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Wiley
2001-Dec-12, 07:24 PM
Here's an article on the interstellar medium that appears in the latest Scientific American. I thought y'all might be interested.

The article (http://sciam.com/2002/0102issue/0102reynolds.html)

Azpod
2001-Dec-12, 08:45 PM
On 2001-12-12 14:24, Wiley wrote:
Here's an article on the interstellar medium that appears in the latest Scientific American. I thought y'all might be interested.

The article (http://sciam.com/2002/0102issue/0102reynolds.html)



Question: the article mentions a structure called the Local Bubble that we are in, formed by a supernova nearby ~1 million years ago. Does anyone have information on this event? Is there a stellar remnant nearby that we think is the culprit? How far was it away from the Sun when it happened? Is there any evidence from the fossil record of extinctions and/or mutations occuring when the shockwave would have reached Earth?

I haven't heard of this event before, so I am curious.

[Edit-- moved my comments out of the quote!]

_________________
Just FYI-- lobster sticks to magnet.
That is all.

--Azpod... Formerly known as James Justin

<font size=-1>[ This Message was edited by: Azpod on 2001-12-12 15:47 ]</font>

ljbrs
2001-Dec-16, 12:03 AM
There had to be a Type II Supernova in the vicinity of our resultant Sun, because the elements found in the Sun and in the Earth (and other planets in the Solar System had to be created in a Supernova (and were not simply the result of the Big Bang nucleosynthesis. Many stars lack these heavier elements which are in our system. We know that there was a supernova because of these resultant elements which would not be there otherwise.

They are the smoking gun...

ljbrs /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_smile.gif

ljbrs
2001-Dec-16, 12:06 AM
On the other hand, a bubble is more speculative than the analysis of elements present in the solar neighborhood.

ljbrs /phpBB/images/smiles/icon_smile.gif

Kaptain K
2001-Dec-16, 10:40 AM
The presence of elements heavier than helium is evidence for probably several supernovae in the 10 billion years between the formation of the galaxy and the birth of the Sun and its retinue of planets.
The question, however, had to do with a supernova about 1 million years ago that might have blown out the "local bubble" in which we seem to reside.

Blob
2006-Oct-25, 01:26 AM
The Sun had sisters when it was born. In fact, according to new research, it had hundreds of thousands of siblings.
And at least one was a supernova, providing further support for the idea that there could be lots of planets around other stars since our solar system emerged in such an explosive environment.

"We know that the majority of stars in our galaxy were born in star clusters. Now we also know that the newborn solar system not only arose in such a cluster, but also survived the impact of an exploding star. This suggests that planetary systems are impressively rugged and may be common in even the most tumultuous stellar nurseries" - Leslie Looney, who arrived at the solar sibling finding along with his colleagues at the University of Illinois at Urbana-Champaign.

Read more (http://www.msnbc.msn.com/id/15403371/)

ozark1
2006-Oct-25, 11:38 AM
Question: the article mentions a structure called the Local Bubble that we are in, formed by a supernova nearby ~1 million years ago. Does anyone have information on this event? Is there a stellar remnant nearby that we think is the culprit? How far was it away from the Sun when it happened? Is there any evidence from the fossil record of extinctions and/or mutations occuring when the shockwave would have reached Earth?

I haven't heard of this event before, so I am curious.

[Edit-- moved my comments out of the quote!]

_________________
Just FYI-- lobster sticks to magnet.
That is all.

--Azpod... Formerly known as James Justin

<font size=-1>[ This Message was edited by: Azpod on 2001-12-12 15:47 ]</font>

The best candidate for the most recent SN in the local bubble is a old pulsar called Geminiga. It probably went SN between 120 and 180 light years from earth about 2 million years ago. There was a mass extinction of certain classes of radiation sensitive marine animals at the time.

The local bubble (or chimney) is a region with less than 1/10 of the normal milky way interstellar gas density. It's about 300 ly across and was created/cleared by up to 6 supernovae from the Sco-Cen OB association. The sun is near to one wall and will encounter higher density gas again within 100,000 years. In fact we might have started to encounter a higher density region already (the local fluff).

The local bubble is not unique. Sco-Cen is creating another bubble at the moment (Loop 1) and there are several other known bubbles associated with the Perseus OB assoc, the Pleiades and others.

The big theory issue is what happens to the solar system. In the local bubble the sun's heliopause is 100 AU+ out (About perihelion of Sedna). When we reenter "normal" gas some researchers think that the heli0pause will be inside the orbit of Jupiter. Under these circumstances the earth will be far more exposed to interstellar events than now.

trinitree88
2006-Oct-29, 11:46 PM
[QUOTE=Azpod;4099]Question: the article mentions a structure called the Local Bubble that we are in, formed by a supernova nearby ~1 million years ago. Does anyone have information on this event? Is there a stellar remnant nearby that we think is the culprit? How far was it away from the Sun when it happened? Is there any evidence from the fossil record of extinctions and/or mutations occuring when the shockwave would have reached Earth?

I haven't heard of this event before, so I am curious.

Azpod. The exact morphological characteristics (shape) of the Local Bubble remains somewhat in dispute. (Try Googling Local Bubble). A good initial summary was published many moons ago in Sky & Telescope,circa 1994-5, (Dec.-Jan?) by Alyssa Goodman of the Harvard Smithsonian Center for Astrophysics. In it an artists rendition of the structure from then-radio-surveys indicated a slight oval or prolate spheroid...quite typical of a supernova remnant (my area of interest).Recently, Local Bubble conferences have decided to coordinate observations over wide ranges of the electromagnetic spectrum, to create instrumental overlap of times of observing the same patch of sky(a good thing), and to try to publish data with images in standardized formats by size, so that infrared, visible, UV, X-ray, gamma ray, microwave, radio..might all be overlapped for coincident observations.(a better thing)
Doppler estimates of the velocity of the expanding walls of the Local Bubble give ~ 25-30 km/sec. This is interesting because it's at ~ that range that the temperature of the walls begins to allow the growth of dust grains of refractory compounds (those with high melting points...as you cool plasma down, they appear first)olivine, silica, pyroxene etc. (read stuff by Eli Dwek, NASA Space Goddard).
My interest has been in the microwave contribution that the wall brings to the CMB. It is at least thermodynamically possible for the wall to produce a microwave hiss, smooth to ~one part in 10,000, with a slight asymmetry due to parity effects in supernova remnants. Initially, I had hoped to find what percentage contribution the wall might make to some sort of systemic error in measuring the CMB. I was both quite surprised and delighted to find that there is sufficient kinetic energy deposited to give an upper limit of ~ 2.79 K for it's hiss....all local.
There is of course the historical evidence for catastrophic loss of life in the late Bronze age..~540 AD, well documented by the Irish dendrochronologist (tree rings) Michael Baillie, at Queens College, Dublin. Catastrophic loss of life occurred in all cultures worldwide. From typical supernova expansion velocities, and the distance from the sun to the presumed epicenter of the Local Bubble, I had predicted in 1994-5 that the primary supernova event should have taken place ~1800-2000 years ago, and was in all probability the origin of the the popular legend of the Star of Bethlehem, to be accompanied by a dusting of the surface of Earth and Mars between 450-600 AD. At less than 5 light years...that's a show.
The authors' argument for an earlier epoch for the sun's sister is also possible, of course, and some might consider the lost Pleiad, that disappeared during the Trojan War epoch, but neither of those accounts for the tree ring
anomaly documented by M.Baillie. An isotopic analysis of marine core sediments from the ~ 540 Ad era should prove interesting. If it's rich in hematite (like the surface of Mars) or iron-60, it will prove interesting.
As Steve Strom at Umass has shown that stars that form in clusters usually have common magnetic polarizations, the Local Bubble ought to carry a polarization linked somewhat anomalously to the sun's spin axis....Tegmark's axis-of-evil. Interesting. Pete.

eburacum45
2006-Oct-30, 04:54 PM
You reckon that there was a supernova 1800-2000 years ago, within 5 light years?
I doubt that very much; it would have severely affected the atmosphere at that distance. Additionally we should have found the remnant- it can't have got far in 2000 years. 10 light years tops. No such remnant is evident as far as I know; therefore no close supernova.

To address your other points; why do you think the local Bubble would be related in any way to the Sun? If it was caused by the explosion of Geminga, that star certainly was not born at the same time as the Sun; in fact I don't know that any star is a good candidate for being one of the Sun's sisters from the birth cluster. Certainly not the Pleiades; they are only 100 million years old, and I don't believe that any supernova remnant has been found there, either.

trinitree88
2006-Oct-30, 11:02 PM
:silenced:
You reckon that there was a supernova 1800-2000 years ago, within 5 light years?
I doubt that very much; it would have severely affected the atmosphere at that distance. Additionally we should have found the remnant- it can't have got far in 2000 years. 10 light years tops. No such remnant is evident as far as I know; therefore no close supernova.

To address your other points; why do you think the local Bubble would be related in any way to the Sun? If it was caused by the explosion of Geminga, that star certainly was not born at the same time as the Sun; in fact I don't know that any star is a good candidate for being one of the Sun's sisters from the birth cluster. Certainly not the Pleiades; they are only 100 million years old, and I don't believe that any supernova remnant has been found there, either.


Eburacum. The image printed in Sky & Telescope, accompanying the article by Ms Goodman, indicated an epicenter ~ 45 light years from the sun.
Expansion velocities of type 2 supernovae at least, (published by Alexei Fillipenko in the Astrophysical Journal,)following SN1987a, indicated velocities as high as c/10 for expansion of the ejecta. If that ejecta expands into a bubble previously cleared by a supernova, it can cover 180 light years (the ~ radius of the published graphic), in about 1800 years. A. Fillipenko is one of the world's leading theorists in supernova theory.
We live in a remnant....the Local Bubble...along with several dozen other nearby ultraviolet emitting stars. That's how the Local Bubble is defined...those stars beyond the "swept" volume have their ultraviolet emissions absorbed, or scattered by the intervening dust and gas.
There is at least some historical evidence that the Lost Pleiad disappeared during the Trojan War. At a distance of ~400 light-years, the Pleiades are proximate to Geminga's distance...also ~ 400 light years...so it's at least possible that Geminga is the pulsar from that event. That epoch was recent enough that a second supernova would expand it's ejecta almost unhindered, producing the ~180 light year radius Local Bubble in ~1800-2000 years.
It is of more than a curiosity that such a second ejecta cloud, running into a primary ejecta cloud, and braking, would give off first an optical, then an infrared, then a microwave display. It is also of more than a curiosity that kinematic equations using no dark matter, no dark energy, and no Big Bang, but only conservation of momentum, conservation of energy, and the Stefan-Boltzmann Law yield an upper limit to the energy density of the microwave hiss at ~ 2.79 K, for the present Bubble wall velocity (~25 km/sec)...not far from the observed 2.72.(Hartford AAPT Meeting, "Downsizing the Big Bang", ATM thread Local Bubble CMB..trinitree88.
While it is true that the exact morphology of the Local Bubble remains a construct in progress...CMB maps routinely subtract all foregrounds...potential sources of the CMB itself.
The argument that no dust can emit smoothly has been taken up in it's appropriate forum..ATM. The Astrophysical Journal article by Hines , Low & Schreiber found dust using Hubble's NICMOS, around HD98800, emitting in a SED best fit by a near blackbody curve around 165 K.
Recent work on Cas A, and Tycho's remnant by Dwek indicates spectral fits best modeled by the presence of iron whiskers in the remnant interior. We live in a remnant interior. Iron whiskers emit pretty blackbody. They also emit polarized emissions when magnetically aligned. So it's probably just a coincidence that the CMB octopole emissions are aligned with the magnetic axis,(and spin axis...axis of evil) of the sun and the solar system....a galactic arm foreground (Local Bubble Wall),with the right optical density, right kinetic energy, right momentum, right composition, and right temperature to be coincidently emitting the same spectrum....should be removed.
Kind of reminds me of Steinbeck's short story..."The Lottery". They draw straws and then kill somebody every year by stoning them to death...because they always have. Fun community..... :silenced: Pete

ArgoNavis
2006-Oct-31, 03:18 AM
Here's an article on the interstellar medium that appears in the latest Scientific American. I thought y'all might be interested.

The article (http://sciam.com/2002/0102issue/0102reynolds.html)

This article appears to have been moved and I am not getting anything on this address.

Do you mean this one?

http://www.sciam.com/article.cfm?articleId=0002BE5A-D608-152F-960883414B7F0123

Blob
2006-Oct-31, 10:39 AM
The Solar System sits within a shell or bubble of expanding hot gas that radiate low-energy X-rays, known as the “Local Hot Bubble” created by a supernova. A study using data from the XMM-Newton Space Telescope has shown that this local bubble is being compressed by an even more recent supernova remnant, the “Loop 1 Superbubble”, which is expanding faster and is compressing an area of cool dense gas, known as the Wall, that lies between the two shells.

The Local Hot Bubble because of this and many more ancient remnants has actually an hourglass shape.


Title: A Cold Nearby Cloud Inside the Local Bubble
Authors: David M. Meyer, J.T. Lauroesch, Carl Heiles, J.E.G. Peek, Kyle Engelhorn

The high-latitude Galactic H I cloud toward the extragalactic radio source 3C 225 is characterised by very narrow 21 cm emission and absorption indicative of a very low H I spin temperature of about 20 K. Through high-resolution optical spectroscopy, we report the detection of strong, very narrow Na I absorption corresponding to this cloud toward a number of nearby stars. Assuming that the turbulent H I and Na I motions are similar, we derive a cloud temperature of 20 (+6, -8) K (in complete agreement with the 21 cm results) and a line-of-sight turbulent velocity of 0.37 ±0.08 km/s from a comparison of the H I and Na I absorption linewidths. We also place a firm upper limit of 45 pc on the distance of the cloud, which situates it well inside the Local Bubble in this direction and makes it the nearest-known cold diffuse cloud discovered to date.

Read more (http://arxiv.org/PS_cache/astro-ph/pdf/0609/0609611.pdf) (32kb, PDF)

Ken G
2006-Nov-01, 03:04 PM
[QUOTE=trinitree88;856462 Iron whiskers emit pretty blackbody. They also emit polarized emissions when magnetically aligned. So it's probably just a coincidence that the CMB octopole emissions are aligned with the magnetic axis,(and spin axis...axis of evil) of the sun and the solar system....a galactic arm foreground (Local Bubble Wall),with the right optical density, right kinetic energy, right momentum, right composition, and right temperature to be coincidently emitting the same spectrum....should be removed.
[/QUOTE]

Pete, you are making a lot of very interesting points here about the possibility of a recent nearby supernova, but this idea that the CMB is due to a dust wall from that supernova is not very reasonable. There is no supernova remnant in all of space with anything that remotely approaches the uniformity of the CMB. That alone rules out your model, not that it isn't informative to consider such alternatives.

eburacum45
2006-Nov-02, 11:06 AM
There is at least some historical evidence that the Lost Pleiad disappeared during the Trojan War. At a distance of ~400 light-years, the Pleiades are proximate to Geminga's distance...also ~ 400 light years...so it's at least possible that Geminga is the pulsar from that event.
They may be approximately at the same distance, but they are far apart in the sky. According to my estimate (using Celestia) Geminga is 356 light years from the Pleiades; if it were ejected 3200 years ago (during the Trojan War epoch) it would need to have been travelling at nearly 0.1 c all that time. In fact the proper motion of Geminga is more like 20 times the speed of Sound; much, much slower.

Geminga is currently believed to be 552 light years from Earth, and to be 300,000 years old; none of this fits with your scenario. And I am pretty sure that there is no recent supernova remnant within 50 light years of the Earth, and certainly not one which is only 3000 years old or so; it would surely dominate the radio sky or be prominent in other wavelengths, even if we couldn't see it visually.

trinitree88
2006-Nov-06, 01:00 AM
They may be approximately at the same distance, but they are far apart in the sky. According to my estimate (using Celestia) Geminga is 356 light years from the Pleiades; if it were ejected 3200 years ago (during the Trojan War epoch) it would need to have been travelling at nearly 0.1 c all that time. In fact the proper motion of Geminga is more like 20 times the speed of Sound; much, much slower.

Geminga is currently believed to be 552 light years from Earth, and to be 300,000 years old; none of this fits with your scenario. And I am pretty sure that there is no recent supernova remnant within 50 light years of the Earth, and certainly not one which is only 3000 years old or so; it would surely dominate the radio sky or be prominent in other wavelengths, even if we couldn't see it visually.

Eburacum. Agreed, if that's the required velocity for Geminga, it's too high.1%c is about the limit..must be another pulsar, hopefully yet to be found.
As to whether the bubble dominates the radio sky, or not, I'll stick to my conservation laws here...at ~180 light years, 25-30 km/sec, it's almost entirely microwave, with a column density just sufficient to quench exo-bubble stars' ultraviolet through Rayleigh-Taylor scattering.

trinitree88
2007-May-10, 06:14 PM
Pete, you are making a lot of very interesting points here about the possibility of a recent nearby supernova, but this idea that the CMB is due to a dust wall from that supernova is not very reasonable. There is no supernova remnant in all of space with anything that remotely approaches the uniformity of the CMB. That alone rules out your model, not that it isn't informative to consider such alternatives.

Ken G. It now seems that overlaying microwave emissions with gas velocity distributions of H1 regions is adding some interest in the community in mechanisms for the generation of microwaves from the implicit geometry of these areas. Good. I'll be keeping a light tab on these activities as they warm up.pete

RussT
2007-May-11, 07:40 AM
http://antwrp.gsfc.nasa.gov/apod/ap020217.html

This could be of interest.