Conjunction of Venus and Sun a rare event

  • Thread starter Thread starter Kerrie
  • Start date Start date
  • Tags Tags
    Sun Venus
Click For Summary

Discussion Overview

The thread discusses the conjunction of Venus and the Sun, particularly focusing on the rare event of a transit of Venus, which occurred on June 8th, 2004. Participants explore the implications of this event, its historical significance, and the mechanics of how such transits occur, including their frequency and observational details.

Discussion Character

  • Exploratory
  • Technical explanation
  • Historical
  • Debate/contested

Main Points Raised

  • Some participants express confusion about the terminology, noting that a conjunction occurs regularly when Venus and Earth align, while transits are much rarer events.
  • One participant clarifies that a transit of Venus does not require it to pass through the center of the Sun, but must occur near its node during a conjunction.
  • Another participant mentions that transits of Venus occur in pairs, referencing historical observations and their significance in determining the size of the solar system.
  • There is a discussion about the historical expeditions to observe transits, including those led by James Cook and Jesuit missionaries, highlighting their contributions to astronomy.
  • A participant raises a question about how the astronomical unit (AU) was calculated based on the timing of the transit, seeking clarification on the methodology involved.

Areas of Agreement / Disagreement

Participants generally agree on the rarity of transits of Venus and their historical importance, but there is some disagreement regarding the terminology and the specifics of how the AU was calculated from transit observations. The discussion remains unresolved on the latter point.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the observational techniques and the specific calculations involved in determining the AU from transit timings, which are not fully explored.

Who May Find This Useful

This discussion may be of interest to those studying astronomy, historical methods of astronomical measurement, and the significance of planetary transits in understanding the solar system.

Kerrie
Staff Emeritus
Gold Member
Messages
843
Reaction score
14
I won't get to see this rare event in my part of the U.S. :frown: However, I still wanted to share with you all this conjunction of Venus and the Sun June 8th, 2004.

http://sunearth.gsfc.nasa.gov/eclipse/transit/venus0412.html
 
Last edited by a moderator:
Astronomy news on Phys.org
I'm confused what exactly is going on here...

Venus is passing through the center of the Sun as viewed from Earth?

Since we're near the spring equinox, I'd guess that means that Venus is near its node as well... from the pictures on that website, it looks like the descending node.
 
enigma said:
I'm confused what exactly is going on here...

Venus is passing through the center of the Sun as viewed from Earth?

Since we're near the spring equinox, I'd guess that means that Venus is near its node as well... from the pictures on that website, it looks like the descending node.

A transit is any time Venus crosses any part of the body of the Sun as seen from Earth ( It doesn't have to pass through the center), And yes, it only occurs when Venus is near its node during a conjunction.)

I was also slightly confused by the title of this thread since it appeared to imply that a conjunction with Venus was a rare event. A conjunction occurs when ever Venus and the Earth pass each other in their orbits; this occurs fairly regularly. Transits are much rarer.
 
Sorry Janus, I used "conjunction" then as a wrong term? But yes, the transit of Venus passing directly in front of the sun is a rare event...the last time it happened was in 1882, and the even more weird thing about this is Venus is again expected to have a transit in 2004.
 
I believe transits of Venus occur in pairs. At least I know there was a pair of them in the 1760s, which was the occasion of heroic expoditions to observe them. At that time they were the only way to determine the actual size of the solar system.
 
What does this mean in terms of someone wanting to observe the event?
 
Those Venus transients certainly do come in pairs, each separated about eight years:

http://sunearth.gsfc.nasa.gov/eclipse/transit/catalog/VenusCatalog.html

and you can see it in Europe and the Eastern US at sunrise.
 
Last edited by a moderator:
selfAdjoint said:
I believe transits of Venus occur in pairs. At least I know there was a pair of them in the 1760s, which was the occasion of heroic expoditions to observe them. At that time they were the only way to determine the actual size of the solar system.

here's a webpage with some original drawings from the James Cook
expedition to observe the transit of 1769. Cook's team observed the transit from Tahiti-----the page has some quotes from Cook's account to the Royal Socieity and some sketches of the temporary observatory they set up in Tahiti and their instruments.

http://www.jcu.edu.au/school/mathphys/astronomy/jamescook2.shtml

apparently it was Edmund Halley (of comet fame) who proposed, in 1716, that timing a transit of venus could serve to determine the AU. another page I happened to see said:

"Edmund Halley, in 1716, suggested that the distance from the Sun to the Earth could be calculated by timing the transit of Venus across the face of the Sun. "
 
Last edited by a moderator:
The Jesuits also made expeditions, I think they went to the Pacific coast of North America, to the California missions run by the Fransiscans. There was no love lost. Apparently the track of the transit went from the South Pacific up across California and north into Canada, somewhere around the west end of Lake Superior. There was a book about all this, called The Transit of Venus and I'm posting from dim memories of reading it.
 
  • #10
selfAdjoint said:
... There was a book about all this, called The Transit of Venus and I'm posting from dim memories of reading it.

do you happen to recall how (according to Halley's suggestion apparently) they were to calculate the AU from timing transit?

To simplify let's assume the transit is across center of sun's disk so it describes a solar diameter

I think that by measuring angular size of sun's disk they could tell that
one AU is around 107 times the solar diameter, or 108 (we don't have to be accurate I just want to see in a rough way how they'd calculate)

So the transit takes some time (like 8 hours?) that they measure.

How would they calculate the AU from that?

I suppose they could observe the angular size of Venus at the same time (it would be at a maximum I suppose) and i wonder if that information was also used in some way in the calculation of the AU.

Maybe its so obvious to most people that the derivation doesn't even need to be explained but I don't immediately see it.
 
  • #11
even google recognized this event :P
 

Similar threads

Undergrad Visibility of Venus during the march equinox
  • · Replies 3 ·
Replies
3
Views
4K
Undergrad If a planet struck the sun, would fragments be blasted out?
  • · Replies 7 ·
Replies
7
Views
3K
Venus passes in front of our sun
  • · Replies 9 ·
Replies
9
Views
3K
Undergrad How Big of an Object Orbiting Closer to the Sun Than Earth Could Be Overlooked?
  • · Replies 17 ·
Replies
17
Views
5K
High School Is This a Solar Flare?" - Investigating Possible Phenomenon
  • · Replies 2 ·
Replies
2
Views
3K
High School Could a brown dwarf passing through our solar system ignite Jupiter?
  • · Replies 40 ·
2
Replies
40
Views
8K
MHB Venus - Transit of VenusWhat did I capture during the recent transit of Venus?
  • · Replies 2 ·
Replies
2
Views
2K
  • Sticky
Stargazing How Can You Improve Your Amateur Solar Imaging Techniques?
  • · Replies 311 ·
11
Replies
311
Views
58K
Stargazing Solar Activity and Space Weather Update thread
  • · Replies 460 ·
16
Replies
460
Views
65K
Stargazing How can I safely view a solar eclipse?
  • · Replies 1 ·
Replies
1
Views
5K