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)

[edit] Planet visual magnitudes

Hi Kheider, I wonder if we could compare our methods of obtaining the range of magnitudes. While entering angular size values for the planets in their infoboxes, I noticed that the reference I was using (e.g. this one for Saturn) also gave peak magnitudes. The values I obtain based on this (how , I will explain below) differ somewhat from the ranges you put in a few days ago. It'd be good to sort these numbers out.

So, for example, for Saturn, that nasa fact sheet gives:

Apparent diameter from Earth
       Maximum (seconds of arc)   20.1
       Minimum (seconds of arc)   14.5
Maximum apparent visual magnitude             0.43

Obviously the maximum magnitude I use is right there. To get the minimum, I assume that the brightness maximum must occur at the same time as the given maximum apparent diameter, and that the minimum brightness must occur simultaneously with the minimum apparent diameter. (This is inapplicable to Venus and Mercury, since they are not in full phase at their closest approach to Earth). This consideration gives a minimum intensity that is (14.5/20.1)^2=0.520 times the maximum, assuming a circular orbit for Saturn, therefore a magnitude change of 0.709, hence a minimum magnitude of 0.43+0.71=1.14. I notice that you obtained a significantly darker minimum magnitude of 1.4, and am wondering at how that comes about. Deuar 15:18, 12 October 2007 (UTC)

Hi Deuar. I used "A Field Guide to the Stars and Planets" (Pasachoff, 1983) for some of the values, and I used JPL Horizons to confirm the values.

You are right there is deviation based on the source and probably the methods used. I do agree that maximum apparent diameter is important, but keep in mind that the "Sun-Target-Observer angle" (target's apparent PHASE ANGLE as seen at observer's location) might affect magnitude. Some of NASA's own sources conflict one another. :-)

NASA Reference Publication 1349 lists Mercury as high as -2.3 (full phase) on May 19 2006. I went with -1.9
Different sources list values of -4.7 and -4.6 for Venus.
I have confirmed Mars (using Horizons) at 2.88 on 2003-Aug-29: You will need to set the "Target Body" as (4) MB:Mars, the date range to cover 2003, and include the QUANTITIES: 9 (vis mag) and 20 (range AU).
I can not get Jupiter's brightest magnitude greater than Mars's maximum in our lifetime.
I have heard (can not remember the source it was years ago), that when tilted at their maximum of 27 degrees, such as in 1988, that the rings increase Saturn's brightness by 0.2 to .7(?) magnitude. The book "A Field Guide to the Stars and Planets", does list Saturn at +0.2 opposition magnitude for 1985 through 1989. In 1984 with the rings only tilted 20 degrees Saturn is listed at +0.3. NASA Reference Publication 1349 lists Saturn at -0.2 (yes, that is a minus) on Jan 2 2004! The +1.47 (Horizons) value for Saturn on 2017-Oct-23 probably does not account for the rings either.

Numbers I used (vs generated with Horizons)
Mercury -1.9 2051-Jun-04 -2.20 (brightest when full)
Venus -4.6 1989-Dec-18 -4.57 (brightest when cresent)
Mars -2.9 2003-Aug-29 -2.88; 2021-Jul-11 1.84
Jupiter -2.8 2010-Sep-20 -2.79
Saturn -0.24 1973-Dec-23 0.42; 2017-Oct-23 1.47 (error since rings tilted a lot!?) (Pic)
Uranus 5.5 2048-Feb-25 5.31; 2008-Feb-26 5.95
Neptune 7.7 2032-Oct-07 7.80; 1973-Dec-04 8.02
Kheider 19:28, 12 October 2007 (UTC)

Yep, it's complicated. Albedo can vary with phase angle and orbital location (e.g. Pluto, Mars, Uranus?) as well. However, i would suppose that the phase angle wouldn't affect the min/max values for the planets external to Earth, since both cases should occur when we view the full face at opposition, or just next to the Sun. This might be a different matter for inclined objects like Pluto or asteroids, though. There's also a matter of which face we're viewing, or the rings of Saturn. Those rings could account for the discrepancy at the minimum magnitude we see if the maximum value given in my fact sheet took them into account (as was probably the case). Pity the fact sheets I know don't explain how the values were obtained! Anyway, I see that you've gone into lots of detail in your investigation, so I'm happy to trust your judgment :) Incidentally, how did you get Horizons to give you magnitudes? I briefly tried looking for a magnitude-related field there, but couldn't find it. Deuar 22:05, 12 October 2007 (UTC)

Go to Horizons. Make sure it is set to Ephemeris: OBSERVER. Go to "Table Settings" (2nd from the bottom) and click on the blue "change". Make sure that "9. Vis mag. & Surf Brt" has a check mark next to it.  :-) Kheider 22:37, 12 October 2007 (UTC)

Thanks, I see I was using the wrong Ephemeris type (elements). So, comparing the Horizons magnitude to that given in your new reference, there is a 0.3 difference in brightness (dimmer in Horizons), which is presumably due to the rings. In Horizons they mention that they don't take into account the illumination angle of the rings, but this is ambiguous - are the rings taken into account or not overall? what about viewing angle? etc. It looks like a mess, and any own calculations are bound to be bordering on original research due to the complexity of the thing. :( Well found reference, then! :) Deuar 13:20, 13 October 2007 (UTC)

It does not appear as if Horizons or the NASA Fact Sheet consider Saturn's ring system. I have updated Saturn to magnitude -0.24 for the 2000-12-08 opposition at ring tilt 24° / solar phase angle 0.038. I wonder how bright Saturn was at opposition in 2002-12-17 when it was at ring tilt 26.5° / solar phase angle 0.027? This abstract does not seem to publicly show it.
-- Kheider 23:59, 14 October 2007 (UTC)

Saturn Calculate: magnitude, ring tilt, diagram with rings, S&T moons

Mercury/Venus Calculate: Phase

[edit] Updating 2007 WD5

If you can reasonably prove that the data sources are reliable and accurate, you should just go ahead and make the changes. —Viriditas | Talk 04:59, 24 December 2007 (UTC)

[edit] DYK

Updated DYK query On 27 December 2007, Did you know? was updated with a fact from the article 2007 WD5, which you created or substantially expanded. If you know of another interesting fact from a recently created article, then please suggest it on the Did you know? talk page.

--Maxim(talk) 14:40, 27 December 2007 (UTC)

[edit] ref for 2007 WD5

Could you take a look at this edit - the reference is broken. --mikeu (talk) 19:24, 27 January 2008 (UTC)

Thank you for the heads-up. I moved the "Horizons1223" citation details to top ref to prevent the ref error that did not exist on 21:35, 3 January 2008. Perhaps citation details should not be placed in external link sections. -- Kheider (talk) 20:14, 27 January 2008 (UTC)

[edit] Sedna

It might or might not be unlikely, who knows if the astronomical community wants to enlist another planet? I know I'm for it. Besides, Mercury's probably tired of being the littlest! Secondly, size isn't -currently- use to decide which objects get to be "Planets". Thirdly, Eris doesn't cross Sedna's orbit, check the latest version of Celestia if you don't believe me.

Mass (which is Volume*Density aka size) is used to determine if an object can be orbitally dominant. And a lot of the above statements do not comply with NPOV policies. -- Kheider (talk) 22:51, 16 February 2008 (UTC)

They don't. I admitted it, but neither is your insistence that Sedna can't be a planet. And as I'd type before, there's only three standards by which a 'planet' is a 'planet,' and "orbital dominance" (except in the case of planets with moons) is not one of them, especially if we're talking about unknown Solar System bodies. You can type until you have carpal-tunnel, but the rules won't be changing until next year. -- IdLoveOne (talk) 02:10, 17 February 2008 (UTC)

I suggest you read Steve Soter's article at http://arxiv.org/abs/astro-ph/0608359v6 This is what a lot of people suggest going by. Clearing the neighborhood requires orbital dominance. Moons do not effect orbital dominance since they are submissive to a Planet by definition. -- Kheider (talk) 13:06, 17 February 2008 (UTC)
There are no "cleared neighborhoods," every solar system body from Mercury and beyond has something that imposes on it's orbit. What about the centaur Chariklo, it's all alone in it's orbit & probably just out of the reaches of Saturn and Uranus. If it's found to have hydrostic equilibrium, I say it's fair game for planet status. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Chariklo;orb=1;view=Far -- IdLoveOne (talk) 00:27, 21 February 2008 (UTC)

Chariklo will probably look a lot like Phoebe or Hyperion. There are many known Centaurs and their orbit are unstable over a million years as they are perturbed by the dominant gas giants. Some of these centaurs will become future comets. -- Kheider (talk) 01:42, 21 February 2008 (UTC)

[edit] Barnstar

The E=mc² Barnstar
For helping get Neptune to FA, and for coining the phrase "a lot of inbred rocks", to which I chortled heartily, I award you the science barnstar. :-) Serendipodous 12:46, 14 March 2008 (UTC)

[edit] Cite to abstract or paper

Hey mate, about your change to go to the abstract. I understand citing the abstract as it is na HTML and not PDF, but can I still cite the pages where that info appears, even if citing the abstract? Samuel Sol (talk) 15:17, 17 March 2008 (UTC)

[edit] You're welcome

And sorry to hear about your loss. :-( I know how difficult these times can be, and wish you all the best. Serendipodous 07:12, 3 April 2008 (UTC)

Thanks :) Though my knees are OK now; mainly it's my ribs that are killing me... Serendipodous 18:29, 20 April 2008 (UTC)

[edit] 1995 GJ

You wrote that 1995 GJ is cubewano. But on Minor Planet Ephemeris Service you can find that the object was observed only on two days 1995 Apr. 3-4, and eccentricity is assumed. So, it may be SDO as well as cubewano. Excuse my English. Regards, Chesnok (talk) 08:38, 22 May 2008 (UTC)

That was one of the first articles that I wrote. I just updated it some. I know that the JPL Small-Body Database Browser lists it as a Cubewano. But I am not sure how official that is given that it was only observed over two nights and is considered lost. Should we use that as the reference? -- Kheider (talk) 16:25, 22 May 2008 (UTC)

[edit] FAR for Mercury (planet)

FYI. Thanks again for all of your help on this project. UltraExactZZ Claims ~ Evidence 02:10, 7 June 2008 (UTC)