Eris outweighs Pluto by 27%.

3488 · Jun 15, 2007

Eris outweighs Pluto considerably. Article here. The Eris moon, Dysnomia appears to have shrunk from 400 KM to 150 KM, therefore similar in size to the Pluto moon Hydra. These new results are based on Hubble Space Telescope observations. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Jun 15, 2007

Andrew, I noticed too with disappointment the severe shrinking of Dysnomia when I read the article. Because this will decrease considerably potential tidal energy dissipation in Eris, and prevent Dysnomia from being another Enceladus. Given the diameter ratio to Eris, consistent with difference in magnitude, it is difficult to understand why 400km were considered in the first place, in retrospect. I wonder whether someone did not confuse diameter and radius. Another source of disappointment was the absence of other moonlets, despite long observations from Hubble, making their absence very likely. And so no prospect for unstabilities in the CoG of the subsystem. Hopefully there should be soon other dwarves announced, by the hundreds... And so tens of multiple subsystems with large bodies

alokmohan · Jun 16, 2007

They want scoop news everyday.Hang on with repeating story.

3488 · Jun 18, 2007

Hi borman, Brilliant question. AFAIK, Eris is coated in methane ice, in fact its spectra is not too different to Pluto. The main difference is that Eris is grey, where as Pluto is reddish (exposure to short wave radiation)??? You are correct in that a steller occultation is required to reveal more. It is fascinating that Charon shows crystalline ice where as Pluto does not!!! New Horizons should answer that. I wonder if the Methane ice is covering any cryastalline ice, thus masking it? Charon does not show Methane ice. Hi Joel, Yes I too am disappointed that Dysnomia has shrunk. As you say ,these where very intensive observations with the HST & they failed to show more moons. Having said that, Eris is reasonably dense, so could be a differentated object, like Jupiter's Ganymede so there could have been cryovolcanism in the past. Until there is a Voyager / New Horizons type mission, I fear that we will not know for sure. Hi alokmohan, this is brand new material. This sort of information, some of us have been waiting for, for quite some time. Dysnomia was always the key to this, observing the orbit of this moon around Eris. I agree, with you, that it will probably be repeated unnecessarily elsewhere, very true. Hopefully these observatrions will answer other questions too, such as rotational rate, direction & tilt???? Also were albedo variations detected?? Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Jun 19, 2007

APOD Eris & Dysnomia. The Sun looks far too large however. Currently from Eris & Dysnomia, the Sun appears 19.5" across, magnitude -16.81, in front of southern Virgo, near the border with Corvus. Interesting that Eris is made to look a lot like the Jupiter moon Europa. Tuesday 19th June 2007. Dysnomia orbits Eris once every 15 days, 18 hours & 29 minutes. Dysnomia orbits Eris at a distance of 37,430 kilometres / 23,244 miles in an almost perfectly circular, prograde orbit (counter clockwise as seen from the north), eccentricity of less than 0.001. Seeing as MOST planetary satellites orbit their primaries in the some direction as the primary rotates, this most likely means that the rotaion of Eris is also prograde (like the Earth). Also Dysnomia appears to orbit Eris at an inclination of only one arc minute, from the plane of Eris's orbit around the Sun. If Dysnomia is in orbit around the equator of Eris (by no means proven), then Eris, orbits the Sun, pretty well bolt upright. Strange considering that the orbit of Eris is so steeply inclined (44 degrees) to the invariable plane. In other words, if true, Eris will have no 'seasons' as such. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Jun 21, 2007

Hi Joel, In answer to your post here. I put my answer here as it is specific to Eris & Dysnomia. True, the tidal dissipation between Eris & Dysnomia is virtually zero, but seeing as Eris is denser than first thought, there may have been more radioactive heating in its earlier days, so there may be evidence still of historic cryovolcanism. I doubt very much, like yourself that anything is happening now apart from the odd frest impact crater. I may be out of the loop for a little while. Computer problems are fixed, but now have issues of an unreliable line (again). So I am going to give British Telecom a right b********g. This has been going on for more than long enough. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

3488 · Jun 21, 2007

This just in. Taken a long time: August 2006. From Hubble Site. NASA's Hubble Space Telescope has teamed up with the W.M. Keck Observatory to precisely measure the mass of Eris, the largest member of a new class of dwarf planets in our solar system. Eris is 1.27 times the mass of Pluto, formerly the largest member of the Kuiper Belt of icy objects beyond Neptune. Hubble observations in 2006 showed that Eris is slightly physically larger than Pluto. But the mass could only be calculated by observing the orbital motion of the moon Dysnomia around Eris. Multiple images of Dysnomia's movement along its orbit were taken by Hubble and Keck. Astronomer Mike Brown of the California Institute of Technology in Pasadena, Calif. and colleagues also report in this week's Science Magazine that Dysnomia is in a nearly circular 16-day orbit. This favors the idea that Dysnomia was born out of a collision between Eris and another Kuiper Belt object (KBO). A gravitationally captured object would be expected to be in a more elliptical orbit. The satellites of Pluto, as well as the Earth-Moon system are also believed to have been born out of a collision process where debris from the smashup goes into orbit and coalesces into a satellite. By comparing the mass and diameter, Brown has calculated a density for Eris of 2.3 grams per cubic centimeter. This is very similar to the density of Pluto, the large Kuiper Belt object 2003 EL61, and Neptune's moon Triton which is likely a captured KBO. These higher densities imply that these bodies are not pure ice but must have a significant rocky composition. The discovery of Eris in 2005 (originally nicknamed Xena, and officially cataloged 2003 UB313) prompted a debate over the planetary status of Pluto because astronomers realized they would have to call it the "10th" planet if Pluto retained its own <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Jun 21, 2007

Andrew, As far as radioactivity is concerned I am no longer sure of anything. Especially after having seeing the thermal simulations for Ceres. (that is more than ten times lighter) Few hundredths of W/mÂ² are enough to keep a water layer under the surface ice shelf/crust. So, who knows... Joel

dragon04 · Jun 22, 2007

Dysnomia's orbit looks oddly eccentic compared to our own Moon's orbit. What might that imply? <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

3488 · Jun 22, 2007

Hi Dragon04. I wonder if that ellipse is because we are seeing the orbit of Dysnomia around Eris from an angle (like foreshortened craters near the limb of the Moon)? The HST team, reckon the orbit is very nearly a perfect circle, with an eccentricity of less than 1 part in 1,000, & is also inclinded by less the one MINUTE of arc to the orbit Eris makes around the Sun. The Eris & Dysnomia system, however is steeply inclined with respect to the Earth's orbit around the Sun. In fact the plane of Eris's orbit is tilted some 44 degrees from the Invariable Plane of the solar system. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

MeteorWayne · Jun 22, 2007

I think you are misusing the "invariable plane of the solar system" term here. From what I recall, it is the plane of the mass of the solar system, of course dominated by Jupiter. The plane of earths orbit is at most a few degrees from that. (0.1 to 3) wiki link Perhaps you meant the invariable plane of the galaxy? <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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