KNOWLEDGE I WANT YOU TO “GET”

FROM TODAY’S CLASS MEETING

ASTR 105G Class Meeting #42 Wed, May 4th

i) An Extrasolar Planet announcement from Monday, May 2nd – a brief Space.com story to read

ii) discuss some additional (won’t be on the Final Exam!) fun topics:

BLACK HOLES, ALIENS, terraforming Mars…

iii) conduct some EXAM REVIEW exercises

NEWS ITEMS:

1) SCHEDULE OF REMAINING CLASSES:

TODAY: Wednesday, April 29th: i) Earth-like planets(?) orbiting a dim red star located ~40

Light Years (2.5 million AU) from the Sun - ‘other topics’ that there are usually of interest …

ii) review for the Final Exam

FRIDAY, May 6th: i) answer any questions in prep for FINAL EXAM

ii) a few Exercises in Prep for FINAL EXAM

MONDAY, MAY 9th, 10:30 AM: FINAL EXAM

5 DAYS FROM TODAY !!!

Final Exam: 10:30 AM, Monday, May 9th

HERE IN CLASSROOM Biology Annex Room 102

NO SCANTRON SHEET WILL BE NEEDED !!

A “FINAL EXAM” STUDY GUIDE has been distributed (is available online)

EXAM #1 and EXAM #2, and Quizzes #1-7,

will be very valuable study guides for the Final Exam, as are the in-class exercises we have

conducted AND YOUR LABS !!!

BONUS Homework #5

The online (via the CANVAS page for this course)

COURSE EVALUATION

Link will be available through Sunday night (May 8th)

Assignment Description is available in

printed form here in class or online in the HOMEWORK folder at the class website

THERE IS NOW AVAILABLE via the CANVAS System (http://learn.nmsu.edu) an ON-LINE COURSE EVALUATION for this course and Instructor (ASTR 105G, M01, or M02, or M03) . You should see evidence of this EVALUATION opportunities when you log-on to CANVAS. Your comments are and will remain ANONYMOUS. I will GREATLY appreciate your taking the time to complete the evaluation to let me know what aspects of this course could benefit from change/improvement, what aspects of this course work/should not be changed, what course aspects should be dropped or added, etc. Your comments are very helpful in constructing as good a class as I can deliver. If you have any trouble accessing the COURSE EVALUATIONS for this class via CANVAS, let me know. IF 60% of you complete the Evaluation no later than Sunday, May 8th, a BONUS 1.0 points will be added to Semester Grades for ALL of you in the form of 35 BONUS Homework points Regards, Dr. Murphy murphy@nmsu.edu 575-646-5333

I will VERY MUCH appreciate obtaining your feedback about this class via the on-line COURSE EVALUATION FORM system described in the document that has been distributed in printed form. This is an anonymous system so your name will not be connected to your comments. I am interested in learning what attributes of this course presentation I could change to improve the delivery/material covered, and what attributes seem to work for you in their current form/delivery style.

I do appreciate the time you are willing to spend on this effort.

Thanks !!

Here in class Mon, May 2nd we discussed EXTRASOLAR Planets, .. planets that are orbiting stars other than the Sun A Space.com news story at 10:30 AM MDT day declared that several newly discovered Extrasolar Planets orbiting a star located 39 Light Years from the Sun MIGHT be in the dim, red star’s Habitable Zone http://www.space.com/32761-three-alien-planets-trappist-1-star-could-support-life.html You have today been given a printed 2-page copy of this Space.com (author: Charles Choi) story, with added comments indicating where a number of the processes we have discussed this semester are applicable to understanding the details of this interesting planetary system connected to the star TRAPPIST-1

Interpretation / analysis of the star TRAPPIST-1 & its 3 detected orbiting planets makes use of:

- Kepler’s 3rd Law - Newton’s modified form of Kepler’s 3rd Law - Wiens’ Law - Stefan-Boltzmann Law - Transit method of Extrasolar Planet detection - Gravity

BRIGHT Stars The star TRAPPIST-1 is cooler (colder photosphere than the Sun’s photosphere) and dimmer than the Sun (both because it is colder and smaller than the Sun)

HOT Stars COLD Stars

DIM Stars

The Sun

TRAPPIST-1 star

Maybe future news articles will provide information about new knowledge regarding TRAPPIST-1’s three planets…. and maybe those articles will address any evidence about LIFE on one of these planets !!!

NOW, Let’s complete Parts II & III of the Exercise begun here in class Monday, May 2nd

COMETS / Parts, Positions

SEASONS / Axis Tilt

Let’s now discuss some other ‘astronomy’ topics…. These WILL NOT be included

on the Final Exam BLACK HOLES: not an exam topic !!

What are they? Can we ‘see’ them?

http://cosmology.berkeley.edu/Education/BHfaq.html A BLACK HOLE is simply an object that is massive enough (importantly, dense enough)

that its Surface Gravitational ESCAPE VELOCITY

is greater than the SPEED of LIGHT

(escape velocity greater than 3 x 108 meters per second,

or ~186,000 miles per second)

The ESCAPE VELOCITY of an object is the speed at which the

KINETIC ENERGY of an object:

KE = ½ x MASSOBJECT x SPEED2 is equal to an object’s

GRAVITY POTENTIAL ENERGY:

POTGRAV = G MASSOBJECT MASSCENTRAL DISTANCE

SO:

VESC = 2 G MCENTRAL / DISTANCE VESC at their surfaces:

Earth: VESC = 11,000 meters per second (~ 22,000 miles per hour)

Sun: VESC = 618,000 meters per second (6.18 x 105 m/s = 1,200,000 mph)

Neither of these speeds is within even 0.25% of the speed of light, so light (radiant energy) has no trouble ‘escaping’ from either the Sun or Earth in their current sizes……

What about if we start to shrink the Sun...

If we shrink the Sun’s radius by half (but retain all of the mass!!), the Sun’s escape velocity at its New Surface increases, so:

½ SUN: VESC = 9.63 x 105 meters per second

1/4 SUN: VESC = 1.36 x 106 meters per second

1/1000 SUN:VESC = 2.15 x 107 meters per second

3-km SUN: VESC = 3 x 108 meters per second

For a 3-km radius (6 km diameter) Sun, its density would be ~ 1.6 x 1016 grams per cubic centimeter !!!!!

SO: As the Sun shrinks, the ESCAPE

VELOCITY AT ITS SHRINKING SURFACE increases BUT

the escape velocity at the distance of its original surface DOES NOT CHANGE

(an object there does not know that the Sun

has shrunk)

The ‘REAL’ Sun (radius = 700,000 km)

VESC, sfc=681,000 m/s

The ‘3-km Radius’ Sun VESC, sfc = 3x108 m/s VESC, old sfc=6.8x105 m/s

Earth would need to be shrunk to a radius of ~1 cm for its surface VESC value to equal the speed of light

SO, a BLACK HOLE ( an object so massive that not even light can escape its

gravitational attraction)

is only dangerous if you are close to it..

and the DENSITY of material within a Black

Hole is outrageously large (for 3-km Sun, density is ~ 2 x 1016 g/cm3)

How can BLACK HOLES be detected if no radiant energy is able to escape ?

When material falls toward a BLACK

HOLE will it fall at a slow speed or a fast speed?

A VERY FAST SPEED !!!!

As the pieces of fast moving material bump in to each other, they will heat each other up tremendously (think METEOR!)

This tremendously heated material will

emit away very-short wavelength (as well as other wavelengths) radiant energy

which can ‘escape’ before that material crosses the EVENT HORIZON

(= the distance from the BLACK HOLE’s center within which VESC is greater than the

speed of light)

Thus, BLACK HOLES can be ‘detected’ via the

tremendous quantity of very short wavelength GAMMA and X-RAY radiant energy the infalling material emits away before it crosses the EVENT HORIZON

….. BLACK HOLES can also be detected by the fast orbit speeds objects (such as stars) near to the black hole exhibit….

The center of our MILKY WAY Galaxy is home to a BLACK HOLE with a mass

equal to ~3.7 million Suns !!!! Looking toward the center of our Galaxy…. VISIBLE wavelengths

Infrared Wavelength

If we look at short (large energy) X-ray wavelengths, a tremendous intensity of energy

from the constellation Sagittarius (‘the Teapot’) is coming from the Galaxy’s center…

Individual stars in the vicinity of Sgr A are seen to complete orbits in ~15 years…. Using Newton’s modified version of Kepler’s 3rd Law, astronomers can determine that the mass of the central object around which the stars are orbiting is large enough to have an escape velocity that exceeds the speed of light… The ‘size’ of the black hole (the radius of its EVENT HORIZON) is ~6 ‘Light hours’, or ~45 AU in diameter

The lowest-mass BLACK HOLES have masses a few times the Sun’s mass, and arise from individual stars collapsing in

upon themselves when they have exhausted their ability to fuse low-mass

atoms to create higher-mass atoms…

The massive ‘Galactic Center’ BLACK HOLES seems to be associated with galaxy formation, but just what processes result in these massive BHs is not well understood…

Any BLACK HOLE questions?

SPACE ALIENS ???? not an exam topic LIFE ELSEWHERE IN OUR GALAXY?

What might be the ‘easiest’ ways to stay here on Earth but ‘SEARCH’ for life (and we’ll focus on technologically capable, intelligent life) elsewhere in our GALAXY?

‘EASY’ methods to Search for the presence of Life 1) try to detect radio-wavelength signals being broadcast by a civilization (… civilizations that are 60 Light Years away from us would just now start to receive the original ‘I LOVE LUCY’ television episodes broadcast in the early 1950’s…. while civilization that are 15 or 16 Light Years distant would just now start to receive broadcast episodes of “AMERICAN IDOL’)

The SETI (Search for Extraterrestrial Life) Program is engaged in such a ‘listen’ investigation

(SETI was at one time funded by NASA, but now is privately funded…… no obvious detections yet)

You can participate in the analysis of the radio signals that SETI receives:

http://setiathome.ssl.berkeley.edu/

SETI was featured in the movie (and book) CONTACT

which was partially filmed at the National Radio Astronomical Observatory (NRAO)’s

Very Large Array radio telescope west of Socorro, NM

How else to detect distant civilizations while we sit here on

Earth?

…. there are not too many other ways of detection that readily come to mind, at least with our current technologies….

HAVE OTHER DISTANT CIVILIZATIONS VISITED US HERE ON EARTH?

ALIENS……..

(Dr. Murphy’s belief is NO…)

The ‘ROSWELL’ incident from July 1947 is very well known (especially here in New Mexico)

If you traveled from Earth to another planet system 100 or 1000 Light Years away (we’ll assume that our technology has advanced enough to permit such travel in a short period of time): What would you do when you arrived at your destination? .. biologically investigate two men drinking beverages & fishing late on a FRiday night in Pascagoula, MS (1973)? .. crash your craft in the New Mexico desert (1947)? .. travel overhead of large–population cities (most years)? .. attack (.. many movies)? .. keep your presence quiet?

TERRAFORMING MARS…

NOT AN EXAM TOPIC !! Could we (humans) possibly make Mars a

HABITANLE PLANET? That is, could we create atmospheric conditions on Mars that would make Mars’ surface ‘WARMER’ with a greater ‘SURFACE GAS PRESSURE’ to permit liquid water to exist and maybe provide OXYGEN for humans to breathe?

http://www.youtube.com/watch?v=i5D8e71c75U

http://www.users.globalnet.co.uk/~mfogg/zubrin.htm

HOW COULD WE MAKE MARS’ SURFACE WARMER?

CAN WE USE MARS-AVAILABLE RESOURCES FOR THIS PURPOSE?

CAN WE THINK OF ANY PROBLEMS THAT WE WOULD CREATE THAT COULD NEGATIVELY

AFFECT OUR ATTEMPT TO ‘WARM UP’ MARS?

These ‘Mars Terraforming’ questions have been addressed, in a 1991 peer-reviewed journal paper

(NATURE journal)

Your are encouraged to watch a video available no-line that nicely illustrates

common misconceptions about WHAT CAUSES SEASONS

and WHAT CAUSES MOON PHASES

and hopefully learn that you now know how these processes ‘work’ (if you did not

already know prior to this semester..)

Video: http://www.learner.org/resources/series28.html Script: http://www.scribd.com/doc/269350/A-Private-Universe