Eris: Plutoid, Dwarf Planet, or 10th Planet?

Eris was discovered on January 5, 2005 by Michael E. Brown, Chad Trujillo, and David A. Rabinowitz. Its orbit is more eccentric and more highly inclined than Pluto’s, and it is almost as large as Pluto, having a diameter that is 97.9% that of Pluto. Eris last came to perihelion on July 23, 1699 when it was in the constellation Virgo shining at a magnitude of 14.8, well beyond the reach of any telescopes existing at the time.

Pluto, Eris, and Satellites – Sizes and Orbital Distances to Scale

Eris has an orbit that is so eccentric (e = 0.44) that it actually spends some time each orbit closer to the Sun than Pluto is during the outer reaches of its orbit. Pluto’s aphelion distance is 49.31 AU, and Eris will be closer to the Sun than that for 99 years, from 2208 to 2307.

Eris is closer to the Sun than Pluto’s average distance of 40.70 AU for 43 years, between 2236 and 2279. Eris again reaches perihelion in 2257, when it will be 38.09 AU from the Sun.

Eris has an orbit that is tilted at nearly a 45° angle with respect to the ecliptic. This takes it through some interesting constellations during its 559-year orbital period. Here is its upcoming travel itinerary.

Upcoming Travel Plans for Eris (not subject to change1)

2022   Cetus
2036   Pisces
2059   Cetus
2064   Aries
2126   Perseus
2174   Camelopardalis
2197   Lynx
2208   Ursa Major
2237   Canes Venatici
2245   Coma Berenices
2256   Virgo
2274   Libra
2281   Hydra
2285   Centaurus
2286   Lupus
2298   Norma
2308   Ara
2320   Pavo
2357   Indus
2367   Tucana
2376   Grus
2399   Phoenix
2434   Sculptor
2487   Cetus

1 Unless the constellation boundaries are redrawn due to precession or other considerations

In Greek & Roman mythology, Eris is the goddess of strife and discord. 500 years hence, in 2522, Eris will once again be in Cetus, as it is today. But where will we be? What kind of life will our great-great-great-great great-great-great-great-great-great-great-great-great great-great grandchildren have in 2522? Here are some of my hopes for 2522.

  • Humanism will have replaced religion.
  • There will be no poverty in the world.
  • Everyone will have adequate health care, and it will be free.
  • Zero population growth will have been achieved by the only humane way possible: having fewer children.
  • There will be no more wars, no weapons of mass destruction.
  • There will be no need for guns, and no one will have them.
  • Violence will not be tolerated, nor will society glorify it or dwell on it in any way.
  • Individuals who “cross the line” and violate others through the use of physical violence will be psychologically re-engineered so they will live productive and fulfilling lives without being a threat to others. This neutralization of violent tendencies must be accomplished humanely and in a way that does not violate the individual’s essential humanity.
  • The Earth will be treated as the oasis it is.
  • Money will no longer exist, nor will it be needed.

Though no one alive today is likely to ever see any of these things, that in no way excuses us from working substantially towards these goals. To do anything less is a dereliction of moral duty.

Non-Profit Mail Overload

I receive enough solicitations in the mail from non-profit organizations to fill a 10-ream paper box every couple of months. I don’t think I have ever seen it this bad. I know that needs are great and worthwhile causes many, but giving $25 to an organization supporting cause xyz should not result in a dozen other organizations supporting similar causes mailing me multiple times each year.

There has to be a better way. Catalog companies had to solve this problem decades ago because of the expense of printing and mailing catalogs to existing and prospective customers. You mail your best customers often, those who don’t spend much or purchase infrequently less often, and prospective customers maybe once in a great while.

If the U.S. Postal Service continues to have financial problems, one source of revenue would be to increase the non-profit postage rate, and that would force many non-profit organizations to use a more sophisticated approach for their mailings.

Why not start now? I’d like to see a non-profit organization established whose sole purpose is to help other non-profit organizations to mail donors and prospective donors efficiently. Let’s give it a placeholder name: Nonprofit Mailing Association (NMA). Each participating non-profit organization would confidentially provide their donor lists and contribution history for each donor to NMA, and NMA in turn would use the data received from your organization and other non-profit organizations to rank-order donors based on likelihood to contribute and amount likely to contribute.

In the marketing business, this process is called “modeling”. Each model needs to take into consideration the amount you give (are you a $25 or $500 donor?), the frequency you give (monthly, 2-3 times a year, annually, or every couple of years or so), and to which non-profits. Other behaviors need to be taken into account. Does the donor tend to support organizations that they seek out directly, or are they more likely to respond to prospect mailings?

This modeling will result in fewer mailings but a lower acquisition cost per donor. From a donor standpoint, hopefully this will stop frequent mailings to individuals who have never donated to an organization. Once a year is often enough. Anything more borders on harassment. Besides, is the average person more likely to look at a non-profit mailing if they receive one in the mail on average each day or ten?

This approach should also apply to political organizations.

Using a more sophisticated approach to non-profit mailings will result in lower mailing and printing costs for the non-profit, and less printed material ending up in the recycling stream or—more often—the landfill.

A Case for Ten Planets

Clyde Tombaugh (1906-1997) spent the first fifteen years of his life on a farm near Streator, Illinois, and then his family moved to a farm near Burdett, Kansas (no wonder he got interested in astronomy!), and he went to high school there. Then, on February 18, 1930, Tombaugh, a self-taught amateur astronomer and telescope maker, discovered the ninth planet in our solar system, Pluto. It had been nearly 84 years since the eighth planet, Neptune, had been discovered, in 1846. And it would be another 62 years before another trans-Neptunian object (TNO) would be discovered.

Clyde Tombaugh made his discovery using a 13-inch f/5.3 photographic refractor at the Lowell Observatory in Flagstaff, Arizona.

Clyde Tombaugh was 24 years old when he discovered Pluto. He died in 1997 at the age of 90 (almost 91). I was very fortunate to meet Prof. Tombaugh at a lecture he gave at Iowa State University in 1990. At that lecture, he told a fascinating story about the discovery of Pluto, and I remember well his comment that he felt certain that no “tenth planet” larger than Pluto exists in our solar system, because of the thorough searches he and others had done since his discovery of Pluto. But, those searches were done before the CCD revolution, and just two years later, the first TNO outside the Pluto-Charon system, 15760 Albion (1992 QB1), would be discovered by David Jewitt (1958-) and Jane Luu (1963-), although only 1/9th the size of Pluto.

Pluto is, by far, the smallest of the nine planets. At only 2,377 km across, Pluto is only 2/3 the size of our Moon! Pluto has a large moon called Charon (pronounced SHAR-on) that is 1,212 km across (over half the size of Pluto), discovered in 1978 by James Christy (1938-). Two additional moons were discovered using the Hubble Space Telescope (HST) in 2005: Hydra (50.9 × 36.1 × 30.9 km) and Nix (49.8 × 33.2 × 31.1 km). A fourth moon was discovered using HST in 2011: Kerberos (10 × 9 × 9 km). And a fifth moon, again using HST, in 2012: Styx (16 × 9 × 8 km).

Pluto has been visited by a single spacecraft. New Horizons passed 12,472 km from Pluto and 28,858 km from Charon on July 14, 2015. Then, about 3½ years later, New Horizons passed 3,538 km from 486958 Arrokoth, on January 1, 2019.

Only one other TNO comparable in size to Pluto (or larger) is known to exist. 136199 Eris and its moon Dysnomia were discovered in 2005 by Mike Brown (1965-), Chad Trujillo (1973-), and David Rabinowitz (1960-). It is currently estimated that Eris is 97.9% the size of Pluto. Not surprisingly, in 2006 Pluto was “demoted” by the IAU from planethood to dwarf planet status. (Is not a “dwarf planet” a planet? Confusing…)

My take on this is that Pluto should be considered a planet along with Eris, of course. The definition of “planet” is really rather arbitrary, so given that Pluto was discovered 75 years before Eris, and 62 years before TNO #2, I think we should (in deference to the memory of Mr. Tombaugh, mostly) define a planet as any non-satellite object orbiting the Sun that is around the size of Pluto or larger. So, by my definition, there are currently ten known planets in our solar system. Is that really too many to keep track of?

There is precedent for including history in scientific naming decisions. William Herschel (1738-1822) is thought to have coined the term “planetary nebula” in the 1780s, and though we now know they have nothing to do with planets (unless their morphology is affected by orbiting planets), we still use the term “planetary nebula” to describe them today.

In the table below, you will find the eight “classical” planets, plus the five largest TNOs, all listed in order of descending size. (The largest asteroid, Ceres, is 939 km across, and is thus smaller than the smallest of these TNOs.)

You’ll see that the next largest TNO after Eris is Haumea, and that its diameter is only 67% that of Eris.

I’ve also listed the largest satellite for each of these objects. Venus and Mercury do not have a satellite—at least not at the present time.

It is amazing to note that both Ganymede and Titan are larger than the planet Mercury! And Ganymede, Titan, the Moon, and Triton are all larger than Pluto.

Largest Objects in the Solar System

Object Diameter (km) Largest Satellite Diameter (km) Size Ratio
Jupiter 139,822 Ganymede 5,268 3.8%
Saturn 116,464 Titan 5,149 4.4%
Uranus 50,724 Titania 1,577 3.1%
Neptune 49,244 Triton 2,707 5.5%
Earth 12,742 Moon 3,475 27.3%
Venus 12,104 N/A N/A N/A
Mars 6,779 Phobos 23 0.3%
Mercury 4,879 N/A N/A N/A
Pluto 2,377 Charon 1,212 51.0%
Eris 2,326 Dysnomia 700 30.1%
Haumea 1,560 Hiʻiaka 320 20.5%
Makemake 1,430 S/2015 (136472) 175 12.2%
Gonggong 1,230 Xiangliu 200 16.3%

Should any other non-satellite objects with a diameter of at least 2,000 km be discovered in our solar system, I think we should call them planets, too.

A Smarter TV

It seems to me that so-called “Smart TVs” just give you more of the same: corporately-curated, pay-to-subscribe, advertising-supported television.

I’d like to be able to create my own “channels” from websites and services that I choose. My channels would include:

  • PBS Passport
  • Curiosity Stream

Currently, I access these by selecting the content I want on a laptop computer which I’ve connected to my television.

It would be nice to have the web browser built into the television and a TV remote that includes a keyboard (real or virtual) and a touchpad (or arrow keys) to navigate website menus and enter text into search boxes. That way you could dispense with the connected laptop.

It would also be nice to be able to automatically and securely log in to each website by simply clicking on the channel icon. No apps to download, configure, or install.

Does such a television even exist?

Election Day Eclipse

The second of two total lunar eclipses this year visible from Tucson will occur early next Tuesday morning, November 8. Yes, this is Election Day in the U.S. Having a total lunar eclipse on Election Day is so rare that it has never happened before since the United States was founded in 1776. Whether or not our nation survives its current paroxysms, we can rest assured that lunar eclipses will continue to occur as they have for billions of years.

Here are the local circumstances for Tucson, Arizona.

Time (MST)EventAltitude
1:02 a.m.Penumbral Eclipse Begins69˚
~1:45 a.m.Penumbra First Visible?62˚
2:09 a.m.Partial Eclipse Begins57°
3:16 a.m.Total Eclipse Begins44°
3:59 a.m.Greatest Eclipse35°
4:42 a.m.Total Eclipse Ends26°
5:23 a.m.Astronomical Twilight Begins18°
5:49 a.m.Partial Eclipse Ends13°
5:52 a.m.Nautical Twilight Begins12°

There are few astronomical events as impressive as a total lunar eclipse, and we’ll have a front-row seat Election Day morning.

Every month, the full moon passes close to the Earth’s shadow, but because of the Moon’s tilted orbit it usually passes above or below the shadow cone of the Earth. This month is different!

Tuesday morning, the Moon orbits right through the Earth’s shadow. At 1:02 a.m., the Moon dips his proverbial toe into the Earth’s shadow, when the Moon is 69˚ above Tucson’s SW horizon. This is the undetectable beginning of the eclipse, when the leading edge of the eastward orbiting-Moon “sees” a partial solar eclipse. When no part of the Moon sees anything more than the Earth blocking some but not all of the Sun, we call that a penumbral eclipse. The very subtle penumbral shading may just begin to be detectable around 1:45 a.m.

When the partial eclipse begins at 2:09 a.m., the upper left edge becomes the first part of the Moon to “see” a total solar eclipse. In other words, from part of the Moon now, the Earth totally eclipses the Sun.

Totality begins at 3:16 a.m. when all of the Moon sees the Earth completely blocking the Sun. Mid-totality occurs at 3:59 a.m., when the center of the Moon is closest to the center of the Earth’s shadow. At that moment, the Moon’s coppery color should be darkest.

That color is caused by sunlight refracting (bending) through the Earth’s atmosphere and shining on the Moon even though from the Moon the Earth is completely blocking the disk of the Sun. The reddish or orangish color imparted to the Moon during totality is the combined light of all the world’s sunrises and sunsets. What a beautiful thought! Had the Earth no atmosphere, the Moon would utterly disappear from view during totality—the time it is completely within the Earth’s umbral shadow.

Totality ends at 4:42 a.m., and the partial eclipse ends at 5:49 a.m. during morning twilight. When the last vestiges of partial solar eclipse leave the Moon at 6:56 a.m., the (penumbral) eclipse ends at moonset as the Sun is rising in the ESE.

This leisurely event can be enjoyed with the unaided eye, binoculars, a telescope, or all three. Don’t let anyone in the family miss seeing it!

The next total eclipse will not grace our skies until March 13, 2025.

If you haven’t already done so, please be sure to vote! It is your responsibility that comes with the privileges of your living in these United States. And voting should only be the beginning of your civic involvement. The quality of our government and elected representatives is directly proportional to the sum total of our collective civic involvement. And that has been pretty poor in recent years. Unlike an eclipse, democracy is not a spectator sport!

Archimedes’ Constant

The number pi (π) can be simply stated: it is the ratio of a circle’s circumference (C) to its diameter (d).

\pi = \frac{C}{d}

The Greek mathematician Archimedes (c. 287 BC – c. 212 BC) was the first person to come up with a computational method of calculating π. He inscribed and circumscribed polygons with the same number of sides inside and outside of a circle. The value of π is between the perimeter of the inscribed polygon and the perimeter of the circumscribed polygon as shown in the diagrams below. By increasing the number of sides of the inscribed and circumscribed polygons, the value of π can be estimated more closely. The number π is thus sometimes called Archimedes’ Constant.

Archimedes’ method of calculating π

Archimedes’ Constant was not called π until Welsh mathematician William Jones (1675-1749) began using it in 1706. π is the first letter of the Greek word for periphery (περιφέρεια).

The number π (3.1415926535897932384626433…) has some remarkable properties, a few of which are

  • π cannot be expressed as a ratio of two integers (it is an irrational number).
  • The exact decimal representation of π has an infinite number of digits.
  • The decimal digits of π never exhibit a repeating pattern.
  • The decimal digits of π are randomly distributed, but this has not yet been proven.
  • π cannot be a solution of any equation involving only sums, products, exponents, and integers (it is a transcendental number).

It is worth noting that there are an infinite number of transcendental numbers (and, therefore, at least an infinite number of irrational numbers). But π is remarkable in that it pervades both mathematics and physics, often in ways that appears to have nothing to do with circles, spheres, or even geometry.

The value of π has now been calculated out to 100 trillion decimal places (1014) by Japanese computer scientist Emma Haruka Iwao. Like other recent attempts to calculate the most digits of π, Iwao used the Chudnovsky algorithm. Her record-breaking calculation took nearly 158 days using cloud computing between October 14, 2021 and March 21, 2o22.

Interestingly, the value of π can be calculated using a couple of simple infinite series.

The great Swiss mathematician Leonhard Euler (1707-1783) obtained the following:

\pi = \sqrt{6\left ( \frac{1}{1^{2}}+\frac{1}{2^{2}}+\frac{1}{3^{2}}+\frac{1}{4^{2}}+\cdots \right )}

And earlier, German mathematician Gottfried Wilhelm Leibniz (1646-1716) and Scottish mathematician David Gregory (1659-1708) independently arrived at an even simpler infinite series to generate π, though it converges so slowly that it is of little practical use.

\pi = 4\left ( \frac{1}{1}-\frac{1}{3}+\frac{1}{5}-\frac{1}{7}+\cdots \right )

Sagittarius Time Machine

The bright stars that outline our constellations beckon to us from a remarkably wide range of distances. Many of these stars are super-luminous giant stars and hot blue dwarf stars. More typical stars like our Sun—and the even more abundant red dwarf stars—are much too faint to see with our unaided eyes, unless they are only a few light years away. Thus many of the stars we see when we look up at the night sky are the intrinsically brightest ones, the “whales among the fishes.”

Trigonometric parallax directly provides us with the best estimate of the distance to each of these stars (provided they are not more than a few hundred light years away), and once you know the distance, it is easy to calculate when the light you are seeing tonight left each one of them. It is enjoyable to contemplate what was going on in Earth history when each star’s light began its long journey across interstellar space, the tiniest fraction of which is reaching your eyes as you look up on a clear night.

This article is the next in a series featuring the major stars of a prominent constellation. We turn now towards Sagittarius, which is currently crossing the celestial meridian at the end of evening twilight.

Below you will find a chart showing the constellation Sagittarius and the bright stars that define its outline. The official IAU-approved star names are listed, where available, or the Bayer designation. There’s a printer-friendly PDF version of this chart at the bottom of this article. There’s room for you to write in the year when the light we are currently receiving left the photosphere of each star, using the provided table (which is updated automatically to today’s date).

The “Teapot” asterism of Sagittarius

The table below contains all the relevant information. There are three tabs: Parallax, Distance, and Time. The first three columns of each tab show the star name, the Bayer designation, and the spectral type and luminosity class listed in SIMBAD.

On the Parallax tab, the parallax in millarcseconds (mas) is listed in column D, along with the uncertainty in the parallax in column E, and the year the parallax was published in column F. All are from SIMBAD. I will update these values as new results become available, but please post a comment here if you find anything that is not current, or is incorrect.

On the Distance tab, the parallax and parallax uncertainty for each star is used to calculate the range of possible distances to the star (in light years) in columns D through F. The nominal value given in column E is our current “best guess” for the distance to the star.

On the Time tab, the range of distances from the Distance tab are used to determine the range of years when the light we are seeing at this point in time would have left the star. The earliest year (given the uncertainty in parallax) is shown in column D, the most likely year in column E, and the latest year (given the uncertainty in parallax) in column F.

Here’s a printer-friendly PDF version of the Sagittarius chart where after printing you can enter the nominal year from column E of the Time tab next to the name for each star. The year values on the Time tab will update automatically to reference the current date.

Interest Connect

Make a list of your interests, either mentally or on paper. Are you curious about who else living in your area shares an interest with you? Wouldn’t it be nice if there were a safe online platform that would provide you with email addresses of others in your area who have a mutual interest so that you could exchange private emails? This might lead to a productive email exchange, meeting in person, forming an advocacy group, or working on a special project together. Two people or several. Your choice. And no advertising or marketing! I don’t think anything like this exists yet. Here’s my vision.

The name of the online platform will be Interest Connect.

A management organization (an independent non-profit entity or benefit corporation) will create and manage Interest Connect.

Each member will have a profile on the service that contains only the following basic information, viewable in its entirety only by the member and the management organization.

  • Your name (real name, no aliases)
  • Your email address
  • Your geographic region
  • Your interests

The list of geographic regions will be created and maintained by the management organization. The list will include the names of metro areas, subregions of metro areas, cities, towns, counties, and so on. Members can always ask for a new geographic region to be added. A member can only belong to one geographic region and will have no visibility into the other regions. There could, however, be visibility into levels of the same geographic region. For example: NW Tucson, Tucson, Pima County. Each member must provide proof of residency in their chosen geographic region by sharing their residential address with the management organization. That address will be independently verified, kept confidential, and will never be made public.

The management organization approves interest types and adds them to the list that members can select to add to their profile. There will be a large number of interests to choose from, and members can always ask for new ones to be added.

Some interests will be general, and others highly specialized.

Interest Connect is not a public discussion group, but a group to foster person-to-person private communication.  More than two members with the same interest could certainly arrange to communicate collectively amongst themselves via email.

As a member of Interest Connect, what would you see? You would see the names and email addresses of others in your geographic region that share the same interest as you.

Safety from predators is crucial, and the management organization will have complete authority to remove anyone from membership in Interest Connect that violates their terms and code of conduct.

Here’s a simplistic example showing four hypothetical individuals in the same geographic region. Interests A, B, C, D, E, F, and G are simply placeholders in our example for the actual interests that would be listed in Interest Connect.

Each member has a private profile that looks like this…

Marija Kelemen
Tucson, AZ
Interests: Interest A, Interest B, Interest C

Nikolaos Hubbard
Tucson, AZ
Interests: Interest D, Interest E, Interest F

Slavica Brankovič
Tucson, AZ
Interests: Interest B, Interest D

Aidan Storstrand
Tucson, AZ
Interests: Interest B, Interest D, Interest G

Each member would have visibility into other members like this…

Marija would see the following:

Interest B
Slavica Brankovič:
Aidan Storstrand:

Nikolaos would see the following:

Interest D
Slavica Brankovič:
Aidan Storstrand:

Slavica would see the following:

Interest B
Marija Kelemen:
Aidan Storstrand

Interest D
Nikolaos Hubbard:
Aidan Storstrand:

Aidan would see the following:

Interest B
Marija Kelemen:
Slavica Brankovič:

Interest D
Nikolaos Hubbard:
Slavica Brankovič:

Each member’s interest lists will be dynamic, so that interests can be added or removed at any time. Perhaps notifications could be set up (optionally) so that if someone new adds one of your interests, you will automatically be notified.

How to fund this noble endeavor without resorting to hosting irritating advertising? Each member would pay a modest annual membership fee. No mandatory automatic renewals, please!

What do you think? Has something like Interest Connect already been done somewhere? Do you have suggestions or concerns? I would be interested in hearing your thoughts. Feel free to post a comment here.

Peculiar Neutron Stars

There’s a lot we don’t know about neutron stars. Neutron stars are the densest objects we can directly observe, and we have little understanding of how matter behaves under such extreme conditions. Though there are a lot of neutrons in neutron stars, they are not entirely made of neutrons. Whether the interiors of neutron stars contain something other than the known elementary particles is an open question.

The nearest neutron star we know of is RX J1856.5-3754 in Corona Australis, just below Sagittarius. It regales us at a distance between 352 and 437 light years, with the most likely distance being 401 ly. Though most neutron stars we know of are pulsars (a good example of observational selection—we tend to discover what is easiest for us to discover), this one is not.

In addition to its intrinsic properties, how a neutron star looks to us also depends upon its orientation and the environs with which it interacts. These three factors have led to a variety of nomenclature that requires some explanation.

Pulsar – a highly-magnetized, fast-rotating neutron star whose magnetic poles emit beams of electromagnetic radiation. If either of the beams sweeps past the Earth, we observe periodic pulses of electromagnetic radiation coming from the neutron star.

Magnetar – an extremely-highly-magnetized, more-slowly-rotating neutron star that produces bursts of X-rays and gamma rays. Only some magnetars are pulsars. Anomalous X-ray pulsars (AXPs) are now thought to be magnetars.

Rotating Radio Transients (RRATs) – a neutron star that is a pulsar, but with the peculiar property that it emits a single short-lived and extremely bright radio burst quasi-periodically with long lulls in between. The radio bursts last only 2 to 30 milliseconds, with intervals ranging from 4 minutes to 3 hours between pulses.

Soft gamma repeaters (SGRs) – a neutron star—possibly a type of magnetar—that emits large bursts of gamma-rays and X-rays at irregular intervals. If not a magnetar, it may be a neutron star with a disk of material in orbit around it.

Compact Central Objects in Supernova remnants (CCOs in SNRs) – a radio-quiet X-ray-producing neutron star surrounded by a supernova remnant. These have thermal emission spectra, and a weaker magnetic field than most neutron stars.

X-ray Dim Isolated Neutron Stars (XDINS) – an isolated, nearby (otherwise, it would be too faint to see) young neutron star. Only seven of these have been discovered to date (see The Magnificent Seven).

And that’s not all. Clearly, we have a lot more to learn about neutron stars.

There are currently about 3,200 known neutron stars, almost all of them pulsars, and all of them in our Milky Way galaxy and the Magellanic Clouds. About 5% are members of a binary system.

I know of no comprehensive catalog of neutron stars, but here is a catalog of pulsars:

ATNF Pulsar Catalogue

A new and exciting frontier for exploring neutron stars is gravitational wave astronomy. All gravitational-wave observations to date have come from merging binaries consisting of black holes and neutron stars. Events include black hole – black hole mergers, neutron star – neutron star mergers, and neutron star – black hole mergers.

Three Pulsars of Note

The Fastest – PSR J1748-2446ad in the constellation Sagittarius is the fastest-spinning pulsar known, rotating once every 1.40 milliseconds, or 716 times per second (716 Hz). An educated guess at the neutron star’s radius (16 km) tells us that the equatorial surface is spinning at about 24% of the speed of light! PSR J1748-2446ad is located at a distance of about 18,000 ly in the globular cluster Terzan 5. Fortuitously, PSR J1748-2446ad is an eclipsing binary system with a bloated and distorted low-mass main-sequence-star companion.

The Slowest – PSR J0901-4046 in the southern constellation Vela is the slowest-spinning pulsar known*, rotating once every 75.886 seconds. It is located at a distance of approximately 1,300 ly.

The Most Massive – PSR J0952–0607 in the constellation Sextans is the most massive neutron star (2.35±0.17 M) known, and the second-fastest-spinning pulsar known (1.41 ms, 707 Hz). PSR J0952–0607 is located in a binary system with a (now) substellar-mass companion that has been largely consumed by the neutron star. The distance to this system is highly uncertain.

* The white dwarf in the red-dwarf – white-dwarf binary system AR Scorpii rotates once every 117 seconds, and is thought to be the only known example of a white-dwarf pulsar.


Liz Kruesi (2022, July 2). Slowpoke pulsar stuns scientists. Science News, 202(1), 8.

Govert Schilling (2022, July 28). Black widow pulsar sets mass record.

Dvořák – Symphony No. 8

Antonín Dvořák in 1890

Antonín Dvořák (1841-1904) was a remarkably talented composer, and though he is best known for his Symphony No. 9, “From the New World”, there is so much more to explore. Here is one writer, at least, who believes that his renown has not yet reached its peak.

One Dvořák compact disc that soars high above the crowd is the October 26, 1984 recording by the Cleveland Orchestra under Christoph von Dohnányi of Dvořák’s Symphony No. 8 and Scherzo capriccioso, released by Decca London in 1986. These are superlative performances.

This recording is still available through Presto Music, along with Dvořák’s other best symphonies, Nos. 7 & 9, and you might be able to find a copy of the original recording through Amazon, or elsewhere.

Dvořák composed and orchestrated his Symphony No. 8 in just two and a half months (August 26 to November 9) in 1889 at his summer resort in Vysoká u Příbramě, Bohemia (Czech Republic, today). The 8th is a high-energy work, cheerful and optimistic, with minor key excursions adding depth and emotional weight. Each of the four movements exhibit a tremendous variety of thematic material, much of it inspired by Bohemian folk music.

The first performance of the Symphony No. 8 in G major, op. 88 was on February 2, 1890 in Prague. During Dvořák’s extended stay in the United States, 1892-1895, he conducted the Exposition Orchestra (the Chicago Orchestra—later the Chicago Symphony Orchestra—expanded to 114 players) in a rousing performance of the 8th symphony and two other of his works at the 1893 Chicago World’s Fair. The August 12, 1893 performance was enthusiastically received by an audience estimated to number at least 8,000.

At that time, Dvořák’s symphonies were numbered in order of publication, and the first four were published after the last five, hence Symphony No. 4 = Symphony No. 8 today

Here are samples from each of the four movements, as performed by Christoph von Dohnányi conducting the Cleveland Orchestra in the fabulous recording recommended here.

Symphony No. 8 – Antonín Dvořák: I. Allegro con brio [excerpt]
Symphony No. 8 – Antonín Dvořák: II. Adagio [excerpt]
Symphony No. 8 – Antonín Dvořák: III. Allegretto grazioso [excerpt]
Symphony No. 8 – Antonín Dvořák: IV. Allegro, ma non troppo [excerpt]

This disc finishes out with another superb work by Antonín Dvořák, the Scherzo capriccioso in D♭ major, op. 66, written six years earlier in 1883. It also received its first performance in Prague, on May 16, 1883.

“Scherzo capriccioso” translates to “lively, playful character, with animated rhythm” (scherzo) and “capricious” (capriccioso). In other words, a capricious scherzo. And indeed it is—Enjoy!

Scherzo capriccioso – Antonín Dvořák [excerpt]