Some Bright and Deep Eclipsing Binaries

Here are the four brightest eclipsing binaries north of declination -30°, in order of brightness:

Menkalinan Algol Mintaka Alphecca
Beta Aurigae Beta Persei Delta Orionis Alpha Coronae Borealis
5h 59m 32s 3h 08m 10s 5h 32m 00s 15h 34m 41s
+44° 56′ 51″ +40° 57′ 20″ -00° 17′ 57″ +26° 42′ 53″
1.89 – 1.98 2.12 – 3.39 2.14 – 2.26 2.21 – 2.32
0.09m  3.96d 1.27m  2.87d 0.12m  5.73d 0.11m  17.36d

The first line is the proper name of the star.
The second line is the Bayer designation.
The third line is right ascension (epoch 2000.0).
The fourth line is the declination (epoch 2000.0).
The fifth line is the range of visual magnitude.
The sixth line is the Δm and period in days.

Honorable mention: two eclipsing binaries, one along the Vela/Carina border and visible only from latitudes south of 35° N; the other experiences an eclipse almost as deep as Algol.

δ Vel Sheliak
Delta Velorum Beta Lyrae
8h 44m 42s 18h 50m 05s
-54° 42′ 32″ +33° 21′ 46″
1.96 – 2.36 3.25 – 4.36
0.40m 45.15d 1.11m 12.94d

And, here are four reasonably bright eclipsing binaries with deep eclipses, north of declination -30°:

V Sge
AC UMa
SY Cyg
UW Vir
V Sagittae AC Ursae Majoris SY Cygni UW Virginis
20h 20m 15s 8h 55m 54s 19h 46m 34s 13h 15m 21s
+21° 06′ 10″ +64° 58′ 14″ +32° 42′ 18″ -17° 28′ 17″
8.60 – 13.90 10.30 – 14.00 10.70 – 14.20 9.00 – 12.40
5.30m 0.51d 3.70m 6.85d 3.50m 6.01d 3.40m 1.81d

Some eclipsing binaries have very long periods between minima.  Epsilon Aurigae (27.1 years), Zeta Aurigae (2.7 years), and Zeta Tauri (132.97 days) are examples.

References
Catalogue of eclipsing variables. Version 2 (Avvakumova+, 2013)

Divided America

We have quite the dilemma.   In the broadest sense, we have two very different views of the role of government, science, economics, education, and world view.  There seems little hope of reconciliation until, I fear, some catastrophe of epic proportions befalls us.  Closed minds do not change easily.

There is more than enough blame for how we got to this point to spread around, but the media certainly deserves to be singled out as fueling divisiveness rather than letting the facts speak for themselves and building bridges of understanding.  Our TV nation hasn’t helped, either.

A recent example of this schism: President Barack Obama.  To many, he was one of the best presidents we have had in decades: intelligent, articulate, dignified, thoughtful, and hopeful.  To others, he was one of the worst presidents in history.  I happen to be in the former camp.  I predict that history will be kind to Barack Obama.  Very kind.

Presently, there is an uneasiness and anxiety across this country that during my 60 years in the U.S. is unprecedented.  Where do we go from here?  Increased civic engagement at all levels is crucial.  As is a media that educates rather than agitates.  Perhaps living separately, but in harmony, is the best way to demonstrate a better way to live, interact, and govern.

Many a time I have found myself wishing we could peacefully divide into two countries: one for the conservatives, and one for the liberals.  That way the conservatives could finally have the kind of laws and governance that they desire, and the liberals theirs.  But this is impractical because too many people would have to move.  What about at the state level?  Some states would be “liberal” states, and others “conservative”.  Well, we already have this to a small degree, but there are big differences in political persuasion even within a state.  Once again, too many people would have to relocate.

What about an expansion of the “sanctuary city” idea?  Though currently defined as safe havens for undocumented immigrants, sanctuary cities could become places where liberals and progressives could live and work largely free of conservative doctrine and laws.  One challenge to this approach, however, is that cities are largely subject to state and federal laws.

Finally, at the smallest level, one always has the opportunity to form or join an intentional community.  Though, once again, that community would be subject to state and federal laws, as well as local ones.  There is also the challenge of economies of scale.

I would like to live in a country where science and reason inform public decisions and laws rather than religion, dogma, superstition, and “fake news”.  A meritocracy where education and critical thinking is valued and encouraged for all citizens, regardless of their ability.  Where taxes are higher because they provide free education and universal health care, and less is spent on the instruments of war.  Where guns are a privilege requiring extensive training and vetting, not a right.  A post-capitalist society where government strongly regulates and at the same time supports businesses, and always strives to equalize economic opportunity for all citizens.  Utopian?  Perhaps.  I have no doubt that many of us could live and flourish in such a society.  The question is, will it work for everyone?

What’s That You Said…Both an Evening and a Morning Comet??

Sun-hugging Comet McNaught (C/2006 P1) was a wonderful sight ten years ago this month for the few who saw it in the northern hemisphere during January 2007.  It became visible to the unaided eye here in Wisconsin around January 4th, and brightened significantly during the next several days.  This unexpectedly bright comet reached a close perihelion (0.17 AU) on Friday, January 12, 2007 and became a spectacular sight from the southern hemisphere, but at that point our turn was over.

You may have heard (or witnessed) that Comet McNaught was visible in both the morning and evening twilight sky.  In fact, from SW Wisconsin the comet was visible both morning and evening from December 18th through January 9th.  How could that be?  It seems to defy common sense!

By looking at this video, you can see that Comet McNaught rose above and to the left of the Sun in the a.m. and set above and to the right of the Sun in the p.m.  Because the Comet-Sun line was nearly perpendicular to the ecliptic, as the sky rotated (due to the Earth’s rotation) during the day, Comet McNaught stayed “above” the Sun all day long, as shown in this video.  In the video, the blue/green line is the ecliptic, the plane of the Earth’s orbit.  Let’s use a clock analogy.  The Sun is at the center of the clock and Comet McNaught is at the end of the hour hand.  When Comet McNaught rises, it is at about the 10 o’clock position.  As the Sun rises and crosses the sky from SE to SW, the comet hour hand “moves” from the 10 o’clock position to the 2 o’clock position at sunset.  Though, of course, the clock itself is rotating clockwise, and the hour hand doesn’t move!

I’m not satisfied with this incomplete explanation, but at least you can see what is going on.  How good are you at visualizing spherical geometry in your head?  I’ll bet Stephen Hawking can do it.  If you can come up with a better description of this phenomenon—which will occur for any celestial object in the right position as seen from a certain range of latitudes— please share in a comment here!

Epoch and Equinox

We use the term epoch (of a given date) to refer to the actual measured coordinates of a star that takes into account precession, nutation, and proper motion. The term equinox means that the coordinates have been precessed to a given date, but that other factors affecting a star’s position have not been applied. So, equinox 2000.0 is not the same as epoch 2000.0.

Example: Barnard’s Star

Epoch 2000.0 coordinates: α = 17h 57m 48.49803s, δ = +4° 41′ 36.2072″ (the actual position of Barnard’s Star at 0h UT on January 1, 2000, accounting for precession, nutation, and proper motion)

Equinox 2017.1 coordinates: α = 17h 58m 39.20689s, δ = +4° 41′ 33.5614″ (coordinates have been precessed from epoch 2000.0 above to today’s date, but nutation and proper motion have not been applied)

Epoch 2017.1 coordinates: α = 17h 58m 37.85s, δ = +4° 44′ 37.8″ (the actual position of Barnard’s Star on January 19, 2017, accounting for precession, nutation, and proper motion)

Sometimes, the epochal coordinates are further adjusted to account for aberration and atmospheric refraction.  The latter tends to “lift” stars towards the zenith—the closer to the horizon the greater the lift.

Eugène Delporte and the Constellation Jigsaw

Belgian astronomer Eugène Joseph Delporte (1882-1955) discovered 66 asteroids from 1925 to 1942, but he is best remembered for determining the official boundaries of the 88 constellations, work he completed in 1928 and published in 1930.  The constellation boundaries have remained unchanged since then.

The International Astronomical Union (IAU), founded, incidentally, in Brussels, Belgium in 1919, established the number of constellations at 88—the same number, coincidentally, as the keys on a piano—in 1922 under the guidance of American astronomer Henry Norris Russell (1877-1957).  The IAU officially adopted Delporte’s constellation boundaries in 1928.

All the constellation boundaries lie along lines of constant right ascension and declination—as they existed in the year 1875. Why 1875 and not 1900, 1925, or 1930? American astronomer Benjamin Gould (1824-1896) had already drawn up southern constellation boundaries for epoch 1875, and Delporte built upon Gould’s earlier work.

As the direction of the Earth’s polar axis slowly changes due to precession, the constellation boundaries gradually tilt so that they no longer fall upon lines of constant right ascension and declination. Eventually, the tilt of the constellation boundaries will become large enough that the boundaries will probably be redefined to line up with the equatorial coordinate grid for some future epoch. When that happens, some borderline stars will move into an adjacent constellation. Even now, every year some stars change constellations because proper motion causes them to move across a constellation boundary. For faint stars, this happens frequently, but for bright stars such a constellation switch is exceedingly rare.

1892: First Auroral Photography

One hundred and twenty five years ago this month, on January 1, 1892, two Germans, astronomer & physicist Martin Brendel (1862-1939) and geographer & meteorologist Otto Baschin (1865-1933), arrived at Alta fjord near Bossekop in northern Norway to study the Northern Lights and conduct magnetic field measurements.  Their latitude was just shy of 70° N.  Brendel began photographing the aurora the next day, and his first extant photograph (the first ever) was taken on January 5, 1892.

Edward Emerson Barnard (1857-1923), incidentally, was to establish his reputation as an extraordinarily gifted astrophotographer later that same year when he began taking photographs of comets, clusters, nebulae (including galaxies), and the Milky Way using the 6-inch Crocker astrographic camera at the Lick Observatory.

The first extant photograph of the aurora, taken on January 5, 1892 by Martin Brendel
The first extant photograph of the aurora, taken on January 5, 1892 by Martin Brendel
Martin Brendel and his photograph of the aurora borealis on February 1, 1892 (below)
Martin Brendel and his photograph of the aurora borealis on February 1, 1892 (below)
Nordlichtdraperie - that's German for "northern lights curtains" - charming!
Nordlichtdraperie – that’s German for “northern lights curtains” – charming!

Otto Baschin (1865-1933)
Otto Baschin (1865-1933)

References
Catchers of the Light: A History of Astrophotography by Stefan Hughes

Earth’s Fickle Companions

A small number of asteroids are currently in a temporary 1:1 orbital resonance with the Earth in their orbit around the Sun.  Unlike the Moon, which is in a stable orbit around the Earth, these much tinier “co-orbital” objects are “just passin’ through.”

3753 Cruithne (1986 TO)
Came relatively close to the Earth each November from 1994 to 2015.  This will next happen around 2292.
Wiki  JPL  Orrery

85770 (1998 UP1)
Passes close to Venus, too.  This next happens in 2115.
Wiki  JPL  Orrery

54509 YORP (2000 PH5)
This tiny asteroid, perhaps 492 × 420 × 305 feet across, is a rapid rotator, turning around once every 12m10s. It is named after the YORP effect, as it provided the first observational evidence of that effect speeding up its spin rate.  It’s day will be half as long in only 600,000 years, and it may eventually speed up to one rotation every 20 seconds!
Wiki  JPL  Orrery

2002 AA29
This near-Earth object has an orbit that is very similar to the Earth’s, and even more circular, though it is inclined a full 10.7° to the ecliptic.  This asteroid is a good candidate for an automated sample-return mission and then human exploration because it is relatively close to the Earth and the amount of energy needed to visit 2002 AA29 and return to Earth is relatively small.
Wiki  JPL  Orrery

164207 (2004 GU9)
Currently, this asteroid never strays far from Earth, sometime leading it and sometimes following it.
Wiki  JPL  Orrery

277810 (2006 FV35)
This asteroid is another good candidate for human exploration.
Wiki  JPL  Orrery

2006 RH120
This extremely tiny object (just 7 to 10 feet across) spins more rapidly than any other object on our list: once every 2m45s!  It may even be an old rocket booster from the Apollo era, but recent evidence indicates it is a bona fide space rock.  It is currently leading the Earth in a very similar orbit.
Wiki  JPL  Orrery

2009 BD
We’ve been able to observe orbital changes in this tiny object due to the Sun’s radiation pressure.  It is currently trailing the Earth.
Wiki  JPL  Orrery

419624 (2010 SO16)
This asteroid was discovered using an infrared space telescope (WISE) and is in an unusually stable orbit that will change little during the next several hundred thousand years.  It is currently trailing the Earth.
Wiki  JPL  Orrery

2010 TK7
Also discovered using WISE, about 1,000 ft. across.  The only known Earth trojan asteroid.  It currently orbits the Sun about the L4 Lagrange point (leading the Earth by 60°).
Wiki  JPL  Orrery

2013 LX28
This asteroid has the highest orbital inclination (50°) of all the objects on our list.
Wiki  JPL  Orrery

2014 OL339
Serendipitously discovered while observing asteroid 2013 VQ4.
Wiki  JPL  Orrery

2015 SO2
Discovered from Slovenia.  Currently leading the Earth.
Wiki  JPL  Orrery

469219 (2016 HO3)
Currently, a quasi-satellite of the Earth.  Always remains within 38 to 100 lunar distances from the Earth as it orbits the Sun.  Leads, then follows, then leads again.  Quite a do-si-do!
Wiki  JPL  Orrery

Acknowledgements
The orrery videos for each asteroid were generated using the Jet Propulsion Laboratory’s incredible Orbit Diagram Java applet on their Small Body Database Browser web site (https://ssd.jpl.nasa.gov/sbdb.cgi), and captured using the equally incredible ScreenFlow software from Telestream (https://www.telestream.net/screenflow/).  Kudos to both organizations!

All is Well

Iowa County, Wisconsin needs a secular, four-part (soprano, alto, tenor, bass) choir for adult singers that meets regularly. When was the last time this area had something like that? I really miss singing in the tenor section of the Sul Ross State University Concert Choir under the outstanding leadership of Dr. Donald Freed.  Dr. Freed is quite a good choral composer, too.  What a privilege it was to sing a number of his choral works during my years in Alpine, Texas.

Fortunately, each year I have the opportunity to sing with the Lands’ End Choir here in Dodgeville each holiday season, under the capable leadership of Phil DeKok, conductor, and Dawn Lingard, accompanist.  It is an amateur choir, of course, and though we rehearse just once a week over the noon hour from late October through early December, it is always a joy to be singing again.

This year, my favorite piece by far was All is Well by Michael W. Smith and Wayne Kirkpatrick (words & music) in a beautiful arrangement by Lloyd Larson.  Here is Lloyd talking about the piece:

https://www.youtube.com/watch?v=c6wqL6Kt_L4

I get pretty emotional about music, and I had a hard time getting through this particular piece without getting a little choked up and teary eyed.

The son of one of our choir members, Bev Adams-Sugden, recorded our performance of this work in Bldg. 5 over the noon hour on Tuesday, December 20, 2016.  Enjoy!

http://skythisweek.info/Lands End Choir 201612 B5 All is Well.mp4

 

Avoid Blue-Rich LED Lighting

As Dodgeville (and many other towns and cities) are planning to replace their streetlights with LED luminaires, it is imperative that we use LEDs with a CCT (correlated color temperature) of 3000 K or less (Jin et al. 2015).  This is a “warm” white light (similar to incandescent) rather than the “cold” blue-rich light often seen with LEDs.  Outdoor LED luminaires often come in at least three “flavors”: 3000K, 4000K, and 5000K.  For example, American Electric Lighting’s Autobahn Series.  5000K luminaires provide the bluest light, and should be avoided at all costs.  Of these three, 3000K would be best, and if 2700K is offered, use that.

Why does this matter?  On June 14, 2016, the American Medical Association issued guidance on this subject.

High-intensity LED lighting designs emit a large amount of blue light that appears white to the naked eye and create worse nighttime glare than conventional lighting.  Discomfort and disability from intense, blue-rich LED lighting can decrease visual acuity and safety, resulting in concerns and creating a road hazard.

The detrimental effects of high-intensity LED lighting are not limited to humans.  Excessive outdoor lighting disrupts many species that need a dark environment.  For instance, poorly designed LED lighting disorients some bird, insect, turtle and fish species, and U.S. national parks have adopted optimal lighting designs and practices that minimize the effects of light pollution on the environment.

Recognizing the detrimental effects of poorly-designed, high-intensity LED lighting, the AMA encourages communities to minimize and control blue-rich environmental lighting by using the lowest emission of blue light possible to reduce glare.  The AMA recommends an intensity threshold for optimal LED lighting that minimizes blue-rich light.  The AMA also recommends all LED lighting should be properly shielded to minimize glare and detrimental human health and environmental effects, and consideration should be given to utilize the ability of LED lighting to be dimmed for off-peak time periods.

Incidentally, for your residential lighting needs, a good local source for LED bulbs that are not blue-rich is Madison Lighting.  They have many LED bulbs in both 3000 K and 2700 K. I use 2700K bulbs exclusively in my home, and the warm white light they provide is an excellent replacement for incandescent and compact fluorescent bulbs.  Never purchase LED lighting without knowing the color temperature of the lights.

If you’re skeptical that the color temperature of LEDs is an important issue, I suggest you purchase a 2700K bulb and a 4000K or 5000K bulb with the same output lumens and compare them in your home.  I believe that you will much prefer the 2700K lighting.  If 2700K lighting is best for your home, then why should it not be best for outdoor lighting as well?

Besides, most streetlighting is currently high pressure sodium (HPS), which is inherently non-blue-rich.  You will find that 2700K LED lights offers better color rendering than HPS without the need to go to even bluer lights.

If you have ever been irritated at night by an oncoming vehicle with those awful “blue” headlights, you’ve experienced firsthand why blue-rich light in our nighttime environment must be minimized.

Why are 4000K and 5000K LED lights so prevalent?  They are easier and cheaper to manufacture, but with increased demand of 2700K and 3000K LED lights, economies of scale will reduce their cost, which today are generally slightly higher than blue-rich LEDs.

Now, a bit more about why blue light at night can be detrimental to human health, and the primary reason why the AMA issued a guidance on this subject.

In addition to image-forming rods and cones, there exist non-image-forming retinal cells in the human eye called intrinsically photosensitive retinal ganglion cells (ipRGCs) that help regulate our circadian rhythms.  Studies have shown that blue light is far more disruptive to our circadian rhythms than redder light (Lockley et al. 2003).

Now, on to the environment.  Using a clever technique that compared sky brightness at several locations on several nights both with and without snow cover, Fabio Falchi (Falchi 2011) determined that at least 60% of light going up into the night sky is direct waste lighting, and 40% or less is reflected light.  This is as good an argument as any that we still have a long way to go towards using only full-cutoff luminaires that do not produce any direct uplight.  Blue light scatters much more in the night sky than red light, and this is due to Rayleigh scattering which tells us that the amount of scattering is proportional to the inverse of the wavelength of light to the fourth power, σs ∝ 1 / λ4.  This also explains why the daytime sky is blue.

Bluer wavelengths of light thus increase artificial sky glow to a much greater extent than redder wavelengths do.  Not only is an increase in blue light bad for astronomy, but its impact on the natural world is likely to be adverse as well.

Falchi recommends a total ban of wavelengths shorter than 540 nm for nighttime lighting, both outdoor and indoor.  He goes on to say that, at the very least, no more light shortward of 540 nm should be allowed than that currently emitted by high pressure sodium lamps, lumen for lumen.

References
Falchi, F. 2011, MNRAS, 412, 33
Falchi, F. 2016, The World Atlas of Light Pollution, p. 44
Jin, H., Jin, S., Chen, L., et al. 2015, IEEE Photonics Journal. 7(6), 1-9
Lockley, S. W., et al. 2003, J Clin Endocrinol Metab. 88(9), 45025

Polarization of Starlight

The space between stars is not a perfect vacuum. It contains gas molecules and dust grains, although they are few and far between by any terrestrial standard. In the presence of a magnetic field, many types of interstellar dust grains line up in a way that is reminiscent of iron filings near a bar magnet. When light from a star passes through a region of space with magnetically-aligned dust grains (though in this case the short axis of the dust grains aligns with the local magnetic field), light with the electric field vector perpendicular to the long axis of the grains is less likely to be absorbed by the grains than light whose electric field vector is parallel to the long axis of the grains. This causes the light passing through such regions of space to become slightly polarized, and the polarization of starlight is something we can measure easily here on Earth. In this way, the strength and orientation of invisible interstellar or circumstellar magnetic fields can be determined at a distance.

Various astrophysical processes result in polarized electromagnetic radiation.  The differential absorption already mentioned polarizes the light from all stars to one degree or another.  Only the Sun—which is vastly nearer—offers us almost completely unpolarized light. Scattering of light off of interstellar clouds and planetary surfaces also results in polarization.  Finally, both synchrotron and cyclotron emission produce a characteristic polarization.

The polarization of starlight can be measured by the use of a polarimeter attached to the telescope.  Unlike standard photometry, polarization is simpler to measure with ground-based telescopes because the measurements are relative rather than absolute and, under normal circumstances, the Earth’s atmosphere does not affect the polarization state of incoming light.  Care must be taken, however, to ensure that the telescope itself does not create instrumental polarization due to oblique reflections.  Placing the polarimeter at the unfolded Cassegrain focus is one desirable configuration (Hough 2006).

References
Hough, J. 2006, A&G, 47, 3.31