General Astronomy lecture note, Lecture notes of Physics

Download General Astronomy lecture note and more Lecture notes Physics in PDF only on Docsity!

General Astronomy

Phys

JU CNSs

Course Outline

Chapter 1: Introduction and History of Astronomy (7 hours)

1.1. The nature of Science and Astronomy

1.2. Numbers in Astronomy

1.3. The Universe at a glance

1.4. Observing the sky

1.5. Ancient history of Astronomy

1.6. Astrology versus Astronomy

1.7. Birth and development of modern Astronomy

1.8. Astronomical objects, distances, and sizes

1.9. Overview of celestial mechanics

Chapter 2: The Earth, moon, and the sky (6 hours)

2.1. Locations on Earth

2.2. Locations on the sky

2.3. The Earth's motions and seasons

2.4. Timekeeping and Calendars

2.5. Phases of the moon

2.6. Solar and lunar eclipses

Chapter 5: Stars and their evolution (7 hours)

• 5.1. Luminosity and brightness of stars
• 5.2. Colors and temperatures of stars
• 5.3. Spectral classes
• 5.4. Stellar distances
• 5.5. Proper motion
• 5.6. The mass determination and the mass-luminosity relation
• 5.7. The Hertzsprung-Russel (HR) diagram
• 5.8. The Main-Sequence (MS) stars
• 5.9. Evolution of the low-mass (<=0.5 solar mass), medium-mass (~0.5 – 8 solar

mass), and high

• mass (>8 solar mass) stars
• 5.10. White dwarfs, neutron stars, and black holes

Chapter 6: The overview Galaxies (6 hours)

• 6.1. The Milky Way galaxy
• 6.1.1. Structure and main components
• 6.1.2. Characteristics of the galaxy
• 6.1.3. Mass of the galaxy
• 6.1.4. Center of the galaxy
• 6.1.5. Stellar population

• 6.2. Other galaxies
• 6.2.1. Morphological types of galaxies
• 6.2.2. The masses of galaxies
• 6.2.3. Characterizing different types of galaxies
• 6.2.4. The Mass to light ratio
• 6.2.5. Estimating distances to galaxies
• 6.2.6. The Hubble classification of galaxies

(evolution)

Chapter 7: Introduction to Cosmology (5 hours)

• 7.1. The beginning of the universe
• 7.2. The Big Bang models of the universe
• 7.3. The expansion of the universe: a problem with age
• 7.4. The cosmic microwave background (CMB)
• 7.5. The inflationary universe
• 7.6. Dark matter and dark energy

The Nature of Astronomy

Astronomy is defined as the study of the objects that lie

beyond our planet Earth and the processes by which these

objects interact with one another.

The word “astronomy” comes from the Greek language

“ αστρονο ία μ ” which means “Stars law”, and it’s an old

science that studies celestial objects as well as the formation

and development of the universe.

It is also humanity’s attempt to organize what we learn into a

clear history of the universe, from the instant of its birth in

the Big Bang to the present moment.

• In considering the history of the universe, we will see again

and again that the cosmos evolves ; it changes in profound

ways over long periods of time.

For example, the universe made the carbon, the calcium, and the

oxygen necessary to construct something as interesting and

complicated as you.

• The size of Earth is typical of the sizes of the rocky planets, the terrestrial planets ,

but planets made mostly of gas such as Jupiter and Saturn are larger by a factor of

several to ten.

• This size scale represents the vast majority of human experience.
• Most of the satellites launched remain very close to Earth.
• The shuttle, for example, orbits at an altitude of only a few hundred kilometers — a few

percent of the radius of Earth.

• Some spacecraft are sent to other planets or to the Moon, but the majority stays at the

scale of this step in our journey.

• Although the Moon seems nearby when we consider the huge space surrounding the

Earth-Moon system,

• The Earth and Moon are really very far apart,

if we get a car and drive to moon the trip would take five

months of driving nonstop, 24 hours a day and seven days a

week.

If our jet could go to the Moon, it would take five days to get

there

Light Speed

• Light travels faster than anything else in the universe. It

has a speed of 300,000 km(186,000 miles) per

second.

• At this speed, light can travel to the Moon in just over one

second.

• This distance, the distance light travels in one second, is

called a light-second.

• As we go further we reach other planets, encompass the bulk of

the Solar System , the system comprising the Sun and all of the objects

orbiting around it.

• This size scale is about five billion kilometers across, 30 times the

distance between the Earth and the Sun.

From where this all comes from

different views?

• For time immemorial, humans have been interested by

creation.

• Where did we, and the universe in which we live, come

from?

• In the Rig Veda , it was proposed that before

creation there was ”neither existence nor non-

existence.” The Latin phrase ex nihilo nihil fit

(”out of nothing comes nothing”) sums up

current human beliefs about origins.

• The Qur’an contains the following verse regarding the

origin of the universe:

• “Do not the Unbelievers see that the heavens

and the earth were joined together (as one

unit of Creation), before We clove them

asunder?” [Al-Qu’ran 21:30]

• Many possibilities have been

considered by scientists over the

millennia.

• Did the universe ”happen” suddenly,

was it created quickly by God, has it

existed forever, or is it in a constant

state of creation, even now?

• There are two schools of thought on how the

Universe formed: ”top down” and ”bottom

up”.

• Top down theorists think that large

clusters formed after the Big Bang, which

later broke down into stars and galaxies.

• ”Bottom up” theorists instead pose the

theory that matter was originally dispersed

fairly evenly by the Big Bang, later

accumulating into stars and galaxies.

• Recent data from Hubble Deep Field

photographs appear to support ”bottom up”

theories. The photos show young galaxies from up to

11 billion light-years away.

• Since only hydrogen and Helium gas

were formed during the big bang,

everything heavier than that had to be

made in stars later.

• These other elements — all of the

elements on the periodic table —were

made in stars.

The Big Bang event is a physical theory that describes how the

universe expanded from an initial state of high density and

temperature

• Today, many billions of years later, the universe has

evolved into a more hospitable place for life.

• Tracing the evolutionary processes that continue to

shape the universe is one of the most important (and

satisfying) parts of modern astronomy.