Cosmic Reflections

Limb Darkening and Luminosity

The Sun photographed on 8 May 2019 in white light by Matúš Motlo
showing sunspots, faculae, and limb darkening

The photosphere of our Sun and most other stars exhibit a phenomenon called limb darkening where the disk is brighter at the center than at the edges at optical wavelengths. This effect is more pronounced towards the violet end of the visible spectrum than it is towards the red end.

Limb darkening occurs because there is a strong temperature gradient within the photosphere (deeper is hotter) and we see deeper into the Sun at the center of the disk then we do toward the edges. The deeper, hotter regions of the photosphere produce more visible light than do the shallower, cooler regions.

Does this non-uniformity of light emitted from the disk of a star mean we are “missing” some light in measuring a star’s brightness that would then affect our ability to accurately calculate the star’s total luminosity? Not at all. Here’s why.

Stars are almost always isotropic emitters of light. That means they emit light uniformly in all directions. At a given distance from the star, an observer would measure the same brightness of the star no matter what their direction from it. Even though the edges of the stellar disk are darker, the center is brighter, and the total integrated brightness is the same as it would be if all parts of the disk were emitting uniformly.

We calculate the luminosity of the star by measuring the amount of light we receive across our collecting area (whether that be the human eye or the telescope aperture), and then dividing this collecting area into the total surface area of a sphere centered on the star and having a radius that is our distance from the star. We then take that quotient times the amount of light we detect in our small collecting area to get the total amount of light emitted by the star in all directions.

Classical Music Timeline: 1880s

This is one of a series of postings of important classical music dates, from the 17th century to the present. Included are the date and location of the birth and death of composers, and the premiere date and location of the first public performance of works. When the premiere date and location is unknown, the date or year of completion of the work is given. Though reasonably comprehensive, this is a subjective list, so the choice of composers and works is mine. If you find any errors, or if you can offer a premiere date and location for a work where only the completion date or year is listed, please post a comment here.

1880
Edvard Grieg (1843-1907) completed Two Elegiac Melodies, op. 34

January 20 – Two Rhapsodies, op. 79 by Johannes Brahms (1833-1897) was first performed in Krefeld, Germany

April 20 – In the Steppes of Central Asia, in A minor, by Alexander Borodin (1833-1887) was first performed in Saint Petersburg, Russia

July 24 – Ernest Bloch (1880-1959) was born in Geneva, Switzerland

December 26 – Tragic Overture, in D minor, op. 81 by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

1881
Edvard Grieg (1843-1907) completed Norwegian Dances, op. 35

February 12 – Symphony No. 2 in C minor, op. 17, “Little Russian” (2nd and final version) by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Saint Petersburg, Russia

February 20 – Symphony No. 4 in E♭ major, WAB 104, “Romantic” by Anton Bruckner (1824-1896) was first performed in Vienna, Austria

March 25 – Béla Bartók (1881-1945) was born in Sânnicolau Mare, Romania

March 28 – Modest Mussorgsky (1839-1881) died in Saint Petersburg, Russia

August 19 – George Enescu (1881-1955) was born in Liveni, Romania

October 30 – Romance in G major for violin and orchestra, op. 26 by Johan Svendsen (1840-1911) was first performed in Oslo, Norway

November 9 – Piano Concerto No. 2 in B♭ major, op. 83 by Johannes Brahms (1833-1897) was first performed in Budapest, Hungary

December 4 – Violin Concerto in D major, op. 35 by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Vienna, Austria

1882
February 10 – The Snow Maiden, opera by Nikolai Rimsky-Korsakov (1844-1908) was first performed in Saint Petersburg, Russia

June 17 – Igor Stravinsky (1882-1971) was born in Lomonosov, Russia

July 8 – Percy Grainger (1882-1961) was born in Melbourne, Australia

July 26 – Parsifal, opera by Richard Wagner (1813-1883) was first performed in Bayreuth, Germany

October 6 – Karol Szymanowski (1882-1937) was born in Tymoshivka, Ukraine

November 5 – Má vlast, six symphonic poems by Bedřich Smetana (1824-1884) was first performed in its entirety in Prague, Czech Republic

November 27 – Serenade for 13 Wind Instruments in E♭ major, op. 7 by Richard Strauss (1864-1949) was first performed in Dresden, Germany

December 9 – Joaquín Turina (1882-1949) was born in Seville, Spain

December 16 – Zoltán Kodály (1882-1967) was born in Kecskemét, Hungary

1883
February 13 – Richard Wagner (1813-1883) died in Venice, Italy

March 19 – Tamara, symphonic poem in B minor by Mily Balakirev (1837-1910) was first performed in Saint Petersburg, Russia

May 16 – Scherzo capriccioso in D♭ major, op. 66 by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

July 4 – Maximilian Steinberg (1883-1946) was born in Vilnius, Lithuania

July 25 – Alfredo Casella (1883-1947) was born in Turin, Italy

July 27 – Franz Doppler (1821-1883) died in Baden bei Wien, Austria

October 14 – Violin Concerto in A minor, op. 53 by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

December – Elégie, for cello and piano, op. 24 by Gabriel Fauré (1845-1924) was first performed in Paris, France

December 2 – Symphony No. 3 in F major, op. 90 by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

December 3 – Anton Webern (1883-1945) was born in Vienna, Austria

December 6 – Sonata in F major for cello and piano, op. 6 by Richard Strauss (1864-1949) was first performed in Nuremberg, Germany

1884
Edvard Grieg (1843-1907) completed From Holberg’s Time: Suite in Olden Style, op. 40

April 23 – Silent Woods, for cello and orchestra (or piano), op. 68, no. 5, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

May 12 – Bedřich Smetana (1824-1884) died in Prague, Czech Republic

September 17 – Charles Griffes (1884-1920) was born in Elmira, New York

December 30 – Symphony No. 7 in E major, WAB 107, by Anton Bruckner (1824-1896) was first performed in Leipzig, Germany

1885
Emmanuel Chabrier (1841-1894) completed Habanera

April 22 – Symphony No. 7 in D minor, op. 70 by Antonín Dvořák (1841-1904) was first performed in London, England

June 19 – Stevan Hristić (1885-1958) was born in Belgrade, Serbia

July 7 – Ernest Farrar (1885-1918) was born in London, England

September 28 – Ballad in D minor, op. 15, for violin and piano, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

October 25 – Symphony No. 4 in E minor, op. 98 by Johannes Brahms (1833-1897) was first performed in Meiningen, Germany

November 23 – Stenka Razin, in B minor, op. 13, symphonic poem by Alexander Glazunov (1865-1936) was first performed in Saint Petersburg, Russia

1886
Edvard Grieg (1843-1907) completed Lyric Pieces, op. 43

January 10 – Aita Donostia (1886-1956) was born in San Sebastián, Spain

May 1 – Romeo and Juliet, Fantasy Overture (3rd and final version), TH 42, by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Tbilisi, Georgia

May 19 – Symphony No. 3 in C minor, op. 78, with organ, by Camille Saint-Saëns (1835-1921) was first performed in London, England

July 31 – Franz Liszt (1811-1886) died in Bayreuth, Germany

October 15 – Night on Bald Mountain by Modest Mussorgsky (1839-1881) and orchestrated by Nicolai Rimsky-Korsakov (1844-1908), was first performed in Saint Petersburg, Russia

November 24 – Cello Sonata No. 2 in F major, op. 99 by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

December 16 – Violin Sonata in A major, CFF 123, by César Franck (1822-1890) was first performed in Brussels, Belgium

1887
Gabriel Fauré (1845-1924) completed Pavane in F♯ minor, op. 50, for SATB choir and piano

Alexander Glazunov (1865-1936) completed Elegy in D♭ major, op. 17 (In memory of Franz Liszt) for cello and piano

January – Miniatures for Two Violins and Viola, op. 75a by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

January 22 – Piano Quartet No. 2 in G minor, op. 45 by Gabriel Fauré (1845-1924) was first performed in Paris, France

February 27 – Alexander Borodin (1833-1887) died in Saint Petersburg, Russia

March 5 – Heitor Villa-Lobos (1887-1959) was born in Rio de Janeiro, Brazil

March 7 – Heino Eller (1887-1970) was born in Tartu, Estonia

March 30 – Four Romantic Pieces, op. 75, for violin and piano, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

October 18 – Concerto for Violin, Cello, and Orchestra in A minor, op. 102 “Double Concerto” by Johannes Brahms (1833-1897) was first performed in Cologne, Germany

October 31 – Capriccio espagnol, op. 34 by Nikolai Rimsky-Korsakov (1844-1908) was first performed in Saint Petersburg, Russia

November 15 – Edvard Grieg (1843-1907) completed Violin Sonata No. 3 in C minor, op. 45

December 12 – Kurt Atterberg (1887-1974) was born in Gothenburg, Sweden

1888
Johannes Brahms (1833-1897) completed Nächtens (At night), in D minor, from Six Quartets, op. 112, no. 2

Nikolai Rimsky-Korsakov (1844-1908) completed Scheherazade, in E major, op. 35

Florida Suite by Frederick Delius (1862-1934) was first performed in Leipzig, Germany

November 17 – Symphony No. 5 in E minor, op. 64 by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Saint Petersburg, Russia

December 15 – Russian Easter Festival Overture, op. 36 by Nikolai Rimsky-Korsakov (1844-1908) was first performed in Saint Petersburg, Russia

December 21 – Violin Sonata No. 3 in D minor, op. 108, by Johannes Brahms (1833-1897) was first performed in Budapest, Hungary

December 30 – Ilse Fromm-Michaels (1888-1986) was born in Hamburg, Germany

1889
Alexander Glazunov (1865-1936) completed the orchestration of the unfinished Symphony No. 3 in A minor by Alexander Borodin (1833-1887)

February 17 – Symphony in D minor, CFF 130, by César Franck (1822-1890) was first performed in Paris, France

February 17 – Geoffrey Toye (1889-1942) was born in Winchester, England

October – Ralph Greaves (1889-1966) was born in Lymington, Hampshire, England

November 11 – Don Juan, tone poem in E major, op. 20 by Richard Strauss (1864-1949) was first performed in Weimar, Germany

November 20 – Symphony No. 1 in D major by Gustav Mahler (1860-1911) was first performed in Budapest, Hungary

←1870s

1890s→

Dean Ketelsen (1953-2023): A Personal Remembrance

Dean Ketelsen at the Grand Canyon Star Party

A dear friend of mine passed away suddenly last week while mowing the lawn at his cottage in St. Charles, Illinois. Most of us are lucky to have maybe a dozen friends. Dean must have had hundreds. He was as generous and kind-hearted as anyone I have ever known. And incredibly knowledgeable about observational astronomy and optics.

I first met Dean while I was an undergraduate student at Iowa State University in the late 1970s. He was hired by Dr. Willet Beavers to make stellar radial velocity observations using the 24-inch telescope at ISU’s Erwin W. Fick Observatory. I was the primary data analyst reducing the data from the telescope, and all of us were amazed at how many stars Dean could observe in a night! I believe Dean was the most productive observer Fick Observatory ever had.

Dean and I were part of the ISU team that traveled to a farm near Riverton, Manitoba, Canada to observe the total solar eclipse on February 26, 1979.

**Iowa State University Solar Eclipse Expedition – February 26, 1979**
Front Row (left to right): Dan Peterson, Maria Meyers, Chuck Hoelzen, Ed Sexauer
Back Row (left to right): David Oesper, Jim Pierce, David Cook, Mike Andrews, Prof. Stan Williams, Prof. Willet Beavers, **Dean Ketelsen**, Joe Eitter

After graduation and working for Fick Observatory before the radial velocity grant money ran out (temporarily), I moved to Dell Rapids, South Dakota to work for the EROS Data Center near Sioux Falls. But, before I left, Dean gave me a Unitron refractor. One of many examples of his generosity.

Soon after I moved to South Dakota, Dean moved to Tucson, Arizona to become a telescope operator on the Mayall 4-meter telescope at Kitt Peak National Observatory. Then, as now, the 4-meter scope was heavily scheduled, but on Christmas and New Year’s he sometimes had the scope to himself for photography and visual observing. I asked him once, “What is the most impressive object you ever saw with the Kitt Peak 4-meter?” His reply: “The crescent moon!” I received some beautiful black & white large prints of galaxies and nebulae from Dean taken with one of the large Kitt Peak instruments. I framed and cherished these astrophotos.

Dean left the telescope operator position at Kitt Peak a few years later and began working at the University of Arizona Mirror Lab where he remained for the rest of his life. He was directly involved in fabricating several of the 8.4-meter mirrors—the largest monolithic telescope mirrors in the world—as well as smaller optics as well. Early in his career at the Mirror Lab, Dean was also working part-time on a Master’s degree in Optical Science at the University of Arizona, but he was never able to complete it before classes he took more than five years earlier no longer counted towards his degree. And I can see why. Dean led a rich and busy life, and his many friends and acquaintances were always his first priority.

Dean’s hospitality was legendary. My family regularly visited Tucson over the years, and Dean was always a most gracious host, transporting us to see all the good sights whenever we visited. A tour of the Mirror Lab was often included, so—thanks to Dean—I have been there many a time.

Dean’s generosity was also legendary. Besides the Unitron refractor and astrophotos, many years ago Dean “loaned” me a pair of Fujinon 16×70 binoculars, and after I moved to Tucson in 2022, he gave me a pair of Celestron 25 x 100 binoculars as a house-warming gift, no longer following any pretense that this would be a loan.

Over a several year period, Dean made a 24-inch mirror for the Ames Area Amateur Astronomers in Iowa, which they are still using today in a Dobsonian telescope built by club members. And, speaking of Dobsonians, Dean was a close acquaintance of John Dobson, and they often got together at star parties.

Dean Ketelsen with John Dobson at a star party

Here are some recent examples of Dean’s generosity. When Suzy and I came to Tucson to visit December 26-30, 2021, Dean and his dear friend Susan Yager picked us up at the Amtrak station and they both spent a lot of time with us as we were thinking about moving to Tucson. Ditto for our March 6-10, 2022 house-hunting trip. I was planning to take Amtrak back to Wisconsin with a stop in Alpine, TX to visit my daughter and her family while Suzy flew to Chicago to get back to work sooner, but Dean was driving from Tucson to St. Charles, Illinois so I rode with him. Though he didn’t have to, Dean went out of his way to drop me off in Dodgeville, Wisconsin and then went on to St. Charles.

Before that house-hunting trip, Dean had reached out to the relatives in charge of Derald Nye’s estate, knowing that I would be losing my backyard research observatory in Wisconsin and that it might be possible for me to purchase his home in Corona de Tucson, which would include an observatory. Unfortunately, that opportunity did not happen, but Dean subsequently put in a good word for me so that I could serve on the 16-inch Meade telescope committee which will add that telescope to the TAAA’s TIMPA observing site.

Before we moved to Tucson, Dean offered to transport my astronomical optics in his large van so that I didn’t need to entrust that delicate equipment to the movers. A week before moving, we drove from Dodgeville and he drove from St. Charles where we met up in Rockford at Lino’s for pizza (great restaurant!) and the transfer of optical equipment to his van afterwards. Needless to say, that equipment arrived safe and sound and in perfect condition at our new house just a few days after the movers when Dean made the trip back to Tucson.

After we moved to Tucson on May 1, 2022, besides restaurant get-togethers at Daily Mae’s and Bianchi’s, Dean & Susan joined John & Lana Gilkison at our house to observe the May 15, 2022 total lunar eclipse. Dean (and Susan) picked me up twice for dark-sky observing: once to watch the Tau Herculid meteor shower Memorial Day 2022 at his favorite observing spot along the road to the top of Kitt Peak, and once to observe from Empire Ranch SSE of Tucson. I was looking forward to many more observing sessions with Dean, but sadly that will not happen. I have lost my best observing buddy here.

No one person can relate all the accolades and experiences that Dean had, but I know of a few. Dean received the 2002 Las Cumbres Amateur Outreach Award from the Astronomical Society of the Pacific, and the asteroid 124075 Ketelsen (2001 GT₁) was named after him.

Dean Ketelsen receiving the 2002 Las Cumbres Amateur Outreach Award
from the Astronomical Society of the Pacific

Dean was primarily responsible for reincarnating the Grand Canyon Star Party in 1991. He was a primary organizer for many years, and I believe he had attended every year since, including this year. I had the good fortune to attend in 2006, and gave one of the “Twilight Talks”. The most wonderful aspect of this star party that makes it very special and decidedly different from other star parties I have attended is that thousands of enthusiastic visitors to Grand Canyon National Park from all around the world are regaled by a twilight talk each night followed by observing through nearly 50 telescopes, binoculars, and green-laser-pointed constellations and satellites. The enthusiasm of the amateur astronomers sharing their love of astronomy with folks who are in an unusually good mood because they’re on vacation in a beautiful place is a winning combination. Dean had a lot to do with that vibe!

Dean was also an excellent public speaker, and frequently gave public astronomy talks and talks about the exciting things happening at the Mirror Lab.

Joan Oesper, **Dean Ketelsen**, Melinda Ketelsen, and David Oesper at Yerkes Observatory in 2008

Dean was an incredible photographer, whether the subject was astronomical, terrestrial, or people. He and his wife Melinda, who passed away after a long battle with cancer in 2016, have a blog called The Ketelsens! that includes many of his photos and descriptions of many of their experiences through the last posting on May 31, 2020—during the COVID-19 pandemic. I sincerely hope this blog will be moved to a permanent location on the internet before his blogspot account runs out. It would be a terrible shame to lose this treasure!

The Ketelsens!

We’re glad to see you here! Come and share our daily lives with us, we welcome your company and your comments. We hope there is something here for everyone!

And, speaking of photography, Dean first suggested many years ago the idea of stereo photography of the aurora. To the best of my knowledge, this has seldom been done, though with cellular phones and digital cameras now it would be relatively easy to coordinate such a venture. Two observers separated by a hundred miles or more with identical cameras, lenses, and exposure times would need to take pictures of the aurora at exactly the same time and in exactly the same direction (centered on the same star or constellation). The results, I’m sure, would be spectacular!

I have found it difficult to capture all I want to say about Dean in this article, but I’d like to finish by sharing with you the recent email communications I had from Dean, right up to the day before he died. All but one of my emails to Dean are unimportant in the context of this article, so they are not included here.

June 4, 2023 email from Dean Ketelsen
Just got word from Elinor’s niece Cathy (Prescott) that Elinor died a couple weeks ago. Evidently fell and broke her arm in several places, contracted pneumonia and died a week later. So sad – about the last of that generation of friends. She and David Levine, Derald Nye, Mike Terenzoni and I were the only folks (and Vicki!) at Grand Canyon #1. No memorial is planned, but I’ve already asked thru Cathy for a vial of her ashes – maybe we can have our own at the Canyon next year!

July 26, 2023 email from Dean Ketelsen
Hi David-
How are you surviving the heat? I’ve been up in St Charles coming up on 4 weeks and it has been delightful! This week is the worst, supposed to be up over 90, I think for the first time, tomorrow and Friday before dropping to low 80s for the weekend. I love those sunny days in the 70s, though we have been getting some smoke from the Canadian fires, some days worse than others.

The closer it comes, the less I’m excited about the annular eclipse. Plus I’ve got a “Ketelsen reunion” on 8 October, and after driving to the Midwest, not sure I’m up for returning after less than a week! So may watch the partial phase from here. Still thinking about next April. My first wife Vicki’s sister and her family live in Dallas and am welcome there. I’ve sent them a map of the path and they are looking for a location closer to the center line for a small group. Will see what they come up with. Not sure I’m interested in trying to chase clear spots – again, will see what sort of a zoo it is!

Probably back in Tucson about the weekend of the 12th. Hopefully temp will have dropped a little towards normal!

Hang in there!

-Dean

August 5, 2023 email from Dean Ketelsen
Hi David-
This article caught my eye in NYT online site. The hospital mixup was only a few miles from Riverton where we observed the ’79 solar eclipse…

https://www.nytimes.com/2023/08/02/world/canada/canada-men-switched-at-birth.html?unlocked_article_code=yfK-_7q6H6afzU_wYRyJuwzwmtKeLienRf4XbckD3zM34dZdJbUpBz9qUPQDAlwgssUlDamr6GRBP77fEwi6BQUoTsCbnU_viGK326XCYiE1qUM7Tt3Kbn2PGakUowq7a-XhOX2KNNzVulTfEMPZUGUVsxBvKP8B7_l7F97mMDmrAljA85HHWfaEPjsRdj6lVLIw4wuPASnGQk5vrlBtTbPPVfOfe7GVXH8Z1qM4ETdA82K49LhOtNmZmAATgCSgpD1i_NjpQixve3DlH7qpMMME7kw0qbhE9n7kIrT1C55hYfgOno8hW7k4wx9ySdTMlvX5xSL9RPz54ce-x5mncWCQsuuzzDLGv8VN&smid=url-share

Dean texted me about a Space X rocket launch from Vandenberg on August 7. I called him and we talked briefly on the phone. Little did I know it would be the last time I would hear his voice. Then, he sent me this email:

Good Luck!

From:launch-alert-bounces@mailman.qth.net <launch-alert-bounces@mailman.qth.net> on behalf of Launch Alert <launch-alert@mailman.qth.net>
Sent: Monday, August 7, 2023 1:02 PM
To:launch-alert@mailman.qth.net <launch-alert@mailman.qth.net>
Subject: [EXT][Launch Alert] Launch on Schedule

External Email

Tonight’s launch of a Falcon 9 rocket from Vandenberg SFB appears to be on schedule. The following is an update from SpaceX:

“SpaceX is targeting Monday, August 7 at 8:57 p.m. PT (03:57 UTC on August 8) for a Falcon 9 launch of 15 Starlink satellites to low-Earth orbit from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California.”

For launch and countdown status, go to…

August 7, 2023 email from David Oesper to Dean Ketelsen
Hi Dean,
Thanks for letting me know about this. We had partly cloudy skies tonight, which didn’t help, and I had to observe from my patio so if, as I suspect, the launch would only have been visible close to the WNW horizon, I wouldn’t have been able to see it. I thought I might be able to see one of the stage separations as it was heading to our southern sky here, but no luck with that either. Oh well, it was worth a try, anyway.

Thanks,

Dave

August 8, 2023 email from Dean Ketelsen
Hey David-
Watching the launch online, I could see the sunset from the onboard camera, but I don’t think it ever rose into bright sunset. Still, Ben Bailly of TAAA captured the enclosed last night. Still, not as spectacular as what it could be – the second taken be non-astronomer friend from Sabino Canyon area 10 months ago she noticed w/o advance warning…. Better luck next time!

-Dean

Dean died the following day. Here is his obituary:

https://www.malonefh.com/obituary/DeanA-Ketelsen

Dean’s obituary states that there will be a future gathering in Tucson to celebrate Dean’s life. As soon as that event is announced, I’ll post the information here in a comment.

Dean Ketelsen – Public Star Party at Sabino Canyon – April 29, 1989

I encourage you to share your personal remembrances of Dean by posting a comment here.

Classical Music Timeline: 1870s

1870
January 5 – Liebeslieder Waltzes, op. 52, by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

April 8 – Charles Auguste de Bériot (1802-1870) died in Brussels, Belgium

1871
Edvard Grieg (1843-1907) completed The Bridal Procession Passes By, op. 19, no. 2 [later orchestrated by Johan Halvorsen (1864-1935) as the Norwegian Bridal Procession]

1872
Edvard Grieg (1843-1907) completed the incidental music for Sigurd Jorsalfar, op. 22

May 1 – Hugo Alfvén (1872-1960) was born in Stockholm, Sweden

May 16 – Leokadiya Kashperova (1872-1940) was born in Lyubim, Russia

October 12 – Ralph Vaughan Williams (1872-1958) was born in Down Ampney, Gloucestershire, England

November 10 – L’Arlésienne Suite No. 1, op. 23bis, incidental music by Georges Bizet (1837-1875) was first performed in Paris, France

1873
January 19 – Cello Concerto No. 1 in A minor, op. 33, by Camille Saint-Saëns (1835-1921) was first performed in Paris, France

April 1 – Sergei Rachmaninoff (1873-1943) was born in Oneg, Novgorod, Russia

April 22 – Wiener Blut, op. 354, waltz by Johann Strauss II (1825-1899) was first performed in Vienna, Austria

November 2 – Variations on a Theme by Joseph Haydn, op. 56a, by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

November 10 – Henri Rabaud (1873-1949) was born in Paris, France

December 11 – String Quartet No. 1 in C minor, op. 51, no. 1, by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

1874
Johannes Brahms (1833-1897) completed Der Abend (The Evening) from Three Quartets, op. 64, no. 2

January 4 – Josef Suk (1874-1935) was born in Křečovice, Czech Republic

May 22 – Requiem by Giuseppe Verdi (1813-1901) was first performed in Milan, Italy

June 22 – Modest Mussorgsky (1839-1881) completed Pictures at an Exhibition, for piano

September 21 – Gustav Holst (1874-1934) was born in Cheltenham, Gloucestershire, England

1875
January 11 – Reinhold Glière (1875-1956) was born in Kyiv, Ukraine

January 24 – Danse macabre, op. 40, by Camille Saint-Saëns (1835-1921) was first performed in Paris, France

February 2 – Fritz Kreisler (1875-1962) was born in Vienna, Austria

March 3 – Carmen, opera by Georges Bizet (1837-1875) was first performed in Paris, France

March 7 – Maurice Ravel (1875-1937) was born in Ciboure, France

May 8 – Neue Liebeslieder Waltzes, op. 65, by Johannes Brahms (1833-1897) was first performed in Karlsruhe, Germany

June 3 – Georges Bizet (1837-1875) died in Bougival, France

September 15 – Louise Farrenc (1804-1875) died in Paris, France

October 31 – Piano Concerto No. 4 in C minor, op. 44, by Camille Saint-Saëns (1835-1921) was first performed in Paris, France

November 18 – Piano Quartet No. 3 in C minor, op. 60, by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

1876
Edvard Grieg (1843-1907) completed Ballade in the Form of Variations on a Norwegian Folk Song in G minor, op. 24, for piano

January 12 – Ermanno Wolf-Ferrari (1876-1948) was born in Venice, Italy

January 28 – Sérénade mélancolique in B♭ minor for violin and orchestra, op. 26, by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Moscow, Russia

February 24 – Peer Gynt, op. 23, incidental music by Edvard Grieg (1843-1907) was first performed in Oslo, Norway

November 4 – Symphony No. 1 in C minor, op. 68, by Johannes Brahms (1833-1897) was first performed in Karlsruhe, Germany

November 18 – Slavonic March in B♭ minor, op. 31, by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Moscow, Russia

November 23 – Manuel de Falla (1876-1946) was born in Cádiz, Spain

December 10 – Serenade for Strings in E major, op. 22, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

1877
March 4 – Swan Lake, op. 20, ballet by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Moscow, Russia

March 9 – Francesca da Rimini: Symphonic Fantasy after Dante, op. 32, symphonic poem by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Moscow, Russia

July 27 – Ernst von Dohnányi (1877-1960) was born in Bratislava, Slovakia

November 21 – Sigfrid Karg-Elert (1877-1933) was born in Oberndorf am Neckar, Germany

December 2 – Symphonic Variations, op. 78, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

December 9 – Cello Concerto in D minor by Édouard Lalo (1823-1892) was first performed in Paris, France

December 9 – Romance in F minor for Violin and Orchestra, op. 11, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

December 30 – Symphony No. 2 in D major, op. 73, by Johannes Brahms (1833-1897) was first performed in Vienna, Austria

1878
Vincent d’Indy (1851-1931) completed The Enchanted Forest (La forêt enchantée), op. 8

February 22 – Symphony No. 4 in F minor, op. 36, by Pyotr Ilyich Tchaikovsky (1840-1893) was first performed in Moscow, Russia

1879
L’Arlésienne Suite No. 2, incidental music by Georges Bizet (1837-1875) and compiled by Ernest Guiraud (1837-1892), was published

Nocturne in B major, op. 40, by Antonín Dvořák (1841-1904) was first performed in Nice, France

January 1 – Violin Concerto in D major, op. 77, by Johannes Brahms (1833-1897) was first performed in Leipzig, Germany

February 26 – Frank Bridge (1879-1941) was born in Brighton, England

March 4 – Symphony No. 2 in B minor (revised) by Alexander Borodin (1833-1887) was first performed in Saint Petersburg, Russia

May 16 – Czech Suite in D major, op. 39, by Antonín Dvořák (1841-1904) was first performed in Prague, Czech Republic

July 9 – Ottorino Respighi (1879-1936) was born in Bologna, Italy

October 19 – Symphony No. 5 in F minor for Organ, op. 42, no. 1, by Charles-Marie Widor (1844-1937) was first performed in Paris, France

October 21 – Joseph Canteloube (1879-1957) was born in Annonay, France

October 29 – Eight Pieces for Piano, op. 76, by Johannes Brahms (1833-1897) was first performed in Berlin, Germany

November 8 – Violin Sonata No. 1 in G major, op. 78, by Johannes Brahms (1833-1897) was first performed in Bonn, Germany

←1860s

1880s→

Otto Struve & Exoplanets, 1952

It’s too bad the remarkable Russian-born American astronomer Otto Struve (1897-1963) never lived to see the discovery of the first exoplanets, especially considering how he was probably the first to suggest the two main techniques by which they are now discovered.

The first discovery of something that could be called an exoplanet was announced in 1992 by the Polish astronomer Aleksander Wolszczan (1946-) and Canadian astronomer Dale Frail (1961-). They found two planets orbiting a neutron star 2,300 light years away in the constellation Virgo. This neutron star is the pulsar PSR 1257+12, which had only recently been discovered by Wolszczan (1990). The pulsar planets were detected using a variant of the Doppler (radial velocity) method, and a third planet was discovered by the same team in 1994. These planets likely formed from the debris disk formed when two white dwarf stars merged, so they could be considered “exotic” planets, quite unlike anything found in our solar system.

In 1995, the first exoplanet orbiting a “normal” star was announced by Swiss astronomers Michel Mayor (1942-) and Didier Queloz (1966-). Using the Doppler (radial velocity) method, they found a “hot Jupiter” orbiting the star 51 Pegasi at a distance of 51 light years (nice coincidence!).

In 1999, independent teams led by Canadian-American astronomer David Charbonneau (1974-) and American astronomer Gregory W. Henry (1972-) were the first to use the transit method to detect an exoplanet. They confirmed a hot Jupiter orbiting the star HD 209458 (also in Pegasus, another nice coincidence) 157 light years distant that had been discovered using the Doppler (radial velocity) technique only weeks earlier.

As you can see, the 1990s was the decade when exoplanetary science got its start!

Getting back to the prescience of Otto Struve—40 years prior to the discovery of the first exoplanets—Joshua Winn (1972-) in his newly-published The Little Book of Exoplanets writes:

Although the discovery of hot Jupiters came as a surprise, it’s not quite true that nobody foresaw them. In 1952, Otto Struve, an astronomer at the University of California at Berkeley, published a short paper pointing out that the precision of Doppler measurements had become good enough to detect planets—but only if there existed planets at least as massive as Jupiter with orbital periods as short as a few days. Setting aside the question of how such a planet might have formed, he realized there is no law of physics that forbids such planets from existing. In an alternate history, Struve’s paper inspired astronomers to launch a thousand ships and explore nearby stars for hot Jupiters. In fact, his paper languished in obscurity. None of the pioneers—neither Walker, Latham, Mayor, nor Queloz—were influenced by Struve’s paper. The planet around 51 Pegasi probably could have been discovered in the early 1960s, or surely by Walker in the 1980s, had the Telescope Time Allocation Committee allowed him to observe a larger number of stars.

Here is Otto Struve’s 1952 paper in its entirety (references omitted), published in the October 1952 issue of The Observatory.

PROPOSAL FOR A PROJECT OF HIGH-PRECISION STELLAR
RADIAL VELOCITY WORK

By Otto Struve

With the completion of the great radial-velocity programmes of the major observatories, the impression seems to have gained ground that the measurement of Doppler displacements in stellar spectra is less important at the present time than it was prior to the completion of R. E. Wilson’s new radial-velocity catalogue.

I believe that this impression is incorrect, and I should like to support my contention by presenting a proposal for the solution of a characteristic astrophysical problem.

One of the burning questions of astronomy deals with the frequency of planet-like bodies in the galaxy which belong to stars other than the Sun. K. A. Strand’s discovery of a planet-like companion in the system of 61 Cygni, which was recently confirmed by A. N. Deitch at Poulkovo, and similar results announced for other stars by P. Van de Kamp and D. Reuyl and E. Holmberg have stimulated interest in this problem. I have suggested elsewhere that the absence of rapid axial rotation in all normal solar-type stars (the only rapidly-rotating G and K stars are either W Ursae Majoris binaries or T Tauri nebular variables, or they possess peculiar spectra) suggests that these stars have somehow converted their angular momentum of axial rotation into angular momentum of orbital motion of planets. Hence, there may be many objects of planet-like character in the galaxy.

But how should we proceed to detect them? The method of direct photography used by Strand is, of course, excellent for nearby binary systems, but it is quite limited in scope. There seems to be at present no way to discover objects of the mass and size of Jupiter; nor is there much hope that we could discover objects ten times as large in mass as Jupiter, if they are at distances of one or more astronomical units from their parent stars.

But there seems to be no compelling reason why the hypothetical stellar planets should not, in some instances, be much closer to their parent stars than is the case in the solar system. It would be of interest to test whether there are any such objects.

We know that stellar companions can exist at very small distances. It is not unreasonable that a planet might exist at a distance of 1/50 astronomical unit, or about 3,000,000 km. Its period around a star of solar mass would then be about 1 day.

We can write Kepler’s third law in the form $V^{3} \sim \frac{1}{P}$ . Since the orbital velocity of the Earth is 30 km/sec, our hypothetical planet would have a velocity of roughly 200 km/sec. If the mass of this planet were equal to that of Jupiter, it would cause the observed radial velocity of the parent star to oscillate with a range of ± 0.2 km/sec—a quantity that might be just detectable with the most powerful Coudé spectrographs in existence. A planet ten times the mass of Jupiter would be very easy to detect, since it would cause the observed radial velocity of the star to oscillate with ± 2 km/sec. This is correct only for those orbits whose inclinations are 90°. But even for more moderate inclinations it should be possible, without much difficulty, to discover planets of 10 times the mass of Jupiter by the Doppler effect.

There would, of course, also be eclipses. Assuming that the mean density of the planet is five times that of the star (which may be optimistic for such a large planet) the projected eclipsed area is about 1/50th of that of the star, and the loss of light in stellar magnitudes is about 0.02. This, too, should be ascertainable by modern photoelectric methods, though the spectrographic test would probably be more accurate. The advantage of the photometric procedure would be its fainter limiting magnitude compared to that of the high-dispersion spectrographic technique.

Perhaps one way to attack the problem would be to start the spectrographic search among members of relatively wide visual binary systems, where the radial velocity of the companion can be used as a convenient and reliable standard of velocity, and should help in establishing at once whether one (or both) members are spectroscopic binaries of the type here considered.

Berkeley Astronomical Department, University of California.
1952 July 24.

Artificial Intelligence and Human Stupidity

There is no question that the continuing development of artificial intelligence (AI) technology will help humanity solve some difficult problems, with its ability to see patterns in complex data and arrive at novel solutions that any human mind would easily miss. But there is also no question that AI will be weaponized by those with ill intent to spread misinformation, destroy our privacy, and cleverly manipulate people to do their bidding. And it will enable a lot of us to do even less deep thinking and reflection then we do already.

Furthermore, if a significant fraction of the population won’t trust or believe humans who are experts in their field, why would they trust or believe AI insights guided by those same experts? Opportunists of questionable integrity and moral character always have been able to manipulate and distract the willfully or wantonly ignorant, and AI will make their job that much easier.

If we humans are to survive and thrive, we must address and solve fundamental human problems. I am not at all convinced that AI is going to help with that.

Population

How is AI going to reduce, over several generations, human population from its current 8 billion to a more sustainable 1 billion by lowering the birth rate uniformly world wide? Those of us alive today are currently burning through the Earth’s physical and natural resources at an unprecedented rate and degrading the Earth’s climate and ecology, all because there are about 7 billion too many people alive today.

Warfare

How is AI going to rid the world of nuclear weapons and other weapons of mass destruction? How is AI going to transform the world’s armies into agencies that provide humanitarian assistance, keep the peace, and enforce sensible international laws? How is AI going to transform the endless trillions the nations of the world spend on defense and warfare and redirect that vast sum of money to the betterment of humankind?

Fear and Hopelessness

How is AI going to rid the world of firearms and other weapons of self destruction?

Governance

How is AI going to ensure that the wisest, most knowledgeable, thoughtful, adaptable, intelligent, and compassionate people are our chosen leaders?

Pathological Behaviors

Will AI help us to understand why some people are hateful, or narcissistic, or violent, while most of us tend to be loving, altruistic, and peaceful—no matter what life throws at us? Will AI help us to truly and humanely rehabilitate those who begin exhibiting dangerous and antisocial behaviors?

Knowledge and Faith

Will AI help us to find a way for all religious believers to peacefully coexist with nonbelievers?

Or, will AI be just another technological distraction?

Classical Music Timeline: 1860s

1860
Franz Liszt (1811-1886) and Franz Doppler (1821-1883) completed the orchestral version of Hungarian Rhapsody No. 3 in D♭ major (S. 359, No. 3)

February 10 – Serenade No. 2 in A major, op. 16 (original version), by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

March 3 – Serenade No. 1 in D major, op. 11, by Johannes Brahms (1833-1897) was first performed in Hanover, Germany

May 4 – Emil von Reznicek (1860-1945) was born in Vienna, Austria

May 29 – Isaac Albéniz (1860-1909) was born in Camprodon, Catelonia, Spain

July 7 – Gustav Mahler (1860-1911) was born in Kaliště, Czech Republic

October 20 – String Sextet No. 1 in B♭ major, op. 18, by Johannes Brahms (1833-1897) was first performed in Hanover, Germany

December 18 – Edward MacDowell (1860-1908) was born in New York, New York

1861
January 15 – The Harp Rings Out, in C major, op. 17, no. 1 (SSA women’s chorus, horn, and harp), by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

The Death of Trenar, in C minor, op. 17, no. 4 (SSA women’s chorus, two horns, and harp), by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

Love Song, in E major, op. 44, no. 1 (SSAA women’s chorus & piano), by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

November 16 – Piano Quartet No. 1 in G minor, op. 25, by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

1862
January 29 – Frederick Delius (1862-1934) was born in Bradford, England

February 17 – Edward German (1862-1936) was born in Whitchurch, Shropshire, England

August 22 – Claude Debussy (1862-1918) was born in Saint-Germain-en-Laye, France

September 25 – Léon Boëllmann (1862-1897) was born in Ensisheim, France

1863
December 24 – Enrique Fernández Arbós (1863-1939) was born in Madrid, Spain

1864
March 15 – Johan Halvorsen (1864-1935) was born in Drammen, Norway

June 11 – Richard Strauss (1864-1949) was born in Munich, Germany

1865
Edvard Grieg (1843-1907) completed In Autumn, concert overture for orchestra, op. 11

June 9 – Carl Nielsen (1865-1931) was born in Sortelung, Denmark

June 10 – Tristan and Isolde, opera by Richard Wagner (1813-1883), was first performed in Munich, Germany

August 10 – Alexander Glazunov (1865-1936) was born in Saint Petersburg, Russia

October 1 – Paul Dukas (1865-1935) was born in Paris, France

October 13 – Cello Sonata No. 1 in E minor, op. 38, by Johannes Brahms (1833-1897) was first performed in Gdańsk, Poland

November 28 – Horn Trio in E♭ major, op. 40, by Johannes Brahms (1833-1897) was first performed in Zürich, Switzerland

December 8 – Jean Sibelius (1865-1957) was born in Hämeenlinna, Finland

December 17 – Symphony No. 8 in B minor, D. 759 “Unfinished” by Franz Schubert (1797-1828) was first performed in Vienna, Austria

1866
April 1 – Ferruccio Busoni (1866-1924) was born in Empoli, Italy

June 22 – Piano Quintet in F minor, op. 34, by Johannes Brahms (1833-1897) was first performed in Leipzig, Germany

October 11 – String Sextet No. 2 in G major, op. 36, by Johannes Brahms (1833-1897) was first performed in Boston, Massachusetts

1867
February 15 – The Blue Danube, op. 314, by Johann Strauss II (1825-1899) was first performed in Vienna, Austria

September 5 – Amy Beach (1867-1944) was born in Henniker, New Hampshire

1868
Gioachino Rossini (1792-1868) completed Péchés de vieillesse (“Sins of Old Age”)

January 5 – Violin Concerto No. 1 in G minor, op. 26, by Max Bruch (1838-1920) was first performed (in its present form) in Bremen, Germany

August 7 – Granville Bantock (1868-1946) was born in London, England

November 13 – Gioachino Rossini (1792-1868) died in Passy, France

November 15 – Waltz in A♭ major, op. 39, no. 15, by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

1869
January 16 – Symphony No. 1 in E♭ major by Alexander Borodin (1833-1887) was first performed in Saint Petersburg, Russia

February 18 – A German Requiem, op. 45, by Johannes Brahms (1833-1897) was first performed in Leipzig, Germany

March – Symphony No. 2, Antar (1st version) by Nikolai Rimsky-Korsakov (1844-1908) was first performed in Saint Petersburg, Russia

March 8 – Hector Berlioz (1803-1869) died in Paris, France

April 3 – Piano Concerto in A minor, op. 16, by Edvard Grieg (1843-1907) was first performed in Copenhagen, Denmark

←1850s

1870s→

Most Distant Human-Made Object

In 1895, Italian inventor and electrical engineer Guglielmo Marconi (1874-1937) produced the first human-made radio waves capable of traveling beyond the Earth, so radio evidence of the existence of human civilization has now traveled 128 light years from Earth. Assuming a stellar number density in the solar neighborhood of (7.99 ± 0.11) × 10⁻² stars per cubic parsec¹, Earth’s radio emissions have already reached about 20,000 star systems.

The most distant physical human-made object, however, is the Voyager 1 spacecraft, now over 160 AU from the solar system barycenter (SSB), a distance of almost 15 billion miles. That certainly sounds impressive by human standards, but that is only 0.0025 light years. As the distance of Voyager 1 from the solar system barycenter is constantly increasing, you’ll want to visit JPL Horizons to get up-to-date information using the settings below for your date range of interest. Delta gives the distance from the SSB to the Voyager 1 spacecraft in astronomical units (AU).

This still-functioning spacecraft that was launched on September 5, 1977, flew by Jupiter on March 5, 1979, and flew by Saturn on November 12, 1980, is now heading into interstellar space in the direction of the constellation Ophiuchus, the Serpent Bearer, near the Ophiuchus/Hercules border.

Given Voyager 1’s current distance (from Earth), a radio signal from Earth traveling at the speed of light would take 22 hours and 8 minutes to reach Voyager 1, and the response from Voyager 1 back to Earth another 22 hours and 8 minutes. So, when engineers send a command to Voyager 1, they won’t know for another 44 hours and 16 minutes (almost 2 days) whether Voyager 1 successfully executed the command. Patience is indeed a virtue!

Thanks to three onboard radioisotope thermoelectric generators (RTGs)², Voyager 1 should be able to continue to operate in the bone-chilling cold of deep space until at least 2025.

In about 50,000 years, Voyager 1 will be at a distance comparable to the nearest stars.

¹The Fifth Catalogue of Nearby Stars (CNS5)
Alex Golovin, Sabine Reffert, Andreas Just, Stefan Jordan, Akash Vani, Hartmut Jahreiß, A&A 670 A19 (2023), DOI: 10.1051/0004-6361/202244250

²At launch, the Voyager 1 RTGs contained a total of about 4.5 kg of plutonium-238, generating 390W of electricity.

Classical Music Timeline: 1850s

1850
Camille Saint-Saëns (1835-1921) completed Symphony in A major

September 21 – Hans Sitt (1860-1922) was born in Prague, Czech Republic

November 17 – String Quintet in C major, D. 956, op. posth. 163, by Franz Schubert (1797-1828) was first performed in Vienna, Austria

1851
February 6 – Symphony No. 3 in E♭ major, op. 97, “Rhenish”, by Robert Schumann (1810-1856) was first performed in Düsseldorf, Germany

March 27 – Vincent d’Indy (1851-1931) was born in Paris, France

1852
Robert Schumann (1810-1856) completed his final revision of the Symphonic Etudes, op. 13, for piano

March 14 – Manfred Overture, op. 115, by Robert Schumann (1810-1856) was first performed in Leipzig, Germany

November 21 – Francisco Tárrega (1852-1909) was born in Villarreal, Spain

1853
March 6 – Prelude, Act 1, from the opera La Traviata by Giuseppe Verdi (1813-1901) was first performed in Venice, Italy

May 15 – The 2nd version of Symphony No. 4 in D minor, op. 120 (much preferred by Clara Schumann and most often performed today) by Robert Schumann (1810-1856) was first performed in Düsseldorf, Germany

1854
February 23 – Les préludes, S. 97, symphonic poem by Franz Liszt (1811-1886) was first performed in Weimar, Germany

February 27 – Robert Schumann (1810-1856) attempted to drown himself in the Rhine River and, after being rescued, committed himself to a sanatorium in the Endenich quarter of Bonn, Germany, remaining there for the rest of his life.

July 3 – Leoš Janáček (1854-1928) was born in Hukvaldy, Czech Republic

September 1 – Engelbert Humperdinck (1854-1921) was born in Siegburg, Germany

1855
January 20 – Ernest Chausson (1855-1899) was born in Paris, France

February 17 – Piano Concerto No. 1 in E♭ major, S. 124, by Franz Liszt (1811-1886) was first performed in Weimar, Germany

May 12 – Anatoly Lyadov (1855-1914) was born in Saint Petersburg, Russia

June 13 – Overture to the opera I vespri siciliani by Giuseppe Verdi (1813-1901) was first performed in Paris, France

December 3 – Piano Trio in G minor, op. 15, by Bedřich Smetana (1824-1884) was first performed in Prague, Czech Republic

1856
Mikhail Glinka (1804-1857) completed the orchestral version of Valse-Fantaisie, in B minor

May 26 – George Templeton Strong (1856-1948) was born in New York, New York

July 29 – Robert Schumann (1810-1856) died in Bonn, Germany

1857
January 7 – Piano Concerto No. 2 in A major, S. 125, by Franz Liszt (1811-1886) was first performed in Weimar, Germany

February 15 – Mikhail Glinka (1804-1857) died in Berlin, Germany

June 2 – Edward Elgar (1857-1934) was born in Lower Broadheath, Worcestershire, England

September 5 – A Faust Symphony, S. 108, by Franz Liszt (1811-1886) was first performed in Weimar, Germany

1858
Camille Saint-Saëns (1835-1921) completed Piano Concerto No. 1 in D major, op. 17

April 22 – Ethel Smyth (1858-1944) was born in Sidcup, England

November 24 – Tritsch-Tratsch Polka in A major, op. 214, by Johann Strauss II (1825-1899) was first performed in Vienna, Austria

1859
January 22 – Piano Concerto No. 1 in D minor, op. 15, by Johannes Brahms (1833-1897) was first performed in Hanover, Germany

November 19 – Mikhail Ippolitov-Ivanov (1859-1935) was born in Gatchina, Russia

December 2 – Ave Maria, in F major, op. 12, by Johannes Brahms (1833-1897) was first performed in Hamburg, Germany

←1840s

1860s→

The Dimmest Constellation

You are probably familiar with at least the names of the twelve constellations of the zodiac:

Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpius
Sagittarius
Capricornus
Aquarius
Pisces

But are you familiar with the twelve constellations that have no stars brighter than 4th magnitude?

Antlia
Caelum
Camelopardalis
Chamaeleon
Coma Berenices
Corona Australis
Mensa
Microscopium
Norma
Sculptor
Sextans
Vulpecula

All but two of these dim constellations are, at least in part, visible from southern Arizona; Chamaeleon and Mensa require a trip south to see.

The southern constellation Mensa, the Table Mountain (declination -70° to -85°) is a ghost of a constellation, exhibiting no star brighter than magnitude 5.1. That’s 17 times fainter than Polaris! In fact, that’s fainter than all the stars of the Little Dipper asterism! Mensa does have one claim to fame, however. The Large Magellanic Cloud, satellite galaxy of our Milky Way galaxy, straddles most of the border that Mensa shares with Dorado, the Swordfish.

Mensa is far and away the dimmest constellation. But Mensa is a small constellation, bested in size by 74 of the 88 constellations. So perhaps it is not too surprising that a small constellation is less likely to harbor a bright star. Another measure of faint, perhaps, is to determine which of these twelve constellations with no star brighter than 4th magnitude is largest. That might be more remarkable, because one is less likely to find no bright stars in a large area of sky than in a small area of sky. By this measure, Camelopardalis, the Giraffe, wins without a doubt. Camelopardalis is the 18th largest constellation, and yet contains no star brighter than magnitude 4.0. It is that empty region you might have not noticed midway between Capella and Polaris, best viewed at evening twilight’s end during the month of February each year.