Comments on: Did Herschel see the rings of Uranus? http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Sun, 05 Jul 2009 20:40:20 +0000 http://wordpress.org/?v=2.3.1 By: Troy http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34928 Troy Wed, 25 Apr 2007 08:00:21 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34928 Maybe seeing rings was an artifact of the optics of his telescope. Chromatic or spherical aberration for example. Maybe it is possible to infer that what he was seeing is a known optical effect. Sometimes people do get lucky; For example it was believed Mars had 2 moons way before they were discovered, though it had to do more with numerology: Earth=1, Mars=2, Ceres=3 (not yet discovered and of course is moonless), Jupiter=4, Saturn=5. Sometimes it is possible to stumble on the correct answer even though the logic or the observation was completely wrong. Maybe seeing rings was an artifact of the optics of his telescope. Chromatic or spherical aberration for example. Maybe it is possible to infer that what he was seeing is a known optical effect. Sometimes people do get lucky; For example it was believed Mars had 2 moons way before they were discovered, though it had to do more with numerology: Earth=1, Mars=2, Ceres=3 (not yet discovered and of course is moonless), Jupiter=4, Saturn=5. Sometimes it is possible to stumble on the correct answer even though the logic or the observation was completely wrong.

]]> By: Josh Colwell http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34927 Josh Colwell Tue, 24 Apr 2007 18:56:22 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34927 In the visible part of the spectrum the rings are much darker than the planet. The composition of the rings includes lots of hydrocarbons which makes the reflectivity very dark. Ground-based observations need to look at particular wavelengths in the near-IR where the planet is dark and the rings are relatively bright in order to detect the rings. The orientation of the rings is easy to predict back in time to 1797 or any other time as long as one assumes that the angular momentum of the rings has not changed significantly. That is, the ring plane is fixed in inertial space, so you just have to track Uranus back in its orbit to get the orientation relative to the Earth. The rings are close to the planet's equatorial plane, and there is no mechanism known that would change that. All that said, I think it is very unlikely that Herschel was able to see the rings. In the visible part of the spectrum the rings are much darker than the planet. The composition of the rings includes lots of hydrocarbons which makes the reflectivity very dark. Ground-based observations need to look at particular wavelengths in the near-IR where the planet is dark and the rings are relatively bright in order to detect the rings. The orientation of the rings is easy to predict back in time to 1797 or any other time as long as one assumes that the angular momentum of the rings has not changed significantly. That is, the ring plane is fixed in inertial space, so you just have to track Uranus back in its orbit to get the orientation relative to the Earth. The rings are close to the planet’s equatorial plane, and there is no mechanism known that would change that.

All that said, I think it is very unlikely that Herschel was able to see the rings.

]]> By: George http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34926 George Tue, 24 Apr 2007 14:22:34 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34926 I can say that when I test Starry Nights Pro Plus on known solar eclipses as far back as 2167 BC in China, that it got it right. But, I do not know if this accuracy extends to planetary inclinations. I can say that when I test Starry Nights Pro Plus on known solar eclipses as far back as 2167 BC in China, that it got it right. But, I do not know if this accuracy extends to planetary inclinations.

]]> By: Stuart http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34925 Stuart Tue, 24 Apr 2007 10:41:56 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34925 I have worries about the accuracy of data in standard planetarium software to accurately predict the inclination of the rings back in the 18th century. Does anyone know how good the input data for Uranus's rings, in software such as Starry Night, is? I have worries about the accuracy of data in standard planetarium software to accurately predict the inclination of the rings back in the 18th century. Does anyone know how good the input data for Uranus’s rings, in software such as Starry Night, is?

]]> By: Bad Albert http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34924 Bad Albert Tue, 24 Apr 2007 05:25:15 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34924 If Herschel could just detect rings with naked-eye observations, wouldn't a long time exposure with IR film easily confirm it? Of course that would have had to wait another century or so for the technology to be developed. If Herschel could just detect rings with naked-eye observations, wouldn’t a long time exposure with IR film easily confirm it? Of course that would have had to wait another century or so for the technology to be developed.

]]> By: bswift http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34923 bswift Tue, 24 Apr 2007 05:15:55 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34923 Right, Sam. Phil's kindly linked the image to a Keck press release for your enjoyment. :) Right, Sam. Phil’s kindly linked the image to a Keck press release for your enjoyment. :)

]]> By: bswift http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34922 bswift Tue, 24 Apr 2007 05:13:30 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/23/did-herschel-see-the-rings-of-uranus/#comment-34922 'Exothermic' isn't really the correct word for it, Thomas. 'Exothermic' would imply a release of internal energy as a result of some process. I think that you're thinking that the rings looks like they are hotter than the planet because they are brighter. However, here, the rings are actually very bright compared to the planet because the image was purposefully taken in a narrow band filter around 2.2 microns (10^-6 meters) in the middle of a big methane absorption feature. The planet emits little light here and the rings shine brightly in contrast. ‘Exothermic’ isn’t really the correct word for it, Thomas. ‘Exothermic’ would imply a release of internal energy as a result of some process. I think that you’re thinking that the rings looks like they are hotter than the planet because they are brighter.

However, here, the rings are actually very bright compared to the planet because the image was purposefully taken in a narrow band filter around 2.2 microns (10^-6 meters) in the middle of a big methane absorption feature. The planet emits little light here and the rings shine brightly in contrast.

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