Astronomy Honor - Advanced

Nature Study

Requirements

1. Have the Astronomy Honor.
2. How are the apparent daily movements of the stars explained?

   Answer: The apparent daily movement of the stars (which seem to rotate from east to west during the night) is NOT real: it is caused by the ROTATION of the Earth on its own axis, from west to east, every 24 hours. Because we are rotating, the entire sky appears to move in the opposite direction. — It is not the stars that move: it is the Earth that rotates — that is why the sky seems to parade from east to west.

3. Give the meaning of the following terms: planet, satellite, comet, meteor, nebula, fixed star, and sunspot.

   Answer: • Planet: a body that orbits a star and has no light of its own. • Satellite: a body that orbits a planet (e.g., the Moon). • Comet: a body of ice and dust that, as it approaches the Sun, forms a tail. • Meteor: the luminous trail ('shooting star') of a body that enters the atmosphere and burns up. • Nebula: a cloud of gas and dust in space. • Fixed star: a star so distant that its position appears not to change (unlike planets, which 'wander'). • Sunspot: a darker, cooler region on the Sun's surface, linked to magnetic activity. — These terms are the basic vocabulary of the sky — distinguishing planet, satellite, comet, and meteor is essential.

4. What do the terms mean: celestial sphere, celestial pole, celestial equator, horizon, right ascension, declination, transit, conjunction, and ecliptic?

   Answer: • Celestial sphere: an imaginary sphere surrounding the Earth, on which the stars appear to be fixed. • Celestial pole: the extension of the Earth's axis onto the celestial sphere (north and south). • Celestial equator: the projection of the Earth's equator onto the sky. • Horizon: the line where the sky meets the Earth. • Right ascension: celestial 'longitude' (measured in hours). • Declination: celestial 'latitude' (in degrees). • Transit: the passage of a celestial body across the highest point (the meridian). • Conjunction: when two celestial bodies appear together/aligned in the sky. • Ecliptic: the apparent path of the Sun across the sky throughout the year. — These are the 'coordinates' and reference lines of the sky, which make it possible to locate and describe the position of the stars.

5. Explain the main differences between refracting and reflecting telescopes. Describe the mounting of an equatorial telescope.

   Answer: • Refractor: uses LENSES to capture and focus light (like a spyglass). • Reflector: uses (concave) MIRRORS for this, and is generally cheaper at large apertures. Differences: the refractor gives sharp images, but becomes expensive and heavy in large sizes; the reflector captures more light for less cost, but requires more maintenance. • Equatorial mount: has one of its axes aligned with the Earth's axis (pointed at the celestial pole), allowing it to follow the movement of the stars by rotating only one axis — ideal for tracking stars and for photography. — A refractor uses lenses; a reflector uses mirrors. The equatorial mount tracks the rotation of the sky by moving only one axis.

6. Into what colors is sunlight broken down when it passes through a prism? How are the colors of stars used to indicate their temperatures?

   Answer: 1) The colors into which sunlight is broken down when passing through a prism: the colors of the rainbow — red, orange, yellow, green, blue, indigo, and violet. 2) How the colors of stars indicate their temperatures: the color reveals the surface temperature — blue and white stars are the hottest; yellow ones (like the Sun) have an intermediate temperature; and orange and red ones are the coolest. — The prism reveals the colors of light; and a star's color is its 'thermometer' — blue is hot, red is cooler.

7. What is the relationship between the ecliptic and the vernal and autumnal equinoxes? What dates are normally associated with the equinoxes?

   Answer: The ecliptic is the apparent path of the Sun across the sky during the year; it crosses the celestial equator at two points — the equinoxes. At an equinox, day and night have equal lengths. The dates are around March 20-21 and September 22-23. (In the Southern Hemisphere, March marks the autumnal equinox and September the vernal equinox — reversed relative to the North.) — At the equinoxes (March and September), the Sun crosses the celestial equator and day equals night.

8. Learn and point out the constellations that are symbols of spring and autumn in the Southern Hemisphere.

   Answer: In the Southern Hemisphere, on spring nights constellations such as Sagittarius and Scorpius (in the west) stand out, along with the rising of Taurus and Orion in the east; in autumn, the Southern Cross (Crux), Centaurus, and Leo stand out high in the sky. The 'seasonal' constellations are those that appear at the beginning of the night at that time of year. — Each season has its prominent constellations at the beginning of the night — recognizing them helps to 'read' the sky throughout the year.

9. Name and point out in the sky the constellations that can be seen all night long on a clear night in the Southern Hemisphere.

   Answer: The southern circumpolar constellations are visible all night long (they do not set), rotating around the south celestial pole. The main ones are: the Southern Cross (Crux), Centaurus, Carina, Vela, and Musca (the Fly), among others near the south celestial pole. — The southern circumpolar constellations, such as the Southern Cross, never set — they spend the whole night rotating around the pole.

10. Give the names of five constellations that are visible between sunset and midnight, in the Southern Hemisphere, during:
    • Summer months.
    • Winter months.

    Answer: 1) Meses de verão (no hemisfério sul, de dezembro a março), entre o pôr do sol e a meia-noite: Órion (Orion), Touro (Taurus), Cão Maior (Canis Major), Cão Menor (Canis Minor) e Lebre (Lepus). 2) Meses de inverno (no hemisfério sul, de junho a setembro), entre o pôr do sol e a meia-noite: Escorpião (Scorpius), Sagitário (Sagittarius), Cruzeiro do Sul (Crux), Centauro (Centaurus) e Lira (Lyra), quando o centro da Via Láctea fica bem visível. — The sky changes with the seasons: Orion dominates the summer; Scorpius and the center of the galaxy dominate the winter in the Southern Hemisphere.

11. At what time of year is the constellation Orion best seen? Give the names of and locate in the sky the three brightest stars of this constellation.

    Answer: In the Southern Hemisphere, Orion is best seen in the SUMMER months (December to March), at night. Its most notable stars: Rigel (blue, in the 'foot'), Betelgeuse (reddish, in the 'shoulder'), and the Three Marys — the belt formed by Alnitak, Alnilam, and Mintaka. — Orion shines in the southern summer; Rigel, Betelgeuse, and the Three Marys are its hallmarks in the sky.

12. How are the letters of the Greek alphabet used to name the stars of a constellation? Give 5 examples of the use of Greek alphabet letters to name stars.

    Answer: 1) How Greek letters name the stars of a constellation: the stars are given letters of the Greek alphabet in decreasing order of brightness (the brightest is Alpha, the second Beta, and so on), followed by the Latin name of the constellation in the genitive case. 2) Five examples: Alpha Centauri, Beta Centauri, Alpha Crucis (the brightest in the Southern Cross), Alpha Orionis (Betelgeuse), and Beta Orionis (Rigel). — Alpha is the brightest in the constellation, Beta the second, and so on — a system created by Johann Bayer.

13. Locate, as they appear during the year, the 15 first-magnitude stars.
14. Using a diagram, demonstrate the relative positions of the Earth and Moon during high and low tides.
15. Regarding the planets of the solar system, answer:
    • Give 2 distinctive characteristics of each of the planets in this system.
    • Which of these planets cannot be seen without the aid of a telescope?
    • 2 of these planets are seen near dawn or near dusk. Which planets are these?

    Answer: 1) Two characteristics of each planet: Mercury: it is the smallest planet and the closest to the Sun. Venus: it is the hottest (an intense greenhouse effect) and the brightest in the night sky. Earth: it is the only one with confirmed life and with liquid water on its surface. Mars: it is the "red planet" and has polar ice caps. Jupiter: it is the largest planet and has the Great Red Spot. Saturn: it is famous for its rings and is the second largest. Uranus: it rotates practically "on its side" (a very tilted axis) and has a bluish color. Neptune: it is the most distant, of an intense blue color and with the strongest winds in the solar system. 2) The planets that CANNOT be seen with the naked eye, requiring a telescope, are Uranus and Neptune (the others — Mercury, Venus, Mars, Jupiter, and Saturn — are visible without an instrument). 3) The two planets seen near dawn or dusk are Venus and Mercury; because they are inner planets (closer to the Sun than the Earth), they always appear low on the horizon, just after sunset or shortly before sunrise. — Each planet has its hallmark; Uranus and Neptune only with a telescope, and Venus and Mercury appear at dawn or dusk.

16. Build a sundial and know how to tell time with it.
17. Where and in what way does the Bible refer to Orion, the Pleiades, and Arcturus?

    Answer: The Bible mentions these stars and constellations mainly in Job and Amos: Job 9:9 and Job 38:31-32 mention Orion, the Pleiades (the 'Seven Stars'), and the Bear/Arcturus (in some translations); and Amos 5:8 speaks of the one who 'made the Seven Stars and Orion.' These passages present God as the Creator and sustainer of the stars. — In Job 38:31-32 and Amos 5:8, the Bible mentions Orion and the Pleiades — pointing to God as the Creator of the heavens.

18. Discuss the statement made in Early Writings, p. 41, regarding the opening in Orion.