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Denis12
2005-Dec-19, 09:16 PM
Is the sun shining bright on pluto or just faint,dim and thus a dim very cold world. Some people have said that pluto has a lack on sunlight,because its large distance from the sun. Can you explain that? Denis.

phunk
2005-Dec-19, 09:34 PM
Yup, alot less sunlight on pluto due to the distance from the sun, and the inverse square law. If I remember correctly, pluto's aphelion is actually far enough away that the atmosphere freezes for part of the year.

Denis12
2005-Dec-19, 09:58 PM
Sometimes pluto comes within neptunes orbit,and why is it that there is not a collision between neptune and pluto,i find that very strange,can yoy explain that? plutos distace to the sun is very different,from closer to the sun than neptune to much further away from the sun. Very strange i think.

grant hutchison
2005-Dec-19, 10:00 PM
Pluto receives about 1000th as much sunlight as Earth. That's about the same lighting level as you have in your house with the lights on at night. So it wouldn't appear dim or dark.

Grant Hutchison

Denis12
2005-Dec-19, 10:01 PM
And why dont have the spacecrafts voyager and pioneer takes photos of pluto and its moon charon. They missed pluto totally. Why.

grant hutchison
2005-Dec-19, 10:02 PM
Sometimes pluto comes within neptunes orbit,and why is it that there is not a collision between neptune and pluto,i find that very strange,can yoy explain that? plutos distace to the sun is very different,from closer to the sun than neptune to much further away from the sun. Very strange i think.Pluto's orbit is tilted relative to Neptune's, so their orbits don't intersect. Also, Neptune and Pluto move in such a way that they are never both near the orbit crossing-point at the same time.

Grant Hutchison

Tim Thompson
2005-Dec-19, 10:21 PM
Pluto receives about 1000th as much sunlight as Earth.
That looks like too much. The Pluto fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html) from NSSDC shows that the surface irradiance of Pluto, in W/m2, is about 5x10-7 of Earth, which is 10,000 times less than 1000th. If the visual magnitude scales like the irradiance, and each magnitude is a factor of 2.5, then 50,000,000 times dimmer implies about 19.5 magnitudes dimmer. If the apparent magnitude of the sun is -27.64, then at Pluto, it should have an apparent magnitude -8.1, which is fairly bright, brighter than any star we see besides the Sun, but still about 50 times dimmer than a full moon (-12.5).

Denis12
2005-Dec-19, 10:22 PM
Maybe a stupid question,but can you walk around pluto (without) a spacesuit? there is a weak atmosphere there. I hope that there are missions to pluto in the future.

Tim Thompson
2005-Dec-19, 10:28 PM
And why dont have the spacecrafts voyager and pioneer takes photos of pluto and its moon charon. They missed pluto totally. Why.
It is my understanding that Voyager I could have been sent to Pluto. But the decision was made to do Titan instead. Voyager II was too late and could not reach Pluto from where it met Neptune. The New Horizons mission (http://www.pluto.jhuapl.edu/), scheduled for launch next January, is bound for Pluto. It should arrive at Pluto about 2015, depending on when it launches, in the Jan-Feb launch window.

Tim Thompson
2005-Dec-19, 10:31 PM
Maybe a stupid question,but can you walk around pluto (without) a spacesuit? there is a weak atmosphere there. I hope that there are missions to pluto in the future.
No, the surface temperature of 35 to 45 Kelvins is rather colder than liquid nitrogen, at about 77 Kelvins. Way too cold, without a spacesuit you would be freeze dried in a hurry. The atmosphere, such as it is, is totally unbreathable in any case.

Hey, this is my 1000th post! Now I am officially as crazy as the rest of the 1000+ gang.

Denis12
2005-Dec-19, 11:01 PM
That looks like too much. The Pluto fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html) from NSSDC shows that the surface irradiance of Pluto, in W/m2, is about 5x10-7 of Earth, which is 10,000 times less than 1000th. If the visual magnitude scales like the irradiance, and each magnitude is a factor of 2.5, then 50,000,000 times dimmer implies about 19.5 magnitudes dimmer. If the apparent magnitude of the sun is -27.64, then at Pluto, it should have an apparent magnitude -8.1, which is fairly bright, brighter than any star we see besides the Sun, but still about 50 times dimmer than a full moon (-12.5).
Thus there is less sunlight than here with the full moon,that sounds pretty dark,but others say completely other stories,that the sunlight on pluto is much brighter than the full moon. I dont know what i can believe. Denis.

grant hutchison
2005-Dec-19, 11:09 PM
That looks like too much. The Pluto fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/plutofact.html) from NSSDC shows that the surface irradiance of Pluto, in W/m2, is about 5x10-7 of Earth, which is 10,000 times less than 1000th.Ummm ... Where are you getting that figure on the page? Here's a cut-and-paste of the relevant line:
Pluto Earth Ratio (Pluto/Earth)

Solar irradiance (W/m2) 0.89 1367.6 0.0007
Which shows that the irradiance is (on average) a little under a thousandth of Earth's.
But it's a simple inverse-square calculation: since Pluto is currently 31 AU from the Sun, it's receiving 1/31² = 0.001 times as much illumination and irradiation. A thousandth.
The apparent magnitude of the Sun from Pluto is around -19.3, currently.

Grant Hutchison

Relmuis
2005-Dec-19, 11:13 PM
At perihelium Pluto is 30 times more distant from the Sun than Earth. At aphelium Pluto is 50 times more distant from the Sun than Earth.

Therefore, the strength of sunlight on Pluto varies between 1/900 and 1/2500 times the strength of sunlight on Earth.

(While I was writing this, Grant Hutchison pointed out the same.)

peteshimmon
2005-Dec-19, 11:19 PM
Well when the atmosphere was detected by
occultation in 1988, the popular explanation
was "well Pluto is nearer than Neptune at the
moment so its warm on Pluto and the methane
sublimates". I thought "Huhh..?"

Bob
2005-Dec-19, 11:53 PM
http://seds.lpl.arizona.edu/nineplanets/nineplanets/plutodyn.html

This website shows graphically why Neptune and Pluto can never collide. And actually Pluto's closest approach to another planet is with Uranus, not Neptune.

Denis12
2005-Dec-20, 12:10 AM
How warm is warm? Still below freezing i think. And how is earth visible from pluto? And in which constellation is earth as seen from pluto?

Denis12
2005-Dec-20, 12:27 AM
I have just looked at the orbits and the positions of the planets at heavens above,and at this moment pluto comes just out of neptunes orbit and it is relatively clear and light on pluto now,but from this moment it goes a long way to its longest distance from the sun. In the year 2110 it reaches its farrest distance from the sun,and then it will be ghostly dusk on pluto on local afternoon time,and it will be severe cold,with frozen methane.

Bob
2005-Dec-20, 12:30 AM
Sounds like Chicago.

grant hutchison
2005-Dec-20, 12:35 AM
How warm is warm? Still below freezing i think. And how is earth visible from pluto? And in which constellation is earth as seen from pluto?Earth is pretty close to the Sun in Pluto's sky at present, so it might be difficult to see.
The Sun and Earth are sitting between the constellations of Orion and Taurus, as seen from Pluto.
The temperature's about 40 K.
(Information from Celestia (http://www.shatters.net/celestia/).)

Grant Hutchison

Denis12
2005-Dec-20, 01:30 AM
What is 40 K in degrees celsius?

Lord Jubjub
2005-Dec-20, 01:46 AM
Freezing point of water is 273 K, so 40 K would be -233 C.

Hamlet
2005-Dec-20, 01:49 AM
What is 40 K in degrees celsius?

40K = -233.15 degrees Celsius

Blob
2005-Dec-20, 02:10 AM
Hum,
i would give it a one out of ten.

Denis12
2005-Dec-20, 02:47 AM
Why is 40 K at pluto called as warm?? That is a temperature that is never recorded on earth.

Kristophe
2005-Dec-20, 04:43 AM
Hum,
i would give it a one out of ten.

You stole my joke! I combed the thread to see if anyone had done it, and it was looking so good until the end! *weeps*

Kristophe
2005-Dec-20, 04:46 AM
Why is 40 K at pluto called as warm?? That is a temperature that is never recorded on earth.

Well, it gets colder on Pluto. 40 K, I imagine, is pretty balmy weather for the lord of the underworld considering at its coldest, it's nearly 20 times the Earth-Sun distance farther from the sun than it is now.

Relmuis
2005-Dec-20, 03:11 PM
Weather will probably get even colder than that on Sedna, Quaoar and the recently discovered new planet. It might be interesting if it were to become cold enough to liquefy helium. If any helium is present, that is. If there is a planet with lakes, rivers, seas or entire oceans of liquid helium in the Solar System, people should definitely send a probe. It's bound to discover things never seen before.

Elyk
2005-Dec-20, 04:17 PM
Rembember that light travels much better than heat, so Pluto may be cold but that doesn't mean it's dark.

tony873004
2005-Dec-20, 05:02 PM
...Neptune and Pluto move in such a way that they are never both near the orbit crossing-point at the same time.

Grant Hutchison

Click link for animation (too large to upload as attachment).
http://orbitsimulator.com/gravity/pluto2.GIF

Also, here's an old thread discussing how bright it is on Pluto:
http://www.bautforum.com/showthread.php?t=33874&highlight=pluto

Tim Thompson
2005-Dec-20, 05:16 PM
Ummm ... Where are you getting that figure on the page?
By misreading it! I used 0.007 as W/m2 instead of a ratio. I should stop posting after bedtime, or I'll do something even worse someday.

grant hutchison
2005-Dec-20, 05:26 PM
By misreading it! I used 0.007 as W/m2 instead of a ratio.Ah, okay. Phew! You gave such a precise figure you really had me twitching.

Grant Hutchison

peteshimmon
2005-Dec-20, 06:22 PM
The point I was making was that it was a
quick "pop" explanation of an atmosphere on
Pluto. As the occultation data in 1988 also
indicated a non spherical shape for the
Planet, a better explanation is that
volatiles are being released as the body
forms into a proper sphere. Is 40 K the
sublimation point for methane? The ice moons
of the Gas Giants seem devoid of atmospheres.

Joff
2005-Dec-20, 06:31 PM
Earth is pretty close to the Sun in Pluto's sky at present, so it might be difficult to see. I guess that's always true... viewed from 30AU the largest separation Earth would ever have from the sun would be less than 2 degrees. By contrast Mercury can get up to about 21 degrees away from the (admittedly much brighter) sun in Earth's sky.

grant hutchison
2005-Dec-20, 07:35 PM
I guess that's always true... viewed from 30AU the largest separation Earth would ever have from the sun would be less than 2 degrees.Yes. At present, Pluto's on the far side of the Sun from the Earth, so Sun and Earth look pretty close in Pluto's sky. Using Celestia again, I eyeball the separation to be roughly 17'. I don't know what sort of apparent magnitude Earth should have, but that close to a -19 mag star, it seems like it would be very difficult to pick out our pale blue dot.

Grant Hutchison