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-------------------------- 2411 - Milky Way Galaxy - our home in the cosmos
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- How big is our galaxy? Counting stars is a tedious business. Even astronomers argue over the best way to do it. Their telescopes see only the brightest stars in our galaxy, and many are hidden by obscuring gas and dust.
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- One technique to estimate the stellar population of the Milky Way is to look at how fast stars are orbiting within it, which gives an indication of the gravitational pull, and therefore the mass of the galaxy. Divide the galactic mass by the average size of a star and you should have your answer.
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- Well, not exactly. These numbers are all approximations. Stars vary widely in size, and many assumptions go into estimating the number of stars residing in the Milky Way. The Gaia satellite has mapped the location of 1 billion stars in our galaxy, and its scientists believe this represents 1 percent of the total, so perhaps the Milky Way contains about 100 billion stars.
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- So, how big is our galaxy? Astronomers are still unsure exactly how much our galaxy weighs, with estimates ranging from 700 billion to 2 trillion times the mass of our Sun. Most of the Milky Way's mass, perhaps 85 percent, is in the form of dark matter, which gives off no light and so is impossible to directly observe.
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- The estimate of the Milky Way's mass is 960 billion times the mass of the Sun. That is 960,000,000,000 which would correspond to that many stars if they were all the same size as our Sun.
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- Our Milky Ways is part of a whole of interconnected strings of galaxies. The large-scale structure of the universe looks like a colossal cosmic web, with string-like filaments connecting dense regions separated by enormous, mostly empty voids. And, our neighborhood is floating in one of these big, empty areas.
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- Lurking in the heart of our Milky Way galaxy is a gigantic blackhole with the weight of 4,000,000 suns. Scientists know that it's there because they can trace the paths of stars in the Milky Way's center and see that they seem to orbit a supermassive object that can't be seen, but gravity knows it is there.
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- In recent years, astronomers have been combining observations from multiple radio telescopes to try and get a glimpse of the environment surrounding this blackhole, which is packed with gas and dust spinning around the blackhole. So far we have only been able to estimate the size and conclude that it is relatively inactive.
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- In between this massive web of interconnected galaxies is “empty” space. And, swirling through this mostly empty space between stars in our own galaxy is a bunch of dirty grease. Oily organic molecules known as “aliphatic carbon compounds” are produced in certain types of stars and then are leaked out into interstellar space.
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- A recent study found that these grease-like substances could account for between a quarter and one-half of the Milky Way's interstellar carbon. The findings are cause for optimism. Because carbon is an essential building block of living things, finding it in abundance throughout the space in our galaxy could suggest that other star systems harbor life.
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- Our galaxy isn't going to be here forever. Astronomers know that we are currently speeding toward our neighbor, the Andromeda galaxy, at around 250,000 mph. When the crash comes, in about 4 billion years, most research has suggested that the more massive Andromeda galaxy would swallow up our own and survive.
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- But in a recent study there emerges a counter view. Other astronomers reweighed Andromeda and found that it was roughly equivalent to 800 billion suns, or about on par with the Milky Way's mass. That means that exactly which galaxy will emerge less scathed from the future galactic crash remains an open question. We will have to wait and see.
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- There are other surprises; Scientists in 2010 uncovered gigantic, never-before-seen structures stretching for 25,000 light-years above and below our galaxy. Named 'Fermi bubbles' after the telescope that found them, these gamma-ray-emitting objects have defied astronomers' explanations ever since. We could not “see” them until we had orbiting gamma-ray telescopes.
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- In 2018, a team gathered evidence suggesting that these bubbles were the aftermath of an energetic event that happened 6 million to 9 million years ago, when the supermassive blackhole in the galactic center swallowed a huge clump of gas and dust and burped out these giant, gamma-ray glowing clouds.
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- There are other mysteries that are being uncovered. Over the last decade, astronomers keep detecting odd flashes of light coming at them from the distant cosmos. Known as fast radio bursts (FRBs), these mysterious signals have no agreed-upon explanation. Despite knowing about them for more than 10 years, researchers had until recently captured only 30 or so examples of these FRBs.
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- In a recent study, Australian scientists managed to find 20 more FRBs, nearly doubling the number of known objects. While they still don't know the odd flashes' origin, the team was able to determine that the light had traveled through several billion light-years of gas and dust, which imparted telltale signs on the signal, suggesting that the FRBs were coming from a long way off, billions of lightyears.
- Our home in the Universe still resides in many more mysteries to be uncovered. We are like someone on the beach picking up pebbles of knowledge with a whole ocean of the unknown extending out over the horizon.
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- June 30, 2019
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--------------------- Sunday, June 30, 2019--------------------
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