Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v09_4/v9_449.txt

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Date: Sun, 21 May 89 03:16:37 -0400 (EDT)
Subject: SPACE Digest V9 #449

SPACE Digest                                      Volume 9 : Issue 449

Today's Topics:
               Andromeda Strain
              Re: Magellan & SRB exhaust
   Re: Asteroids and Dinosaurs (was Re: asteroid almost hits earth)
            Re: Star Dying out...
         Re: Sun's invisible partner NEMESIS
         Re: Sun's invisible partner NEMESIS
         Re: Sun's invisible partner NEMESIS
              Re: Magellan & SRB exhaust
               The late NEMESIS Theory
            Giotto to be woken up
----------------------------------------------------------------------

Date: Thu, 18 May 89 10:58 EST
From: [e-mail]
Subject: Andromeda Strain

    In the *movie* version it was not an asteroid, it was a space
    probe.  It has been a long time since I saw it, but there was I
    think the implication of a possibility that the probe was lanched
    by the military in order to collect extraterrestrial material.
    Also, It didn't decompose plastics at all.  It caused blood to
    coagulate comletely, which kind of slowed the heart down.  In the
    end it was found that it didn't do well in an oxygen environment.
    However, all of the high-tech machines broke down, for stupid reasons
    that the movie maker thought representative of engineering narrow
    mindedness, and so it took them much too long to figure this out.

    By the way, I do think it is possible that an extraterrestrial bug
    could cause problems on earth, although very unlikely. ~rI am thinking
    that something couldevolve to live in an incredibly harsh and spartan
    extraterrestrial environment by being able to extract energy from
    almost any kind of molecule.  }iConsider for example, molds and
    such.  They will grow on any kind of decomposing organic matter.
    They are not in any sense host-specific.  Now imagine one that grew
    much more rapidly in a suitable environment, say inside the lungs.

    Chris Eliot

    Umass/Amherst

    You can post this to the net, but don't expect me to defend any
    of it.

------------------------------

Date: 18 May 89 22:29:57 GMT
From: terra![e-mail]  (Brent Callaghan)
Subject: Re: Magellan & SRB exhaust

In article <[e-mail]>, [e-mail] (Andy Clews) writes:
> Also, (rather naive question), would the shuttle have been "showered"
> with any of the impurities from the Magellan solid motor exhaust at burn
> time, even though it was obviously a long distance from it?

It seems that damage to Shuttle windows from high speed particles
of sold exhaust is a real concern.  According to the Space Shuttle
Operator's Manual, the orbiter turns its windows away and the
crew watch the burn with the TV camera on the elbow of the
manipulator arm.

Made in New Zealand -->  Brent Callaghan  @ Sun Microsystems
             uucp: sun!bcallaghan
             phone: [phone]

------------------------------

Date: 18 May 89 13:16:50 GMT
From: mcvax!inria!irisa![e-mail]  (saouter yannick)
Subject: Re: Asteroids and Dinosaurs (was Re: asteroid almost hits earth)

In article <[e-mail]>, [e-mail] (Ethan Tecumseh Vishniac) writes:
> It is also true that this is not the most dramatic mass extinction in the
> fossil record.

Such collisions occurs about every 50 000 000 years and I've heard that others
species have disappeared as suddenly as the dinosaurs did, so earlier
collisions might be the cause for that, too.

Does anyone knows others example of strange disappearance ?

------------------------------

Date: 18 May 89 13:25:06 GMT
From: amdahl!nsc!taux01![e-mail]  (Amos Shapir)
Subject: Re: Star Dying out...

Have you heard about things called "planets", like, Venus?

They actually *move*!

--
    Amos Shapir                [e-mail]
National Semiconductor (Israel) P.O.B. 3007, Herzlia 46104, Israel
Tel. [phone]  TWX: 33691, fax: [phone]
34 48 E / 32 10 N            (My other cpu is a NS32532)

------------------------------

Date: 18 May 89 14:50:35 GMT
From: cs.utexas.edu!ut-emx![e-mail]  (Ed Nather)
Subject: Re: Sun's invisible partner NEMESIS

In article <[e-mail]>, [e-mail] (Daniel Evans) writes:
>     A couple of years back, I had read some accounts about a tiny (non-
> identical) "twin" of our sun, which swings by every few million years or so.
> Someone referred to it as "Nemesis".
>
>     How much evidence is there supporting this theory?

None.

>  What are the details?

There aren't any.

> What kind of star is it?

It is a mythical star.

> How did they decide what its path is?

They were trying to explain "periodic" mass extinctions in the fossil record
by invoking comets to smash the earth and create a "gravitational winter" by
ruining the earth's ecology, on a regular basis.  The "periodicity" was, at
best, suspect, but why not try?  They invoked the mythical "Oort cloud" of
comets that supposedly (and invisibly) surrounds the solar system, and placed
the mythical "Nemesis" in an orbit that would perturb them periodically, thus
raining destruction on our unsuspecting planet and its inhabitants.

> Is it visible through a telescope?

No.

>  Was this just a trendy theory that got tossed out after a while?

Yes.

>     My wife's sixth-grade students want to know...

Teach them the difference between theory and observation, and you'll do
them a life-long favor.

--
Ed Nather
Astronomy Dept, U of Texas @ Austin

------------------------------

Date: 18 May 89 18:40:00 GMT
From: janus![e-mail]  (Blake Philip Wood)
Subject: Re: Sun's invisible partner NEMESIS

In article <[e-mail]> [e-mail] (Daniel Evans) writes:
>
>Someone referred to it as "Nemesis".
>    How much evidence is there supporting this theory?

Prof. Richard A. Muller, here at Berkeley, is the originator of this idea.
As of a year ago he had a project going to actively look for it.  About a
year ago he wrote a book on the subject: "Nemesis".  I suggest you read
it for more details.  Contrary to other's postings, I don't think this is
a dead or discredited theory at all.


                              Blake P. Wood
                              U.C. Berkeley, EECS
                              Plasmas and Non-Linear Dynamics
                              [e-mail]

------------------------------

Date: 18 May 89 15:20:37 GMT
From: cwjcc!mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Sun's invisible partner NEMESIS

In article <[e-mail]> [e-mail] (Daniel Evans) writes:
>    A couple of years back, I had read some accounts about a tiny (non-
>identical) "twin" of our sun, which swings by every few million years or so.
>Someone referred to it as "Nemesis".

Last I heard, this idea was no longer taken seriously by most people.  It
appears unlikely that Nemesis's orbit would be stable against perturbations
by other stars over billions of years.  And the evidence for mass extinctions
occurring every N million years -- which is what Nemesis was supposed
to explain -- is not all that strong.  (Mass extinctions, yes, but not on
a clockwork-regular schedule.)

Definitely proving or disproving the idea is difficult, but it no longer
looks like a good bet.
--
Subversion, n:  a superset     |     Henry Spencer at U of Toronto Zoology
of a subset.    --J.J. Horning | uunet!attcan!utzoo!henry [e-mail]

------------------------------

Date: 18 May 89 14:03:55 GMT
From: mcdchg!illusion![e-mail]  (Marcus Hall)
Subject: Re: Magellan & SRB exhaust

In article <[e-mail]> [e-mail] (Stuart Warmink) writes:
>   ... that it exactly why the Shuttle turns its undersurface
>   towards where the probe/satellite starts its burn. The worry is that
>   exhaust particles could damage or dirty the orbiter's windows.

Are the windows considered more critical than the bottom tiles?  I guess they
are possibly more fragile, but the bottom tiles experience much higher
temperatures than the top surfaces.  I guess that we know that even with some
of the bottom tiles missing, the orbiter doesn't suffer too much damage, so
I guess that turning the bottom to the burn makes sense, but it doesn't seem
to be clearly the obvious thing to do.

marcus hall

------------------------------

Date: 18 May 89 22:33:46 GMT
From: cfa![e-mail]  (Bill Wyatt)
Subject: The late NEMESIS Theory

I had to comment on the following exchange. I find Ed's response to be
uninformative (and even snide) despite being mostly factually correct.

From article <[e-mail]>, by [e-mail] (Ed Nather):
> In article <[e-mail]>, [e-mail] (Daniel Evans) writes:
>>     A couple of years back, I had read some accounts about a tiny (non-
>> identical) "twin" of our sun, which swings by every few million years or so.
>> Someone referred to it as "Nemesis".
>>
>>     How much evidence is there supporting this theory?
>
> None.

Not exactly correct. Maybe the evidence is poor, but you should mention
what it is: extinction intervals and astroblem dating. Both are vaguely
consistent with periodic extinctions, but the dating of astroblems is
pretty vague, and the degree of extinctions depends a lot on interpretation.
The statistics of small samples prevents any conclusions, IMHO.

>>  What are the details?
>
> There aren't any.

There are lots of details - the depth and extent of one or more iridium
layers, the possible orbits of a NEMESIS type object, what it would
look like (i.e. how to detect it), the dating methods referred to above,
etc.

>
>> What kind of star is it?
>
> It is a mythical star.

Very descriptive. You might have said that if it existed and had not
been detected, it would likely be in the southern hemisphere, that it
would be a faint red dwarf, massing at most 15% of the Sun, and that
it would be most detectable as an infrared source. To my mind, IRAS
would have been the most likely way to find it, and it is this failure
that was the telling blow (not that the other evidence wasn't pretty
bad anyway).

>
>> How did they decide what its path is?
>
> They were trying to explain "periodic" mass extinctions in the fossil record
> by invoking comets to smash the earth and create a "gravitational winter" by
> ruining the earth's ecology, on a regular basis.  The "periodicity" was, at
> best, suspect, but why not try?  They invoked the mythical "Oort cloud" of
> comets that supposedly (and invisibly) surrounds the solar system, and placed
> the mythical "Nemesis" in an orbit that would perturb them periodically, thus
> raining destruction on our unsuspecting planet and its inhabitants.

The `mythical Oort cloud' is on much better theoretical and
observational ground that this denigration would imply. The recent
work indicates that most comets may be closer to the Sun (Uranus -
Neptune region) than was thought, and that we don't, for interesting
dynamical reasons, see them perturbed into the inner solar system as
often as those farther out.

Granted, the path is entirely a result of trying to generate a
periodicity while making it hard to see or find the `comet perturber'.
None of it is direct observation, just a set of deductions from an
initial postulate.

>> Is it visible through a telescope?
>
> No.
>
Well, it ought probably to have been detectable by IRAS. Maybe.

>>  Was this just a trendy theory that got tossed out after a while?
>
> Yes.
>
No argument here.

>>     My wife's sixth-grade students want to know...
>
> Teach them the difference between theory and observation, and you'll do
> them a life-long favor.
>
Absolutely.

One of the things that always bothered me about this whole `NEMESIS
did/didn't kill the dinosaurs' thing was that most people didn't
understand how the chain of reasoning went on NEMESIS, and that even
if some of the more exotic inferences were unlikely, that didn't rule
out other components of the scenario.

For example, NEMESIS was postulated to explain a possible
*periodicity* of extincitions. If it doesn't exist, that doesn't mean
that a comet might not have killed off the dinosaurs, just that
extinctions aren't periodic after all. It might even be that *all*
such extinctions were caused by comets, but just that they aren't
really periodic.

And, most assuredly, if a comet had nothing to do with the K-T
extinction, that doesn't mean that comets and other objects don't
occasionally hit the Earth.

Several things would have to be verified for the entire NEMESIS theory
to be accepted. A short list, off the top of my head:

1) NEMESIS has to be located.
2) It has to have a stable enough orbit to have been around for
   about 1 GY and five or six orbits, maybe more.
3) The outer Oort cloud must be perturbed by NEMESIS.
4) One or several comets must hit the Earth per cycle, depositing
   Ir or some other tracer.
5) The iridium layer(s) must be of extraterrestrial origin.
6) There must be an Ir or other tracer layer at every extinction boundary.
7) Almost all (some random interlopers allowed) Ir layers around the
   world should date to an extinction event.
8) The extinctions must happen very quickly.
9) The mechanism by which a comet impact or impacts actually kills large
   animals but not small must be understood. (also sea versus land animals.)
10) No more likely explanation must be available.

I don't think any of (1)-(9) are completely accepted, and most are not
accepted at all, except maybe (5). Note however, that should (1) and
(2) occur, the others become much more reasonable.
Bill Wyatt, Smithsonian Astrophysical Observatory
    UUCP :  {husc6,cmcl2,mit-eddie}!harvard!cfa!wyatt
    ARPA:   [e-mail]
    SPAN:   cfa::wyatt                 BITNET: wyatt@cfa

------------------------------

Date: 17 May 89 17:07:57 GMT
From: mcvax!ukc!etive!hwcs![e-mail]  (Adrian Hurt)
Subject: Giotto to be woken up

A BBC TV programme, "Tomorrow's World", reported that the Giotto probe is to
be reawakened. Tests have shown that despite its battering from Halley's
Comet, 60% of the craft is still working, and there is still fuel on board.
The idea is that in July 1992, Giotto will intercept another comet. I have no
idea how that comet's name is spelt, but it sounded like Grig-Skellerup.

Anyone want to supply more detail, and in particular the correct spelling of the
comet's name?

 "Keyboard? How quaint!" - M. Scott

 Adrian Hurt                 |    JANET:  [e-mail]
 UUCP: ..!ukc!cs.hw.ac.uk!adrian     |  ARPA:   [e-mail]

------------------------------

End of SPACE Digest V9 #449
*******************