Comet C/2019 Y4 ATLAS was discovered on December 28, 2019 and is named after the observational program that discovered it: Asteroid Terrestrial-impact Last Alert System (ATLAS). It could become a naked-eye comet—if it doesn’t disintegrate as it gets closer to the Sun. Here’s an ephemeris for the remainder of April and May.
The young Finnish composer Jean Sibelius (1865-1957) wanted to be a virtuoso violinist but it was in composition that his greatest talent lay. All his life, he was deeply connected to the natural world, and this love of Nature is expressed in much of his music.
I know of no better introduction to the music of Jean Sibelius than the two CD set of his Symphonies No. 1, 2, and 4, and Finlandia and the Karelia Suite by Vladimir Ashkenazy conducting the Philharmonia Orchestra.
The earliest composition featured on this recording is the Karelia Suite, completed in 1893; the latest is the pensive Symphony No. 4, completed in 1911. All of the music on these discs is splendid, the performances inspired, and the recordings immersive.
Ashkenazy seems to have an innate understanding of Sibelius, and his conducting and interpretations shine here throughout.
As with many (most?) of the greatest composers, Sibelius faced a number of challenges and personal demons throughout his life. Though he lived a long and productive life, he wrote almost no new music after his brilliant tone poem Tapiola in 1926, 31 years before his death. He did complete a Symphony No. 8, but threw the score into his fireplace in 1945. Sibelius once remarked, “If I cannot write a better symphony than my Seventh, then it shall be my last.”
To find out more about the life and music of Jean Sibelius, I’d like to direct your attention to an excellent two-part documentary film by Christopher Nupen, completed in 1984. It is available through the classical music streaming channel medici.tv (highly recommended) and Amazon.
Henry Norris Russell (1877-1957) received his Ph.D. at Princeton in 1899 at just 21 years of age. Three years later—in 1902 when he was 24 years old and years before his discovery of the color-luminosity relationship now known as the Hertzsprung-Russell (H-R) diagram—Russell had an interesting article published in the journal Popular Astronomy that shows him already to be a meticulous and perspicacious observational astronomer. This article, completed 118 years ago this day, is reprinted below.
SHADOWS CAST BY STARLIGHT.
HENRY NORRIS RUSSELL.
FOR POPULAR ASTRONOMY.
It has long been known that Venus casts a distinct shadow; and the same thing has sometimes been observed in Jupiter’s case. More recently, it has been stated in the daily press* that shadows cast by Sirius have been seen at the Harvard Observatory in Jamaica, though it was then said that they could probably be seen only where the air is exceptionally clear.
The writer began to investigate this subject, quite independently, last November, and has found that the shadows cast by a number of the brighter fixed stars can be seen without difficulty under ordinary circumstances, provided proper precautions are taken to exclude extraneous light, and to secure the maximum sensitiveness of the observer’s eyes.
* Interview with Professor W.H. Pickering, New York Tribune, Jan. 18, 1902.
The most convenient method of observation is as follows: Choose a window from which the star is visible, while as little light as possible enters from terrestrial sources. Darken the room completely, with the exception of this window. Open the window, and screen down its aperture to an area of a square foot or less. Hold a large piece of white paper in the path of the star’s rays, as far from the opening as possible. The image of the opening will then appear on the paper.
It cannot, however, be well seen until the observer has spent at least ten minutes in the dark, (to rest his eyes from the glare of ordinary lights). The paper should be held within a foot or so of the eyes, as the faint patch of starlight is most easily visible when its apparent area is large. The shadow of any convenient object may now be made to fall on the screen, and may be observed. By holding the object near the window and noticing that its shadow is still sharp, the observer may convince himself that the light which casts the shadow really comes from the star.
By the method above described, the writer has succeeded in distinguishing shadows cast by the following stars, (which are here arranged in order of brightness):
|α Canis Majoris (Sirius)||– 1.4||ζ Orionis||1.9|
|α Bootis (Arcturus)||0.0||β Tauri||1.9|
|α Aurigae (Capella)||0.2||γ Geminorum||2.0|
|β Orionis (Rigel)||0.3||β Canis Majoris||2.0|
|α Canis Minoris (Procyon)||0.5||α Hydrae||2.0|
|α Orionis* (Betelgeuse)||0.8?||α Arietis||2.0|
|α Tauri (Aldebaran)||1.0||κ Orionis||2.2|
|β Geminorum (Pollux)||1.1||β Leonis||2.2|
|α Virginis (Spica)||1.2||γ Leonis||2.2|
|α Leonis (Regulus)||1.4||δ Orionis||2.4|
|ε Canis Majoris||1.5||η Canis Majoris||2.4|
|α Geminorum (Castor)||1.6||ζ Argus||2.5|
|ε Orionis||1.8||α Ceti||2.7|
|δ Canis Majoris||1.9||15 Argus||2.9|
The groups of stars comprised in the Pleiades and the sword of Orion also cast perceptible shadows. With a wide open window the belt of Orion should be added to this class.
Most of the observations on which this list is based were made at Princeton on February 7th, and 8th, and March 6th, 1902. The first of these nights is recorded as not remarkably clear, the others as very clear. Whenever there was any doubt of the reality of an observed patch of starlight, it was located at least three times, and it was verified each time that the star was really visible from the spot where its light had been located. Many more stars might have been added to the 29 in the foregoing list, had not unfriendly street lamps confined the observations to less than half the sky.
As many of the stars observed were at a low altitude, it may be concluded that a star of the 3rd magnitude, if near the zenith, would cast a perceptible shadow.
In attempting to get a shadow from these faint stars, the opening of the window should be narrowed to a width of a few inches, so as to cut off as much as possible of the diffused light of the sky. Care should be taken not to look at the sky while observing, as it is bright enough to dazzle the eyes for some little time.
By observing these precautions, the writer has been able to detect shadows cast by Sirius, Arcturus and Capella on moonlight nights,—in the case of Sirius, even when the Moon shone into the room.
The actual brightness of the screen, even when illuminated by Sirius, is very small in comparison with that of the “dark” background of the sky, as seen by the naked eye. White paper reflects about 80 per cent of the incident light. From photometric considerations, a disk of this material 1° in apparent diameter, illuminated perpendicularly by Sirius, should send us about 1/16,000 as much light as the star.
But, according to Professor Newcomb’s determination*, an area of sky 1° in diameter, remote from the Milky Way, sends us 9/10 as much light as a 5th magnitude star, or about 1/400 of the light of Sirius. Hence the sky is about 40 times as bright, area for area, as the paper illuminated by Sirius. The illumination of the paper by a 1st magnitude star is about 1/400 as bright, and by a 3d magnitude star less than 1/2000 as bright, area for area, as the “dark” background of the sky.
* Astrophysical Journal, December 1901.
This faint light, as might be anticipated, shows no perceptible color. The light of the white stars β and γ Orionis and the red star α Orionis does not differ sensibly in quality; but the light of the red star appears much fainter than the star’s brightness, as directly seen, would lead one to anticipate. On the screen, the light of α Orionis is much fainter than that of β, and only a little brighter than that of γ, while by direct vision α is much nearer to β than to γ in brightness. As β is 1 ½ magnitudes brighter than γ, it appears that, as measured by the intensity of its light on a screen, α Orionis is at least half a magnitude, perhaps a whole magnitude, fainter than when compared with the neighboring white stars by direct vision.
Such a result might have been anticipated à priori, since, in the ease of such faint lights as are here dealt with, the eye is sensitive to the green part of the spectrum alone, and this is relatively brighter in the spectrum of a white star than of a red one.
A much more interesting example of the accordance of theoretical prediction with observation is afforded by another phenomenon discovered by the writer, which is not hard to observe.
A surface illuminated by a planet—Venus for example—appears uniformly and evenly bright, but in the case of a fixed star, there are marked variations in brightness, so that the screen appears covered with moving dark markings.
This was predicted many years ago by Professor Young, in discussing the twinkling of the stars. He says*: “If the light of a star were strong enough, a white surface illuminated by it would look like the sandy bottom of a shallow, rippling pool of water illuminated by sunlight, with light and dark mottlings which move with the ripples on the surface. So, as we look toward the star, and the mottlings due to the irregularities of the air move by us, we see the star alternately bright and faint; in other words, it twinkles.”
General Astronomy, page 538 (edition of 1898).
It would be difficult to give a better description of the observed phenomenon than the one contained in the first part of the above quotation. It need only be added that the dark markings are much more conspicuous than the bright ones. This agrees with the fact that a star more frequently seems to lose light while twinkling than to gain it.
Sirius is the only star whose light is bright enough to make these light and dark mottlings visible without great difficulty, though the writer has seen them in the light of Rigel and Procyon. With Sirius they have been seen every time the star’s light has been observed on a moonless night. They are much more conspicuous when the star is twinkling violently than on nights when the air is steady. In the latter case there are only faint irregular mottlings, whose motion produces a flickering effect. More usually there appear also ill-defined dark bands, two or three inches wide. These are never quite straight nor parallel but usually show a preference for one or two directions, sometimes dividing the screen into irregular polygons. On some nights they merely seem to oscillate, but on others they have a progressive motion, which may be at any angle with their own direction. The rate of motion is very variable, but is greatest on windy nights,—another evidence of the atmospheric origin of the bands.
The best nights for observing these bands occur when the stars are twinkling strongly, and there is not much wind. The directions given above for observing shadows should be somewhat modified in this case.
If the room is not at the same temperature as the outer air, the window should be kept closed, as otherwise most of what is seen will be due to the air-currents near it. It is also desirable to have an area of star-light at least a foot square to see the bands in, so that a good sized part of the window should be left clear.
If Sirius is unavailable, Arcturus and Vega are probably the best stars in whose light to attempt to see the bands.
PRINCETON, N. J., March 24, 1902.
The remarkable composer and virtuoso pianist Sergei Rachmaninoff (1873-1943) wrote five works for piano and orchestra. The first four were his piano concertos.
Piano Concerto No. 1 in F♯ minor, Op. 1 (1891; revised 1917)
Piano Concerto No. 2 in C minor, Op. 18 (1901)
Piano Concerto No. 3 in D minor, Op. 30 (1909)
Piano Concerto No. 4 in G minor, Op. 40 (1926; revised 1941)
His 2nd and 3rd piano concertos are especially beautiful, and are among the finest examples of this genre in the entire repertory.
Then, in 1934, eight years after his final piano concerto, he wrote his final work for piano and orchestra, Rhapsody on a Theme of Paganini. It is a set of 24 variations in a single movement lasting 23 to 25 minutes. Its point of departure is the last of the 24 Caprices for Solo Violin, written between 1802 and 1817 by the great violinist Niccolò Paganini (1782-1840). Here is a performance of Caprice No. 24.
Kyoko Yonemoto playing Caprice No. 24 in A minor by Niccolò Paganini
And, oh, what Rachmaninoff does with this theme by Paganini! Energetic, scintillating, lush, virtuosic—these are just a few of the words that describe this incredibly dynamic and exciting work. It is the perfect introduction to Rachmaninoff’s music, and arguably his finest work—at least in terms of what he accomplishes in a mere two dozen minutes.
There are many fine recordings of this remarkable piece. I have several. Here they are, in order of duration.
23:00 Gary Graffman (1928-), New York Philharmonic, Leonard Bernstein (1918-1990)
23:01 Cecile Licad (1961-), Chicago Symphony, Claudio Abbado (1933-2014)
23:16 Adilia Alieva (living; birth year unknown), Orchestra Sinfonica do Samremo, Walter Proost (living; birth year unknown)
23:36 Vladimir Ashkenazy (1937-), London Symphony, André Previn (1929-2019)
23:44 Stephen Hough (1961-), Dallas Symphony, Andrew Litton (1959-)
24:56 Daniil Trifonov (1991-), Philadelphia Orchestra, Yannick Nézet-Séguin (1975-)
As you can see even from this small sample, a piece of music can be played with widely varying tempos and, of course, interpretations. The Trifonov recording is the latest addition to my collection, and you’ll note that it is a full 1m12s longer than the next longest interpretation, another great recording by pianist Stephen Hough.
I was bowled over by this Trifonov recording, and it is my current favorite. There is so much to savor here, and yet I never get the sense that the tempo is too slow. Time is certainly relative when it comes to music!
Looking in all directions, how many stars are there brighter than a particular visual magnitude? Here’s an empirical formula that gives an approximation. It can be used over the range mv = +4.0 to +25.0.
where S is the approximate number of stars brighter than apparent visual magnitude m in the entire sky
|Apparent Visual Magnitude||# of Stars|
How many stars are there in our Milky Way galaxy? Between 100 and 400 billion stars. Many stars are not very luminous, and can only be seen in the immediate solar neighborhood. That is one source of uncertainty.
How many galaxies are there in the observable universe? Something like two trillion (2 × 1012).
How many stars are in the observable universe? Something like a septillion (1024). A trillion trillion!
And, just so you know, our universe is probably much larger than the volume that we can observe.
How does the Universe love thee? Let us count the stars…
“How many stars are in the sky?”, Space Math, NASA Goddard Space Flight Center, accessed February 29, 2020, https://spacemath.gsfc.nasa.gov/weekly/6Page103.pdf.
Wikipedia contributors, “Galaxy,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Galaxy&oldid=942479372 (accessed February 29, 2020).
Wikipedia contributors, “Milky Way,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Milky_Way&oldid=942977760 (accessed February 29, 2020).
Yes, I’ve seen the Marfa lights. Bernie Zelazny and I were coming back from doing a star party for a culinary group at El Cosmico in Marfa on April 7, 2011 when we decided to stop at the Marfa lights viewing station just off of US 67/90. For the first couple of minutes (Thursday evening around 11:00 p.m. or so) we saw nothing, but then, sure enough, a slowly moving white light appeared near a small tower with red lights, providing a good point of reference for the motion. The light gradually changed brightness, sometimes brighter, sometimes dimmer, moving left to right, then disappeared. Soon, another would appear: sometimes higher, sometimes lower, usually moving to the right, but sometimes to left. My first thought: distant headlights. Sometimes, more that one could be seen at the same time.
Quickly, I ran back to my car to get the 15 x 70 binoculars and binocular mount (an Orion Paragon Plus) and set them up to view the Marfa lights, which by now were happening frequently. When viewing each Marfa light through these powerful binoculars, the first thing I noticed is that I was not able to focus! No matter how I changed the focus of the binoculars, I could do no better than to see a round amorphous blob of light.
Next, I decided to see if any of the fixed distant lights would focus. First the red tower lights. Nope, red blobs. Then a distant ranch light to the left of the light dome of Ojinaga/Presidio. Nope, a while blob. Then, another distant ranch light. Another white blob. Then some distant headlights on US 67/90 near Marfa heading toward Alpine. The headlights were too far away to resolve, and in the binoculars they, too, were an unresolvable white blob. Next I moved the binoculars up a few degrees to look at some stars. Perfect focus! Back down to the ground lights and Marfa lights: out of focus blobs!
So, it appears to me that some atmospheric phenomenon is defocusing and distorting terrestrial lights in the distance. Perhaps some sort of superior mirage. I think the most likely explanation for the Marfa lights is distant vehicle headlights.
Next steps in the investigation of this curious phenomenon: Use a micrometer eyepiece in a low-power rich-field telescope to measure the angular sizes of the Marfa light blobs, as well as the angular sizes of the blobs from identifiable terrestrial lights. Determine the distance to the terrestrial light sources in the daytime (if possible) using triangulation. Better yet, determine the great circle distance to each terrestrial light source by obtaining GPS coordinates of each of those light sources, and the Marfa lights viewing station. Even better would be to shine a mobile light source at the Marfa lights viewing station from various GPS-determined locations at different distances on an evening when the Marfa lights are visible. Determine if the size of each known light blob is a function of distance. Using this information, estimate the distance to the Marfa light sources.
Also, note whether the angular size of each Marfa light is related to its altitude above the horizon.
More ideas: Take a series of 30-second digital camera exposures over the course of an evening to determine if the Marfa lights take preferred paths. The results might support or refute the vehicle headlights hypothesis. Determine if the Marfa lights paths change from night to night or during the course of one night.
Finally, I’d suggest using the same kind of wide-field spectroscopic equipment used to obtain meteor spectra to determine the spectral characteristics of the Marfa lights. This would tell us much about their chemical composition, temperature, and origin.
The United States Postal Service has issued a number of enticing forever stamps in recent years, and I’ve begun accumulating stamps faster than I use them. Sound familiar? If so, why not use them for extra postage items—even if you end up spending a little more than is required.
The current value of a forever stamp is 55¢. If you have a postal scale at home to weigh the envelopes you want to post, this handy guide will show you how many forever stamps to use for envelopes of different sizes and weights. (Mail within the U.S. only)
Standard Envelopes (≤11.5″ long, ≤6.125″ high, ≤0.25″ thick)
- 0 to 1 ounce: 1 forever stamp
- 1 to 4 ounces: 2 forever stamps
- 4 to 8 ounces: 3 forever stamps
Large Envelopes (11.5-15″ L, 6.125-12″ H, or 0.25-0.75″ T)
- 0 to 1 ounce: 2 forever stamps
- 1 to 4 ounces: 3 forever stamps
- 4 to 7 ounces: 4 forever stamps
- 7 to 9 ounces: 5 forever stamps
- 9 to 12 ounces: 6 forever stamps
- 12 to 15 ounces: 7 forever stamps
If you are mailing a standard envelope that has one or more of the characteristics in DMM 101.1.2, add an ounce to the measured weight to cover the non-machinable surcharge.
If you are mailing a large envelope that is rigid, is non-rectangular, or is not uniformly thick, then take your envelope to the post office to mail because you will have to pay parcel prices.
What a strange world Iapetus is! The third largest satellite of Saturn—and the outermost of Saturn’s large satellites—is a moon of many mysteries. We’ll take a look at three of them.
Mystery #1: Iapetus appears to be an original satellite of Saturn, and yet unlike the other regular satellites, its orbit is inclined 15.5˚ relative to Saturn’s equator. The reason for this steep inclination is not well understood.
And, oh, the view! Iapetus is the perfect perch to view Saturn’s rings, as it orbits Saturn every 79.3 days in its steeply inclined orbit.
Mystery #2: Iapetus has the largest albedo dichotomy in the solar system. Why? Iapetus is locked in synchronous rotation as it orbits around Saturn, with the leading hemisphere ten times darker than its trailing hemisphere.
It is thought that the natural state of the Iapetian surface is the bright icy part, with the dark material a thin veneer, less than a meter thick.
Mystery #3: Iapetus has a shape consistent with a body spinning every ~16 hours and yet its rotation period is 79.3 days, and it has a prominent ridge that can be followed 3/4 of the way around the equator.
The surface of Iapetus is heavily cratered, indicating it is very old. Could two comparable-sized objects have collided almost head-on billions of years ago to form Iapetus?
As beautiful as spacecraft flyby and orbital images are of Iapetus and the many other interesting moons in our solar system, can you imagine what vistas await us once we start exploring their surfaces with rovers? Anticipation of these images and scientific discoveries surely is an impetus to explore the surface of Iapetus (and other moons) sooner rather than later.
Bonnefoy, Léa E., Jean-François Lestrade, Emmanuel Lellouch, Alice Le Gall, Cédric Leyrat, Nicolas Ponthieu, and Bilal Ladjelate. “Probing the subsurface of the two faces of Iapetus.” arXiv preprint arXiv:1911.03394 (2019).
Leleu, Adrien, Martin Jutzi, and Martin Rubin. “The peculiar shapes of Saturn’s small inner moons as evidence of mergers of similar-sized moonlets.” Nature astronomy 2, no. 7 (2018): 555-561.
Rivera-Valentin, Edgard G., Amy C. Barr, EJ Lopez Garcia, Michelle R. Kirchoff, and Paul M. Schenk. “Constraints on planetesimal disk mass from the cratering record and equatorial ridge on Iapetus.” The Astrophysical Journal 792, no. 2 (2014): 127.
Climate change is a serious problem requiring immediate attention. We need to reduce greenhouse gas emissions into our atmosphere as fast as possible. Half measures will not do. We are rapidly running out of time before the quality of life for all humans on planet Earth declines, especially for the economically disadvantaged.
A precipitous decline in biological diversity due to habitat loss and extinction of species is of greater concern, and yet it gets very little attention in the mainstream media. While climate change will render large areas of the Earth uninhabitable, biodiversity loss will lead to a partial or complete collapse of the ecosystem humans depend upon for food.
Getting even less attention is the cause of both of these problems: overpopulation. If you were born in 1973, the world’s human population is now twice what it was then. If you were born in 1952, there are three times as many people alive now than there were then. We have a climate emergency and a biodiversity emergency because we have a population emergency. The number of humans on this planet needs to decline, and the only humane way to accomplish that is to have fewer children. It is that simple.
And, yet, we often see this or that news article lamenting the fact that the birth rate in this or that country is too low. That’s crazy! A low birth rate should be a cause for celebration given the current state of the world and its environment. Certainly, a low birth rate does lead to some economic challenges, but these pale in comparison to the challenges we will face if population (and consumption) continue to grow.
As a humanist, I believe that we should do all we can to alleviate and eliminate human suffering. It is our highest moral calling. To be sure, some human suffering is inevitable and necessary when an individual makes poor decisions and suffers the consequences before hopefully making a mid-course correction. But the kind of suffering I am talking about is suffering that is imposed upon a person through no fault of their own, be it the cruelty of other human beings, or the cruelty of nature.
In this light we can see that our economic systems, governments, and most religions are utterly failing us. Nothing short of drastic changes will solve these problems. May wisdom, intelligence, ingenuity, and compassion guide us, rather than fear, ignorance, hatred, and dogma.
There is an organization dedicated to stabilizing human population throughout the world by lowering the birth rate: Population Connection. I encourage you to support their work as I do.
Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites. In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.
I’ve put together a video montage of satellites I serendipitously recorded between August 9, 2019 and December 22, 2019. Many of the satellite crossings are moving across the fields as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.
Satellites in higher orbits take longer to cross the field. In the next video, the originally geosynchronous satellite OPS 1570 (IMEWS-3, “Integrated Missile Early Warning System”) is barely visible until it exhibits an amazing sunglint around 3:41:22 UT.
I caught one meteor on October 6, 2019 at 9:57:43 UT. Field location was UCAC4 515-043597. The meteor was a Daytime Sextantid, as determined using the method I described previously in There’s a Meteor in My Image. The meteor even left a brief afterglow—a meteor train!
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21