More than 90 percent of objects found in the vast outer-solar system reservoir may have been born around other stars
in [Physics]
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From: palsing on 17 Jun 2010 20:54 On Jun 17, 12:06 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > It's obvious that the radial speed must increase > until Sirius passes the point of closest approach > in about 60,000 years, a minimum distance of about > 7.8 light years, after which the radial component > of the speed will decrease again. The total speed > will remain at about 18.3 km/sec (vector addition > of the radial and proper motion components). Greg, As much as I enjoy sparring with Guth (a battle of wits with an unarmed person), I'm not so sure I agree with your above statement. I agree that Sirius has a constant total speed WRT the sun of 18.3 km/ sec, and would also agree that the radial component and the proper motion component are each variable depending on just when you measure them over time, but it seems to me that a star's motion towards us from far, far away would be mostly radial, and as it was passing us it would be mostly proper motion, and as it was receding it would eventually revert to radial, with the opposite sign... so, since Sirius is nearly to the point of passing us by (a mere 60,000 year blink of an eye from now), it would seem to me that the radial motion is getting smaller and the proper motion is getting bigger... isn't it? Something crossing directly 'across our bow', as it were, for an instant would have no radial velocity at all, would it? Am I missing something here? \Paul A
From: Greg Neill on 17 Jun 2010 21:00 palsing wrote: > On Jun 17, 12:06 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > >> It's obvious that the radial speed must increase >> until Sirius passes the point of closest approach >> in about 60,000 years, a minimum distance of about >> 7.8 light years, after which the radial component >> of the speed will decrease again. The total speed >> will remain at about 18.3 km/sec (vector addition >> of the radial and proper motion components). > > Greg, > > As much as I enjoy sparring with Guth (a battle of wits with an > unarmed person), I'm not so sure I agree with your above statement. > > I agree that Sirius has a constant total speed WRT the sun of 18.3 km/ > sec, and would also agree that the radial component and the proper > motion component are each variable depending on just when you measure > them over time, but it seems to me that a star's motion towards us > from far, far away would be mostly radial, and as it was passing us it > would be mostly proper motion, and as it was receding it would > eventually revert to radial, with the opposite sign... so, since > Sirius is nearly to the point of passing us by (a mere 60,000 year > blink of an eye from now), it would seem to me that the radial motion > is getting smaller and the proper motion is getting bigger... isn't > it? Something crossing directly 'across our bow', as it were, for an > instant would have no radial velocity at all, would it? > > Am I missing something here? Nope. I did; I typed before I thought. Good catch.
From: palsing on 17 Jun 2010 21:41 On Jun 17, 6:00 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > palsing wrote: > > On Jun 17, 12:06 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > > >> It's obvious that the radial speed must increase > >> until Sirius passes the point of closest approach > >> in about 60,000 years, a minimum distance of about > >> 7.8 light years, after which the radial component > >> of the speed will decrease again. The total speed > >> will remain at about 18.3 km/sec (vector addition > >> of the radial and proper motion components). > > > Greg, > > > As much as I enjoy sparring with Guth (a battle of wits with an > > unarmed person), I'm not so sure I agree with your above statement. > > > I agree that Sirius has a constant total speed WRT the sun of 18.3 km/ > > sec, and would also agree that the radial component and the proper > > motion component are each variable depending on just when you measure > > them over time, but it seems to me that a star's motion towards us > > from far, far away would be mostly radial, and as it was passing us it > > would be mostly proper motion, and as it was receding it would > > eventually revert to radial, with the opposite sign... so, since > > Sirius is nearly to the point of passing us by (a mere 60,000 year > > blink of an eye from now), it would seem to me that the radial motion > > is getting smaller and the proper motion is getting bigger... isn't > > it? Something crossing directly 'across our bow', as it were, for an > > instant would have no radial velocity at all, would it? > > > Am I missing something here? > > Nope. I did; I typed before I thought. Good catch. Well, it's not like I've never done that myself before... \Paul A
From: Brad Guth on 18 Jun 2010 00:57 On Jun 17, 12:06 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > Brad Guth wrote: > > On Jun 17, 10:43 am, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > >> Brad Guth wrote: > >>> You purely subjective interpretation that's obfuscation saturated and > >>> Semitic approved is noted. > > >>> Too bad you can't simulate a damn thing, perhaps because that would > >>> make you look even more stupid. > > >>> Even if there's nothing elliptical and the closing velocity of 7.6 km/ > >>> sec were a constant, as for going back 300e6 BP is only an added > >>> distance of 7.6e3 ly when that molecular cloud of at least 12.5e6 Ms > >>> existed. > > >> As expected you've bollocked up the calculation; > >> you've forgotten the contribution of the proper > >> motion velocity components to the total velocity. > > >> The speed of sirius with respect to the solar > >> system is about 18.2 km/sec, of which less > >> than half is currently directed radially. > > > You forgot or rather ignored that everything is in orbit around > > something, so we're even. > > Hardly. Why don't you work out the curvature of the > trajectory of an object orbiting (essentially) the > center of the galaxy at the dystance of sol and > sirius? See if it makes a distance over a few > thousand years. Hint: The Sun's trip around the > galaxy takes about 230 to 250 million years. > > > > > We are still headed towards Sirius at 7.6 km/sec and seemingly > > speeding up (not slowing down). > > "Seemingly"? Where are your figures? Here are > mine: > > It's obvious that the radial speed must increase > until Sirius passes the point of closest approach > in about 60,000 years, a minimum distance of about > 7.8 light years, after which the radial component > of the speed will decrease again. The total speed > will remain at about 18.3 km/sec (vector addition > of the radial and proper motion components). Your purely subjective sources for those numbers and lack of any computer simulation is noted. Obfuscating and/or denial as to the elliptical trajectory that we're on is also noted. So, according to you and other Semites, gravity works only on stuff that's within the radii of our Oort cloud, and our passive solar system isn't going anywhere except farther away from Sirius. You're suggesting that anything more than one light year and of whatever gravity doesn't matter regardless of the original masses involved. Now I get it. Politically and Semite correct physics is all that matters. ~ BG
From: Brad Guth on 18 Jun 2010 01:03
On Jun 17, 5:54 pm, palsing <pnals...(a)gmail.com> wrote: > On Jun 17, 12:06 pm, "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote: > > > It's obvious that the radial speed must increase > > until Sirius passes the point of closest approach > > in about 60,000 years, a minimum distance of about > > 7.8 light years, after which the radial component > > of the speed will decrease again. The total speed > > will remain at about 18.3 km/sec (vector addition > > of the radial and proper motion components). > > Greg, > > As much as I enjoy sparring with Guth (a battle of wits with an > unarmed person), I'm not so sure I agree with your above statement. > > I agree that Sirius has a constant total speed WRT the sun of 18.3 km/ > sec, and would also agree that the radial component and the proper > motion component are each variable depending on just when you measure > them over time, but it seems to me that a star's motion towards us > from far, far away would be mostly radial, and as it was passing us it > would be mostly proper motion, and as it was receding it would > eventually revert to radial, with the opposite sign... so, since > Sirius is nearly to the point of passing us by (a mere 60,000 year > blink of an eye from now), it would seem to me that the radial motion > is getting smaller and the proper motion is getting bigger... isn't > it? Something crossing directly 'across our bow', as it were, for an > instant would have no radial velocity at all, would it? > > Am I missing something here? > > \Paul A We're speeding up as we head back towards Sirius, so we're not crossing its bow for a few ten thousand years, but we are encountering its Oort cloud. ~ BG |