Phys 1830: Lecture 23

1. Phys 1830: Lecture 23 The formation of a massive star. • Previous Class: • Solar System Tour • This Class • Exoplanets • Next Class • The Sun • Stars • Luminosity • Radii, Mass • Lifetime • Stellar Populations

2. Test • turn off cellphones and put them in your coat pocket • leave coat on seat. • Marks are posted on wall for tests.

3. Test #2 • Mean is 69.5% ~ C+ … expected. • Answers and marks posted outside my office Allen 514. • Please come and see me about your test in person by Nov 18, earlier if you think you might VW. VW Date – Nov 13th EXAM – Friday Dec 14@ 9:00am (Tentative - check at official UM site) • Solar System and Solar System Formation in detail onwards. • Please use PENCIL to fill out the bubble sheets as per instructions. • Please take care filling out your student number in the bubbles. • Please check that you have not put 2 answers on 1 line. • It is hard to give you a corrected grade if you have not filled out the question sheet – show your work.

4. Cheating ... on tests, quizzes, exams, or midterms • Cheating can be spontaneous or premeditated. • You are also cheating if you allow others to look at your exam. • The Faculty of Science values academic Integrity. Cheating will not be tolerated by the Faculty of Science. • Penalties may include a minimum of: • zero in the assignment, • F-DISC in the course, • a notation written on your transcript, and/or • suspension from courses in the department or the Faculty of Science for one year.

5. Common examples of academic dishonesty that occur every term: • A student brings a calculator to the final exam. The calculator is allowed by the instructor, but the calculator cover is forbidden. • An invigilator discovers the notes and the incident is forwarded to the department Head or the Associate Dean. An act of academic dishonesty has occurred regardless of whether the notes are used by you during the exam. • Also when handing in materials you write on your exam materials near other students answer sheets this provides an opportunity for academic dishonesty. • What are the consequences of the penalties? • They may slow down the progression of your degree, costing you time and money. • They may be visible to potential employers, professional school applications, or graduate schools. • They may affect your student visa eligibility for a year or more. • Protect yourself: • Do not bring unauthorized material into the exam (e. g. notes, cell phone, calculator cover). Do not bring calculators – they will be taken away for the test. • Resist opportunities to collaborate inappropriately or look at someone else’s paper. • If you suspect someone looking over your shoulder … Cover your paper; ask to be moved to another seat; alert the invigilator. • Review the online tutorials available through Student Advocacy: • umanitoba.ca/student/resource/student_advocacy/AI-and-Student-Conduct-Tutorials.html

6. Image 5: Both circles are intrinsically the same colour grey. If one stares at the image the cirlces appear to change. This composition is therefore an example of which contrast? a) complementary b) warm/cool c) simultaneous d) light/dark e) saturation

7. Test #2 Model Observations a) b) Clusters of Galaxies Nebula c) Image 6: The computer model on the left was meant to correspond to which of the following observations on the right side: a) b) c) d) a) and b) e) a) and c) Cosmic Web

8. Measure Linear Size Question 19

9. Review on Solar System and Solar System Formation : • Which planetary characteristic cannot be predicted by Solar System formation theories? • Composition (rocky or gaseous). • Size. • Rotation and revolution. • Temperature. • All of the above are explained by Condensation theory.

10. Which planets have polar vortices? • Venus, Earth, Jupiter, Saturn, Neptune, Uranus • Earth, Saturn, Jupiter • Venus, Jupiter, Saturn • Saturn • None of the above.

11. Which planets have rings? • Venus and Saturn • All the Jovians • Only Saturn • None of the above

12. Exoplanets and their planetary systems: David Lafreniere, Ray Jayawardhana, Marten H. van Kerkwijk (University of Toronto, Gemini Observatory) This image could be the first direct image of a planet (upper left) around another Sun-like star (center). • Extra-solar planets == exoplanets • How different are these planets from those in our Solar System? • Are our theories about our Solar System’s formation applicable to other planetary systems?

13. Proplyd disk around HD 21997 DUST RING (Hershel Space Obs. & ALMA) CO gas (ALMA) Gas rotating around host star (ALMA) • ~10 million years old • “hybrid disk”  both planetesimals (dust) and gas • dust more extended

14. Exoplanets: Characteristics MASSES # of planets Mass Uranus Super-Earths Mass Earth Mass Uranus • Roughly 1038 planets detected. • Interactive catalogue at http://exoplanet.eu/ • masses in Jupiter’s mass (Mjup: 318 x Mearth). • maximum mass ~ 50 x Mjup •  gas giants

15. Exoplanets: Characteristics DISTANCES # of planets • Roughly 1038 planets detected. • Interactive catalogue at http://exoplanet.eu/ Distance Earth Distance Neptune • distance from host star in AU • maximum distance a few thousand AU •  most are closer than Earth

16. Exoplanets: Characteristics • small mass planets rare? or • is our observational method biased?

17. Exoplanets: Radial Velocity Method  ~ 535 planets • Radial Velocity is the velocity along our line of sight. • The force of gravity between the star and the planet causes the star to be pulled towards the orbiting planet. • Causes the star to wobble back and forth  Star’s motion is Doppler Shifted. • The shift is going to be correlated with the gravitational force between the star and planet. movie

18. Exoplanets: Radial Velocity Method • If m (== mass of planet) increases, then F increases and the change in the radial velocity increases. • If r (== distance between star and planet) decreases, then F increases and the change in the radial velocity increases.  Easier to detect if the planet is massive and close to its star.

19. Review Most exoplanets detected to date are: • have masses similar to a Jupiter • have masses similar to Earth • orbit closer to their star than Jupiter does to ours d) a) and c) e) b) and c)

20. Exoplanets: Doppler Shift Method • The period of Jupiter at 5 AU is 12 years. • This is a long time for one person to observe one star! Your career could be over before you discover one at Saturn’s distance.  Easier to detect those planets closer to their star. • Now work in teams that can try to keep going for a long time.

21. Exoplanets Artist’s impression: The star Gliese 667 C, which belongs to a triple system – 2 of the stars seen in the background. The 6 Earth-mass exoplanet circulates around its low-mass host star at a distance equal to only 1/20th of the Earth-Sun distance. • Planet around alpha Centauri B! Sun-like star. • 4.3 ly distant, 3 stars. • Earth mass planet • P~3 days closer than Mercury • High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph, on ESO's 3.6-metre telescope, discovery of 150 exoplanets Sept 12/11. • HARPS has facilitated the discovery most of the planets known with masses below 20 Earth masses, i.e. super-Earths through the size of Neptune & Uranus. (About 40). • most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system. • CoRoT- 7b is 5 earth-masses and density comparable to Earth  rocky. But 23 times closer to its star than Mercury is to the Sun.

22. Exoplanets Artist: Lynette Cook • Gliese 581g (aka Zaramina’s World) • Gliese 581: Red, dwarf star. • Multiple planets in the system. • 3 * Earth’s mass; 1.5 Earth radius; similar gravity. • Right distance from its star for there to be liquid water == habitable zone. • Potentially life on the planet – not a certainty!

23. Exoplanets -- Kepler 78b • r = 1.2 x Earth & M = 1.7 x Earth  density ~ Earth => same density • orbit’s every 8.5 hrs => 2000K hotter • tidal forces will break it apart HARPS & HIRES spectrograph on Keck I