Meteor Shower “Clumpiness”

Have you ever noticed while watching a major meteor shower like the Geminids, Perseids, or the Leonids (esp. 1997-2002) that meteors come in clumps?  Often, you’ll see a bunch of meteors over a period of one to five minutes, followed by several (sometimes many) minutes with nothing.  In other words, if a rate of 60 meteors per hour is predicted, that does not mean you will see a meteor each minute!  Not even close.  This indicates that the particles in a meteor stream are somewhat bunched together rather than evenly distributed in space.

I can’t tell you how often someone has told me that they went out to watch meteor shower x, y, or z and didn’t see a thing.  Invariably, when I ask “how long did you watch?” they say something like 5, 10, or 15 minutes.  That’s not long enough!  If you’re serious about seeing some impressive meteor activity you really need to be out for two hours minimum, at a time when the meteor shower radiant is above the horizon.  Look generally toward the radiant direction—unless the Moon is in your field of view, in which case you will want to look in a direction opposite the Moon.  You also need to be reasonably well dark-adapted, and that means—ideally—no terrestrial lights should be in your field of view that are brighter than the brightest stars.

Turn Down the Lights, Turn Up the Stars

We are presently witnessing a rapid transformation of our outdoor nighttime environment as many older lighting sources such as high pressure sodium, metal halide, and fluorescent are being replaced with solid state lighting, specifically light emitting diodes (LEDs).  Many of the lighting decisions being made today with little or no citizen input will have consequences that impact our nighttime environment for decades.

Rather than continuing to subscribe to the “more is better, dusk-to-dawn” approach to outdoor lighting, we need to utilize this new technology in creative and innovative ways (many already available) to improve our nighttime built environment while minimizing lighting’s deleterious effects on the natural world.  Three paradigm shifts are needed.

Paradigm Shift #1
Less light will usually work just fine (a little light goes a long way)

Paradigm Shift #2
Dusk-to-dawn lighting → Lighting on Demand

Paradigm Shift #3
Full intensity lighting → Multi-Intensity Lighting (dimmable)

When choosing the amount of light you need, one should always consider the task or tasks needing to be performed.  For example, the amount of light needed to identify a rural intersection is much less than is needed to play a baseball game at night.  In both cases, though, the light needs to be restricted to only the area needing to be illuminated: the intersection or the playing field.

Another example.  When my wife and I bought a house in Dodgeville, Wisconsin back in 2005, our front porch had a 100-watt frosted incandescent light bulb to light the porch that we could turn on whenever we had company in the evening.  Thinking it too bright, we replaced the 100-watt bulb with a 60-watt bulb, then tried a 40-watt bulb, and finally a 25-watt bulb.  The 25-watt bulb adequately illuminated the porch and the stairs leading up to the porch, so in it stayed.

Then there is the issue of dusk-to-dawn lighting.  Many years ago, we switched outdoor lighting on or off as needed, but technological advancements later allowed us to have a light come on at dusk and stay on all night until dawn.  Now, think of all those lights burning when no one is there to use them.  If security is a concern, there is even newer technology that will do a far more effective job of detecting intruders than simply leaving a light on all night long.  In fact, a dusk-to-dawn light is not needed at all as part of an effective security system.  So, why not use 21st-century technology to have outdoor lights automatically turn on when needed and turn off when not needed?  Some LED light bulbs even come now with integrated occupancy sensors.  Lighting on demand could and should be replacing most dusk-to-dawn lighting within the next few years.

What about some roadway and parking lot lighting that must remain on all night long?  Those lights could be at full brightness during times of high traffic such as during the evening hours, but dimmed to 50% when traffic is lower, such as after midnight.  Once again, 21st-century technology makes this easy to do.

LED lighting lends itself very well to frequent on-off switching and dimming, but much of what is currently being installed is too blue.  As you can see in the table below, typical LED light sources have a substantial “spike” at the blue end of the visible light spectrum as compared with other white light sources.

Not only does blue light scatter more in the atmosphere and within our eyes, but many people perceive bluish-white light as colder, more clinical, than the warmer white light where this blue spike is absent, as shown below.  The blue spike in LED lighting can be removed either by using filtering, or by using a different phosphor that gives a warmer white spectrum.  Strongly preferred for both indoor and outdoor lighting are LED light sources with a correlated color temperature (CCT) of 2700K or 3000K.  2700K is the standard for indoor lighting, and yet 4000K is most often used for outdoor lighting.  Why?  Let’s move the standard for outdoor lighting to 2700K or 3000K.

By properly shielding lights so they only shine downwards, by using lights that are no brighter (or bluer) than they need to be, and by turning lights off when they are not needed—or dimming them during times of lower activity—we all will be helping to improve both our natural and celestial environment.

Turn Down the Lights, Turn Up the Stars *

* Suzy Munday, May 11, 2018

Additional Thoughts

In thinking about 21st-century lighting, one’s thoughts naturally towards 21st-century power generation.  We do not think often enough about the many advantages of a more decentralized power grid, where nearly everyone is generating some power with solar panels and small-scale wind turbines, as well as other local sources of energy such as geothermal.   As we once again consider building nuclear power plants (which will still be quite vulnerable to terrorism) and continue to build expensive fossil fuelish power plants and ugly high-voltage transmission lines, why not a paradigm shift towards decentralized energy production instead?

Lovely Coma Berenices

One of the special joys of getting out under a dark rural sky this time of year is seeing the gossamer beauty of the surprisingly expansive star cluster called Melotte 111, also known as the Coma star clusterMel 111 makes up a large part of the constellation Coma Berenices, “Berenice’s Hair”.  This constellation, which entertains the North Galactic Pole as well as a gaggle of galaxies, can be found about midway between Denebola (some call the Coma star cluster the end of the “tail” of Leo the Lion) and Arcturus, as well as midway between Spica and the Big Dipper.  Coma Berenices is transiting the meridian this week as evening twilight ends.  At a distance of just 284 light years, the Coma star cluster is the third nearest star cluster to us, surpassed only by the open cluster remnant Collinder 285—the Ursa Major association (80 ly)—and the Hyades (153 ly).

One Good Shirt Deserves Another

Who hasn’t tried to replace an article of clothing when it finally wears out, only to find that it is no longer available?  When I find something I like, I like to stick with it—or at least something quite similar.  Increasingly, I am having a harder and harder time finding clothing I like.  Is it my age?

Take, for example, long sleeve shirts.  I like button-down dress casual shirts, but if you’re looking for a pattern shirt that doesn’t include blue, good luck.  Look at the shirt below.  It goes well with tan or brown pants, but I can’t find anything like it anywhere!  For such a basic style, this really surprises me.

Here’s a close-up showing the pattern:

So, the moral of the story is if you find an article of clothing you like, purchase another two of them right away, because there’s no guarantee it will be available (or of the same quality) in a couple of years when you’ll be wanting to replace it with something comparable.

Unless, of course, it is blue.

Interstellar Object 1I/2017U1 ‘Oumuamua

After years of searching and hypothesizing, we have finally discovered a macroscopic object passing through our solar system that came from interstellar space!  An elongated rocky object with approximate dimensions 755 × 115 × 115 ft. entered the solar system from the direction of the constellation Lyra at a velocity (v) of 26 km/s (16 mi/s or 58,000 mph), and will exit the solar system at essentially the same speed in the direction of the constellation Pegasus, within the Great Square.

This interstellar object (ISO) is called 1I/2017U1 ‘Oumuamua.  What’s in a name?  A lot!  Let’s separate the three different parts of this designation, discussing each in turn.

1I – “I” stands for “interstellar” and “1” indicates that it is the first interstellar solar system visitor discovered.

2017U1 – indicates that it was the first object discovered during the half-month October 16-31 in the year 2017.

‘Oumuamua [pronunciation] is a Hawaiian word for “scout”, reflecting how this object is like a scout or messenger reaching out to us from the distant past.

‘Oumuamua Enters the Solar System

Here’s a brief timeline of the encounter.

September 9, 2017 – Closest approach to the Sun (0.26 AU)

October 14, 2017 – Closest approach to the Earth (0.16 AU)

October 19, 2017 – Discovered by Robert Weryk with Pan-STARRS

It is very difficult for us to discover objects coming towards us from the inner solar system and the glare of the Sun, so it is not surprising that ‘Oumuamua was discovered after it had passed by the Earth on its way out of the solar system.

‘Oumuamua in the Inner Solar System
NASA Animation Showing ‘Oumuamua’s Journey Through the Inner Solar System
‘Oumuamua Exits the Solar System

Rob Weryk, a post-doc at the University of Hawaii Institute for Astronomy, discovered ‘Oumuamua in images taken by the Pan-STARRS1 1.8-meter Ritchey–Chrétien telescope at the summit of the dormant volcano Haleakalā on the island of Maui.  Pan-STARRS is an acronym for “Panoramic Survey Telescope and Rapid Response System” and is primarily used to search for Near Earth Objects (NEOs).  It has been estimated that Pan-STARRS should be able to detect an interstellar object like ‘Oumuamua passing through our solar system about once every 5 years.

But the 8.4-meter Large Synoptic Survey Telescope (LSST) in Chile, which will see first light in 2019, is expected to be able to detect at least one interstellar object passing through our solar system each year.

While we don’t know ‘Oumuamua’s place of origin, we do know that it originated outside our solar system, and that is exciting.  Was it ejected from a binary system?  Is it an “extinct” interstellar comet?  Perhaps it is a former asteroid of a dying star.  Even our own Sun, which is expected to reach a peak luminosity of 5200 L as a red giant star in a few billion years, will lose mass and transition to a white dwarf, causing a dynamical reshuffling that will eject a large number of asteroids, trans-Neptunian objects, and comets from our solar system (Seligman & Laughlin 2018).  Perhaps ‘Oumuamua long ago suffered a similar fate.

References
McNeill, A., Trilling, D. E., Mommert, M. 2018, ApJL, 857, L1 (arXiv:1803.09864)
Seligman, D. & Laughlin, G. 2018, AJ, in press (arXiv:1803.07022)

Howard Goodall

I first became familiar with British composer, musician, and music presenter extraordinaire Howard Goodall on August 7, 2017, when his documentary Sgt. Pepper’s Musical Revolution aired on Wisconsin Public Television.  As a lifelong Beatlephile who knows a thing or two about the Beatles and their music, I was immensely impressed with the quality and content of this documentary.  I especially liked his detailed analysis (vis-à-vis Alan W. Pollack) of what makes the music of the Beatles so extraordinary, and his obvious enthusiasm for the subject.  After watching this wonderful hour-long (yes, no commercials!) programme, I vowed to do two things:

  1. Purchase an official DVD copy of Sgt. Pepper’s Musical Revolution
  2. Find out more about Howard Goodall and his work

#1  Sad to say, periodic searches have only turned up bootleg copies from questionable sources.  When will the DVD finally be released?

#2  Somehow I missed it when it was originally broadcast on PBS, but I was delighted to find Howard Goodall’s Big Bangs available through Netflix, so I recently ordered it.

First broadcast in the UK in the autumn of 2000, Howard Goodall’s Big Bangs is a series of 50-minute documentaries on five transformative developments in the history of Western music.  They are

  1. Notation
  2. Equal Temperament
  3. Opera
  4. The Piano(forte)
  5. Recorded Sound

I just finished watching this series, and would highly recommend it for anyone interested in music history.

I enthusiastically look forward to other music documentaries by Howard Goodall.  After watching Sgt. Pepper’s Musical Revolution, I believe that he may well be the best person in the world to develop an entire documentary series on the music of The Beatles.  Here’s hoping!

There are those who say that if music has mass appeal it can’t also be music of great significance or depth. What The Beatles proved once and for all is that this idea is hopelessly and absurdly wrong. – Howard Goodall

There are very, very few composers in history whose work changed all the music that followed it: Beethoven was one, Wagner was another. I believe that posterity will add to their select ranks The Beatles. – Howard Goodall

M81 and M82 from HST

The galaxy pair M81 and M82 in Ursa Major must rank near the top of the list of best-loved objects for any Northern Hemisphere amateur astronomer.  So, to see such a familiar object as these in breathtaking Hubble Space Telescope detail is thrilling indeed:

Messier 81 from the Hubble Space Telescope – click on the image for a larger view
Messier 82 from the Hubble Space Telescope – click on the image for a larger view

M81 and M82 lie little more than a moon-width apart in the constellation Ursa Major, 11.8 million and 11.5 million light years, respectively, from Earth.  Check out this pretty pair with either binoculars or a telescope any clear evening during the next few days.  Both galaxies transit the meridian on April 14 at the end of evening twilight, so this is the perfect time to observe them at their highest in the sky.  You can find Bode’s Galaxy (M81) and the “Silver Sliver” (M82) by drawing an imaginary diagonal across the bowl of the Big Dipper, opposite (rather than along) the handle, and extending the diagonal beyond the bowl almost as far as the two bowl stars are apart. Or, using the chart I created below, draw an imaginary line between Dubhe and 24 UMa, then go about four-fifths of the way to 24 UMa.  M81 & M82 lie about 0.4° (a little less than a moon-width) perpendicular to that line on the Polaris side.  Bingo, you’ve got ’em!

Skyline to M81 (and M82)

 

Iapetus – Wow!

Saturn’s third largest moon, Iapetus (eye-AP-eh-tuss), was discovered at the then-new Paris Observatory in 1671 by Italian-French astronomer (and observatory director) Giovanni Domenico (Jean-Dominique) Cassini (1625-1712).  Upon further observation, Cassini noted that he could only see Iapetus when it was on the west side of Saturn, never the east.  His telescope was not large enough to detect Iapetus on the east side of Saturn because it was much fainter then.  He correctly reasoned that, “it seems, that one part of his surface is not so capable of reflecting to us the light of the Sun which maketh it visible, as the other part is.”  He also must have realized that Iapetus was locked in synchronous rotation—as is our Moon—with the same side facing Saturn all the time, with its rotation period being equal to its orbital period.  Today we know these periods to be 79.3215 days.

The leading hemisphere of Iapetus has a visual albedo of only about 5%, whereas most of the trailing hemisphere is much brighter, having an albedo around 25%.  Thus, when Iapetus is on the west side of Saturn, its apparent visual magnitude is around 10.2, but on the east side of Saturn Iapetus is 1.7 magnitudes fainter at 11.9.  Without a doubt, Iapetus is one of the most outlandish places in the solar system, and the Cassini Saturn orbiter flybys certainly amplified the strangeness.

Cassini made one close targeted flyby of Iapetus on September 10, 2007, passing within 762 miles of the surface.  Here are a few of the best photos of Iapetus from Cassini.

The first high-resolution glimpse of the bright trailing hemisphere of Saturn’s moon Iapetus
This is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn’s moon Iapetus on Sept. 10, 2007 showing its prominent equatorial ridge—still a mystery
The “Himalayas” of Iapetus
Dark Terrain Up Close
The Transition Zone
Closest View of Iapetus
Dark material splatters the walls and floors of craters in the surreal, frozen wastelands of Iapetus
May 30, 2017 – Cassini bids farewell to Saturn’s yin-and-yang moon, Iapetus

The dark material appears to have been deposited from elsewhere in the Saturnian system, but sublimation of water ice may also play a role.  In any event, the dark material is a relatively thin veneer, significantly less than a meter thick in many places.

The warm day on Iapetus sees a surface temperature of -227° F on the dark terrain and an even colder -256° F on the bright terrain.  Inhospitable, to say the least!

Pole Stars

Currently, Polaris (Alpha α UMi) shines at magnitude 2.0 and lies just 0.7° from the North Celestial Pole (NCP).  Precession of the Earth’s rotation axis will bring the NCP to within 0.5° of Polaris in March 2100, its minimum distance.

The situation for the South Celestial Pole (SCP) is not such a happy circumstance.  The nearest naked-eye star to the SCP at present is neither near nor bright.  Sigma Octantis at magnitude 5.5 is not easy to see with the unaided eye, and being 1.1 degrees away from the SCP doesn’t win it any awards.  Besides, precession is moving the SCP farther away from Sigma Oct, not nearer.

One wonders, will precession someday bring us a south celestial pole star worthy of the name?  Even, perhaps, comparable to Polaris?  Here’s what our stargazing descendants can look forward to:

Cha = Chamaeleon; Car = Carina; Vel = Vela

So, around 8100 A.D. Iota Carinae and around 9220 A.D. Delta Velorum will serve admirably as southern pole stars every bit as good as Polaris does now in the northern hemisphere.

Now, for the northern hemisphere…

Cep = Cepheus

Up until the year 10,000 A.D., no northern pole star will be as good as Polaris is now, though 4.8-magnitude 9 Cephei will be very close to the north celestial pole around 7400 A.D.

Thought you might enjoy seeing what deep sky objects will come close to the celestial poles, so those are listed in the above tables as well.

March for Our Lives

I am so very proud of what hundreds of thousands of Americans of all ages did today, marching in hundreds of anti-gun-violence rallies all across our nation.  I’m especially proud of the students.  We had a huge group of marchers in Mineral Point, Wisconsin (students included), and I was glad I participated.

I do not want to live in a world where everyone is armed to the teeth.  You know, you have to decide what kind of a world you want to live in and then work towards that goal, no matter how difficult.

Paul McCartney at a March for Our Lives event in New York City

I was devastated and angry when John Lennon was shot to death in New York in 1980 outside his apartment building by a very disturbed man (it is almost always a man, isn’t it?).  I mean, who the hell would kill a musician?  I will never get over it On that day (and many times since), I decided “enough is enough”.  Gun ownership should be a privilege that has to be earned, not a right.  And weapons of war do not belong in the hands of private citizens—ever.  If that involves repealing the Second Amendment to the United States Constitution, then so be it.  But “we the people” never get a chance to vote on gun issues, do we?

If gun owners in this country can’t support much stricter and sensible gun laws, then maybe we should peacefully go our separate ways.  Gun lovers can have their country (a dystopia, really), and the rest of us can live somewhere else.

“The young do not know enough to be prudent, and therefore they attempt the impossible, and achieve it, generation after generation.”

– Pearl S. Buck (1892-1973)