Milky Way

Milky Way
The Milky Way's galactic center in the night sky above the Paranal Observatory (the laser creates a guide for the telescope)
Observation data
Distance	26.4 ± 1.0 kly (8.09 ± 0.31 kpc) (from Sun)[1][2][3]
Characteristics
Type	Sb, Sbc, or SB(rs)bc[4][5] (barred spiral galaxy)
Mass	0.8–1.5×1012 M☉[6][7][8][9] M☉
Number of stars	100–400 billion [(1–4)×1011][10]
See also: Galaxy, List of galaxies

The Milky Way is our home galaxy. It contains around 400 billion stars,^{[11][12][13][14][15]} including our Sun.^[16]

The Milky Way has a diameter of 26.8 ± 1.1 kiloparsecs (87,400 ± 3,600 light-years) as measured using the D₂₅isophote,^[17][18][19] and is a barred spiral galaxy. The idea that the Milky Way is made of stars goes back to the Ancient Greek philosopher Democritus.^[16]

The Milky Way has three main parts: a disk, where the Solar System is, a bulge at the core, and an outer halo all around it.^[20] Although the word "disk" suggests it is flat, the Milky Way is actually not quite flat. It is slightly warped and twisted.^[21]

This galaxy belongs to the Local Group of three large galaxies and over 50 smaller galaxies. The Milky Way is one of the largest galaxies in the group, second to the Andromeda Galaxy.^[11] Its closest neighbour is the Canis Major Dwarf Galaxy, which is about 25,000 light years away from the Earth. The Andromeda Galaxy is moving towards the Milky Way Galaxy and will collide with it in about 3.75 billion years.^[22] The Andromeda Galaxy moves with a speed of about 1,800 kilometres per minute.^[16]

Origin: "Two of the Milky Way's earliest building blocks" are known; Shakti and Shiva seem "to be (left-overs or) remnants of two galaxies that (were joined or) merged ... with an early version of the Milky Way"; That seems to have happened "between 12 and 13 billion years ago";.^[23]

1. ↑ Gillessen, S.; et al. (2009). "Monitoring stellar orbits around the massive black hole in the Galactic Center". Astrophysical Journal. 692 (2): 1075–1109. arXiv:0810.4674. Bibcode:2009ApJ...692.1075G. doi:10.1088/0004-637X/692/2/1075. ISSN 0004-637X. S2CID 1431308.
2. ↑ Boehle, A.; Ghez, A. M.; Schödel, R.; Meyer, L.; Yelda, S.; Albers, S.; Martinez, G. D.; Becklin, E. E.; Do, T.; Lu, J. R.; Matthews, K.; Morris, M. R.; Sitarski, B.; Witzel, G. (October 3, 2016). "An Improved Distance and Mass Estimate for SGR A* from a Multistar Orbit Analysis" (PDF). The Astrophysical Journal. 830 (1): 17. arXiv:1607.05726. Bibcode:2016ApJ...830...17B. doi:10.3847/0004-637X/830/1/17. hdl:10261/147803. S2CID 307657.
3. ↑ Gillessen, Stefan; Plewa, Philipp; Eisenhauer, Frank; Sari, Re'em; Waisberg, Idel; Habibi, Maryam; Pfuhl, Oliver; George, Elizabeth; Dexter, Jason; von Fellenberg, Sebastiano; Ott, Thomas; Genzel, Reinhard (November 28, 2016). "An update on monitoring stellar orbits in the galactic center". The Astrophysical Journal. 837 (1): 30. arXiv:1611.09144. Bibcode:2017ApJ...837...30G. doi:10.3847/1538-4357/aa5c41. S2CID 119087402.
4. ↑ Gerhard, O. (2002). "Mass distribution in our Galaxy". Space Science Reviews. 100 (1/4): 129–138. arXiv:astro-ph/0203110. Bibcode:2002SSRv..100..129G. doi:10.1023/A:1015818111633. S2CID 42162871.
5. ↑ Frommert, Hartmut; Kronberg, Christine (August 26, 2005). "Classification of the Milky Way Galaxy". SEDS. Archived from the original on May 31, 2015. Retrieved May 30, 2015.
6. ↑ McMillan, P. J. (July 2011). "Mass models of the Milky Way". Monthly Notices of the Royal Astronomical Society. 414 (3): 2446–2457. arXiv:1102.4340. Bibcode:2011MNRAS.414.2446M. doi:10.1111/j.1365-2966.2011.18564.x. S2CID 119100616.
7. ↑ McMillan, Paul J. (February 11, 2017). "The mass distribution and gravitational potential of the Milky Way". Monthly Notices of the Royal Astronomical Society. 465 (1): 76–94. arXiv:1608.00971. Bibcode:2017MNRAS.465...76M. doi:10.1093/mnras/stw2759.
8. ↑ Kafle, P.R.; Sharma, S.; Lewis, G.F.; Bland-Hawthorn, J. (2012). "Kinematics of the Stellar Halo and the Mass Distribution of the Milky Way Using Blue Horizontal Branch Stars". The Astrophysical Journal. 761 (2): 17. arXiv:1210.7527. Bibcode:2012ApJ...761...98K. doi:10.1088/0004-637X/761/2/98. S2CID 119303111.
9. ↑ Kafle, P.R.; Sharma, S.; Lewis, G.F.; Bland-Hawthorn, J. (2014). "On the Shoulders of Giants: Properties of the Stellar Halo and the Milky Way Mass Distribution". The Astrophysical Journal. 794 (1): 17. arXiv:1408.1787. Bibcode:2014ApJ...794...59K. doi:10.1088/0004-637X/794/1/59. S2CID 119040135.
10. ↑ Odenwald, S. (March 17, 2014). "Counting the Stars in the Milky Way". The Huffington Post. Archived from the original on August 1, 2014. Retrieved June 9, 2014.
11. ↑ ^{11.0 11.1} "The Milky Way Galaxy". seds.org. Archived from the original on 20 April 1999. Retrieved 5 August 2010.
12. ↑ "The Milky Way Galaxy". cass.ucsd.edu. Retrieved 5 August 2010.
13. ↑ "NASA - Galaxy". nasa.gov. Archived from the original on 8 May 2005. Retrieved 5 August 2010.
14. ↑ "01.09.2006 - Milky Way Galaxy is warped and vibrating like a drum". berkeley.edu. Retrieved 5 August 2010.
15. ↑ "How many stars are in the Milky Way?". universetoday.com. Retrieved 5 August 2010.
16. ↑ ^{16.0 16.1 16.2} "Milky Way; Discovery of Milky Way; Milky Way Galaxy. SPACE.com". space.com. Retrieved 5 August 2010.
17. ↑ Goodwin, S. P.; Gribbin, J.; Hendry, M. A. (22 April 1997). "The Milky Way is just an average spiral". arXiv:astro-ph/9704216.
18. ↑ Goodwin, S. P.; Gribbin, J.; Hendry, M. A. (August 1998). "The relative size of the Milky Way". The Observatory. 118: 201–208. Bibcode:1998Obs...118..201G.
19. ↑ Castro-Rodríguez, N.; López-Corredoira, M.; Sánchez-Saavedra, M. L.; Battaner, E. (2002). "Warps and correlations with intrinsic parameters of galaxies in the visible and radio". Astronomy & Astrophysics. 391 (2): 519–530. arXiv:astro-ph/0205553. Bibcode:2002A&A...391..519C. doi:10.1051/0004-6361:20020895. S2CID 17813024.
20. ↑ "Our own Galaxy - the Milky Way". University of Cambridge. 1996. Archived from the original on 2012-12-03. Retrieved 2012-11-12.
21. ↑ Ghosh, Pallab 2019. Milky Way galaxy is warped and twisted, not flat. BBC News Science & Environment. [1]
22. ↑ NASA 2012. NASA's Hubble shows Milky Way is destined for head-on collision. NASA - NASA's Hubble shows Milky Way is destined for head-on collision
23. ↑ https://www.sciencedaily.com/releases/2024/03/240321155515.htm. Retrieved 2024-04-11