Simple about the complex: the Small Magellanic Cloud

(ORDO NEWS) — The Small Magellanic Cloud (LMC) is a small irregularly shaped dwarf galaxy, which in many sources appears as a satellite galaxy of the Milky Way . If the dwarfism of the MMO is not disputed, as is the case with the Large Magellanic Cloud (LMC), then the status of a satellite of the Milky Way is in serious doubt.

Since the MMO is moving through space at a speed of 217 km/sec relative to the galactocentric rest frame, most researchers are of the opinion that the MMO is moving too fast to be gravitationally bound to the Milky Way.

It is worth noting that the calculations that determine the total cosmic velocity of the MMO took into account that the MMO and LMO are gravitationally bound and revolve around each other at a distance of 75,000 light years, and that their common center of mass revolves around the Milky Way.

Small Magellanic Cloud: quick facts

  • Constellation: Toucan/Hydra;
  • Distance to Earth : 200,000 light years;
  • Mass: 6.5-7 billion solar masses ;
  • Object type: dwarf irregular galaxy;
  • Diameter: 7000 light years;
  • Other names: NGC 292, PGC 3085, Nubecula Minor.

Like the LMC, the MMO is best seen from the Southern Celestial Hemisphere, but due to its low surface brightness, the galaxy is best viewed within the city limits, away from artificial light pollution.

Notable Features

Many observers report that the IMO looks like part of the Milky Way that has separated from the Galaxy. In addition, several eminent astrophysicists (D.S. Mathewson, V.L. Ford and N. Viswanathan) hypothesized that once the IMO and LMC collided, and this led to the “break” of the first galaxy into two parts.

According to this hypothesis, the smaller “piece” that separated from the IMO, as it were, “stuck” between the larger piece and the Milky Way. Although researchers have named the smaller part of the IMO the “Mini Magellanic Cloud,” there is as yet no conclusive evidence that the IMO was actually split in two.

Physical properties

The IMO has a central bar that most researchers believe has become quite disorganized due to continuous tidal interactions with both the Milky Way and the more massive LMC.

Simple about the complex the Small Magellanic Cloud 2

It is worth noting that some questions remain regarding the irregular shape of the IMO:

  • Some researchers believe that the total spatial velocities of both the IMC and the LMC suggest that both galaxies, passing near the Milky Way, are gradually being destroyed by tidal forces. If this is true, then MMOs and LMOs are not true satellites of our Galaxy and will one day be swallowed up;
  • Other researchers are convinced that the two dwarf galaxies are as close to the Milky Way as possible due to the relative positions they occupy during their current rotation relative to each other. If so, then the Milky Way is not destroying galaxies, and the irregular shape is a temporary effect.

X-ray radiation

As with the MMO, during the initial X-ray studies conducted in 1966, no X-rays were found in the MMO beyond normal environmental levels. However, subsequent studies have revealed a large number of fairly powerful X-ray sources. For example, a large number of bright X-ray binaries have been found in the MMO and recent bursts of star formation have been recorded, responsible for the appearance of a large population of both “ordinary” massive stars and massive X-ray binaries.

Star formation

Recent studies of the history of star formation in IMO suggest that its first stars were born as early as 12 billion years ago, although this process was relatively slow. Interestingly, a radial change in the content of “metals” (elements heavier than hydrogen and helium) was also revealed, or, in other words, the central regions of the MMO are more rich in metals than the regions outside.

Simple about the complex the Small Magellanic Cloud 3

Moreover, detailed analysis also showed that although the rate of star formation was relatively slow in the distant past, it nevertheless did not slow down until a period that began 2-3 billion years ago. However, about 500 million years ago, the rate of star formation increased markedly and remained stable. About 100 million years ago, the rate of star formation increased again.

In general, all studies indicate that about 50% of all stars ever formed in the IMO are at least 8.4 billion years old. Since then, the rate of star formation has remained fairly constant, but the several bursts of star formation discussed above seem to indicate that tidal interaction with the Milky Way is responsible.


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