Comments on: And it came from the CMB . . . http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/ Blogging one sidereal day at a time Sat, 04 Feb 2012 16:26:45 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Gravitational Lenses: Making the invisible detectable at Pamela L. Gay http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/comment-page-1/#comment-2926 Gravitational Lenses: Making the invisible detectable at Pamela L. Gay Thu, 28 Jun 2007 00:08:24 +0000 http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/#comment-2926 [...] Two of the most well defined ways we have of studying the universe’s shadows are the Cosmic Microwave Background (CMB) and gravitational lenses. Both things are scientifically interesting in their own right, and each can be used to indirectly see otherwise invisible content in the universe. Recent papers have shown how the CMB may allow astronomers to study our own solar system’s Oort Cloud (the source of long period comets), and how gravitational lensing effects can be used to map dark matter. Rather than try and discuss both these topics in one post, I’m going to take on gravitational lenses today, and dig into the cosmic microwave background tomorrow. (image credit: Kneib & Ellis w/ Caltech Digital Media Center) [...] [...] Two of the most well defined ways we have of studying the universe’s shadows are the Cosmic Microwave Background (CMB) and gravitational lenses. Both things are scientifically interesting in their own right, and each can be used to indirectly see otherwise invisible content in the universe. Recent papers have shown how the CMB may allow astronomers to study our own solar system’s Oort Cloud (the source of long period comets), and how gravitational lensing effects can be used to map dark matter. Rather than try and discuss both these topics in one post, I’m going to take on gravitational lenses today, and dig into the cosmic microwave background tomorrow. (image credit: Kneib & Ellis w/ Caltech Digital Media Center) [...]

]]> By: pamela http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/comment-page-1/#comment-1551 pamela Mon, 14 May 2007 02:32:57 +0000 http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/#comment-1551 According to the paper, <a href="http://xxx.lanl.gov/abs/0705.0986" rel="nofollow"><small>"Long Period Comets (LPC) associated with the Oort Cloud originate in its outermost reaches because objects with large semi-ma jor axes can be preferentially ejected into the inner Solar System. The observed aphelia of LPCs place the outer limits of the Oort Cloud at a distance of approximately 25000 AU (Oort 1950; Marsden & Sekanina 1971), while simulations of the Oort Cloud’s formation, assuming that the Sun formed in a star cluster, suggest that a significant amount of mass may lie in an inner Oort Cloud, which is located at 1000 AU (Hills 1981; Fernandez 1997; Dones et al. 2004). To this point, we have no methods capable of detecting smaller objects in the Kuiper Belt or any objects in the inner Oort Cloud."</small></a> I'm willing to just use the adjectives used in the paper. Eventually, maybe, the IAU will come up with strict definitions. We're not there yet, so Oort owns everything according to Babich. The paper doesn't say exactly what fraction of light the Oort cloud blocks. They give an equation for how it would be blocked in the paper above as well as <a href="http://xxx.lanl.gov/abs/0705.0987" rel="nofollow">this one</a>, as a function of optical depth and temperature. According to the paper, “Long Period Comets (LPC) associated with the Oort Cloud originate in its outermost reaches because objects with large semi-ma jor axes can be preferentially ejected into the inner Solar System. The observed aphelia of LPCs place the outer limits of the Oort Cloud at a distance of approximately 25000 AU (Oort 1950; Marsden & Sekanina 1971), while simulations of the Oort Cloud’s formation, assuming that the Sun formed in a star cluster, suggest that a significant amount of mass may lie in an inner Oort Cloud, which is located at 1000 AU (Hills 1981; Fernandez 1997; Dones et al. 2004). To this point, we have no methods capable of detecting smaller objects in the Kuiper Belt or any objects in the inner Oort Cloud.”

I’m willing to just use the adjectives used in the paper. Eventually, maybe, the IAU will come up with strict definitions. We’re not there yet, so Oort owns everything according to Babich.

The paper doesn’t say exactly what fraction of light the Oort cloud blocks. They give an equation for how it would be blocked in the paper above as well as this one, as a function of optical depth and temperature.

]]> By: Michael Welford http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/comment-page-1/#comment-1543 Michael Welford Sun, 13 May 2007 19:05:06 +0000 http://www.starstryder.com/2007/05/12/and-it-came-from-the-cmb/#comment-1543 When I first read the article and saw the phrase Oort cloud, I assumed you were talking mainly about the proximate source of long period comets. I was going to ask how big a role heating from nearby stars and escaped comets from distant stars played in the teams calculations. But then, rereading the article I see that you use "Oort cloud" to mean 1000 AU from the Sun instead of say 100 times farther out. ( That 1000 AU figure occurs just before you messed up the discussion of temperature. ) So these days everything beyond Eris is the Oort cloud. Even objects whose orbits are stable against perterbation from distant stars. Fine. But doesn't Harvard boy realize that his lack of precision gives up a potential opportunity to name a vast region of the solar system after himself. Actually I think it would very exciting if they could find some quirk in comet distribution in the 1000 AU range. It would likely be evidence for a distant planet. Except we won't be allowed to call it a planet. Because the Priests of Prague have proclamed that a planet has to clear its orbital neighborhood, and a distant planet-massed object would have the effect of cluttering the far outer solar system with debris that Jupiter would otherwise have tossed to interstellar space. And does the Oort cloud actually block a significant amount of radiation at any frequency? When I first read the article and saw the phrase Oort cloud, I assumed you were talking mainly about the proximate source of long period comets. I was going to ask how big a role heating from nearby stars and escaped comets from distant stars played in the teams calculations. But then, rereading the article I see that you use “Oort cloud” to mean 1000 AU from the Sun instead of say 100 times farther out. ( That 1000 AU figure occurs just before you messed up the discussion of temperature. ) So these days everything beyond Eris is the Oort cloud. Even objects whose orbits are stable against perterbation from distant stars. Fine. But doesn’t Harvard boy realize that his lack of precision gives up a potential opportunity to name a vast region of the solar system after himself.

Actually I think it would very exciting if they could find some quirk in comet distribution in the 1000 AU range. It would likely be evidence for a distant planet. Except we won’t be allowed to call it a planet. Because the Priests of Prague have proclamed that a planet has to clear its orbital neighborhood, and a distant planet-massed object would have the effect of cluttering the far outer solar system with debris that Jupiter would otherwise have tossed to interstellar space.

And does the Oort cloud actually block a significant amount of radiation at any frequency?

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