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Amara Graps - Dust as photons


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#1 Bruce Klein

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Posted 11 July 2005 - 06:49 AM


Chat Topic: Amara Graps - Dust as photons
Astronomer, Amara Graps joins ImmInst Chat to help members follow the trail of dust from supernovae to us. Is dust is a piece of us, or are we a piece of the dust?

Chat Time: Sun Aug 21 @ 8 pm Eastern (Time Zone Guide)
Chat Room: http://www.imminst.org/chat

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Amara Graps, Astronomer & ImmInst Member, amaragraps

#2 Bruce Klein

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Posted 30 August 2005 - 05:23 PM

Chat Archive:

[01:51] Amara: Is anyone here?
[01:51] worldeater: i am
[01:52] Amara: There is a thunderstorm in progress, and I did not
sleep as long as I wanted (It is 2am here)
[01:52] worldeater: oh where are you?
[01:52] Amara: Let me get some tea and I will be back in 5 minutes..
[01:52] worldeater: ok
[01:52] Jonesey: hi amara, actually i know a west african with your first name
[02:04] Amara: Hi.. I'm back. Do I give an introduction to this topic
first typically, and should I give an introduction to myself?
[02:05] Jonesey: whichever you'd like
[02:05] Jonesey: BJK's not here, so however you want to talk. I
didn't even realize there was a chat scheduled
[02:06] Amara: OK. The topic is 'Dust as Photons'. I chose this
phrase from a piece of poetry I wrote during my thesis. I'll post
that first.
[02:07] Amara: The dust wakes out of its slumber and I follow its passage.
[02:07] Amara: From volcanoes on moons, through comet breezes,
[02:07] Amara: Atop bookshelves in rooms, expelled by human sneezes,
[02:07] Amara: From disks of new stars into emerald-blue planets,
[02:07] Amara: The dust is a piece of me, or am I a piece of dust?
[02:07] Amara: We fly from the ecliptic brightness,
[02:07] Amara: feel comforted by the local fluff, and
[02:07] Amara: drink a ceylon tea at the cosmic tea table
[02:07] Amara: with our friends from beta Pic.
[02:07] Amara: They don't laugh at my jokes, but I smile anyway.
[02:08] Amara: I wrote that in March 2001. I finished my thesis in
July 2001 (University of Heidelberg, Germany)
[02:09] Amara: So while I am a relatively new postdoc, I have been
working in astronomy since 1980.
[02:09] Amara: I spent many years as a scientific programmer working
for different astronomy groups (JPL, NASA-Ames, Stanford).
[02:10] Amara: In 1995 during the recovery of a repetitive strain
injury I decided that I couldn't make excuses any more for not
getting a PhD.
[02:12] Amara: So I moved from California to Heidelberg and made my
degree there. I chose Heidelberg because my advisor was there,
primarily. But also because I could complete in a shorter time since
my masters degree allowed me to jump into the German system not
needing any more classes.
[02:13] Amara: So to introduce myself, I am Amara Graps, an
astronomer who followed a rather circuitous path through astronomy.
Just like the dust...
[02:14] Amara: Dust particles, like photons, are born at remote sites in space
[02:14] Amara: and time, and carry from there information that may not be
[02:14] Amara: accessible to direct investigation.
[02:15] Amara: By the way, this is my first ever IRC chat session, so
if I am doing something not usually done in chat sessions, please
educate me!
[02:16] Amara: From knowledge of the dust particles' birthplace and
their bulk properties, we can learn about the remote environment out
of which the particles were formed.
[02:20] Amara: Once cosmic dust is detected, the scientific problem
to be solved is an inverse problem to determine what processes
brought that encoded 'photon-like' object (dust) to the detector;
e.g. the dust particle wouldn't have reached the detector unless its
initial motion, material properties, the intervening plasma and
magnetic field heldparticular values. Slightly changing any of these
parameters can give significantly different dust dynamical behavior.
Therefore, one can learn about where that object came from, and what
is (in) the intervening medium. So that is what I mean by dust as
photons.
[02:20] Amara: End of introduction...
[02:24] Amara: Jonesey: Regarding my name, there are so many meanings
and variations that I wrote a page at my web site listing them.
Because I have the amara.com for the last 10 years, I think every
amara in the world (or at least those with Internet access) have
written me telling me I have their name.
[02:25] Amara: And to answer worldeater's first question, I'm located
in the outskirts of Rome, Italy.
[02:26] Jonesey: haha Amara
[02:26] Jonesey: and thanks for giving me the perfect excuse not to
sweep or dust, dont' want to destroy all that valuable information
[02:28] Amara: The old jokes that dust astronomers hear all of the
time is usually regarding the dust under everyone's bed. I think that
very little of that is cosmic, actually! But you can leave it there,
if you want...
[02:28] Jonesey: hehe thanx
[02:29] Amara: To 'pick up' cosmic dust on Earth you can go the
Antarctic ice sheets or to Greenland.
[02:29] Jonesey: while the ice is still there. mr bush is working on that
[02:30] worldeater left the chat room. (Ping timeout)
[02:30] Amara: Scientists extract dust from the deep-sea sediments
and polar ice and bring it to their laboratories and analyze it there.
[02:32] Amara: Also there were NASA campaigns to collect dust from
the stratosphere, using collectors located under the wings. I think
that most of the dust in the collections in Houston were acquired
that way.
[02:33] Amara: Yes, while the ice is still there! Mr. Bush.. well I
could rant about politics, but I won't ... (we have Berlusconi )
[02:38] Amara: OK, so how does one see traces of supernovae or
pre-solar system formation activities in the cosmic dust? (I feel
like a school teacher asking...)
[02:39] Jonesey: i guess the way its distributed?
[02:39] Jonesey: brb
[02:39] Amara: That's a clue, but the more direct clue is the
composition pieces of the dust grain themselves.
[02:40] Amara: Cosmic dust is dust grains and agreggates of dust
grains. Irregularly shaped and porous.
[02:41] Amara: The composition, size, and other properties depends on
where the dust is found.
[02:42] Amara: Typical Interplanetary Dust Particles (IDPs) are
fine-grained mixtures of thousands to millions of mineral grains.
[02:43] Amara: We can picture an IDP as a "matrix" of material with
embedded elements which were formed at different times and places in
the solar nebula and before our solar nebula's formation.
[02:44] Amara: Examples of embedded elements in cosmic dust are
called in acronym : GEMS, chondrules, and CAIs.
[02:46] Amara: The GEMS stand for Glass with Embedded Metal and
Sulfides. GEMS are likely either solar nebula or presolar
interstellar grains.
[02:48] Amara: Chondrules (from Greek chondros, grain), are round,
spheroid pieces suspended in the younger matrix of dust grain
material of meteorites and IDPs. Chondrules are thought to be among
the oldest material from the formation of the solar system. They
formed by a rapid heating within minutes or less. Some think a kind
[02:48] Amara: (oops!) of flash heating process in the solar nebula
like lightning.
[02:49] Amara: If you can get to a natural history museum like the
one in New York or in Vienna, you can see chondrules in their
meteorite collection.
[02:50] Amara: They are roundish, different-colored size pieces
embedded in the rest of the rock. It's cool to see our solar system
formation that way!
[02:52] Amara: CAIs are Calcium-Aluminum-Inclusions between the
chondrules in cosmic dust. CAIs were formed at much higher
temperatures than the temperatures at which chondrules formed, and
CAIs may have survived many multiple high-temperature events, while
most chondrules are the product of a single, transient melting event.
[02:54] Amara: OK, should I keep talking (I can go on to the supernova link)
[02:56] Amara: I guess that is yes.. (my you folks are quiet!)
[02:59] Amara: From the collected IDPs, about 60% are chondritic,
which is the link to our solar system formation. Out of those are
some rich in carbon and have abundances of H, C, N, and O.
[03:01] Amara: These are thought to be the most primitive material
because they contain volatile elements.
[03:02] Amara: Those with carbon etc show the link to us humans (i.e.
life), but the link to supernova is more indirect.
[03:04] Amara: The local interstellar environment around our solar
system is know from remote sensing observations (more than insitu
studies).
[03:06] Amara: If one observes in different directions to get a
line-of-sight, then we see that we are in a local cloud located at
the edge of the local bubble which was excavated by supernova
explosions in the neighboring star-forming regions of the
Scorpius-Centaurus and Orion Associations. There seem to have been
several supernovae at different times carving out our 'space'.
[03:07] MRA: Hi Amara. I've got a question: How has more recent
knowledge of dust's distribution and size in space effected the
plans/estimates of our ability to travel through space a very high
speeds?
[03:08] Amara: How high of speeds..?
[03:08] Amara: The present spacecraft flying have 'dust shields' but
that is for solar system speeds.
[03:09] MRA: Well, I'm thinking of both sub-relativistic speeds of
<10% light and also higher speeds >10% up to 99%c
[03:10] MRA: I suspect the answer will be different in these cases.
[03:10] Amara: My guess at your answer (I would need to ask a
spacecraft designer), is that we can shield for that.
[03:10] Amara: Yes, I suspect the shielding will be different for the
two cases!
[03:11] MRA: Interesting. Have the estimates for size and
distribution of the dust changed significantly enough to effect
design at all?
[03:12] Amara: Not generally, however the geostationary satellite
people are very interested.
[03:12] MRA: heh. I can imagine.
[03:13] Amara: In GEO, there was a dust collection experiment
collecting for 7 years (the GORID experiment, I can point you to more
references).
[03:13] MRA: From an L5 community perspective I would also suspect
high interest in the answers.
[03:14] Amara: Most of the dust however is too small to affect
spacecraft and people.
[03:14] MRA: Thx. Right now I'm asking from the point of view of
navigation hazard.
[03:14] Amara: For the bigger particles, yes, they are a hazard (cm sized).
[03:15] MRA: Have there been any studies as to the velocity of dust
in space (speed and direction)?
[03:15] Amara: In the solar system or outside?
[03:15] MRA: I'm asking about both, actually.
[03:16] Amara: In the solar system, the best person who would know is
Markus Landgraf, now at ESOC in Darmstadt.
[03:16] Amara: He did his PhD on that problem.
[03:16] MRA: It is tough to gather data from outside (except for
secondary evidence) without going outside, I would guess.
[03:17] Amara: Outside of the solar system, the studies useful for
this would be by P. Frisch.
[03:17] MRA: Woah. Perhaps his PhD is in English... googling.
[03:17] Amara: Markus Landgraf studied interstellar dust entering the
solar systm.
[03:18] Amara: You see there are different populations of dust in our
solar system (five or six)
[03:18] aloril left the chat room. (Client closed connection)
[03:19] MRA: That fellow has a whole bunch of publications.
[03:19] Amara: Markus studied mostly one population. (the
interstellar dust kind)
[03:20] Amara: There is a classic paper by my old advisor Eberhard
Gruen in 1985 in Icarus that empirically looked at all of the
populations of the solar system.
[03:21] Amara: That work is now being revised by Valeri Dikarev (in
Heidelberg). I don't recall if Valeri included speeds, but I can ask
him.
[03:22] MRA: My reason for asking is that the likely speed and
direction of dust effects spacecraft shield design.
[03:23] MRA: The sheild would have to cover a greater angle for more
uncertainty of dust's speed and direction.
[03:23] Amara: Yes, probably the whole spacecraft ?!
[03:24] MRA: Even when designing an active (versus passive) shield,
one has to predict the area of space to scan for 'incoming'.
[03:24] Amara: Cassini spacecraft designers did not think in such an
elegant way.
[03:25] Amara: When the spacecraft flew through the rings, the orbit
trajectory was the result of 10 years or more of debates...
[03:25] MRA: I suspect their budget did not allow it.
[03:26] Amara: That's true. They also placed the dust detector on the
opposite side of the imaging system.
[03:27] Amara: (so if the camera and the dust detector wanted to
observe the same object.. one was out of luck!)
[03:27] MRA: That's funny, in a sad sort of way.
[03:27] Amara: I know..
[03:28] MRA: I would have though a dust-detector would be
multi-directional, or at least have a very wide angle of 'aperture'.
[03:28] MRA: I am unfamiliar with how they went about detection in their case.
[03:29] Amara: It is wide angle but located on one part of a
spacecraft. So either the part of the spacecraft must rotate
continuously (like Galileo to scan 360 degrees) or else the whole
spacecraft must turn (like Cassini).
[03:30] Amara: One of the budget decisions early on for Cassini was
to remove the 'scanning continuously' capability.
[03:30] MRA: In my imagination I picture a circular matrix of
detection material, like a sponge the shape of a tennis ball, that
detects impacts - possibly two of the size, speed and direction.
[03:31] Amara: Therefore, all of the instruments suffer, and the
observation planning goes through a lengthy negotion.
[03:31] MRA: But I suspect Cassini has something much more primitive.
[03:31] Amara: But where and how is the circular matrix material placed?
[03:32] Amara: You see for the best observations it needs to see the
whole region of space.
[03:32] MRA: For 100% coverage I would place three at appropriate
angles from each other aay from the craft.
[03:32] MRA: *away
[03:33] MRA: Dust detectors of the future!
[03:33] Amara:
[03:34] MRA: What are your views of longevity, Amara. Specifically:
do you want the ability to live forever?
[03:34] Amara: Gruen is designing new dust detectors that are
multilayered. Keep a look out for a dust 'telescope' called Cosmic
DUNE.. He is promoting this both to ESA and NASA.
[03:34] Amara: Oh. longevity.. Yes, I want to live forever, or at
least as close to forever as possible.
[03:35] Amara: Why do you ask?
[03:35] Amara: (smiley goes here)
[03:36] Amara: Do you?
[03:36] MRA: Well, other than us chatting on #immortal, I am
interested in how you judge we will achieve (or near achieve) such an
aim, and when?
[03:36] MRA: (MRA: definitely wants the opportunity to live for ever,
and severally)
[03:37] Amara: Hmmm how I judge. The anti-aging crowd (Aubrey de Grey
for example) seem to be the investigators to watch.
[03:37] MRA: says: for those who don't know me, I am Michael Roy
Ames, currently president of the Singularity Institute - Canada
Branch.
[03:38] MRA: www.singinst.org/canada
[03:38] Amara: Ahh.. hi Michael...!
[03:38] MRA:
[03:38] Amara: I suggest to look at their research successes.
[03:39] MRA: They certainly have been getting some press lately.
[03:39] Amara: I can't judge how significant their successes are, but
yes, I agree that they have been getting some press.
[03:39] MRA: I have seen them "prodding" the establishment in the
right direction.
[03:39] Amara: This means that maybe some people are also paying them
for the research, which is a good thing!
[03:40] MRA: Hope they are successful, as it will improve the climate
for many related areas of research.
[03:40] Amara: Me too! Keep in touch with Bradbury too, he is
following that research probably closer than anyone.
[03:41] MRA: My partner, Barbie, is chair of the Alzhiemer's society
Vancouver-Island, and so much research could be better done if the
'public will' (for want of a better term) were there to make it
happen.
[03:42] MRA: (Bradbury who? Sorry, I know multiple Bradbury-named people)
[03:42] Amara: Robert Bradbury..
[03:42] MRA: Ah... yes, that Bradbury.
[03:42] MRA: I have communicated with him, on occasion.
[03:43] Amara: I think that the public will be alot more receptive to
anti-aging research if they understand that embedded in the process
are cured injuries and diseases.
[03:44] Amara: I think that it is a better approach to show how
these technologies can help people instead of a focus on the designer
aspects (even though we want the designer aspects too).
[03:45] MRA: Many of the currently 'hot-topic' diseases are closely
connected with aging. I suspect that the demographic changes
associated with the boom generations reaching retirement age will
help 'push' research at a faster pace.
[03:45] MRA: I hope so, anyway.
[03:46] Amara: I agree, especially in Europe, where it is clear that
we have much older populations with unsustainable pension systems.
[03:46] MRA: And what of your plans, Amara? What does the future
hold for you (short term).
[03:47] Amara: I'm trying to liberate myself from a dependence on the
Italian government for my salary. It is unliveable.
[03:48] Amara: I tried working extra jobs teaching at night, then
discovered that taxes took out a too-large chunk.
[03:48] Amara: I like the work and my group alot, but I need
something more solid under my feet. So I have several plans in
motion, but I don't know which one
[03:49] Amara: will succeed. I am trying to avoid moving to another
country since I have built something of a life here in Italy. It is
just the science support that is so stupifyingly bad.
[03:49] MRA: My sympathies about the low salary... I guess
"academics" are expected to live on bread and water there - or have
rich patrons perhaps?
[03:51] Amara: In general astronomy support is poor (all western
countries), and Italy is one end of that spectrum. It is the only
western country that still experiences a 'brain drain' for that
reason (I'm a rare scientist who immigrated in).
[03:51] MRA: Glad to hear that your living is going well - other than
the funding.
[03:51] Amara: The volcanoes are pretty :-).
[03:51] MRA: Do you have good internet connections where you are
living, or do you have to use the ones at work?
[03:53] Amara: Until July, I had a terrible internet connection at
home that dropped me every 30 seconds. You should have seen my trials
and tribulations on ebay! But since July, I am trying the only other
service available, which is really good.. wireless even. I'm in this
century now.
[03:53] MRA: Good suggestion about IEEE Spectrum magazine (on
FutureTag) by the way... it is rather good.
[03:54] Amara: Thanks to my dad for reminding me! I visited with him
in London before he continued his travels to Latvia. He brought with
him several issues of IEEE Spectrum. He knows I like it. After I
investigated the web site, I found a lot of articles that are
available for free.
[03:55] MRA: I recommend "A Hoist to The Heavens" by By Bradley Carl
Edwards to the room. http://www.spectrum....ents/index.html
[03:55] Nucleator joined the chat room.
[03:56] MRA: I imagine that the ordinary guest-chat-time has long
since expired, so...
[03:57] MRA: I thank you for joining #immortal on behalf of BJ.
[03:57] Amara: I think that I need to stop soon.. Do you continuing
without me? For more of dust you can go to Wikipedia (I have written
most of the articles there), and for more of me, you can go to the
maze at www.amara.com. You're welcome Michael and Imminst...!
[03:57] MRA: There are a number of people logging, and I'm sure the
chat will be passed around to those who want to read it.
[03:58] Nucleator: Sorry I missed the chat.
[03:58] Nucleator: Hi everyone.
[03:58] MRA: I will, reluctantly, be returning to my studies also.
The writing of papers is calling.
[03:58] MRA: Hi Nuc.
[03:58] Nucleator: I'll karaoke Kansas Dust in the Wind in Amara's honor.
[03:58] Nucleator: unless that would be upsetting
[03:58] MRA: Such a prince.
[03:58] Amara: Great.. I will do a copy of this window.. Ciao for now
(and thanks for the karaoke).




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