Saturn at Eastern Quadrature

Wednesday evening, September 13, 2017, at 9:59 p.m. CDT, Saturn reaches eastern quadrature as Saturn, Earth, and Sun form a right triangle.  Eastern quadrature is so named as Saturn is 90° east of the Sun.  This is the time when Saturn presents to us its most gibbous phase.  Even so, Saturn will be 99.7% illuminated due to its great distance from us.

A more noticeable effect will be the shadow of Saturn on its rings, a phenomenon best seen at eastern or western quadrature.

Saturn will only be 12° above our horizon in SW Wisconsin at the exact moment of eastern quadrature Wednesday evening.  Earlier that evening, Saturn crosses the celestial meridian at 6:51 p.m.—22 minutes before sunset.  If it weren’t for daylight, that would be the best time to observe Saturn: when it is highest in the sky and we are seeing it through the least amount of atmosphere.  If you have a telescope equipped with a polarizing filter, you can significantly darken the blue sky background around Saturn since the planet will be exactly 90° away from the Sun, where the scattered sunlight is most highly polarized.  Rotate the polarizer until the sky is darkest around Saturn.

Speaking of Saturn, the Cassini mission will come to a bittersweet end on Friday, September 15 around 5:31 a.m. CDT when the storied spacecraft, which has been orbiting Saturn since June 30, 2004, will have plunged deep enough into Saturn’s atmosphere that it is no longer able to point its high gain antenna towards Earth.  Soon after that, Cassini will burn up in Saturn’s massive atmosphere.  We on Earth will not receive Cassini’s last radio transmission until 1h23m later—at around 6:54 a.m. CDT.

Emily Lakdawalla, who is arguably the best planetary science journalist in the world these days, includes the visual timeline of Cassini’s demise shown below and in her recent blog entry, “What to expect during Cassini’s final hours”.

Also, on Wednesday evening, don’t miss NOVA: Death Dive to Saturn, which will air on Wisconsin Public Television’s flagship channel at 8:00 p.m.

It may be a while before we visit ringed Saturn and its retinue of moons again.  But further exploration of Titan and Enceladus is certain to feature prominently in humankind’s next mission to Saturn.  Hopefully, that will be soon.

Nearest Neutron Star

So far as we know, RX J1856.5-3754 is the neutron star closest to our solar system.  This radio-quiet isolated neutron star can be found between 352 and 437 ly from our solar system, with its most likely distance being 401 ly.  Directionally, it is located within the constellation Corona Australis, near the topside of the CrA circlet, just below the constellation Sagittarius.  Its coordinates are:

α2000 = 18h 56m 35.11s, δ2000 = -37° 54′ 30.5″.

RX J1856.5-3754 was formed in a supernova explosion about 420,000 years ago.  Today, this tiny 1.5 M star about 15 miles across has a surface temperature of 1.6 million K and shines in visible light very feebly with an apparent visual magnitude of only 25.5.  Its surface is so hot that its thermal emission is brightest in the soft X-ray part of the electromagnetic spectrum; this is how it was discovered in 1992.

Like all neutron stars, RX J1856.5-3754 has a very intense surface magnetic field (B ≈ 1013 G) which causes the electromagnetic radiation leaving it to exhibit a strong linear polarization.  In the presence of such a strong magnetic field, the “empty” space through which the light travels behaves like a prism, linearly polarizing the outgoing light through a process known as vacuum birefringence.

An active area of neutron star research currently is a precise determination of their diameters.  We do not yet know whether the extremely dense central regions of these stars contain neutrons, or an exotic form of matter such as a quark soup, hyperons, a Bose-Einstein condensate, or something else.  Knowing the exact size and mass of a neutron star will allow us to infer what type of matter must exist in its interior.  The majority of neutron stars are pulsars with active magnetospheres that make it difficult for us to see down to the surface.  More “quiet” neutron stars such as RX J1856.5-3754 are the best candidates for precise size measurements of the neutron star itself.  An accuracy of at least ± 1 mile is needed to begin to distinguish between the various models.

References
Mignani, R.P., Testa V., González Caniulef, D., et al. 2017, MNRAS 465, 1, 1
Özel, F., Sky & Telescope, July 2017, pp. 16-21
Yoneyama, T., Hayashida, K., Nakajima, H., Inoue, S., Tsunemi, H. 2017
[https://arxiv.org/abs/1703.05995]

Dark Sky Community Prospectus

  1. Rationale
    1. A small community (hereafter referred to as a dark sky community) can thrive without the need for streetlights or any other dusk-to-dawn lighting
    2. A dark sky community would appeal to people who value the night sky and a natural nighttime environment
    3. It will probably be many years before the majority of people will accept life without dusk-to-dawn outdoor lighting
    4. A dark sky community must be located far enough away from neighboring communities and other significant light sources that the night sky and nighttime environment will not be adversely affected, either now or in the foreseeable future
    5. It is better to live in community than in isolation
  2. Community Attributes
    1. A dark sky community should be multi-generational, but since rural employment options are limited, moving to a dark sky community may be easier for retired or semi-retired folks
    2. A dark sky community should be affordable, with a variety of housing options (units that can be rented, for example)
    3. An observatory commons area should be developed for observing and include more than one observatory for use by members of the community
    4. The dark sky community should engage in an ambitious educational outreach program, including the operation of an astronomy resort and astro-tourism business
    5. The business end of the community should be a nonprofit corporation or cooperative that operates the astronomy resort and rental properties
    6. The community should share resources as much as possible, freeing residents from the financial burden of having to individually own everything they need or use
    7. The dark sky community should engage in an ambitious program of collaborative astronomical research and data collection, working collaboratively within the community and with amateur and professional astronomers outside the community
  3. Community Location
    1. The most affordable option would be to “convert” an existing rural subdivision or small town into a dark sky community, current residents willing, of course!
    2. The best location for a dark sky community would be within, or adjacent to, a protected natural area such as a state or national park
    3. Recognizing that there would be distinct advantages in siting a dark sky community reasonably close to a town or city with medical facilities, it would be best (for astronomical reasons) for the dark sky community to be located southeast or southwest of the larger community
  4. Philosophy
    1. In an age of technological wonders such as digital imaging, computer-controlled telescopes, remote observing, and space astronomy, we recognize that there is still value in the experience of “firsthand astronomy” both for ourselves and our guests

For greater detail, see my astronomy village proposal for Mirador Astronomy Village.  I welcome your comments and ideas here.

Identifying Distant Light Pollution Sources

Ten years ago, I lived within easy walking distance of the south edge of Dodgeville, and on one starry evening, I walked to a favorite hilltop with a good view of the sky just south of town.  To my surprise and displeasure, I noticed a bright light dome in the southeast I had never noticed before.  Where was that light coming from?

Fortuitously, the bright star Antares was at that moment very close to the horizon, and right above the offending light dome!  I noted the time: 10:25 p.m. CDT on 15 May 2007.  And the observing location: 42° 57′ 06.4″ N, 90° 08′ 16.9″ W.

After getting home, I started up the Voyager planetarium software on my Macintosh, set the date and time to the observation time, and the observing location listed above.  I found that at that moment, Antares was at an azimuth of 134.2°.

Now, grabbing a protractor and a Wisconsin state map, I quickly determined that the most likely city along the 134.2° azimuth line from Dodgeville was Monroe, Wisconsin.  Though quite some distance away, could this have been the source of the light dome I saw?

Using a great circle calculation program on the internet and the known geographic coordinates (latitude, longitude) for the two locations using Wikipedia, I determined that Monroe is at bearing (azimuth) 133.5 from my observing location near Dodgeville at a distance of 35 miles.  This matched my star-determined azimuth quite well.

Was there an outdoor athletic event going on in Monroe at that time to cause so much light pollution?

Could the light dome possibly have been coming from Rockford, Illinois?  Even though Rockford’s bearing of 131.1° makes it a suspect, its line-of-sight distance of 71 miles makes this extremely unlikely.

Renters and Flood Plains

The catastrophic flooding in Houston brings back terrible memories of  the flood I experienced during the early morning hours of Tuesday, May 26, 2015 when my apartment in the Meyerland area of Houston took on three feet of water and I lost most of my belongings including my car.  There was no warning that the Brays Bayou would leave its banks that night.  My Meyergrove apartment has flooded again twice since I left Houston in September 2015: once on April 18, 2016, and again this weekend.  This frequency of flooding is unprecedented in that area of Houston.

Flood scene from 2nd floor balcony of my apartment building during morning twilight, May 26, 2015.

Everyone with a ground floor apartment lost most of their belongings in my apartment complex during the Memorial Day Weekend 2015 flood.  No one I talked to had flood insurance, and everyone had renter’s insurance that did not cover their flood damage, so they lost a lot.

Brays Bayou from the 2nd floor balcony of my apartment building, morning of May 26, 2015.

Which brings up an important point.  Why are there not laws to require lessors to disclose to renters when the apartment or house they are renting lies in a flood plain?  If the lessor has flood insurance on their property, then they should be required to inform their tenants of that fact and clearly communicate that the tenant should purchase flood insurance in addition to their renter’s insurance.  After all, when you are buying a house, you cannot get a home loan unless you purchase flood insurance if you are living in a flood-prone area.  Why do not renters have the same protection?

Perhaps there are other areas of the country where landlords have to disclose to their renters if they will be living in a flood plain, but there appears to be no such protection for renters in the state of Texas.

 

 

Total Solar Eclipse of August 21, 2017

Sunday morning our eclipse party was SE of Grand Island, Nebraska, but weather prospects were not good for Nebraska on eclipse Monday so we decided to make the long trek to Wyoming.  Fortunately, my friends John & Nancy Wunderlin had invited us to their eclipse-watching site in Glendo State Park near Glendo, Wyoming.  I brought along a Coronado 70 mm Hα telescope, a Meade 8-inch Schmidt-Cassegrain with a white-light full-aperture solar filter from Thousand Oaks Optical, and Fujinon 16 x 70 binoculars, also with Thousand Oaks solar filters, mounted on a heavy-duty Orion binocular mount.  While John took pictures of the eclipse, I was busy showing a large group of eclipse watchers views of the partial eclipse before and after totality.  During totality, we ignored those instruments and viewed the eclipse using our unaided eyes and unfiltered 7 x 50 binoculars.

Photograph by John Wunderlin, Glendo State Park, Wyoming, August 21, 2017

We had perfect conditions for this eclipse: a very clear sky, low humidity, and reasonably high elevation (~4,700 ft.).  This total eclipse was for me more impressive than the only other total solar eclipse I’ve seen: February 26, 1979 near Riverton, Manitoba.  It is difficult to describe in words or even photographs the beauty of this event!  Definitely worth driving a rented Cruise America RV 2,200 miles and spending three nights in the RV—the night before and the night after the eclipse without hookups, the latter in the Wal Mart parking lot in Chadron, Nebraska.  Besides its size, an RV is more challenging to drive than a car or minivan—especially if it is windy—and every time a semi passes you get buffeted.  Both hands on the wheel!  And then there was the 6+ hours we spent driving from Glendo State Park to Glendo and up WY 319 up to US 18/20—a distance of only about 20 miles—after the eclipse.  Traffic was at a standstill most of that time and we really appreciated having the on-board restroom.  Despite a huge number of people heading home after the eclipse, it was the most civilized group you could imagine under the circumstances.  The kind of people who make the effort to put themselves into the path of totality are probably more intellectually curious and courteous than your average American.  We were all still basking in the afterglow of totality, I’m sure.

There are so many aspects of the eclipse to describe, but I’ll focus on just a few here.  First, I had the equipment all set up before first contact, which is the point at which the disc of the Moon first touches the disc of the Sun, and the partial eclipse begins.  Likewise, none of the equipment came down until after last contact, when the Sun once again became completely uncovered.  We watched the entire eclipse intently from beginning to end.  Though I was busy tending to the two telescopes and binoculars and answering eclipse questions for the wonderful throng of kids and adults who joined us, I did have a chance from time to time to look up at the Sun with the eclipse glasses we all had and frequently used.  Paul Martsching saw to it that no one went without their own pair of eclipse glasses.

The pre- and post-totality Sun offered up views of a surprising number of sunspots, some very small, and it was interesting to watch them being covered and later uncovered by the Moon.  One of the irregular sunspot groups reminded me of a monkey looking backwards over its shoulder.

As totality began, it suddenly got darker, and we marveled at the handful of planets and stars we could see.  Venus was especially bright.  The prominences were a beautiful shade of red and very bright, even to the unaided eye, and in 7×50 binoculars the view was stunning!  I have seen many photographs of totality, but no photograph can compare to the view you get with the unaided eye or through binoculars.  You just have to be there to experience it first hand.

After totality was over and while the Sun was still mostly covered by the Moon, the solar prominences in the Coronado Hα telescope were incredibly bright, brilliantly red, larger and much easier to see than they ever are when viewing the uneclipsed Sun.  Wow!

When the Sun was about a third to a half uncovered (unfortunately, I didn’t note the time because I was so busy tending to the instruments, listening to eclipse impressions, and answering questions), I noticed a very strange phenomenon in the Meade 8-inch telescope, where the filtered Sun was magnified enough to mostly fill the field of view.  A round black bead—a little larger than the largest sunspot—moved along the southwest limb of the Sun from about the 7 o’clock to the 9 o’clock position relative to the cusps.  At first glance, I thought it might be a bird or an airplane.  The speed seemed about right for a bird, in front of the Sun between one and two seconds, but this black circle moved along the solar limb instead of transecting the Sun!  Then, just a couple of seconds later, another black bead appeared, moved along the solar limb, and disappeared precisely as the first one had.  That was it.  I saw no more.  Was this some sort of unusual atmospheric phenomenon?  Whatever it was, it definitely wasn’t floaters.

As Shakespeare wrote around the turn of the 17th century, there are more things in heaven and earth than are dreamt of in our philosophy.  A total solar eclipse certainly confirms that notion.

Next Generation Beginner’s Telescope

Let’s start with an 8″ f/4.5 Newtonian in an alt-az Dobsonian mount (remember the wonderful Coulter Odyssey?).  Give it “push to” rather than go-to capability, and motorized tracking.  The next generation part? Have a built-in imaging camera that can be moved in and out of the light path and the on-board smarts to look at the relationships between the stars in the image to determine where the telescope is pointing.  Think of the enjoyment a beginner (or experienced astronomer, for that matter) would have pointing the telescope around the sky, finding an object of interest, and then turning a knob to take an image and having the telescope tell them what they’re pointed at!  Or, alternatively, once the telescope knows where it is pointing using the imaging technique, it could show the observer how much to push in altitude and azimuth to reach a known object of interest.  Oh, and a built-in laser collimator would be nice, too.

As a professional computer programmer, I would love to have the opportunity to write the software for such a system, and meeting the challenge of making this telescope far more “beginner friendly” than the current generation of go-to telescopes.

Satellite Crossings 2016-2017

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but since October 4, 1957 another “species” of sky vermin made their debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my ~¼° field of view.

I’ve put together a video montage of satellites I’ve recorded between December 14, 2016 and August 5, 2017.  The component events are presented chronologically as follows:

UT Date
12-14-2016
1-15-2017
5-5-2017
6-7-2017
6-19-2017
7-25-2017 (2 satellites)
8-5-2017

Target Star
UCAC4 538-7253
Tycho 586-1051-1
Tycho 1422-911-1
Tycho 4997-136-1
Tycho 6799-309-1
Tycho 666-190-1
UCAC4 548-7392

Asteroid
2485 Scheffler
19807 (2000 SE16)
71612 (2000 EH12)
11133 Kumotori
68112 (2000 YC143)
491 Carina
151 Abundantia


In all cases, the asteroids were too faint to be recorded.  And, in all cases, the target star was not occulted by the asteroid (a miss).  In the final event, the satellite passed right over the target star (9:40:11.679 UT) during the period of time the event would be most likely to occur (9:40:10 ± 3 s)!  Fortunately, the seeing disc of the target star was never completely obliterated by the passing satellite, so I was able to determine unequivocally that the asteroid missed passing in front of the star from my location on Spaceship Earth.

Here’s a graph of the brightness of UCAC4 548-7392 during the last video clip.  You can definitely see the close appulse of the satellite with the star!

In general, the slower the satellite is moving across the field, the higher is its orbit around the Earth.  One must also consider how much of the satellite’s orbital motion is along your line of sight to the satellite.  In the following montage of two video clips, the first satellite is very slow moving and thus most likely in a very high orbit.  The second video clip shows a satellite that is quite faint.  Again, the asteroids are too faint to be recorded and no asteroid occultation event occurred.

UT Date
5-14-2017
6-8-2017

Target Star
Tycho 5011-133-1
Tycho 5719-308-1

Asteroid
190471 (2000 DG27)
321656 (2010 BM90)

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Yellow LED Astronomy Flashlights

Back when I had my astronomy-friendly outdoor lighting business, I used to sell yellow-LED flashlights that I bought from a fellow who made them in California.

The Houston flood Memorial Day weekend 2015 wiped out the remaining inventory I had and, sadly, these wonderful flashlights are no longer available.

It is not rocket science.  You need to start with a well-made flashlight, replace the regular bulb with a yellow LED and the appropriate current-limiting resistor, and voila!

Yellow may be better than red.  See the article by Robert Dick, “Is Red Light Really Best?”, in the June 2016 issue of Sky & Telescope.

There’s a great business opportunity here.  It wouldn’t take much to make a better astronomy flashlight than what Orion and others sell.  Besides, I have found these yellow-LED flashlights to be most useful for moving around the house after bedtime (such as a bathroom trip) to avoid being exposed to any bright light at night which would affect your night vision and even your circadian rhythm.

If you know of any astronomy-friendly yellow LED flashlights or would like to manufacture some, please post a comment here or contact me directly.

Eclipse Weather – IL, MO, KS, NE, and WY

I’ve written a SAS program that pulls National Weather Service zone forecasts for the 49 counties along the eclipse centerline in Illinois, Missouri, Kansas, Nebraska, and Wyoming.  During the week leading up to the Monday, August 21, 2017 total solar eclipse, I will be frequently updating this page:

Eclipse Weather

I hope you will find this weather resource useful as you plan for a cloud-free view of this wondrous event.  Clear skies!