Constellation | Characteristics of Stars | Grade 9 Science Quarter 3 Week 7-8 Lesson

Key Concepts:

• Stars: Brightness, color, surface temperature, size, mass, nebulae
• Constellations: Patterns of stars, Orion, Taurus, Scorpius, Virgo, Pegasus, IAU, Zodiacs
• Earth's Revolution and Rotation: Impact on constellation visibility

1. Characteristics of Stars

• A star is a natural luminous body, a huge sphere of hot, glowing gas.
• Stars are fundamental building blocks of galaxies.
• Five basic characteristics define a star: brightness, color, surface temperature, size, and mass.

1.1 Brightness

• Brightness depends on size and temperature: larger and hotter stars shine brighter.
• Apparent brightness: Brightness seen from Earth.
• Absolute brightness: Brightness if all stars were at the same distance.
• A hot, large star far from Earth may not appear very bright.

1.2 Color and Temperature

• Star color ranges from red to blue, indicating surface temperature.
• Table of star colors and temperatures:
  • Proxima Centauri (Red): 2,300°C
  • Sun (Yellow): 5,700°C
  • Epsilon Eridani (Orange): 4,600°C
  • Vega (White): 9,800°C
  • Sirius (White): 10,000°C
  • Alnilam (Blue): 27,000°C
• Coldest stars appear red, hottest stars appear blue.

1.3 Size

• Stars vary in size: medium-sized (like the Sun), white dwarfs (size of Earth), red giants and supergiants (large enough to fill the solar system up to Jupiter).

1.4 Mass

• Star's life cycle depends on its initial mass.
• Low mass stars: Survive for billions of years, die quietly, leaving a white dwarf.
• High mass stars: Survive for a few million years, die in a supernova explosion, leaving a black hole.

1.5 Origin

• Stars originate from huge clouds of gas and dust called nebulae.

2. Constellations

• Constellations are imaginary patterns of stars grouped together.
• Stars in a constellation appear close from Earth but may be very distant from each other.
• Many constellation names originate from early Babylonian and Greek civilizations.
• Different cultures have different names for constellations.

2.1 Examples of Constellations

• Orion the Hunter: Prominent in the night sky during winter. Known as "Tatlong Maria" or "Tres Marias" in Christian Filipino culture.
• Taurus: Visible during summer in the Philippines.
• Scorpius: Resembles a scorpion.
• Virgo: Resembles a woman.
• Pegasus: Resembles a winged horse.

2.2 Constellation Visibility

• Some constellations are not visible at certain months due to the Earth's revolution.
• As Earth revolves, stars concealed by the sun in previous months become visible.

2.3 International Recognition

• The International Astronomical Union (IAU) recognizes 88 constellations.

2.4 Zodiac Signs

• Zodiacs are 12 constellations.

3. Earth's Revolution and Rotation

• The Earth's revolution is responsible for the fact that we can see different parts of the sky at different parts of the year.
• The Earth's rotation causes constellations to appear to move across the night sky from east to west.

4. Synthesis/Conclusion

Stars vary in brightness, color, size, and mass, originating from nebulae. Their characteristics are key to understanding their life cycles. Constellations are patterns of stars that appear to move across the sky due to Earth's rotation and have varying visibility throughout the year due to Earth's revolution. The IAU recognizes 88 constellations, including the 12 zodiac constellations.