null results for planetary companions continued throughout the 1980s and 1990s, the latest based on interferometric work with the Hubble Space Telescope in 1999. By refining the values of a star’s motion, the mass and orbital boundaries for possible planets are tightened: in this way astronomers are often able to describe what types of planets cannot orbit a given star.
M dwarfs such as Barnard’s Star are more easily studied than larger stars in this regard because their lower masses render perturbations more obvious. Gatewood was thus able to show in 1995 that planets with 10 times the mass of Jupiter (the lower limit for brown dwarfs) were impossible around Barnard’s Star, in a paper which helped refine the negative certainty regarding planetary objects in general. In 1999, work with the Hubble Space Telescope further excluded planetary companions of 0.8 times the mass of Jupiter with an orbital period of less than 1,000 days (Jupiter’s orbital period is 4,332 days), while Kuerster determined in 2003 that within the habitable zone around Barnard’s Star, planets are not possible with an “M sin i” value greater than 7.5 times the mass of the Earth, or with a mass greater than 3.1 times the mass of Neptune (much lower than van de Kamp’s smallest suggested value).
Even though this research has greatly restricted the possible properties of planets around Barnard’s Star, it has not ruled them out completely; terrestrial planets would be difficult to detect. NASA’s Space Interferometry Mission, which was to begin searching for extrasolar Earth-like planets, was reported to have chosen Barnard’s Star as an early search target. However, this mission was shut down in 2010. ESA’s similar Darwin interferometry mission had the same goal, but was stripped of funding in 2007.
…Our most easy visible Galaxies, like Andromeda are impressive, and might be twice the size of the Milky Way…!
…How far are we from any possible known habitable planet like Earth, in the Milky Way…?
…Seemingly, no where else to go…!
AT THE CURRENT RATE OF USAGE OF WORLD RESOURCES, it will imply when these resources get to a noticeable depletion and population suffering and hunger deaths, that World Countries could start a more forceful battle for resources and life…!