|Discovered by||Franz Kaiser|
|Discovery date||December 22, 1913|
|Minor planet category||Asteroid|
|Epoch August 18, 2005 (JDCT 2453600.5)|
773 Irmintraud is a minor planet that orbits the Sun between the planets Mars and Jupiter. Discovered by German astronomer Franz Kaiser at Heidelberg, Germany, on December 22, 1913, the planetoid was named for Irmtraud, an old German woman's name that appears frequently in old songs and sagas. This D-type asteroid's previous designation was 1913 TV. The 773 Irmintraud asteroid is a likely source of the Tagish Lake meteorite which landed in Canada on January 18, 2000.
In 1992, Larry A. Lebofsky and colleagues published an article in which they noted that "unaltered asteroids are thought to represent the raw materials available for terrestrial planet formation and so are important to our understanding of the origin and evolution of the Solar System." Since at least 1980, it was believed that D-type asteroids were unaltered asteroids, ultraprimitive in composition and composed largely of hydrated silicates and organic material. However, in analyzing the spectra of 773 Irmintraud for the water of hydration band (the 3-µm absorption feature of hydrated silicates), Lebofsky discovered the first D-type asteroid to show the water of hydration band on the surface of the asteroid. Lebofsky concluded that 773 Irmintraud had undergone an alteration process typically seen C-type asteroid, making 773 Irmintraud and perhaps other D-type asteroids less likely to represent the raw materials available for terrestrial planet formation. In addition, the discovery of water of hydration band on 773 Irmintraud meant that there may be major differences in mineralogy within individual type classification and astronomers must be careful in assuming that the C-, D-, and other type classification relate directly to mineralogy.
In 1997, NASA added 773 Irmintraud and eventually over one million other names to a microchip placed on board the Stardust spacecraft that launched February 7, 1999. Placing the names onto the Stardust spacecraft was a public outreach effort. In particular, this served to promote public interest, awareness and support of the space program.
In September 2001, there was speculation that Tagish Lake meteorite which struck in British Columbia, Canada on January 18, 2000, was derived from a D-type asteroid, since the spectral shape and brightness of the meteorite was similar to D-type asteroids. Of the three studied, the 0.032 IRAS albedos (8) of 368 Haidea and the 0.033 IRAS albedos (8) of 773 Irmintraud are both considered close to the reflectance of the Tagish Lake meteorite. Moreover, even though 368 Haidea was closest spectrally to the Tagish Lake meteorite, 773 Irmintraud was no more than 0.034 AU to a chaotic zone associated with one of the Kirkwood gaps due to the mean motion resonance with Jupiter. This made 773 Irmintraud the closest of the three candidates to the associated chaotic zone and thus the most likely of the three as the source of the 2000 Earth impacted meteorite.
The idea that humans held a piece of the asteroid 773 Irmintraud spurred others to act. In 2002, the University of Tokyo performed near-infrared photometric and spectroscopic observations of 773. In addition, the University obtained an accurate lightcurve in Japan through visible photometry and ultimately found a gap between K- and L- band spectra. From this, the university concluded that results support the idea that Tagish Lake meteorite has a link with D-type asteroids.
- NASA (12 Jun 2008) Plantary Data System. Accessed June 12, 2008.
- Schmadel, Lutz D. (2003) Dictionary of Minor Planet Names. Page 73. Publisher: Springer. ISBN 3-540-00238-3
- Warner, Brian D. (2006) The Minor Planet Observer and the Palmer Divide Observatory 773 Irmintraud.
- Hiroi, Takahiro, et al. (September 21, 2001) Science The Tagish Lake Meteorite: A Possible Sample from a D-Type Asteroid. Volume 293; Issue 5538; Page 2234.
- Lebofsky, Larry A. (1992) NASA Technical Reports Server. An Infrared Reflectance Study of Low Albedo Surface Constituents. N92-10830.
- NASA (July 16, 2001) Microchip Names (I). Accessed June 12, 2008.
- Ai, Kanno. (2002) Astronomical Herald Photometric and Near-IR Spectroscopic observations of a D-type asteroid, (773) Irmintraud, by SUBARU/IRCS. VOL.95; NO.11; PAGE.507-514. Accession number: 02A0834926; Japanese language Journal Code: F0543A; ISSN 0374-2466
- Preston, Steve. (May 19, 2007) asteroidoccultation.com (773) Irmintraud / TYC 4908-00263-1 event on 2007 May 22, 06:07 UT Accessed June 11, 2008.