Wolf–Lundmark–Melotte

From the Science Archives, the open-project database of science information
Jump to navigation Jump to search
Wolf–Lundmark–Melotte
The WLM galaxy on the edge of the Local Group.jpg
The galaxy Wolf–Lundmark–Melotte (WLM), imaged by VLT
Observation data (J2000 epoch)
ConstellationCetus
Right ascension00h 01m 58.1s[1]
Declination−15° 27′ 39″[1]
Redshift-122 ± 2 km/s[1]
Distance3.04 ± 0.11 Mly (930 ± 30 kpc)[2]
Apparent magnitude (V)11.0[1]
Characteristics
TypeIB(s)m[1]
Apparent size (V)11′.5 × 4′.2[1]
Notable features-
Other designations
WLM,[1] DDO 221,[1] UGCA 444,[1] PGC 143[1]
See also: Galaxy, List of galaxies

The Wolf–Lundmark–Melotte (WLM) is an irregular galaxy discovered in 1909 by Max Wolf, located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

Star formation[edit]

In 1994, A. E. Dolphin used the Hubble Space Telescope to create a color–magnitude diagram for WLM. It showed that around half of all the star formation in this galaxy occurred during a starburst that started ~13 Gyr ago. During the starburst, the metallicity of WLM rose from [Fe/H] ~ −2.2 to [Fe/H] −1.3. There being no horizontal-branch population, Dolphin concludes that no more than ~20 M per Myr of star formation occurred in the period from 12 to 15 Gyr ago. From 2.5 to 9 Gyr ago, the mean rate of star formation was 100 to 200 M per Myr.[3] Being at the edge of the Local Group has also protected WLM from interactions and mergers with other galaxies, giving it a "pristine" stellar population and state that make it particularly useful for comparative studies.[4]

Globular cluster[edit]

WLM Globular Cluster, Hubble space telescope

WLM has one known globular cluster (PGC 910901) at 00h 01m 29.5s −15° 27′ 51″ that Hodge et al. (1999) determined having an absolute magnitude of −8.8 and a metallicity of –1.5, with an age of ~15 billion years. This cluster has a luminosity that is slightly over the average for all globulars. The seeming lack of faint low-mass globular clusters cannot be explained by the weak tidal forces of the WLM system.[3]

References in popular culture[edit]

In E. E. Smith’s Lensman novels, the "Second Galaxy" is identified as "Lundmark's Nebula".[5][6] However, some believe the "Second Galaxy" may not be the Wolf–Lundmark–Melotte galaxy, since the first chapter of the first novel in the series (Triplanetary) and the series-establishing material appearing at the beginning of subsequent novels states that the "Second Galaxy" and the "First Galaxy" (the Milky Way) collided and passed through each other "edge-on" during the "planet-forming era"—implying that the "Lundmark's Nebula" of the series must necessarily be obscured from view by the Milky Way; however, according to others, it could have passed through at an angle and thus be identified with the galaxy described in this article; some have stated that this is the galaxy that E.E. Smith was thinking of when he wrote the series. However, the distance to Lundmark's nebula is defined quite precisely in Grey Lensman as approximately 24 million parsecs, much larger than the distance to Wolf–Lundmark–Melotte (approximately 930,000 parsecs). Additionally, in Second Stage Lensmen multiple references are made to the spiral arms of Lundmark's Nebula. Wolf–Lundmark–Melotte does not possess such structures. At the time of writing of these books, the name of Lundmark was associated with such classifications and Smith may have elected to use this as a "believable" name for an entirely fictional galaxy.

At the time the Lensman series was written, most astronomers favored the tidal theory of Solar System formation, which required that planets be formed by the close approach of another star. In order to produce the massive numbers of planets necessary to evolve into the galactic civilizations in both the Milky Way and Lundmark's Nebula portrayed in the Lensman series, E.E. Smith felt it would have been necessary for another galaxy to have passed through the Milky Way in the past to produce the large number of close encounters necessary to form so many planets.

References[edit]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  2. McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A. et al. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society 356 (4): 979–997. arXiv:astro-ph/0410489. Bibcode 2005MNRAS.356..979M. doi:10.1111/j.1365-2966.2004.08514.x.
  3. 3.0 3.1 van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific 112 (770): 529–536. arXiv:astro-ph/0001040. Bibcode 2000PASP..112..529V. doi:10.1086/316548
  4. (eso1610)"The Wilds of the Local Group", 23 March 2016 (Accessed 24/3/2016) http://www.eso.org/public/news/eso1610/
  5. Lua error in Module:Citation/CS1 at line 886: bad argument #1 to 'sub' (string expected, got table).
  6. Lua error in Module:Citation/CS1 at line 886: bad argument #1 to 'sub' (string expected, got table).


Add your comment
The Science Archives welcomes all comments. If you do not want to be anonymous, register or log in. It is free.


As a reminder, article comments are only for discussions on how to improve the article. Please direct other comments to a user's talk page. Please be formal and do not use excessive uppercase. Please be advised you may receive an automatic block if you break the article comments policy. For information regarding what is acceptable/not acceptable in article comments, please message Icons-flag-ru.png Joey (talk), Natalia (talk), Icons-flag-fr.png ynoss (talk), or Icons-flag-ca.png Daniel (older account/talk).