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Solar limb darkening is a prominent feature seen in white images of the Sun: the brightness of the solar disk is greatest at the solar center and decreases radially outward towards the limb. White light images can be used to examine and even model limb darkening; however, the limb-darkening effect is, in fact, wavelength dependent. Limb darkening is more pronounced at the blue end of the spectrum and less at the red end. We discuss a relatively simple method to examine the wavelength-dependent nature of limb darkening using solar projection, smartphone imaging, and SalsaJ software.

The typical equipotential lab involves students sampling points in an electrode configuration: they move the probe around until they find a series of points with the same potential. Other authors have highlighted some difficulties with the traditional lab approach: most do not allow real-time visualization of equipotential lines, and students often seem to rely conceptually on single point charge equipotential models or Coulomb’s laws. I propose a different approach to the parallel plate lab: Students are directed to set up a grid of equally spaced points between parallel plates. Students measure and record probe voltages in a spreadsheet and analyze voltages as a function of x and y. I demonstrate typical results and briefly discuss possible extensions.

Light pollution is a detrimental consequence of excess or unwise use of artificial light at night. Hopes for reducing light pollution have been rooted in educating teachers, students, and the general public. These programs manifest in a diverse set of disciplines. Many programs focus on connecting light pollution to the damaging biological and environmental effects. There are even efforts to connect solutions for light pollution to engineering education. “Globe at Night” is an educational program that engages participants in astronomical observations of the night sky to bring awareness to the problem of light pollution and lies squarely in the domain of observational astronomy. Many of these efforts make use of physics that goes “under the radar”; we advocate for making direct connections to the physics of light pollution to students and teachers.

When driving on a sunny day, one can sometimes observe a small solar spectrum in the rearview mirror of a vehicle. The formation of this “rainbow” results from the prism-like structure of the rearview mirror. Our investigation of this phenomenon reveals that the resulting spectrum is formed in a manner similar to the way a rainbow is formed by a water droplet. We suggest a demonstration that you can perform so that your students can observe this phenomenon. All that is required is a sunny day, a ring stand, a clamp holder, and rearview mirror.

We present a simple method to estimate the size of Earth's umbral shadow in a classroom setting. The method uses the published sky brightness curves obtained during a total lunar eclipse and requires only a conceptual understanding of lunar eclipses and simple geometric considerations. It is suitable for use in introductory and upper level astronomy courses.

The citizen Continental-America Telescopic Eclipse (CATE) Experiment was a new type of citizen science experiment designed to capture a time sequence of white-light coronal observations during totality from 17:16 to 18:48 UT on 2017 August 21. Using identical instruments the CATE group imaged the inner corona from 1 to 2.1 RSun with 1.″43 pixels at a cadence of 2.1 s. A slow coronal mass ejection (CME) started on the SW limb of the Sun before the total eclipse began. An analysis of CATE data from 17:22 to 17:39 UT maps the spatial distribution of coronal flow velocities from about 1.2 to 2.1 RSun, and shows the CME material accelerates from about 0 to 200 km s−1 across this part of the corona. This CME is observed by LASCO C2 at 3.1–13 RSun with a constant speed of 254 km s−1. The CATE and LASCO observations are not fit by either constant acceleration nor spatially uniform velocity change, and so the CME acceleration mechanism must produce variable acceleration in this region of the corona.

Fluorescence spectra excited by laser pointers have been the subject of several papers in TPT. These papers all describe a fluorescence phenomenon in which the reflected laser light undergoes a change in color: this color change results from the combination of some partially reflected laser light and additional colors generated by fluorescent emission. Here we examine the fluorescence spectra of highlighter inks using green and violet laser pointers. We use an RSpec Explorer spectrometer to obtain spectra and compare the emission spectra of blue, green, yellow, orange, pink, and purple highlighters. The website Compound Interest details the chemical composition of highlighter inks; in addition, the site discusses how some base dye colors can be combined to produce the variety commercially available colors. Spectra obtained in this study were qualitatively consistent with the Compound Interest site. We discuss similarities and differences between various highlighter colors and conclude with the relevance o...

Glow sticks are a popular Halloween staple familiar to most of our students. The production of light via a chemical reaction is called “chemiluminescence,” and glow sticks are often used as demonstrations and experiments in the chemistry classroom to study reaction rates as a function of temperature.1–3 A black light can be used to illuminate glow sticks that have not been cracked or those that are “dead” in order to demonstrate fluorescence in liquid chemicals.4 In this article, we present the use of glow sticks as an inexpensive demonstration of spectra and color addition.

Studies on cognitive aspects of science education, especially how students achieve conceptual change, have been a focus of interest for many years.1 Researchers of student learning and conceptual change have developed several easily applicable teaching strategies. One of these strategies is known as discrepant events. Discrepant events are very powerful ways to stimulate interest, motivate students to challenge their covert science misconceptions, and promote higher‐order thinking skills. The key point is that directly challenging students' naive ideas will lead to more quality science learning going on in the classroom. In this paper, we summarize the research‐based role of discrepant events in conceptual change and we share several highly successful discrepant events we use in our own classes.

In introductory astronomy courses, I typically introduce the three types of spectra: continuous, absorption line, and emission line. It is standard practice to use an ordinary incandescent light bulb to demonstrate the production of a continuous spectrum, and gas discharge tubes to demonstrate the production of an emission line spectrum. The concept of an absorption spectrum is more difficult for students to grasp. A variety of commercially available light bulbs can be used to demonstrate absorption spectra. Here I discuss the use of specialty incandescent light bulbs to demonstrate the phenomenon of absorption of the continuous spectrum produced by a hot tungsten filament. The bulbs examined include the GE Reveal bulb, yellow anti-insect lights, colored party bulbs, and an incandescent “black light” bulb. The bulbs can be used in a lecture or laboratory setting.

Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

Several papers in this journal have dealt with the fluorescence in orange neon plastic, olive oil, and soda. In each case, the fluorescent emission was excited by either green or violet-blue laser light. In this paper, we examine the fluorescent emission spectra of so-called neon colored papers and plastic clipboards available in department and office supply stores. We also employ violet-blue and green laser pointers as excitation sources. We conclude with a brief discussion of neon pigments in terms of the “day glow” or “daylight fluorescence” phenomenon.

PUBLISHED, Symbiotic binary stars typically consist of a hot compact star orbiting a cool giant. Overlaid on the continuum from these stars is a nebular spectrum produced by the photoionization of the cool star wind by the hot star. Most of the observed emission lines are readily identifiable with common ions; however, a pair of lines at lambdalambda6825 and 7082 remained unidentified until relatively recently. A case has been made that these long-unidentified emission lines result from the Raman scattering of O vi lambdalambda1032, 1038 resonance photons. We present near-simultaneous far-UV and optical observations of the symbiotic star Z Andromedae, obtained with the space-borne Hopkins Ultraviolet Telescope and the Mount Hopkins 1.5 m telescope. Our data show the presence of both the O vi lambdalambda1032, 1038 resonance doublet and the lambda6825 and lambda7082 emission lines and provide strong evidence for the Raman effect in Z And. We show that the unusual line ratio of 7:1 observed for the O vi lines is due to the effects of interstellar H_2 absorption. Correction for this effect results in a line ratio of close to2:1, consistent with optically thin emission. We derive the efficiency for the Raman-scattered O vi lines and compare them with previously reported measurements for RR Telescopii.

A new camera attached to EchoStar 11, a geostationary communications satellite, recently started sending breathtaking and near real-time images of Earth. Available on one of DISH Network’s channels, viewers can see our planet 24/7, including occasional appearances by the Sun, the Moon, Venus, and space debris. These images present an excellent opportunity to teach about the Sun-Earth-Moon system. The purpose of this article is to introduce the DISH Earth channel to science educators, to provide a teacher-tested sample lesson plan using DISH Earth channel videos, and to suggest additional topics that could be explored with this newly available resource.