- 3174 - UNIVERSE - age and rotation? We think our Universe was born about 13.7 billion years ago. This newborn universe didn’t look like it does today, with elegant, star-filled galaxies strewn in all directions. Instead of stars and galaxies, the early universe was filled with gas and dark matter.
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- As dark matter coalesced into clumps, it pulled in gas and triggered stars, and thus galaxies, to form. This star and galaxy formation ramped up over a few billion years, reaching its peak 10 billion years ago.
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- Spiral arms of stars were discovered in an unexpected place, a giant, extremely luminous galaxy about 12.3 billion years ago, offering a new puzzle for astronomers to ponder.
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- Previously, astronomers had found galaxies with spiral arms that had formed as early as about 10 to 11 billion years ago. Astronomers find these snapshots of galaxies from billions of years in the past by looking deep into space.
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- Since light travels through a vacuum at a set speed, pointing a telescope at a galaxy that’s a billion light-years away means we see what that galaxy looked like a billion years ago.
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- This newly discovered galaxy, BRI 1335-0417, is forming about 5,000 solar masses worth of stars per year. The Milky Way galaxy is forming something like one to two solar masses’ worth of stars per year, though there may have been small bursts in star formation in the past. This galaxy also has a “quasar’ in its center, a supermassive blackhole that’s actively gobbling up nearby mass.
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- Larger galaxies break down into a few different types, including disc, elliptical, and irregular galaxies. Disc galaxies, including spiral galaxies like the Milky Way, are called this because of their relatively flat plane of stars.
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- What’s especially interesting about this galaxy is that it’s forming stars so intensely and contains a quasar in its center. A galaxy like this is often the product of two galaxies smashing together and merging.
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- If that’s what happened to this galaxy it somehow managed to form a disc and spiral arms in the time since such a collision. Hot gas in this galaxy was rotating around the galaxy center.
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- The velocities of gas at different points in the galaxy match a typical pattern found in galaxies with discs, implying that this galaxy has a fairly well-defined disc. The rotation speeds of gas in the arm-like structures match the rotation speeds of the disc, suggesting the structures could be arms within the disc rather than streams of gas outside it.
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- The presence of spiral arms in a galaxy can affect how gas moves within a galaxy and encourage dense structures to form in galaxy centers, like the bar in the center of the Milky Way.
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- Spiral galaxies have distinct internal structures including a stellar bulge, disk and spiral arms. It is unknown when in cosmic history these structures formed. This intensely star-forming galaxy in the distant Universe has a redshift of 4.41.
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- The gas kinematics show a steep velocity rise near the galaxy center and have a two-armed spiral morphology, which extends from about 2 to 5 kiloparsecs in radius.
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- We interpret these features as due to a central compact structure, such as a bulge; a rotating gas disk; and either spiral arms or tidal tails. These features had formed within 1.4 billion years after the Big Bang, long before the peak of cosmic star formation.
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- Anther interesting galaxy, UGC 10738, had a thick disc containing ancient stars formed billions of years ago and a thin disc of relatively younger stars. The two star-filled discs were strikingly similar to those located in the Milky Way galaxy.
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- This presented the astronomers with a rare opportunity to compare our own galaxy with its very own galactic twin, a galaxy that may have evolved in a similar fashion to the Milky Way. They found that the Milky Way may have evolved gradually over time rather than having formed as a result of a massive collision between galaxies.
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- Their observations revealed that galaxy UGC 10738 has a thick disc consisting mostly of ancient stars, which have a low ratio of iron to hydrogen and helium, while its thin disc stars are younger and contain more metal, a sign that they formed from material left over by previous generations of stars.
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- Our Sun is a thin disc star, forming around 4.5 billion years ago. These discs have been observed in galaxies before, but it was nearly impossible to tell whether they hosted the same kind of star distribution between the two discs.
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- By confirming that this galaxy has a similar distribution of young and old stars between its thin and thick discs, the astronomers concluded that it had a similar origin story to that of the Milky Way.
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- Nearly 14 billion years ago, enormous clouds of gas and dust collapsed under the weight of their own gravity to form the Milky Way. These clouds then formed two main structures: a spherical halo, and a dense, bright disk.
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- A popular theory suggests that around 11 billion years ago, a small galaxy called Gaia-Enceladus slammed into the primordial Milky Way.
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- The Milky Way today is headed for a collision with its neighboring galaxy, Andromeda, within the next several billion years But the new study suggests that instead of a massive collision, the Milky Way came to be by way of natural progression.
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- Our observations indicate that the Milky Way’s thin and thick discs didn’t come about because of a gigantic mash-up, but a sort-of ‘default’ path of galaxy formation and evolution.
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- The Milky Way was unique in that it formed as a result of mergers with other, smaller galaxies and therefore its structure was not observable with other spiral galaxies.
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- The new findings also don’t necessarily contradict the theory that the Milky Way collided with other smaller galaxies over time, leading to its structure today. This is perhaps the closest comparison scientists have observed to our home galaxy and may suggest that the Milky Way is somewhat typical.
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- The Milky Way disk consists of two prominent components — a thick, alpha-rich, low-metallicity component and a thin, metal-rich, low-alpha component. External galaxies have been shown to contain thin and thick disk components, but whether distinct components in the [α/Fe]–[Z/H] plane exist in other Milky Way-like galaxies is not yet known.
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- We present VLT-MUSE observations of UGC 10738, a nearby, edge-on Milky Way-like galaxy. We demonstrate through stellar population synthesis model fitting that UGC 10738 contains alpha-rich and alpha-poor stellar populations with similar spatial distributions to the same components in the Milky Way.
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- We discuss how the finding that external galaxies also contain chemically distinct disk components may act as a significant constraint on the formation of the Milky Way’s own thin and thick disk.---------------------------------- Other reviews to cover the Universe.
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- 3151 - UNIVERSE - size and beyond? The universe doesn't need that outside perspective in order to exist. The universe simply is. It is entirely mathematically self-consistent to define a three-dimensional universe without requiring an outside to that universe.
- 3143 - UNIVERSE - rate of expansion? The disagreement over the Hubble constant of expansion is one of the biggest mysteries in cosmology today. In addition to helping us unravel this puzzle, the spacetime ripples from these cataclysmic events open a new window on the universe. We can anticipate many exciting discoveries in the coming decade.
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- 3142 - UNIVERSE - is it also rotating? This Review tackles the question. Einstein’s theory of general relativity is our only validated theory of the universe as a whole. Without it we would have difficulty explaining where the universe came from and where it is going.
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- 3135 - UNIVERSE - what is it expanding in to? - If the Universe is infinite, how can infinity be expanding? Astronomers believe the Universe is finite and that eventually it comes back on itself. To explain this we have to decide the shape of the Universe. The shape is flat?
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- 3106 - UNIVERSE - The Universe you live in? Space is completely silent. Sound needs an atmosphere to travel through, and since space has no atmosphere, it has no sound. The biggest, most awe-inspiring exploding star wouldn’t even make a peep. Astronauts are able to communicate up there thanks to radio waves, which can travel through space.
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- 3101 - UNIVERSE - Is it spinning, or, is it just me? An initial spinning Universe could cause parity-violating asymmetry where gravity is allowing matter to dominate over anti-matter. Bold theories still need a preponderance of evidence. A spinning Universe is a new idea. What does it all mean?
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- 2016 - Birth of the Universe. The universe was born 13.8 billion years ago. Our telescopes can see back 13 billion years. This is when the Universe was only 800,000 years old.
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- 2008 - The universe almost did not happen. There is a fine tuning problem for many of the constants in physics. Change any of these constants only slightly and the universe we know would not have happened.
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- 1991 - Universe - what are the odds? Our whole existence appears to be n the very edge of the best conditions. Our bodies are a collection of elements that were formed inside exploding stars. So, what are the odds you are able to read this review?
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- 1493 - The universe is expanding at an ever accelerating rate due to a vacuum energy that we do not understand. This energy will eventually over come all the gravity in the universe. Enjoy life while you have it. The future is not bright.
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- 1836 - 95% of the universe is Dark Matter and Dark Energy that we do not understand. General Relativity was the theory used to detect gravitational waves. These are ripples in Einstein’s space-time.
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- 1821 - Describing the universe. The universe can be described with a model using just 6 qualities. Astronomy is a time machine that looks backwards in time. Hubble’s law describes the expansion.
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- May 27, 2021 UNIVERSE 3174
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--------------------- --- Friday, May 28, 2021 ---------------------------
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