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What do two dozen or so galaxies nearest to the Milky Way Galaxy form?
LooneyTunerIan
Two dozen or so galaxies nearest to the Milky Way Galaxy form Local Group.
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∙ 9y ago
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Our galaxy is one of a dozen galaxies that comprises what is known as the?
Our galaxy is one of the billions of other galaxy known as the spiral galaxy. Our galaxy is one of a dozen galaxies that comprises what is known as the local group.
What does the Local Group revolve around?
a cluster of about 40 galaxies to which the milky way galaxy belongs Five popular Local Group galaxies: 1. Milky Way 2. Andromeda 3. Triangulum 4. Large Magellanic Cloud 5. Small Magellanic Cloud
How many black holes are there in the milky way?
The milky way contains about a dozen black holes in the milky way.
What type of galaxy is the dimmest?
There are galaxies that orbit our galaxy that are believed to be filled with a lot of dark matter. Segue 1 is one of about two dozen dwarf galaxies around ours that have light outputs equal to only a few hundred times that of our sun. There are probably untold numbers of other such galaxies around the more visible galaxies. This is a possible explanation for the discrepancy in the predicted mass of the universe and the observed mass. Some theories postulate that 90% of the mass of the universe is composed of this unobservable "dark matter". The existence of these dim dwarf galaxies help explain the discrepancy.
How many ounces are in one dozen?
Any number you like. There will be zero ounces in a dozen ideas (ideas are massless), a tiny number of ounces in a dozen electrons and a huge number of ounces in a dozen galaxies.
How do you know how many stars and galaxies in the universe?
We guess. Really. There's no way to actually COUNT the stars in the Milky Way; the small ones are too small and dim to see if they are more than a few dozen light years away. So we make estimates, which are little better than guesses.
Why have no pictures been taken outside of the milky way galaxy?
We are inside the Milky Way galaxy, and so it is difficult to tell exactly what it looks like from the outside - because we aren't "outside."Think of it like this: If you are inside your house and never went outside, you could still look out the windows and see other houses. But you wouldn't be able to SEE your house. You could figure it out, by drawing a diagram - but it isn't the same thing as seeing it from the outside.From Earth, we see thousands upon thousands of stars. With big telescopes, we can also see other things between the stars, and some of those things are other galaxies.---Some galaxies are hard to see because dense groupings of stars and nebulae in the Milky Way are in the way. But given that, we can see a dozen or so "satellite" galaxies of the Milky Way, and the next closest galaxies are those in the Andromeda group, some 2 million light-years away. This means that the light we see left Andromeda more than two million years ago. We are seeing them as they were that long ago. However, galaxies persist for billions of years, so they are likely very little changed from what they looked like then.
When was the spiral galaxy discovered?
It wasn't until telescopes that people realized that the band of light reaching across the sky, called the Milky Way since ancient times, was actually made of an immense number of stars. Astronomers still did not really understand what they were seeing until the 20th century, however.Until the 1920s, astronomers thought that what we now know to be our Milky Way Galaxy to be the entire universe, and that our whole universe was a few thousand light years across. Other "spiral nebulae" had been observed, but they were thought to be new star systems forming nearby. After Hubble (the astronomer, not the telescope named for him) observed Cepheid variable stars in the Great Nebula in Andromeda, he realized that the Andromeda "Nebula" was immensley distant, and ennormous in size, and, by extension, the other "spiral nebulae" were also huge and incomprehensibly distant. He called them "island universes", and realized that we were also in one, and that the 'Milky Way' band of stars across the sky was our galaxy's disk, seen from inside. So, even though people have been calling the band of light across the sky the Milky Way for thousands of years, it wasn't until the 1920's that we understood what it was--our galaxy!We can see only a small part of our galaxy in visible light. Since the 1960s, radio astronomers have mapped out the structure of the entire galaxy, and shown it to be a large spiral galaxy of about 100 billion stars; we are in one of the spiral arms about 8 kiloparsecs (25,000 light years) from the center of our galaxy, more or less halfway from the center to the edge.I think Gallileo came across the milky way in the 1600's. The cloudy band we now call the Milky Way has been known since ancient times (it's referenced in various cultural mythologies, for example). However, it was only in the past few centuries that it was properly identified as a galaxy, specifically our own.== == The Milky Way's true age hasn't been discovered. The only knowledge we have is of a meteorite which dates 4.7 billion years ago. And yes, Galileo discovered the odd colors of the Milky Way in the 1600's. If we could escape our galaxy, scientists believe it would look like M-31(The Great Galaxy of Andromeda)I would hesitate to talk about a "discovery" of something that is in plain sight - that people have been seeing for ... well, for as long as there have been people. Like the Sun, or the Moon, or trees, or animals - or the Milky Way.
What is the order in decreasing size of spiral giant elliptical dwarf elliptical and irregular galaxies?
Galaxies come in three main types: ellipticals, spirals, and irregulars. A slightly more extensive description of galaxy types based on their appearance is given by the Hubble sequence. Since the Hubble sequence is entirely based upon visual morphological type, it may miss certain important characteristics of galaxies such as star formation rate (in starburst galaxies) and activity in the core (in active galaxies).Elliptical galaxyThe Hubble classification system rates elliptical galaxies on the basis of their ellipticity, ranging from E0, being nearly spherical, up to E7, which is highly elongated. These galaxies have an ellipsoidal profile, giving them an elliptical appearance regardless of the viewing angle. Their appearance shows little structure and they typically have relatively little interstellar matter. Consequently these galaxies also have a low portion of open clusters and a reduced rate of new star formation. Instead the galaxy is dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions. In this sense they have some similarity to the much smaller globular clusters.The largest galaxies are giant ellipticals. Many elliptical galaxies are believed to form due to the interaction of galaxies, resulting in a collision and merger. They can grow to enormous sizes (compared to spiral galaxies, for example), and giant elliptical galaxies are often found near the core of large galaxy clusters.Starburst galaxies are the result of such a galactic collision that can result in the formation of an elliptical galaxy.Spiral galaxy and Barred spiral galaxyThe Sombrero Galaxy, an example of an unbarred spiral galaxy. Credit:Hubble Space Telescope/NASA/ESA.Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) that indicates the degree of tightness of the spiral arms and the size of the central bulge. An Sa galaxy has tightly wound, poorly-defined arms and possesses a relatively large core region. At the other extreme, an Sc galaxy has open, well-defined arms and a small core region.In spiral galaxies, the spiral arms have the shape of approximate logarithmic spirals, a pattern that can be theoretically shown to result from a disturbance in a uniformly rotating mass of stars. Like the stars, the spiral arms also rotate around the center, but they do so with constant angular velocity. That means that stars pass in and out of spiral arms, with stars near the galactic core orbiting faster than the arms are moving while stars near the outer parts of the galaxy typically orbit more slowly than the arms. The spiral arms are thought to be areas of high density matter, or "density waves". As stars move through an arm, the space velocity of each stellar system is modified by the gravitational force of the higher density. (The velocity returns to normal after the stars depart on the other side of the arm.) This effect is akin to a "wave" of slowdowns moving along a highway full of moving cars. The arms are visible because the high density facilitates star formation, and therefore they harbor many bright and young stars.NGC 1300, an example of a barred spiral galaxy. Credit:Hubble Space Telescope/NASA/ESA.A majority of spiral galaxies have a linear, bar-shaped band of stars that extends outward to either side of the core, then merges into the spiral arm structure. In the Hubble classification scheme, these are designated by an SB, followed by a lower-case letter (a, b or c) that indicates the form of the spiral arms (in the same manner as the categorization of normal spiral galaxies). Bars are thought to be temporary structures that can occur as a result of a density wave radiating outward from the core, or else due to a tidal interaction with another galaxy. Many barred spiral galaxies are active, possibly as a result of gas being channeled into the core along the arms.Our own galaxy is a large disk-shaped barred-spiral galaxy about 30 kiloparsecs in diameter and a kiloparsec in thickness. It contains about two hundred billion (2×1011) stars and has a total mass of about six hundred billion (6×1011) times the mass of the Sun.Other morphologiesHoag's Object, an example of a ring galaxy. Credit:Hubble Space Telescope/NASA/ESA.Peculiar galaxies are galactic formations that develop unusual properties due to tidal interactions with other galaxies. An example of this is the ring galaxy, which possesses a ring-like structure of stars and interstellar medium surrounding a bare core. A ring galaxy is thought to occur when a smaller galaxy passes through the core of a spiral galaxy. Such an event may have affected the Andromeda Galaxy, as it displays a multi-ring-like structure when viewed in infrared radiation.A lenticular galaxy is an intermediate form that has properties of both elliptical and spiral galaxies. These are categorized as Hubble type S0, and they possess ill-defined spiral arms with an elliptical halo of stars. (Barred lenticular galaxies receive Hubble classification SB0.)NGC 5866, an example of a lenticular galaxy. Credit:Hubble Space Telescope/NASA/ESAIn addition to the classifications mentioned above, there are a number of galaxies that can not be readily classified into an elliptical or spiral morphology. These are categorized as irregular galaxies. An Irr-I galaxy has some structure but does not align cleanly with the Hubble classification scheme. Irr-II galaxies do not possess any structure that resembles a Hubble classification, and may have been disrupted. Nearby examples of (dwarf) irregular galaxies include the Magellanic Clouds.Dwarf galaxyDespite the prominence of large elliptical and spiral galaxies, most galaxies in the universe appear to be dwarf galaxies. These tiny galaxies are about one hundredth the size of the Milky Way, containing only a few billion stars. Ultra-compact dwarf galaxies have recently been discovered that are only 100 parsecs across.Many dwarf galaxies may orbit a single larger galaxy; the Milky Way has at least a dozen such satellites, with an estimated 300-500 yet to be discovered. Dwarf galaxies may also be classified as elliptical, spiral, or irregular. Since small dwarf ellipticals bear little resemblance to large ellipticals, they are often called dwarf spheroidal galaxies instead
How many black holes have people discovered?
If you know,there lies a black hole at the center of every galaxy,so the number of galaxies in the universe,same number of black holes.But there could be trillions of galaxies,witch also means trillions of black holes. There maybe a black hole in the center of every galaxy but there are also called stellar black holes. Stellar black holes can be find ANYWHERE in space.So it is not only the ammount of galaxies. There is a unknown answer to this question.There might be billions of black holes. Scientists do not know yet. Since we can only see about 13 billion lightyearsof the Universe from this position, its impossible to know even an estimated number of anything in the universe. That's including black holes.
Is Venus the hottest planet in the galaxy?
Probably not; we only know of a couple dozen planets or so total, yet the galaxy must have billions if not trillions of planets in it.
How many genearation of stars does the milky way contain?
Some of the white dwarf stars may be only first or second generation; some stars, like the Sun, are certainly at least 3rd. Some of the giant stars may be 4th or 5th; there's no way to tell. Small dim stars are very long-lived; very large, very bright stars may exhaust their fuel in only a few dozen million years. Some stars might easily be in the 8th or 10th generation; we really have no way to know.
