Talk:Potentially hazardous object

Unprecedented

I'll leave this with the folks who have done all the work on this article. The use of "unprecedented" in the second paragraph does not make sense.

This is big enough to cause unprecedented regional devastation... once per 10,000 years

I would suggest simply removing the word would be better than trying to dress up the statement with unnecessary adjectives. Kid Bugs (talk) 19:35, 2 January 2010 (UTC)

Actually, that is the official wording used to describe a Torino scale 9 object, which is the closest to the definition of a minimum size PHA on that scale. Although, a Torino scale 8 would seem to be pretty hazardous to me as well, and would have probably included the Tunguska event object and the Arizona crater object. I guess what is meant is that the disaster would be greater than any in recorded history. Just deleting the adjective would fail to impart the significance of the event. The only thing really wrong here is that there is no recognition in the article that that description has been "lifted" from Torino. SpinningSpark 22:48, 2 January 2010 (UTC)

The issue is that, without going to look at the Torino article, a reader does not necessarily infer that the "regional devastation" refers to human construction/human lives. It could also be referring more generally to geological disruption, which is obviously not unprecedented. In addition I think the "once per 10,000 years or less" is ambiguous, because "or less" could mean, 'less frequently than that', or, it could mean 'or less years' (meaning, more frequently). To try to resolve ambiguities I have edited the sentence. --Leperflesh (talk) 21:12, 18 May 2011 (UTC)

Since the "historical" period of human civilization is less than 10,000 years, and no such event (whether recorded, or not) is known to have occured since civilization was invented, then such an event is without historical precedent, hence unprecedented. Such events certainly occured in the pre-civilization era.Eregli bob (talk) 23:38, 7 September 2012 (UTC)

Decap

Should be moved to Potentially hazardous object, without the capitals. Rothorpe (talk) 20:33, 16 September 2010 (UTC)

how often

Such impact events occur on average once per 10,000 years or less.

Less than 1e4 years, or less than once per 1e4 years? —Tamfang (talk) 06:52, 13 January 2011 (UTC)

Frequency of occurence

So if these events occur about every 10,000 years, then in 10 million years, there would be 1000 of these impacts. And in 100 million years, about 10,000 of these impacts. And the solar system is 40 times older than that. This raises two issues. Since the big ex-dinosaur impact 65 million years ago, how come another 6000 or so impacts since then, didn't make much difference ? If so many of these have crashed into the Earth, why are any left up there ?Eregli bob (talk) 23:43, 7 September 2012 (UTC)

There are about 25 million asteroids larger than 100 metres (PHO size) according to our asteroid article, we are not going to run out of them any time soon. The "dinosaur" asteroid was enormously larger than 100 metres and had much greater consequences than "regional devastation", but fortunately, these are much rarer events. SpinningSpark 00:35, 8 September 2012 (UTC)

100 - 150 m size??

Articles says that PHOs start from 100 - 150 m size. Objects that are smaller than about 100 m are NOT considered potentially hazardous? The Chelyabinsk meteor has been estimated to have a dimension of ca 17m - and did considerable damage. Is there no chance that with a different composition or entry angle an object of this size might release its energy closer to ground (more destruction)? Is the 100 - 150 m really an universally agreed definition of "PHO"? Kipala (talk) 09:05, 18 February 2013 (UTC)

To prevent multiple threads, see my reply at Talk:Near-Earth object/Archive 1#Size of potentially hazardous objects. -- Kheider (talk) 11:07, 18 February 2013 (UTC)

"Issues"-section

I removed this section, since all it contains is a quote with no context whatsoever, and thus it does not seem to add anything to the article. The actual citation might still be useful though. SBareSSomErMig (talk) 14:47, 17 June 2015 (UTC)

I am not sure why you reverted back to the 10 December 2014 version. You did more than remove a paragraph. -- Kheider (talk) 16:29, 17 June 2015 (UTC)

My mistake, I messed up. It appears you have fixed it, so thank you for that. SBareSSomErMig (talk) 16:31, 17 June 2015 (UTC)

Propose moving to "Potentially hazardous asteroid"

Since 1) it's less vague, 2) JPL uses PHA, 3) the article itself uses PHA ("PHA" count: 28, "PHO" count: 3), 4) Category:Potentially hazardous asteroids exists.   ~ Tom.Reding (talk ⋅dgaf)  05:48, 10 January 2016 (UTC)

Agreed as the MPC also only lists PHAs. Excluding the 66 "addiional fragments" of 73P/Schwassmann-Wachmann, JPL only lists (82-66)=16 comets with E-MOID<0.05AU. The diameter of many of these "comets" is very poorly determined as comets do not use the same absmag scale as an asteroid (H vs M2 values). Only 6 of these "comets" have an inclination greater than 20 degrees, which makes me wonder how many of these comets may be active asteroids perturbed out of the the main-belt. -- Kheider (talk) 20:35, 10 January 2016 (UTC)

I actually didn't notice that comets were included (even though it's written right there in the lead...), which could muddle the issue. But, yeah, going through all of the 82 items in that list shows that none of them are categorized as "potentially hazardous <anything>", which is worth noting in the article. Comets could become PHOs (or PHAs maybe), but apparently none of them currently are. We could have Potentially hazardous object redirect to a section in Potentially hazardous asteroid which talks about possible exceptions?   ~ Tom.Reding (talk ⋅dgaf)  21:15, 10 January 2016 (UTC)

We have 1,650 PHAs and only 16 short period-comets "with E-MOID<0.05AU". There is no official list (that I know of) of "Potentially hazardous comets". So this article should probably give PHAs more focus/weight. -- Kheider (talk) 23:41, 10 January 2016 (UTC)

Could mention or link to programs to find

Is this the best article to mention NASA Scout in ?

• nasas-new-asteroid-alert-system...
• NASA's New 'Intruder Alert' System Spots An Incoming Asteroid
• Incoming! New Warning System Tracks Potentially Dangerous Asteroids

- Rod57 (talk) 14:24, 21 January 2017 (UTC)