Fenómeno

Pregunta Clave

¿Qué crees que la expansión puede revelarnos sobre el Universo?

Argumentos

El argumento del proceso está pensado para centrarse en los estudiantes y conectar con las lecciones dentro de la unidad. La investigación "El Universo en Expansión", que incluye este fenómeno, encajaría mejor en el argumento de la unidad orientado a la compresión de la evolución, la estructura o la expansión del Universo.

Los posibles argumentos incluyen:

¿Qué podemos saber/observar/medir del Universo?

¿Cómo la expansión del Universo apoya la teoría del Big Bang?

Instrucciones para presentar el Fenómeno

Este fenómeno se puede presentar a los estudiantes a través de experiencias de modelado práctico o mediante un video del modelo. Seleccione la opción de abajo que mejor se ajuste a sus necesidades.

1. Antes de que inicien las clases, preparare una Guía de Preguntas (DQB) que todos los estudiantes puedan ver. Puede crearse con notas adhesivas o en formato digital, como Jamboard (ver otros recursos aquí). La DQB debe incluir la pregunta clave específica para esta lección: "¿Qué podemos aprender sobre el Universo al estudiar su expansión?". A lo largo de la lección, los estudiantes consultarán varias veces esta DQB.
2. Pida a los estudiantes que lean y reflexionen sobre la pregunta clave antes de realizar la actividad (3 minutos).
3. Informe a los estudiantes que trabajarán con un modelo físico o verán un video que representa la expansión del Universo (con algunas limitaciones).

4. Opción 1 (Esfera de Hoberman)

Entregue una Esfera de Hoberman a los grupos de estudiantes o enseñe a toda la clase los siguientes pasos utilizando una Esfera de Hoberman.

Comience con la esfera en su tamaño más pequeño y expándala lentamente hasta su posición máxima (los estudiantes pueden repetir estas acciones según sea necesario para hacer sus observaciones).

Opción 2 (Video de la Esfera de Hoberman)

Muestre el video.

Puede seguir reproduciendo el video mientras los estudiantes observan y reflexionan sobre sus observaciones.

Opción 3 (Otras opciones de modelado)

Utilice uno de los modelos habituales (inflar un globo, la analogía del pan con pasas (o galletas de chocolate), el ejercicio de la cinta elástica) para demostrar la expansión del espacio.

5. Plantee a los alumnos la siguiente pregunta para orientarles con los componentes de la esfera y comprobar su comprensión inicial.

"La Esfera de Hoberman tiene dos componentes: la cuadrícula y los cuadrados de colores. ¿Qué representa cada uno de estos componentes sobre el Universo?". Ayude a los estudiantes a comprender que los cuadrados de colores representan las galaxias y la cuadrícula representa el espacio o el espacio-tiempo.

6. A continuación, dígales: "En este modelo utilizado con la Esfera de Hoberman, el espacio-tiempo del Universo y estas galaxias constituyen todo el Universo: no hay nada dentro de la esfera ni fuera de ella que sea parte del Universo".

7. Los estudiantes deben reflexionar sobre lo que han visto e intentar averiguar cómo representa este aparato la expansión del Universo. Deben pensar qué más necesitan saber y qué preguntas se pueden plantear. Los estudiantes deben anotar sus preguntas y compartirlas con toda la clase. Estas preguntas deberán incluirse en la DQB para que todos los estudiantes puedan consultarlas (5 minutos).

8. Facilite un debate sobre las preguntas donde participe toda la clase. Empiece por identificar y agrupar las preguntas comunes en categorías (10 minutos).

Print Star Cards

Print the star card sets listed below. Students will be working in small groups for this activity. There are four different sets of star cards. Print enough sets of star cards for each group to have one set.

Introduce the Phenomenon

1. Explain to the students that they will be going on a stellar “safari”, observing and gathering information about stars (rather than animals).

2. Place students in small groups and give each group a set of star cards. When each group receives their cards, they should begin observing their stars, looking for patterns.

3. Next, give students five minutes to work with their group to organize their set of stars. There are no restrictions or guidelines for how they should organize their stars. You can encourage groups to be creative or to consider prior knowledge.

4. After five minutes, or when the groups are finished organizing their set of stars, go on a gallery walk around the room as a class. As you stop together at each group, ask the group to explain to the class how they organized their set of star cards. Optional: after the gallery walk, challenge students to find a new way to organize their star cards.

5. After the gallery walk, present the students with the investigation driving question, “How are stars different from each other?” Hold a class brainstorming session with students working dynamically on whiteboards and sticky notes to share ideas or responses to the driving question. Encourage students to think about some of the properties they saw on their star cards. Then facilitate a class discussion, identifying common themes.

6. Then, ask students to individually generate questions that will lead to further investigation of this topic. Students should place their questions on the driving question board. Work with the students to organize the driving question board by common themes in the questions. Examples:

9. Revisit the investigation driving question and tell students they will be completing an investigation that will help them answer this driving question along with their generated questions on the DQB.

10. Begin the Exploding Stars Investigation.

Short Descriptions of Some Historical Supernovae - Part 1

Supernova RCW 86

RCW 86 is the oldest recorded supernova. In 185 A.D., Chinese astronomers saw a "guest star" suddenly appear in the night sky in the constellation that today is known as Circinus. The Book of Later Han volume 102 gives the following description:

"In the 2nd year of the epoch Zhongping [中平], the 10th month, on the day Kwei Hae [癸亥] [Year 185], a 'guest star' appeared in the middle of Nan Mun [asterism containing Alpha Centauri], The size was half a bamboo mat. It displayed various colors, and gradually lessened. In the 6th month of the succeeding year it disappeared."

There’s also some evidence that Roman astronomers witnessed the event. It had a peak apparent magnitude of −4, similar to the planet Venus when at its brightest.

The first page of the Book of the Later Han. Image by By 范曄 (Fan Ye, 398–445) - 南宋紹興刊本 (Southern Song Shaoxing [1131-1162] edition), Public Domain.

Supernova 1006

On April 30, 1006 A.D., the brightest supernova in recorded history appeared, reaching an estimated apparent magnitude of -7.5. At its peak, this supernova would have been bright enough to be seen in broad daylight. Its light was bright enough to illuminate the ground and cast shadows at night. Egyptian astrologer and astronomer Ali ibn Ridwan, writing in a commentary on Ptolemy's Tetrabiblos, stated that the "spectacle was a large circular body, 2 1⁄2 to 3 times as large as Venus. This peak brightness would have been around 16 times brighter than Venus, or about the same as a crescent Moon (when the moon is 25% illuminated). Monks at the Abbey of Saint Gall in Switzerland wrote that "[i]n a wonderful manner this was sometimes contracted, sometimes diffused, and moreover sometimes extinguished...It was seen likewise for three months.”

A rock carving, or petroglyph, in Arizona's White Tanks Regional Park, near Phoenix, may depict this striking astronomical event. The Hohokam people occupied the region from about 500–1100 A.D. The carving shows a large rayed circle beneath a scorpion symbol. The 1006 supernova was visible in the constellation Lupus, southwest of Scorpius the Scorpion.

https://astronomy.com/news/2006/06/rock-art-records-an-ancient-blast

Supernova 1054

On July 4, 1054 AD, a new star appeared in the constellation Taurus the Bull. Chinese records suggest it was brighter than all the stars and planets, surpassed in luminosity only by the Sun and the Moon. Other observations of the explosion were recorded by Japanese and Arab stargazers.

The supernova was visible in broad daylight, reaching an estimated apparent magnitude of -7, about ten times that of Venus, the brightest astronomical object visible from Earth besides the Sun and Moon. It remained visible by day for 23 days, and by night for 653 days.

A pictograph (seen below), associated with the Ancestral Puebloan culture found in Chaco Canyon, New Mexico, may depict the supernova. The crescent is the Moon, the star shape to the left is the supernova, and a life-size hand print is thought to indicate that the site is sacred. Calculations of the Moon's orbit show that before dawn on July 5, 1054, as seen from Chaco Canyon, the thin waning crescent Moon was within 3 degrees of the supernova, and oriented as seen below.

https://commons.wikimedia.org/wiki/File:Anasazi_Supernova_Petrographs.jpg#filelinks

Supernova 1572A

Supernova 1572 first appeared in the night sky on November 2, 1572 in the constellation Cassiopeia. By November 11 it was already brighter than Jupiter. Around November 16, 1572, it reached its peak brightness at about magnitude −4.0, with some descriptions giving it as equal to Venus when that planet was at its brightest. The supernova remained visible at night to the naked eye into early 1574, gradually fading until it disappeared from view.

The supernova of 1572 is often called "Tycho's supernova", because of Tycho Brahe's publication, De nova et nullius aevi memoria prius visa stella ("Concerning the Star, new and never before seen in the life or memory of anyone"), published in 1573. Many European colleagues also observed the supernova and their observations were also included in Tycho’s publication. This supernova appeared before the invention of the telescope.

Star map of the constellation Cassiopeia showing the position of the Supernova of 1572. The supernova is identified as “I, Nova Stella”. A facsimile reprint of the original edition, 1573] Tychonis Brahe dani, die XXIV octobris A. D. MDCI defuncti, operum primitias De nova stella

Supernova 1604

Supernova 1604 appeared in the constellation of Ophiuchus on October 9, 1604 AD. It was brighter at its peak than any other star in the night sky, with an apparent magnitude of −4. Records of its sighting exist in European, Chinese, Korean and Arabic sources.

Johannes Kepler started observing it from October 17 (when the cloudy skies above him cleared) and continued observing it for a year. Because he published a book containing the observations of the supernova, De Stella nova in pede Serpentarii ("On the new star in Ophiuchus's foot", Prague 1606), it has come to be known as Kepler's Supernova.

A star map excerpt from Kepler’s book. The location of the supernova is marked by a capital N, (4 squares from left edge and 4 squares up from the bottom). Image in the public domain. https://commons.wikimedia.org/wiki/File:Kepler_Drawing_of_SN_1604.png

Supernova 1987A

In more recent history, Supernova 1987A was first spotted by telescope operator Oscar Duhalde, while on a coffee break in the middle of his night shift on February 23, 1987, at Las Campanas Observatory in Chile. The supernova was located in the Large Magellanic Cloud, which is a satellite galaxy of the Milky Way.

Its brightness peaked in May, with an apparent magnitude of +2.9. Although this supernova never got bright enough to be seen in the daytime, it could be seen in the night sky for almost a year before fading below the limit of naked eye visibility (about +6.5). It is also the most extensively studied supernova, observed by many instruments over a range of wavelengths, for a duration of years.

Two views of the Large Magellanic Cloud, before (left) and after (right) the explosion of SN 1987A. The supernova is marked by the arrow. (ESO PR Photo 08b/07)

1. Hold a class discussion as students look back at the remaining questions on the DQB. What questions can we answer? What additional questions do you have? Encourage students to independently investigate any remaining questions they have.
2. Ask students to work in their small groups and revisit their star cluster CMD from the first checkpoint of the investigation. Or, ask students to organize their star cards (or a new set of star cards) according to the axes of a CMD.
3. Provide students with each of the star cluster CMDs (not labeled).
4. Ask students to work with their groups to analyze the isochrones for each cluster and determine which CMD represents their star cluster.
5. Ask students to then explain the evolutionary state of their star cluster using the turn off point of the isochrone as their guide.
   The evolutionary states of the star clusters will vary. Explanations should include details about the mass of the main-sequence stars near the turnoff points. The lower the turnoff points, the older the star cluster.

Published ages of the four star clusters:

• NGC188 Cluster 1 9.7 Gyrs
• NGC2323 Cluster 2 8.3 Gyrs
• NGC2369 Cluster 3 9.0 Gyrs
• NGC2547 Cluster 4 7.6 Gyrs

Youngest to oldest: Cluster 4, Cluster 2, Cluster 3, Cluster 1