1 8. The evolution of stars a more detailed picture 8.1Pre Main-Sequence Evolution Evolution onto the main sequence begins with a cloud of cold gas which contracts under self-gravity. Potential Energy is transformed into kinetic energy, which gets thermalised, so the temperature goes up. This phase lasts a relatively short time. When the cloud is hot enough, the gas is ionised and OPACITY sets in. When that is the case, the gas finds it harder to lose energy, and becomes hotter even quicker. Since the opacity is so high the star is fully convective. The star in the HR diagram moves at tracks of almost constant temperature and with decreasing luminosity (Fig. 1). These are called Hayashi-tracks. In time, as the internal temperature continues to rise, ionisation is completed and the opacity drops. The convective zone recedes from the centre, and the star moves to higher effective temperatures. Slowly nuclear burning starts in the core. As a result the stellar luminosity starts rising slowly. In the end, when nuclear burning has fully set in, a star is born, and the star appears on the Main Sequence. The timescale of evolution onto the Main Sequence is relatively short, given by the Kelvin-Helmholtz timescale : t KH U L G M 2 R L Stars in the pre-main sequence are hard to detecet because they are scarce, but also because they are still shrouded by the remains of the cloud in which they are formed. The less massive pre-main sequence stars appear as highly variable mass ejecting objects known as T Tauri stars. They are surrounded by circumstellar disks, sites of planet formation.
2 Before a star starts burning hydrogen it is often called a protostar. Several candidate protostars have been found by the Hubble Space Telescope in the Orion Nebula. During the initial collapse, the clump is transparent to radiation and the collapse proceeds fairly quickly. As the clump becomes more dense, it becomes opaque. Escaping IR radiation is trapped, and the temperature and pressure in the center begin to increase. At some point, the pressure stops the infall of more gas into the core and the object becomes stable as a protostar.
3 The protostar, at first, only has about 1% of its final mass. But the envelope of the star continues to grow as infalling material is accreted. After a few million years, thermonuclear fusion begins in its core, then a strong stellar wind is produced which stops the infall of new mass. The protostar is now considered a young star since its mass is fixed, and its future evolution is now set. T-Tauri Stars: Once a protostar has become a hydrogen-burning star, a strong stellar wind forms, usually along the axis of rotation. Thus, many young stars have a bipolar outflow, a flow of gas out the poles of the star. This is a feature which is easily seen by radio telescopes. This early phase in the life of a star is called the T-Tauri phase. One consequence of this collapse is that young T Tauri stars are usually surrounded by massive, opaque, circumstellar disks. These disks gradually accrete onto the stellar surface, and thereby radiate energy both from the disk (infrared wavelengths), and from the position where material falls onto the star at (optical and ultraviolet wavelengths). Somehow a fraction of the material accreted onto the star is ejected perpendicular to the disk plane in a highly collimated stellar jet. The circumstellar disk eventually dissipates, probably when planets begin to form. Young stars also have dark spots on
4 their surfaces which are analogous to sunspots but cover a much larger fraction of the surface area of the star. The T-Tauri phase is when a star has: vigorous surface activity (flares, eruptions) strong stellar winds variable and irregular light curves A star in the T-Tauri phase can lose up to 50% of its mass before settling down as a main sequence star, thus we call them pre-main sequence stars. Their location on the HR diagram is shown below: The arrows indicate how the T-Tauri stars will evolve onto the main sequence. They begin their lives as slightly cool stars, then heat up and become bluer and slightly fainter, depending on their initial mass. Very massive young stars are born so rapidly that they just appear on the main sequence with such a short T-Tauri phase that they are never observed. T-Tauri stars are always found embedded in the clouds of gas from which they were
5 born. One example is the Trapezium cluster of stars in the Orion Nebula. The evolution of young stars is from a cluster of protostars deep in a molecular clouds core, to a cluster of T-Tauri stars whose hot surface and stellar winds heat the surrounding gas to form an HII region (HII, pronounced H-two, means ionized hydrogen). Later the cluster breaks out, the gas is blown away, and the stars evolve as shown below.
6 Often in galaxies we find clusters of young stars near other young stars. This phenomenon is called supernova induced star formation. The very massive stars form first and explode into supernova. This makes shock waves into the molecular cloud, causing nearby gas to compress and form more stars. This allows a type of stellar coherence (young stars are found near other young stars) to build up, and is responsible for the pinwheel patterns we see in galaxies. Contraction takes about 1% of a star's life. It will spend about 80% as a main sequence stars. For example, for the Sun, the contraction phase takes about M Sun. For a 9 solar mass star this phase takes only 10 5 years. 8.2 Low-mass stars (from Vik Dhillon - Sheffield) Stars of mass less than 1.1 M Sun fuse hydrogen using the P-P chain. As this has a comparatively weak temperature dependence, energy generation is not sufficiently concentrated at the centre of the star to induce convection, and the core of the star is radiative. This means that the core of the star is not mixed and nuclear reactions can therefore draw only on the fuel that is available locally. The temperature is highest at the centre and so the rate of burning is highest there, forming a concentration gradient with smallest hydrogen content in the centre of the star. The interior of three stellar types are shown below. Note that an O star is about 15 times larger than a G star, and a M star is about 1/10 the size of a G star, this scale is shown below the interiors.
7 This scale, on the other hand, displays the absolute sizes. Notice how the nuclear burning regions takes up a larger percentage of the stellar interior as one goes to low mass stars. High mass stars have a very small core surrounded by a large envelope. The energy released from the stellar core heats the stellar interior producing the pressure that holds a star
8 up. If stars were like cars, then they would burn their core hydrogen until they ran out and the star would fade out. But fusion converts hydrogen into helium. So the core does not become empty, it fills with helium `ash'. Eventually, the centre of the star becomes completely devoid of hydrogen. Immediately outside the centre, however, the temperature is only a little lower and there is still hydrogen left to burn. Nuclear reactions therefore continue, but now in a thick shell rather than throughout a sphere, as shown in Figure 1. Fig. 1:The structure of a low-mass star ( M 1.1 M Sun red-giant branches of the HR diagram. ) on the sub-giant and The continuation of nuclear burning in a shell means that there is no need for the whole star to contract. Only in the central regions, where there is no longer any energy production but energy is still leaking outwards in to the rest of the star, is there a need for an additional energy source. The core thus begins to contract, releasing gravitational potential energy and therefore getting hotter. Because the core gets hotter, the temperature of the hydrogen-
9 fusing shell outside the core also increases, increasing the rate of fusion. This heats up the intermediate layers of the star, causing them to expand. The expansion increases the total radius of the star. Recalling that: 4 L 4 R S T eff and given that the luminosity a radiative envelope can carry is nearly constant for a star of given mass, there must be a decrease in the effective temperature of the star, causing the star to appear red. The immediate postmain-sequence evolution of a radiative star therefore moves the star's position more-or-less horizontally to the right in to the sub-giant branch of the HRdiagram, as shown in Fig. 2. Fig. 2: The complete evolution of a low-mass star ( M 1.1 M Sun ) from the main sequence to a white dwarf, depicted schematically on an HR diagram.
10 As the star expands, however, the effective temperature cannot continue to fall indefinitely. When the temperature of the outer layers of the star fall below a certain level, they become fully convective. This enables a greater luminosity to be carried by the outer layers and hence abruptly forces the evolutionary tracks of low-mass stars in the HR diagram to travel almost vertically upwards to the giant branch (see Fig. 2). The effective temperature at which this upward excursion in luminosity on the HR diagram occurs is known as the Hayashi line. Meanwhile, the helium core continues to contract until it becomes degenerate. The increased gravity at the border of the core and the shell which results from the core contraction raises the density of the hydrogen in the shell. This increases the rate of hydrogen burning in the shell, sending the star quickly up the red giant branch. The hotter hydrogen-burning shell heats up the degenerate core until it reaches the point where helium fusion to carbon through the triple-alpha process is possible. The onset of this fusion process and the consequent heating of the core would normally increase the core pressure, causing it to expand and cool in response, keeping the temperature just high enough for the nuclear reactions to continue; helium burning would therefore start in a stable fashion. Because the core is degenerate, however, its pressure is independent of the temperature and hence it cannot expand and cool in response to the nuclear energy generation. Hence the core heats up, which increases the rate of helium fusion, which in turn increases the core
11 temperature still further, leading to a thermonuclear runaway reaction know as the helium flash (see Fig. 2). The helium flash ends when the temperature has risen sufficiently to make higher-energy electron states available for electrons to move into, lifting the core degeneracy and allowing the core to expand. The expansion of the core following the helium flash reduces the gravity at the core/shell boundary, which weakens the hydrogen shell-source. Thus, although the star now has two nuclear energy source - the helium burning core and the hydrogen-burning shell - the prodigious shell source is now so weakened that the star produces less luminosity than before. The lower total luminosity is too little to keep the star in its distended red-giant state and the star shrinks in size, dims and settles on the horizontal branch (see figure 2). Fig. 3: The structure of a low-mass star ( M 1.1 M Sun branch of the HR diagram. ) on the asymptotic giant The history of the helium burning stage is much like the earlier hydrogen burning stage. When the core helium is exhausted, a helium burning shell is established between the inert carbon-oxygen core and the hydrogen-burning shell (see Fig. 3) and the star evolves up the asymptotic giant branch, as shown in Fig. 2. This stage of stellar evolution is not well understood, involving complex interactions between the helium and hydrogen burning shells. The star becomes increasingly unstable and begins to lose mass in an intense stellar wind, which eventually consumes the whole outer envelope. This lost mass forms an expanding cloud around the star known as a planetary nebula, an example of which is shown in Fig. 4.
12 Fig. 4: The Helix nebula ( Anglo-Australian Observatory). The extremely hot, degenerate, carbon-oxygen core of the original star, no longer generating energy, remains as the central star of the planetary nebula and cools slowly as it radiates away its stored heat. When the core has finally burnt its hydrogen and helium shells, lost its extended envelope and descended the HR diagram, it is known as a white dwarf. The final approach to a white dwarf from an asymptotic giant star is shown as a dashed line in Fig. 2 because the theory is incomplete for these late stages of stellar evolution. Fig. 5 summarises the complete evolution of a low-mass star ( M 1.1 M Sun ) from the main sequence to a carbon-oxygen white dwarf in pictorial form.
13 Fig. 5: The complete evolution of a low-mass star ( M 1.1 M Sun ) from the main sequence to a carbon-oxygen white dwarf in pictorial form. 8.3 High-mass stars (from Vik Dhillon - Sheffield) In stars with masses greater than about 1.1 M Sun, the central temperature is high enough for the CNO cycle to become dominant. The strong temperature dependence of the CNO cycle means that the energy generation is much more concentrated at the centre of the star. The resulting steep temperature gradient is unstable to convection and hence such stars have convective cores. Convection has the effect of mixing the material in the core, bringing fresh hydrogen into the centre and spreading the newly-produced helium throughout the core. This keeps the chemical composition of the core uniform, which means that when the nuclear reactions have used up all of the hydrogen at the centre, there is no hydrogen left anywhere in the convectively mixed region and energy production ceases throughout the core. Just outside the core, hydrogen is still available for burning, but the temperature is too low for fusion to occur and hydrogen burning ceases altogether when the core burns out.
14 The abrupt cessation of hydrogen burning means that the star now has no nuclear energy source and it is forced into a slow overall contraction. Part of the gravitational potential energy released is used to balance the radiation from its surface, but about half of it goes into heating up the core as the central density and pressure are increased by the contraction. Eventually, the core is hot enough that hydrogen can start burning in a thin shell just outside the core boundary. The star is now similar in structure to a hydrogen-shellburning star of lower mass, as shown in Fig. 1, but it has a much thinner shell (because the dependence of energy production on temperature is more severe). Overall contraction stops, and the energy from the contraction of the core is now fed into an expansion of the envelope, just as for lower-mass stars. The main difference in the evolutionary track of higher-mass stars in the HR-diagram is that the phase of overall contraction causes a hook to the left before progress to the giant region is resumed once the shell has ignited, as shown in Fig. 2.
15 Fig. 2: The evolution of high-mass stars depicted schematically on an HR diagram. The track for a solar mass star is also shown for comparison. The three dots on each track represent, from left to right, the main-sequence, the onset of core contraction following hydrogen exhaustion, and the beginning of helium burning, respectively. The exhausted core now consists of almost pure helium. Although there is no nuclear energy source, the centre of the star is initially hotter than the edge of the core and heat flows down this temperature gradient, cooling the centre and heating up the outside. This continues until the core becomes isothermal. The isothermal core grows slowly in mass as the shell gradually burns its way outwards into fresh fuel, leaving helium 'ash' behind. This continues until the core reaches the Schönberg-Chandrasekhar limit of about 10% of the mass of the star, at which point an isothermal core cannot support itself against gravity. This instability only occurs in stars with masses between about 2 M Sun and 6 M Sun. For lower mass stars, the core becomes degenerate before the Schönberg-Chandrasekhar limit is reached; for higher mass stars, the central temperature becomes hot enough for helium fusion to occur before the Schönberg-Chandrasekhar limit is reached. In stars in which the Schönberg-Chandrasekhar limit is reached, the core begins to contract rapidly. The energy released goes into a rapid expansion of the whole star, and hence a rapid transition to the giant branch. Because of
16 this rapid transition, very few stars are observed during this phase, which accounts for the Hertsprung gap seen in HR diagrams of clusters. As lowermass stars become red giants less rapidly, this agrees with the absence of a Hertzsprung gap in the HR diagrams of globular clusters. The collapse of the helium core, whether rapid or not, raises the central temperature to the point where helium ignites via the triple-alpha process. If the core is not degenerate (i.e. M > 2 M Sun ), helium ignites gently and there is no helium flash. The effect of helium ignition, whether violent or quiet, is to move a star off the giant branch towards higher surface temperatures (i.e. to the left of the HR diagram). There are now two nuclear energy sources, helium-burning in the core and hydrogen-burning in a shell, and the evolution is much more complicated than in the core-hydrogen-burning phase. After existing as horizontal branch stars for a few million years, the helium in the core of the star is exhausted (now being mostly carbon and oxygen nuclei) and a helium burning shell will develop underneath the hydrogen burning shell. The electrons and nuclei in the core again become degenerate and the star expands and cools to become an asymptotic giant branch star.
17 Most of the energy is coming from the hydrogen burning shell, the helium burning shell is small at this time. However, the hydrogen shell is dumping helium ash onto the helium shell. After sometime, enough helium is built up so that the helium shell undergoes an explosive event called a thermal pulse. The thermal pulse is barely noticed at the surface of the star, but serves to increase the mass of the carbon/oxygen core, so that the size and luminosity of the star gradually increases with time. As the star climbs the asymptotic giant branch, a wind develops in the star's envelope which blows the outer layers into space. It is in this wind that dust particles (important for interstellar clouds and proto-solar systems) are formed from carbon material dredged up from the core by convective currents. During this time, a thick dust shell blocks the visible light from the star such that even though it is 10,000 brighter than the Sun, it is only seen in the IR. Nuclear evolution beyond core helium-burning depends on whether or not the carbon-oxygen core ever becomes hot enough for further fusion reactions to occur and whether the core becomes degenerate. For stars with initial
18 masses of M > 8 M Sun, the core is non-degenerate and carbon can ignite quietly, burning first to oxygen and neon. At lower initial masses, a carbon flash occurs, as the core is degenerate. Further reactions are possible and a series of burning episodes builds up successive shells of more and more processed material. Elements produced in these shells include magnesium, silicon and sulphur. For stellar masses greater than about 11 M Sun, burning can proceed as far as iron and other elements of comparable nuclear mass, principally chromium, manganese, cobalt and nickel (the so-called iron-peak elements). At this point, because iron is the most stable element, with the highest binding energy per nucleon, to produce elements heavier than iron it is necessary to add energy. The star has thus exhausted all its possible nuclear fuels and it has an onion skin structure, with successive shells containing the ashes of the various burning stages, as shown in Fig. 3. Fig. 3: The onion-ring structure of a red supergiant (a pre-supernova star). Note that this diagram is not too scale - the outer hydrogen burning shell has a radius of order 10-2 R Sun and whereas the star has a radius of order 10 3 R Sun. The evolution of a massive star undergoing these different phases of core and shell burning beyond helium is very complex. As the core and shell energy sources vary in relative strength, the star makes a number of excursions to and fro across the HR diagram. In high-mass stars, these rightward (core exhaustion) and leftward (core ignition) excursions, between the red and blue (supergiant) branches respectively, occur with only a slight systematic
19 increase in luminosity and hence the evolutionary tracks of high-mass stars occur virtually horizontally in the HR diagram. In very high-mass stars, the nuclear evolution in the central regions of the star occurs so quickly that the outer layers have no time to respond to the successive rounds of core exhaustion and core ignition, and there is only a relatively steady drift to the right on the HR diagram before the star arrives at the pre-supernova state, as shown in Fig. 2. It should be noted that the details of this stage of stellar evolution remain uncertain. In addition, the time taken to make these latter excursions in the HR diagram are very small compared to the duration of the earlier phases. So we do not expect to observe all the complications of an individual evolutionary track to show up in a star cluster HR diagram. With no nuclear energy generation, the iron core becomes degenerate. As lighter elements continue to burn in shells above it, the iron core grows in mass until it exceeds the Chandrasekhar limit of around 1.4 M Sun - the maximum possible mass of a white dwarf, above which electron degeneracy pressure is insufficient to prevent gravitational collapse. The core then begins to collapse. The core's iron nuclei decompose into those of helium, which then fragment into protons and neutrons, and the protons then combine with the electrons to form more neutrons, all at the expense of the star's gravitational potential energy. In this way, the collapsed core becomes a neutron star, where it is the degeneracy pressure exerted by neutrons which prevents continued gravitational collapse. Meanwhile, the outer layers of the star are still collapsing: they hit the hard surface of the newly formed neutron star and bounce off, creating a shockwave which blows off the outer layers of the star in a Type II supernova explosion occurs, as depicted in the animation of Fig. 4. Fig.4: An animation showing the final stages of a Type II supernova explosion. What remains after a Type II supernova explosion? The expelled envelope of the star becomes visible as a supernova remnant, as shown in Fig. 5, at the centre of which lies the core of the star. If the core of the star has a mass of below approximately 3 M Sun, it is a neutron star, those that exhibit pulsed radiation being known as pulsars.
20 Fig. 5: The crab nebula - the remnant of a supernova which exploded about 900 years ago. But if the mass of the core exceeds approximately 3 M Sun, there is nothing to prevent the core from collapsing to a state of zero radius and infinite density (within the laws of physics as they are presently understood). Such an object is known as a black hole. Isolated black holes cannot be directly observed, as the escape velocity from its surface exceeds the speed of light. Evidence that they exist has only recently been confirmed via observations of binary stars, where the motion of the visible star is measured in order to determine the mass of the compact object lying at the heart of the accretion disc in Fig. 6. If the mass of the compact object is measured to be M > 3 M Sun, the existence of a black hole is inferred.
21 Fig. 6: An artists impression of an X-ray binary star, some of which are believed to harbour black holes.
Nuclear fusion in stars Collapse of primordial density fluctuations into galaxies and stars, nucleosynthesis in stars The origin of structure in the Universe Until the time of formation of protogalaxies,
1. Most interstellar matter is too cold to be observed optically. Its radiation can be detected in which part of the electromagnetic spectrum? A. gamma ray B. ultraviolet C. infrared D. X ray 2. The space
Chapter 19 Star Formation 19.1 Star-Forming Regions Units of Chapter 19 Competition in Star Formation 19.2 The Formation of Stars Like the Sun 19.3 Stars of Other Masses 19.4 Observations of Cloud Fragments
WHERE DID ALL THE ELEMENTS COME FROM?? In the very beginning, both space and time were created in the Big Bang. It happened 13.7 billion years ago. Afterwards, the universe was a very hot, expanding soup
Stellar Evolution: a Journey through the H-R Diagram Mike Montgomery 21 Apr, 2001 0-0 The Herztsprung-Russell Diagram (HRD) was independently invented by Herztsprung (1911) and Russell (1913) They plotted
Ay 20 - Lecture 9 Post-Main Sequence Stellar Evolution This file has many figures missing, in order to keep it a reasonable size. Main Sequence and the Range of Stellar Masses MS is defined as the locus
Name Date Period 30 GALAXIES AND THE UNIVERSE SECTION 30.1 The Milky Way Galaxy In your textbook, read about discovering the Milky Way. (20 points) For each item in Column A, write the letter of the matching
OVERVIEW More than ever before, Physics in the Twenty First Century has become an example of international cooperation, particularly in the areas of astronomy and cosmology. Astronomers work in a number
Exercises 131 The Falling Apple (page 233) 1 Describe the legend of Newton s discovery that gravity extends throughout the universe According to legend, Newton saw an apple fall from a tree and realized
Chapter 15.3 Galaxy Evolution Elliptical Galaxies Spiral Galaxies Irregular Galaxies Are there any connections between the three types of galaxies? How do galaxies form? How do galaxies evolve? P.S. You
UNIT V Earth and Space Chapter 9 Earth and the Solar System EARTH AND OTHER PLANETS A solar system contains planets, moons, and other objects that orbit around a star or the star system. The solar system
CHAPTER 3 1 A Solar System Is Born SECTION Formation of the Solar System BEFORE YOU READ After you read this section, you should be able to answer these questions: What is a nebula? How did our solar system
Evolution of Close Binary Systems Before going on to the evolution of massive stars and supernovae II, we ll think about the evolution of close binary systems. There are many multiple star systems in the
Chapter 12 Quiz, Nov. 28, 2012, Astro 162, Section 4 12-1. Where in our Galaxy has a supermassive (or galactic) black hole been observed? a) at the outer edge of the nuclear bulge b) in the nucleus X c)
ctivity: Multiwavelength background: lmost everything that we know about distant objects in the Universe comes from studying the light that is emitted or reflected by them. The entire range of energies
Origin of the Solar System Lecture 7 Formation of the Solar System Reading: Chapter 9 Quiz#2 Today: Lecture 60 minutes, then quiz 20 minutes. Homework#1 will be returned on Thursday. Our theory must explain
Science Standard 4 Earth in Space Grade Level Expectations Science Standard 4 Earth in Space Our Solar System is a collection of gravitationally interacting bodies that include Earth and the Moon. Universal
Be Stars By Carla Morton Index 1. Stars 2. Spectral types 3. B Stars 4. Be stars 5. Bibliography How stars are formed Stars are composed of gas Hydrogen is the main component of stars. Stars are formed
Lecture 14 Introduction to the Sun ALMA discovers planets forming in a protoplanetary disc. Open Q: what physics do we learn about the Sun? 1. Energy - nuclear energy - magnetic energy 2. Radiation - continuum
Using Photometric Data to Derive an HR Diagram for a Star Cluster In In this Activity, we will investigate: 1. How to use photometric data for an open cluster to derive an H-R Diagram for the stars and
In studying the Milky Way, we have a classic problem of not being able to see the forest for the trees. A panoramic painting of the Milky Way as seen from Earth, done by Knut Lundmark in the 1940 s. The
THE HR DIAGRAM THE MOST FAMOUS DIAGRAM in ASTRONOMY Mike Luciuk 1.INTRODUCTION Late in the nineteenth century, astronomers had tools that revealed a great deal about stars. By that time, advances in telescope
The Origin of the Solar System and Other Planetary Systems Modeling Planet Formation Boundary Conditions Nebular Hypothesis Fixing Problems Role of Catastrophes Planets of Other Stars Modeling Planet Formation
Enter your answers on the form provided. Be sure to write your name and student ID number on the first blank at the bottom of the form. Please mark the version (B) in the Key ID space at the top of the
California Standards Grades 912 Boardworks 2009 Science Contents Standards Mapping Earth Sciences Earth s Place in the Universe 1. Astronomy and planetary exploration reveal the solar system s structure,
Stellar Astrophysics: Stellar Evolution 1 Stellar Evolution Update date: October 29, 2014 With the understanding of the basic physical processes in stars, we now proceed to study their evolution. In particular,
Nuclear fission and fusion P2 62 minutes 62 marks Page of 23 Q. Nuclear power stations use the energy released from nuclear fuels to generate electricity. (a) Which substance do the majority of nuclear
Astro 130, Fall 2011, Homework, Chapter 17, Due Sep 29, 2011 Name: Date: 1. If stellar parallax can be measured to a precision of about 0.01 arcsec using telescopes on Earth to observe stars, to what distance
Science Olympiad Astronomy Multiple Choice: Choose the best answer for each question. Each question is worth one point. In the event of a tie, there will be a tie-breaking word problem. 1) The final phase
Determining the Sizes & Distances of Stars Using the H-R Diagram Activity UCIObs 11 College Level Source: Copyright (2009) by Tammy Smecker-Hane & Michael Hood. Contact firstname.lastname@example.org with questions.
Study Guide: Solar System 1. How many planets are there in the solar system? 2. What is the correct order of all the planets in the solar system? 3. Where can a comet be located in the solar system? 4.
The Messier Objects As A Tool in Teaching Astronomy Dr. Jesus Rodrigo F. Torres President, Rizal Technological University Individual Member, International Astronomical Union Chairman, Department of Astronomy,
The Birth of the Universe Newcomer Academy High School Visualization One Chapter Topic Key Points of Discussion Notes & Vocabulary 1 Birth of The Big Bang Theory Activity 4A the How and when did the universe
Summary: Four Major Features of our Solar System How did the solar system form? According to the nebular theory, our solar system formed from the gravitational collapse of a giant cloud of interstellar
Galaxy Evolution is the study of how galaxies form and how they change over time. As was the case with we can not observe an individual galaxy evolve but we can observe different galaxies at various stages
Lecture 8: Cloud Stability Heating & Cooling in Molecular Clouds Balance of heating and cooling processes helps to set the temperature in the gas. This then sets the minimum internal pressure in a core
The Layout of the Solar System Planets fall into two main categories Terrestrial (i.e. Earth-like) Jovian (i.e. Jupiter-like or gaseous) [~5000 kg/m 3 ] [~1300 kg/m 3 ] What is density? Average density
Origins of the Cosmos Summer 2016 Pre-course assessment In order to grant two graduate credits for the workshop, we do require you to spend some hours before arriving at Penn State. We encourage all of
I The Sun and Solar Energy One of the most important forces behind global change on Earth is over 90 million miles distant from the planet. The Sun is the ultimate, original source of the energy that drives
credit: NASA L2: The building-up of the chemical elements UCL Certificate of astronomy Dr. Ingo Waldmann What ordinary stuff is made of What ordinary stuff is made of Build up of metallicity 2 What are
DE2410: Learning Objectives SOLAR SYSTEM Formation, Evolution and Death To become aware of our planet, solar system, and the Universe To know about how these objects and structures were formed, are evolving
The Formation of Planetary Systems Astronomy 1-1 Lecture 20-1 Modeling Planet Formation Any model for solar system and planet formation must explain 1. Planets are relatively isolated in space 2. Planetary
Solar System Fundamentals What is a Planet? Planetary orbits Planetary temperatures Planetary Atmospheres Origin of the Solar System Properties of Planets What is a planet? Defined finally in August 2006!
Article 1 Big Bang - the birth of our universe. The universe we can observe is finite. It has a beginning in space and time, before which the concept of space and time has no meaning, because spacetime
Lecture #34: Solar System Origin II How did the solar system form? Chemical Condensation ("Lewis") Model. Formation of the Terrestrial Planets. Formation of the Giant Planets. Planetary Evolution. Reading:
Q. (a) The diagrams represent three atoms, X, Y and Z. Which of these atoms are isotopes of the same element? Give a reason for your answer. In a star, nuclei of atom X join to form nuclei of atom Y. Complete
Lesson Plan G2 The Stars Introduction We see the stars as tiny points of light in the sky. They may all look the same but they are not. They range in size, color, temperature, power, and life spans. In
Test 2 f14 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Carbon cycles through the Earth system. During photosynthesis, carbon is a. released from wood
Introduction to the Solar System Lesson Objectives Describe some early ideas about our solar system. Name the planets, and describe their motion around the Sun. Explain how the solar system formed. Introduction
Lecture Outlines Chapter 15 Astronomy Today 7th Edition Chaisson/McMillan Chapter 15 The Formation of Planetary Systems Units of Chapter 15 15.1 Modeling Planet Formation 15.2 Terrestrial and Jovian Planets
The Universe Inside of You: Where do the atoms in your body come from? Matthew Mumpower University of Notre Dame Thursday June 27th 2013 Nucleosynthesis nu cle o syn the sis The formation of new atomic
Instructions: Answers are typed in blue. Answers for the Student Worksheet for the Hubble Space Telescope Scavenger Hunt Crab Nebula What is embedded in the center of the nebula? Neutron star Who first
Stars, Galaxies, Guided Reading and Study This section explains how astronomers think the universe and the solar system formed. Use Target Reading Skills As you read about the evidence that supports the
Federation of Galaxy Explorers Space Science Once Upon A Big Bang Learning Objectives: 1. Explain how the universe was created using the Big Bang theory. 2. Understand how the existence of Cosmic Background
IV. Molecular Clouds Dark structures in the ISM emit molecular lines. Dense gas cools, Metals combine to form molecules, Molecular clouds form. 1. Molecular Cloud Spectra 1 Molecular Lines emerge in absorption:
Imperial College London BSc/MSci EXAMINATION June 2008 This paper is also taken for the relevant Examination for the Associateship SUN, STARS, PLANETS For Second Year Physics Students Wednesday, 4th June
Astro 102 Test 5 Review Spring 2016 See Old Test 4 #16-23, Test 5 #1-3, Old Final #1-14 Sec 14.5 Expanding Universe Know: Doppler shift, redshift, Hubble s Law, cosmic distance ladder, standard candles,
Old Science 30 Physics Practice Test A on Fields and EMR Test Solutions on the Portal Site Use the following image to answer the next question 1. Which of the following rows identifies the electrical charge
Lecture 15 Fundamentals of Physics Phys 120, Fall 2015 Cosmology A. J. Wagner North Dakota State University, Fargo, ND 58108 Fargo, October 20, 2015 Overview A history of our view of the universe The Big
The Universe is thought to consist of trillions of galaxies. Our galaxy, the Milky Way, has billions of stars. One of those stars is our Sun. Our solar system consists of the Sun at the center, and all
Solar System Formation Solar System Formation Question: How did our solar system and other planetary systems form? Comparative planetology has helped us understand Compare the differences and similarities
The Birth, Life, and Death of Stars The Osher Lifelong Learning Institute Florida State University Jorge Piekarewicz Department of Physics email@example.com Schedule: September 29 November 3 Time: 11:30am
Your years of toil Said Ryle to Hoyle Are wasted years, believe me. The Steady State Is out of date Unless my eyes deceive me. My telescope Has dashed your hope; Your tenets are refuted. Let me be terse:
Giant Molecular Clouds http://www.astro.ncu.edu.tw/irlab/projects/project.htm Galactic Open Clusters Galactic Structure GMCs The Solar System and its Place in the Galaxy In Encyclopedia of the Solar System
1 Lecture 10 Formation of the Solar System January 6c, 2014 2 Orbits of the Planets 3 Clues for the Formation of the SS All planets orbit in roughly the same plane about the Sun. All planets orbit in the
Chapter 7 Neutron Stars 7.1 White dwarfs We consider an old star, below the mass necessary for a supernova, that exhausts its fuel and begins to cool and contract. At a sufficiently low temperature the
Elliptical galaxies: Ellipticals Old view (ellipticals are boring, simple systems)! Ellipticals contain no gas & dust! Ellipticals are composed of old stars! Ellipticals formed in a monolithic collapse,
5. The Nature of Light Light travels in vacuum at 3.0. 10 8 m/s Light is one form of electromagnetic radiation Continuous radiation: Based on temperature Wien s Law & the Stefan-Boltzmann Law Light has
Section 24-1 1. Carol is in a railroad car on a train moving west along a straight stretch of track at a constant speed of 120 km/h, and Charles is in a railroad car on a train at rest on a siding along
Chapter 5 Light and Matter: Reading Messages from the Cosmos Messages Interactions of Light and Matter The interactions determine everything we see, including what we observe in the Universe. What is light?
Formation of the Solar System Any theory of formation of the Solar System must explain all of the basic facts that we have learned so far. 1 The Solar System The Sun contains 99.9% of the mass. The Solar
Black Holes & The Theory of Relativity A.Einstein 1879-1955 Born in Ulm, Württemberg, Germany in 1879, Albert Einstein developed the special and general theories of relativity. In 1921, he won the Nobel
WELCOME to Aurorae In the Solar System Aurorae in the Solar System Sponsoring Projects Galileo Europa Mission Jupiter System Data Analysis Program ACRIMSAT Supporting Projects Ulysses Project Outer Planets
15.6 Planets Beyond the Solar System Planets orbiting other stars are called extrasolar planets. Until 1995, whether or not extrasolar planets existed was unknown. Since then more than 300 have been discovered.
OVERVIEW DISTRIBUTION OF ELEMENTS IN EARTH S CRUST This lesson serves as an extension to the Howard Hughes Medical Institute short film The Day the Mesozoic Died. It provides an opportunity for students
Protobinaries von Cornelia Weber, Bakk.rer.nat. Overview Motivation Molecular Clouds Young Stellar Objects Multiplicity of YSO Orion Molecular Cloud Aims of my thesis Motivation Binary and Multiple system
Lecture 28 High Temperature Geochemistry Formation of chemical elements Reading this week: White Ch 8.1 8.4.1(dig. 313-326) and Ch 10.1 to 10.5.3 (dig. 421-464) Today 1. Stellar processes 2. nucleosynthesis
Name: Teacher: Pd. Date: Science Tutorial TEK 6.9C: Energy Forms & Conversions TEK 6.9C: Demonstrate energy transformations such as energy in a flashlight battery changes from chemical energy to electrical
PROJECT 4 THE HERTZSPRUNG RUSSELL DIGRM Objective: The aim is to measure accurately the B and V magnitudes of several stars in the cluster, and plot them on a Colour Magnitude Diagram. The students will
White Dwarf Properties and the Degenerate Electron Gas Nicholas Rowell April 10, 2008 Contents 1 Introduction 2 1.1 Discovery....................................... 2 1.2 Survey Techniques..................................
Chapter 8 Welcome to the Solar System 8.1 The Search for Origins What properties of our solar system must a formation theory explain? What theory best explains the features of our solar system? What properties
The Nature of the Physical World Lecture 19 Big Bang Cosmology Arán García-Bellido 1 News Exam 2: you can do better! Presentations April 14: Great Physicist life, Controlled fusion April 19: Nuclear power,
Your consent to our cookies if you continue to use this website.