IPB

Welcome Guest ( Log In | Register )

2 Pages V   1 2 >  
Reply to this topicStart new topic
Size of Sun as seen from Mercury
algorimancer
post Jun 20 2011, 03:02 PM
Post #1


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.
Go to the top of the page
 
+Quote Post
ilbasso
post Jun 20 2011, 03:18 PM
Post #2


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
Go to the top of the page
 
+Quote Post
Decepticon
post Jun 20 2011, 09:14 PM
Post #3


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!
Go to the top of the page
 
+Quote Post
Phil Stooke
post Jun 20 2011, 09:23 PM
Post #4


Solar System Cartographer
****

Group: Members
Posts: 10122
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
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
Go to the top of the page
 
+Quote Post
Gsnorgathon
post Jun 20 2011, 09:53 PM
Post #5


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
Go to the top of the page
 
+Quote Post
Mr Valiant
post Jun 26 2011, 01:00 AM
Post #6


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.
Go to the top of the page
 
+Quote Post
Decepticon
post Jun 26 2011, 04:29 AM
Post #7


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.
Go to the top of the page
 
+Quote Post
Greg Hullender
post Jun 26 2011, 05:04 PM
Post #8


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
Go to the top of the page
 
+Quote Post
JohnVV
post Jun 27 2011, 08:47 AM
Post #9


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]
Go to the top of the page
 
+Quote Post
Bjorn Jonsson
post Jun 28 2011, 09:41 AM
Post #10


IMG to PNG GOD
****

Group: Moderator
Posts: 2250
Joined: 19-February 04
From: Near fire and ice
Member No.: 38



QUOTE (Decepticon @ Jun 26 2011, 04:29 AM) *
Interesting, Most space art of Jupiter from Io or Europa look incorrect.

This doesn't have to be the case - the field of view varies. There is no single correct size of Jupiter as seen from the Galileans.
Go to the top of the page
 
+Quote Post
djellison
post Jun 28 2011, 03:29 PM
Post #11


Founder
****

Group: Chairman
Posts: 14431
Joined: 8-February 04
Member No.: 1



Quite. Neither of these views is 'incorrect'
Attached thumbnail(s)
Attached Image
 
Go to the top of the page
 
+Quote Post
Phil Stooke
post Jun 28 2011, 04:45 PM
Post #12


Solar System Cartographer
****

Group: Members
Posts: 10122
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
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
Go to the top of the page
 
+Quote Post
ilbasso
post Jun 28 2011, 08:41 PM
Post #13


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
Go to the top of the page
 
+Quote Post
Fran Ontanaya
post Jun 29 2011, 02:41 AM
Post #14


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.
Go to the top of the page
 
+Quote Post
tedstryk
post Jun 29 2011, 09:58 PM
Post #15


Interplanetary Dumpster Diver
****

Group: Admin
Posts: 4404
Joined: 17-February 04
From: Powell, TN
Member No.: 33



QUOTE (ilbasso @ Jun 28 2011, 09:41 PM) *
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!


--------------------
Go to the top of the page
 
+Quote Post

2 Pages V   1 2 >
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 19th March 2024 - 11:42 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.