astr 314 : survey of astronomy - texas a&m...

ASTR 314 : Survey of Astronomy

Dr. Alexey BelyaninOffice: MIST 426

Phone: 979-845-7785Webpage: http://faculty.physics.tamu.edu/belyanin/

Email: [email protected] Office Hours: MWF 10-11:30 am, or by appointment

http://faculty.physics.tamu.edu/belyanin/astr314.html

Wednesday, January 20, 2010

http://faculty.physics.tamu.edu/belyanin/












mailto:[email protected]














Textbook:

Carroll & OstlieAn Introduction to Modern Astrophysics2nd Edition


Policies

Grading: two mid-term exams 20% each, homework 10%, quizzes 10%, final exam 40%

• Quizzes: We will use CPS clickers for all in-class quizzes and discussion. You should expect a clicker quiz or some activity using the clickers each class, starting from the week of February 1. Please don’t forget to bring your clicker.

• Weekly homework is due on Fridays at the beginning of the class, unless announced otherwise. Homework assignments will be posted online on Mondays. They will normally be taken from the textbook


• Buy clickers at MSC bookstore, UNLESS you already have one from other classes!!

• Price is around $25; you will use for other classes. Cost of registration is around $13

• Do not follow the registration procedure that you receive at the bookstore

• Do not register clickers at einstruction.com• Register clickers at http://elearning.tamu.edu/ by clicking

the button “Register your clicker for ASTR314”• You need only your clicker number which shows up when

you turn on the power• Problem with registration? Call help desk at elearning:

979-845-8300• Problem with clicker? call einstruction.com 888-333-4988

CPS clickers


http://elearning.tamu.edu

http://elearning.tamu.edu

• This is a 300-level science course, a calculus-based freshman physics course is a prerequisite. The level of math will be about the same as in PHYS 218 or 208.

• For this class, you need to be familiar with the mathematics of Freshman-level Physics including algebra, trigonometry, logarithms, vectors, and basic derivatives and integrals. You will encounter scientific notation and powers of 10 all the time.

Level of math


Remember and check unitsfor all terms in the formulas!!!

Indicate units in your homework and exams

Express all terms in correct units before plugging in the formulas

Check your answer for right unit. The numbers should make sense!

We will use metric units and some special units. See Appendix for definitions, tables, and other info.


7

Douglas Isbell Headquarters, Washington, DC Sept. 30, 1999 (Phone: 202/358-1753) Mary Hardin Jet Propulsion Laboratory, Pasadena, CA (Phone: 818/354-5011) Joan

Underwood Lockheed Martin Astronautics, Denver, CO (Phone: 303/971-7398) RELEASE 99-113

MARS CLIMATE ORBITER TEAM FINDS LIKELY CAUSE OF LOSS A failure to recognize and correct an error in a transfer of information between the Mars Climate Orbiter spacecraft team in Colorado and the mission navigation team in California led to the loss of the spacecraft last week, preliminary findings by NASA's Jet Propulsion Laboratory internal peer review indicate. "People sometimes make errors," said Dr. Edward Weiler, NASA's Associate Administrator for Space Science. "The problem here was not the error, it was the failure of NASA's systems engineering, and the checks and balances in our processes to detect the error. That's why we lost the spacecraft." The peer review preliminary findings indicate that one team used English units (e.g., inches, feet and pounds) while the other used metric units for a key spacecraft operation. This information was critical to the maneuvers required to place the spacecraft in the proper Mars orbit. "Our inability to recognize and correct this simple error has had major implications," said Dr. Edward Stone, director of the Jet Propulsion Laboratory. "We have underway a thorough investigation to understand this issue."

NASA PRESS RELEASE 09/30/1999


Why astronomy is fun to study and to teach

• In every lecture, we reach the frontier of human knowledge

• Crossroads of physics, chemistry, biology, philosophy, …

• Breakthrough discoveries occur every year. The golden age of astronomy and astrophysics!

• All scales from elementary particles (10-15 m) to the Hubble radius (1026 m) are involved; all timescales from 10-43 s to 1010 years

• No need in sophisticated tools to do observations and make discoveries


Course Outline

• History of astronomy. The celestial sphere.

• Physics of astronomy and cosmology: Kepler’s and Newton’s laws, Interaction of light and matter, Theory of Relativity.

• Formation and evolution of structures in the Universe: stars, galaxies, clusters of galaxies.

• Our Universe as a whole: evidence for Dark Matter, Dark Energy, Expansion of the Universe and the Big Bang


Asking right questions and analyzing the evidence

• What do we know?

• How do we know it?


• Is the Sun or the Earth the center of the Universe ? If not, where is the center of the Universe ? Does it have a center?

• How big is the Earth ? How far away is the Sun ? The nearest Star ? The center of the galaxy ? The nearest galaxy ? How big is the Universe ?

• How old is the Earth ? How old is the Sun ? How old is the Galaxy ? How old is the Universe ? How did all these things form ?

• What is a black hole ? Dark Matter ? Dark Energy ?

• What is the fate of the Universe ?

• How do you know these things ?


Our place in the Universe

• As we see it now

• As believed by ancient observers


1024 m ~ 100 million light-years

106 m

1012 m

1026 m ~ 10 billion light-years

1022 m ~ 1 million light-years1021 m ~ 100,000 light-years


Distances and scales in Astronomy are really astronomical !

The average distance from the Sun to Neptune is 4 trillion meters (2793 million miles).

The nearest star (other than our Sun), Alpha Centauri, is 4.23 light years away; roughly 4 x 1016 meters (~30 trillion miles !)

If you scaled the Solar System down to the size of a football field, the Sun would be on the 50 yard line and Neptune would be in the End Zone. Alpha Centauri would be more than 300 miles away - more than twice the distance from Texas A&M to Dallas !


Need to introduce new units of distance

1 astronomical unit (AU) = 1.5 x 1011 m

1 light-year (ly) ≈ 1016 m

1 ly = c×1 year (the distance the light travels in 1 year)

Velocity of light in vacuum c = 3 ×108 m/s1 year ≈ 3.1 × 107 s

1 parsec (pc) ≈ 3.26 ly ≈ 3 ×1016 m

1 kpc = 1000 pc;1 Mpc = 1 million pc;1 Gpc = 1 billion pc


Huge isolation of stars:

Distance between stars

1 astronomical unit~ 106

The time needed to reach Proxima with modern spacecrafts:

•Currently the travel to stars is impossible•Looking through space = travel in time!


Local Bubble

Density ~ 0.05 atoms/cm3

Temperature ~ 105 K

Remnant of supernovaexplosion?


1024 m ~ 100 million light-years

106 m

1012 m

1026 m ~ 10 billion light-years

1022 m ~ 1 million light-years1021 m ~ 100,000 light-years


Contents of the Universe

• 97% of all ordinary (baryonic) matter is in stars

• Only 3-5% of matter in the Universe is baryonic!

• 27% is cold dark matter

• 70% is dark energy


Historical notes


Slide

• Already in the stone and bronze ages, human cultures realized the cyclic nature of motions in the sky.

• Observations of stars, sun, moon, and planets were used in navigation and time keeping, and for mystical purposes (astrology)

• Monuments dating back to ~ 3000 B.C. show alignments with astronomical significance.

• Those monuments were probably used as calendars or even to predict eclipses.

Historical CosmologyCosmology : the science of the origin and development of the universe.


Ancient AstronomyObservations of sun, moon, stars, and planets

formed the basis for timekeeping, and navigation.

Stonehenge in southern England: stones are aligned with rising Sun of the Summer Solstice

Stonehenge upon its completion around 1600-1500 B.C.

Stonehenge ruins today


Slide

Other Examples All Over the World

Caracol (Maya culture, approx. A.D. 1000)Wednesday, January 20, 2010

Anasazi Native Americans occupied Colorado Plateau from ~100-1100 AD. Used Sun Dials to mark equinoxes.

Fajada butte in Chaco Canyon, New Mexico

Anasazi Sun dials near top of butte




Anasazi Sun dials at noon on Winter Solstice

Anasazi Sun dials at noon on Summer Solstice -the “Sun dagger”.




Aryabhata the Elder Born: 476 in Kusumapura (now Patna), IndiaDied: 550 in India

Most accurate value of Pi among ancients!Add four to one hundred, multiply by eight and then add sixty-two thousand. the result is approximately the circumference of a circle of diameter twenty thousand. By this rule the

relation of the circumference to diameter is given. This gives π = 62832/20000 = 3.1416 which is a surprisingly accurate value:

π = 3.14159265 correct to 8 places!Aryabhata gives a systematic treatment of the position of the planets in space. He gave the circumference of the earth as 24 835 miles, which is an excellent approximation to the currently accepted value of 24 902 miles. He believed that the apparent rotation of the heavens was due to the axial rotation of the Earth. This is a quite remarkable view which later commentators could not bring themselves to follow and most changed the text to save Aryabhata from what they thought were stupid errors!

Aryabhata believes that the Moon and planets shine by reflected sunlight. He correctly explains the causes of eclipses of the Sun and the Moon.

Aryabhata calculated the Sidereal day (the rotation of the earth against the fixed stars) as 23 hours 56 minutes and 4.1seconds; the modern value is 23:56:4.091. Similarly, his value for the length of the sidereal year at 365 days 6 hours 12 minutes 30 seconds is only 3 minutes 20 seconds longer than the true value (over 365 days).


Arab scienceScience in Islamic world was built on the sciences of two great cultures, the Greek and the Indian. Blending and expanding these often different ideas led to a new science which later profoundly influenced Western scientific exploration beginning in the Renaissance.

Al-Khwarizmi (9th century), the inventor of algebra. He based the system on the Indian numbers borrowed by the Arabs (what we today call Arabic numerals). Detailed positions of the sun and planets, detailed map of the world.

Omar Khayyam was a great Persian scientist, philosopher, and poet who lived from 1048-1131. He made outstanding contributions to mathematics (general theory of cubic equations, conic sections, non-euclidean geometry, Pascal triangle, etc. ) He was ahead of his time by at least 500 years. He compiled many astronomical tables and performed a reformation of the calendar which was more accurate than the Julian and came close to the Gregorian. An amazing feat was his calculation of the year to be 365.24219858156 days long, which is accurate to the 6th decimal place! Actually, 6th decimal place changes over a person’s lifetime.


Samarkand: Marco Polo’s “most perfectly beautiful city”


Ah, make the most of what we yet may spend,Before we too into the Dust Descend;Dust into Dust, and under Dust, to lie,Sans Wine, sans Song, sans Singer and--sans End!

For I remember stopping by the way To watch a Potter thumping his wet Clay: And with its all-obliterated Tongue It murmur'd--"Gently, Brother, gently, pray!"

But helpless Pieces of the Game He plays Upon this Chequer-board of Nights and Days; Hither and thither moves, and checks, and slays, And one by one back in the Closet lays.

Translation by E. Fitzgerald, 1859


Slide

Chinese astronomers: kept careful track of all events in the sky

First observation of solar eclipse: 2136 BC!

“Guest starts”: comets, novae, supernovae, and other transientsStill scientifically important!

During Europe's Dark Ages, the flourishing civilization in China, as well as those in Arabia and India, achieved major advances in science, technology, medicine, mathematics and astronomy. China invented paper, gunpowder and the compass. The Chinese printed books using movable type in 1050.


Slide

Comet Halley

can be traced back to 240 BC or even to 1059 BC in Chinese records

Period 76 yr;Last appearances: 1986, 1910Expected: 2061


Slide

Crab nebula Supernova in Taurus July 4, 1054

"In the 1st year of the period Chih-ho, the 5th moon, the day chi-ch'ou, a guest star appeared... After more than a year it gradually became invisible..."


Slide

Western scientific history begins with the ancient Greek civilization about 600 BCE


Slide

• Found in 1901 near the Antikythera island in a Roman shipwreck dated 80 BC• Remained a puzzle for over 100 years • Recently deciphered using X-ray tomography, optical imaging, texture mapping

Nature, 30 November 2006 (page 587)


Slide

A sophisticated mechanical computer


Slide

Predicts:• Lunar and solar cycles, taking into account ellipticity of the moon’s orbit• Lunar and solar eclipses• Accurate positions of the sun, moon, and planets• Luni-solar calendar

Next time when much simpler mechanisms of this kind appeared was in Islamic countries in 1300 AD (Al Biruni)Later they were imported to Europe and became clock mechanisms


astr 314 : survey of astronomy - texas a&m...

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