Assessment of astronomical numbers like those of Proxima Centauri

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In summary, the conversation discusses the accuracy of an image depicting the size and scale of planets in our solar system. The image accurately shows the relative sizes of the planets and the Sun, with all the planets fitting between the Earth and Moon. The conversation also mentions the difficulty of interstellar space travel and the possibility of seeing Jupiter and Saturn's full disks at the same time from Earth. Overall, the image is considered to be fairly accurate in depicting the relative sizes of the planets and the Sun.
  • #1
cjackson
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Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).



Is the image accurate?
 
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  • #2
cjackson said:
Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).
OK. What's your point?
 
  • #3
phinds said:
OK. What's your point?
Apart from that, OP is using way too many significant digits. You cannot say that 4.2 lightyears is 24,673,274,438,400 miles. There just isn’t sufficient precision for 12 significant digits (which would be essentially knowing your length at the precision of an atom...
 
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  • #4
cjackson said:
Is the image accurate?

Aren't Jupiter and Saturn slightly further apart than that?
 
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  • #5
phinds said:
OK. What's your point?
My point is wanting to know the accuracy of the numbers in the op.
 
  • #6
PeroK said:
Aren't Jupiter and Saturn slightly further apart than that?
Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
 
  • #7
cjackson said:
Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
Well - what are the radii of the planets and the Sun? Wikipedia is a good enough source for straightforward stuff like this, and they usually cite nasa.gov links if you want to check. And how big is each of the planets and the Sun in the image? Do you know how to work out the scale factor?
 
  • #8
cjackson said:
Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).

I'm not sure I see the purpose of this calculation. The Sun and Proxima Centauri are moving relative to each other, but not at the speed you quote. The closest approach is calculated to be 3.1 light years about 27,000 years from now. You can read about here:

https://en.wikipedia.org/wiki/Proxima_Centauri

You could also calculate how long the Voyager spacecraft would take to reach Proxima Centauri and ponder the immense difficulty of interstellar space travel.
 
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  • #9
cjackson said:
Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
What do you get when you add up the diameters of those 4 planets and compare the result to the radius of the moon's orbit?
 
  • #11
They can't be to scale.

The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
 
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  • #12
Mikestone said:
They can't be to scale.

The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
That's not what "to scale" means here. The fact that all the planets are lined up like that is understood to be bogus. It's the relative sizes that are the point in question.
 
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  • #13
cjackson said:
Is the image accurate?

Yes, it accurately depicts the relative sizes of the planets and the Sun compared to one another. All of the other planets could fit between the Earth and the Moon, with a bit of room to spare.
 
  • #14
Mikestone said:
The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
There certainly is such vantage point, and we're living on it. One simply has to wait until the planets line up in their orbits so that they both are opposite of the Sun on the sky.
And since they're both in opposition as of this month, one can see both showing their full discs if one goes out and looks at the sky tonight.
And if one waits until December of this year, the two planets will even be so close together to fit inside the picture in the opening post - they'll pass each other at approx. 6' of angular separation, which is approx. 1/5th of the width of the disc of the Sun.

What they can't ever be is in front of the Sun as seen from Earth, but as was already explained the picture is just to illustrate the relative (physical, not angular) sizes.
 
  • #15
phinds said:
That's not what "to scale" means here. The fact that all the planets are lined up like that is understood to be bogus. It's the relative sizes that are the point in question.
Sorry. In that case I'd say (I haven't tried to actually measure) that they *are* pretty much to scale.
 
  • #16
star_comp_lg.jpg
largest-star-compared-to-earth.jpg


Earth is about 1/10th the radius of Jupiter. Jupiter is about 1/10th the radius of the Sun. The volumes are 1 million and 1 thousand. That is rounding off. The pictures look about right.

Jupiter is only slightly larger than Saturn. Brown dwarfs and the smallest red dwarfs end up around that size too. More massive brown dwarfs are slightly smaller than Jupiter. More mass just crushes it more.

The star Sirius b would fit inside of Earth's radius. Neutron stars are comparable in size to Manhattan island.
 

1. How do scientists determine the distance of Proxima Centauri?

Scientists use a method called parallax to determine the distance of Proxima Centauri. This involves measuring the apparent shift in the position of the star as the Earth orbits the Sun.

2. How large is Proxima Centauri compared to our Sun?

Proxima Centauri is much smaller than our Sun, with a radius of only about 1/7th of the Sun's radius. It is also much cooler and less luminous.

3. What is the significance of Proxima Centauri's habitable zone?

The habitable zone of Proxima Centauri is the region where liquid water could potentially exist on a planet's surface. This makes it a prime location to search for potentially habitable exoplanets.

4. How long does it take for light from Proxima Centauri to reach Earth?

Light from Proxima Centauri takes approximately 4.2 years to reach Earth. This means that the light we see from the star today actually left it 4.2 years ago.

5. Can Proxima Centauri be seen with the naked eye?

No, Proxima Centauri is not visible to the naked eye. It is a red dwarf star that is much too faint to be seen without the aid of a telescope.

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