Talk:2010 TK7

Comments

The article first says 'less energetically costly to reach than the moon, even though they are dozens of times more distant' then 'not likely to be a target for any near future space mission...a spacecraft would require a great deal of additional fuel to match its motion'. I understand the first is talking about Earth Trojans in general and the second is talking about 2010 TK7 (and fuel rather than energy generally), but this could potentially lead to confusion? 81.132.36.245 (talk) 09:06, 29 July 2011 (UTC)

I had the same idea and made a slight change. Please see whether you think it now reads better. JonRichfield (talk) 09:35, 29 July 2011 (UTC)

This suggests an article on the asteroids reachable from Earth, in order of delta-v and desirability. Midgley (talk) 15:54, 20 October 2020 (UTC)

"Spotting an asteroid sharing Earth's orbit is normally difficult from the ground, because their potential locations are generally in the daytime sky"

Huh? The solar elongation of the Lagrangian point is always around 60 degrees, plenty far enough to be at a reasonable eastern or western altitude during astronomical night. And if "[the orbit] is so unusually elongated that it sometimes travels nearly to the opposite side of the Sun from the Earth", then conversely, at other times, the asteroid will therefore be at even greater elongations. Am I missing something here? Old_Wombat (talk) 09:09, 29 July 2011 (UTC)

Well, it's small, and averages an AU away, and we're seeing it from the side so it's not fully lit as it would be at opposition. And while it's at a greater angle from the Sun than Venus, when observing from the ground, it's still not going to be high in the sky between astronomical dusk and dawn.

"The reason it takes so long to see, the reason it has been so long to find one of these things is because, most of the time when we're looking for asteroids or anything else in the solar system, we look out beyond the Earth. We look into the night sky. To find these things that are actually in the same orbit of the Earth, you really have to look in the very early morning or the very, very early evening, as the sky is really quite bright, so no one has found these things up until now." Michael E. Brown http://www.pbs.org/newshour/bb/science/july-dec11/asteroid_07-28.html

—WWoods (talk) 18:32, 29 July 2011 (UTC)

Comets are often discovered when they are around apparent magnitude 19.5. This object never gets brighter than about 20.8. -- Kheider (talk) 18:42, 21 January 2012 (UTC)

Subscripted 7 ?

A recent edit subscripted the 7 in the designation TK7. However none of the first few references that I checked use the subscript. If the subscript is valid, a specific note/reference explaining why would be useful. Mitch Ames (talk) 02:39, 30 July 2011 (UTC)

I dunno about 'useful', but it's technically correct. See Provisional designation in astronomy: "... a subscript number is appended to indicate the number of times that the letters have cycled through. Thus, the 28th asteroid discovered in the second half of March 1950 would be 1950 FC
₁. For technical reasons, such as ASCII limitations, the subscript is sometimes "flattened out", so that this could be written 1950 FC1. ..." Hopefully, it'll get a proper name in short order.

—WWoods (talk) 04:31, 30 July 2011 (UTC)

I couldn't have said it better myself.

We could add "The provisional designation is 2010 TK
₇, meaning it was discovered in the first half of October 2010 (T-> 1st to 15th October), and that it was the 185th object (K->10 + 7*25 = 185) discovered during that time." --Regards, Necessary Evil (talk) 05:41, 30 July 2011 (UTC)

No need to spell out the details in this article if we have a link to the Provisional designation in astronomy - which we now have in See also.

Ideal orbit

I made this change to the lead paragraph:

Trojan objects ideally nominally orbit at a Lagrangian point ...

on the grounds that "ideally" sounded like a POV, but my change was reverted with comment about "ideal" gases. As it happens, I have heard of ideal gases (and the concept of a theoretical vs actual behaviour). However, many of our readers may not have, and we should be writing for them. I still maintain that in the absence of a specific reference to the particular meaning of "ideal" here, that word does not read well. Perhaps we could:

• Add a relevant link. We don't have an ideal orbit article, but perhaps something in orbit or orbital mechanics would be appropriate.

and/or

• Reword the sentence so that it is clear that the word "ideal" does not have it's usual every-day meaning.

Suggestions anybody? Mitch Ames (talk) 04:12, 30 July 2011 (UTC)

Yerrrr... welllll... I was the author of the original "ideal" and I do not apologise for it because I used it in a perfectly correct value-free sense. However, if there is any suggestion, even of mild preference for a similarly useful word in its stead (such indeed, as "nominal"; I, for one, Would not have reverted your edit) then go ahead; you don't need *my* permission after all, and I would not start any edit wars for trivialities.

At the same time, I am a bit nonplussed at your remarks and I agree more closely with Medeis. What I read as your suggestion of something like a definitive norm for the meaning of "ideal" as carrying the suggestion of POV-related perfection would not stand up to analysis. If you have a look at the (disambiguation) entry for "Ideal", you will see that there is a wide range of usages in which "ideal" means something more like "essential" (in the sense of "essence", not as in "necessary"). It might help to reflect that the etymology of "ideal" is cognate with that of "idea". So in fact the "ideal" gas is a concept in which one makes a simplifying abstraction, so that one may neglect such things as molecular volume, van der Waals force etc. :Similarly, one could assume that an ideal Trojan orbit is one in which a body occupies the L4 or L5 point, an abstraction with no nonsense about perturbations or tadpole-shaped oscillations. There is nothing wrong with the idea, but it ignores inconvenient practical considerations, just like in speaking of ideal gases.

So as I said, I am not much fussed about the exact wording in the article, as long as the idea is effectively conveyed, but I don't think that anyone reading an article of that type should be much confused by the idea of "ideal" as "abstract". In such circles that would be very much a "usual every-day meaning", no? In fact, one could have a very similar terminological wrangle about POV and "nominal", don't you think? But if anyone feels strongly about one or the other... JonRichfield (talk) 08:19, 30 July 2011 (UTC)

And amusingly, I see that we now have an elaboration by WolfmanSF, making the whole thing academic, so everyone should now be satisfied. That is one of the strengths of the WP concept IMO. JonRichfield (talk) 08:33, 30 July 2011 (UTC)

In retrospect, "POV" probably wasn't the right term to use in my objection to "ideal". What I meant was that the original wording seemed to imply that the object wasn't where we thought it should be - as if the astronomers got to choose where things go. Whereas the object was just obeying the laws of physics, over which the astronomers get no say. (I'd raise the same objection if someone said "gases would ideally obey PV = NkT. It makes it sound as if the world should follow our physics laws, instead of our physics laws describing the real world as it is. Whereas the "ideal gas" is a actually just a model to help us - not to tell the gas how to behave.) I'm not sure I'm explaining this well, but it doesn't matter - it's been reworded, so the problem has gone away. As JonRichfield says, this is the power of the collective WP mind at work.Mitch Ames (talk) 10:02, 30 July 2011 (UTC)

Etymology

Where is it?Curb Chain (talk) 06:25, 30 July 2011 (UTC)

Does the addition of Provisional designation in astronomy to See also - as discussed in #Subscripted 7 ? above - answer your question? Mitch Ames (talk) 06:45, 30 July 2011 (UTC)

Orbital period

Infobox says orbital period is 365.394 d. Article text (under "Physical and orbital characteristics") says orbital period is "365.389 days, comparable to Earth's 365.256 days". I'm not an expert but guess that a Trojan's orbital period will vary according to where it is in its libration, so at times its period would be less than Earth and at times greater, with a long-term average the same as Earth. Would it be worth adding a comment to this effect, and that the current orbital period is... (whatever the current value is). — Preceding unsigned comment added by Gebjon (talk • contribs) 11:47, 30 July 2011 (UTC)

The mean period must be the same as that of Earth, as is obvious from the general description. If, short-term, it takes longer to go round the Sun, then its short-term average position must be getting nearer. That, and the approximate year of its closest approach, are worth having in the Article. The current "period" is not. 94.30.84.71 (talk) 13:03, 1 August 2011 (UTC)

Statements (such as 365.389 or 365.394) which cannot be perpetually valid should be accompanied by a sufficient indication of when they do or did apply. That applies throughout Wikipedia, and indeed to any form of publication other than speech. 94.30.84.71 (talk) 13:03, 1 August 2011 (UTC)

Trojan objects are most easily conceived as orbiting at a Lagrangian point 60 degrees ahead of or behind a planet or moon in a type of 1:1 orbital resonance

Sorry, but "orbiting at a Lagrangian point 60 degrees ahead of or behind a planet or moon in a type of 1:1 orbital resonance" is NOT what I would call "most easily conceived as" in a encyclopedia aimed for ordinary people.

Hence the 'technical' tag. CapnZapp (talk) 15:25, 30 July 2011 (UTC)

Undid revision 442242740 by 98.118.103.58 (talk) - we don't remove tags just because "it looks bad". Instead, why don't you actually improve the article instead of hiding it's issues under the rug? Thanks, CapnZapp (talk) 13:26, 1 August 2011 (UTC)

What is the problem with the sentence? Have you followed the links to Lagrangian point and orbital resonance, as a reader unfamiliar with the subject matter would be expected to do? Are you saying you don't understand it, or that you imagine that others don't? WolfmanSF (talk) 16:50, 1 August 2011 (UTC)

Partially concur with CapnZapp, the sentence is too complex, containing too many unnecessarily bloated noun clusters. The offending phrases are:

Trojan objects are most easily conceived as orbiting - skip the very unnecessary "most easily conceived as"!

ahead of or behind a planet or moon - too many "or":s making four variants,

in a type of 1:1 orbital resonance - unnecessary "a type of", replace with "an"

the "Trojanness" boils down to:

preceeds or follows a planet with 60° in a stable orbit

"1:1 orbital resonance" or replace planet with large moon and such follows by the logics of the readers mindd. Rursus dixit. (^mbork³!) 10:23, 5 August 2011 (UTC)

I've rearranged and slightly shortened the sentence. However, CapnZapp complained that the article was difficult to understand from a technical, rather than semantic, standpoint. Some of what you describe as being unnecessary is actually of value; without "most easily conceived as", the statement is false; most of the time 2010 TK7 is nowhere near a Lagrangian point. Also, "a type of" serves to alert the interested reader to the fact that there are a number of types of 1:1 orbital resonance. WolfmanSF (talk) 03:33, 6 August 2011 (UTC)

Useful Media

The discoverers page here has some useful media on it.

Particularly the video simulated from a non-rotating frame of reference. (linked in the purple section just below the video clips section)

I am unsure of the copyright status of the images/videos on this page (The page itself is copyrighted though). Though it is likely they are free to use as NASA image we already use is a modified version of an image here (Obviously this should be confirmed first).

A simple way to visualise this orbit for ordinary people would be to modify the non-rotating frame of reference video to also trace out the orbital path of the asteroid (leaving in the current tracing so people can make the connection). It would then be seen to clearly orbit the sun in a relatively close to 1:1 resonance with Earth, not orbit a spot in space in front of Earth.

Nbound (talk) 00:31, 31 July 2011 (UTC)

ahead of us or behind us?

Does this asteroid precede or follow the earth in its orbit? The article doesn't seem to say. I think that should be there. Michael Hardy (talk) 02:16, 1 August 2011 (UTC)

I agree. — Preceding unsigned comment added by 146.95.126.178 (talk) 13:29, 1 August 2011 (UTC)

Check out sentence 6 of the article. WolfmanSF (talk) 16:41, 1 August 2011 (UTC)

Gravitational and centrifugal forces balance??

(where gravitational and centrifugal forces balance).

Implying that the object moves in a straight line without acceleration? Obviously incorrect. Can someone with a better knowledge of Classical Mechanics propose a better phrasing? — Preceding unsigned comment added by 130.238.196.72 (talk) 15:02, 16 January 2012 (UTC)

2014-Jan-16

At 2014-Jan-16 03:51UT 2010 TK7 became an Aten with a semi-major axis (a) of less than 1AU. (Just making note of it.) -- Kheider (talk) 15:39, 27 February 2014 (UTC)

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How come Venus doesn't capture or perturb it?

Since it gets much closer to Venus' orbit at times. — Preceding unsigned comment added by 2A02:A457:9497:1:986F:F8D1:9ECB:16E7 (talk) 00:48, 14 January 2020 (UTC)

The Earth-MOID (Minimum Orbit Intersection Distance) of 0.08 AU is smaller than the Venus MOID of 0.11 AU. The asteroid is moving too quickly for Venus capture. Earth only shepherds it with help from the Sun. -- Kheider (talk) 18:34, 20 October 2020 (UTC)

Orbital Speed

The article's listed orbital speed for asteroid 2010 TK-7 is 9.1 km/sec which is about one third of Earth's orbital speed. How could that be? Is the listed 9.1 km/sec actually the variation in its orbital speed? 2603:7081:1F07:9753:31B0:6719:33AA:9812 (talk) 14:05, 13 October 2022 (UTC)

Ouch! Good catch with an orbit similar to Earth it would have a similar orbital speed of 29.8 km/s wrt to the Sun. At perihelion it would be around 36 km/s and at aphelion around 24 km/s. -- Kheider (talk) 15:13, 13 October 2022 (UTC)