Simultaneous transits of Venus and Mercury?

"Sam Wormley" wrote in message
...
Florian wrote:

Is it possible for Venus and Mercury to be transiting the sun at the
same
time?

How about a Venus/Mercury transit during a solar eclipse? Now that's got
to be rare.

;-)

-Florian

During a rainstorm! :-(

I should think the rainstorm woud somehow actually _increase_ the odds of
the double transit. At least during the thickest cloud cover.

Jim

AG
From: "Andrew Goldish"
AG
Subject: Simultaneous transits of Venus and Mercury?
AG
Date: Wed, 9 Jun 2004 20:40:36 -0400

In the present era, no, Assuming the planet orbits remain the
same, we can not get simultaneous transits. Transits occur when the
planet is at or near one of its two nodes, and Earth is there, too.
For Mercury this happens obly in May and November; Venus, June and
December. So right away we have at least a month discrepancy. Perhaps
a better inquiry would be: can we have transits of both planets in the
same year? A monthish apart?


AG Is it possible for Venus and Mercury to be transiting the sun at the same
AG time? Assuming the two orbits are independent of each other, it should
AG occur (though extremely rarely: millions of years between double transits
AG probably or something like that).

---
þ RoseReader 2.52á P005004

Is it reasonable to assume that the nodes of the two orbits would also
precess/change over the millennia, so that at some time in the future, the
nodes would occur on the same day? That way simultaneous transits might
just be possible. I agree chances must be millions to one against.

"JOHN PAZMINO" wrote in message
...
AG
From: "Andrew Goldish"
AG
Subject: Simultaneous transits of Venus and Mercury?
AG
Date: Wed, 9 Jun 2004 20:40:36 -0400

In the present era, no, Assuming the planet orbits remain the
same, we can not get simultaneous transits. Transits occur when the
planet is at or near one of its two nodes, and Earth is there, too.
For Mercury this happens obly in May and November; Venus, June and
December. So right away we have at least a month discrepancy. Perhaps
a better inquiry would be: can we have transits of both planets in the
same year? A monthish apart?


AG Is it possible for Venus and Mercury to be transiting the sun at the
same
AG time? Assuming the two orbits are independent of each other, it
should
AG occur (though extremely rarely: millions of years between double
transits
AG probably or something like that).

---
þ RoseReader 2.52á P005004

In article ,
wrote:
CeeBee writes:

Andrew Goldish wrote:

Is it possible for Venus and Mercury to be transiting the sun at the
same time? Assuming the two orbits are independent of each other, it
should occur (though extremely rarely: millions of years between
double transits probably or something like that).

You're right. What should be the problem preventing the two passing the
Sun simultaneuosly as seen from Earth?

The problem that currently prevents it is the non-alignment of the
nodes of Mercury's and Venus' orbits. I do not know their precession
rates, so I'm not in a position to say how long it might be before
the nodes are aligned. But for such a thing to happen, you'd need
(a) the nodes aligned to within some tight tolerance, (b) both
planets near their nodes at approximately the same time, (c) both
planets on the same side of the Sun, (d) the Earth aligned with both
planets at that time. I wouldn't be surprised if it's never happened
in the 4.5 billion year history of the Solar System.

I tried to guess at the very-very-long-term average frequency of these events,
assuming that Mercury and Venus aren't in an orbital resonance (so their
longitudes should be uncorrelated), and that the precession of their nodes is
at least fast enough that they've coincided many times over the life
of the solar system. And I guessed that Mercury's and Venus' nodes
needed to be within a one-degree span (half degree delta) for double
transits to be possible.

During periods when the nodes do nearly coincide, it looked like there
should be about three double transits, with these 5-or-6-hour-long
events at least partly overlapping, per million years. And if the
+/- 0.5 degree tolerance is right, those periods should be about 1/180th
of the time. So the long-term-average rate would be about
one per 60 million years, or maybe 80 times during the life of
the solar system, within a factor of a few.

Of course this kind of handwaving gives no clue about the *distribution*
of these events in time. I browsed a bit but couldn't find any on-line
references suggesting specific values for rates of node advance for
Mercury or Venus. There must be people (Gerald Sussmann?) who have
done very-long-term solar system integrations -- maybe their papers
would give statistics like these.

I'm crossposting to sci.astro.research too since this seems like
a sane thread so far, and one raising a question that its readers
might have something to say about...

Stuart Levy

In article ,
Mark HARDAKER wrote:

Is it reasonable to assume that the nodes of the two orbits would
also precess/change over the millennia, so that at some time in
the future, the nodes would occur on the same day?

It's very reasonable to assume that. As a matter of fact, the node
will coincide in about 10,000 years. However, then there won't be
any double transit. The next actual double transit will occur in
about 67,000 years, on 69,163 July 26 Dynamical Time (J Meeus & A
Vitagliano, Journal of the British Astronomical Association 114, 3,
2004).

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://www.stjarnhimlen.se/
http://home.tiscali.se/pausch/

"Stuart Levy" writes:

I browsed a bit but couldn't find any on-line references suggesting
specific values for rates of node advance for Mercury or Venus.

From the 1992 edition of the Explanatory Supplement to the
Astronomical Ephemeris, p. 316, we find for J2000 for mean equinox and
ecliptic of that date:
Mercury's node = 48.33° - 4.4630"/year
Venus's node = 76.68° - 9.9689"/year

However, the inclinations are not constant, so these are not
representative of the long-term behavior. For a double transit, you
would want to search for times when the inclination between the orbital
planes of Venus and Earth was a minimum. Then Venus transits would be
frequent enough that nodal alignments would be long-lasting, opening up
many opportunities for double transits.

Incidentally, I've added an appendix about transits seen from other
solar system planets to my paper on the black drop effect at
http://metaresearch.org/home/viewpoint/blackdrop.asp. -|Tom|-


Tom Van Flandern - Washington, DC - see our web site on replacement
astronomy research at http://metaresearch.org

Hi,

"Stuart Levy" writes:
I browsed a bit but couldn't find any on-line references suggesting

The Journal of the British Astronomical Association has an article on
this in its current issue (Vol 114 No. 3). It is not available online
however http://www.britastro.com/jbaa/114-3.htm

So summarise, they list three simeltaneous and near similtaneous
transits, though none of us will be witnessing them!:

13,425 (the year)
Sept 17th 0345 Venus
Sept 17th 1927 Mercury

69,163
July 26th 1647 Venus
July 26th 2031 Mercury

224,508
Mar 27th 2259 Venus
Mar 28th 0339 Mercury

specific values for rates of node advance for Mercury or Venus.

From the 1992 edition of the Explanatory Supplement to the
Astronomical Ephemeris, p. 316, we find for J2000 for mean equinox and
ecliptic of that date:
Mercury's node = 48.33° - 4.4630"/year
Venus's node = 76.68° - 9.9689"/year

However, the inclinations are not constant, so these are not
representative of the long-term behavior.

They mention this in their paper and state that to account for this they
used formulae from Simon J L et. al, `Numerical expressions for
precession formulae and mean elements for the Moon and the planets`
Astron.Astrophysics 282, 663-683 (1984) [
http://adsabs.harvard.edu/cgi-bin/np...6A...282..663S
]

I hope this is of help.

Cheers,
~Al
--
www.irishastronomy.org

Hi,

"Stuart Levy" writes:
I browsed a bit but couldn't find any on-line references suggesting

The Journal of the British Astronomical Association has an article on
this in its current issue (Vol 114 No. 3). It is not available online
however http://www.britastro.com/jbaa/114-3.htm

So summarise, they list three simeltaneous and near similtaneous
transits, though none of us will be witnessing them!:

13,425 (the year)
Sept 17th 0345 Venus
Sept 17th 1927 Mercury

69,163
July 26th 1647 Venus
July 26th 2031 Mercury

224,508
Mar 27th 2259 Venus
Mar 28th 0339 Mercury

specific values for rates of node advance for Mercury or Venus.

From the 1992 edition of the Explanatory Supplement to the
Astronomical Ephemeris, p. 316, we find for J2000 for mean equinox and
ecliptic of that date:
Mercury's node = 48.33° - 4.4630"/year
Venus's node = 76.68° - 9.9689"/year

However, the inclinations are not constant, so these are not
representative of the long-term behavior.

They mention this in their paper and state that to account for this they
used formulae from Simon J L et. al, `Numerical expressions for
precession formulae and mean elements for the Moon and the planets`
Astron.Astrophysics 282, 663-683 (1984) [
http://adsabs.harvard.edu/cgi-bin/np...6A...282..663S
]

I hope this is of help.

Cheers,
~Al
--
www.irishastronomy.org

although transits across Sol will always be rare and unique from Earth, i'd
like to believe multiple transits could be logistically-created from
inter-Solar system spaceflight before 13,425...maybe within the next century?

optimistically,
SaberStar

So summarise, they list three simeltaneous and near similtaneous
transits, though none of us will be witnessing them!:

13,425 (the year)
Sept 17th 0345 Venus
Sept 17th 1927 Mercury

69,163
July 26th 1647 Venus
July 26th 2031 Mercury

224,508
Mar 27th 2259 Venus
Mar 28th 0339 Mercury

although transits across Sol will always be rare and unique from Earth, i'd
like to believe multiple transits could be logistically-created from
inter-Solar system spaceflight before 13,425...maybe within the next century?

optimistically,
SaberStar

So summarise, they list three simeltaneous and near similtaneous
transits, though none of us will be witnessing them!:

13,425 (the year)
Sept 17th 0345 Venus
Sept 17th 1927 Mercury

69,163
July 26th 1647 Venus
July 26th 2031 Mercury

224,508
Mar 27th 2259 Venus
Mar 28th 0339 Mercury