230907 - M31 "Andromeda" galaxy
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click image to enlarge
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ASTRO:
type=barred spiral galaxy const=Andromeda mag=3.4 dist=2.5 M ly size=220 k ly IMAGE: location=EB Driveway BrtlCls=4 exposure=CMOS OSC: 153x120s (5.1h) EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=Explore Scientific ED102 CF corrector=Starizona 0.65x "L" reducer, eff. FL=464mm, f/4.55, filter=Optolong L-Pro LPS; mount=Celestron AVX EQ; guiding=Orion 60x240mm, ZWO ASi224MC SOFTWARE: acquisition=Stellarium, APT, PHD2, processing=PixInsight, RCAstro, PhotoshopCC, APF-R, LrC |
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The Andromeda Galaxy, also known as Messier 31, or M31, and NGC 224, is a barred spiral galaxy located appx 2.5 million light-years from Earth. It is the nearest large galaxy to our home galaxy, the Milky Way. Andromeda's name comes from the area of Earth's sky in which it appears, the constellation of Andromeda, which in Greek mythology is named after the Ethiopian princess who was the wife of the mighty warrior, Perseus.
A galaxy is a gravitationally bound system of stars, interstellar gas, dust, and dark matter. It represents the largest independently visible type of object that astronomers typically observe in our night sky. In this image, the star field seen outside of Andromeda Galaxy is part of our home galaxy, the Milky Way. Because we are located far inside the bounds of our home galaxy, we are "looking through" a sea of stars that are between appx 5 light years (close) to 100,000 light years (far) away from us. But Andromeda lies much further away than that. At appx 2.5 M light years, the space between our Milky Way and Andromeda is a large expanse of outer space called the intergalactic medium that is largely void of visible objects like stars, nebulae and dust clouds.
Outer space, while invisible, is actually not completely empty. It is a near perfect vacuum containing a very low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, and cosmic rays, all of which are invisible to typical astronomers' telescopes. The plasma between galaxies is thought to account for about half of the ordinary matter in the universe, but it has a density of less than one hydrogen atom per cubic meter.
The mass of the Andromeda Galaxy is on the same order of magnitude as that of the Milky Way, containing an estimated 200 billion stars, and having a mass of appx 1 trillion solar masses. The mass of either galaxy is difficult to estimate with accuracy, but it has long been theorized that Andromeda is somewhat more massive than the Milky Way by a margin of about 25%.
Visually, Andromeda is a large object in the night sky. It spans appx 2° across, the same distance as appx four (4) full Moons in a straight line. Working thru the math, Andromeda's diameter is appx 220,000 ly, making it the largest member of the Local Group of galaxies in terms of dimensional size. It compares to appx 185,000 ly diameter for our home Milky Way. With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects, making it visible to the naked unaided eye from Earth on moonless nights, even when viewed from areas with moderate light pollution. It becomes more visible with the use of binoculars, and is very discernible with low-power, wide-field telescopes.
The Milky Way and Andromeda galaxies are bound to each other gravitationally; they are expected to collide in 4-5 billion years, merging to form a giant elliptical galaxy or a large lenticular galaxy.
A galaxy is a gravitationally bound system of stars, interstellar gas, dust, and dark matter. It represents the largest independently visible type of object that astronomers typically observe in our night sky. In this image, the star field seen outside of Andromeda Galaxy is part of our home galaxy, the Milky Way. Because we are located far inside the bounds of our home galaxy, we are "looking through" a sea of stars that are between appx 5 light years (close) to 100,000 light years (far) away from us. But Andromeda lies much further away than that. At appx 2.5 M light years, the space between our Milky Way and Andromeda is a large expanse of outer space called the intergalactic medium that is largely void of visible objects like stars, nebulae and dust clouds.
Outer space, while invisible, is actually not completely empty. It is a near perfect vacuum containing a very low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, and cosmic rays, all of which are invisible to typical astronomers' telescopes. The plasma between galaxies is thought to account for about half of the ordinary matter in the universe, but it has a density of less than one hydrogen atom per cubic meter.
The mass of the Andromeda Galaxy is on the same order of magnitude as that of the Milky Way, containing an estimated 200 billion stars, and having a mass of appx 1 trillion solar masses. The mass of either galaxy is difficult to estimate with accuracy, but it has long been theorized that Andromeda is somewhat more massive than the Milky Way by a margin of about 25%.
Visually, Andromeda is a large object in the night sky. It spans appx 2° across, the same distance as appx four (4) full Moons in a straight line. Working thru the math, Andromeda's diameter is appx 220,000 ly, making it the largest member of the Local Group of galaxies in terms of dimensional size. It compares to appx 185,000 ly diameter for our home Milky Way. With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects, making it visible to the naked unaided eye from Earth on moonless nights, even when viewed from areas with moderate light pollution. It becomes more visible with the use of binoculars, and is very discernible with low-power, wide-field telescopes.
The Milky Way and Andromeda galaxies are bound to each other gravitationally; they are expected to collide in 4-5 billion years, merging to form a giant elliptical galaxy or a large lenticular galaxy.