1. Galaxies, Nebulae, and Stars

2. TEKS 8.8A describe components of the universe including stars, nebulae and galaxies, and use models such as the Herztsprung-Russell diagram for classification TEKS 8.8B recognize that the Sun is a medium-sized star near the edge of a disc-shaped galaxy of stars and that the Sun is many thousands of times closer to the Earth than any other star

3. We live in a galaxy called the Milky Way. A galaxy is a system of stars, planets gas, dust and dark matter.

5. Within galaxies are star forming regions called nebula. A nebula is a cloud of dust, hydrogen and helium gases.

6. It is in these clouds of gas and dust that stars sometimes form.

7. A star is a large ball of gases that generates its own energy through nuclear fusion.

8. Fusion is a process in which hydrogen and helium fuse to form heavier elements.

9. This process generates large quantities of energy.

10. The energy is emitted from the star in the form of heat and light.

11. Stars undergo many changes through their evolution.

12. Depending on the mass of the star, its lifetime may be a few million years to trillions of years. Lower massed stars can generate energy for billions of years.

13. Stars that are very massive generate energy for only a few million years.

14. Nebula with protostars Stellar Evolution

15. Over the course of the star’s evolution the energy generated by the star begins to decrease.

16. Ultimately, the star will no longer have enough hydrogen or helium to continue to radiate.

17. Our Sun is only one of many stars in the universe.

18. It is considered to be a medium- sized star near the edge of our disc-shaped galaxy.

19. So what will happen to our Sun?

20. At the end of the sun’s life, it will gradually brighten, as it has been doing for the last 4 billion years.

21. Around 5,000,000, 000 AD, the hydrogen in the Sun’s core will run out.

22. The sun will expand into a red giant about three times larger than it is now.

23. The increased brightness will boil the oceans and raise our temperatures to over 1000 Kelvin.

24. Eventually, the Sun will shrink, but then expand again, charring the surface of the earth with solar prominences.

25. If earth isn’t destroyed, it will become a cold, dark chunk of rock circling a white dwarf.