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The Whirlpool Galaxy, also known as M51, is a spiral galaxy about 23 million light-years from Earth. Its interactions with the yellowish dwarf galaxy NGC 5195 are of interest to astronomers because the galaxies are near enough to Earth to be well-studied.

Decades ago astronomers could not tell if these two galaxies were just passing each other but radio astronomy has supplied astronomers with important data outlining their interactions. Using this data, astronomers have simulated the interaction. NGC 5195 came from behind and then passed through the main disk of M51 about 500 to 600 million years ago. The dwarf galaxy crossed the disk again between 50 and 100 million years ago and is now slightly behind M51. These interactions appear to have intensified the spiral arms that are the dominant characteristic of the Whirlpool Galaxy.

Astronomers are able to learn about objects unimaginably far away from Earth using telescopes that sense all wavelengths on the electromagnetic spectrum. Imagine what Galileo would do if he could see the images and data astronomers have available to them now.


26.1 Stars
26.2 Galaxies
26.3 The Universe

Maine Connections

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Khan Academy

  1. Scale of Earth and Sun
  2. Scale of Solar System
  3. Scale of Distance to Closest Stars
  4. Scale of the Galaxy
  5. Intergalactic Scale
  6. Hubble Image of Galaxies
  7. Big Bang Introduction
  8. Radius of Observable Universe
  9. (Correction) Radius of Observable Universe
  10. Red Shift
  11. Cosmic Background Radiation
  12. Cosmic Background Radiation 2
  13. Cosmological Time Scale 1
  14. Cosmological Time Scale 2
  15. Four Fundamental Forces
  16. Birth of Stars
  17. Becoming a Red Giant
  18. White and Black Dwarfs
  19. A Universe Smaller than the Observable
  20. Star Field and Nebula Images
  21. Parallax in Observing Stars
  22. Stellar Distance Using Parallax
  23. Stellar Parallax Clarification
  24. Parsec Definition
  25. Hubble's Law
  26. Lifecycle of Massive Stars
  27. Supernova (Supernovae)
  28. Supernova clarification
  29. Black Holes
  30. Cepheid Variables 1
  31. Why Cepheids Pulsate
  32. Why Gravity Gets So Strong Near Dense Objects
  33. Supermassive Black Holes
  34. Quasars
  35. Quasar Correction
  36. Galactic Collisions
  37. Earth Formation