2 Questions for Astronomers

In message , Roger Stokes
writes
"BRAINIAC" wrote in message
...
A) Our sun is just an avergage star.

There are 71 stars within 20 light years of the solar system, of which only
4
(Alpha Centauri A, Sirius, Procyon, and Altair) are brighter than the sun.
Most are M dwarfs. Here's the list (from the hipparcos catalog)

TYPE DISTANCE (LY) MAGNITUDE Name
HIP70890 M5Ve 4.2 +/- 0.00 11.0 Alpha Centauri C (Proxima)
HD128621 K1V 4.4 +/- 0.00 1.4 Alpha Centauri B
HD128620 G2V 4.4 +/- 0.01 -0.0 Alpha Centauri A (Rigil Kent)
HIP87937 sdM4 6.0 +/- 0.04 9.5 Barnard's star

Isn't one of the better-known ones missing from that list?
Wolf 359 was a TV star about 20 years before it featured in "Star Trek:
TNG" (It's the title of an "Outer Limits" story)
--
"It is written in mathematical language"

(BRAINIAC) wrote in message ...

[snip]

B) The earth will end when the sun burns out, and the orbit of earth
will come close to or be enveloped by the edge of the sun, thereby
burning it out of existence.

The sun will burn out in about 5 to 7 billion years.

It's debatable that the future, red-giant Sun will become large enough
to envelop the Earth's orbit. The Sun is not so massive as, say,
Antares. The Sun is expected to expand, but perhaps not this far.
Nevertheless, here's something else to keep you awake at night... :^)

While it may take 5-7 billion years for the gas envelope of the Sun to
swallow Earth, our planet will be uninhabitable long before that.
There will be substantial global warming well before the demise of
Earth. One recent study estimated that it will become hot enough to
evaporate Earth's oceans only one billion years hence. As the
atmosphere heats, we expect more rainfall. Atmospheric CO2 depletion
due to rainfall-mediated sequestering in carbonate rocks may happen as
soon as 500 million years from now.

http://news.bbc.co.uk/1/hi/sci/tech/...000/649913.stm

--
John J. Ladasky Jr., Ph.D.
Department of Biology
Johns Hopkins University
Baltimore MD 21218
USA
Earth

(BRAINIAC) wrote in message ...

[snip]

B) The earth will end when the sun burns out, and the orbit of earth
will come close to or be enveloped by the edge of the sun, thereby
burning it out of existence.

The sun will burn out in about 5 to 7 billion years.

It's debatable that the future, red-giant Sun will become large enough
to envelop the Earth's orbit. The Sun is not so massive as, say,
Antares. The Sun is expected to expand, but perhaps not this far.
Nevertheless, here's something else to keep you awake at night... :^)

While it may take 5-7 billion years for the gas envelope of the Sun to
swallow Earth, our planet will be uninhabitable long before that.
There will be substantial global warming well before the demise of
Earth. One recent study estimated that it will become hot enough to
evaporate Earth's oceans only one billion years hence. As the
atmosphere heats, we expect more rainfall. Atmospheric CO2 depletion
due to rainfall-mediated sequestering in carbonate rocks may happen as
soon as 500 million years from now.

http://news.bbc.co.uk/1/hi/sci/tech/...000/649913.stm

--
John J. Ladasky Jr., Ph.D.
Department of Biology
Johns Hopkins University
Baltimore MD 21218
USA
Earth

(John Ladasky) writes:

(BRAINIAC) wrote in message ...

[snip]

B) The earth will end when the sun burns out, and the orbit of earth
will come close to or be enveloped by the edge of the sun, thereby
burning it out of existence.

The sun will burn out in about 5 to 7 billion years.

It's debatable that the future, red-giant Sun will become large enough
to envelop the Earth's orbit. The Sun is not so massive as, say,
Antares. The Sun is expected to expand, but perhaps not this far.

Remember that red giants have very extended tenuous "atmospheres,"
which exert drag on planets both directly and via tidal drag, and also
that they lose mass at prodigious rates. Current simulations are not yet
good enough to resolve whether the Earth gets suck into the red-giant Sun
via drag, or escapes by spiraling away as the Sun loses mass; some studies
show the former, others the latter.


Nevertheless, here's something else to keep you awake at night... :^)

While it may take 5-7 billion years for the gas envelope of the Sun to
swallow Earth, our planet will be uninhabitable long before that.
There will be substantial global warming well before the demise of
Earth. One recent study estimated that it will become hot enough to
evaporate Earth's oceans only one billion years hence. As the
atmosphere heats, we expect more rainfall. Atmospheric CO2 depletion
due to rainfall-mediated sequestering in carbonate rocks may happen as
soon as 500 million years from now.

http://news.bbc.co.uk/1/hi/sci/tech/...000/649913.stm

I can't become seriously concerned about _ANY_ of these domsday scenarios,
as they involve timescales over a thousand times longer than the hominidae
have existed as a genus, and hundreds of thousands of times longer than the
paltry few tens of millenia H. sap. has existed as a species. By the time
_ANY_ of these scenarios come to pass, our species will either have been
superceded by the remote and barely recognizable descendants of whatever
diverse species we will evolve into, perhaps as we spread to the stars,
or it will have been long extinct. Either way, it's somebody else's problem !!! :-/


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(John Ladasky) writes:

(BRAINIAC) wrote in message ...

[snip]

B) The earth will end when the sun burns out, and the orbit of earth
will come close to or be enveloped by the edge of the sun, thereby
burning it out of existence.

The sun will burn out in about 5 to 7 billion years.

It's debatable that the future, red-giant Sun will become large enough
to envelop the Earth's orbit. The Sun is not so massive as, say,
Antares. The Sun is expected to expand, but perhaps not this far.

Remember that red giants have very extended tenuous "atmospheres,"
which exert drag on planets both directly and via tidal drag, and also
that they lose mass at prodigious rates. Current simulations are not yet
good enough to resolve whether the Earth gets suck into the red-giant Sun
via drag, or escapes by spiraling away as the Sun loses mass; some studies
show the former, others the latter.


Nevertheless, here's something else to keep you awake at night... :^)

While it may take 5-7 billion years for the gas envelope of the Sun to
swallow Earth, our planet will be uninhabitable long before that.
There will be substantial global warming well before the demise of
Earth. One recent study estimated that it will become hot enough to
evaporate Earth's oceans only one billion years hence. As the
atmosphere heats, we expect more rainfall. Atmospheric CO2 depletion
due to rainfall-mediated sequestering in carbonate rocks may happen as
soon as 500 million years from now.

http://news.bbc.co.uk/1/hi/sci/tech/...000/649913.stm

I can't become seriously concerned about _ANY_ of these domsday scenarios,
as they involve timescales over a thousand times longer than the hominidae
have existed as a genus, and hundreds of thousands of times longer than the
paltry few tens of millenia H. sap. has existed as a species. By the time
_ANY_ of these scenarios come to pass, our species will either have been
superceded by the remote and barely recognizable descendants of whatever
diverse species we will evolve into, perhaps as we spread to the stars,
or it will have been long extinct. Either way, it's somebody else's problem !!! :-/


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Gordon D. Pusch) wrote in message ...

I can't become seriously concerned about _ANY_ of these domsday scenarios,
as they involve timescales over a thousand times longer than the hominidae
have existed as a genus, and hundreds of thousands of times longer than the
paltry few tens of millenia H. sap. has existed as a species.

That's why I appended the smiley to the end of this statement:

(John Ladasky) writes:
Nevertheless, here's something else to keep you awake at night... :^)

And yes, these are disasters which are, in evolutionary time,
extremely far off. I made similar remarks to yours when this story
first appeared:

http://groups.google.com/groups?hl=e...rp1.deja.co m

--
John J. Ladasky Jr., Ph.D.
Department of Biology
Johns Hopkins University
Baltimore MD 21218
USA
Earth

(Gordon D. Pusch) wrote in message ...

I can't become seriously concerned about _ANY_ of these domsday scenarios,
as they involve timescales over a thousand times longer than the hominidae
have existed as a genus, and hundreds of thousands of times longer than the
paltry few tens of millenia H. sap. has existed as a species.

That's why I appended the smiley to the end of this statement:

(John Ladasky) writes:
Nevertheless, here's something else to keep you awake at night... :^)

And yes, these are disasters which are, in evolutionary time,
extremely far off. I made similar remarks to yours when this story
first appeared:

http://groups.google.com/groups?hl=e...rp1.deja.co m

--
John J. Ladasky Jr., Ph.D.
Department of Biology
Johns Hopkins University
Baltimore MD 21218
USA
Earth

In article ,
Jonathan Silverlight writes:
Isn't one of the better-known ones missing from that list?
Wolf 359 was a TV star about 20 years before it featured in "Star Trek:
TNG" (It's the title of an "Outer Limits" story)

Good catch! According to SIMBAD, Wolf 359 is at 2.35 pc = 7.67 light
years. At V=13.5, it is too faint for Hipparcos. Its distance would
make it the fifth nearest star after the Sun unless there are others
missing. The list in _AQ_ also appears to be a Hipparcos list, so it
too will be incomplete for faint stars.

There's probably a way to search SIMBAD or another archive to create
a distance-limited list, but unfortunately, I don't know how. I've
never needed to do it.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

In article ,
Jonathan Silverlight writes:
Isn't one of the better-known ones missing from that list?
Wolf 359 was a TV star about 20 years before it featured in "Star Trek:
TNG" (It's the title of an "Outer Limits" story)

Good catch! According to SIMBAD, Wolf 359 is at 2.35 pc = 7.67 light
years. At V=13.5, it is too faint for Hipparcos. Its distance would
make it the fifth nearest star after the Sun unless there are others
missing. The list in _AQ_ also appears to be a Hipparcos list, so it
too will be incomplete for faint stars.

There's probably a way to search SIMBAD or another archive to create
a distance-limited list, but unfortunately, I don't know how. I've
never needed to do it.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

On Wed, 22 Oct 2003 21:25:25 GMT, (Steve
Willner) wrote:

. . . .

Good catch! According to SIMBAD, Wolf 359 is at 2.35 pc = 7.67 light
years. At V=13.5, it is too faint for Hipparcos. Its distance would
make it the fifth nearest star after the Sun unless there are others
missing. The list in _AQ_ also appears to be a Hipparcos list, so it
too will be incomplete for faint stars.

. . . .

Zeta Tuc also appears to be missing.

Dan, ad nauseam