scdggdcg

1. The Creation of the
Elements and the
Relationship to
Cosmic Events in the
Universe

2. The Big Bang
 The Big Bang Theory is the accepted scientific
theory about the origin of the universe based
upon multiple lines of evidence.
 The “Big Bang” was a phenomenally energetic
explosion that initiated the expansion of the
universe.
 All matter and energy were compressed at a
single point (singularity) at the time of the
explosion
 We do not know what was before…..?
 The age of the universe is calculated at 13.7
billion years (based on multiple methods of age
dating based on empirical data).

3. The Big Bang vs. the
Steady State Model
 The Big Bang (1931) was first proposed by an Belgian
cosmologist and priest named George LeMaitre based on
theoretical calculations and astronomical measurements
of distant galaxies (by Edwin Hubble) that demonstrated
that the universe is expanding.
 The competing theory was the Steady State Model (1948)
which said that on the large scale the universe has always
looked the same and that there was no beginning and is
no end. To account for the observed expansion of the
universe, it required that matter to be continuously created
to fill gaps that would be created
by an expanding universe.

4. Scientific Evidence for the
Big Bang Theory
 The Red Shift of Distant Galaxies
(Hubble, 1927)
 The Cosmic Elemental Abundances of
Hydrogen and Helium and Big Bang
Nucleosynthesis
(Alpher and Gamow, 1948)
 The Cosmic Microwave Background (CMB)
Radiation
(Penzias and Wilson, 1964)

5. Red Shift is Evident in
Emission Spectra of Light
from Stars and Galaxies

6. Hubble’s Law and Red Shift
 Everything in the universe is moving away from
everything else (Raisin bread analogy).
 We are not at the center of the universe.
 Edwin Hubble discovered that distant galaxies
are moving away from us at rates faster than
closer galaxies are moving away from us.

7. Cosmic Elemental
Abuandances
 Hydrogen (74%) and Helium (24%) are
the most abundant elements in the
universe.
 Stellar nucleosynthesis alone cannot
account for the large amount of Helium.
(can only account for about 2%)
 Big Bang nucleosynthesis calculations
accurately predict the present cosmic
abundances of hydrogen and helium.

8. Big Bang Nucleosynthesis
 All Hydrogen and most Helium in the universe was
produced during the Big Bang Event, starting ~100
seconds after the explosion. A small amount of Lithium
was also produced.
 Big Bang nucleosynthesis ceased within a few minutes
because the universe had expanded sufficiently by
then such that the temperatures and pressures were
too low to support additional fusion reactions.

10. Cosmic Microwave
Background Radiation
 There is a background signal of microwave radiation emitted
by the universe. It comes from the light energy given off
during the “Big Bang” explosion.
 It can be detected no matter which direction you point an
antennae in the sky, at any time, day or night.
 It was discovered by accident by two astronomers (Penzias
and Wilson) working at Bell Labs in New Jersey in 1964.
Penzias and Wilson won
the Nobel Prize in Physics
in 1978 for their discovery.

11. Cosmic Microwave
Background Radiation
 Due to the cosmic background microwave radiation, the
remnant radiation left over from the Big Bang, the universe
has an ambient temperature of 3K.
 The CMB radiation is remarkably uniform in its distribution.
It has been mapped by the COBE (Cosmic Background
Explorer) satellite.

12. Stellar Nucleosynthesis
 Stars create elements by combining lighter nuclei into heavier
nuclei via nuclear fusion reactions in their cores.
 Enormous temperatures (15,000,000 K), pressures, and densities
of matter are needed to initiate fusion (thermonuclear) reactions.
 The basic nuclear reaction in the Sun converts hydrogen to helium
and releases energy in the form of electromagnetic radiation. This
is why stars shine!

13. Stellar Nucleosynthesis
 Larger stars can fuse heavier elements.

14. Supernova Nucleosynthesis
 Elements heavier than Iron are made primarly
when giant stars explode in supernova events.

15. A summary…
(you are made of stardust)

16. The Life Cycles of Stars

17. Nebulae
 Nebulae are regions
of gas and dust in
interstellar space
within galaxies.
 Nebulae contain gas
and dust from
previously exploded
stars.
 Nebulae are the
birthplaces of new
stars. (recycling!)
 When stars form,
planets may form
too (a solar system)

18. Nebulae (continued)
The image,
roughly 3
light-years
across, was
taken May 29-
30, 1999, with
the Wide Field
Planetary
Camera 2. The
colors in the
image
represent
various gases.
Red
represents
sulfur; green,
hydrogen; and
blue, oxygen.

19. Main Sequence Stars
The Hertzsprung-Russell (H-R) Diagram shows that there is some
relationship between the temperature and luminosity (brightness) of a
star. The clustering indicates something about how stars change over
time. Young-middle age stars always plot on the main sequence.

20. Main Sequence Stars
Main sequence stars
fuse hydrogen to
helium.

21. Red Giants and White Dwarfs
V838 Monocerotis – Red Giant
NGC 6369 – Planetary
Nebula with White Dwarf

22. Supernovae
The Crab Nebula – Supernova Remnant
Observed 1000 years ago.
The Veil Nebula – 5000 to
10000 years old; in our
galaxy

23. Neutron Stars and Black
Holes