Data from Gaia has been described as "transformational". It has been estimated that Gaia has expanded the number of observations of stars from about 2 million stars as of the 1990s to 2 billion. It has expanded the measurable volume of space by a factor of 100 in radius and a factor of 1,000 in precision. [93] Main articles: List of names for the Milky Way and Milky Way (mythology) The Origin of the Milky Way, by Tintoretto ( c. 1575–1580) a b "100 Billion Alien Planets Fill Our Milky Way Galaxy: Study". Space.com. January 2, 2013. Archived from the original on January 3, 2013 . Retrieved January 3, 2013. In March 2019, astronomers reported that the virial mass of the Milky Way Galaxy is 1.54 trillion solar masses within a radius of about 39.5kpc (130,000ly), over twice as much as was determined in earlier studies, suggesting that about 90% of the mass of the galaxy is dark matter. [7] [8] a b Bland-Hawthorn, Joss; Gerhard, Ortwin (2016). "The Galaxy in Context: Structural, Kinematic, and Integrated Properties". Annual Review of Astronomy and Astrophysics. 54: 529–596. arXiv: 1602.07702. Bibcode: 2016ARA&A..54..529B. doi: 10.1146/annurev-astro-081915-023441. S2CID 53649594.

The stars and gas in the Milky Way rotate about its center differentially, meaning that the rotation period varies with location. 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. Away from the central bulge or outer rim, the typical stellar orbital speed is between 210±10km/s (470,000±22,000mph). [237] Hence the orbital period of the typical star is directly proportional only to the length of the path traveled. This is unlike the situation within the Solar System, where two-body gravitational dynamics dominate, and different orbits have significantly different velocities associated with them. The rotation curve (shown in the figure) describes this rotation. Toward the center of the Milky Way the orbit speeds are too low, whereas beyond 7 kpcs the speeds are too high to match what would be expected from the universal law of gravitation. [ citation needed] This is a small chocolate star shaped candy that is not a bar. These little treats are made with unique magic star characters on each one. There is a whole cast of characters associated with these little candies and the characters are part of how the bar is marketed there.The Milky Way's spiral structure is uncertain, and there is currently no consensus on the nature of the Milky Way's arms. [204] Perfect logarithmic spiral patterns only crudely describe features near the Sun, [202] [205] because galaxies commonly have arms that branch, merge, twist unexpectedly, and feature a degree of irregularity. [176] [205] [206] The possible scenario of the Sun within a spur / Local arm [202] emphasizes that point and indicates that such features are probably not unique, and exist elsewhere in the Milky Way. [205] Estimates of the pitch angle of the arms range from about 7° to 25°. [149] [207] There are thought to be four spiral arms that all start near the Milky Way Galaxy's center. [208] These are named as follows, with the positions of the arms shown in the image below: According to observations utilizing adaptive optics to correct for Earth's atmospheric distortion, stars in the galaxy's bulge date to about 12.8 billion years old. [261]

Artist's conception of the spiral structure of the Milky Way with two major stellar arms and a bar. [204] The Milky Way candy bar is often thought incorrectly to be named after space. This is not actually the case and it was named after the malted milk drinks that were popular at the time in many confectionaries and soda shop items. Malted milk was actually first sold as a baby formula and was still being associated with the health food category when the Milky Way Bar was first being made. The Milky Way brand extended into variations beginning in 1936. The Forever Yours bar is actually a spin-off of the original vanilla version made in 1926. The Forever Yours bar was first made in 1936 and includes chewy (not creamy) caramel, fluffy vanilla nougat, encased in bittersweet dark chocolate. This candy bar eventually ended up being discontinued in 1979. In the UK and Australia, there was also a slogan that said, “The sweet you can eat between meals without ruining your appetite”. While this is a bit of a mouthful, during the years where candy was thought to be a suitable meal replacement for good health, this was how a lot of candy bars advertised themselves. Current measurements suggest the Andromeda Galaxy is approaching the Milky Way at 100 to 140km/s (220,000 to 310,000mph). In 4.3 billion years, there may be an Andromeda–Milky Way collision, depending on the importance of unknown lateral components to the galaxies' relative motion. If they collide, the chance of individual stars colliding with each other is extremely low, [277] but instead the two galaxies will merge to form a single elliptical galaxy or perhaps a large disk galaxy [278] over the course of about six billion years. [279] Velocity [ edit ]Alternative gravity theories such as modified Newtonian dynamics reject the idea of dark matter, instead seeking to explain discrepancies by tweaking Einstein’s theory of general relativity. Brenner, Joël Glenn The Emperors of Chocolate: Inside the Secret World of Hershey and Mars p.174 Broadway Books, 04/01/2000 Using this data, the team inferred that the bar – made up of billions of stars and trillions of solar masses – had slowed down its spin by at least 24% since it first formed.

The idea of putting malt-flavored taste in chocolate was because of the malt that was used to create milkshakes. The Milky Way bar name became trademarked by Mars Inc. in 1925. In 1926, the company was moved to Chicago Illinois and shortly thereafter, by 1929, the Milky Way bar was the best-selling candy bar in the United States . Observations of distant galaxies indicate that the Universe had about one-sixth as much baryonic (ordinary) matter as dark matter when it was just a few billion years old. However, only about half of those baryons are accounted for in the modern Universe based on observations of nearby galaxies like the Milky Way. [234] If the finding that the mass of the halo is comparable to the mass of the Milky Way is confirmed, it could be the identity of the missing baryons around the Milky Way. [234] Galactic rotation [ edit ] Galaxy rotation curve for the Milky Way – vertical axis is speed of rotation about the galactic center; horizontal axis is distance from the galactic center in kpcs; the sun is marked with a yellow ball; the observed curve of speed of rotation is blue; the predicted curve based upon stellar mass and gas in the Milky Way is red; scatter in observations roughly indicated by gray bars, the difference is due to dark matter [41] [235] [236] The controversy was conclusively settled by Edwin Hubble in the early 1920s using the Mount Wilson observatory 2.5m (100in) Hooker telescope. With the light-gathering power of this new telescope, he was able to produce astronomical photographs that resolved the outer parts of some spiral nebulae as collections of individual stars. He was also able to identify some Cepheid variables that he could use as a benchmark to estimate the distance to the nebulae. He found that the Andromeda Nebula is 275,000 parsecs from the Sun, far too distant to be part of the Milky Way. [89] [90] Astrography [ edit ] A map of the Milky Way Galaxy with the constellations that cross the galactic plane in each direction and the known prominent components annotated, including main arms, spurs, bar, nucleus/bulge, notable nebulae, and globular clusters An all-sky view of stars in the Milky Way and neighbouring galaxies, based on the first year of observations from Gaia satellite, from July 2014 to September 2015. The map shows the density of stars in each portion of the sky. Brighter regions indicate denser concentrations of stars. Darker regions across the Galactic Plane correspond to dense clouds of interstellar gas and dust that absorb starlight. The nature of the Milky Way's bar is actively debated, with estimates for its half-length and orientation spanning from 1to 5kpc (3,000–16,000ly) and 10–50degrees relative to the line of sight from Earth to the Galactic Center. [175] [176] [185] Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. [186] However, RRLyrae-type stars do not trace a prominent Galactic bar. [176] [187] [188] The bar may be surrounded by a ring called the "5kpc ring" that contains a large fraction of the molecular hydrogen present in the Milky Way, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of the Milky Way. [189] X-ray emission from the core is aligned with the massive stars surrounding the central bar [182] and the Galactic ridge. [190] Enjoy the great taste of Milkybar®. Great tasting creamy smooth white chocolate, enjoy milky deliciousness with no artificial colours, flavours or preservatives.

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A diagram of the Milky Way with the position of the Solar System marked by a yellow arrow and a red dot in the Orion Arm. The dot roughly covers the larger surroundings of the Solar System, the space between the Radcliffe wave and Split linear structures (formerly the Gould Belt). [95] An artistic close-up of the Orion Arm with the main features of the Radcliffe Wave and Split linear structures, and with the Solar System surrounded by the closest large scale celestial features at the surface of the Local Bubble at a distance of 400–500 light years. The disk of stars in the Milky Way does not have a sharp edge beyond which there are no stars. Rather, the concentration of stars decreases with distance from the center of the Milky Way. For reasons that are not understood, beyond a radius of roughly 40,000 light years (13 kpc) from the center, the number of stars per cubic parsec drops much faster with radius. [113] Surrounding the galactic disk is a spherical galactic halo of stars and globular clusters that extends farther outward, but is limited in size by the orbits of two Milky Way satellites, the Large and Small Magellanic Clouds, whose closest approach to the Galactic Center is about 180,000ly (55kpc). [152] At this distance or beyond, the orbits of most halo objects would be disrupted by the Magellanic Clouds. Hence, such objects would probably be ejected from the vicinity of the Milky Way. The integrated absolute visual magnitude of the Milky Way is estimated to be around −20.9. [153] [154] [g] Pache, Corinne Ondine (2010). "Hercules". In Gargarin, Michael; Fantham, Elaine (eds.). Ancient Greece and Rome. Vol.1: Academy-Bible. Oxford, England: Oxford University Press. p.400. ISBN 978-0-19-538839-8. Archived from the original on March 26, 2023 . Retrieved April 24, 2019.

Starr, Michelle (July 14, 2020). "A Giant 'Wall' of Galaxies Has Been Found Stretching Across The Universe". ScienceAlert. Archived from the original on February 5, 2021 . Retrieved May 5, 2022.

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a b Croswell, Ken (March 23, 2020). "Astronomers have found the edge of the Milky Way at last". ScienceNews. Archived from the original on March 24, 2020 . Retrieved March 27, 2020. Shapley, H.; Curtis, H. D. (1921). "The Scale of the Universe". Bulletin of the National Research Council. 2 (11): 171–217. Bibcode: 1921BuNRC...2..171S. Kruit, Pieter C. van der (2019). Jan Hendrik Oort: Master of the Galactic System. Cham, Switzerland: Springer. pp.65, 717. ISBN 978-3-030-17801-7. OCLC 1110483488. Archived from the original on May 2, 2022 . Retrieved April 24, 2022. Because the orbital velocity depends on the total mass inside the orbital radius, this suggests that the Milky Way is more massive, roughly equaling the mass of Andromeda Galaxy at 7 ×10 11 M ☉ within 160,000ly (49kpc) of its center. [130] In 2010, a measurement of the radial velocity of halo stars found that the mass enclosed within 80 kilo parsecs is 7 ×10 11 M ☉. [131] In a 2014 study, the mass of the entire Milky Way is estimated to be 8.5 ×10 11 M ☉, [132] but this is only half the mass of the Andromeda Galaxy. [132] A recent 2019 mass estimate for the Milky Way is 1.29 ×10 12 M ☉. [133]