Size of Sun as seen from Mercury |
Size of Sun as seen from Mercury |
Jun 20 2011, 03:02 PM
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#1
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Member Group: Members Posts: 656 Joined: 20-April 05 From: League City, Texas Member No.: 285 |
I got to wondering about this, considered making my own graphic, then googled and came up with the following, from Burton Mackenzie's blog:
http://1.bp.blogspot.com/_tlXkPX0vMqk/SaTW...ize_diagram.png So apparently the Sun appears about 3 times as large in Mercury's sky as it does on Earth. I was expecting something much more dramatic. |
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Jun 20 2011, 03:18 PM
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#2
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Member Group: Members Posts: 753 Joined: 23-October 04 From: Greensboro, NC USA Member No.: 103 |
That is interesting indeed. It reminds us how far away even Mercury is from the Sun. So many graphics of the solar system make it look like Mercury is only a couple solar radii away!
I had a similar question a couple of months ago, wondering how far you would have to be from the Moon in order for it to appear the same size as Earth from your vantage point. It was a surprisingly small distance, only about 30,000 miles, if I remember correctly. Both bodies would be about 4 degrees across as seen in your sky. -------------------- Jonathan Ward
Manning the LCC at http://www.apollolaunchcontrol.com |
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Jun 20 2011, 09:14 PM
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#3
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Senior Member Group: Members Posts: 1276 Joined: 25-November 04 Member No.: 114 |
I have a question thats kinda related.
How big does Jupiter look from Io's Surface? Europa also! |
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Jun 20 2011, 09:23 PM
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#4
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Solar System Cartographer Group: Members Posts: 10164 Joined: 5-April 05 From: Canada Member No.: 227 |
It's quite simple geometry. For the same object (like the moon), double the distance = half the size, half the distance = double the size and so on, and for different objects at the same distance, twice the size = twice the apparent diameter and so on.
So... for the sun, Mercury's a third of the distance that Earth is from the sun, so three times bigger is what you'd expect. Jupiter from Io? Jupiter is about 40 times the diameter of the Moon (very roughly) so from the Moon's distance it would look 40 times bigger than the Moon. Then multiply by the appropriate fraction for the ratio of distances - you can go from there yourself, I think. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jun 20 2011, 09:53 PM
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#5
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Member Group: Members Posts: 259 Joined: 23-January 05 From: Seattle, WA Member No.: 156 |
Bravo, Phil! That's much better than my answer - I was just going to say 2arctan(radius/distance), but your version's a lot easier to work out in one's head.
Apparent diameter in degrees (Moon from Earth = .5): Jupiter from Io 18.6 Jupiter from Europa 11.8 Jupiter from Ganymede 7.4 Jupiter from Callisto 4.2 |
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Jun 26 2011, 01:00 AM
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#6
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Junior Member Group: Members Posts: 61 Joined: 20-March 10 From: Western Australia Member No.: 5275 |
Hey! Jupiter is so big. 4.2 degrees from Callisto, and considering Callisto is pretty much outside
the Jupiter Van Allen belts, it may be the first place humans set foot in the Jupiter system. Will be an awesome sight. |
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Jun 26 2011, 04:29 AM
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#7
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Senior Member Group: Members Posts: 1276 Joined: 25-November 04 Member No.: 114 |
QUOTE Jupiter from Io 18.6 Jupiter from Europa 11.8 Interesting, Most space art of Jupiter from Io or Europa look incorrect. |
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Jun 26 2011, 05:04 PM
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#8
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Senior Member Group: Members Posts: 1018 Joined: 29-November 05 From: Seattle, WA, USA Member No.: 590 |
Well, most Earth art makes the moon way, way too big, so I'm not sure what space art is supposed to do. I do get a kick out of how when they show Saturn from any of its moons, artists frequently tilt the planet so the rings can be seen.
Another point on sizes--forgive me if this seems too obvious--but the area is propotional to the square of the diameter. So the sun is not 3x bigger at Mercury--it's 9x bigger. --Greg |
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Jun 27 2011, 08:47 AM
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#9
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
a quick look
from Earth [attachment=24650:sun.earth.jpg] from Mercury [attachment=24649:sun.mer.jpg] earth [attachment=24651:earth.jpg] Mercury [attachment=24652:mer.jpg] |
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Jun 28 2011, 09:41 AM
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#10
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
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Jun 28 2011, 03:29 PM
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#11
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
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Jun 28 2011, 04:45 PM
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#12
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Solar System Cartographer Group: Members Posts: 10164 Joined: 5-April 05 From: Canada Member No.: 227 |
"So the sun is not 3x bigger at Mercury--it's 9x bigger."
Let's not confuse diameter and area! Both are correct. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Jun 28 2011, 08:41 PM
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#13
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Member Group: Members Posts: 753 Joined: 23-October 04 From: Greensboro, NC USA Member No.: 103 |
To be precise, the Sun is the same size. It just LOOKS bigger.
-------------------- Jonathan Ward
Manning the LCC at http://www.apollolaunchcontrol.com |
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Jun 29 2011, 02:41 AM
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#14
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Member Group: Members Posts: 293 Joined: 22-September 08 From: Spain Member No.: 4350 |
I think it would still have a smaller apparent area from Earth after compensating for the distance, due to Lorenz contraction as the Sun moves across the line of view.
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Jun 29 2011, 09:58 PM
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#15
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
To be precise, the Sun is the same size. It just LOOKS bigger. Huh? So are you saying that as I move my hand away from my face my hand doesn't shrink, it just looks smaller? My whole cosmology has just been rocked! -------------------- |
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Jun 29 2011, 10:22 PM
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#16
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
Every time a pointless debate of semantics begins, a baby seal pup gets clubbed to death
True story. |
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Jun 30 2011, 01:51 PM
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#17
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
Every time a pointless debate of semantics begins, a baby seal pup gets clubbed to death That reminds me Doug, your pelts from last month are ready. The guy says he's OK with coats and hats, but there is no way he can stitch them into undershorts. Sorry. -------------------- If Occam had heard my theory, things would be very different now.
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Jun 30 2011, 01:56 PM
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#18
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Member Group: Members Posts: 753 Joined: 23-October 04 From: Greensboro, NC USA Member No.: 103 |
I need to be better about using smiley faces.
-------------------- Jonathan Ward
Manning the LCC at http://www.apollolaunchcontrol.com |
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May 16 2018, 08:26 PM
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#19
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Director of Galilean Photography Group: Members Posts: 896 Joined: 15-July 04 From: Austin, TX Member No.: 93 |
Are there any good videos of the sun throughout a Mercurian day? I found this video, but it doesn't show how the sun's location varies, or what a specific observer on a specific spot would see. I assume there are solar system simulators that would allow one to stand on spots on Mercury and watch the sun progress?
https://www.youtube.com/watch?v=gubNWJ5RlP4 I assume at one of the sub-solar points you would see the Sun approach overhead, slow down, get larger, pause for a bit, then speed up and get smaller. But what would a person not at one of those points see? If you were 90* away, the sun would be largest at sunrise, shrink, then get larger again at sunset? Thanks everyone! -------------------- Space Enthusiast Richard Hendricks
-- "The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke Mother Nature is the final inspector of all quality. |
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May 16 2018, 09:01 PM
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#20
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Member Group: Members Posts: 923 Joined: 10-November 15 Member No.: 7837 |
-------------------- |
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May 17 2018, 06:48 AM
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#21
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Newbie Group: Members Posts: 5 Joined: 20-November 17 From: Brazil Member No.: 8292 |
Stellarium as well is pretty good. F6 to change location, switch planet to Mercury, pick somewhere on the map and speed up time as you wish. You can zoom into the Sun and watch it change size as time progresses, change your location 90° to the east/west and do the same again. Spoiler alert: your assumption is correct
Curiously, just over a year ago I made a gif/short video using Stellarium (Gfycat link) of what a solar day on Mercury would look like, but the change in apparent size of the Sun isn't really noticeable - it was more aimed at visualising the Sun's movement through the sky. The labels are all in Portuguese, L is east and O is west. -------------------- |
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May 17 2018, 09:52 PM
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#22
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Director of Galilean Photography Group: Members Posts: 896 Joined: 15-July 04 From: Austin, TX Member No.: 93 |
Thanks for tips, those both look like great programs!
-------------------- Space Enthusiast Richard Hendricks
-- "The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke Mother Nature is the final inspector of all quality. |
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May 18 2018, 12:30 AM
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#23
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
https://eyes.nasa.gov could do it as well. If you use the shoulder camera on Mercury then lock the camera to the sun you could watch it all day.
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