milky way galaxy upsc

[1] The Sun is currently 5–30 parsecs (16–98 ly) above, or north of, the central plane of the Galactic disk. [193] Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf. As is typical for spiral galaxies, the orbital speed of most stars in the Milky Way does not depend strongly on their distance from the center. [b] Maps of artificial night sky brightness show that more than one-third of Earth's population cannot see the Milky Way from their homes due to light pollution.[42]. [3] Astronomers first began to conjecture that the Milky Way is a barred spiral galaxy, rather than an ordinary spiral galaxy, in the 1960s. It has a close companion, the Small Magellanic Cloud. [97][1][2][98][99][100] In the inner few kiloparsecs (around 10,000 light-years radius) is a dense concentration of mostly old stars in a roughly spheroidal shape called the bulge. All the stars we see in the night sky are in our own Milky Way Galaxy. "The Milky Way, i.e. The motion of material around the center indicates that Sagittarius A* harbors a massive, compact object. Alternatively, a minority of astronomers propose that a modification of the law of gravity may explain the observed rotation curve. Don Lincoln writes about a new study that sheds light on the history of our Milky Way. Searching the photographic record, he found 11 more novae. Astronomers have mapped the most extensive atlas of our Milky Way galaxy yet, including the positions of nearly 2 billion stars. As viewed from Earth, the visible region of the Milky Way's galactic plane occupies an area of the sky that includes 30 constellations. A galaxy is a large group of stars, gas, and dust bound together by gravity. [137], It has been suggested that the Milky Way contains two different spiral patterns: an inner one, formed by the Sagittarius arm, that rotates fast and an outer one, formed by the Carina and Perseus arms, whose rotation velocity is slower and whose arms are tightly wound. [78] On November 4, 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs within the Milky Way. Black holes are born when a giant star runs out of energy. [68][127] There are thought to be four spiral arms that all start near the Milky Way's center. [176], Globular clusters are among the oldest objects in the Milky Way, which thus set a lower limit on the age of the Milky Way. [181][182][183], Several individual stars have been found in the Milky Way's halo with measured ages very close to the 13.80-billion-year age of the Universe. Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic, relative to the galactic plane. [180], In November 2018, astronomers reported the discovery of one of the oldest stars in the universe. Individual galaxies, including the Milky Way, have peculiar velocities relative to the average flow. Although special relativity states that there is no "preferred" inertial frame of reference in space with which to compare the Milky Way, the Milky Way does have a velocity with respect to cosmological frames of reference. From Sagittarius, the hazy band of white light appears to pass around to the galactic anticenter in Auriga. The Milky Way is a barred spiral galaxy with an estimated visible diameter of 150-200,000 light-years,[9][24][25] an increase from traditional estimates of 100,000 light-years. [216] However, Aristotle himself believed the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together"[217] and that the "ignition takes place in the upper part of the atmosphere, in the region of the world which is continuous with the heavenly motions. UPSC [51] According to a study published in 2014, the mass of the entire Milky Way is estimated to be 8.5×1011 M☉,[52] but this is only half the mass of the Andromeda Galaxy. This lack of recent major mergers is unusual among similar spiral galaxies; its neighbour the Andromeda Galaxy appears to have a more typical history shaped by more recent mergers with relatively large galaxies. The integrated absolute visual magnitude of the Milky Way is estimated to be around −20.9. The artist's concept also includes a new spiral arm, called the "Far-3 kiloparsec arm," discovered via a radio-telescope survey of gas in the Milky Way. One such frame of reference is the Hubble flow, the apparent motions of galaxy clusters due to the expansion of space. Rather, the concentration of stars decreases with distance from the center of the Milky Way. [86][87] The mass distribution within the Milky Way closely resembles the type Sbc in the Hubble classification, which represents spiral galaxies with relatively loosely wound arms. The largest of these is the Large Magellanic Cloud with a diameter of 14,000 light-years. [159] A reanalysis of the effects of the Sun's transit through the spiral structure based on CO data has failed to find a correlation. The band then continues the rest of the way around the sky, back to Sagittarius, dividing the sky into two roughly equal hemispheres. [203], Another reference frame is provided by the cosmic microwave background (CMB). Milky Way Galaxy nature sky sunset scenic milk evening forest dark nebula earth northern lights aurora beach cosmos sun mountain starry sky outdoors clouds abstract astronomy landscape Philippe Donn. Stars and gases at a wide range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The Milky Way consists of a bar-shaped core region surrounded by a warped disk of gas, dust and stars. Within a few billion years of the birth of the first stars, the mass of the Milky Way was large enough so that it was spinning relatively quickly. (2016), the Sun lies at an estimated distance of 27.14 ± 0.46 kly (8.32 ± 0.14 kpc)[2] from the Galactic Center. [187] Recent analysis of the chemical signatures of thousands of stars suggests that stellar formation might have dropped by an order of magnitude at the time of disk formation, 10 to 8 billion years ago, when interstellar gas was too hot to form new stars at the same rate as before. [179] Once a white dwarf is formed, it begins to undergo radiative cooling and the surface temperature steadily drops. Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy. It is estimated to contain 100–400 billion stars. [88][89][90] These conjectures were confirmed by the Spitzer Space Telescope observations in 2005[91] that showed the Milky Way's central bar to be larger than previously thought. Radio emission comes from a wide variety of sources. Hence, such objects would probably be ejected from the vicinity of the Milky Way. [30][31], The Milky Way contains between 100 and 400 billion stars[60][61] and at least that many planets. [142] However, a few globular clusters have been found farther, such as PAL 4 and AM 1 at more than 200,000 light-years from the Galactic Center. The Milky Way is the second-largest galaxy in the Local Group (after the Andromeda Galaxy), with its stellar disk approximately 170,000–200,000 light-years (52–61 kpc) in diameter and, on average, approximately 1,000 ly (0.3 kpc) thick. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Interstellar dust accounts for an additional 1% of the total mass of the gas. [168] Nonetheless, these stars and clusters now comprise the stellar halo of the Milky Way. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be visible. [133], The Near 3 kpc Arm (also called the Expanding 3 kpc Arm or simply the 3 kpc Arm) was discovered in the 1950s by astronomer van Woerden and collaborators through 21 centimeter radio measurements of HI (atomic hydrogen). In this scenario, suggested by numerical simulations of the dynamics of the different spiral arms, the outer pattern would form an outer pseudoring,[138] and the two patterns would be connected by the Cygnus arm. The gas is expelled, cools and forms stars on its way out of the galaxy, which end up with unusual or eccentric orbits that can run contrary to the regular swirl of the Milky Way. Wright and Kant also conjectured that some of the nebulae visible in the night sky might be separate "galaxies" themselves, similar to our own. The Milky Way is the galaxy that contains our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.The term Milky Way is a translation of the Latin via lactea, from the Greek γαλακτικός κύκλος (galaktikos kýklos, "milky circle"). This motion is observed by satellites such as the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) as a dipole contribution to the CMB, as photons in equilibrium in the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction. With this technique, the age of the globular cluster M4 was estimated as 12.7 ± 0.7 billion years. The low end of the estimate range is 5.8×1011 solar masses (M☉), somewhat less than that of the Andromeda Galaxy. [243], This article is about the galaxy. var urlmenu = document.getElementById('menu1'); For reasons that are not understood, beyond a radius of roughly 40,000 ly (13 kpc) from the center, the number of stars per cubic parsec drops much faster with radius. A. There may still be undetected dwarf galaxies that are dynamically bound to the Milky Way, which is supported by the detection of nine new satellites of the Milky Way in a relatively small patch of the night sky in 2015. Measurements of thin disk stars yield an estimate that the thin disk formed 8.8 ± 1.7 billion years ago. [139], Outside of the major spiral arms is the Monoceros Ring (or Outer Ring), a ring of gas and stars torn from other galaxies billions of years ago. This value is estimated using geometric-based methods or by measuring selected astronomical objects that serve as standard candles, with different techniques yielding various values within this approximate range. Because of this high inclination, depending on the time of night and year, the arch of the Milky Way may appear relatively low or relatively high in the sky. Pixabay. [194] There are also some dwarf galaxies that have already been absorbed by the Milky Way, such as the progenitor of Omega Centauri. 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