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Afrocentric
2009-Nov-27, 10:40 PM
Have we actually seen Ceres and does it have a moon?

Nick Theodorakis
2009-Nov-27, 11:10 PM
It's been imaged by the Hubble Space Telescope, and it has no moon detectable by the HST. The Dawn Space Probe is on the way to the asteroid belt and should have some close-up pics by 2015.

Nick

Hornblower
2009-Nov-27, 11:11 PM
Have we actually seen Ceres and does it have a moon?

Ceres was discovered visually with a telescope, a small one by today's standards, in the year 1801. As far as I know it does not have a moon.

Celestial Mechanic
2009-Nov-28, 05:58 AM
Ceres was discovered visually with a telescope, a small one by today's standards, in the year 1801. As far as I know it does not have a moon.I have seen it in binoculars. It's a matter of knowing when and where to look. As for the satellite, I would be very surprised if 1 Ceres does not have one, we'll just have to wait and see.

Nick Theodorakis
2009-Nov-28, 06:25 AM
BTW, if you mean is it ever visible to the naked eye, then no. It never gets brighter than magnitude 6.7, according to the wiki (http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29).

Also, welcome to the board.

Nick

Hans
2009-Nov-28, 10:52 AM
Trivia on Ceres

In his sequal to HG Well's War of the World Garret P Serviss had Ceres at war with the Martians and populated by 40 foot greek god looking giants......All of this was in the book 'Edison's Conquest of Mars' printed in 1898. A scream of a space opera.

glappkaeft
2009-Nov-29, 02:19 PM
BTW, if you mean is it ever visible to the naked eye, then no. It never gets brighter than magnitude 6.7, according to the wiki (http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29).

At a truly dark site and good night vision you can see fainter objects than that although it might be hard to identify it. Several members in our astronomy club including me have seen objects in the 7.0-7.2 range. We have however not tried spotting Neptune or any of the major asteroids since here in Sweden (same latitude as Anchorage, Alaska) they are usually pretty close to the horizon.

Hipkins68
2009-Dec-05, 03:54 AM
If Ceres does have a moon wouldn't it be considered a planet? I believe this was one of the characteristics that defined a planet. If there is a moon it must be a small one. I still don't understand why Pluto was demoted back in 2006 by the IAU. The eccentricity of its orbit should have nothing to do with the classification. If I am not mistaken Ceres is 2 or 3 times bigger than any other object in the asteroid belt.

Craig

Murphy
2009-Dec-06, 05:47 AM
If Ceres does have a moon wouldn't it be considered a planet? I believe this was one of the characteristics that defined a planet. If there is a moon it must be a small one. I still don't understand why Pluto was demoted back in 2006 by the IAU. The eccentricity of its orbit should have nothing to do with the classification. If I am not mistaken Ceres is 2 or 3 times bigger than any other object in the asteroid belt.

Craig

I don't think having a moon will have any bearing on it being a planet or not. Eris and probably many other Kuiper belt objects / Dwarf planets have moons. And Ceres is already a planet of sort, at the same time Pluto was "demoted", Ceres was "promoted" from an asteroid to a Dwarf planet.

I you don't understand the IAU definition then you should read the Wiki articles... http://en.wikipedia.org/wiki/IAU_definition_of_planet, http://en.wikipedia.org/wiki/Definition_of_planet.


I have seen it in binoculars. It's a matter of knowing when and where to look. As for the satellite, I would be very surprised if 1 Ceres does not have one, we'll just have to wait and see.

You really think Ceres will have a moon? Hmm I had never thought of the possibility before, but seeing as it is in the asteroid belt I guess there are a lot of possible moons to pick up.

01101001
2009-Dec-06, 06:16 AM
I believe this was one of the characteristics that defined a planet.

Ex-planet Pluto has 3 known moons.

slang
2009-Dec-06, 12:27 PM
If Ceres does have a moon wouldn't it be considered a planet?

Asteroid 243 Ida (http://en.wikipedia.org/wiki/243_Ida) has a moon.

slang
2009-Dec-06, 12:29 PM
Have we actually seen Ceres and does it have a moon?

Ceres and Vesta (http://antwrp.gsfc.nasa.gov/apod/ap070622.html). No moons, so far.

dhd40
2009-Dec-06, 01:33 PM
You really think Ceres will have a moon? Hmm I had never thought of the possibility before, but seeing as it is in the asteroid belt I guess there are a lot of possible moons to pick up.

Itīs not that easy to "pick up" a moon. Nevertheless, I would also expect Ceres to have a moon, born from an Earth-Moon-like process

Orion's Fan
2009-Dec-06, 08:06 PM
Asteroid 243 Ida (http://en.wikipedia.org/wiki/243_Ida) has a moon.

Dactyl is a favorite of mine.

Murphy
2009-Dec-07, 12:04 AM
Itīs not that easy to "pick up" a moon. Nevertheless, I would also expect Ceres to have a moon, born from an Earth-Moon-like process

Wouldn't an Earth-Moon type impact formation suggest a rather large moon?

I think Ceres is already too well studied for it to have a large moon, I would guess that any moon would have to be a small captured asteroid that has been overlooked so far. Anyway, we will know for sure when Dawn gets there.

dhd40
2009-Dec-07, 01:48 PM
Wouldn't an Earth-Moon type impact formation suggest a rather large moon?

No, not at all. By "Earth-Moon type" I simply think of an impact. The size of the moon would depend on many parameters, like relative speed, angle of impact, size/mass/density, etc of the two bodies, etc, ...


I would guess that any moon would have to be a small captured asteroid

No. It has been said here many times before (and itīs true) that "capturing" asks for more than two objects

fifelad55
2009-Dec-07, 05:06 PM
I have seen it in binoculars. It's a matter of knowing when and where to look. As for the satellite, I would be very surprised if 1 Ceres does not have one, we'll just have to wait and see.

You obviously have clearer and darker skies than I have. I was on my condo roof last night around 9.30 as part of a sidereal time experiment for a module I'm doing with the University of Central Lancashire and the limiting naked eye magnitude was about 2!

It has been worse though! One night I estimated it to be 1.5!!!! Through binoculars, the limiting magnitude was perhaps 3.5!

On a good night, I can see down to about 3.5 with the naked eye though a bit better than 4 to the west where the light pollution isn't so bad.

Alan

Jeff Root
2009-Dec-07, 08:48 PM
The opposite of what dhd40 said. An Earth-Thea type giant impact creates
a moon by uplifting a sizeable quantity of material from the larger body which
then collides, more or less circularizing the orbits of the colliding particles.
An impact on Ceres by a body much smaller than Ceres would just spew the
particles out in all directions because they would not have enough mass to
pull themselves together by their own gravity, collide with one another, and
go into circular orbits.

The third body in a three-body capture can be the Sun. That is how Jupiter
captured its outermost moons, which are in retrograde orbits.

-- Jeff, in Minneapolis

Celestial Mechanic
2009-Dec-08, 05:47 AM
I have seen it in binoculars. It's a matter of knowing when and where to look.{Snip!}You obviously have clearer and darker skies than I have. I was on my condo roof last night around 9.30 as part of a sidereal time experiment for a module I'm doing with the University of Central Lancashire and the limiting naked eye magnitude was about 2! {Snip!}Make that "had". That was back when I was at the University of Oklahoma, in Norman, Oklahoma. I could walk a short distance and almost be under rural skies with a limiting magnitude of 4.5 to 5.

Nowadays I live in Milwaukee, Wisconsin a mile and a half from downtown, a block away from an expressway (and its towering streetlamps) and two blocks due south of the world's largest four-face clock--each face of which is lit up by hundreds of fluorescent bulbs behind a translucent white clock-face that can be seen up to 25 miles away on Lake Michigan.

Needless to say, I won't be doing much observing here. :sad:

Edited to add: And even if I do, it won't be my 5.25" telescope discovering any satellite of 1 Ceres.

slang
2009-Dec-08, 08:16 AM
Look what I found: The absence of satellites of asteroids (http://adsabs.harvard.edu/abs/1987Icar...70..257G)


A CCD-imaging survey was made for satellites of minor planets at distances of about 0.1 to 7 arcmin from 1 Ceres, 2 Pallas, 4 Vesta, 6 Hebe, 7 Iris, 8 Flora, 15 Eunomia, 29 Amphitrite, 41 Daphne, and 44 Nysa, with cursory inspection of 192 Nausikaa. Satellites larger than 3 km were not found in this work, nor in previous photographic surveys. Not finding them appears to be consistent with theoretical studies of collisions in the asteroid belt by several authors. The satellites would have to be larger than at least 30 km to be collisionally stable. Taking tidal stability into account, it is concluded that the only possible satellites for main-belt asteroids are near-contact binaries. The only other rare possibility for a satellite might be a piece of debris from a recent collision.

(emphasis mine) It's a 1987 paper, and I don't know how it could be affected by new observations. The paper itself seems to be behind a pay wall.

agingjb
2009-Dec-08, 08:52 AM
Interesting; would the conclusions of the study have ruled out Dactyl?

dhd40
2009-Dec-08, 11:12 AM
An impact on Ceres by a body much smaller than Ceres would just spew the
particles out in all directions because they would not have enough mass to
pull themselves together by their own gravity, collide with one another, and
go into circular orbits.
-- Jeff, in Minneapolis

I see. But wouldnīt it be possible for larger chunks to be spewn out?

Jeff Root
2009-Dec-08, 04:18 PM
Yes, although the size of chunks is limited by the strength of the material.
Frangible rock crumbles on collision, while strong material requires high-energy
impacts to fracture. The result tends to be smaller chunks either way.

Some chunks could end up in orbit. Small chunks will fairly quickly be pushed
out of their orbits by solar light pressure. All would eventually be pulled out
of their orbits by gravitational interaction with the Sun and nearby planets,
especially Jupiter. Larger chunks might take millions of years to either escape
from or crash into their primary. A few million years isn't very long.

-- Jeff, in Minneapolis

Swift
2009-Dec-08, 07:38 PM
It's been imaged by the Hubble Space Telescope, and it has no moon detectable by the HST. The Dawn Space Probe is on the way to the asteroid belt and should have some close-up pics by 2015.

Nick
By the way here is a link (http://hubblesite.org/newscenter/archive/releases/2005/27/image/a) to those pictures.

NASA's Hubble Space Telescope took these images of the asteroid 1 Ceres over a 2-hour and 20-minute span, the time it takes the Texas-sized object to complete one quarter of a rotation. One day on Ceres lasts 9 hours.

Hubble snapped 267 images of Ceres as it watched the asteroid make more than one rotation. By observing the asteroid during a full rotation, astronomers confirmed that Ceres has a nearly round body like Earth's. Ceres' shape suggests that its interior is layered like those of terrestrial planets such as Earth. Ceres may have a rocky inner core, an icy mantle, and a thin, dusty outer crust inferred from its density and rotation rate.

The bright spot that appears in each image is a mystery. It is brighter than its surroundings. Yet it is still very dark, reflecting only a small portion of the sunlight that shines on it.

dhd40
2009-Dec-09, 03:11 PM
Some chunks could end up in orbit. Small chunks will fairly quickly be pushed
out of their orbits by solar light pressure. All would eventually be pulled out
of their orbits by gravitational interaction with the Sun and nearby planets,
especially Jupiter. Larger chunks might take millions of years to either escape
from or crash into their primary. A few million years isn't very long.

-- Jeff, in Minneapolis

(my bold)

Thanks. Sounds reasonable.
Especially the few million yearsī blink of an eye :)

Rick1067
2009-Dec-21, 06:05 PM
If 267 images of Ceres were taken why are only about 8 used? Where are the rest? Also Why are they so blurry? If the HST can take images of galaxies light years away why no clear images of something so close?

Murphy
2009-Dec-21, 06:32 PM
If 267 images of Ceres were taken why are only about 8 used? Where are the rest? Also Why are they so blurry? If the HST can take images of galaxies light years away why no clear images of something so close?

Probably because those Galaxies are so much more massively big than a small planetoid.

Don't worry too much, in 2015 the Dawn Spacecraft will reach Ceres and go into orbit, it will take excellent close up pictures and should show us what this little world is really like. Wiki article... http://en.wikipedia.org/wiki/Dawn_(spacecraft), and NASA... http://dawn.jpl.nasa.gov/.

Hornblower
2009-Dec-21, 11:06 PM
If 267 images of Ceres were taken why are only about 8 used? Where are the rest? Also Why are they so blurry? If the HST can take images of galaxies light years away why no clear images of something so close?

If we enlarge a tiny portion of a typical HST galaxy image to the same image scale as the Ceres images, it will look just as fuzzy.

Jens
2009-Dec-22, 02:52 AM
If 267 images of Ceres were taken why are only about 8 used? Where are the rest? Also Why are they so blurry? If the HST can take images of galaxies light years away why no clear images of something so close?

Just to add a tiny bit, you can clearly see the moon with your naked eye, but you can't make out an ant just 30 feet away. It's basically the same situation.