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Questions and Answers
What letter best represents the location of Sirius on the Milky Way scale diagram?
What letter best represents the location of Sirius on the Milky Way scale diagram?
What letter best represents the location of Vega on the Milky Way scale diagram?
What letter best represents the location of Vega on the Milky Way scale diagram?
What letter best represents the location of M34 (Pleaides) on the Milky Way scale diagram?
What letter best represents the location of M34 (Pleaides) on the Milky Way scale diagram?
What letter best represents the location of M1 (Crab) on the Milky Way scale diagram?
What letter best represents the location of M1 (Crab) on the Milky Way scale diagram?
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What letter best represents the location of M71 (Globular) on the Milky Way scale diagram?
What letter best represents the location of M71 (Globular) on the Milky Way scale diagram?
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What letter best represents the location of the Sagittarius Dwarf Elliptical Galaxy on the Milky Way scale diagram?
What letter best represents the location of the Sagittarius Dwarf Elliptical Galaxy on the Milky Way scale diagram?
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What letter best represents the location of the Large Magellanic Cloud on the Milky Way scale diagram?
What letter best represents the location of the Large Magellanic Cloud on the Milky Way scale diagram?
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What letter best represents the location of the Andromeda Galaxy on the Milky Way scale diagram?
What letter best represents the location of the Andromeda Galaxy on the Milky Way scale diagram?
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All RR Lyraes have absolute magnitudes of about M = 0.5.
All RR Lyraes have absolute magnitudes of about M = 0.5.
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Type I Cepheids follow the same Period-Luminosity Relation as RR Lyraes.
Type I Cepheids follow the same Period-Luminosity Relation as RR Lyraes.
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What is the name of the project used in the Sloan Digital Sky Survey fly-through exercise?
What is the name of the project used in the Sloan Digital Sky Survey fly-through exercise?
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When looking at galaxies farther away, it can be determined that the closer the galaxies are together, the greater the change in distances.
When looking at galaxies farther away, it can be determined that the closer the galaxies are together, the greater the change in distances.
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What is the main feature that is visible in the universe at a distance bias, which is only visible at large distances, shown in the SDSS v4 exercise?
What is the main feature that is visible in the universe at a distance bias, which is only visible at large distances, shown in the SDSS v4 exercise?
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The black holes at the cores of normal galaxies are not eating much, which makes them visible in the SDSS v4 exercise.
The black holes at the cores of normal galaxies are not eating much, which makes them visible in the SDSS v4 exercise.
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The Hubble Constant is the slope of the best fit line on the graph that represents the recessional velocity of a galaxy versus the distance to the galaxy.
The Hubble Constant is the slope of the best fit line on the graph that represents the recessional velocity of a galaxy versus the distance to the galaxy.
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The 'Big Squeeze' is part of the future possibilities of the universe in the scale of the universe exercise. Which of these possibilities does not go through the 'Big Squeeze'?
The 'Big Squeeze' is part of the future possibilities of the universe in the scale of the universe exercise. Which of these possibilities does not go through the 'Big Squeeze'?
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In the "Elements in the Universe" exercise, the deuterium bottleneck prevents the formation of elements heavier than helium due to the inability of photons to break up larger nuclei.
In the "Elements in the Universe" exercise, the deuterium bottleneck prevents the formation of elements heavier than helium due to the inability of photons to break up larger nuclei.
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Study Notes
Nordgren Photography
- Tyler Nordgren is from the University of Redlands.
- His photography sites include Acadia and Big Bend.
- He gave a talk at UNL on YouTube in 2009.
Class 5.1 11/20/2024
- Exam 4 results ranged from 67.8 ± 19.6.
- Fourteen students still needed to take the exam.
- The 5 segments in the solar system were covered last week.
- Tonight's forecast was clear.
- Citizen science topics covered several fits well topics, including Tyler Nordgren Photography.
- Questions on the Milky Way Galaxy and variable stars as standard candles were discussed.
Milky Way Scale
- The distances to various stars are given in light-years.
- Letter A represents the location of Sirius, Vega, Spica, Rigel, and Deneb.
Milky Way Scale (Clusters)
- M34 (Pleiades) is 380 light-years away.
- M1 (Crab) is 630 light-years away.
- M71 (Globular) is 12,700 light-years away.
Milky Way Scale (Nearby Galaxies)
- Sagittarius Dwarf Elliptical Galaxy is 80,000 light-years away.
- Large Magellanic Cloud (LMC) is 160,000 light-years away.
- Andromeda Galaxy (M31) is 2,600,000 light-years away.
Conclusions
- Objects in the night sky are relatively close to us within the Milky Way.
- Bright stars and clusters are within our side of the Milky Way.
- Only three objects visible to the naked eye are outside the Milky Way, the LMC, SMC, and Andromeda Galaxy.
- All are very close to us within the universe.
Milky Way: Dwarf Galaxy Discovery
- The Sagittarius Dwarf galaxy is colliding with the Milky Way and will eventually be torn apart by tidal forces.
- It was discovered in 1994 (later than the Magellanic Clouds), though closer.
Clusters
- Globular clusters are contrasted with open clusters.
Astronomical Historical Overview
- 1600s: Copernicus, Brahe, Kepler, Galileo, Newton, and the nature of the Solar System.
- 1700s: Significant work on stars.
- 1800s: Herschel cataloged stars; a "grinding stone" model of the Milky Way.
- 1900s: Shapley and Hubble's work.
Harlow Shapley (1885 – 1972)
- Observed globular clusters, determining their distance using RR Lyrae stars.
- Mapped their locations and assumed the center of the distribution of globulars was the center of the Milky Way.
- Found the distance to the center of the Milky Way.
- Incorrectly believed "spiral nebulae" were within our galaxy.
The Great Debate
- The Shapley-Curtis Debate in 1920 involved scientists debating the scale of the universe.
- Shapley argued that spiral nebulae were nearby gas clouds within a single galaxy.
- Curtis argued for the existence of many galaxies like our own.
Edwin Hubble (1889-1953)
- Observed and categorized other galaxies.
- Used Cepheid variables to determine the distance to the Andromeda Galaxy—showing it was further than previously thought.
- Confirmed spiral nebulae as separate galaxies.
Stellar Profile: Polaris
- Polaris is near the North Celestial Pole (NCP).
- It's a triple star system.
- A yellow supergiant with a luminosity of 1,260 L☉.
- Surface temperature is 6,000 K.
- Radius of 38 R☉, mass of 5.4 M☉, and age of 70 Myr.
- It's a Cepheid variable star with a period of ~4 days.
- Located 430 light-years away, making it an important standard candle for distance measurements.
Class 5.2 11/22/2024
- NAAP 5 was distributed for class exercises on metallicity and rotation curves.
- Peer instruction covered metallicity and rotation curves.
- Summary exercises for 5.1 and 5.2 on MilkyWay Galaxy.
Discussion Question (Metallicity)
- How do stars obtain their metal content?
- What does a star’s metallicity indicate about the star?
- What does metallicity represent in terms of a proxy?
Standard Candles
- A standard candle is an object with a known luminosity.
Exercise 5.1b: Variable Stars as Standard Candles
- All RR Lyrae stars have an absolute magnitude of roughly 0.5.
- Observations of apparent magnitude, knowing the absolute magnitude, calculates distance.
- Cepheid variables obey a period-luminosity relation, making them valuable distance indicators.
- One observes the period, looks up the absolute magnitude, and then calculates the distance modulus to determine the distance. The period-luminosity relation connects the period of a Cepheid variable star to its luminosity.
WorldWide Telescope
- Explore the Milky Way in various wavelength bands was covered as exercise 5.1c.
Galactic Rotation Curve
- The orbital speed of stars in a galaxy increases in relation to their distance from the galactic center.
- The graph showing the circular velocity is the galactic rotation.
Class 5.3 11/25/2022
- Student Observatory information.
- Review tasks for the Milky Way, galaxy classifications exercises, discussion of galaxy types, galactic collisions, and gravitas were included.
Formative Assessment Task (on the Milky Way Galaxy)
- A task to sort characteristics into halo stars or disk stars bins.
Paisley Galaxies
- Type PY galaxy image cluster.
Hubble Tuning Fork
- Galaxy classification scheme.
Exercise 5.3b
- Classify sample galaxies.
Galaxy Collisions
- Illustrations of galaxy collisions.
Gravitas
- A combination of galactic collision simulations and contemporary music presented by John Dubinski.
Gravitas 2 on YouTube
- Video clip on Gravitas.
Class 5.4 12/2/2024
- Announcements and pre-survey scores’ updates.
- Wrap up of galaxy classifications.
- Practice exercises on distant object observations.
- Covers gravitational lensing and the Sloan Digital Sky Survey observations.
Looking at Distant Objects
- A class play to understand distances and look-back time by sending a signal to, and receiving a signal from, a distant object.
Looking at Distant Objects
- Numbers 5, 7, and 8 provide specific examples of these concepts.
Exercise 5.4a: Quasar Logic
- Shows the relation between redshift and distance.
- Explains how quasars appear as bright objects located at great distances.
- Uses Doppler shift and Hubble's Law to explain quasars.
Quasars
- Superluminous cores in the distant galaxies (caused by supermassive black holes consuming material).
Gravitational Lensing Demo
- Demonstrations of how gravitational lensing can be used to view distant objects.
Class 5.5 4/19/2024
- Announcements, SSDS data flythrough, review of look-back time, peer instruction on expansion of the universe through smartphone simulation, and Hubble's Law.
Sloan Digital Sky Survey Fly-Through
- Visual identification of nearby normal galaxies, zones of avoidance, distance bias affecting observations of luminous objects, quasars, and the Cosmic Background Radiation (CBR).
SDSS ver 4
- The Sloan Digital Sky Survey (SDSS) visual aspects and explanation from observations, including seeing the nearby, normal galaxies (not very old), big red galaxies, quasars, the cosmic background radiation, and the galaxy formations during the Big Bang.
The Universe at Increasing Distance
- A visualization showing how the universe changes by increasing distance and lookback time.
- Explains the types of objects astronomer can observe by distance, including local groups, more distant active galaxies, quasars, and the Cosmic Background Radiation (CBR).
Hubble's Law
- Relationship between recessional velocity and distance for galaxies.
Expansion of the Universe
- Galaxies appearing to get bigger as the universe expands.
- Comparing distances between galaxies to show expansion.
- Determining whether there is a center to the expanding universe.
Smartphone Sim: Expansion of the Universe
- A smartphone simulation exercise to explore Hubble’s law and observe how the universe's expansion affects our observations of galaxies at different distances.
Class 5.6 4/22/2024
- Announcements on exam 5, experiential project scores, peer instruction on the Hubble constant, class exercises on Hubble’s Law, exercise on the evolution of the universe, and the associated Tau Zero video clip related to dark energy.
Class Exercise 5.5 (Determining the Hubble Constant)
- Uncertainties in measuring recessional velocity of galaxies, including Doppler shifts and peculiar velocities.
- Calculating errors in distance with increasing distance.
- Plotting and analyzing data on the Hubble constant, plotting best fit lines (with error ranges).
Class Exercise 5.6b: Evolution of the Universe
- Examination of the past and future scale of the universe.
Tau Zero (1970)
- An award-winning science fiction novel by Poul Anderson.
- The book explores the concept of time dilation in relation to special relativity.
Video Clip (NOVA Runaway Universe)
- A short video clip on the topic of the runaway universe.
- Type I supernovae observations.
- How the expanding universe is observed.
Segment 5 Review (Day 4/24/2024)
- Announcements about the exam and the start of segment 6.
- Reviewing prior material on galaxy types, Hubble's law, and peculiar velocities.
Exercise 3.3a: Characteristics of Galaxies
- The nature of spheroidal and cylindrical components in galaxies, and the presence or absence of various types of stars.
Have Active Star Formation
- The distinguishing features of spiral and elliptical galaxies, as well as their relationship to star formation, galaxy mergers, and their representation in galactic catalogs.
Smartphone Sim: Hubble's Law
- Questions about the universe simulations and how Hubble’s law correlates to distance.
Big Bang?
- Visualization of the Big Bang event.
Class Exercise 5.6a: Big Picture View of the Big Bang
- An overview of the Big Bang.
Exercise 5.6 (Big Picture Evolution of the Universe)
- Directions, facts, pivotal events, and locating a point in time when the universe was half its current age.
- The early universe with most energy in the form of radiation is presented in the exercise.
- Element building, recombination, and galaxy formation (and the first stars forming).
Recommended Demonstration Video
- "Shape Memory Allows"—a demonstration of a phase change analogous to inflation.
- Relevant video information (dimensions and duration).
WMAP
- Information about the Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft and its studies of the cosmic background radiation (CBR).
- Explanation including connections between the CBR structure and matter density at the time of recombination, galaxy formation seeds.
Exercise 5.6c: Elements in the Universe
- Studying the formation of elements in the universe and the mechanisms involved.
WMAP (What’s in the Universe?)
- Percentage composition of the universe (based on WMAP data) at the present time and 13.7 billion years ago.
Studying That Suits You
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Description
Test your knowledge on the Milky Way Galaxy, variable stars, and distances in light-years. This quiz also touches on citizen science and the work of Tyler Nordgren in photography. Prepare for questions related to recent class discussions and star clusters.
