* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Pop Quiz Question
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Star of Bethlehem wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Observational astronomy wikipedia , lookup
Corona Borealis wikipedia , lookup
Dyson sphere wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Corona Australis wikipedia , lookup
Canis Major wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Malmquist bias wikipedia , lookup
Astronomical unit wikipedia , lookup
Star formation wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Type II supernova wikipedia , lookup
Cosmic distance ladder wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Stellar evolution wikipedia , lookup
ASTR 1020 * Spring 2017 MW 5:30-6:45 pm Stellar and Galactic Astronomy • Your instructor: Ryan Norris – Switched from Dr. Doug Gies • Email: [email protected] • Remember labs start week of Jan 23 (this week!) • Please get a syllabus from me if you don’t have one • For now slides will be on www.astro.gsu.edu/~norris/ASTR1020 – Up by tomorrow at 12PM Pop Quiz 1-Results • These count as bonus – 0-50% correct→0.25 pts – 50-80% correct → 0.5 pts – 80-100% correct → 0.75 pts – Added to your total score for the course (total is out of 100 pts) • The Quizes (first one next Monday) will have a similar format but more questions – You might even see the same question! • Class Average: 50% (6/12) Pop Quiz Question What we see visually as the surface of the Sun is the: A. corona B. core C. photosphere D. chromosphere Pop Quiz Question What we see visually as the surface of the Sun is the: A. corona B. core C. photosphere D. chromosphere Pop Quiz Question The temperature of the solar corona is approximately A. B. C. D. 1,000,000 K 100,000 K 15,000 K 6,000 K Pop Quiz Question The temperature of the solar corona is approximately A. B. C. D. 1,000,000 K 100,000 K 15,000 K 6,000 K Solar Atmosphere: Photosphere opaque limit, 4400 K (top), 6000 K (bottom), effective temperature ~5800K, visible light emission, ~500km thick Chromosphere hotter, 6000K (bottom)30000 K (top), avg= 10000-20000K, ultraviolet emission, ~2500 km thick Corona *really* hot, 106 K, X-ray emission Solar wind (extends through Solar System) All subject to “activity” Pop Quiz Question The temperature at the center of the Sun is approximately A. 6,000 K B. 15,000,000 K C. 15,000 K D. 100,000 K Pop Quiz Question The temperature at the center of the Sun is approximately A. 6,000 K B. 15,000,000 K C. 15,000 K D. 100,000 K Pop Quiz Question Sunspots appear dark because they are A. cooler than their surroundings B. hotter than their surroundings C. obscured from our point of view D. formed in the corona Pop Quiz Question Sunspots appear dark because they are A. cooler than their surroundings B. hotter than their surroundings C. obscured from our point of view D. formed in the corona Pop Quiz Question Sunspots,flares, prominences, and coronal mass ejections are all caused by A. neutrinos B. magnetic activity on the Sun C. the interaction of the Sun’s magnetic field and the solar wind D. electrical activity on the Sun Pop Quiz Question Sunspots,flares, prominences, and coronal mass ejections are all caused by A. neutrinos B. magnetic activity on the Sun C. the interaction of the Sun’s magnetic field and the solar wind D. electrical activity on the Sun Pop Quiz Question Nuclear fusion in the center of the Sun produces energy by the following reaction: A. four H to one He B. one H to four He C. one He to one H D. one H to one He Pop Quiz Question Nuclear fusion in the center of the Sun produces energy by the following reaction: A. four H to one He B. one H to four He C. one He to one H D. one H to one He Pop Quiz Question If energy production in the center of the Sun suddenly changed, which evidence would astronomers notice first? A. A change in visible-light emission B. A change in neutrino emission C. They would notice both at the same time Pop Quiz Question If energy production in the center of the Sun suddenly changed, which evidence would astronomers notice first? A. A change in visible-light emission B. A change in neutrino emission C. They would notice both at the same time Pop Quiz Question If the Sun’s core suddenly contracted (shrunk in radius) a little bit, what would happen in the Sun? A. The core would cool off and continue to shrink as its density increased B. The density of the core would decrease, causing the core to coll off and expand C. The core would heat up, causing it to radiate so much energy that it would shrink even more D. The core would heat up, fusion rates would increase, the core would re-expand. Pop Quiz Question If the Sun’s core suddenly contracted (shrunk in radius) a little bit, what would happen in the Sun? A. The core would cool off and continue to shrink as its density increased B. The density of the core would decrease, causing the core to coll off and expand C. The core would heat up, causing it to radiate so much energy that it would shrink even more D. The core would heat up, fusion rates would increase, the core would re-expand. Solar Thermostat Decline in core temperature causes fusion rate to drop, so core contracts and heats up Rise in core temperature causes fusion rate to rise, so core expands and cools down Pop Quiz Question Hydrostatic equilibrium in the Sun means the inward force of gravity is balanced by the outward force of A. pressure B. light C. electrons D. anti-gravity Pop Quiz Question Hydrostatic equilibrium in the Sun means the inward force of gravity is balanced by the outward force of A. pressure B. light C. electrons D. anti-gravity Pop Quiz Question X is the amount of light received on Earth whereas Y is the amount of light a star is giving off. A. Brightness:parallax B. Parallax:luminosity C. Brightness:luminosity D. Luminosity:brightness Pop Quiz Question X is the amount of light received on Earth whereas Y is the amount of light a star is giving off. A. Brightness:parallax B. Parallax:luminosity C. Brightness:luminosity D. Luminosity:brightness Pop Quiz Question The star Racecar has a parallax 100 mas while the star Kayak has a parallax of 50 mas. They are the same brightness. This means that: A. Kayak is twice as luminous as Racecar B. Racecar is twice as luminous as Kayak C. Racecar is four times as luminous as Kayak D. Kayak is four times as luminous as Racecar Pop Quiz Question The star Racecar has a parallax 100 mas while the star Kayak has a parallax of 50 mas. They are the same brightness. This means that: A. Kayak is twice as luminous as Racecar B. Racecar is twice as luminous as Kayak C. Racecar is four times as luminous as Kayak D. Kayak is four times as luminous as Racecar Pop Quiz Question Kayak: parallax 50 mas Racecar: parallax 100 mas Distance=1/parallax ● 1/50 vs 1/100 → Kayak is twice as far away ● Remember bigger parallax means closer! ● Smaller parallax means further! Brightness is the same but distance is twice as much ● So Kayak has to be more luminous Brightness is proportional to Luminosity/d^2 ● So if the distance is twice as much then in order for Brightness to be the same Luminosity must be d^2 more or 2^2 more...4 times as bright Pop Quiz Question Kayak: parallax 50 mas Racecar: parallax 100 mas Distance=1/parallax ● 1/50 vs 1/100 → Kayak is twice as far away ● Remember bigger parallax means closer! ● Smaller parallax means further! Pop Quiz Question Brightness is the same but distance is twice as much ● So Kayak has to be more luminous Brightness is proportional to Luminosity/d^2 LK BK 22 = BR LR 12 LK BK 4 = BR LR 1 LK 1= 4 LR 1 LR 1 = LK 22 4=LK/LR Pop Quiz Question A Blue star is hotter than a red star. A. TRUE B. FALSE C. There is not enough information to answer this question Pop Quiz Question A Blue star is hotter than a red star. A. TRUE B. FALSE C. There is not enough information to answer this question Luminosity HertzsprungRussell diagram plots the luminosity versus temperature of stars Temperature Luminosity In 1910 Ejnar Hertzsprung and Henry Norris Russell tediously built the first HR diagram for most known stars (at the time). Positions of stars in the HR diagram are related to their current state of evolution. Temperature Extending the Cosmic Distance Scale The problem with the classic parallax distance method is that it doesn’t reach far (< 200 pc). The spectroscopic parallax method doesn’t actually use any parallax motion, it is based on spectroscopy only. It works till ~10000 pc. We can estimate a star’s luminosity if we know its spectral type and luminosity class Extending the Cosmic Distance Scale How to get a distance with the “spectroscopic parallax” method: 1. Measure the star’s apparent magnitude m and spectral classification 2. Use spectral classification to estimate luminosity (absolute magnitude M) from HRD 3. Apply inverse-square law to find distance Magnitude equation version: m – M = 5 log d – 5 (will not be on the test) Extending the Cosmic Distance Scale Normal stellar parallax are limited to 500pc, but spectroscopic parallax can extend the cosmic distance scale to 10000 pc : Stellar Properties Review Luminosity: from brightness and distance 10-4 LSun - 106 LSun Temperature: from color and spectral type 3,000 K - 50,000 K Mass: from period (p) and average separation (a) of binary-star orbit 0.08 MSun - 100 MSun Lifetime Sun’s life expectancy: 10 billion years Life expectancy of 10 MSun star: Until core hydrogen (10% of total) is used up 10 times as much fuel, uses it 104 times as fast 10 billion years x 10 / 104 ~ 10 million years Life expectancy of 0.1 MSun star: 0.1 times as much fuel, uses it 0.01 times as fast 10 billion years x 0.1 / 0.01 ~ 100 billion years Main-Sequence Star Summary High Mass: High Luminosity Short-Lived Large Radius Blue Low Mass: Low Luminosity Long-Lived Small Radius Red Luminosity A D B C Temperature Which star is most like our Sun? Luminosity A D B C Temperature Which of these stars will have changed the least 10 billion years from now ? Luminosity A D B C Temperature Which of these stars can be no more than 10 million years old ? Star clusters = groups of same age stars Open cluster: A few thousand loosely packed stars (Pleiades), In the galactic disk, ~30 ly across, relatively young (< 5 billion years) Globular cluster: hundreds of thousands stars in a dense ball (M80), ~60-150 ly across, >10 billion years, in halo of the Milky Way Massive blue stars die first, followed by lower mass stars (white, yellow, orange, and red) In HRD, stars die away first at the top end (massive stars) of main sequence. We can find the age of a cluster by determining the turn-off point, which corresponds to the most massive stars still on main sequence. HR diagrams for two open clusters, showing the main sequence turn-off at different ages. Oldest globular clusters are ~13 billion years old Pop Quiz Question The spectral sequence ____ corresponds to a temperature sequence of hot to cool stars A. OBAFGKM B. OBFGAMK C. OMAFGKB D. MKGFABO Pop Quiz Question The spectral sequence ____ corresponds to a temperature sequence of hot to cool stars A. OBAFGKM B. OBFGAMK C. OMAFGKB D. MKGFABO Pop Quiz Question The star Canopus has spectral classification A9II so its luminosity class indicates it is a ___ star A. main sequence B. bright giant C. subgiant D. supergiant Pop Quiz Question The star Canopus has spectral classification A9II so its luminosity class indicates it is a ___ star A. main sequence B. bright giant C. subgiant D. supergiant Pop Quiz Question The Sun has a diameter over 100 times the Earth’s A. TRUE B. False Pop Quiz Question The Sun has a diameter over 100 times the Earth’s A. TRUE B. False Pop Quiz Question The apparent magntiude of the Sun is A. Close to 5 as it is average in luminosity B. Close to -27 as it is the brightest object in the sky C. Close to -5 as it is average in luminosity D. Close to 27 as it is the brightest object in the sky Pop Quiz Question The apparent magntiude of the Sun is A. Close to 5 as it is average in luminosity B. Close to -27 as it is the brightest object in the sky C. Close to -5 as it is average in luminosity D. Close to 27 as it is the brightest object in the sky Pop Quiz Question Which is the largest star: A. a M7 I star B. a F4IV star C. a AIV star D. a O2 II star Pop Quiz Question Which is the largest star: A. a M7 I star B. a F4IV star C. a AIV star D. a O2 II star Pop Quiz Question Globular Clusters are young and have recent star formation A. TRUE B. FALSE Pop Quiz Question Globular Clusters are young and have recent star formation A. TRUE B. FALSE