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M31

Messier 31
Andromeda Galaxy
Spiral Galaxy

Right Ascension 0h 42m 44s Best Seen 10/1-3/1
Declination 41° 16' 05" Magnitude 3.4
Constellation Andromeda

Actual
Compared
to Milky Way
Distance 2.5 million ly --
Actual Brightness 11 billions suns --
Diameter 200,000 ly ~1.5
Mass 400 billion suns --
Galactic Type Sb Sbc

What To Look For Through The Telescope


  1. Recommended eyepiece: 40 mm on 16 inch, 32 mm on 6 inch.

  2. When people look through the telescope they should see a fuzzy patch of light. This is the galaxy. In fact the galaxy is so large that all it cannot fit in the field of view.

  3. If they are having trouble seeing it, have them look at a star near the edge of the field, then look back to the center out of the corner of their eye.

  4. The view through the telescope will not look like photographs of galaxies they may have seen. A photograph of a galaxy may have an exposure of many hours. This long exposure brings out the spiral arms and other details. Our eyes allow the light to collect for only about 1/30 of a second before they refresh themselves and start over again.


M31 Information


  1. This galaxy is the famous Andromeda Galaxy.

  2. This galaxy is a member of the local group.

  3. It is surrounded by about 140 globular clusters.

  4. This galaxy can be seen with the unaided eye -- it is the furthest object that can be seen with the naked eye, it is 2.5 million light years from Earth.. It was known to the Persian astronomer Abd-al-Rahman Al-Sufi who described it in his book Book of Fixed Stars in 964 A.D.

  5. It is visible in both the Northern and Southern hemispheres. In the Northern hemisphere Andromeda, can be seen from August to February. In the Southern hemisphere, the constellation can be viewed from October to December.

  6. The Andromeda galaxy is at least two times as large as our Milky Way galaxy, yet the Andromeda galaxy has less mass than our galaxy. Our Milky Way galaxy is more dense than M31.

  7. The disk of the Andromeda galaxy is slightly warped, possibly due to interactions with its companion M32.

  8. The Andromeda galaxy is orbited by several smaller galaxies, some of which are visible through a telescope or binoculars.

  9. The nucleus rotates in about 11 million years. The outer portions of the galaxy rotate in 100 to 200 million years.

  10. With the Hubble Space Telescope, astronomers discovered that the Andromeda galaxy has a double nucleus, possibly because of a collision with another galaxy in the past, or because there’s dust obscuring part of the nucleus.

  11. In 1923, Edwin Hubble found the first Cepheid variable star in the Andromeda galaxy, confirming a distance to M31 that placed it well outside of our own galaxy.

  12. The Andromeda galaxy has been studied so much because we can see all the features of a galaxy that we can’t see in our own because of interstellar dust. With M31, we can study spiral structure, globular and open clusters, interstellar matter, supernova remnants, planetary nebulae, galactic nuclei, companion galaxies, and more.

  13. The Andromeda constellation is one of the original constellations listed by the Greco-Roman scientist Ptolemy almost 2,000 years ago.

Home > Galaxies > Spiral > M31 > References top
References
Item Updated Notes
Coordinates 2002-09-30 just tweaked a bit
Magnitude 2002-09-30 previously: 4.88.7
– BUT found mag at
http://messier.seds.org/m/m031.html
Distance 2002-09-30 OK
Diameter 2002-09-30 OK
Mass --
Brightness --
Other Information 2002-09-30 lots of info and reminders from the SEDS site http://messier.seds.org/m/m031.html