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Re: Killer asteroids

Cross-posted to 5 groups.

Followups directed to: sci.astro

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Greg Goss wrote:

> Ned Latham <nedlatham@woden.valhalla.oz> wrote:
>>> > https://www.universetoday.com/36398/
>>> > what-is-the-difference-between-asteroids-and-meteorites/
>>
>>"While we know that some asteroids pass very close to Earth's orbit
>>around the Sun, we've been lucky in the history of humanity that we
>>haven't had a large asteroid hit Earth in the past several thousand
>>years. It wasn't until satellite imagery of Earth became widely
>>available that scientists were able to see evidence of past asteroid
>>impacts.?
>>
>>> > If it landed, it's not an asteroid.
>>
>>Wrong again, idiot. You should read your source *before&
>>using it.
> 
> Where is the cut-off between "Asteroid" and "Meteor"?

That is like asking “Where is the cut-off between ‘apples’ and ‘oranges’?”

I could not find a normative definition specifically for “asteroid”, but 
search results on the IAU Web site suggest that it is equivalent to “minor 
planet”:

,-<https://www.iau.org/public/themes/pluto/>
| 
| Pluto and the Developing Landscape of Our Solar System
| =======================================================
| 
| […]
| 
| The final resolution
| ---------------------
| 
| The first draft proposal for the definition of a planet was debated 
| vigorously by astronomers at the 2006 IAU General Assembly in Prague and a 
| new version slowly took shape. This new version was more acceptable to the 
| majority and was put to the members of the IAU for a vote at the Closing 
| Ceremony on the 24 August 2006. By the end of the Prague General Assembly, 
| its members voted that the resolution B5 on the definition of a planet in 
| the Solar System would be as follows:
| 
|   A celestial body that (a) is in orbit around the Sun, (b) has sufficient 
|   mass for its self-gravity to overcome rigid body forces so that it 
|   assumes a hydrostatic equilibrium (nearly round) shape, and (c) has
|   cleared the neighbourhood around its orbit.
| 
| […]
| 
| Planets, Dwarf Planets and Small Solar System Bodies
| ----------------------------------------------------
| 
| Questions and Answers
| 
| […]
| Q: How many dwarf planets are there? 
| A: Currently there are five objects accepted as dwarf planets. Ceres, 
| Pluto, Eris, Makemake and Haumea. 
| 
| […]
| Q: What is Ceres? 
| A: Ceres is (or now we can say it was) the largest asteroid, about 1000 km 
| across, orbiting in the asteroid belt between Mars and Jupiter. […]
| 
| Q: Didn't Ceres used to be called an asteroid or minor planet? 
| A: Historically, Ceres was called a planet when it was first discovered in 
| 1801, orbiting in what is known as the asteroid belt between Mars and 
| Jupiter. In the 19th century astronomers could not resolve the size and 
| shape of Ceres, and because numerous other bodies were discovered in the 
| same region, Ceres lost its planetary status. For more than a century, 
| Ceres has been referred to as an asteroid or minor planet. 
| 
| […]
| Q: What is a [“small Solar System body”]? 
| A: The term "small Solar System body" is a new IAU definition to encompass 
| all objects orbiting the Sun that are too small (not sufficiently massive) 
| to satisfy the definition of planet or dwarf planet. 
| 
| Q: Is the term [“minor planet”] still to be used? 
| A: The term "minor planet" may still be used. But generally the term 
| [“small Solar System body”] will be preferred. 

,-
<https://www.iau.org/static/science/scientific_bodies/commissions/f1/meteordefinitions_approved.pdf>
| 
| Definitions of terms in meteor astronomy
| =========================================
| 
| […]
| *Meteor* is the light and associated physical phenomena (heat, shock, 
| ionization), which result from the high speed entry of a solid object from
| space into a gaseous atmosphere.
| 
| *Meteoroid* is a solid natural object of a size roughly between 30 
| micrometers and 1 meter moving in, or coming from, interplanetary space.
| 
| […]
| *Meteorite* is any natural solid object that survived the meteor phase in
| a gaseous atmosphere without being completely vaporized. 
| 
| […]
| The explanatory remarks, comments and secondary definitions (in bold)
| ----------------------------------------------------------------------
| 
| Remarks to */meteor/* 
| 
| The meteor phenomenon can be caused by a meteoroid, an asteroid, a comet
| or any solid matter with the appropriate combination of velocity, mass and
| mean-free-path in a planetary atmosphere. 
| 
| […]
| This document was approved by the majority of members of IAU Commission F1
| participating in the electronic voting completed on April 30, 2017. 

Please learn how to use Usenet and stop the mindless crossposting across 
alt.ALL and the Big 8 without Followup-To.

F'up2 sci.astro

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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Thread

Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-25 09:46 -0700
  Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-27 13:50 -0700
    Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-27 13:58 -0700
      Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-27 21:17 -0700
    Re: Killer asteroids Ned Latham <nedlatham@woden.valhalla.oz> - 2017-05-28 08:14 -0500
      Re: Killer asteroids "J. Clarke" <j.clarke.873638@gmail.com> - 2017-05-28 13:23 -0400
        Re: Killer asteroids Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-28 20:28 +0200
        Re: Killer asteroids Ned Latham <nedlatham@woden.valhalla.oz> - 2017-05-29 07:23 -0500
      Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-28 11:15 -0700
        Re: Killer asteroids Ned Latham <nedlatham@woden.valhalla.oz> - 2017-05-29 07:38 -0500
      Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-29 10:54 -0700
        Re: Killer asteroids Ned Latham <nedlatham@woden.valhalla.oz> - 2017-05-29 18:14 -0500
          Re: Killer asteroids Greg Goss <gossg@gossg.org> - 2017-05-29 19:25 -0600
            Re: Killer asteroids jimp@specsol.spam.sux.com - 2017-05-30 02:37 +0000
            Re: Killer asteroids Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-30 14:08 +0200
              Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-30 10:35 -0700
                Re: Killer asteroids Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-31 00:39 +0200
                Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-30 16:14 -0700
                Re: Killer asteroids Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-31 22:17 +0200
                Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-31 13:52 -0700
                Re: Killer asteroids Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-06-01 02:12 +0200
          Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-29 22:35 -0700
            Re: Killer asteroids Ned Latham <nedlatham@woden.valhalla.oz> - 2017-05-30 17:01 -0500
              Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-30 15:43 -0700
                Re: Killer asteroids The Starmaker <starmaker@ix.netcom.com> - 2017-05-30 17:08 -0700
  Re: Killer asteroids tesla sTinker <truecatholicstaff@truecarpentry.org> - 2017-05-28 20:40 -0700
    Re: Killer asteroids Poutnik <poutnik4nntp@gmail.com> - 2017-05-29 06:59 +0200
      Re: Killer asteroids tesla sTinker <truecatholicstaff@truecarpentry.org> - 2017-05-29 21:29 -0700
        Re: Killer asteroids benj <benj@nobody.net> - 2017-05-30 17:01 -0400
      Re: Killer asteroids tesla sTinker <truecatholicstaff@truecarpentry.org> - 2017-05-29 21:52 -0700

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