APOD: Moon over Makemake (2016 Apr 30)

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APOD: Moon over Makemake (2016 Apr 30)

Post by APOD Robot » Sat Apr 30, 2016 4:09 am

Image Moon over Makemake

Explanation: Makemake, second brightest dwarf planet of the Kuiper belt, has a moon. Nicknamed MK2, Makemake's moon reflects sunlight with a charcoal-dark surface, about 1,300 times fainter than its parent body. Still, it was spotted in Hubble Space Telescope observations intended to search for faint companions with the same technique used to find the small satellites of Pluto. Just as for Pluto and its satellites, further observations of Makemake and orbiting moon will measure the system's mass and density and allow a broader understanding of the distant worlds. About 160 kilometers (100 miles) across compared to Makemake's 1,400 kilometer diameter, MK2's relative size and contrast are shown in this artist's vision. An imagined scene of an unexplored frontier of the Solar System, it looks back from a spacecraft's vantage as the dim Sun shines along the Milky Way. Of course, the Sun is over 50 times farther from Makemake than it is from planet Earth.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by bystander » Sat Apr 30, 2016 4:25 am

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Ann » Sat Apr 30, 2016 5:42 am

Minor planets and moons.
Source (according to this page): NASA "Space Place" for Kids
They do pick up their moons, those minor planets out there. Now Makemake has its satellite too, which was undiscovered at the time when NASA made the picture at left.

That seems to be an interesting difference between the minor planets in or near the Kuiper Belt and the inner planets. Mercury has no moon, and neither has Venus.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by heehaw » Sat Apr 30, 2016 10:17 am

As an astronomer, I never much liked (or like) paintings showing 'imagined' appearances of systems, not even Chesley Bonestell. But it makes me think how incredibly lucky I am, that in my lifetime, so many celestial objects have gone from Bonestell imaginings to a crisp reality. We didn't even know the rotation of Mercury (indeed, we had it wrong) and now we have detailed images of the surface of the whole planet. I admit I liked the old imagined Venus (under those clouds the swamps and the dinosaurs) much better than the new, real, Venus (hell). Mars is OK, but not great. Radiation means people will never colonize anything in the solar system, ever. Treasure and preserve this Earth, folks!

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by neufer » Sat Apr 30, 2016 2:06 pm

Ann wrote:
They do pick up their moons, those minor planets out there. That seems to be an interesting difference between the minor planets in or near the Kuiper Belt and the inner planets. Mercury has no moon, and neither has Venus.
  • Neither do the 7 largest asteroids.
https://en.wikipedia.org/wiki/87_Sylvia wrote: <<87 Sylvia is the 8th-largest asteroid in the asteroid belt. It is a member of the Cybele group located beyond the core of the belt. Sylvia is the first asteroid known to possess more than one moon. Sylvia was discovered by N. R. Pogson on May 16, 1866 from Madras (Chennai), India. A. Paluzie-Borrell, writing in Paul Erget's The Names of the Minor Planets (1955), mistakenly states that the name honours Sylvie Petiaux-Hugo Flammarion, the first wife of astronomer Camille Flammarion. In fact, in the article announcing the discovery of the asteroid, Pogson explained that he selected the name in reference to Rhea Silvia, mother of Romulus and Remus.

Sylvia is very dark in color and probably has a very primitive composition. The discovery of its moons made possible an accurate measurement of the asteroid's mass and density. Its density was found to be very low (around 1.2 times the density of water), indicating that the asteroid is porous to very porous; from 25% to as much as 60% of it may be empty space, depending on the details of its composition, this suggests a loose rubble pile structure. Sylvia is also a fairly fast rotator, turning about its axis every 5.18 hours. The short axis is the rotation axis. Direct images[3] indicate that Sylvia's axial tilt of around 29.1°. Sylvia's shape is strongly elongated.>>
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Ann » Sat Apr 30, 2016 2:18 pm

neufer wrote:
Ann wrote:
They do pick up their moons, those minor planets out there. That seems to be an interesting difference between the minor planets in or near the Kuiper Belt and the inner planets. Mercury has no moon, and neither has Venus.
Neither do the 7 largest asteroids.
Well, the 7 largest asteroids are not too close to the Kuiper Belt. :wink:

And they are not too far from the inner solar system either, considering.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Chris Peterson » Sat Apr 30, 2016 2:37 pm

Ann wrote:That seems to be an interesting difference between the minor planets in or near the Kuiper Belt and the inner planets. Mercury has no moon, and neither has Venus.
Most orbits that involve more than two bodies are unstable. Essentially all are subject to chaotic adjustments. That makes moons around planets close to the Sun problematic. It makes moon around bodies subject to perturbations from Jupiter problematic.

We seen moons around the gas giants because their local gravity dominates, and they are approximately two body systems (with exceptions being metastable resonances). We see moons around bodies in the far outer system because again, they are close to two body systems. The Earth is a bit of a special case, with the Moon being closer to a binary planet, both in orbit around the Sun.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by neufer » Sat Apr 30, 2016 2:48 pm

Ann wrote:
[Kuiper Belt objects] do pick up their moons, those minor planets out there. That seems to be an interesting difference between the minor planets in or near the Kuiper Belt and the inner planets. Mercury has no moon, and neither has Venus.

Ann wrote:
neufer wrote: Neither do the 7 largest asteroids.
Well, the 7 largest asteroids are not too close to the Kuiper Belt. :wink:
And they are not too far from the inner solar system either, considering.
It seems both like a more relevant & statistically significant comparison:

Of the eight largest asteroids only one is known to have a moon.

Of the eight largest Kuiper Belt objects six are known to have moons.

These can be said to be statistically significant different sets at the 95% confidence level.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by orin stepanek » Sat Apr 30, 2016 6:27 pm

What? 16 planets and counting? How many dwarfs are out there? Maybe Mercury should be counted as a dwarf also! And the giants; maybe should be classified as giant planets instead as just planets! So maybe we have only 3 planets; Venus Earth and Mars! :wink: :mrgreen:
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by owlice » Sat Apr 30, 2016 9:03 pm

orin stepanek wrote:What? 16 planets and counting? How many dwarfs are out there? Maybe Mercury should be counted as a dwarf also! And the giants; maybe should be classified as giant planets instead as just planets! So maybe we have only 3 planets; Venus Earth and Mars! :wink: :mrgreen:
An excellent idea!!!
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by lawn » Sat Apr 30, 2016 11:29 pm

owlice wrote:
orin stepanek wrote:What? 16 planets and counting? How many dwarfs are out there? Maybe Mercury should be counted as a dwarf also! And the giants; maybe should be classified as giant planets instead as just planets! So maybe we have only 3 planets; Venus Earth and Mars! :wink: :mrgreen:
An excellent idea!!!
Why stop there? Venus, Earth and Mars could be "giant dwarfs." Then there'll be no planets.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by orin stepanek » Sat Apr 30, 2016 11:49 pm

Ceres-reously; has there every been a count of the objects ( size of Ceres and Charon and larger) that are in the Solar system? There are a lot of moons that are about the size of the dwarfs! There's a lot of real estate out there. I'll bet there is a lot of gold in those dwarfs! :wink: :lol2:
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Jim Leff » Sun May 01, 2016 3:43 am

Every time I see the sun depicted from distant planets/objects, it makes me wonder how far away a human would need to go before he could safely stare at the sun. Any ideas?

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by neufer » Sun May 01, 2016 12:37 pm

Jim Leff wrote:
Every time I see the sun depicted from distant planets/objects, it makes me wonder how far away a human would need to go before he could safely stare at the sun. Any ideas?
That sort of depends upon how long one intends to stare directly at the Sun but for someone with excellent vision it would probably start to be safe to stare at the Sun for extended periods from Makemake at aphelion (53 AU).

(You could always view the Sun through a pinhole in a sheet of aluminum foil and see how far back you had to stand in order to feel comfortable viewing.)
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by rstevenson » Mon May 02, 2016 12:17 am

heehaw wrote:... Radiation means people will never colonize anything in the solar system, ever. ...
And we'll never go more than 60 mph on the Earth because we couldn't breath. And we'll never go into space because there's nothing for the rockets to push against. :lol2:

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by oldrcd » Mon May 02, 2016 6:35 am

I'm with heehaw of never much liking artist's conceptions or interpretations. They seem to have no grasp of the enormity of space (or perhaps the laws of physics?) so they depict planets/moons/etc impossibly large and close. If these objects got as close as they depict, tidal forces would rip them apart, melt them, or send them crashing together. Let APOD use real images; there are plenty.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by geckzilla » Mon May 02, 2016 7:50 am

oldrcd wrote:I'm with heehaw of never much liking artist's conceptions or interpretations. They seem to have no grasp of the enormity of space (or perhaps the laws of physics?) so they depict planets/moons/etc impossibly large and close. If these objects got as close as they depict, tidal forces would rip them apart, melt them, or send them crashing together. Let APOD use real images; there are plenty.
The funny thing is that Alex Parker is one of the PIs who discovered the moon. He made this illustration, too. So it's not as if he has no grasp of the enormity of space or the laws of physics. The thought is laughable. He's probably one of the most qualified individuals for the job, but in the end it's still just an illustration.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Jim Leff » Mon May 09, 2016 2:04 pm

neufer wrote:
Jim Leff wrote:
Every time I see the sun depicted from distant planets/objects, it makes me wonder how far away a human would need to go before he could safely stare at the sun. Any ideas?
That sort of depends upon how long one intends to stare directly at the Sun but for someone with excellent vision it would probably start to be safe to stare at the Sun for extended periods from Makemake at aphelion

Did not expect that reply. I figured it would be much, much close (Jupiter/Saturn-ish).

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by neufer » Mon May 09, 2016 5:00 pm

Jim Leff wrote:
neufer wrote:
Jim Leff wrote:
Every time I see the sun depicted from distant planets/objects, it makes me wonder how far away a human would need to go before he could safely stare at the sun. Any ideas?
That sort of depends upon how long one intends to stare directly at the Sun but for someone with excellent vision it would probably start to be safe to stare at the Sun for extended periods from Makemake at aphelion
Did not expect that reply. I figured it would be much, much close (Jupiter/Saturn-ish).
From Makemake at aphelion the Sun is a star of magnitude -18
(the equivalent of a Type Ia Supernova at 57 light years distance).
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Chris Peterson » Mon May 09, 2016 5:23 pm

neufer wrote:
Jim Leff wrote:
neufer wrote: That sort of depends upon how long one intends to stare directly at the Sun but for someone with excellent vision it would probably start to be safe to stare at the Sun for extended periods from Makemake at aphelion
Did not expect that reply. I figured it would be much, much close (Jupiter/Saturn-ish).
From Makemake at aphelion the Sun is a star of magnitude -18
(the equivalent of a Type Ia Supernova at 57 light years distance).
For reference- it is generally considered safe to continuously view the Sun through a ND 4.0 filter, and to view it for some seconds at a time through a ND 3.0 filter. Given the Sun at mag -27, the ND 4.0 reduces that to about mag -17, and the ND 3.0 to about mag -19. So your target of mag -18 for safe viewing (Makemake at aphelion) is quite reasonable.

The Sun at Saturn is about 1% as bright as that at Earth- the same as looking at the Sun from Earth through a stacked pair of sunglasses. It will only take a few seconds to burn your retina.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Jim Leff » Mon May 09, 2016 8:42 pm

Just intuitively, I'd have figured from that that the sun, at our distance, would present a viciously perilous threat to the eyes; that humans would have evolved a downward-looking face and we'd all be nocturnal. Etc.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by geckzilla » Mon May 09, 2016 9:00 pm

Jim Leff wrote:Just intuitively, I'd have figured from that that the sun, at our distance, would present a viciously perilous threat to the eyes; that humans would have evolved a downward-looking face and we'd all be nocturnal. Etc.
Ever tried staring at the Sun? It's physically painful. That's evolution telling you to stop it.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Chris Peterson » Mon May 09, 2016 9:29 pm

Jim Leff wrote:Just intuitively, I'd have figured from that that the sun, at our distance, would present a viciously perilous threat to the eyes; that humans would have evolved a downward-looking face and we'd all be nocturnal. Etc.
The Sun isn't much of a threat to our eyes at all. It creates such a small image that the retinal blood flow can easily carry away the heat. You have to work pretty hard at it to damage your eye- override your reflexes, ignore the discomfort, suppress your largely involuntary saccadic eye movement. Seems like evolution did just fine.
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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by Jim Leff » Tue May 10, 2016 5:18 am

Chris Peterson wrote: The Sun isn't much of a threat to our eyes at all.
....and yet if you go 1,000,000,000 miles further out, to where the sun is only 1% of its earthly brightness, you still can't safely stare at it.

Hence my perplexity.

It's like saying a certain acid isn't particularly caustic, but you shouldn't get even one molecule on you.

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Re: APOD: Moon over Makemake (2016 Apr 30)

Post by geckzilla » Tue May 10, 2016 6:42 am

Well, no one wants to be responsible for telling you something that might cause damage to your precious eyes. It is pretty hard to get the Sun to harm them (unless you've got a telescope, binoculars or some other form of focusing lens), but once the harm happens there's no healing it, and your eyes are extremely important if you've come to rely on them your entire life. You can stare at the Sun a while here on Earth if you'd like...

I happen to live with someone who did so at the beach once. He said he was giving himself "laser eye surgery" and is the type of person who thinks that something natural like the Sun is really good for you. He can still see, but I have no idea what harm that did to him. All I know is we walked up to him and he was crying and staring at the Sun until we told him to stop it.
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