Tuesday, November 23, 2010

The reference... VIII

Moribund Records varies greatly with regards to the quality of the bands on the label’s roster, and with individual releases. There are some stellar acts on Moribund Records (Ayat), as well as some absolute turkeys (Satan’s Host). A band that caught my eye, and ear, a couple of years ago is the duo known as Empire Auriga with their debut full-length album Auriga Dying.

Playing a dreamy, droning form of black metal with interesting compositions incorporating industrial and ambient elements, I reviewed the album for Live 4 Metal, and I also interviewed band mastermind Boethius.

Besides the band’s name, there are interesting astronomical references appearing on the two versions of the album’s artwork. Auriga Dying first appeared in a self-released form prior to a formal release from Moribund Records. Both versions of cover art depict different deep sky objects.

First of all, Auriga is a prominent constellation visible from the Northern Hemisphere during late autumn and winter. Below is a Sky Dome chart of the Northern Hemisphere sky as seen in the late evening in mid to late November, and Auriga is very easy to find.

The Charioteer, Auriga contains one of the brightest stars in the sky, Capella, or Alpha Aurigae. Besides being bright, Capella is also a well-studied example of a multiple star system, consisting of two sets of binary stars orbiting a common center of mass. In other words, two pairs, or four total stars, make up the Capella system.

Two other stars of interest, both easily visible to the naked eye, are within Auriga. Beta Tauri (El Nath) is actually shared with the nearby constellation Taurus (see map above), but is otherwise nondescript. Of more interest is the unusual variable star Epsilon Aurigae.

Epsilon Aurigae was first noticed in the 19th century as a very long period variable star. The star is a normal, run of the mill blue white star larger and more luminous than the Sun. However, inexplicably, the star dims by an order of apparent visual magnitude for a couple of years at a time once every approximately 27 years. The history behind the study of this star is a fascinating one, and can be referenced in the October 2009 issue of Astronomy Magazine, which provides a nice summary.

To make a very long story short, the star is actually being eclipsed by an enormous disk of dusty material in orbit about the star. The disk itself has a hole, sort of like a doughnut, that’s been cleared of material by a very tight binary star system. The following graphic from the article summarizes the situation quite nicely.

Essentially, Epsilon Aurigae is a triple star system with two of the stars locked in a tight orbit while surrounded by a dusty disk of material left over from the binary system’s formation. This binary system, in turn, is in orbit around the blue white primary star. A strange, rather unique, and yet beautiful system as the following artist’s conception illustrates.

The first version of the artwork for Auriga Dying appears to be a fictionalized composite of two different, unrelated elements, a globular cluster and wisps of what appears to be reflection nebulae in the foreground.

A globular cluster is a huge agglomeration of stars, all approximately the same age, arranged into a spherical volume a few tens of light years across. The number of stars contained within this relatively small volume is staggering, on the order of several hundred thousand to upwards of a million in some examples. For comparison, the number of stars contained within an equal volume centered on the Sun is only a couple of hundred. We live in a relatively sparse, quiet neighborhood (this is a good thing), but just imagine what the sky would appear as from the outskirts, or from the interior of a globular cluster.

Globular clusters are old systems, dating back to the formation of galaxies. Typically, globular clusters are arranged in a roughly spherical halo surrounding the center of galaxies. Each is orbiting the galaxy’s center. In the case of the Milky Way, there are several tens of globular clusters orbiting the galactic center with orbital radii typically extending to tens of thousands of light years.

The globular cluster depicted on Auriga Dying appears to be a retouched photo of M79, but I’m not certain.

As mentioned, any reflection nebulae would appear in the foreground of such an object, as the nearest globular cluster is over 10,000 light years from the Sun. The constellation of Auriga is relatively sparse with regards to interesting objects, however, and does not contain any globular clusters.

Moribund Records’ release of the album depicts the emission nebula IC 405 within Auriga, on the cover (false color). A relatively dim example of both emission and reflection nebulae, IC 405 is not very noteworthy, or interesting through even a modest telescope, appearing as a dim splotch of nebulosity surrounding the bright young star AE Aurigae.

For you geeks out there, the U.S.S. Auriga is the doomed starship (famously captained by Dan Hedaya) in Alien: Resurrection, and the warlike aliens depicted in the classic Star Trek: TOS episode “Friday’s Child” are referred to as Capellans (it’s not known whether Julie Newmar is a typical female of the species, though).

Apparently, Empire Auriga are gearing up for a new release…

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