The Monoceros Mystery
In the constellation of the Unicorn, or Monoceros, astronomers witnessed a spectacular, energetic, stellar outburst from what the British science journal, Nature, has deemed an “extraordinary object” (Bond, et al., 2003, 422:408). The astronomical event also has been described as “peculiar,” “puzzling,” and “mysterious.” The stellar eruption originated from a previously unknown variable star named V838 Monocerotis. At the 202nd meeting of the American Astronomical Society, David Lynch of The Aerospace Corporation declared: “It is the talk of astronomy.” Why has there been such a flurry of activity and astonishment from the astronomical community over this once-unheard-of star?
The reason for the excitement concerning V838 has to do with the fact that it has appeared—and flaunted itself—in such an unconventional manner. For instance, the star’s magnificent eruption suddenly increased its brightness by a factor of 10,000. Researchers exclaimed, “V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way” (422:405). Furthermore, it had increased in size, so that if it were placed within our solar system, the star would engulf everything within (and even including) the orbit of Jupiter. The rapid expansion and sudden increase in luminosity were slightly reminiscent of novae or supernovae explosions. However, as scientists have documented, it failed to exhibit the necessary characteristics to be considered as either option. First, novae-type explosions are cataclysmic events involving the ejection of massive amounts of material, but V838’s outbursts showed tremendous ejection of its outer layers, and only small amounts of circumstellar dust have been found. Second, it lacked the subsequent gravitational core collapse, which produces a central region of extreme density, sometimes seen in the form of a white dwarf star, neutron star, or black hole. Third, rather than have the seething expulsion of matter associated with the nebular stage in a classical novae-type eruption, the temperature within the star actually dropped from around 6000 to 2000 Kelvin, and the outermost part of the shell is now probably somewhere around 800 Kelvin. Using the Broadband Array Spectrograph System (BASS) and the Near Infrared Imaging Spectrograph (NIRIS), The Aerospace Corporation performed a deeper look into the interior of the star. They observed that the molecular content within the star had some very unusual features. Physicist Catherine C. Venturini noted: “There were molecular features everywhere: water (H2O), carbon monoxide (CO), hydroxyl radical (OH), hydrogen sulfide (H2S) and mercapto radical (SH), and aluminum oxide (AlO)” (see “The Strangest Star…,” 2003). V838 has been marked “as different from any known category of stellar outburst” (see “Strange Outburst,” 2003), and Munari and colleagues proposed that this star could be the manifestation of a “new class of astronomical objects” (2002, 389:L56). In their paper, published in Nature, Bond and his colleagues noted that “these characteristics indicate that V838 Mon represents a hitherto unknown type of stellar outburst, for which we have no completely satisfactory physical explanation” (422:405).
With the advent of modern astronomical techniques and technology, astronomers today are able to scan, search, and survey the sky with such detail as no generation prior. With the placement of terrestrial telescopes on our mountains, and the new breed of space telescopes such as the Hubble Space Telescope, we have been privy to a grand collage of stunning pictures and information. And, likewise, discoveries that have boggled our minds have come at an ever-increasing rate, with late-breaking finds being published virtually ad infinitum. Yet, although astronomers have been intensely observing and monitoring V838 since its initial eruption, they are immensely perplexed as to the mechanism behind how such an event could occur. As the scientists themselves concluded, under current stellar evolutionary hypotheses, the incredible display of luminosity, the extremely rapid growth, the unusual outburst behavior, the thermal cooling of the interior, and the diverse molecular components can have no “satisfactory physical explanation.” Thus, stellar evolution can provide no response concerning the “strangest star known” (Britt, 2003).
REFERENCES
Bond, Howard E. et al. (2003), “An Energetic Stellar Outburst Accompanied by Circumstellar Light Echoes,” Nature, 422:405-408, March 27.
Britt, Robert Roy (2003), “Strangest Star Known is the ‘Talk of Astronomy,’” [On-line], URL: http://www.space.com/scienceastronomy/aas202_strangest_030526.html.
Munari, U. et al. (2002), “The Mysterious Eruption of V838 Mon,” Astronomy and Astrophysics, 389:L51-L56, July.
“Strange Outburst,” (2003), [On-line], URL: http://www.nature.com/Physics/Physics.taf?g=&file=/physics/highlights/6930-1.html.
“The Strangest Star We have Ever Observed,” (2003), [On-line], URL: http://www.aero.org/news/current/star-v838.html.
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