Magellanic clouds

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Small and Large Magellanic Cloud

The Magellanic Clouds are two irregular dwarf galaxies in relative proximity to the Milky Way and thus part of the Local Group . They are counted in the Milky Way subgroup but may not be gravitationally bound to the galaxy. The Large Magellanic Cloud about 163,000 light years away contains about 15 billion stars, the Small Magellanic Cloud about 200,000 light years away contains 5 billion stars.

The Large Magellanic Cloud is in the constellations Swordfish and Table Mountain , the Small Magellanic Cloud in the constellation Toucan on the border with the Little Water Snake , both in the southern sky . They are not visible from Central Europe . The inhabitants of the southern hemisphere had known the two galaxies since prehistoric times through observations with the naked eye, but they were first mentioned in writing by the Persian astronomer Al Sufi in his book of fixed stars in 964.

The first European to describe the two clouds was the Italian navigator Andrea Corsali in a letter of January 6, 1515 to Giuliano di Lorenzo de 'Medici , his compatriot Antonio Pigafetta mentioned the cloud-like formations ten years later in his much-read travelogue about the first circumnavigation of the world under the command of Ferdinand Magellan . In the telescope, their character is revealed as a galaxy made up of stars , nebulae , star clusters and other objects . After the Milky Way, the Andromeda Nebula and the Triangle Nebula , the Large Magellanic Cloud is the fourth largest galaxy in the Local Group.

Large and Small Magellanic Clouds are abbreviated as GMW and KMW or English with LMC and SMC (Large / Small Magellanic Cloud) .

Data

Surname Catalog number Type Entf. / KLj (kpc) Diameter / kLj (kpc) Mass / M ☉ Right ascension declination vis. brightness Skylinks
Large Magellanic Cloud ESO 56-115 SBm / Irr 162.98 ± 3.62 (49.97 ± 1.11) 25.1 (7.7) 10 10 5 h 24 m 1305200−69 ° 48 ′ 0 ″ 0.9 mag Database links to GMW
Small Magellanic Cloud NGC 292 Insane ≈209 (≈64) 10.1 (3.1) 2 · 10 9 0 h 51 m 1269400−73 ° 6 ′ 0 ″ 2.7 likes Database links to KMW
Explanation: kLj = kilo light year (thousand light years ) • kpc = kiloparsec (thousand parsec ) • M ☉ = solar mass .

distance

The Great Magellanic Cloud

The distance, especially to the GMW, has played a key role in extragalactic astronomy in the last century, but has also repeatedly caused confusion. The great interest is mainly due to the fact that the extragalactic distance measurement is based on the period-brightness relationship of the variable Cepheid stars. This relationship was not only discovered on the basis of Cepheids in the KMW, but is also calibrated and checked on the Cepheids of the GMW to this day. However, this means that all errors in determining the distance of the Magellanic Clouds extend directly to determining the distance of other galaxies. In particular, misinterpretations of the period-brightness relationship in the first half of the 20th century led to enormous fluctuations in the cosmic scales determined.

To this day, different sources contain different information for the distance of the Magellanic Clouds, varying between 40 and 80 kpc . Research in current scientific publications shows that research continues in this area. However, the measurement errors, especially in the course of researching the Supernova 1987A in the GMW, have significantly decreased. Until the beginning of 2013, a distance of between 44 and 51 kpc (143,000 to 166,000 light years ) was last considered to be certain for the Large Magellanic Cloud . According to the latest research carried out by the Paranal Observatory using pairs of eclipsing variables , so-called cool red giants , a distance of 163,000 light years +/- 2% is now considered to be certain (published in March 2013). According to ESO , a further reduction in uncertainty to just 1% is expected over the next few years.

description

NGC 346 in the Small Magellanic Cloud

Both Magellanic Clouds consist mainly of objects from Population I , with the stars in the KMW having a more uniform distribution. Large and Small Magellanic Clouds have a quarter and 1/20 of the luminosity of the Milky Way.

In the Magellanic Clouds there are numerous objects of interest for amateur astronomers, such as the gas nebula 30 Doradus (NGC 2070) known as the tarantula nebula . In its center is the super star cluster R136 , which is responsible for the ionization of the nebula and contains numerous massive stars, including R136a1 , the most massive and brightest known star (265 M ☉ , 10 7  L ☉ ).

Furthermore, many star clusters in the Magellanic Clouds are already visible in the small telescope, some of which belong to the class of blue globular star clusters , a class of objects that does not exist in the Milky Way.

The Supernova 1987A in the GMW made it possible for the first time to observe a supernova and its effects with modern instruments. Although there were supernovae in our own galaxy in the past, which were much closer to us, the last of these occurred in 1604, before the invention of the telescope.

Position of the Magellanic Clouds relative to the Milky Way. Abbreviations:
• GMW   - Large Magellanic Cloud
• KMW - Small Magellanic Cloud
• GSP - Galactic South Pole
• MSI - First hydrogen compression in the Magellanic Current
• 3 -   30 Doradus
• W - Wing of the KMW
The green arrow indicates the direction of rotation of the Magellanic Clouds around the center of the Milky Way.

The two Magellanic Clouds are connected to each other by the Magellanic Bridge and also to the Milky Way by a thin hydrogen band, the Magellanic Current .

The clouds are in the constellations Swordfish / Table Mountain (GMW) and Toucan (KMW). Due to their small distance to the earth and their large size, they have an apparent diameter of about 6 ° and 3.5 ° for an earthly observer. Because of this and their great apparent brightness, they can be seen with the naked eye from Earth - but only from the southern hemisphere.

Although the Large Magellanic Cloud is currently moving away from the Milky Way, simulations have calculated that it will likely collide with the Milky Way in one to four billion years.

NGC objects in the Large Magellanic Cloud (selection)

In or around the Large Magellanic Cloud there are numerous star clusters and nebulae that are listed in the NGC catalog. These objects can be observed even with small telescopes:

NGC objects in the Small Magellanic Cloud (selection)

There are also numerous star clusters and nebulae in the Small Magellanic Cloud that are listed in the NGC catalog. These objects can be observed even with small telescopes. Globular clusters 47 Tucanae and NGC 362 are not members of the Small Magellanic Cloud .

Trivia / science fiction

  • The Perry Rhodan - Heftroman series of the 1960s and 70s shifted levels of action in the Magellanic Clouds.
  • In Dan Simmons ' series of novels, Hyperion , an unknown alien force moved Earth to the Magellanic Clouds after humanity abandoned the planet.
  • In Bungie's video game series Halo , the Large Magellanic Cloud is the homeworld of the parasitic life form the Flood.
  • In the Star Trek: Titan novel series, the Neyel Territory is located in the small Magellanic Cloud. The Neyel are descendants of mankind. The USS Titan and USS Excelsior are displaced into the cloud by a spatial anomaly.

Web links

Commons : Large Magellanic Cloud  - collection of images, videos and audio files
Commons : Small Magellanic Cloud  - collection of images, videos and audio files

Individual evidence

  1. ↑ Thomas Bührke in Süddeutsche Zeitung of May 17, 2010: Only in transit , accessed on February 2, 2020
  2. ↑ http://www.astronews.com/frag/lösungen/1/frage1149.html
  3. ↑ Guglielmo Berchet (Ed.): Raccolta di documenti e studi pubblicati dalla R. Commissione Colombiana pel quarto centenario dalla scoperta dell'America . Part III, Vol. II. Rome 1893, p. 241 f .
  4. ^ Boston Public Library: Magellan's voyage around the world . Cleveland: The Arthur H. Clark Company, 1906 ( archive.org [accessed April 4, 2018]).
  5. ↑ NASA / IPAC Extragalactic Database. In: Results for Large Magellanic Cloud. Retrieved October 29, 2006 .
  6. ↑ G. Pietrzynski, et al .: An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent . In: nature . 495, 2013, pp. 76-79. doi : 10.1038 / nature11878 .
  7. ↑ http://presseservice.pressrelations.de/pressemitteilung/die-genaueste-vermessung-des-universums-aller-zeiten-525131.html
  8. ↑ ESO: Record star far bigger than expected
  9. ^ Graphic from Stars and Space , Edition 5/98
  10. ↑ Marina Koren: The Milky Way Could Crash Into Another Galaxy Billions of Years Earlier Than Predicted. In: The Atlantic. January 5, 2019, accessed January 5, 2019 .
  11. ^ The aftermath of the Great Collision between our Galaxy and the Large Magellanic Cloud. In: Monthly Notices of the Royal Astronomical Society. November 13, 2018, accessed January 5, 2019 .