Earth and Space News: Sir William Herschel Uranus discovery 1781

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Friday, March 13, 2015

Uranus Discovery 234 Years Ago on March 13, 1781, by Sir William Herschel

Summary: Friday, March 13, 2015, marks the 234th anniversary of the discovery of Uranus by Sir William Herschel.

March 13, 2015, which falls on a Friday, commemorates the 234th anniversary of the discovery of Uranus by Sir William Herschel on March 13, 1781, which fell on a Tuesday.

Born into a musical family in Hanover, in today's north central Germany, Friedrich Wilhelm Herschel (Nov. 15, 1738-Aug. 25, 1822) first applied his diligence and genius to music, playing at least four instruments (harpsichord, oboe, organ, violin) and composing in a variety of musical genres, including 24 symphonies. With the French occupation of Hanover in the wake of their victory on July 26, 1757, at the Battle of Hastenbeck, William, then aged 19, migrated with his older brother Heinrich Anton Jacob Herschel (November 1734-1792) to England, where he anglicized his first and second names to Frederick William.

Through his musical interests, William developed a passion for mathematics and lenses that led him to astronomy. William began building his own versions of reflecting telescopes, a mid-17th century invention.

Scientific genius Sir Isaac Newton (Dec. 25, 1642-March 20, 1726/7) generally is credited with completing the first functional reflecting telescope in 1668. Also known as a reflector, a reflecting telescope is a type of optical telescope based upon catoptrics (Greek: κάτοπτρον, katoptron, "mirror"), the branch of optics (study of light) using mirrors to gather and focus light.

By May 1773, William was an impassioned sky gazer, searching with his homemade, customized telescopes for double stars, which are star pairs seemingly in proximity in the sky, and also for planets (Ancient Greek: ἀστήρ πλανήτης, astēr planētēs, "wandering star").

With his appointment in 1766 as organist of Octagon Chapel in the resort city of Bath in England's South West county of Somerset, William had settled into a small, Georgian-style townhouse with three stories plus an attic and a basement at 19 New King Street. In the property's garden, off the basement's rear kitchen, William built a workshop for his design experiments on telescopes. William logged many hours -- with the assistance of his sister Caroline (March 16, 1750-Jan. 9, 1848) -- polishing his telescopes' mirrors, made of speculum metal, a mixture of two-thirds copper and one-third tin.

On Friday, March 13, 1981, the 200th year anniversary of William's planetary discovery, his townhouse opened as the Herschel Museum of Astronomy, under the ownership of the Herschel House Trust.

It was through a 7-foot telescope with a 6.2-inch aperture that he had made in his workshop that William espied Uranus on Tuesday, March 13, 1781. He first assumed that the celestial body was either a comet or a star. His sister Caroline took notes as he discovered his sighting.

By 1783, William accepted his discovery as a planet, which he named Georgium Sidus ("George's Star") in honor of George III (June 4, 1738-Jan. 29, 1820), whose kingly reign over Great Britain and Ireland began Oct. 25, 1760.

In 1784, French astronomer Joseph Jérôme Lefrançois de Lalande (July 11, 1732-April 4, 1807) proposed renaming the seventh planet from Earth's sun as Herschel.

Included among mythology-based names as alternatives to the Georgian Planet was Uranus, proposed in 1785 by German astronomer Johann Elert Bode (Jan. 19, 1747-Nov. 23, 1826) to conform with the patronymic chain of Jupiter as father of Mars, Saturn as father of Jupiter and Uranus as father of Saturn. The name of Uranus achieved universal acceptance in 1850 with its inclusion in The Nautical Almanac, published as a guide for celestial navigation since 1767.

In the intervening two and one-third centuries that have passed since Uranus caught William's attention, the blue-green planet continues to stand out. Uranus is honored as the first planet to be discovered by the fairly newly invented reflecting telescope, trailblazing harbinger of continual discoveries, including Neptune in 1846, on the time-space continuum. The blue-green ice giant also is the only solar system planet with the Greek form (Ancient Greek: Οὐρανός,Ouranos, "heaven, sky"), not the Roman form (Latin: Caelus), of a deity from classical mythology.

replica of telescope through which William Herschel discovered the planet Uranus, Herschel Museum of Astronomy, Bath, Somerset, South West England: Mike Young, Public Domain, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

false color image of Uranus generated by Erich Karkoschka from data taken Aug. 8, 1998, with Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer; credit NASA/JPL/STScI: "Hubble Finds Many Bright Clouds on Uranus," NASA image Aug. 24, 2000, May be used for any purpose without prior permission, via NASA Jet Propulsion Laboratory @ http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA02963;
"PIA02963: Hubble Finds Many Bright Clouds on Uranus," May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA02963

replica of telescope through which William Herschel discovered the planet Uranus, Herschel Museum of Astronomy, Bath, Somerset, South West England: Mike Young, Public Domain, via Wikimedia Commons @ http://commons.wikimedia.org/wiki/File:HerschelTelescope.jpg

For further information:

Herschel, Mr., and Dr. Watson, Jun. of Bath. "Account of a Comet. Read April 26, 1781." Philosophical Transactions of the Royal Society of London, vol. LXXI [71] (1 January 1781): 492 - 501.
Available via Wikimedia Commons @ http://commons.wikimedia.org/wiki/File:Herschel-Account_of_a_Comet.pdf

“IoE Number 443114; Nos. 18 – 19 New King Street.” Images of England.
Available @ http://www.imagesofengland.org.uk/details/default.aspx?id=443114

Marriner, Derdriu. "Uranus the Blue Green Ice Giant: Sideways Seventh Planet From the Sun." Earth and Space News. Friday, March 13, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/03/uranus-blue-green-ice-giant-sideways.html

Mullaney, James. The Herschel Objects and How to Observe Them. New York: Springer Science+Business Media, 2007.

Talcott, Richard. “The Sky This Week: March 6 – 15, 2015.” Astronomy Magazine > Observing > The Sky This Week. March 6, 2015.
Available @ http://astronomy.com/observing/sky-this-week/2015/03/march-615-2015

“Uranus: Overview.” NASA Solar System Exploration > Planets > Uranus.
Available @ http://solarsystem.nasa.gov/planets/profile.cfm?object=Uranus

Wednesday, February 16, 2011

Stuart Eves Credits William Herschel With Uranian Epsilon Ring in 1789

Summary: Surrey Satellite Technology Limited’s Stuart Eves suggests William Herschel saw Uranian epsilon ring in 1789, in a new look at Herschel’s notes.

Surrey Satellite Technology Limited’s Stuart Eves suggests William Herschel saw the Uranian epsilon ring in 1789, according to the astrophysicist and space safety expert’s new look at the German-British astronomer’s observations.

Dr. Stuart Eves officially presented his new look at Uranian ring observations made by William Herschel (Nov. 15, 1738-Aug. 25, 1822) at the 2007 National Astronomy Meeting. The Royal Astronomical Society (RAS) held the prestigious annual conference from Monday, April 16, to Friday, April 20, 2007, at the University of Central Lancashire’s (UCLan) Centre for Astrophysics in Preston, North West England.

William Herschel (Nov. 15, 1738-Aug. 25, 1822) shared findings from his 10-year search for a Uranian ring system at the Royal Society of London’s Dec. 14, 1797, meeting. He reported ringed and ringless observations.

Herschel extensively described ringed views that he obtained on March 16, 1789. “The ring is short, not like that of Saturn . . . . It is remarkable that the two annae seem of a colour a little inclined to red . . . .” (page 68).

In his “Remarks Upon the Foregoing Observations,” however, Herschel cited a ringless view as critical to his assessment of a ringless system. “Placing therefore great confidence on the observation of March 5, 1792, supported by my late views of the planet, I venture to affirm, that it has no ring in the least resembling that, or rather those, of Saturn” (page 70).

Yet, in a post-1792 observation, he had noted: “Dec. 4, 1793. 7-feet reflector, power 287. The Georgian planet is not so well defined as, from the extraordinary distinctness of my present 7-feet telescope, it ought to be. There is a suspicion of some apparatus about the planet” (page 69).

In a re-evaluation of Herschel’s annular observations, Dr. Eves finds a consistent rightness of details with the Uranian system’s now-known epsilon (ε) ring.

In an April 16, 2007, press release, Royal Astronomical Society press officers Robert Massey and Anita Heward reveal: “Herschel got a lot of things right, notes Dr. Eves. He has a ring of roughly the correct size relative to the planet, and he also has the orientation of this ring in the right direction. In addition, he accurately describes the way the appearance of the ring changes as Uranus moves around the Sun, and he even gets its colour right. Uranus’s Epsilon ring is somewhat red in color, a fact only recently confirmed by the Keck telescope, and Herschel mentions this in his paper.”

Dr. Eves offers several explanations for the lack of observations of the Uranian ring system in the 190 years between Herschel’s discernments, which date back, at least, to March 4, 1787, and the serendipitous detection of at least five rings on March 10,1977, via the Kuiper Airborne Observatory. The planet’s extremely tilted axial geometry greatly limits the opportunities for Earth-based observations of the Uranian ring system.

Also, Dr. Eves references the Cassini-Huygens spacecraft’s observations of the darkening of the Saturnian ring system as a process that might also affect the Uranian ring system. The unknown brightening-darkening phenomena could have operated to brighten the Uranian ring system in the late 18th century.

“If these same mechanisms are also operating at Uranus, then the appearance of its rings could have changed quite markedly over 200 years, making them much harder to detect. Herschel’s observations could thus be proof that planetary ring systems in our solar system are far more dynamic than has previously been supposed,” notes the Royal Astronomical Society’s press release.

Earth’s atmosphere could also interfere with the ring system’s observability, according to BBC News science reporter Paul Rincon’s April 18, 2007, article on Dr. Eves’ presentation. The light pollution and smog created by the Industrial Revolution, which approximately began in the last half of the 18th century, have disturbed the clarity of the night sky environment.

The takeaway for Surrey Satellite Technology Limited’s Stuart Eve’s suggestion that William Herschel could have seen the Uranian epsilon ring is that the astrophysicist and space security expert’s new look at Herschel’s 1797 report of ringed and ringless views of Uranus finds details in the German-British astronomer’s descriptions that accord with the Uranian ring system.

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Uranus and the planet's outermost ring, the epsilon ring; computerized summation of six images obtained Nov. 28, 1985, by spacecraft Voyager 2’s ISS (Imaging Science Subsystem) narrow-angle camera (NAC) from a range of 72.3 million kilometers (44.9 million miles); NASA ID ARC-1985-A86-7001; image credit NASA / JPL-Caltech: Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Video Library @ https://images.nasa.gov/details-ARC-1985-A86-7001

high-resolution image of Uranian system’s bright outer ring, the epsilon ring, obtained Jan. 23, 1986, from a distance of 1.12 million kilometers (690,000 miles) by Voyager 2’s ISS (Imaging Science Subsystem) narrow-angle camera (NAC); the approximate width of 100 kilometers (60 miles) at this section of the epsilon ring shows structural variations of a broad, bright outer component, approximately 40 kilometers (25 miles) wide; a comparably wide, darker middle region; and a narrow, brighter inner strip, approximately 15 kilometers (9 miles) in width; NASA ID PIA01983; ARC-1986-A86-7022; P-2950BW; NASA ID PIA01983; image addition date 1999-06-30; image credit NASA / JPL: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA01983;
Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Video Library @ https://images.nasa.gov/details-PIA01983

For further information:

De Pater, Imke; H.B. Hammel; Mark R. Showalter; and Marcos A. van Dam. “The Dark Side of the Rings of Uranus.” Science, vol. 317, issue 5846: 1888-1890. DOI: 10.1126/science.1148103
Available via AAAS Science @ https://science.sciencemag.org/content/317/5846/1888
Available via ResearchGate @ https://www.researchgate.net/publication/6123185_The_Dark_Side_of_the_Rings_of_Uranus

Dreyer, J.L.E. (John Louis Emil), comp. The Scientific Papers of Sir William Herschel Including Early Papers Hitherto Unpublished. Vol. I; Vol. II. London, England: The Royal Society and The Royal Astronomical Society, 1912.
Vol. I: Available via HathiTrust @ https://babel.hathitrust.org/cgi/pt?id=mdp.39015010954678
Vol. II: Available via HathiTrust @ https://babel.hathitrust.org/cgi/pt?id=mdp.39015010954744
Vol. I: Available via Internet Archive @ https://archive.org/details/scientificpapers032804mbp/
Vol. II: Available via Internet Archive @ https://archive.org/details/scientificpapers02hersuoft/

Fountain, Henry. “In a Rare View, Rings on Uranus Show Their Changes.” The New York Times > Science > Observatory. Aug. 28, 2007.
Available @ https://www.nytimes.com/2007/08/28/science/28obring.html

Herschel, William. “Observations and Reports Tending to the Discovery of One or More Rings of the Georgian Planet, and the Flattening of Its Polar Regions.” Pages 67-71. “III. On the Discovery of Four Additional Satellites of the Georgium Sidus. The Retrograde Motion of its Old Satellites Announced; and the Cause of Their Disappearance at Certain Distances From the Planet Explained. Read December 14, 1797.” Philosophical Transactions of the Royal Society of London. For the Year MDCCXCVIII, [vol. LXXXVIII (88)], Part I: 47-79. London, England: Peter Elmsly, Printer to The Royal Society, MDCCXCVIII (1798).
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/49109940

Herschel, William. “III. On the Discovery of Four Additional Satellites of the Georgium Sidus. The Retrograde Motion of its Old Satellites Announced; and the Cause of Their Disappearance at Certain Distances From the Planet Explained. Read December 14, 1797.” Philosophical Transactions of the Royal Society of London. For the Year MDCCXCVIII, [vol. LXXXVIII (88)]], Part I: 47-79. London, England: Peter Elmsly, Printer to The Royal Society, MDCCXCVIII (1798).
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/49109920
Available via Royal Society of London Publishing @ https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1798.0005

Herschel, William. “Remarks Upon the Foregoing Observations.” Pages 69-71. “III. On the Discovery of Four Additional Satellites of the Georgium Sidus. The Retrograde Motion of its Old Satellites Announced; and the Cause of Their Disappearance at Certain Distances From the Planet Explained. Read December 14, 1797.” Philosophical Transactions of the Royal Society of London. For the Year MDCCXCVIII, [vol. LXXXVIII (88)], Part I: 47-79. London, England: Peter Elmsly, Printer to The Royal Society, MDCCXCVIII (1798).
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/49109942

Lavoie, Sue, site manager. “PIA01983: Epsilon Ring of Uranus.” NASA Jet Propulsion Laboratory Photojournal. Image addition date 1999-06-30.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA01983

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Marriner, Derdriu. “William Herschel First Glimpsed Uranian Ring System on March 4, 1787.” Earth and Space News. Wednesday, Feb. 2, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/02/william-herschel-first-glimpsed-uranian.html

Marriner, Derdriu. “William Herschel Saw Uranian Rings But Puzzling Views Created Doubt.” Earth and Space News. Wednesday, Feb. 9, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/02/william-herschel-saw-uranian-rings-but.html

Massey, Robert; and Anita Heward. “Did William Herschel Discover the Rings of Uranus in the 18th Century?” Royal Astronomical Society > Press. April 16, 2007.
Available via Internet Archive Wayback Machine @ https://web.archive.org/web/20120910092417/http://www.nam2007.uclan.ac.uk/press_releases.php?news=20070416b

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

New Scientist Monitor Column. “Herschel Saw Rings Round Uranus in 1787.” New Scientist, vol. 74, no. 1052 (May 19, 1977): 396.
Available via Google Books @ https://books.google.com/books?id=Rt5VRWY4aR8C&pg=PA396

Pearson, W. (William), Rev. Plates Belonging to the Second Volume of An Introduction to Practical Astronomy.
Available @ https://digital.tcl.sc.edu/digital/collection/ariail2/id/151

Pearson, W. (William), Rev. “XV. The Herschelian Forty-Feet Telescope (Plate VIII).” An Introduction to Practical Astronomy: Containing Descriptions of the Various Instruments, That Have Been Usefully Employed in Determining the Places of the Heavenly Bodies, With an Account of the Methods of Adjusting and Using Them. Vol. II: 71-78. London, England: Printed for the Author by Messrs. Longman, Rees, Orme, Brown, and Green, 1829.
Available via HathiTrust @ https://hdl.handle.net/2027/nyp.33433090845102?urlappend=%3Bseq=101

Rincon, Paul. “Uranus Rings ‘Were Seen in 1700s.’” BBC News > Science & Environment. April 18, 2007.
Available @ http://news.bbc.co.uk/2/hi/sci/tech/6569849.stm

Schmude, Richard, Jr. “1. The Uranus System: Rings.” Uranus, Neptune, Pluto and How to Observe Them: 27-34. Astronomers’ Observing Guides. New York NY: Springer Science + Business Media LLC, 2008.
Available via ePDF @ https://epdf.pub/uranus-neptune-and-pluto-and-how-to-observe-them-astronomers-observing-guides.html
Available via Google Books @ https://books.google.com/books?id=47azIwooFqEC&pg=PA27

Shiga, David. “Rare View Reveals Dynamic Nature of Uranus’s Rings.” New Scientist > Space. Aug. 23, 2007.
Available @ https://www.newscientist.com/article/dn12529-rare-view-reveals-dynamic-nature-of-uranuss-rings/

SM Dana Centre ‏@DanaCentre. “Have been reading about William Herschel in 'The Age of Wonder'. Looking forward to Stuart Eves' talk on him tonight http://budurl.com/lsf5.” Twitter. Oct. 19, 2010.
Available @ https://twitter.com/DanaCentre/status/27836180852

SM Dana Centre ‏@DanaCentre. “Stuart Eves talks about William Herschel and the rings of Uranus http://budurl.com/ubjm 19 October http://budurl.com/ubjm.” Twitter. Oct. 15, 2010.
Available @ https://twitter.com/DanaCentre/status/27443609239

Young, Kelly. “Uranus Moons Seen Overtaking Each Other for First Time.” NewScientist > Space. May 18, 2007.
Available @ https://www.newscientist.com/article/dn11891-uranus-moons-seen-overtaking-each-other-for-first-time/

Wednesday, February 9, 2011

William Herschel Saw Uranian Rings But Puzzling Views Created Doubt

Summary: Uranus discoverer William Herschel saw Uranian rings but puzzling views created doubt in the German-British astronomer about his annular discoveries.

Rare edge-on view of entire Uranian ring system, obtained Aug. 14, 2007, by NASA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC-2), shows edge-on rings spiking above and below Uranus; blocking out of the planet’s bright glare in the photo interferes with visibility of continuity of ring system across the planet’s face; fan-shaped image artifact represents residual glare, along with edge between inner and outer rings’ exposure: courtesy NASA / ESA (European Space Agency / M. (Mark Robert) Showalter (SETI Institute), via NASA Hubblesite / Space Telescope Science Institute (STScI)

Uranus discoverer William Herschel saw Uranian rings but puzzling views created doubt in the German-British observational astronomer about his annular discoveries.

After discovering Uranus on March 13, 1781, William Herschel (Nov. 15, 1738-Aug. 25, 1822) continued to study the seventh planet from the sun. In a report read at the Royal Society of London’s Dec. 14, 1797, Herschel summarized his 10-year search for definitive observational proof of a ring system on “the Georgian planet.”

He cited his journal entry for Feb. 4, 1787, as detecting “. . . no appearance of any ring . . .” (page 67). He specified that he had examined the planet with his 20-foot reflector telescope, power 300.

Three subsequent journal entries, for March 4 through March 7, noted annular views. The March 7 entry identified “the great ring R” and “Small ring r.”

But, without offering an explanation, Herschel quoted his March 8 entry as stating: “R and r are probably deceptions.”

He expressed doubt in his next journal entry: “Nov. 9. The suspicion of a ring returns often when I adjust the focus by one of the satellites, but yet I think it has no foundation.”

Four entries in 1789 offered positive notations concerning the existence of the Uranian ring system. In particular, Herschel discerned “. . . two annae . . . of a colour a little inclined to red” (page 68) on March 16.

In 1792, however, puzzling views created doubt in the keen-eyed astronomer. His entry for Feb. 26 extensively detailed his efforts to suss Uranus as ringed or ringless.

“6h 34’. My telescope is extremely distinct; and, when I adjust it upon a very minute double star, which is not far from the planet, I see a very faint ray, like a ring crossing the planet, over the centre. This appearance is of an equal length on both sides, so that I strongly suspect it to be a ring. There is, however, a possibility of its being an imperfection in the speculum, owing to some slight scratch: I shall take its position, and afterwards turn the speculum on its axis.

“8h 39’. Position of the supposed ring 55°, 6 from N.P. to S.F.

“9h 56’. I have turned the speculum one quadrant round; but the appearance of the very faint ray continues where it was before, so that the defect is not in the speculum, nor is it in the eye-glass. But still it is now also pretty evident that it arises from some external cause; for it is now in the same situation, with regard to the tube, in which it was 3 1/2 hours ago: whereas, the parallel is differently situated, and the ring, of course, ought to be so too” (pages 68-69).

In assessing his annular study, Herschel assigned great value to these findings. He stated: “. . . the observation of the 26th seems to be very decisive against the existence of a ring” (page 70).

Eight days later, on March 5, Herschel noted: “I viewed the Georgian planet with a newly polished speculum, of an excellent figure. It shewed the planet very well defined, and without any suspicion of a ring” (page 69).

Herschel evaluated the possibility of a ring system in the context of the hypothesis that established his observational guidelines. “When the surmises arose at first, I thought it proper to suppose, that a ring might be in such a situation as to render it almost invisible; and that, consequently, observations should not be given up, till a sufficient time had elapsed to obtain a better view of such a supposed ring, by a removal of the planet from its node. This has now sufficiently been obtained in the course of ten years; for, let the node of the ring have been in any situation whatsoever, provided it kept to the same, we must by this time have had a pretty good view of the ring itself,” he explained (page 70).

Herschel cited the last 1792 ring entry that he presented at the Royal Society’s Dec. 14, 1792, meeting as critical to the conclusion that he was drawing about the seventh planet’s ring system. “Placing therefore great confidence on the observation of March 5, 1792, supported by my late views of the planet, I venture to affirm, that it has no ring in the least resembling that, or rather those, of Saturn.”

Yet, despite his dismissal of a Saturn-styled ring system around his planetary discovery, Herschel included in his Dec. 14, 1792, report an entry for Dec. 4, 1793: “There is a suspicion of some apparatus about the planet” (page 69).

The takeaways for puzzling views creating doubt despite William Herschel’s sightings of the Uranian rings in 1787 and 1789 are that the German-British astronomer concluded his 10-year search for rings around the planet that he had discovered in 1781 by valuing ringless views obtained Feb. 26 and March 5, 1792, but that he included in his Dec. 14, 1797, report an entry for Dec. 4, 1793, that suspects “some apparatus around the planet.”

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

a ringed view of Uranus in a false color image assembled from exposures taken July 3, 1995, by Hubble Space Telescopes Wide Field Planetary Camera-2 (WFPC2); NASA ID: PIA01280; image addition date 1998-08-02; image credit NASA / JPL (Jet Propulsion Laboratory) / STScI (Space Telescope Science Institute): May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA01280;
Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA Image and Video Library @ https://images.nasa.gov/details-PIA01280

For further information:

Herschel, Mr. (William). “XXXII. Account of a Comet. Communicated by Dr. Watſon. Read April 26, 1781.” Philosophical Transactions of the Royal Society of London. Vol. LXXI. For the Year 1781. Part II: 492-501. London, England: Lockyer Davis and Peter Elmsly, Printers to The Royal Society, MDCCLXXXII (1782).
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51826184

Herschel, William. “I. A Letter From William Herschel, Eſq. F.R.S. to Sir Joseph Banks, Bart. P.R.S.” Philosophical Transactions of the Royal Society of London. Vol. LXXIII for the Year 1783. Part I: 1-3.
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51826827

Lavoie, Sue, site manager. “PIA01280: Hubble Captures Detailed Image of Uranus’ Atmosphere.” NASA Jet Propulsion Laboratory Photojournal. Image addition date 1998-08-02.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA18182

Lavoie, Sue, site manager. “PIA18182: Uranus as Seen by NASA’s Voyager 2.” NASA Jet Propulsion Laboratory Photojournal. Image addition date 1986-12-18.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA18182

Levy, David H. Skywatching. Revised and updated. San Francisco CA: Fog City Press, 1994.

Marriner, Derdriu. “William Herschel Discovered Mimas With Newly Built 40-Foot Telescope.” Earth and Space News. Wednesday, Sep. 21, 2019.
Available @ https://earth-and-space-news.blogspot.com/2011/09/william-herschel-discovered-mimas-with.html

Marriner, Derdriu. “William Herschel Discovered Saturnian Moon Mimas Sept. 17, 1789.” Earth and Space News. Wednesday, Sept. 14, 2011.
Available @ https://earth-and-space-news.blogspot.com/2011/09/william-herschel-discovered-saturnian.html

Moore, Patrick, Sir. Philip’s Atlas of the Universe. Revised edition. London UK: Philip’s, 2005.

Rincon, Paul. “Uranus Rings ‘Were Seen in 1700s.’” BBC News > Science & Environment. April 18, 2007.
Available @ http://news.bbc.co.uk/2/hi/sci/tech/6569849.stm

Schmude, Richard, Jr. “1. The Uranus System: Rings.” Uranus, Neptune, Pluto and How to Observe Them: 27-34. Astronomers’ Observing Guides. New York NY: Springer Science + Business Media LLC, 2008.
Available via ePDF @ https://epdf.pub/uranus-neptune-and-pluto-and-how-to-observe-them-astronomers-observing-guides.html Available via Google Books @ https://books.google.com/books?id=47azIwooFqEC&pg=PA27

Villard, Ray; and Mark Showalter. “Going, Going, Gone: Hubble Captures Uranus’s Rings on Edge.” NASA Hubblesite > News > News Releases. Release ID 2007-32. Aug. 23, 2007. Available @ https://hubblesite.org/contents/news-releases/2007/news-2007-32.html

Young, Kelly. “Uranus Moons Seen Overtaking Each Other for First Time.” NewScientist > Space. May 18, 2007. Available @ https://www.newscientist.com/article/dn11891-uranus-moons-seen-overtaking-each-other-for-first-time/

Wednesday, February 2, 2011

William Herschel First Glimpsed Uranian Ring System on March 4, 1787

Summary: German-British astronomer William Herschel first glimpsed the Uranian ring system on March 4, 1787, less than six years after discovering Uranus.

William Herschel’s sketches of Uranian ring system on March 4 and March 5, 1787 (figure 7) and on March 16, 1787 (figures 8-10); engraving by James Basire I (Oct. 6, 1730-Sept. 6, 1802) and/or James Basire II (Nov. 12, 1769-May 13, 1822); W. Herschel, “On the Discovery of Four Additional Satellites” (1797), Tab. III, between pages 78 and 79: Public Domain, via Biodiversity Heritage Library

German-British astronomer William Herschel first glimpsed the Uranian ring system on March 4, 1787, less than six years after his discovery of the ring system’s parent body, ice giant planet Uranus.

William Herschel (Nov. 15, 1738-Aug. 25, 1822) discovered the seventh planet from the sun on March 13, 1781. He referred to his planetary discovery as Georgium Sidus and as “Georgian planet” in honor of his royal patron, King George III (June 4, 1738-Jan. 29, 1820).

The conscientious observational astronomer continued to scrutinize the Uranian system. He evaluated the planet’s shape and considered the possibility of a ring or rings as shaping the planet’s outline. He detailed his ring search in an article read at the Royal Society’s Dec. 14, 1797, meeting.

Seven of the entries from Herschel's observational journals for 1787 and 1789 noted his detection of a ring system for the planet. He included four sketches of his sightings in his report to the Royal Society.

On Feb. 4, 1787, Herschel viewed Uranus with his 20-foot reflector telescope, power 300. In his observational journal entry, he noted: “Well defined; no appearance of any ring; much daylight” (page 67).

Yet, one month later, on March 4, he pondered: “I begin to entertain a suspicion that the planet is not round. When I see it most distinctly, it appears to have double, opposite points. See figure 7. Perhaps a double ring; that is, two rings, at rectangles to each other.”

He reported for the following day, March 5: “The Georgian Sidus not being round, the telescope was turned to Jupiter. I viewed that planet with 157, 300, and 480, which shewed it perfectly well defined. Returning to the Georgian planet, it was again seen affected with projecting points. Two opposite ones, that were large and blunt, from preceding to following; and two others, that were small and less blunt, from north to south. See figure 7.”

He reported that two days later, on March 7: “Position of the great ring R, from 70° S.P. to 70° N.F. Small ring r, from 20° N.P. to 20° N.F. 600 shewed R and r. 800 R and r. 1200 R and r.”

The next annular sighting reported by Herschel occurred a little over one year 11 and one-half months later, on Feb. 22, 1789. He summarized his findings as: “A ring was suspected.”

His entry for March 16, 1789, extensively described his ring findings: “7h 37’. I have turned my speculum 90° round. A certain appearance, owing to a defect which it has contracted by exposure to the air since it was made, is gone with it; (see fig. 9 and 10;) but the suspected ring remains in the place where I saw it last.

“7h 50’. Power 471 shews the same appearance rather stronger. Power 589 still shews the same.

“Memorandum. The ring is short, not like that of Saturn. It seems to be as in figure 8; and this may account for the great difficulty of verifying it. It is remarkable that the two ansæ seem of a colour a little inclined to red. The blur occasioned by the fault of the speculum is, to-night, as represented in figure 9. The other evening it was as in figure 10; and the ring is likewise as it was the same evening” (page 68).

Four evenings later, on March 20, Herschel observed: “7h 53’. When the satellites are best in focus, the suspicion of a ring is the strongest.”

Herschel’s entry for Dec. 15, almost nine months later, announced: “The planet is not round, and I have not much doubt but that it has a ring.”

The takeaways for William Herschel’s first glimpse of the Uranian ring system on March 4, 1787, are that he reported his annular search at the Dec. 14, 1787, meeting of The Royal Society of London; that only one of the entries (for Feb. 4, 1787) in his observational journals for 1787 and 1789 noted the absence of a ring system; and that the German-British astronomer included four sketches of his ringed sightings in his report.

The National Aeronautics and Space Administration’s (NASA) Hubble Space Telescope captured ever more oblique (shallower) tilts of Uranus, as viewed from Earth; the Uranian ring system culminated in fully edge-on view (right), obtained Aug. 14, 2007, by Hubble’s Wide Field Planetary Camera 2 (WFPC-2): courtesy NASA / ESA (European Space Agency / M. (Mark Robert) Showalter (SETI Institute), via NASA Hubblesite / Space Telescope Science Institute (STScI)

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

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