sunrise on mercury

[tropicalzone]

imagine sunrise on mercury,how much bigger would the sun look on mercury than on earth?

 

[doubletruncation]

The heliocentric orbit of Mercury has a semi-major axis of 0.38 AU (the Earth's is 1 AU by definition). The angular size of the sun is just the ratio of the diameter of the sun to it's distance, so on Mercury the sun would appear 1/0.38 = 2.6 times larger than it does on the Earth. If you held your little finger out at arm's length its width spans about 1.5 degrees. From Earth the sun has an angular diameter of about half a degree. So, from Mercury the sun would be just covered by your little finger held out at arm's length.<br /> <div class="Discussion_UserSignature"> </div>

 

[qso1]

Not as impressive as one might imagine and as space artists of years past would have one believe. But it would still be an awesome sight since its something we don't see every day...or any day for that matter. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[alokmohan]

Are there two sunrises in mercury?

 

[qso1]

Actually, its tidally locked in orbit around the sun. Its rotation period equals or is pretty close to equaling its orbital duration. Travelling around the sun once every 88 days. You'd literally have to walk or fly from the night side into the day side to see a sunrise. You would be able to see the sun low on the horizon if you were near the dayligh edge of the terminator.<br /><br />Hope that helps. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[billslugg]

I believe it is in a 3:2 resonance. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[qso1]

I seem to recall that as well but I didn't have any refs handy. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[dragon04]

<font color="yellow">Are there two sunrises in mercury?</font><br /><br />Yes, depending on your location on the planet with respect to your view and the length of a Hermian "day".<br /><br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[nexium]

I agree: Mercury is not tide locked. The day is long, but all locations except creator bottoms near the poles have sun rise and sun set. With negligble atmosphere, the sun is very harsh and the sky is almost as black as midnight.

 

[dragon04]

No, it's not tidally locked. The planet rotates in a 3:2 spin-orbit resonance as billslugg pointed out.<br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[lukman]

Mercury in Wiki <div class="Discussion_UserSignature"> </div>

 

[qso1]

Dragon04:<br />No, it's not tidally locked. The planet rotates in a 3:2 spin-orbit resonance as billslugg pointed out.<br /><br />Me:<br />My mistake. I went to the wiki link and it shows a Sidereal period of 87.969 34 days and a Synodic period of 115.8776 days. I think somewhere back when I was much younger, it was thought Mercurys day was as long as its year. More recent observations have proven that to be wrong.<br /><br />Thanks for pointing that out lukman, Dragon04, and billslugg. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[nexium]

I think the 115.8776 Earth days is close to the average length of a day on Mercury's surface, so the day is longer than the year and almost twice the time the surface rotates with respect to the distant stars = 59.DDD days, I think. Neil