September 19, 2018

Astro-Challenge:The Magellanic Clouds.

Ah…the southern hemisphere has all the good stuff. As we here at Astroguyz dip below the equator for the fifth time on a trip to Ecuador, we thought we’d include an old friend and a unique celestial pairing that most people have never seen. The Magellanic clouds are actually small satellite galaxies of our own Milky Way; the Large Magellanic cloud (LMC) is at a distance of 160,000 light years and contains about 10 billion stars, while the Small Magellanic cloud (SMC) is at a distance of 200,000 light years and weighs in at 7 billion solar masses.

Both were first noted by Magellan on his world spanning voyage, and the name stuck. Unfortunately, these are deep in the southern skies at about -75 degrees south, and you really have to be at a declination of +5 north or lower to really see them! I first saw the LMC and SMC during my first journey below the equator in 1994 to Mombasa, Kenya; My best views came during a trip to New Zealand in 1998. The SMC and LMC are good binocular targets and may be visible to the naked eye as faint, cloud-like patches; The LMC and SMC are about 21 degrees apart in the sky and in December transit the meridian at about 9 PM local. I plan to bring my 15×45 binocs to scan the southern skies…expect some posts on the trip to come!

The term of the week is irregular galaxy…an irregular is a type of galaxy that doesn’t exhibit a definite spiral or elliptical structure. Both the SMC and the LMC exhibit such irregularity. The structure appears chaotic, without a distinct central nucleus or bulge. The Milky Way has 12 known satellite galaxies total, and there is some controversy as to whether the LMC and SMC and gravitationally bound to our own galaxy or not. In fact, there is also some controversy that these dwarf are not true irregulars, as they exhibit a vague barred structure! Ah, the convoluted world of evolving classifications… its been suggested that a fourth type of barred spiral galaxy might be required, that of a barred Magellanic spiral.

 

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