User talk:Kheider
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[edit] Data source
If you just joined, welcome to Wikipedia!
I’ve noticed that you’re changing diameters in many TNO articles. If you’re updating the data, please consider the following:
- Always provide the source (published scientific article)
- Do not use Internet sites other than directly related with a recognised astronomical institution (they provide the sources: published papers)
- Avoid changing the values with one sigma error e.g. 800 km ± 50 by a single figure 853. With no error margin the figure is meaningless.
- Finally, if you’re a johnstonarchive fan, use the references from this page: [1] and not unreferenced figures.
Otherwise, a well-meant update actually ruins the work of many editors and will ultimately be reverted as unreferenced. Eurocommuter 06:47, 5 September 2006 (UTC)
[edit] Ceres
Ceres is not considered as an asteroid and is considered as a Small Solar System Body. -- Deenoe 14 October 2006 (UTC)
There has been NO OFFICIAL STATEMENT from the IAU committee removing (1) Ceres as an asteroid. A poorly worded Q&A article that says Ceres both 'IS and WAS' is NOT a good official statement.
Using the IAU 2006 definitions an object is either a Planet, 'Dwarf Planet' (compound noun), or a Small Solar System Body (SSSB). This does not affect the definition of the older terms asteroids and comets.
Pluto is a Kuiper Belt Object (KBO) even though it is also a 'dwarf planet'. I believe that 1 Ceres will still considered an Asteroid since it orbits in the asteroid belt and has the same origin as the other asteroids.
Has Pallas become the 1st asteroid discovered? Has Vesta become the largest asteroid (at least until the IAU decides that since Vesta is a damaged, differentiated protoplanet that it was probably a healthy dwarf planet in the past)? *IF* Ceres is truly no longer an asteroid, because it is spherical, then those two very basic questions have new answers.
2 Pallas is similar to 4 Vesta in volume, but significantly less massive. If the IAU ever reclassifies Vesta as a dwarf planet AND officially declares that dwarf planets are not asteroids, then Pallas may someday be considered the largest asteroid. -- Kheider 23:33, 17 October 2006 (UTC)
[edit] Concerning your edits on Talk:List of solar system objects by mass
Please do not edit other comments, unless merely formatting a conversation to become more readable (e.g. by inserting proper indentations). Otherwise, such edits are unnecessary and could be considered to corrupting the original context. Thank you. --Iamunknown 18:43, 18 October 2006 (UTC)
Under "Spheroid or not?", I added a link to Neptune's moon Proteus. Proteus is one of the largest non-spheroids in the solar system. Your re-edit (rv) moved the link from the moon to Greek mythology ;-) Kheider 19:01, 18 October 2006 (UTC)
- You removed the link again. Please consider, if doing anything, disambiguating the link. There is an article about the Neptunian moon Proteus (moon). You could have replaced [[Proteus]] with [[Proteus (moon)|Proteus]]. I am restoring the link with the pipe-link disambiguation Proteus (moon). --Iamunknown 16:58, 19 October 2006 (UTC)
Since I have only been using Wiki for 1 month, I did not known how to get Wiki to link to the wiki copy of the "(moon) Proteus". The original link to Greek mythology would not help anyone trying to study spheroids. Thank you for making Proteus point to something relevant to the discussion. Kheider 18:21, 19 October 2006 (UTC)
- I didn't realize that you are relatively new here. Please let me formally welcome you to Wikipedia! Here are some pages that you might find helpful:
- I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (~~~~); this will automatically produce your name and the date. If you need help, check out Wikipedia:Questions, ask me on my talk page, or place
{{helpme}}on your talk page and someone will show up shortly to answer your questions. Again, welcome! --Iamunknown 19:13, 19 October 2006 (UTC)
[edit] Occulation Chords
An occulation chord is the width of an asteroid along a particular line, as inferred from stellar occulation. This is not the same as a solar eclipse: no asteroid can be observed to transit the Sun (particularly since most are further from the Sun than the Earth). The process works like this: we can predict roughly where an asteroid will pass in front a star, as seen from some part of the surface of the Earth. We then place a large number of telescopes across this region, with known positions, and measure the brightness of the star + the asteroid as a function of time. We see a drop when the asteroid passes in front of the star, and a jump when the star becomes visible again. The time of these events tells us the extent of the asteroid along a line defined by its projected velocity, a single chord. Taking many telescopes, we can construct an occulation silhouette. This process is very laborous and prone to difficulty, but was the only way to get asteroid dimensions with any accuracy until the advent of radar astronomy, adaptive optics, and spacecraft observations.
- So an occulation chord passing through the equator of the asteroid is equal to the diameter of the asteroid? Does it matter that the Earth is only passing through the penumbra? Kheider 20:04, 20 October 2006 (UTC)
There is no penumbra in an asteroid occulation, because the asteroid's angular size is far larger than the angular size of the star (an asteroid may subtend an angle of a tenth of an arcsecond, while stars have angular sizes in the milliarcsecond range). The penumbra in a solar or lunar eclipse is caused by diffraction (which is neglible for an object with no atmosphere) and by partial shadowing, which doesn't apply here. An occulation chord passing through the equator is not the same as the diameter, because the diameter of an irregular asteroid is ill-defined. The occulation chords given the plane-of-sky silhouette, and nothing else. Michaelbusch 22:14, 20 October 2006 (UTC)
[edit] Linking
When linking an image, template, or category without adding it to the article, use a leading : For example: [[:Category:Binary_asteroids|Category:Binary_asteroids]] Rmhermen 16:24, 28 October 2006 (UTC)
[edit] Moderately Red Spectral class
- When a KBO's spectral class is called '(moderately red)' what does that mean? Does that mean it does not reflect well in the visible light but reflects better in the infrared? Or does it mean that object is reddish in color? 50000 Quaoar, 20000 Varuna, and 28978 Ixion are all listed as such. 38628 Huya says, "appears to be dark red, suggesting it is covered with ancient organic chemistry." Thanks -- Kheider 01:42, 2 November 2006 (UTC)
'Red' in this context means that the object is relatively more reflective in the red and near-infrared than in the blue (the reflectance spectrum slopes upward toward red). Such spectra on outer solar system objects are often caused by organic compounds, such as tholins. However, to the unaided eye these objects would be brownish or black, because of their low albedos. Michaelbusch 01:49, 2 November 2006 (UTC)
- So on the plot TNO Colors I assume that both 1994 ES2 and (119070) 2001 KP77 would be red? -- Kheider 23:15, 2 November 2006
Yes. Redder objects have higher V-R and B-V. On this plot, (0,0) is equal magnitude in all three bands. This is not quite the same as a perfectly white, because the bands are broad, but a white object would be at (0,0). A blue object would plot at negative B-V and negative V-R. Michaelbusch 23:19, 2 November 2006 (UTC)
- So would 1994 ES2 be redder than (119070) 2001 KP77? -- Kheider 23:48, 2 November 2006 (UTC)
Not necessarily. 1994 ES2 has higher V-R, but much lower B-V. This means that ES2 has relatively more blue in its spectrum as compared to KP77. So if we looked only between V & R, ES2 would be more red, but if we looked only between B & V, KP77 would be redder. This simply is a problem with the definition of redness. Michaelbusch 23:56, 2 November 2006 (UTC)
