# Distance to the Sun using Venus transit

• ExoP
In summary: But if you want to find the AU from just one observation, you can use the concept of angular diameter. Essentially, you can measure the angular diameter of Venus as it appears to cross the Sun's disk during the transit. With this measurement, you can then use the formula: d = AU x tan(alpha), where d is the distance between Venus and the Sun, AU is the astronomical unit, and alpha is the angular diameter of Venus. From this, you can solve for the AU.
ExoP
Hi!

I was wondering if anyone of you know how to calculate the astronomical unit 1 AU, using data from a Venus transit and not using the parallax method. I already have all the data from the 2012 transit; the time it was in phase 1 when it contacts the Sun's disk and when it leaves the disk in phase 4 etc. The latitudes are all included. I haven't found anything helpful yet. So, if you have any idea or maybe a website that explains how to calculate this without the parallax method, please help.

Cheers!

This link has a clear elementary explanation of Halley's method proposed in 1716.

http://brightstartutors.com/blog/2012/the-transit-of-venus/

However this seems to be what you call the "parallax method" because it involves timing the same transit as seen from different locations on earth, essentially from different latitudes.

If you would like to help me understand what you are looking for (and help others in the same situation who might read the thread) you could be more explicit. Are you in fact looking for a method that does not involve making TWO separate observations of the same transit, from different latitudes on earth?
Are you looking for a method to find the AU from just your one observation?
I have a vague memory of having examined a calculation scheme of that type, but I'm not sure how it worked, someone else might know though.

Last edited:
That's right, I'm searching for a method that does not involve making TWO separate observations of the same transit.

How can you calculate is when there is an angle between the Venus transit, seen from us? Imagine the Sun, with Venus being a black dot. One of the dots are on the center of the Sun and the other slightly to the left in an angle under it. How should I consider this during my calculations? :S

Last edited:
ExoP said:
That's right, I'm searching for a method that does not involve making TWO separate observations of the same transit.

I don't think there's another way other than parallax.

## 1. How is the distance to the Sun measured using Venus transit?

The distance to the Sun is measured during the transit of Venus by using a method known as parallax. This involves observing the transit of Venus from two different locations on Earth and using the difference in the apparent position of Venus to calculate the distance to the Sun.

## 2. Why is Venus used to measure the distance to the Sun?

Venus is used to measure the distance to the Sun because it is one of the few planets in our solar system that transits in front of the Sun from Earth's perspective. This allows for accurate measurements to be taken during its transit.

## 3. How often does the Venus transit occur?

The Venus transit occurs in pairs, eight years apart, with over a century between each pair. This means that a Venus transit can be observed every 105-121 years.

## 4. What is the significance of measuring the distance to the Sun using Venus transit?

Measuring the distance to the Sun using Venus transit provides a more accurate value for the astronomical unit (AU), which is the average distance between the Earth and the Sun. This can then be used to measure distances to other celestial bodies in our solar system.

## 5. When was the last Venus transit and when is the next one expected?

The last Venus transit occurred in June 2012 and the next one is expected to occur in December 2117. This means that the next opportunity to measure the distance to the Sun using Venus transit is over a century away.

• Astronomy and Astrophysics
Replies
7
Views
1K
• Astronomy and Astrophysics
Replies
14
Views
1K
• Astronomy and Astrophysics
Replies
3
Views
2K
• Astronomy and Astrophysics
Replies
3
Views
991
• Astronomy and Astrophysics
Replies
6
Views
2K
• Astronomy and Astrophysics
Replies
3
Views
2K
• Astronomy and Astrophysics
Replies
17
Views
2K
• Astronomy and Astrophysics
Replies
7
Views
3K
• Astronomy and Astrophysics
Replies
2
Views
2K
• Astronomy and Astrophysics
Replies
1
Views
4K