Discovering Our Stellar Neighborhood Modeling the Nearby Stars in Three Dimensions

[ILLUSTRATION OMITTED] The stars closest to Earth aren't particularly remarkable or exciting. They're average stars typical of the spiral arms of our Milky Way galaxy. In fact, until recently, most astronomy and Earth science textbooks ignored all but the largest of them to focus on distant, more exotic objects like red supergiants or black holes. But the recent discovery of exoplanets, or planets that orbit stars outside our solar system, has changed all that. The closest star system, Alpha Centauri, has at least one Earth-size planet that orbits its second star, Alpha Centauri B, and a recent study suggests as many as five planets could orbit Tau Ceti (Tuomi 2013). Our stellar neighborhood is becoming a lot more interesting. To help my physics and astronomy students grasp the concepts of stellar coordinates, constellations, star names, and star classes, I've spent the last 20 years perfecting a crowning activity for our star unit. In this activity, student teams work together to build a three-dimensional (3-D) model of "nearby" space, made up of star systems 13 light-years (i.e., the distance light travels in one year) from the Sun. Students consistently remark that this project is among the most memorable of the year. Their unit test scores and essay assignments, such as the Interstellar Voyage Proposal (see "On the web"), show a deep understanding of stars and nearby space. Addressing the standards Building a 3-D model of the nearby stars requires several days of class time, but this activity is well worth the effort with the emphasis of the Next Generation Science Standards (NGSS Lead States 2013) on science and engineering practices and crosscutting concepts. Students engage in the scientific and engineering practice of Developing and Using Models (and understanding their limitations) as well as the practice of Using Mathematics and Computational Thinking. The activity also emphasizes the crosscutting concepts of Scale and Proportion, teaches the Earth and space science disciplinary core idea of Earth's Place in the Universe, and touches on light and the electromagnetic spectrum. Model preparation and materials Alternative methods exist for building 3-D models of the nearby stars. For example, the NASA Institute for Advanced Concepts (NIAC, date unknown) developed a model that uses quilting pins as stars mounted on a foamcore base. Another model (Furutani 2009) mounts stars made from painted Styrofoam balls on long wires sticking up from wooden bases. The advantage of the model I developed is that the stars hang from a platform which in turn hangs from the classroom ceiling, so students can literally get inside the model and see how the constellations shift depending on the viewer's perspective. Also, gravity keeps the star models in their places (mounting stars on wires from the floor creates problems if the wires get bumped or bent). By using trigonometry, students can determine the positions of the stars more accurately. I installed eyebolts in my ceiling to hang the platform. Teachers in classrooms with ceiling tiles could place hooks of stiff wire over the tile dividers and hang the model from them. My 3-D model costs about $50 to construct, but teachers can store and reuse it. The platform consists of four pieces of foamcore taped together with clear packing tape and stiffened with cardboard packing tubes or PVC pipe. Stars are located using a polar coordinate system similar to longitude, latitude, and elevation. Right ascension is celestial longitude, the angular distance measured to the right (eastward) along the celestial equator from the vernal equinox, and declination is the latitude north or south of the celestial equator. On the underside of the platform, students draw a guide circle with radial spokes every 10[degrees] for the right ascension angles, progressing in a clockwise direction. They label the vernal equinox as 0[degrees] and then each radial spoke and light-year circle. …