Talk:9 Metis

From Wikipedia, the free encyclopedia

WikiProject Solar System
Solar System Portal

This article is within the scope of the Solar System WikiProject, a collaborative effort to improve Wikipedia's coverage of the Solar System.
B This article has been rated as B-Class on the assessment scale.

Contents

[edit] Greek

Some variation in the Greek forms, genitive Mêtios or Mêtidos. However, the former is the more productive root, so we might expect the English adj. form to be (an unattested) Metian. kwami 2005 July 6 07:50 (UTC)

Following the pattern of ophis produces ophidian, this would make the alternative adjective Metidian? --Sturmde 05:11, 3 November 2005 (UTC)

Correct. kwami 05:21, 3 November 2005 (UTC)

[edit] Only one discovered in Ireland?

Is it really the only asteroid ever discovered from Ireland? Out of all the 200,000 or so? Deuar 12:24, 18 February 2006 (UTC)

[edit] Dimensions

As usual, there is a range of size determinations, which is kind of hard to collect together to something coherent:

  • Thermal measurements (MSX data) gave a mean diameter of 155±4 km.
  • Hubble images gave 235×165 km (Icarus Vol. 137 p. 260) and 222×182 km (Icarus Vol. 173, p. 409).
  • The most recent lightcurve analysis [1] gives axis (a×b×c) ratios a/b=1.2 and b/c=1.4, along with a shape model which agrees qualitatively with the Hubble images. This is also in general agreement with earlier analyses [2].
  • Occulations [3] gave >141 km, 190 km, 174 km, and 157×132 km.

In the end, in the article, i've used the largest Hubble diameter as the long axis "a", and obtained the other axes from the lightcurve ratios to get about 235×195×140 km. This agrees fairly well with the Hubble observations. There are some issues with this, however: the "mean volume" diameter is then 186 km, much more than the thermal measurement. This can be properly reconciled with the thermal estimate only if that was made when the asteroid was oriented so as to hide the long axis. Well, it's possible, I suppose, and has even been suggested in the Hubble observations reference (Icarus Vol. 173, p. 409). Deuar 20:43, 19 February 2006 (UTC)

[edit] Albedo

I've taken the liberty to change the albedo to the value calculated from infra-red spectra (MSX in this case) for compatibility with the majority of asteroid articles. Of course, there's a different albedo for every wavelength (hey, maybe we could try to explicitly standardise which one to use in the template or in standard asteroid physical characteristics some day!), but the values obtained from thermal fits to infra-red spectra look like a good practical standard to quote for two reasons:

  • They are known for huge numbers of asteroids, and give a good relative comparison
  • They have been fitted from the thermal spectrum of the asteroid, which implies that
    • they are related to physical properties of interest to a non-specialist (temperature).
    • its roughly an average albedo over the bulk of solar radiation, which is produced by the Sun overwhelmingly around visible wavelengths. (Despite using infra-red intensities, the albedos quoted are estimates of the proportion of solar radiation reflected from the body. The estimate is based on the temperature of the body that is implied by the measured infra-red spectrum).

(IMHO) Deuar 21:19, 19 February 2006 (UTC)