John Herschel Made Four Observations of Lenticular Galaxy NGC 7302

Summary: John Herschel made four observations of lenticular galaxy NGC 7302, which his father, Uranus discoverer William Herschel, discovered Oct. 3, 1785.

Sir William Herschel’s 20-foot reflecting telescope, through which Sir William discovered NGC 7302 on Oct. 3, 1785, and used for his son’s four observations of NGC 7302: W. Herschel, W. Bunce and J. Walker’s William Herschel’s Twenty-Foot Reflecting Telescope (1794 print), CC BY 4.0 International, via University of Cambridge Institute of Astronomy Library

John Herschel made four observations of lenticular galaxy NGC 7302, which was discovered Oct. 3, 1785, by his father, Uranus discoverer William Herschel.

German-British astronomer and composer Sir William Herschel (Nov. 15, 1738-Aug. 25, 1822) discovered NGC 7302 on Oct. 3, 1785, four years six-plus months after his March 13, 1781, discovery of solar system planet number seven, Uranus. His discovery of NGC 7302 appears as entry IV-31 in his Catalogue of a Second Thousand of New Nebulae and Clusters of Stars, published in 1789.

Sir William made his discovery of the lenticular galaxy in Aquarius the Water Bearer constellation with his 18.7-inch aperture, 20-foot reflector telescope. Sir John used his father’s telescope for his four observations of NGC 7302.

Sir William’s only child, John Frederick William Herschel, 1 Baronet (March 7, 1792-May 11, 1871), made his first observation of NGC 7302 during Sweep 37 of deep-sky objects, conducted Aug. 5, 1826. His second and third observations happened on two successive dates in July 1830. Sweep 273 and Sweep 274 occurred, respectively, on July 26 and July 27. Sir John’s fourth observation took place Sept. 10, 1831, during Sweep 373.

Sir John compiled his four observations under entry number 2165 in his astronomical catalogue, Observations of Nebulae and Clusters of Stars, Made at Slough, which was published in 1833. His observations are arranged in order of right ascension, the celestial equivalent of terrestrial longitude. Accordingly, his observation from Sweep 273 (July 26, 1830), which occurred chronologically as the second of the four observations, appears first.

The Sweep 273 observation has equatorial coordinates of right ascension at 22 hours 23 minutes 15.6 seconds and declination at 104 degrees 59 minutes 37 seconds. He remarks: “F; pL; R; v s b M to a S, F, R nucleus; diam 2’; has a * s f in pos 352°.5 by micr; dist 3’.”

Sir John’s description transcribes as: “Faint; pretty large; round; very suddenly bright in the middle to a small, faint, round nucleus; diameter 2’; has a star south following, in angle of position measured 352.5 degrees by the micrometer; at a distance from it of 3”.”

The second entry under number 2165 comes from the next night’s survey, Sweep 274 (July 27, 1830). Right ascension calculates at 22 hours 23 minutes 15.7 seconds. Declination measures 104 degrees 60 minutes 23 seconds. Sir John’s concise description observes: “F; E; s b M; twilight commenced.”

His description translates as: “Faint; elongated; suddenly bright in the middle; twilight commenced.”

Sweep 37 (Aug. 5, 1826), which chronologically occurred as first of the four observations, supplies the next set of details. Right ascension is 22 hours 23 minutes 16.7 seconds, and declination is 104 degrees 59 minutes 51 seconds. Sir John’s description notes: “F; R; b M; 15’; by obs RA = 22^m 16^s.7, but this is an obvious mistake.”

His description transcribes as: “Faint; round; bright in the middle; right ascension by observation equals 22 minutes 16.7 seconds, but this is an obvious mistake.”

Details from Sweep 373, conducted Sept. 10, 1831, as the last of the four observations, close Sir John’s entries on NGC 7302. Right ascension is 22 hours 23 minutes 18.5 seconds. Declination is 104 degrees 58 minutes 57 seconds. Sir John’s briefly notes: “F; S; R; v s b m to a * 14 m.”

His description translates as: “Faint; small; round; very suddenly much brighter to star of the 14th magnitude.”

The takeaway for Sir John Herschel’s four observations of lenticular galaxy NGC 7302, discovered Oct. 3, 1785, in constellation Aquarius by his father, Uranus discoverer William Herschel, is that Sir John made his four observations with the same telescope used for his father’s discovery.

NGC 7302, lenticular galaxy in constellation Aquarius, discovered Oct. 3, 1785 by Uranus discoverer Sir William Herschel and observed four times between 1826 and 1831, by his son, Sir John Herschel; "Atlas Image courtesy of 2MASS/UMass/IPAC-Caltech/NASA/NSF": 2MASS (Two Micron All Sky Survey), Public Domain, via NASA/JPL-Caltech IPAC (Infrared Processing and Analysis Center)

Acknowledgment

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

Image credits:

Sir William Herschel’s 20-foot reflecting telescope, through which Sir William discovered NGC 7302 on Oct. 3, 1785, and used for his son’s four observations of NGC 7302: W. Herschel, W. Bunce and J. Walker’s William Herschel’s Twenty-Foot Reflecting Telescope (1794 print), CC BY 4.0 International, via University of Cambridge Institute of Astronomy Library @ https://www.repository.cam.ac.uk/handle/1810/217286

NGC 7302, lenticular galaxy in constellation Aquarius, discovered Oct. 3, 1785 by Uranus discoverer Sir William Herschel and observed four times between 1826 and 1831, by his son, Sir John Herschel; "Atlas Image [or Atlas Image mosaic] obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.": Public Domain, via NASA/JPL-Caltech IPAC (Infrared Processing and Analysis Center) @ https://irsa.ipac.caltech.edu/cgi-bin/2MASS/PubGalPS/nph-galps?objstr=2MASXJ22322379-1407137

For further information:

Bratton, Mark. The Complete Guide to the Herschel Objects: Sir William Herschel’s Star Clusters, Nebulae and Galaxies. Cambridge, UK; New York NY; Melbourne, Australia; Madrid, Spain; Cape Town, South Africa; Singapore; São Paulo, Brazil; Delhi, India; Tokyo, Japan; Mexico City, Mexico: Cambridge University Press, 2011.

Dreyer, J.L.E. (John Louis Emil). “No. 7302.” In: “A New General Catalogue of Nebulae and Clusters of Stars, Being the Catalogue of the Late Sir John F.W. Herschel, Bart., Revised, Corrected, and Enlarged.” Memoirs of the Royal Astronomical Society, vol. XLIX, part I: 198. London, England: Royal Astronomical Society, 1888.
Available @ https://ia800501.us.archive.org/14/items/newgeneralcatalo00dreyrich/newgeneralcatalo00dreyrich.pdf
Available via HathiTrust @ https://hdl.handle.net/2027/osu.32435078053089?urlappend=%3Bseq=204

Dreyer, J.L.E. (John Louis Emil). “A New General Catalogue of Nebulae and Clusters of Stars, Being the Catalogue of the Late Sir John F.W. Herschel, Bart., Revised, Corrected, and Enlarged.” Memoirs of the Royal Astronomical Society, vol. XLIX, part I. London, England: Royal Astronomical Society, 1888.
Available @ https://ia800501.us.archive.org/14/items/newgeneralcatalo00dreyrich/newgeneralcatalo00dreyrich.pdf
Available via HathiTrust @ https://hdl.handle.net/2027/osu.32435078053089

Dreyer, J.L.E. (John Louis Emil). “A Supplement to Sir John Herschel’s ‘General Catalogue of Nebulae and Clusters of Stars.’ (Read February 26, 1877.).” The Transactions of the Royal Irish Academy, vol. XXVI (March 1878). Dublin, Ireland: Royal Irish Academy, 1878.
Available via Internet Archive @ https://archive.org/details/supplementtosirj00dreyrich/

Herschel, Sir John Frederick William. “Catalogue of Nebulae and Clusters of Stars. Received October 16, -- Read November 19, 1863.” Philosophical Transactions of the Royal Society of London. For the Year MDCCCLXIV [1864]. Vol. 154: 1-137. London, England: Taylor and Francis, MDCCCLXV (1865).
Available via Biodiversity Heritage Library (Natural History Museum Library, London) @ https://biodiversitylibrary.org/page/54093164
Available via JSTOR @ https://www.jstor.org/stable/108864

Herschel, Sir John F.W. (Frederick William). “A General Catalogue of Nebulae and Clusters of Stars, Arranged in Order of Right Ascension and Reduced to the Common Epoch 1860.0 (With Precessions Computed for the Epoch 1880.0). Received October 16, -- Read November 19, 1863.” Philosophical Transactions, Part I (1864): 1-137. London, England: Taylor and Francis, 1864.
Available via HathiTrust @ https://catalog.hathitrust.org/Record/001475323

Herschel, Sir John Frederick William. “No. 2165.” In: “Observations of Nebulae and Clusters of Stars, Made at Slough, With a Twenty-Feet Reflector, Between the Years 1825 and 1833. Received July 1, -- Read November 21, 1833.” Philosophical Transactions of the Royal Society of London, vol. 123 (1833): 473.
Available via Internet Archive @ https://archive.org/details/philtrans06301558/page/n114
Available via JSTOR @ https://www.jstor.org/stable/108003?seq=115#metadata_info_tab_contents

Herschel, Sir John Frederick William. “No. of Catalogue: 4802.” In: “Catalogue of Nebulae and Clusters of Stars. Received October 16, -- Read November 19, 1863.” Philosophical Transactions of the Royal Society of London. For the Year MDCCCLXIV [1864]. Vol. 154: 132. London, England: Taylor and Francis, MDCCCLXV (1865).
Available via Biodiversity Heritage Library (Natural History Museum Library, London) @ https://biodiversitylibrary.org/page/54093295
Available via JSTOR @ https://www.jstor.org/stable/108864?seq=132#metadata_info_tab_contents

Herschel, Sir John Frederick William. “Observations of Nebulae and Clusters of Stars, Made at Slough, With a Twenty-Feet Reflector, Between the Years 1825 and 1833. Received July 1, -- Read November 21, 1833.” Philosophical Transactions of the Royal Society of London, vol. 123 (1833): 359-505.
Available via JSTOR @ https://www.jstor.org/stable/108003

Herschel, William. “IV. 31.” In: “Catalogue of a Second Thousand of New Nebulae and Clusters of Stars; With a Few Introductory Remarks on the Construction of the Heavens. Read June 11, 1789.” Philosophical Transactions of the Royal Society of London, vol. LXXIX, part II (1789): 246. London, England: Lockyer Davis and Peter Elmsly, Printers to The Royal Society, MDCCLXXXIX.
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51828776
Available via JSTOR @https://www.jstor.org/stable/106695

Herschel, William. “Catalogue of 500 New Nebulae, Nebulous Stars, Planetary Nebulae, and Clusters of Stars; With Remarks on the Construction of the Heavens. Read July 1, 1802.” Philosophical Transactions of the Royal Society of London. For the Year MDCCCII [1802] [vol. 92], part II: 477-528. London, England: W. Bulmer and Co., MDCCCII.
Available via Biodiversity Heritage Library (Smithsonian Libraries) @ https://biodiversitylibrary.org/page/49130796
Available via Biodiversity Heritage Library (University of Toronto -- Robarts Library) @ https://biodiversitylibrary.org/page/22894665
Available via JSTOR @ https://www.jstor.org/stable/107131

Herschel, William. “Catalogue of a Second Thousand of New Nebulae and Clusters of Stars; With a Few Introductory Remarks on the Construction of the Heavens. Read June 11, 1789.” Philosophical Transactions of the Royal Society of London, vol. LXXIX, part II (1789): 212-255. London, England: Lockyer Davis and Peter Elmsly, Printers to The Royal Society, MDCCLXXXIX.
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/51828742
Available via JSTOR @ https://www.jstor.org/stable/106695

Herschel, William. “Catalogue of One Thousand New Nebulae and Clusters of Stars. Read April 27, 1786.” Philosophical Transactions of the Royal Society of London, vol. LXXVI, part II (1786): 457-499. London, England: Lockyer Davis and Peter Elmsly, Printers to The Royal Society, MDCCLXXXVI.
Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/48283813
Available via JSTOR @ https://www.jstor.org/stable/106639

Mullaney, James. The Herschel Objects and How to Observe Them. AST Astronomers’ Observing Guides. New York NY: Springer Science+Business Media LLC, 2007.

Mullaney, James; Wil Tirion. The Cambridge Atlas of Herschel Objects. Cambridge, England; New York NY; Melbourne, Australia; Madrid, Spain; Cape Town, South Africa; Singapore; São Paulo, Brazil; Delhi, India; Dubai, United Arab Emirates; Tokyo, Japan; Mexico City: Mexico: Cambridge University Press, 2011.

O’Meara, Steve. Herschel 400 Observing Guide: How to Find and Explore 400 Star Clusters, Nebulae, and Galaxies Discovered by William and Caroline Herschel. Cambridge, England; New York NY; Melbourne, Australia; Madrid, Spain; Cape Town, South Africa; Singapore; São Paulo, Brazil: Cambridge University Press, 2007.

Chadwick Crater Honors British Physicist Sir James Chadwick

Summary: Chadwick Crater honors British physicist Sir James Chadwick, whose 1935 Nobel Prize in Physics recognized his discovery of the neutron in 1932.

Detail of Lunar Astronautical Chart (LAC) 28 shows Chadwick Crater as a far side crater, with nearest named neighbors De Roy Crater and Mendel Crater's satellite J to the southeast and northwest, respectively; courtesy NASA (National Aeronautics and Space Administration) / GSFC (Goddard Space Flight Center) / ASU (Arizona State University): U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature

Chadwick Crater honors British physicist Sir James Chadwick, who was awarded the Nobel Prize in Physics in 1935 for his 1932 discovery of the neutron.

Chadwick is a lunar impact crater in the lunar far side’s southeastern quadrant. The roughly circular crater exhibits a sharp-edged rim. Thickened south-southeastern inner walls account for an outward bulge in the crater’s outline. Chadwick’s interior floor appears uneven.

Chadwick is centered at minus 52.85 degrees south latitude, minus 101.34 degrees west longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The southern hemisphere crater obtains northernmost and southernmost latitudes at minus 52.36 degrees south and minus 53.34 degrees south, respectively. The high middle-latitude crater’s easternmost and westernmost longitudes occur at minus 100.54 degrees south and minus 102.15 degrees south, respectively. Chadwick’s diameter measures 29.74 kilometers.

De Roy Crater and Mendel J Crater occur as Chadwick’s nearest named neighbors. De Roy resides to the southeast of Chadwick. Mendel J lies to the northwest of Chadwick.

Slightly irregularly circular De Roy Crater occurs as the northernmost and easternmost member of the De Roy Crater system. Its location places it closer to Chadwick Crater than to its three satellites, which reside to the southwest of their parent.

De Roy Crater is centered at minus 55.24 degrees south latitude, minus 98.99 degrees west longitude. It marks northernmost and southernmost latitudes of minus 54.52 degrees south and minus 55.95 degrees south, respectively. De Roy finds easternmost and westernmost longitudes at minus 97.74 degrees west and minus 100.24 degrees west, respectively. De Roy Crater’s diameter measures 43.51 kilometers.

Mendel J numbers among the Mendel Crater system’s three satellites. Mendel J shares part of its parent’s southeastern rim.

Mendel J is centered at minus 51.51 degrees south latitude, minus 107.2 degrees west longitude. The satellite records northernmost and southernmost latitudes at minus 50.56 degrees south and minus 52.46 degrees south, respectively. It registers easternmost and westernmost longitudes at minus 105.68 degrees west and minus 108.73 degrees west, respectively. Mendel J’s diameter spans 57.59 kilometers.

Chadwick Crater honors British physicist Sir James Chadwick (Oct. 20, 1891-July 24, 1974). The International Astronomical Union (IAU) approved Chadwick as the crater’s official in 1985, during the organization’s XIXth (19th) General Assembly, held in New Delhi, India, from Monday, Nov. 18, to Saturday, Nov. 30.

Sir James was elected as a Fellow of The Royal Society (FRS) on Dec. 5, 1927, according to The Royal Society’s website. The Society’s election certificate noted, in particular, Chadwick’s investigations into the properties of alpha and beta particles and “on the magnitude of the charge on the nucleus and the law of force around it.” The certificate also cited Chadwick’s collaboration in pioneer research on alpha particle disintegration, since 1919, with nuclear physics pioneer Sir Ernest Rutherford, 1st Baron Rutherford of Nelson (Aug. 30, 1871-Oct. 19, 1937) at the University of Cambridge’s Cavendish Laboratory.

In 1932, Chadwick and his assistant, English physicist Norman Feather (Nov. 16, 1904-Aug. 14, 1978), who had been Chadwick and Rutherford’s doctoral student, discovered the neutron. Chadwick announced the discovery of the subatomic, non-electrically charged particle in a letter, dated Feb. 17, 1932, to Nature. The Swedish Academy of Sciences awarded the Nobel Prize in Physics in 1935 to Chadwick “for the discovery of the neutron.” The Nobel Laureate’s biography on the Nobel Prize website explains the significance of his discovery: “Chadwick in this way prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb.”

Chadwick was knighted for his achievements in physics in 1945.

The takeaways for Chadwick Crater, which honors British physicist Sir James Chadwick, are that the lunar impact crater occupies the far side’s southeastern quadrant; that the crater’s namesake is credited with the discovery of the neutron, a non-charged subatomic particle, in 1932; and that the Swedish Academy of Sciences awarded the Nobel Prize in Physics in 1935 to Chadwick for his significant discovery.

Detail of Shaded Relief and Color-Coded Topography Map shows Chadwick Crater as a high middle-latitude crater in the lunar far side’s southeastern quadrant: U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature

Acknowledgment

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

Image credits:

Detail of Lunar Astronautical Chart (LAC) 135 shows Chadwick Crater as a far side crater, with nearest named neighbors De Roy Crater and Mendel Crater's satellite J to the southeast and northwest, respectively; courtesy NASA (National Aeronautics and Space Administration) / GSFC (Goddard Space Flight Center) / ASU (Arizona State University): U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/Lunar/lac135_wac.pdf

Detail of Shaded Relief and Color-Coded Topography Map shows Chadwick Crater as a high middle-latitude crater in the lunar far side’s southeastern quadrant: U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/moon_nearside.pdf

For further information:

Andersson, Leif E.; and Ewen A. Whitaker. NASA Catalogue of Lunar Nomenclature. NASA Reference Publication 1097. Washington DC: NASA National Aeronautics and Space Administration Scientific and Technical Information Branch, October 1982.
Available via NASA NTRS (NASA Technical Reports Server) @ https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19830003761.pdf

Barnes, Melene. “Richard C. Carrington.” Journal of the British Astronomical Association, vol. 83, no. 2 (1973): 122-124.
Available via Harvard ADSABS @ http://adsabs.harvard.edu/full/1973JBAA...83..122B
Available via Harvard ADSABS @ http://adsabs.harvard.edu/pdf/1973JBAA...83..122B

Chadwick, James. “Existence of a Neutron.” Proceedings of the Royal Society A, vol. 136, issue 830 (June 1, 1932): 692-708.
Available via JSTOR @ https://www.jstor.org/stable/95816
Available @ https://royalsocietypublishing.org/doi/abs/10.1098/rspa.1932.0112

Chadwick, James. “Possible Existence of a Neutron.” Nature, vol. 129, no. 3252 (Feb. 27, 1932): 312.
Available via MIT @ http://web.mit.edu/22.54/resources/Chadwick.pdf
Available @ https://www.nature.com/articles/129312a0

Consolmagno, Guy; and Dan M. Davis. Turn Left at Orion. Fourth edition. Cambridge UK; New York NY: Cambridge University Press, 2011.

Grego, Peter. The Moon and How to Observe It. Astronomers’ Observing Guides. London UK: Springer-Verlag, 2005.

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Chadwick.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > The Moon. Last updated Oct. 18, 2010.
Available @ https://planetarynames.wr.usgs.gov/Feature/1118

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “De Roy.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > The Moon. Last updated Oct. 18, 2010.
Available @ https://planetarynames.wr.usgs.gov/Feature/1444

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Mendel J.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > The Moon. Last updated Oct. 18, 2010.
Available @ https://planetarynames.wr.usgs.gov/Feature/11324

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

Marriner, Derdriu. “Bragg Crater Honors British Physicist Sir William Henry Bragg.” Earth and Space News. Wednesday, March 14, 2012.
Available @ https://earth-and-space-news.blogspot.com/2012/03/bragg-crater-honors-british-physicist.html

Marriner, Derdriu. “Pogson Crater Honors British Astronomer Norman Robert Pogson.” Earth and Space News. Wednesday, June 20, 2012.
Available @ https://earth-and-space-news.blogspot.com/2012/06/pogson-crater-honors-british-astronomer.html

Massey, Harrie; and N. Feather. “James Chadwick 20 October 1891-24 July 1974 Elected F.R.S. 1927.” Biographical Memoirs of Fellows of the Royal Society, vol. 22 (November 1976): 10-70.
Available via JSTOR @ https://www.jstor.org/stable/769732

The Moon Wiki. “Chadwick.” The Moon > Lunar Features Alphabetically > C Nomenclature.
Available @ https://the-moon.us/wiki/Chadwick

The Moon Wiki. “De Roy.” The Moon > Lunar Features Alphabetically > D Nomenclature.
Available @ https://the-moon.us/wiki/De_Roy

The Moon Wiki. “IAU Directions.” The Moon.
Available @ https://the-moon.us/wiki/IAU_directions

The Moon Wiki. “Mendel.” The Moon > Lunar Features Alphabetically > M Nomenclature.
Available @ https://the-moon.us/wiki/Mendel

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

The Nobel Prize. “James Chadwick: Biographical.” The Nobel Prize > Prizes > Physics > 1935.
Available @ https://www.nobelprize.org/prizes/physics/1935/chadwick/biographical/

The Royal Society. “Chadwick; James (c 1660-1697).” The Royal Society > Collections > Fellows.
Available @ https://collections.royalsociety.org/DServe.exe?dsqIni=Dserve.ini&dsqApp=Archive&dsqCmd=Show.tcl&dsqDb=Persons&dsqPos=3&dsqSearch=%28%28text%29%3D%27Chadwick%27%29

Swings, J.P. (Jean-Pierre), ed. XIXth General Assembly Transactions of the IAU Vol. XIX B Proceedings of the 19th General Assembly New Delhi, India, November 18-30, 1985. Washington DC: Association of Universities for Research in Astronomy, Jan. 1, 1986.
Available via IAU @ https://www.iau.org/publications/iau/transactions_b/

Cassini Wide Angle Camera Imaged South Pole During First Titan Flyby

Summary: The Cassini wide angle camera imaged the south pole during the first Titan flyby on Friday, July 2, 2004.

Natural color image composites Cassini wide angle camera’s blue, green and red filtered images obtained July 2, 2004, from an approximate distance of 347,000 kilometers (216,000 miles); yellow curve on image with superimposed coordinate system grid (right) indicates day/night terminator; image scale equals 21 kilometers (13 miles) per pixel; phase angle of 62 degrees; NASA ID PIA06087; image addition date 2004-07-27; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal

The Cassini wide Angle Camera imaged the south pole during the first Titan flyby on Friday, July 2, 2004, as the Cassini-Huygens spacecraft took the mission’s first images of Saturn’s largest moon.

The Cassini Wide angle camera (WAC) is one of two framing cameras composing the Cassini Imaging Science Subsystem (ISS). The two-dimensional imaging device pairs the wide angle camera with a narrow angle camera (NAC). The Cassini Imaging Science Subsystem is mounted on the Cassini-Huygens spacecraft’s Cassini orbiter. The sophisticated camera system numbers among 12 science instruments carried on the Cassini orbiter.

The mission’s wide angle camera is a 0.2-meter (200-millimeter) focal length refractor telescope with a field of view (FOV) of 3.5 degrees. Both the wide angle camera and the narrow angle camera are outfitted with an array of spectral filters that combine to yield an electromagnetic spectrum span of 200 to 1100 nanometres (nm), according to Cassini imaging administrator Carolyn Porco and 19 co-authors in the November 2004 issue of Space Science Reviews. (A nanometer is a unit of length in the metric system equating to one billionth of a metre.)

On July 2, 2004, the Cassini-Huygens spacecraft made its first flyby of Titan. The NASA Jet Propulsion Laboratory’s (JPL) Photojournal website’s gallery of images from the first Titan flyby includes two natural color images, NASA identification numbers PIA06087 and PIA 06089.

A natural color image captured by Cassini’s wide angle camera on July 2, 2004, reveals the view of the largest Saturnian moon only about two hours after the spacecraft’s closest approach to Titan. The natural color image (NASA ID PIA06087) represents a composite of images taken through the wide angle camera’s blue, green and red filters. The color-filtered images were obtained at an approximate distance of 347,000 kilometers (216,000 miles) from Titan.

The phase angle from the sun to the target, Titan, to the observer, the Cassini-Huygens spacecraft, measured 62 degrees. In her Planetary Society blog posting Oct. 27, 2009, planetary geologist Emily Lakdawalla notes that, per planetary scientist Anne Verbiscer’s communication, Titan displays no variability in brightness at phase angles under 90 degrees, that is, below the half moon phase.

Titan appears as a gibbous moon, more than half-illuminated, in the July 2 natural color image. Illumination encompasses an expanse of Titan southward from the equator to the south pole and eastward from approximately 330 degrees west longitude. The day/night terminator is clearly visible as the line marking the boundary between Titan’s illuminated and unilluminated regions.

A second natural color image displayed on the NASA JPL Photojournal website represents the view of Titan on July 3, 2004, approximately one day after the first Titan flyby’s closest approach. The natural color image (NASA ID PIA06089) composites images obtained through the wide angle camera’s blue, green and red filters. The July 3 color-filtered images were taken at an approximate distance of 790,000 kilometers (491,000 miles) from Titan. The images were acquired at a sun-Titan-spacecraft, or phase, angle of 115 degrees. The phase angle of the July 3 color-filtered images measured 115 degrees.

The July 3 natural color image presents Titan as a crescent moon. Titan’s illuminated portion stretches along the eastern limb from the south pole northward to the lower crescent’s point, or horn, at approximately minus 30 degrees south latitude and the upper horn, in northern equatorial latitudes. The Titanean terminator demarcates the image’s vast unilluminated region, which encompasses approximately 180 to 300-plus degrees west longitude and minus 60 degrees south latitude to 30-plus degrees north latitude.

The takeaways for the Cassini wide angle camera’s south pole images during the first Titan flyby in July 2004 are that two natural color images displayed on the NASA Jet Propulsion Laboratory’s (JPL) Photojournal website show the Titanean south pole in the moon’s crescent and gibbous phases; that the July 2 image composites blue, green and red filter images obtained from an approximate distance of 347,000 kilometers (216,000 miles); and that the July 3 image’s view was acquired from an approximate distance of 790,000 kilometers (491,000 miles).

Natural color image composites Cassini wide angle camera’s blue, green and red filtered images obtained July 3, 2004, from an approximate distance of 790,000 kilometers (491,000 miles); yellow curve on image with superimposed coordinate system grid (right) indicates day/night terminator; image scale equals 47 kilometers (29 miles) per pixel; phase angle of 115 degrees; PIA06089; image addition date 2004-07-28; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal

Acknowledgment

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

Image credits:

Natural color image composites Cassini wide angle camera’s blue, green and red filtered images obtained July 2, 2004, from an approximate distance of 347,000 kilometers (216,000 miles); yellow curve on image with superimposed coordinate system grid (right) indicates day/night terminator; image scale equals 21 kilometers (13 miles) per pixel; phase angle of 62 degrees; NASA ID PIA06087, image addition date 2004-07-27; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA06087

Natural color image composites Cassini wide angle camera’s blue, green and red filtered images obtained July 3, 2004, from an approximate distance of 790,000 kilometers (491,000 miles); yellow curve on image with superimposed coordinate system grid (right) indicates day/night terminator; image scale equals 47 kilometers (29 miles) per pixel; phase angle of 115 degrees; PIA06089, image addition date 2004-07-28; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA06089

For further information:

Lakdawalla, Emily. “What ‘Phase Angle’ Means.” The Planetary Society > Blogs. Oct. 27, 2009.
Available @ https://www.planetary.org/blogs/emily-lakdawalla/2009/2179.html

Lavoie, Sue, site mgr. “PIA06081: Titan in Natural Color.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-02.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06081

Lavoie, Sue, site mgr. “PIA06089: Hazy All Over.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-28.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06089

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

Marriner, Derdriu. “Cassini Narrow Angle Camera Imaged South Pole During First Titan Flyby.” Earth and Space News. Wednesday, July 4, 2012.
Available @ https://earth-and-space-news.blogspot.com/2012/07/cassini-narrow-angle-camera-imaged.html

Marriner, Derdriu. “Christiaan Huygens Discovered Saturnian Satellite Titan March 25, 1655.” Earth and Space News. Wednesday, March 21, 2012.
Available @ https://earth-and-space-news.blogspot.com/2014/03/christiaan-huygens-discovered-saturnian.html

Marriner, Derdriu. “Visible and Infrared Mapping Spectrometer VIMS Shows Titanean Surface.” Earth and Space News. Wednesday, March 28, 2012.
Available @ https://earth-and-space-news.blogspot.com/2012/03/visible-and-infrared-mapping.html

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

Porco, Carolyn C.; Robert A. West; Steven Squyres; Alfred McEwen; Peter Thomas; Carl D. Murray; Anthony Delgenio; Andrew P. Ingersoll; Torrence V. Johnson; Gerhard Neukum; Joseph Veverka; Luke Dones; Andre Brahic; Joseph A. Burns; Vance Haemmerle; Benjamin Knowles; Douglas Dawson; Thomas Roatsch; Kevin Beurle; and William Owen. “Cassini Imaging Science: instrument Characteristics and Anticipated Scientific Investigations at Saturn.” Space Science Reviews, vol. 115 (November 2004), issue 1-4: 363-497.
Available via NASA GISS (Goddard Institute for Space Studies) @ https://pubs.giss.nasa.gov/docs/2004/2004_Porco_po04100j.pdf

Cassini Narrow Angle Camera Imaged South Pole During First Titan Flyby

Summary: The Cassini narrow angle camera imaged the south pole during the first Titan flyby on July 2, 2004.

A sequence of four images, obtained by the Cassini-Huygens spacecraft’s narrow angle camera (NAC) over approximately five hours during the mission’s first Titan flyby, July 2, 2004, tracks an evolving field of clouds near Titan’s south polar region; NASA ID PIA06110, image addition date 2004-07-03; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal

The Cassini narrow angle camera imaged the south pole during the first Titan flyby on July 2, 2004, as the Cassini-Huygens spacecraft obtained the mission’s first images of Saturn’s largest moon.

The Cassini-Huygens spacecraft launched Wednesday, Oct. 15, 1997, at 08:43 Coordinated Universal Time (UTC; 1:43 a.m. Pacific Daylight Time PDT; 4:43 a.m. Eastern Daylight Time EDT) from east central Florida’s Cape Canaveral. On Monday, June 28, at 8:54 p.m. PDT (11:54 p.m. EDT; Tuesday, June 29, at 03:54 UTC), the spacecraft entered into Saturn’s orbit by executing the Saturn Orbit Insertion (SOI) maneuver, according to a June 28, 2004, post by science writers Lonnie Shekhtman and Jay Thompson on the National Aeronautics and Space Administration (NASA) Science Solar System Exploration website.

The spacecraft achieved its first flyby of Titan, Saturn’s largest moon, on Friday, July 2, 2004. The NASA Jet Propulsion Laboratory’s (JPL) Photojournal website displays images from this first, albeit distant, encounter with Titan. The images were obtained, over the course of almost five hours, by the Cassini Imaging Science System’s (ISS) narrow angle camera (NAC).

The narrow angle camera is one of two fixed focal length cameras that comprise the Cassini-Huygens spacecraft’s Imaging Science Subsystem. The narrow angle camera is a high resolution reflecting telescope with a square field of view (FOV) of 0.35 degrees and a 2000-millimeter (mm) focal length. The wide angle camera (WAC) is a low resolution refractor with a field of view of 3.5 degrees and a 200-mm focal length. Each camera is equipped with spectral filters that have a combined electromagnetic spectrum span of 200 to 1100 nanometres (nm), according to Cassini imaging director Carolyn Porco and 19 co-authors in the November 2004 issue of Space Science Reviews.

The Imaging Science System is attached to the cylindrically-shaped main body of the Cassini orbiter. The Cassini orbiter and the Huygens probe are the spacecraft’s two main elements.

A sequence of four images of Titan’s atmosphere and surface (NASA ID: PIA06110) were obtained at distance ranges of 364,000 to 339,000 kilometers (226,170 to 210,600 miles) from the haze-blanketed moon. The images have a pixel scale of 2.2 to 2.0 kilometers per pixel (1.4 to 1.2 miles per pixel). The smallest discernible surface features in the images measure approximately 10 kilometers (6 miles).

The quartet records a field of clouds near the Titanean south pole. The bright clouds are believed to be methane-based, not water-based.

A blowup of one of the images of the south polar clouds (NASA ID: PIA06112) reveals variations in brightness on the Titanean surface. The field of the clouds covers 450 kilometers (280 miles), which approximates the size of the U.S. state of Arizona, according to the NASA JPL Photojournal website. This image was acquired at a distance of 339,000 kilometers (210,600 miles).

A mosaic, published July 3, 2004, as “Titan’s Mottled Surface” (NASA ID: PIA06109), is composed of south polar region images that were obtained via special filters that penetrate Titan’s thick haze and atmosphere. The mosaic’s surface features blur toward the limb as a result of the amount of atmosphere traversed by reflected light during passage from the Titanean surface to the camera.

The mosaic post considers the glimpse of the Titanean surface offered by this first flyby composite. “There are many strange dark and bright patterns on Titan’s surface -- linear, sinuous and circular -- whose origins are not yet understood,” the PIA06109 post observes.

The Cassini Huygens mission’s imaging team processes the mission’s images for release to the public at CICLOPS (Cassini Imaging Central Laboratory for Operations). CICLOPS is housed in the Space Science Institute (SSI) in Boulder, north central Colorado.

The takeaways for the Cassini narrow angle camera’s south pole images during the Cassini-Huygens mission’s first the Titan flyby are that the mission’s first, albeit distant, encounter with Saturn’s largest moon captured images from a distant range of 364,000 to 339,000 kilometers (226,170 to 210,600 miles) and that bright clouds and surface features were included in the camera’s field of view (FOV).

A mosaic of special filter images, obtained July 2, 2004, by the Cassini-Huygens spacecraft’s narrow angle camera from a distance of 339,000 kilometers (210,600 miles) reveals bright clouds and surface features at Saturnian moon Titan’s south polar region; NASA ID PIA06109, image addition date 2004-07-03; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal

Acknowledgment

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

Image credits:

A sequence of four images, obtained by the Cassini-Huygens spacecraft’s narrow angle camera (NAC) over approximately five hours during the mission’s first Titan flyby, July 2, 2004, tracks an evolving field of clouds near Titan’s south polar region; NASA ID PIA06110, image addition date 2004-07-03; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA06110

A mosaic of special filter images, obtained July 2, 2004, by the Cassini-Huygens spacecraft’s narrow angle camera from a distance of 339,000 kilometers (210,600 miles) reveals bright clouds and surface features at Saturnian moon Titan’s south polar region; NASA ID PIA06109, image addition date 2004-07-03; image credit NASA / JPL / Space Science Institute: May be used for any purpose without prior permission, via NASA JPL Photojournal @ https://photojournal.jpl.nasa.gov/catalog/PIA06109

For further information:

European Space Agency. “Approach and Arrival at Saturn.” European Space Agency Science & Technology > Missions > Operations / Post-Operations > Cassini-Huygens.
Available @ https://sci.esa.int/web/cassini-huygens/-/34955-approach-and-arrival

Finn, Heidi. “Porco Joins Space Science Institute.” Space Science Institute > Press Room. Nov. 13, 2003.
Available @ https://www.spacescience.org/pressroom/releases/20031113.pdf

Huber, Lyle, cur. “Cassini ISS: Imaging Science Subsystem.” NASA Planetary Data System (PDS) Planetary Atmospheres Node > Cassini.
Available @ https://atmos.nmsu.edu/data_and_services/atmospheres_data/Cassini/inst-iss.html

International Astronomical Union (IAU) / U.S. Geological Survey (USGS) Gazetteer of Planetary Nomenclature. “Target: Titan.” USGS Astrogeology Science Center > Gazetteer of Planetary Nomenclature > Nomenclature > Saturn.
Available @ https://planetarynames.wr.usgs.gov/Page/TITAN/target

Lavoie, Sue, site mgr. “PIA06109: Titan’s Mottled Surface.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-03.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06109

Lavoie, Sue, site mgr. “PIA06110: Titan’s South Polar Clouds.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-03.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06110

Lavoie, Sue, site mgr. “PIA06111: Titan’s South Polar Clouds.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-03.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06111

Lavoie, Sue, site mgr. “PIA06112: Titan Close-Up.” NASA Jet Propulsion Laboratory Photojournal > Catalog > Saturn. Image addition date 2004-07-03.
Available @ https://photojournal.jpl.nasa.gov/catalog/PIA06112

Lawrence, Eleanor. “Cloudy But Changeable on Titan.” Nature > News. Oct. 15, 1998.
Available @ https://www.nature.com/news/1998/981015/full/news981015-1.html

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

Marriner, Derdriu. “Christiaan Huygens Discovered Saturnian Satellite Titan March 25, 1655.” Earth and Space News. Wednesday, March 21, 2012.
Available @ https://earth-and-space-news.blogspot.com/2014/03/christiaan-huygens-discovered-saturnian.html

Marriner, Derdriu. “Visible and Infrared Mapping Spectrometer VIMS Shows Titanean Surface.” Earth and Space News. Wednesday, March 28, 2012.
Available @ https://earth-and-space-news.blogspot.com/2012/03/visible-and-infrared-mapping.html

Martinez, Carolina. “First Close Encounter of Saturn’s Hazy Moon Titan.” NASA > Missions > Current Missions > Cassini-Huygens Mission to Saturn > Multimedia. Oct. 25, 2004.
Available @ https://www.nasa.gov/mission_pages/cassini/media/cassini-102504.html

McEwen, A. (Alfred); E. (Elizabeth) Turtle; J. Perry; S. (Stephanie) Fussner; C. (Carolyn) Porco; R. (Robert) West; T. (Torrence) Johnson; G. Collins; T. Del Genio; J. Barbara; and the Cassini ISS Team. “Cassini Imaging Results at Titan.” Lunar and Planetary Science XXXVI: Papers Presented at the Thirty-Sixth Lunar and Planetary Science Conference March 14-18, 2005.
Available via NASA NTRS (NASA Technical Reporters Server) @ https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050174640.pdf

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

Nelson, Jon, site mgr. “Titan’s Mottled Surface.” NASA JPL > Space Images. July 3, 2004.
Available @ https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA06109

Nelson, Jon, site mgr. “Titan’s South Polar Clouds.” NASA JPL > Space Images. July 3, 2004.
Available @ https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA06110

Porco, Carolyn C.; Robert A. West; Steven Squyres; Alfred McEwen; Peter Thomas; Carl D. Murray; Anthony Delgenio; Andrew P. Ingersoll; Torrence V. Johnson; Gerhard Neukum; Joseph Veverka; Luke Dones; Andre Brahic; Joseph A. Burns; Vance Haemmerle; Benjamin Knowles; Douglas Dawson; Thomas Roatsch; Kevin Beurle; and William Owen. “Cassini Imaging Science: instrument Characteristics and Anticipated Scientific Investigations at Saturn.” Space Science Reviews, vol. 115 (November 2004), issue 1-4: 363-497.
Available via NASA GISS (Goddard Institute for Space Studies) @ https://pubs.giss.nasa.gov/docs/2004/2004_Porco_po04100j.pdf

Russell, Christopher T. The Cassini-Huygens Mission: Orbiter Remote Sensing Investigations, vol. 3. Reprinted from Space Science Reviews, vol. 115, nos. 1-4 (2004). Dordrecht; Boston MA; London UK: Kluwer Academic Publishers, 2004.
Available via Google Books @ https://books.google.com/books?id=-atCAAAAQBAJ

Shekhtman, Lonnie; and Jay Thompson. “Saturn Arrival -- A Guide to Saturn Orbit Insertion.” NASA Science Solar System Exploration > News. June 28, 2004.
Available @ https://solarsystem.nasa.gov/resources/11794/saturn-arrival-a-guide-to-saturn-orbit-insertion/

Shekhtman, Lonnie; and Jay Thompson. “Titan Flyby A (T-A): Oct. 26, 2004.” NASA Science Solar System Exploration > News. Oct. 25, 2004.
Available @ https://solarsystem.nasa.gov/news/12953/titan-flyby-a-t-a-oct-26-2004/

Shekhtman, Lonnie; and Jay Thompson. “Titan’s First Close-Up.” NASA Science Solar System Exploration > News. Dec. 17, 2004.
Available @ https://solarsystem.nasa.gov/resources/12149/titans-first-close-up/