Astronomy 309C Final
For young stars forming in the Orion nebula close to a massive star, within what distance to the massive O star do the baby stars suffer and completely lose their disk and/or envelope of material? Beyond this distance, what masses of the disks around the protostars do researchers observe?
0.1 light years; Disk masses ranging from 1-80 times the mass of Jupiter
Describe the different stages that protoplanetary disks can go through. For each stage, or type of disk, list the physical characteristics of that disk. (Hint: there are 4 main disk types or stages, and this question is specifically asking about the disks, not the overall characteristics of the young protostar)
1 - Massive flared disk - much more extended, disk is flared outwards. The accretion disk is large and increasing in this stage. 2 - Settled Disk - disk has more structure and is settled more along the mid plane. Still a large accretion disk at this stage, but disk growth / accretion is starting to slow down at this stage. 3 - Photoevaporating Disk - gas closest to the star has been evaporated or blown away by the star itself. Left with less material in the disk, some gas and dust still left by more in the outer portions of the disk. 4 - Debris Disk - left over remnants of the disk. All of the gas is gone, just left with a little dust and other rocky debris.
Which law relates the power emitted from a star per square meter with its temperature?
Stefan-Boltzmann Law
Rank the following from earliest to latest in terms of the beginning stages of star formation: dense cores are formed, cloud of gas, collapses gravitationally to form clumps
1 - cloud of gas 2 - collapses gravitationally to form clumps 3 - dense cores are formed
For a star like the sun, after it leaves the MS how much time will it spend in the Red Giant phase?
1.3 billion years
How long do disks around stars last?
10 million years or less
What temperature is the molecule gas phase of the interstellar medium (ISM) typically at?
10K
The Milky Way galaxy is thought to contain how many globular clusters?
150-200
When was the very first credible exoplanet discovered, and what type of parent star was it discovered around?
1995; a sun-like star
Based on observations from the Dawn spacecraft, when did the asteroid Vesta become assembled?
2 million years after the first solids in the Solar System condensed and started sticking together
One of the most distance galaxies we have been able to observe, and confirm, is producing stars at a rate of _____, compared to the rate of the Milky Way which is only producing stars at a rate of ______.
300 solar masses per year; 1-2 solar masses per year
At least ____ of all stars are thought to be found in binary star system
50%
Why do we find rocky material everywhere in the solar system, but large amounts of volatile material only in outer regions? Would you expect the same to be true of other solar systems? Explain your answer.
A planet's composition depend on the location in the solar system in which it was formed. This composition also depends on what materials were able to condense out of the solar nebula, which is determined by its distance from the Sun. Although rocky materials are found everywhere in the solar system, larger amounts of volatile materials are found specifically in the outer regions. This is due to the fact that temperatures in the outer regions were much cooler early on in the solar system's lifetime, allowing for planets in these areas to accrete solid volatile material when the warmer inner planets couldn't hold on to gaseous volatiles. Disk temperature is a function of the disk's distance from the Sun.
If we were to get extremely lucky, what type of structure did the video identify as a far out possibility of detecting around an advanced alien civilization?
A ring world, a giant artificial structure around a planet
A star (or protostar) is often described as "moving" on an HR Diagram; why is this description used, and what is actually happening with the star?
A star or protostar is said to move on the HR Diagram because its physical properties, which are plotted on the HR diagram, are what is changing as the star goes through different evolutionary stages in its lifetime. The star / protostar is not physically moving in space, or along a physical track in space. Instead, what is actually happening is that the star's luminosity and temperature change with time or at different evolutionary stages. For example, as the protostar starts out it moves along the Hayashi Track with it's temperature staying relatively constant but its luminosity and radius decreasing as the star is contracting. Another example, is as the star leaves the Main Sequence and moves up the Red Giant branch, the star gets bigger in size (radius increases) and it gets cooler, it is becoming a Red Giant, this also causes its luminosity to increase.
With what type of electromagnetic radiation would you observe: A) A star with temperature 5800K? B) A person on a dark night?
A) Visible; B) Infrared
Match each of the types of spectra with its correct description: Absorption, Continuous, Emission
Absorption - produced by passing white light through a cool, low density gas Continuous - produced by solid/very dense gas giving off radiation Emission - produced by a hot, low density gas observed directly
How often do we observe jets evolving around protostars?
jets visibly change over human timescales, even shorter timescales of 10 years or more
What do astronomers mean by bipolar outflow?
Bipolar Outflow: Gas that is ejected / launched from ends (both poles) of an object, rather than uniformly in all directions (spherically) is considered to be a bipolar outflows. Protostars can have bipolar outflows and very collimated jets.
Based on the computer simulations run by the authors (Raymond et al.) in the last study/paper, match the list of possible options what mechanism or feature frequently causes inner terrestrial planets to be cleared out? In contrast, what feature in their simulations often resulted in systems with terrestrial planets forming and being retained?
Causes inner terrestrial planets to be cleared out - perturbations to the gas giant planets, giving them elliptical orbits Allows for inner terrestrial planet to be maintained - systems with debris disks
How can we explain why the asteroid (and dwarf planet) Ceres formed with a larger amount of water than its neighbor, Vesta, which is also an asteroid and dwarf planet? Both asteroids now reside in the asteroid belt and at roughly similar distances from the Sun (2.8 and 2.4 AU, respectively)
Ceres likely formed in a colder outer region of the early Solar System than Vesta, giving it a larger water content as it formed beyond the snow line. It then later migrated inwards to its current location in the asteroid belt, close to Vesta
Consider the two different models that have been proposed for formation of the gas giant planets, core accretion and gravitational disk instability: a) Briefly describe each of the two different models b) Discuss the advantages and disadvantages that each model has.
Core Accretion Model: 3-10 million years Orbiting dust --> planetesimals --> planetary embryos --> planets Pros: Explains composition of giant planets and why they're different from the Sun Method by which terrestrial planets form Cons: Takes too long to build up planetesimals through collisions Hard to form gas giants at large distances Gravitational instability: protoplanetary disk of gas and dust forms around a young star. Gravitational disk instability --> clump of gas --> self-gravitating planet --> dust grains --> core. Pros: may be natural for disks to be gravitationally unstable; Happens very fast; explains why gas giants can form at large distances Cons: Disks are usually not ; Doesn't easily explain the differences between compositions of planets
In a region of massive star formation/HII region, what type of object did researchers first see emerging from the edges of the HII region?
Evaporating Gaseous Globules (EGGs)
Why are old Globular clusters still around today and how were they able to survive the collisions that their original host galaxy went through?
Globular clusters survived because they were the most massive ones. The many smaller clusters were destroyed during bursts of star formation that occurred during galaxy collisions
In the protoplanetary disk, where can each substance exist as a solid?
Hydrogen/Helium - Outer Region Hydrogen Compounds - Intermediate Region (0.3-3.5 AU) and Outer Region Rocks/Metals - Inner Region (inside 0.3 AU), Intermediate Region (0.3-3.5 AU), Outer Region
A typical temperature of intercloud gas is 8000K, whereas the typical temperature of a cold molecular cloud is 100K. Using Wien's Law calculate the peak wavelength each of these clouds will radiate at. Which parts of the electromagnetic spectrum is the peak emission from each cloud being emitted in (e.g. x-ray, UV, visible, infrared, radio, microwave)?
Inter cloud gas temp = 8000K; Molecular cloud - 100K; Wien's Law: 2900/temp; 2900/8000 = 0.363 microns = 363nm; 2900/100 = 29 microns; therefore the warm intercloud gas will radiate in the UV near UV and the molecular cloud will radiate in the IR
What unstable isotope (or leftover products from it) was found relatively recently in meteorites giving evidence for the newly formed Sun and Solar System to have formed near a massive star?
Iron-60
What happens to the light we observe here on Earth from very distant galaxies?
It gets shifted to longer, redder wavelengths because of the expanding universe
What likely happened to all the material in the inner part of the early Solar System that didn't have high enough melting points?
It would have vaporized
The exoplanet Kepler-186f is the first earth size exoplanet discovered in the habitable zone around another star but what is the main difference between this planet and Earth?
Its parent star is cooler and dimmer than our Sun
What do observed kinks in jets tell us about them?
Kinks in jets show how the direction of the outflowing jet has changed over time
A protostar evolves from a temperature of T = 3500K and a luminosity L = 5000 times that of the Sun (L = 5000L) to T = 5000 and L = 3L. What is its radius (in units of solar radii) at a) the start, and b) the end of its evolution?
L - R^2xT^4; w/L in units of solar luminosities, temp in units of T = 5800K (also solar temp units) R = square root of L/T^4 at start of evolution L = 5000 L, T = 3500K; T in solar units = 3500K/5800K = 0.603; Radius = square root of 5000/(0.603)2 = 194.5R; radius at start = 195 solar radii at end of evolution L = 3L, T in units of 5800K; T = 5000/5800 = 0.862; R = square root of 3/0.862)2 = 2.33 R; radius at end = 2.33 solar radii
When we observe distant galaxies, we are essentially doing what?
Looking back in time, seeing what the universe looked like much earlier
Compare the temperature of the protoplanetary disk at the orbit of Mercury (0.5 AU) and Jupiter (5 AU).
Mercury at 0.5 AU is over 1,000 K while Jupiter at 5 AU is around 200 K. Water boils at 373.16 K and water freezes at 273.16 K so Mercury is well beyond the boiling point and Jupiter is just under the freezing point. So at Jupiter's location water condenses to form ice.
Galaxies grow and change with time by what main mechanism?
Mergers of galaxies and accretion of smaller galaxies
List which type of rock from the following list is the best source for age dating the Solar System through radioactive dating: Moon rocks, Earth rocks, or Meteorites. In addition, describe the reasons why the type of rock chosen is the best source for age dating, as opposed to the other ones listed.
Meteorites are the best source for age dating, then comes moon rocks. Earth rocks cannot help us understand the age of the Solar System because geologic process on earth causes rocks to melt and re-solidify. We can only age date from the last solidification. We have to find rocks that have not melted or vaporized since they condensed from the solar nebula. That is why meteorites are the best option for age dating at 4.6 billion years old; they would have an older solidification date. Moon rocks are still a good source of knowledge but they are not the best.
A molecular cloud core has a density of 10^6 particles/cm^3, a temperature of 100K, and a total mass in the core of 100M. a) What in the Jeans Mass (in solar masses) required for collapse of this cloud fragment? b) Will this molecular cloud core be able to collapse? Why or why not? c) If it does star the collapse process, how long will it take for the cloud core to completely collapse, assuming the initial density is the same everywhere in the cloud.
Mjeans = 50xT^3/2/square root of n; T = 100K, n = 10^6 particles/CM^3 a) 50M b) Yes, the cloud core will be able to collapse because the mass of the cloud is greater than the Jeans Mass, which is the minimum mass needed for collapse to begin, given the initial conditions of the cloud (temp and n). C) Free-fall time, tff = 3.4x10^7/square root of n (in years); tff = 3.4x10^7/square root of 10^6 = 34,000 years
Which of the answers listed below is not a possibility for why we don't see thousands of dwarf galaxies around the Milky Way?
No small, dwarf galaxies ever formed in the first place. Only large massive galaxies like the Milky Way were formed right off the bat
Choose the correct ranking of main sequences stars based on their spectral type (color/temperature), from hottest to coolest
OBAFGKM
What can we learn about the formation of our solar system by studying other stars? Explain.
Observing other stars allows us to see that different types of planets and planet formation begins in the same location. Observing other stars can also help us understand how planets formed in systems with stars similar to our own Sun by observing the many stages those stars go through.With these observations we can validate the core accretion theory and use it (along with other star observations) to prove that terrestrial planets are located closer to their star while icy planets are located further away.
The Sun likely took approximately 40 million years (4.0X10^7) years to evolve from a collapsing cloud core to a star, with 10 million of those years on the main sequence. Suppose we were to compress the Sun's main-sequence lifetime into just a single year: a) How long would the total collapse phase last in hours? Assuming the Sun's birth began on midnight of January 1, on what day/hour would the entire collapse process have finished? b) How long would the Sun have spent on its Hayashi track on this scale? Give your answer in hours, and specify which day this would have happened on.
Part (a) - 10 billion years = 1 calendar year = 365 days 40 million years / 10 billion years = 0.004 0.004 * 365 = 1.46 ~ 1.5 days, therefore on approximately Jan. 2nd at noon collapse process / pre-main sequence evolution would have ended. Accept anything around these numbers and can be in the form of either Jan 2nd around 11am / noon, or 1.5 days, or 35-36 hours. Part (b) - 10 million / 10 billion = 0.001 = 0.365 days on this scale or 8.8 hours. Accept around 8 or 9 hours. Or would have lasted until 8 or 9 am on January 1.
Describe the differences between low-mass and massive stars. a) Related to the type of environment they are most commonly or likely to have formed in. b) Related to their evolution/lifetimes on the main sequence, as well as time it takes them to reach the main sequence. c) Related to their end states after they leave the main sequence (i.e. what do they end up as?)
Part a - Environment stars formed in: Massive stars have to form in the most massive, dense environment, i.e. the larger molecular clouds / star forming nebulae, or clustered environments. Low mass stars can form in either the massive star forming regions, or in smaller, isolated clouds. Part b - Evolution / Lifetimes: Low-mass stars will evolve much slower than the massive stars. They take longer to evolve on to the main sequence, and once there they will have much longer lifetimes. Massive stars evolve quickly, get to the main sequence much more quickly, and will have shorter lifetimes. Part c - End states: Massive stars end up as either Neutron stars or black holes Low mass stars will end up as white dwarfs.
Consider two observations, taken 5 years apart, of the same Herbig Haro object with a jet, and the jet appears to move a distance of 250 AU between the first observation and the second observation (5 years later). a) How fast is that jet moving in km/s? b) Compare this to the typical speeds of jet airplanes (a different kind of jet) that travel at average cruising speeds of 900 km/hour.
Part a.) Distance = 250 AU, time = 5 years. Velocity needs to be given in units of km / s = 250 km/s. (Depending on the exact value of the constants used some students might get this as 237 km/s, which is fine). Part b.) Airplane speed = 900 km / hr, or = 0.25 km/s in the same units as part a). The interstellar jet moves with a speed that is 1000 times faster than typical jet airplanes.
What method of searching for ET is most related to Drake Equation?
Passively listening to signals from stars and planets
Describe at least two different mechanisms that can cause "triggered" star formation. Make sure to describe physically what is going on for each mechanism (not just a list of kinds of mechanisms).
Possible mechanisms to choose from are: Supernovae induced star formation, this occurs from the shock wave produced by the supernova itself, which compresses a nearby cloud of gas, and starts the collapse process & second generation of stars start to form. A second possible mechanism is: shock waves and ionization fronts given off by the massive stars, i.e. expanding HII regions which compresses the gas, same way as above which then leads to new star formation. A third mechanism is spiral density waves in spiral arms of the galaxy. Can use the traffic jam analogy to explain. Gas getting caught up / piling up, slowed down in the spiral arms as they pass through. They get compressed and this leads to star formation in the arms. A 4th mechanism that could be used is mergers in galaxies, i.e. starbursts in galaxies, super star clusters.
Describe three different methods for detecting extrasolar planets. For each method, explain whether it is a direct detection method or an indirect detection method and why.
Radial Velocity/Doppler Spectroscopy (Indirect) Transit Spectroscopy (Direct) Direct Imaging (Direct)
What wavelength observation did astronomers use to detect one of the earliest stages of star formation process?
Radio and Infrared observations
What is currently the best proposed mechanism to explain the existence of the inner Oort Cloud, based on observations of the two members, Sedna and 2012 VP113?
Scattering of leftover planetismals due to close encounters of the young Sun and other stellar members of its birth star cluster
Describe how, on average, spiral galaxies and elliptical galaxies appear different. Discuss differences between their colors and shapes. What is one of the main reasons for why these two types of galaxies have difference in their appearance?
Spiral- younger, active star formation, spiral arms- bluer elliptical- older stars, redder, no active ongoing star formation amount of gas and dust determines activeness of star formation
Discuss which phase of the interstellar medium is the site where stars form. Discuss the properties of this part of the interstellar medium, and explain why it is the ideal location for star formation as opposed to other parts of the interstellar medium.
Stars are born out of the molecular gas phase of the interstellar medium. This phase of the ISM is made up of mostly hydrogen gas in the molecular form (H2), along with a little bit of dust and other molecules. This phase is the coldest and densest part of the ISM, making it the ideal location for star formation to begin. A cloud needs to be dense enough that it will collapse under its own weight, once the force due to gravity becomes greater than the gas pressure of the cloud. Other phases of the ISM (neutral of ionized) are much less dense, and much hotter, therefore clouds in these parts of the ISM won't collapse, and therefore star formation cannot happen there. Only in the molecular cloud phase.
Describe two different mechanisms that can be a hazard to planet formation.
Supernovae explosions can be hazardous to planet formation because of the high amounts of energy shooting out into the area. Nearby protostars and the planets beginning to form could be hindered by these explosions. Extreme ultraviolet regions can also destroy the disks around young protostars. This causes proplyds to lose up to a half of the mass necessary to create Jupiter- sized planets.
Select the statement that best describes the TRAPPIST-1 system
TRAPPIST-1 is a system of seven earth-sized planets, with three located in the habitable zone
In the first article about comets, researchers had to make a number of assumptions about comets, and the early solar system formation. What was the biggest assumption they had to make for their model?
That the extended scattered disks of comets around the stars would have formed early enough, perhaps as early as 3 million years in to the formation in the Solar System
What observations of the Moon have resulted in a revised theory for how the Moon formed due to the collision model?
The Moon has almost the exact same chemical composition as the Earth for certain isotopes, and if the Moon had formed from a collision between the Earth and Mars-size objects then it should have the chemical signature of both parent bodies, and not just the Earth
Is the sun an average star? Why or why not?
The Sun is not an average star because its mass is greater than the majority of the stars plotted. There are more stars in the first mass bin (0.08 - 0.5 solar masses), and the Sun falls in the next bin. Overall, there are many less stars above 0.5 solar masses.
According to researchers and their models presented in the first article, how did the Solar System obtain such a large number of comets especially those at very large distances from the Sun?
The Sun was able to snag and capture ejected comets from other stars as the young Sun passed nearby the other stars in the stellar cluster, from which the Sun was born in
The observations of the exoplanet system HR 8799, give supporting evidence to which gas giant planet formation theory?
The core accretion model
What is one of the main differences in the timescales of gas giant planet formation between the two main competing theories of gas giant planet formation?
The core accretion model takes a long time to start the process for gas giant planet formation, whereas the gravitational instabilities in the disk model can create gas giant planets very quickly in one step
The revised Drake Equation in the article about the possibility of life on other worlds attempts to address or calculate what factor, as compared to the original Drake Equation which looked to estimate the number of advanced alien civilizations?
The fraction of planets with gases in their atmospheres that can be produced by lifeforms
What is the best piece of evidence that astronomers are using to infer the presence of a Planet 9 in the Kuiper Belt?
The highly elliptical and clustered orbits of some of the Kuiper Blet Objects
Briefly describe the three main types of clusters of stars that can form. For each cluster type, list the typical numbers of stars that may be found there, how they form or what environment they may form in, and whether we find old or young stars there.
The three types of clusters are: globular clusters, open clusters, and super star clusters. Typical numbers of stars: globulars = 10,000 - millions; open clusters = 100's - 1000's of stars; super star clusters = 1000's - 10's of 1000s How they form: open clusters form in recent star formation areas, large star forming regions. Need enough stars / mass in the cluster relative to the original mass in the cloud for the cluster to stay gravitationally bound, related to the star formation efficiency (but they are not required to explain the star formation efficiency). Globular clusters can form by a few possible different mechanisms, (they just need to list one): mergers of galaxies early on; smaller dwarf galaxies being accreted, globular clusters = remnants of these early smaller galaxies; or just discuss how the parent molecular clouds had to have been much more massive, denser, etc. For super star clusters talk about how they are from recent star formation but are more extreme, such as being formed due to star formation outburst in a galaxy due to merging, more gas available results in a big burst of star formation and a large super star cluster. Types of stars present in them: Globular clusters = old stars Open & Super star clusters = young stars.
What combinations of techniques have scientists used to discover and identify these organic molecules around young stars?
They used a combination of lab experiments involving exciting molecules and measuring their colors and then comparing it to the observations taken with the ALMA of star forming regions
The Kepler Space Telescope uses which method to detect exoplanets?
Transit method
What method is best for age dating objects in the Solar System like the Earth and Moon
Using the radioactive decay method with rock samples
The peak _______ of a star's emission depends on the star's _________. This is known as Wien's Law.
Wavelength; temp
Match the type of star with its correct approximate location on the HR Diagram: White Dwarf, Red super giant, hot MS, the sun
White Dwarf - lower left, Red super giant - upper right, hot MS - upper left, The sun - in the middle
Based on the articles on binary star formation, match the two types of binary systems with the most likely formation mechanism: Widely separated binaries, close in binaries
Widely separated binaries - fragmentation early on in the larger cloud before the young stars start to form Close in binaries - fragmentation of the smaller disk around a younger protostar
Scientists used what telescopes to observe and confirm the existence of the TRAPPIST-1 exoplanet system?
a small ground-based telescope, called TRAPPIST, a large ground-based telescope called the Very Large Telescope (VLT), and the Spitzer Space Telescope
Present theory suggest that giant planets cannot form without condensation of water, ice, and other volatile materials (which become vapor at high temperatures close to a star). So how can we explain the presence of gas-giant (Jupiter-sized exoplanets closer to their star than Mercury is to our Sun? Discuss at least two physical mechanisms or ways for how close-in gas giant planets ("Hot Jupiters") may have stabilized their orbits.
a) The Jupiter-sized gas-giants could have been formed somewhere else and moved to where it is now. Gas giants need to form at the outer region past the frost line and then likely move in closer to the star after formation. This can happen due to gravitational interactions with other systems, flinging the planet inwards towards the star. The magnetic field of the star keeps the planet from crashing into the parent star. Hot Jupiter planets head in towards their stars by gravitational or tidal forces of a star, circularizing and stabilizing a planet's orbit; when the orbit finally becomes circular, the migration ceases. b) The tidal forces theory proposes that a migrating planet stops once the star's orbit has circularized because of the tidal forces. Scientists looked at 126 planets' distance from their stars and found that the distance varied depending on the mass of a star. This theory predicts that hot Jupiters of more massive stars would orbit farther out on average. The results of this study correlated with massive stars having farther out orbits. The star's magnetic field preventing the planets from going any farther is another theory. Because a star is so heavily surrounded by debris when it is forming, material falls onto the star. Accretion can cause a magnetic bubble called the magnetosphere. This magnetosphere could by stopping the migrating planets.
As of 2015, Saturn has 62 known moons, with confirmed orbits. a) Calculate the Roche limit for Saturn in units of km. Saturn's radius = 58,232 km b) How many of Saturn's Moons are within the Roche limit? c) How are they able to exist there?
a) d = 2.4(Rplanet) d = 2.4(58,232km) = 139,756.3km = Saturn Roche Limit b) 4 out of the 12 mons are within Saturn's Roche Limit c) the moons that are able to exist within the Roche limit have a higher density and are composed of materials that are not as easily pulled apart / broken apart
Why do we often want to observe molecular clouds with infrared (IR) wavelengths?
because longer IR light can penetrate into molecular clouds, and does not get blocked like visible light does. In addition, cool dust in these clouds will radiate in the IR
a) Make a sketch of an HR diagram. Label the x-axis and y-axis, surface temperature (K) and luminosity, respectively. You don't have to put numbers on your axes, but you can if it is helpful to you. b) On your HR diagram, draw and label the Main Sequence. Mark/Label on the Main Sequence where high-mass and low-mass stars will be found. c) If you have a cluster of stars that were all born approximately the same time, and you make an HR diagram of this cluster, what does the Main Sequence turn off point (at any given time) tell you about this specific cluster of stars?
c) The Main Sequence Turn off point on the HR diagram for a cluster of stars tells us the age of that cluster. This can be estimated based on the mass of the stars right at the Turn off point, because we know the approximate main sequence lifetime of star of a given mass.
In the spiral arm density wave theory, as a mechanism for triggering new star formation where do the clouds get compressed in regards to the traffic analogy?
clouds get compressed when they hit the traffic jam, which is this analogy is the spiral arm
What analogy was used to help describe the initial mass function of stars?
collecting the weight of all the people in the room and plotting up that distribution in analogous to plotting the initial mass function for stars
In the star forming regions W5 there is evidence for how many generation of stars, and which objects/types of stars represent the first generation in this region?
evidence for 2-3 generations of stars; the massive O stars at the center represent the first generation
As a protostar is formed, what happens to it?
gets hotter and denser
What ingredients in the early solar system appears to be more important for the formation of gas giants, but not as necessary for the formation of terrestrial planets?
ices
The HR Diagram is a plot of what?
intrinsic brightness of stars versus their surface temperature
What is the Cosmic Microwave Background (CMB) radiation? Why is the CMB referred to as the first baby picture of the universe?
leftover electromagnetic radiation from the Big Bang; represents accurate depiction of what the Universe was like after the Big Bang
A brown dwarf is defined as a failed star with a mass
less than 1/12 that of the sun but larger than 1/100 of the sun
What conditions are needed in the gas to start the process of forming stars?
low temp, high density
In the video of the star forming region Sharpless 106 besides ionizing and heating up the gas surrounding the young massive star, what else is the massive star doing to the cloud around it?
making the gas more turbulent or clumpy, it is churning it up
What mechanism have researchers recently found to be the best way to explain how inward migration of gas giant planets comes to a stop?
migration stops once the tidal forces from the star have been able to circularize the planet's orbit
What do scientists think may be causing the gaps seen in the disk around the protostar HL Tau?
newly forming planets that are clearning out the disk
According to a research study using Kepler data, what fraction of Sun-like stars in our galaxy are thought to have an Earth-like planet in the habitable zone? This fraction translates to how many total planets?
one-fifth; 40 billion
Most stars, including the Sun are thought to form in what type of cluster?
open clusters
The new revised Kepler mission, or K2, uses what additional effects to help stabilize
pressure from sunlight
Which detection method(s) is (are) necessary in order to determine an exoplanet's density, and therefore its composition - whether it is a gas giant or rocky planet?
radial velocity and the transit method
The pre-MS evolutionary track for a 1 solar mass star remains nearly vertical (Hayashi track) for a while. How is its radius changing during this time? Its temp?
radius is decreasing, temp stays roughly the same
What can spur on and trigger the collapse of a clump of molecular gas to start the star formation process?
stellar winds or a supernova explosion
Based solely on detection number or frequency, Kepler has found the most of what type of exoplanet?
super earth or sub-neptune sized planets
The observations of which elements in the system HR 8799, specifically their ratio relatively to one another, were the important observations for providing clues to the theories of giant planet formation?
the amount of carbon relative to the amount of oxygen
The average lifespan of HII regions of typically a few million years is comparable to:
the lifetime of the most massive OB stars which create HII regions
In the Seager equation (the revised Drake equation), what two parameters are most confident about their values at this time? In other words, which parameters do we feel very confident about their values, compared to others where we may just have to guess?
the number of stars bright enough to observe the fraction of planets that can be observed
What part of the early solar System was water likely to have been found?
the outer part
One main limitation of the microlensing technique for detecting exoplanets is?
the planets detected by microlensing will not be observed again
Explain in your own words why we can think of galaxies as time machines.
the speed at which light travels is not instantaneous enough for us to be able to observe recent data
What observation did the astronomers use to determine that a massive star was ejected from the cluster (LH 82) it formed in?
they found a bow shock associated with the massive star and the shape of the bow shock showed the direction of the star's motion
Brown dwarfs may look more like giant gas planets but we think most of them may form like stars. If this is the case how or why do we think brown dwarfs stalled and didn't turn into stars?
they start forming in a nebula with other pre-stella cores but got ejected out of the nebula before they could gain enough mass
What is so special about finding the specific sugar molecule (glycoladehyde) in the disk around a young nearby star?
this specific simple sugar molecule is one of the components in the formation of RNA, one of the building blocks of life
