Talk:ʻOumuamua

Sentence in lede

"The high eccentricity both inbound and outbound indicates that it is not gravitationally bound to the Solar System and is likely an interstellar object." - shouldn't the comet be on a single conic section orbit (in this case, a hyperbola) in which case there is only one eccentricity, and "both inbound and outbound" is unnecessary? Further, since eccentricity > 1, it is by definition a hyperbolic orbit -> it's already given that the comet is not gravitationally bound to the Solar System. Banedon (talk) 21:24, 26 October 2017 (UTC)

The eccentricity will always be somewhat different inbound and outbound for any object as a result of planetary perturbations. Many comets bound to the Sun will briefly appear slightly hyperbolic either inbound or outbound. So it is useful to state that this object is strongly eccentric both inbound and outbound. This is what makes this object special. The barycentric eccentricity of 17U1 goes from 1.189 (epoch 1900) inbound to 1.193 (epoch 2100) outbound. -- Kheider (talk) 00:09, 27 October 2017 (UTC)

Xenoästeroid

Andy Rivkin has started referring to it as a xenoästeroid https://twitter.com/asrivkin/status/923719587920797696 Agmartin (talk) 17:24, 27 October 2017 (UTC)

I probably prefer rogue asteroid or even manx comet. -- Kheider (talk) 19:43, 27 October 2017 (UTC)

Wrong units?

I believe A/2017 U1 is moving at 44 km/sec which is about 27 miles /sec and not as written in the article. see here for example Golan's mom (talk) 12:32, 29 October 2017 (UTC)

17U1 is moving at numerous speeds depending on when and what you are comparing it to. It was discovered on Oct 19 when it was moving at 46 km/s with respect to the Sun (60 km/s wrt Earth). It was moving 26 km/s wrt the Sun when it was inbound 200 AU from the Sun. It peaked at 87.5 km/s wrt the Sun (68.8 km/s wrt Earth) when passing perihelion on 2017-Sep-09 11:19 UT. As of Oct 29, it is moving 43.6 km/s wrt the Sun. It will continue to slowdown until it reaches an interstellar cruising speed of 26 km/s. Put simply all objects move faster the closer they are to the Sun. -- Kheider (talk) 13:55, 29 October 2017 (UTC)

Flight path

Strange there is nothing about the unexpected flight path here. Is Wikipedia biased? -- 88.112.75.34

There is not much to say as the origin of the object is unknown. Vega was not in the same part of the sky 300000 years ago. It is near the solar apex which is to be expected as more bugs hit a front windshield than a back windshield. -- Kheider (talk) 23:33, 29 October 2017 (UTC)

not necessarily the inner solar system of wherever it hails from

Should "or have been in the inner region of that stellar system long enough for all ice to sublime" be "or have been in the inner region of a stellar system long enough for all ice to sublime". How would we know it sublimed in its source stellar system as opposed to one on the way? ϢereSpielChequers 23:33, 31 October 2017 (UTC)

Good point there. We cann't really know, but I'd reasonably doubt that it happened on the way given how short a time scale that would have to happen on. exoplanetaryscience (talk) 23:36, 31 October 2017 (UTC)

Temporary satellite captures (TSC) are fairly rare and short lived. There is no reason to think 17U1 has spent eons orbiting more than one star as a Short-period comet. Being a short-period comet for 100000+ years is how a comet can become an inactive "Extinct comet". -- Kheider (talk) 02:10, 1 November 2017 (UTC)

Thanks, I suppose that depends on how many stars it has approached and how closely as well of course as how big it actually is (the bigger the object the deeper some volatiles could once have been), presumably speeding up each time via slingshot effect? In any event I don't see how we know that the first solar system it left is the one where it lost all its volatiles. ϢereSpielChequers 10:34, 1 November 2017 (UTC)

Infobox : Perihelion date

I am not familiar with the use of infoboxes. Why is the type 'infobox planet' and not 'comet' used here ? It seems to lack an important information, the perihelion date. This important parameter is only given at present in the text itself. Apparently when using an infobox 'comet', there is a keyword 'last_p' for this information. For A/2017 U1 according to the Minor planet circular quoted in the article, it is : T 2017 Sept. 9.41719 TT , to be rounded to Sept. 9, 2017 I guess to be homogeneous with other wiki pages, cf e.g. Comet_Hale–Bopp . Of course for an hyperbolic orbit 'last' perihelion is a bit strange (as it is the only one) - but that is not incorrect. Tenfeet33 (talk) 14:40, 6 November 2017 (UTC)

Since it is technically classified as an "asteroid" ("A/" as it has shown no cometary activity), we are using Template:Infobox planet. Most known minor planets are confined to the asteroid belt and come to perihelion every 5 years or so. So for minor planets with less than a ~10 year orbital period, the perihelion date is less significant than the opposition date. But I suppose an admin could add it. Perihelion is important for comets because they generally have very eccentric orbits and perihelion is generally when they out-gas the most. -- Kheider (talk) 20:12, 6 November 2017 (UTC)

"1I" ; "A/" ; "C/"

The article should explain the notation. "A/" isn't normal, and "1I" is totally new. "C/" should be explained as cometary notation. "A/" should be explained for comets that turned into asteroids (and not asteroidal notation). "1I" is new, not part of the "#C/" comets or "#P/" comets, so should definitely be explained, since it is a new class of classifications. I assume "I" means interstellar comet, since it looks like cometary notation (ie. "1P/Halley" for the first periodic comet whose periodicity was discovered). -- 70.51.45.76 (talk) 05:49, 7 November 2017 (UTC)

I also believe "A/" has never been used before. A handful of asteroids have been later classified as comets when cometary active is detected. But an "assumed"(?) comet has never been relisted as an asteroid as the MPC generally requires a secondary source to confirm the cometary nature of a newly discovered object. But as I follow asteroids more than comets I might be missing another example of the "A/" notation. "I/" is certainly meant to represent interstellar. -- Kheider (talk) 13:49, 7 November 2017 (UTC)

Light curve

What is the source of the light curve? Agmartin (talk) 16:46, 7 November 2017 (UTC)

Some recent papers

The rotation period and shape of the hyperbolic asteroid A/2017 U1 from its lightcurve

Implications for planetary system formation from interstellar object A/2017 U1

On the Consequences of the Detection of an Interstellar Asteroid

Agmartin (talk) 17:15, 7 November 2017 (UTC)

Correct name is 1I/ʻOumuamua (with ʻOkina), not 1I/'Oumuamua

The cCorrect name is 1I/ʻOumuamua (with ʻOkina), not 1I/'Oumuamua. I asked the Minor Planet Center by e-mail and got a quick answer from Gareth Williams referring to the reference “MPEC 2017-V17: NEW DESIGNATION SCHEME FOR INTERSTELLAR OBJECTS”:

• “The MPECs are an ASCII-only publication and Unicode characters cannot be used. The character in the name is an ʻokina and where a publication cannot represent the character exactly, a near equivalent should be substituted, according to the standards of the publication. This is similar to ASCII representation of cedillas, accents, haceks, etc.”

Thus, the article should in fact be moved to 1I/ʻOumuamua. I tried this, but apparently the destination name is currently blocked. Thus, I propose to perform this move by someone who has sufficient access permissions. -- Karl432 (talk) 22:39, 7 November 2017 (UTC)

We cannot base content on a personal email. It is not verifiable. Since the MPEC gives the official name and it is only ASCII we will have to stick with ASCII until they issue a bulletin with an explanation of the character that should be used. However I have created a redirect. We will see if anyone ever uses that https://tools.wmflabs.org/pageviews/?project=en.wikipedia.org&platform=all-access&agent=user&range=latest-20&pages=1I/%CA%BBOumuamua. Graeme Bartlett (talk) 23:46, 7 November 2017 (UTC)

Actually the supplied bulletin does have the "ʻOkina" character in it. So it is not exclusively ASCII. So I have moved the page to match the name as given in MPEC 2017-V17. Graeme Bartlett (talk) 00:38, 8 November 2017 (UTC)

a couple of sources if someone want add a mention of ʻokina to the article.

Michele Bannister‏ @astrokiwi Replying to @astrokiwi @MinorPlanetCtr Hello, ʻOumuamua! note:' is an apostrophe.ʻ is an ʻokina: a consonant. #A2017U1 https://twitter.com/astrokiwi/status/927686950957481984

Hawaiian words are pronounced just as they are spelled with every letter pronounced, but in this case the name has an ʻokina in front, which is like a glottal stop (I saw one description that it’s like the stop when you say, “uh-oh”). So this is pronounced Oh-oo-moo-ah-moo-ah, with the glottal stop in front http://www.syfy.com/syfywire/an-interstellar-rock-gets-a-name

I wouldn't quote Phil Plait's pronunciation without getting verification from someone that speaks the language.

This, for example, appears to indicate Phils is wrong, note the before and after.

Bob Collom‏ @call_him_bob 22h22 hours ago Replying to @astrokiwi @MinorPlanetCtr Pronunciation guide?

Adrien Coffinet‏ @AdrienCoffinet 19h19 hours ago It corresponds to a glottal stop. Practically, you can consider it as no "liaison" between the sounds before and after the 'okina.

Adrien Coffinet‏ @AdrienCoffinet 19h19 hours ago More or less what happens between the two vowels in “uh-oh” https://twitter.com/AdrienCoffinet/status/928013554543980545 Agmartin (talk) 16:45, 8 November 2017 (UTC)

Audio Pronunciation

Is it possible to get an audio pronunciation for this? This seems like such a minimum requirement, but I have never heard this pronounced. Parsing the phonetic pronunciation just isn't a reasonable expectation for the casual reader.