Why can't we take good pictures of Pluto?

[Ortix]

I don't quite understand why we can't take good pictures of Pluto or comets in the kuiper belt but can detect galaxies essentially 13 billion light years away.

As an AP Physics student i should know and my guess is the focal point of the lens has something to do with this. I think it's like taking a picture from the Apollo landing sight here from the moon. Is this correct?

Just wondering

 

[origin]

I don't quite understand why we can't take good pictures of Pluto or comets in the kuiper belt but can detect galaxies essentially 13 billion light years away.

As an AP Physics student i should know and my guess is the focal point of the lens has something to do with this. I think it's like taking a picture from the Apollo landing sight here from the moon. Is this correct?

Just wondering

No it has nothing to do with the focal point.

It is simply that Pluto is very small and faint while galaxies are very large and bright.

 

[Gravity_Ray]

I don't quite understand why we can't take good pictures of Pluto

Cause Pluto keeps hiding behind Mickey...

Sorry, Im a bit punch drunk working all day... Here is the picture of Pluto HST did take.

http://hubblesite.org/newscenter/archiv ... es/1996/09

I guess its not what you would call a "good picture of Pluto", and that is because of the other answer you got. Another way to say it is for the same reason you can clearly see the Moon with just your eyes but you cannot see an ant on the ground 20 feet away.

 

[3488]

Hi Gravity_Ray, you have it spot on.

IIRC the images of Pluto you have linked to are still the best to date.

New Horizons hopefully will produce 40 metre resolution images of Pluto, or at least the area beneath New Horizons at closest approach. Charon will be seen at 80 metre resolution at closest approach.

Andrew Brown.

 

[yale_s]

Hubble can resolve 0.05 arcseconds.

Pluto is 0.08 arcseconds, so it just covers a pixel or two.

The "images" of Pluto's surface is essentially derived from the variations in brightness when Charon crosses in front, rather than a direct imaging.

The galaxies seen in the deep space images are actually rather large (altho very dim).

The latest image from Hubble was 60 arcMINUTES across which means the images of the galaxies are quite wide.

- yale

 

[CalliArcale]

YALE!!!

*tacklepouncehuggles*

How ya doing, man?

Sorry to hijack the thread, but I just had to say that. ;-) Been missin' ya, dude!

 

[yale_s]

Mmmph...
*picksselfofffloorandtriestocatchbreath* :?

Lady Time Lord!
Long time- no see!

Yeah, I just phased-in with the EnviroSphere. Been running low on EverClear propellent.

I've been roaming the far reaches of the Galactic Wastes and was stricken with a wave of nostalgia for That Old Gang Of Mine.

I'm thinking of maybe cooling my thrusters here for a while.

So, nu?, what's up with you and yours?

- yale

 

[MeteorWayne]

Wow, Hi yale. So it is ye that we newbies have heard so much about in the past! Nice to meet ya!

Meteor Wayne

 

[yale_s]

I don't know what you heard, but unless any of it was positive I DENY THE WHOLE THING! :shock:

Yeah, I was here back when the earth's crust was still cooling. I see Yevaud is still breathing and I am checking to see if there any other Living Fossils still around.

I hope to post here and there if I have anything to add.

- yale

 

[drwayne]

I am not a fossil yet, but getting pretty crusty.

Good to "see" you sir.

Wayne

 

[yale_s]

I see the Dr is In...

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I have been checking my facts, and I see I used the lowest resolution of the Faint Object Camera.
While that mode is only 0.05 arcseconds, in hi-rez, it is closer to 0.007 arcsecs.

That means that Pluto, at its closer than average distance, with its diameter of about 0.1 arcsecs DOES show detail directly.

14 or 15 pixels will span the diameter - something a bit under 200km/pixel.

Pluto:

 

[Torque_dvl]

Before New Horizons arrives, It's just a question of current space telescope's abilities, and no big improvements are expected...

Besides, imagine concept of a space telescope with main mirror consisting of many small independently floating mirrors instead of one big and bulky... The system will be very versatile...

The mirrors can be made of thin film with some sort of shape controllers and individual ion engines, so they would be very lightweight and very slim, around tens of kilograms and few cm thick. We can stack hundreds of them into one launcher, and the resulting mirror will be much more powerful than even JWST's one. More, the shape and size of it can be easily changed by just moving components around! The registering unit will also be freely floating, and that will allow to change focus distance. The damaged mirrors can be replaced without significant drop in performance of the whole system, and more mirrors can be added to improve it.

With two launches (one for mirror components and one for registering unit) it will be possible to build around-100-m main mirror, large enough to see Pluto in details and peer deep into Cuiper belt And, to expand, imagine 10000 km telescope in L4 or L5 point, able to directly see disks of exoplanets and who knows what else... :roll:

 

[Gravity_Ray]

Torque
I love it when people think big...

The Lagrange points in our solar system are woefully unused.

 

[AdmiralQuality]

"Why can't we take good pictures of Pluto?"

I dunno, I've seen a lot of good pictures of Uranus!







(Sorry, had to!

 

[rabraha3]

The Lagrange points are woefully underused simply because they're so far away. It takes a lot of time and effort to send things to these points, and you have to make sure they work perfectly. There will be no repair missions to anything at any of the Lagrange points for quite a long time.

 

[hawkeyeofthehuron]

My friend, try Googling "inverse square law" and "albedo" for the rest of the story. This and the other replies should do it. I didn't read them all, but stars shine very brightly from their own light and we have to wait for the sun's light to go all the way to Pluto and back.
I took a couple of semesters of astronomy, all math-major credits, etc., before switching to EE because of the pesky Foreign Language requirement (but I did do English 101, 102, 201, 202 and 300).

 

[elguapoguano]

Yep, this thread is officially Hi-Jacked.....

Yales, good to know you're still kickin man. It's been forever since I've seen you post. Although I've been mostly hangin out at "the other place" quite a bit more than here lately, it's great to see you.

 

[AdmiralQuality]

...and we have to wait for the sun's light to go all the way to Pluto and back.

:lol: You're kidding, right?

 

[MeteorWayne]

I believe he was referring to how dim the resulting image is, rather than the amount of time.

 

[billions]

I've made a quick graphic to show the apparent sizes of the planets (from the point of view of the earth):

http://imgur.com/adQsF.jpg

I've also added a quick comparison graphic, showing how these planets size up to the apparent size of our Moon:

http://imgur.com/SKGgo.jpg

As you can see, all of the planets are quite tiny in the sky compared to the size of the moon. But there is still a lot of variation within the planets. While something like Jupiter looks quite nice at the size in my graphic, Pluto is still just a tiny dot!


Apparent sizes is only half of the story, though. Magnitude (brightness) is just as important. Perhaps more on that later...

 

[MeteorWayne]

Pluto reached about mag +13.5 at perihelion, of course it's dimmer the rest of the time.

 

[billions]

Indeed, due to the inverse square law and Pluto's distance, it has a tiny magnitude.

By my count the full moon is over 37 billion times brighter than Pluto! (here on Earth, of course).
Planets visible with the naked eye:

• Venus: 20.5 million times brighter than Pluto

• Mars: 4.3 million times brighter than Pluto

• Jupiter: 3.5 million times brighter than Pluto

• Mercury: 1.7 million times brighter than Pluto (if you can find it!)

• Saturn: 150,000 times brighter than Pluto

Big telescopes excel at looking at objects like the Orion Nebula (which appears 7,500 times brighter than Pluto), and the Andromeda Galaxy (which appears 12,000 times brighter than Pluto). Worse still, both those objects take up quite a lot more sky than even the Moon. Looking at a picture like this, Pluto would occupy a fraction of a fraction of a pixel in size, and be a fraction of a fraction as bright.

 

[orienteer]

Billions; nice job with your graphic arts. a picture IS worth a thousand words

 

[billions]

Thanks!

The last thing I was going to mention on Pluto is that it is nearly unique in the astronomical community in that it wasn't discovered due to it's apparent size or brightness, but rather, it's gravity!

As the story goes, Clyde Tombaugh inferred that Pluto must be out there based on it's gravitational influence on Neptune's orbit. After some lengthy calculations he had a decent idea of where this planet should appear in the sky. After many nights of developing images looking directly where this planet should be, he finally saw it! To me the most impressive part is that he was able to turn the growing observational error in Neptune's orbit into the coordinates of this mystery planet.

I suppose black holes and dark matter are also located due to their gravitational effects, but that's for a whole new story there...

 

[AdmiralQuality]

billions, that's a fantastic illustration, thanks for doing that!

I assume that these are the maximum apparent sizes we see when each respective planet is as close to Earth as it ever gets?