Are any of you nearing retirement (as I am) or already retired who might be interested in moving to an astronomy-oriented retirement community? If you are, I encourage you to join the moderated Groups.io discussion group Dark-Sky Communities at
I am working to establish such a community and would value your input and assistance. That work involves extensive research, networking, writing articles in various publications to reach a wider audience, finding a suitable developer, and seeking benefactors.
Some characteristics of the community I envision include:
Rural location with a dark night sky, but not too far from a city with decent medical facilities, preferably to the northeast or northwest;
Location with an abundance of clear nights and mild winters, probably in Arizona, New Mexico, or West Texas;
Lighting within the community that does not interfere with astronomical activities, strictly enforced;
Community is owned and operated by a benefit corporation or cooperative that will rent a house or apartment to each resident;
Observatories will be available for rental by interested residents who will equip them;
Pro-am collaborative research opportunities will be developed and nurtured;
A community observatory and a public observatory for astronomy outreach will be constructed and maintained;
Lodging will be available for visitors and guests;
There will be opportunities for on-site income operating and maintaining the community or, alternatively, a reduction in monthly rental fees.
Many of us have spent a significant amount of time and energy over the years trying to rein in light pollution in our respective communities and in the wider world, with varying degrees of success. Those efforts should continue, but the grim reality is that light pollution is continuing to get worse almost everywhere.
The opportunity to live in a community of varied interests but with a common appreciation for the night sky and a natural nighttime environment will appeal to many of us. Furthermore, a dark-sky community will afford us opportunities to show the world at large a better way to live.
Traditionally, in the United States at least, if one wants to live under a dark and starry night sky, your only options are to purchase land and build a house on it, or purchase an existing rural home. Not only is buying and maintaining rural real estate unaffordable or impractical for many, many would prefer to live in a rural community, provided that the night sky and nighttime environment are vigorously protected. Rental will also make it easier to move into and out of the community as circumstances change.
Has anyone else noticed how Alliant Energy is gradually replacing our orangish-white-light streetlights with bluish-white-light ones? The orangish-white-light streetlights are high-pressure sodium (HPS) with a correlated color temperature (CCT) of 1900K, whereas the bluish-white-light streetlights that are replacing them are LED with a CCT of 4000K, and, most notably, they are two and a half times as bright.
Even though I have written to both Alliant Energy and the City of Dodgeville, nothing has changed.
My questions, which are still unanswered:
What is the justification for increasing the streetlighting illumination level by two and a half times over what it has been for decades?
Why are we going from 1900K to 4000K (cold white), when 2700K or 3000K (warm white) is readily available and being used in many communities in the U.S. and Canada?
This same transformation is happening in Mineral Point, and probably many other communities in SW Wisconsin as well.
Is anyone else noticing how this is profoundly changing the rural character of our nighttime environment? Is anyone else concerned about this? The increase in glare and light trespass onto neighboring properties from these new LED lights is quite noticeable to me, even though they are nominally full-cutoff. Why? They are too bright, and too blue.
If anyone locally is reading Cosmic Reflections (and sometimes I wonder if anyone is…), and if you have noticed and are alarmed by these streetlighting changes, please contact me on blog or off blog (oesper at mac.com) and let’s meet and discuss a plan of action. Something needs to be done before it is too late and we are stuck with this very negative change to our nighttime environment.
Back in 2006, I started a Yahoo! Group called DarkSkyCommunities. My goal was to provide a forum for astronomy enthusiasts and other like-minded individuals to discuss living where you’d have a star-filled night sky and never have to worry about streetlights or neighbor’s lights. Everyone else in the community would value the night sky and a natural nighttime environment as you do.
My approach with DarkSkyCommunities was not to be a heavy-handed moderator. I approved new members but after that, members were free to post (within reason) anything they wanted to. In that sense, it worked pretty well and there were very few postings I ever had to take down.
Unfortunately, astronomers know next to nothing about intentional community and intentional communitarians know next to nothing about astronomy, so the group drifted far from my original intent to a general discussion about light pollution, with “what’s wrong with the IDA” being a surprisingly popular topic for discussion. Eventually, though, a small number of individuals with a chip on their shoulder or an axe to grind became the most frequent posters, and that sort of poisoned the group.
So, I’d like to introduce to you DarkSkyCommunities 2.0: a Google group called Dark-Sky Communities. Here’s the description on the landing page:
Dark-Sky Communities is a discussion group for the development and nurturing of intentional communities where the night sky and the nighttime environment are valued and protected. The emphasis is on affordable, sustainable dark-sky communities where those of modest financial means can live, work, and retire. This group is moderated to keep the focus on intentional communities that are astronomy-friendly.
This time around I am going to approve (or disapprove) the messages posted to the group so that we stay on the topic of astronomy-friendly intentional communities. If you have an interest in this topic, please join!
Light pollution, despite our best efforts, is getting worse almost everywhere. LED lighting which had (and still has) so much promise is generally resulting in more lights, brighter lights, and bluer lights—not the direction we want to head.
Someday, I would like to live in a place where I can walk a few feet beyond my door, set down a lawn chair, and watch a meteor shower without being assaulted by streetlights, insecurity lights, glare, and skyglow. Is that too much to ask?
Would you like to live in a place like that, too? Let’s make it happen!
I attended the 234th meeting of the American Astronomical Society (AAS), held in St. Louis, Missouri, June 9-13, 2019. Here are some highlights from that meeting.
Day 1 – Monday, June 10, 2019
Research Notes of the AAS is a non-peer-reviewed, indexed and secure record of works in progress, comments and clarifications, null results, or timely reports of observations in astronomy and astrophysics. RNAAS.
The Bulletin of the American Astronomical Society is the publication for science meeting abstracts, obituaries, commentary articles about the discipline, and white papers of broad interest to our community. BAAS.
We still have many unanswered questions about galaxy formation. The rate of star formation in galaxies and central black hole accretion activity was highest between 10 and 11 billion years ago. This corresponds to redshift z around 2 to 3, referred to as “cosmic high noon”. This is the ideal epoch for us to answer our questions about galaxy formation. Near-infrared spectroscopy is important to the study of galaxies during this epoch, and we are quite limited in what we can do from terrestrial observatories. Space based telescopes are needed, and the James Webb Space Telescope (JWST) will be key.
Galaxies are not closed boxes. We need to understand how inflows and outflows affect their evolution (“galactic metabolism”).
There are five international space treaties, with the Outer Space Treaty of 1967 being the first and most important. The United States has signed four of the five treaties. The Moon Agreement of 1979 which states that no entity can own any part of the Moon does not include the United States as one of the signatories.
U.S. Code 51303, adopted in 2015, identifies asteroid resource and space resource rights, and states that “A United States citizen engaged in commercial recovery of an asteroid resource or a space resource under this chapter shall be entitled to any asteroid resource or space resource obtained, including to possess, own, transport, use, and sell the asteroid resource or space resource obtained in accordance with applicable law, including the international obligations of the United States.”
So, unfortunately, U.S. law does allow a commercial entity to own an asteroid, but you have to get there first before you can claim it. The large metallic asteroid 16 Psyche is highly valuable and will probably be owned by some corporation in the not-too-distant future.
Space law often relies upon maritime law as a model.
Astronomer Vayu Gokhale from Truman State University gave an interesting iPoster Plus presentation on how he and his students are operating three automated and continuous zenithal sky brightness measurement stations using narrow-field Sky Quality Meters (SQMs) from Unihedron. Even measurements when it is cloudy are of value, as clouds reflect light pollution back towards the ground. Adding cloud type and height would allow us to make better use of cloudy-night sky brightness measurements. In a light-polluted area, the darkest place is the zenith, and clouds make the sky brighter. In an un-light-polluted area, the darkest place is the horizon, and clouds make the sky darker.
A number of precision radial velocity instruments for exoplanet discovery and characterization will begin operations soon or are already in operation: NEID, HARPS, ESPRESSO, EXPRES, and iLocater, to name a few.
Dark matter: clumps together under gravity, does not emit, reflect, or absorb electromagnetic radiation, and does not interact with normal matter in any way that causes the normal matter to emit, reflect, or absorb electromagnetic radiation. The ratio between dark matter and normal (baryonic matter) in our universe is 5.36 ± 0.05 (Planck 2018).
What is dark matter? It could be a new particle. If so, can we detect its non-gravitational interactions? It could be macroscopic objects, perhaps primordial black holes. Or, it could be a mixture of both. Another possibility is that a modification to the laws of gravitation will be needed to mimic the effects of dark matter.
How “dark” is dark matter? Does it interact at all (besides gravitationally)? Can dark matter annihilate or decay? Even if dark matter started hot, it cools down rapidly as the universe expands.
Primordial black holes could have masses ranging anywhere between 10-16 and 1010 solar masses. LIGO is possibility sensitive to colliding primordial black holes with masses in the range of a few to a few hundred solar masses. Primordial black holes are a fascinating dark matter candidate, with broad phenomenology.
The Cosmic Microwave Background (CMB) is a nearly perfect blackbody with distortions < 1 part in 10,000. What this tells us is that nothing dramatically heated or cooled photons after 2 months after the Big Bang. Anisotropies are variances in the CMB temperature, and the angular power spectrum is variance of CMB temperature as a function of angular scale. CMB anisotropies are very sensitive to the ionization history of the universe. How the universe recombined plays a key role in CMB anisotropies.
Hydrogen: not such a simple atom.
The CMB is polarized. The polarization is caused by Mie scattering of photons.
At the NASA Town Hall, we learned about current and future missions: TESS, SPHEREx, HabEx, LUVOIR, Lynx, Origins Space Telescope (OST).
The highest image rate of standard CCD and CMOS video cameras for asteroid occultation work is 30 frames (60 fields) per second, providing time resolution of 0.017 seconds per field. Adaptive optics and autoguider imaging devices often have a higher sampling rate, and such a camera could perhaps be easily modified to be used for occultation work. A time-inserter would need to be added to the camera (either on-board or GPS-based), and improvements in quantum efficiency (because of the shorter exposures) would benefit from newer imaging technologies such as a Geiger-mode avalanche photodiode (APD); or the Single-photon avalanche detector (SPAD), which are frequently used in chemistry.
Gregory Simonian, graduate student at Ohio State, presented “Double Trouble: Biases Caused by Binaries in Large Stellar Rotation datasets”. The Kepler data yielded 34,030 rotation periods through starspot variability. However, the rapid rotators are mostly binaries. In the Kepler dataset, many rapid rotators have a spin period of the stars equal to the orbital period of the binary. These eclipsing binaries, also known as photometric binaries because they are detected through changes in brightness during eclipses and transits, need to be treated separately in stellar rotation datasets.
Granulation was discovered by William Herschel in 1801 and are vertical flows in the solar photosphere on the order of 1000 m/s, and 1000 km horizontal scale. Supergranulation (Hart 1954, Leighton et al. 1962) are horizontal motions in the photosphere of 300 to 500 m/s with a horizontal scale on the order of 30,000 km.
The amplitude of oscillations in red giants increase dramatically with age.
We’ve never observed the helium flash event in a red giant star, though models predict that it must occur. It is very brief and would be difficult to detect observationally.
Brad Schaefer, Professor Emeritus at Louisiana State University, gave a talk on “Predictions for Upcoming Recurrent Nova Eruptions”. Typically, recurrent novae have about a 30% variation in eruptive timescales, so predicting the next eruption is not trivial. Due to the solar gap (when the object is too close to the Sun to observe on or near the Earth), we are obviously missing some eruptions. However, orbital period changes (O-C curve) can tell us about an eruption we missed. U Sco and T CrB are well-known examples of recurrent novae. Better monitoring of recurrent novae is needed during the pre-eruption plateau. Monitoring in the blue band is important for prediction.
I had the good fortune to talk with Brad on several occasions during the conference, and found him to be enthusiastic, knowledgeable, and engaging. Perhaps you have seen The Remarkable Science of Ancient Astronomy (The Great Courses), and he is just as articulate and energetic in real life. Among other things, we discussed how the internet is filled with misinformation, and even after an idea has been convincingly debunked, the misinformation continues to survive and multiply in cyberspace. This is a huge problem in the field of archaeoastronomy and, indeed, all fields of study. People tend to believe what they want to believe, never mind the facts.
Astrobites is a daily astrophysical-literature blog written by graduate students in astronomy around the world. The goal of Astrobites is to present one interesting paper from astro-ph per day in a brief format accessible to its target audience: undergraduate students in the physical sciences who are interested in active research.
Helioseismology can be done both from space (all) and the ground (some). Active regions on the far side of the Sun can be detected with helioseismology.
All HMI (Helioseismic and Magnetic Imager) data from the Solar Dynamics Observatory is available online.
A good approach to studying solar data is to subtract the average differential rotation at each point/region on the Sun and look at the residuals.
The Wilcox Solar Observatory has been making sun-as-a-star mean magnetic field measurements since 1975.
It is possible to infer electric currents on the Sun, but this is much more difficult than measuring magnetic fields.
Future directions in solar studies: moving from zonal averages to localized regions in our modeling, and the ability through future space missions to continuously monitor the entire surface of the Sun at every moment.
Systematic errors are nearly always larger than statistical uncertainty.
Day 2 – Tuesday, June 11, 2019
It is probably not hyperbole to state that every star in our galaxy has planets. About 1/5 of G-type stars have terrestrial planets within the habitable zone. Life is widespread throughout the universe.
Gas-grain interaction is at the core of interstellar chemistry. Interstellar ices, charged ices, surface chemistry – there is more time for interactions to occur on a dust grain than in a gas. Grain collisions are important, too.
Hot cores are transient regions surrounding massive protostars very early in their evolution. Similar regions are identified around low-mass protostars and are called corinos.
Methanol (CH3OH) is key to making simple organic molecules (SOM). Evaporating ice molecules drive rich chemistry. Dust plays a key role in the chemistry and in transporting material from the interstellar medium (ISM) to planetary systems.
The Rosetta mission detected amino acids on comet 67P/Churyumov–Gerasimenko.
JUICE (JUpiter ICy moons Explorer) is an ESA mission scheduled to launch in 2022, will enter orbit around Jupiter in October 2029 and Ganymede in 2032. It will study Europa, Ganymede, and Callisto in great detail.
The gravitational wave event GW170817 (two infalling and colliding neutron stars) was also detected as a gamma-ray burst (GRB) by the Fermi gamma-ray space telescope, which has a gamma-ray burst detector that at all times monitors the 60% of the sky that is not blocked by the Earth.
The time interval between the GW and GRB can range between tens of milliseconds up to 10 seconds.
The Milky Way galaxy circumnuclear disk is best seen at infrared wavelengths around 50 microns. Linear polarization tells us the direction of rotation. The star cluster near the MW center energizes and illuminates gas structures. Gravity dominates in this region. The role of magnetic fields in this region has been a mystery.
Pitch angle – how tightly wound the spiral arms are in a spiral galaxy.
Are spiral arms transient or long lived? They are probably long lived. There may be different mechanisms of spiral arm formation in grand design spirals compared with other types of spiral galaxies.
In studying spiral galaxies, we often deproject to face-on orientation.
The co-rotation radius is the distance from the center of a spiral galaxy beyond which the stars orbit slower than the spiral arms. Inside this radius, the stars move faster than the spiral arms.
The Sun is located near the corotation circle of the Milky Way.
The origins of supermassive black holes (SMBH) at the centers of galaxies are unclear. Were they seeded from large gas clouds, or were they built up from smaller black holes?
The black holes at the centers of spiral galaxies tend to be more massive when the spiral arm winding is tight, and less massive when the spiral arm winding is loose.
Spiral Graph is in review as a Zooniverse project and has not yet launched. Citizen scientists will trace the spiral arms of 6,000 deprojected spiral galaxies, and 15 traces will be needed for each galaxy. Spiral arm tracings will provide astronomers with intermediate mass black hole candidate galaxies.
Barred spiral galaxies are very common. 66% to 75% of spiral galaxies show evidence of a bar at near-infrared wavelengths.
Magnetic fields in the inner regions of spiral galaxies are scrambling radio emissions to some extent, but radio astronomers have ways to deal with this.
For me, the plenary lecture given by Suvrath Mahadevan, Pennsylvania State University, was the first truly outstanding presentation. His topic was “The Tools of Precision Measurement in Exoplanet Discovery: Peeking Under the Hood of the Instruments”. His discussion of the advance in radial velocity instrumentation was revelatory to me, as his starting point was Roger F. Griffin’s radial velocity spectrometer we used at Iowa State University in the 1970s and 1980s, giving us a precision of about 1 km/s. My, we have come a long way since then!
To discover our Earth from another star system in the ecliptic plane would require detecting an 8.9 cm/s velocity shift in the Sun’s motion over the course of a year.
Precision radial velocity measurement requires we look at the displacement of thousands of spectral lines using high resolution spectroscopy.
The two main techniques are 1) Simultaneous reference and 2) Self reference (iodine cell). Also, externally dispersed interferometry and heterodyne spectroscopy can be used.
Griffin 1967 ~ km/s → CORAVEL 1979 ~300 m/s → CORALIE/ELODIE 1990 ~ 5-10 m/s → HARPS 2000 ~ 1 m/s → ESPRESSO/VLT, EXPRES/DCT, NEID/KPNO, HPF/HET.
We cannot build instruments that are stable over time at 10 cm/s resolution or less.
You can track the relative change in velocity much better than absolute velocity because of the “noise” generated by stellar internal motions.
Measuring the radial velocity at red or infrared wavelengths is best for M dwarfs, and cooler stars.
High radial velocity precision will require long-term observations, and a better understanding of and mitigation for stellar activity. Many things need to be considered: telescope, atmosphere, barycentric correction (chromatic effects can lead to 1/2 m/s error), fibers, modal noise, instrument decoupled from the telescope, calibrators, optics, stability, pipeline, etc. Interdisciplinary expertise is required.
NEID will measure wavelengths of 380 – 930 nm, and have a spectral resolution of R ~ 90,000.
Pushing towards 10 cm/s requires sub-milli-Kelvin instrument stability high-quality vacuum chambers, octagonal fibers, scrambling, and excellent guiding of the stellar image on the fiber to better than 0.05 arcseconds.
Precision radial velocity instruments such as NEID and HPF weigh two tons, so at present they can only be used with ground-based telescopes.
Charge Transfer Efficiency (CTE): need CCDs with CTE > 0.999999. Other CCD issues that don’t flat field out accurately: CCD stitch boundaries, cross hatching in NIR detectors, crystalline defects, sub-pixel quantum efficiency differences. Even the act of reading out the detector introduces a noise source.
10 cm/s is within reach from a purely instrumental perspective, but almost everything has to be just right. But we need to understand stellar activity better: granulation, supergranulation, flares, oscillations, etc. We may not be able to isolate these components of stellar activity, but we will certainly learn a lot in the process.
1s time resolution is required to properly apply barycentric corrections.
Gene Byrd, University of Alabama, gave an interesting short presentation, “Two Astronomy Demos”. The first was “Stars Like Grains of Sugar”, reminiscent of Archimedes’ The Sand Reckoner. And “Phases with the Sun, Moon, and Ball”. He uses a push pin in a golf ball (the golf ball even has craters!). Morning works best for this activity. The Sun lights the golf ball and the Moon and they have the same phase—nice! Touching as well as seeing the golf ball helps students understand the phases of the Moon. Here’s a link to his paper on these two activities.
Daniel Kennefick, University of Arkansas, gave a short presentation on the 1919 eclipse expedition that provided experimental evidence (besides the correct magnitude of the perihelion precession of Mercury) that validated Einstein’s General Relativity. Stephen Hawking in his famous book A Brief History of Time mis-remembered that the 1979 re-analysis of the Eddington’s 1919 eclipse data showed that he may “fudged” the results to prove General Relativity to be correct. He did not! See Daniel Kennefick’s new book on the subject, No Shadow of a Doubt: The 1919 Eclipse That Confirmed Einstein’s Theory of Relativity.
Brad Schaefer, Louisiana State University, gave another engaging talk, presenting evidence that the Australian aborigines may have discovered the variability of the star Betelgeuse, much earlier than the oft-stated discovery by John Herschel in 1836. Betelgeuse varies in brightness between magnitude 0.0 and +1.3 quasi-periodically over a period of about 423 days. It has been shown that laypeople can detect differences in brightness as small as 0.3 magnitude with the unaided eye, and with good comparison stars (like Capella, Rigel, Procyon, Pollux, Adhara, and Bellatrix—not all of which are visible from Australia—for Betelgeuse). It is plausible that the variability of Betelgeuse may have been discovered by many peoples at many different times. The Australian aborigines passed an oral tradition through many generations that described the variability of Betelgeuse. https://ui.adsabs.harvard.edu/abs/2019AAS…23422407S/abstract.
As a longtime astronomical observer myself, I have actually never noticed the variability of Betelgeuse, but Brad has. After his presentation, I mentioned to Brad that it would be interesting to speculate what would lead early peoples to look for variability in stars in the first place, which seems to me to be a prerequisite for anyone discovering the variability of Betelgeuse. His response pointed out that all it would take is one observant individual in any society who would notice/record the variability and then point it out to others.
If you haven’t looked at the NASA/IPAC Extragalactic Database (NED) lately, you will find new content and functionality. It has been expanded a great deal, and now includes many stellar objects, because we don’t always know what is really a star and what is not. There is now a single input field where you can enter names, coordinates with search radius, etc. NED is “Google for Galaxies”.
I noticed during the 10-minute iPoster Plus sessions that there is a countdown timer displayed unobtrusively in the upper right hand corner that helps the presenter know how much time they have remaining. I think this would be a great device for anyone giving a short presentation in any venue.
Galactic archaeology is the study of the oldest stars and other structures in our galaxy to better understand how our galaxy evolved.
Day 2 ended with an evening presentation of “Cielo”, a documentary film by Alison McAlpine. Highly recommended!
I noted that “Cielo” was presented on the Documentary Channel in Canada. Too bad we do not have a channel like that here in the U.S.!
Day 3 – Wednesday, June 12, 2019
Day 3 began with what for me was the finest presentation of the entire conference: Joshua Winn, Princeton University, speaking on “Transiting Exoplanets: Past, Present, and Future”. I first became familiar with Josh Winn through watching his outstanding video course, The Search for Exoplanets: What Astronomers Know, from The Great Courses. I am currently watching his second course, Introduction to Astrophysics, also from The Great Courses. Josh is an excellent teacher, public speaker, and presenter, and it was a great pleasure to meet him at this conference.
Transits provide the richest source of information we have about exoplanets. For example, we can measure the obliquity of the star’s equator relative to the planet’s orbital plane by measuring the apparent Doppler shift of the star’s light throughout transit.
Who was the first to observe a planetary transit? Pierre Gassendi (1592-1655) was the first to observe a transit of Mercury across the Sun in November 1631. Jeremiah Horrocks (1618-1641) was the first to observe a transit of Venus across the Sun in November 1639. Christoph Scheiner (1573-1650) claimed in January 1612 that spots seen moving across the Sun were planets inside Mercury’s orbit transiting the Sun, but we know know of course that sunspots are magnetically cooled regions in the Sun’s photosphere and not orbiting objects at all. Though Scheiner was wrong about the nature of sunspots, his careful observations of them led him to become the first to measure the Sun’s equatorial rotation rate, the first to notice that the Sun rotated more slowly at higher latitudes, and the first to notice that the Sun’s equator is tilted with respect to the ecliptic, and to measure its inclination.
An exoplanet can be seen to transit its host star if the exoplanet’s orbit lies within the transit cone, an angle of 2R*/a centered on our line of sight to the star. R* is the star’s radius, and a is the semi-major axis of the planet’s orbit around the star.
Because of the geometry, we are only able to see transits of 1 out of every 215 Earth-Sun analogs.
Space is by far the best place to study transiting exoplanets.
If an exoplanet crosses a starspot, or a bright spot, on the star, you will see a “blip” in the transit light curve that looks like this:
Are solar systems like our own rare? Not at all! There are powerful selection effects at work in exoplanet transit statistics. We have discovered a lot of “hot Jupiters” because large, close-in planets are much easier to detect with their short orbital periods and larger transit cones. In actuality, only 1 out of every 200 sun-like stars have hot Jupiters.
Planet statistical properties was the main goal of the Kepler mission. Here are some noteworthy discoveries:
Kepler 89 – two planets transiting at the same time (only known example)
Kepler 36 – chaotic three-body system
Kepler 16 – first known transiting exoplanet in a circumbinary orbit
Transiting Exoplanet Survey Satellite (TESS) – Unlike Kepler, which is in an Earth-trailing heliocentric orbit, TESS is in a highly-elliptical orbit around the Earth with an apogee approximately at the distance of the Moon and a perigee of 108,000 km. TESS orbits the Earth twice during the time the Moon orbits once, a 2:1 orbital resonance with the Moon.
TESS has four 10.5 cm (4-inch) telescopes, each with a 24˚ field of view. Each TESS telescope is constantly monitoring 2300 square degrees of sky.
TESS is fundamentally about short period planets. Data is posted publicly as soon as it is calibrated. TESS has already discovered 700 planet candidates. About 1/2 to 2/3 will be true exoplanets. On average, TESS is observing stars that are about 4 magnitudes brighter than stars observed by Kepler.
The TESS Follow-Up Observing Program (TFOP) is a large working group of astronomical observers brought together to provide follow-up observations to support the TESS Mission’s primary goal of measuring the masses for 50 planets smaller than 4 Earth radii, in addition to organizing and carrying out follow-up of TESS Objects of Interest (TOIs).
HD 21749 – we already had radial velocity data going back several years for this star that hosts an exoplanet that TESS discovered
Gliese 357 – the second closest transiting exoplanet around an M dwarf, after HD 219134
TESS will tell us more about planetary systems around early-type stars.
TESS will discover other transient events, such as supernovae, novae, variable stars, etc. TESS will also make asteroseismology measurements and make photometric measurements of asteroids.
The James Webb Space Telescope (JWST) will be able to do follow-up spectroscopy of planetary atmospheres.
Upcoming exoplanet space missions: CHEOPS, PLATO, and WFIRST.
Hot Jupiter orbits should often be decaying, so this is an important area of study.
Sonification is the process of turning data into sound. For example, you could “listen” to a light curve (with harmonics, e.g. helioseismology and asteroseismology) of a year’s worth a data in just a minute or so.
Solar cycles have different lengths (11-ish years…).
Some predictions: 2019 will be the warmest year on record, 2020 will be less hot. Solar cycle 24 terminate in April 2020. Solar cycle 25 will be weaker than cycle 24. Cycle 25 will start in 2020 and will be the weakest in 300 years, the maximum (such as it is) occurring in 2025. Another informed opinion was that Cycle 25 will be comparable to Cycle 24.
Maunder minimum: 1645 – 1715
Dalton minimum: 1790 – 1820
We are currently in the midst of a modern Gleissberg minimum. It remains to be seen if it will be like the Dalton minimum or a longer “grand minimum” like the Maunder minimum.
Citizen scientists scanning Spitzer Space Telescope images in the Zooniverse Milky Way Project, have discovered over 6,000 “yellow balls”. The round features are not actually yellow, they just appear that way in the infrared Spitzer image color mapping.
Yellow balls (YBs) are sites of 8 solar mass or more star formation, surrounded by ionized hydrogen (H II) gas. YBs thus reveal massive young stars and their birth clouds.
Antlia 2 is a low-surface-brightness (“dark”) dwarf galaxy that crashed into our Milky Way galaxy. Evidence for this collision comes from “galactoseismology” which is the study of ripples in the Milky Way’s disk.
The Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and the Sagittarius Dwarf Galaxy have all affected our Milky Way Galaxy, but galactoseismology has shown that there must be another perturber that has affected the Milky Way. Antlia 2, discovered in November 2018 from data collected by the Gaia spacecraft, appears to be that perturber.
Gaia Data Release 2 (DR2) indicates that the Antlia 2 dwarf galaxy is about 420,000 ly distant, and it is similar in extent to the LMC. It is an ultra-diffuse “giant” dwarf galaxy whose stars average two magnitudes fainter than the LMC. Antlia 2 is located 11˚ from the galactic plane and has a mass around 1010 solar masses.
A question that is outstanding is what is the density of dark matter in Antlia 2? In the future, Antlia 2 may well be an excellent place to probe the nature of dark matter.
Gravity drives the formation of cosmic structure, dark energy slows it down.
Stars are “noise” for observational cosmologists.
“Precision” cosmology needs accuracy also.
The Vera Rubin telescope (Large Synoptic Survey Telescope) in Chile will begin full operations in 2022, collecting 20 TB of data each night!
We have a “galaxy bias” – we need to learn much more about the relation between galaxy populations and matter distribution.
Might there be an irregular asymmetric cycle underlying the regular 22-year sunspot cycle? The dominant period associated with this asymmetry is around 35 to 50 years.
The relationship between differential rotation and constant effective temperature of the Sun: the Sun has strong differential rotation along radial lines, and there is little variation of solar intensity with latitude.
Solar filaments (solar prominences) lie between positive and negative magnetic polarity regions.
Alfvén’s theorem: in a fluid with infinite electric conductivity, the magnetic field is frozen into the fluid and has to move along with it.
Some additional solar terms and concepts to look up and study: field line helicity, filament channels, kinetic energy equation, Lorentz force, magnetic energy equation, magnetic flux, magnetic helicity, magnetohydrodynamics (MHD), meridional flow, polarity inversion lines, relative helicity, sheared arcade, solar dynamo.
We would like to be able to predict solar eruptions before they happen.
Magnetic helicity is injected by surface motions.
It accumulates at polarity inversion lines.
It is removed by coronal mass ejections.
Day 4 – Thursday, June 13, 2019
Cahokia (our name for it today) was the largest city north of Mexico 1,000 years ago. It was located at the confluence of the Mississippi, Missouri, and Illinois Rivers. At its height from 1050 – 1200 A.D., Cahokia city covered 6 square miles and had 10,000 to 20,000 people. Cahokia was a walled city. Some lived inside the walls, and others lived outside the walls.
Around 120 mounds were built at greater Cahokia; 70 are currently protected. Platform mounds had buildings on top, and some mounds were used for burial and other uses.
Monks mound is the largest prehistoric earthwork in the Americas. Mound 72 has an appalling history.
Woodhenge – controversial claim that it had an astronomical purpose. Look up Brad Schaefer’s discussion, “Case studies of three of the most famous claimed archaeoastronomical alignments in North America”.
Cahokia’s demise was probably caused by many factors, including depletion of resources and prolonged drought. We do not know who the descendents of the Cahokia people are. It is possible that they died out completely.
The Greeks borrowed many constellations from the Babylonians.
One Sky, Many Astronomies
The neutron skin of a lead nucleus (208Pb) is a useful miniature analog for a neutron star.
Infalling binary neutron stars, such as GW 170817, undergo tidal deformation.
Minisatellite: 100-180 kg
Microsatellite: 10-100 kg
Nanosatellite: 1-10 kg
Picosatellite: 0.01-1 kg
Femtosatellite: 0.001-0.01 kg
CubeSats are a class of nanosatellites that use a standard size and form factor. The standard CubeSat size uses a “one unit” or “1U” measuring 10 × 10 × 10 cm and is extendable to larger sizes, e.g. 1.5, 2, 3, 6, and even 12U.
The final plenary lecture and the final session of the conference was a truly outstanding presentation by James W. Head III, Brown University, “The Apollo Lunar Exploration Program: Scientific Impact and the Road Ahead”. Head is a geologist who trained the Apollo astronauts for their Moon missions between 1969 and 1972.
During the early years of the space program, the United States was behind the Soviet Union in space technology and accomplishments. The N1 rocket was even going to deliver one or two Soviet cosmonauts to lunar orbit so they could land on the Moon.
Early in his presidency, John F. Kennedy attempted to engage the Soviet Union in space cooperation.
Chris Kraft’s book, Flight: My Life in Mission Control is recommended.
The Apollo astronauts (test pilots) were highly motivated students.
The United States flew 21 robotic precursor missions to the Moon in the eight years before Apollo 11. Rangers 1-9 were the first attempts, but 1 through 6 were failures and we couldn’t even hit the Moon.
Head recommends the recent documentary, Apollo 11, but called First Man Hollywood fiction, saying, “That is not the Neil Armstrong I knew.”
The Apollo 11 lunar samples showed us that the lunar maria (Mare Tranquillitatis) has an age of 3.7 Gyr and has a high titanium abundance.
The Apollo 12 lunar excursion module (LEM) landed about 600 ft. from the Surveyor 3 probe in Oceanus Procellarum, and samples from that mission were used to determine the age of that lunar maria as 3.2 Gyr.
Scientists worked shoulder to shoulder with the engineers during the Apollo program, contributing greatly to its success.
Apollo 11 landed at lunar latitude 0.6˚N, Apollo 12 at 3.0˚S, Apollo 14 at 3.6˚S, and Apollo 15 at 26.1˚N. Higher latitude landings required a plane change and a more complex operation to return the LEM to the Command Module.
The lunar rover was first used on Apollo 15, and allowed the astronauts to travel up to 7 km from the LEM. Head said that Dave Scott did remarkable geological investigations on this mission. He discovered and returned green glass samples, and in 2011 it was determined that there is water inside those beads. Scott also told a little fib to Mission Control to buy him enough time to pick up a rock that turned out to be very important, the “seat belt basalt”.
In speaking about Apollo 16, Head called John Young “one of the smartest astronauts in the Apollo program”.
Harrison Schmitt, Apollo 17, was the only professional geologist to go to the Moon, and he discovered the famous “orange soil”. This is the mission where the astronauts repaired a damaged fender on the lunar rover using duct tape and geological maps to keep them from getting covered in dust while traveling in the rover.
When asked about the newly discovered large mass under the lunar surface, Head replied that it is probably uplifted mantle material rather than an impactor mass underneath the surface.
Radiometric dating of the Apollo lunar samples have errors of about ± 5%.
One of the reasons the Moon’s albedo is low is that space weather has darkened the surface.
The South Pole-Aitken basin is a key landing site for future exploration. In general, both polar regions are of great interest.
Smaller objects like the Moon and Mars cooled efficiently after their formation because of their high surface area to volume ratio.
We do not yet know if early Mars was warm and wet, or cold and icy with warming episodes. The latter is more likely if our solar system had a faint young sun.
Venus has been resurfaced in the past 0.5 Gyr, and there is no evidence of plate tectonics. The first ~80% of the history of Venus is unknown. Venus probably had an ocean and tectonic activity early on, perhaps even plate tectonics. Venus may have undergone a density inversion which exchanged massive amounts of material between the crust and mantle. 80% of the surface of Venus today is covered by lava flows.
A mention was made that a new journal of Planetary Science (in addition to Icarus, presumably) will be coming from the AAS soon.
I attend a lot of meetings and lectures (both for astronomy and SAS), and I find that I am one of the few people in attendance who write down any notes. Granted, a few are typing at their devices, but one never knows if they are multitasking instead. For those that don’t take any notes, I wonder, how do they really remember much of what they heard days or weeks later without having written down a few keywords and phrases and then reviewing them soon after? I did see a writer from Astronomy Magazine at one of the press conferences writing notes in a notebook as I do. I believe it was Jake Parks.
Anyone who knows me very well knows that I love traveling by train. To attend the AAS meeting, I took a Van Galder bus from Madison to Chicago, and then Amtrak from Chicago to St. Louis. Pretty convenient that the AAS meeting was held at the Union Station Hotel, just a few blocks from Amtrak’s Gateway Station. It is a fine hotel with a lot of history, and has an excellent on-site restaurant. I highly recommend this hotel as a place to stay and as a conference venue.
The bus and train ride to and fro afforded me a great opportunity to catch up on some reading. Here are a few things worth sharing.
astrometry.net – you can upload your astronomical image and get back an image with all the objects in the image astrometrically annotated. Wow!
16 Psyche, the most massive metal-rich asteroid, is the destination for a NASA orbiter mission that is scheduled to launch in 2022 and arrive at Psyche in 2026. See my note about 16 Psyche in the AAS notes above.
The lowest hourly meteor rate for the northern hemisphere occurs at the end of March right after the vernal equinox.
A tremendous, dynamic web-based lunar map is the Lunar Reconnaissance Orbiter Camera (LROC) Quickmap, quickmap.lroc.asu.edu.
I read with great interest Dr. Ken Wishaw’s article on pp. 34-38 in the July 2019 issue of Sky & Telescope, “Red Light Field Test”. Orange or amber light is probably better that red light for seeing well in the dark while preserving your night vision. You can read his full report here. Also, see my article “Yellow LED Astronomy Flashlights” here.
Jupiter and Saturn will have a spectacular conjunction next year. As evening twilight fades on Monday, December 21, 2020, the two planets will be just 1/10th of a degree apart, low in the southwestern sky.
The light curve of a stellar occultation by a minor planet (asteroid or TNO) resembles a square well if the object has no atmosphere (or one so thin that it cannot be detected, given the sampling rate and S/N), and the effects of Fresnel diffraction and the star’s angular diameter are negligible.
Astronomer Margaret Burbidge, who turns 100 on August 12, 2019, refused the AAS Annie Jump Cannon Award in 1972, stating in her rejection letter that “it is high time that discrimination in favor of, as well as against, women in professional life be removed, and a prize restricted to women is in this category.” In 1976, Margaret Burbidge became the first woman president of the AAS, and in 1978 she announced that the AAS would no longer hold meetings in the states that had not ratified the Equal Rights Amendment (ERA).
During the days following the conference when I was writing this report, I received the happy news from both the AAS and Sky & Telescope that AAS was the winning bidder of S&T during a bankruptcy auction of its parent company, F+W Media. I believe that this partnership between the AAS and Sky & Telescope will benefit both AAS members and S&T readers immensely. Peter Tyson, Editor in Chief of Sky & Telescope, stated in the mutual press release, “It feels like S&T is finally landing where it belongs.” I couldn’t agree more!
At a school board meeting in November 2017, concerns were raised about inadequate lighting for evening school events, so the Dodgeville School District directed Alliant Energy to install some additional lights. The lighting was installed during a warm spell in January 2018, and the photographs you see below were taken during the afternoon and evening of June 17, 2018.
Rather than being used only when school events are taking place in the evening, these terrible lights are on dusk-to-dawn 365 nights a year. They are too bright, poorly directed, poorly shielded, and the glare they cause on W. Chapel St. and N. Johnson St. could pose a safety concern for pedestrians not being seen by drivers experiencing disability glare. I can imagine that adjacent neighbors are not too happy with the light trespass into their yards and residences, either.
This is a perfect example of poor lighting design and unintended consequences. How could it be done better? Look for the solution below the following series of photos documenting the problem.
In fact, regardless of the lighting solution, the lights should be either turned off or dimmed down to a lower level later at night. (Security cameras will see just fine at lower light levels if that is a concern.)
Good neighbor outdoor lighting means minimizing GLUT:
Glare—never helps visibility Light Trespass—no point in putting light where it is not needed Uplight—sending light directly up into the night sky is a total waste Too Much Light—use the right amount of light for the task, don’t overlight
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
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?
A new bright white LED streetlight made its debut in Dodgeville, Wisconsin on Friday, November 3, 2017, and it isn’t pretty.
The white-light LED streetlight is located at the NE corner of W. Washington St. & N. Johnson St. in Dodgeville. The illumination level on the ground peaks at 3.15 fc. An existing orange-light high pressure sodium streetlight at the SW corner of W. Division St. & N. Virginia Terrace peaks at 1.23 fc, which is typical.
Even though the reduction of uplight and near-horizontal light (i.e. “glare”) from this luminaire is a welcome improvement, an illumination level 2.6 times as bright as before is neither welcome nor justified. Furthermore, lower illumination levels may be acceptable when using white-light LED luminaires in comparison with high pressure sodium (Glamox n.d.). More research is needed on the effect of spectral composition on both brightness perception and, more importantly, visual acuity at various illuminance levels.
I do not have an instrument to measure the correlated color temperature (CCT) of this luminaire, but visually it looks to me to be around 4000 K, which is too blue. I will check with the City of Dodgeville and report back here. The International Dark-Sky Assocation (IDA) and the American Medical Assocation (AMA 2016) recommend using “warm white” LEDs with a CCT no higher than 3000 K, with 2700 K preferred.
AMA (2016), Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting H-135.927. Retrieved November 5, 2017 from https://policysearch.ama-assn.org/policyfinder/detail/H-135.927?uri=%2FAMADoc%2FHOD-135.927.xml.
Glamox (n.d.), The Glamox Brightness Sensitivity Test. Retrieved November 5, 2017 from http://glamox.com/gmo-recreational/led-brightness.
IDA (n.d.), LED: Why 3000K or Less. Retrieved November 5, 2017 from http://www.darksky.org/lighting/3k/.
Today, we celebrate the 140th anniversary of the birth of one of America’s greatest astrophysicists: Henry Norris Russell (1877-1957). Called the “Dean of American Astronomers”, he is perhaps best remembered for his discovery of the relationship between the luminosity (absolute brightness) of a star and its color. We call any plot of luminosity vs. color for a group of stars an H-R diagram, named after Russell and Danish astronomer Ejnar Hertzsprung (1873-1967) who independently discovered this relationship.
Russell noticed that cool (relative to other stars) red stars come in two varieties: those that are dim, and others that are very bright. The only way a cool, red star could be so bright would be if the star were very, very large1. In this way, Russell discovered that there are red giants and red dwarfs, but no medium-sized red stars. Further studies by Russell and others led to the use of the H-R diagram as a tool in understanding the life cycles of stars. Red giants, it turns out, are one of the final stages in the life of an ordinary star (like the Sun, for example). Red dwarfs are low-mass stars that change very little throughout their lives.
After famously rejecting the revolutionary conclusion (in 1925) by Cecilia Payne-Gaposchkin (1900-1979) establishing that hydrogen is the primary constituent of the Sun and other stars, Henry Russell concluded four years later that Payne-Gaposchkin was correct, and acknowledged her significant contribution. Moreover, he surmised that the main physical characteristics of stars are determined by just two basic parameters: mass and chemical composition. This idea is known as the Vogt-Russell theorem, named after Russell and German astronomer Heinrich Vogt (1890-1968), who independently came up with the same idea.
An interesting sidenote. Early in his stellar career, when he was just 24 years of age, Henry Russell wrote an interesting article published in the May 1902 issue of Popular Astronomy and dated March 24, 1902: “Shadows Cast by Starlight”. It is a fascinating read—all the more special because it was written at a time (now over 115 years ago) when light pollution had not yet destroyed our nocturnal environment.
1Here we are comparing stars at comparable distances, such as in a star cluster.
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
A dark sky community would appeal to people who value the night sky and a natural nighttime environment
It will probably be many years before the majority of people will accept life without dusk-to-dawn outdoor lighting
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
It is better to live in community than in isolation
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
A dark sky community should be affordable, with a variety of housing options (units that can be rented, for example)
An observatory commons area should be developed for observing and include more than one observatory for use by members of the community
The dark sky community should engage in an ambitious educational outreach program, including the operation of an astronomy resort and astro-tourism business
The business end of the community should be a nonprofit corporation or cooperative that operates the astronomy resort and rental properties
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
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
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!
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
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
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
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.