Podcast
Questions and Answers
A spherical galaxy, like M87, which looks like a monster globular cluster, is type?
A spherical galaxy, like M87, which looks like a monster globular cluster, is type?
- ES1
- ES
- E0 (correct)
- 0V
- S0 (correct)
The flattest of the ellipticals are class?
The flattest of the ellipticals are class?
- SBF
- E0
- SBO
- E9
- E7 (correct)
The Large and Small Magellanic Clouds fall into Hubble's class?
The Large and Small Magellanic Clouds fall into Hubble's class?
- Irr I (correct)
- SBc
- E3
- Pec
- E6
When mass is accreted into a black hole, how much total mass-energy can be radiated away?
When mass is accreted into a black hole, how much total mass-energy can be radiated away?
The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ________ according to Hubble.
The Milky Way is often considered to be an intermediately wound, barred spiral, which would be type ________ according to Hubble.
The greatest variation in size, mass, and luminosity occurs in?
The greatest variation in size, mass, and luminosity occurs in?
Which of the following is NOT one of Hubble's types of galaxies?
Which of the following is NOT one of Hubble's types of galaxies?
Within the boundaries of the constellations Coma and Virgo are found?
Within the boundaries of the constellations Coma and Virgo are found?
Most of the galaxies in the Local Group are?
Most of the galaxies in the Local Group are?
What is the nearest huge cluster of galaxies to our Local Group?
What is the nearest huge cluster of galaxies to our Local Group?
The Tully-Fisher relation exists between the galaxy's luminosity and its?
The Tully-Fisher relation exists between the galaxy's luminosity and its?
What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong?
What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong?
Why does the Cepheid 'standard candle' have limited usefulness beyond 20 Mpc?
Why does the Cepheid 'standard candle' have limited usefulness beyond 20 Mpc?
Which of the following paraphrases Hubble Law?
Which of the following paraphrases Hubble Law?
What is true of spiral galaxies?
What is true of spiral galaxies?
For finding the distance to M31 (the Andromeda galaxy at 0.78 Mpc), Hubble relied upon?
For finding the distance to M31 (the Andromeda galaxy at 0.78 Mpc), Hubble relied upon?
According to Hubble's Law, the greater a galaxy's redshift, the?
According to Hubble's Law, the greater a galaxy's redshift, the?
While examining the spectrum of a galaxy you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is?
While examining the spectrum of a galaxy you find all the hydrogen lines are shifted to longer wavelengths. This galaxy is?
Quasars usually have their distances measured by what technique?
Quasars usually have their distances measured by what technique?
That quasars were at cosmological distances yet appeared like ordinary faint stars meant?
That quasars were at cosmological distances yet appeared like ordinary faint stars meant?
Quasar's spectral lines are?
Quasar's spectral lines are?
Why is the energy source for active nuclei like Seyferts thought to be compact?
Why is the energy source for active nuclei like Seyferts thought to be compact?
In what sense are the quasars 'quasi-stellar'?
In what sense are the quasars 'quasi-stellar'?
If we are directly in the line of a jet coming out of the lobe galaxy's core, we see a?
If we are directly in the line of a jet coming out of the lobe galaxy's core, we see a?
The huge lobe radio galaxy at the center of the Virgo Supercluster is?
The huge lobe radio galaxy at the center of the Virgo Supercluster is?
The quasars with the largest presently known redshifts are close to?
The quasars with the largest presently known redshifts are close to?
A billion solar mass black hole would still have a radius of only?
A billion solar mass black hole would still have a radius of only?
Which of the following does the intensity of synchrotron radiation NOT depend on?
Which of the following does the intensity of synchrotron radiation NOT depend on?
The type of radiation coming from active nuclei due to electrons spiraling in very strong magnetic fields at relativistic speeds is?
The type of radiation coming from active nuclei due to electrons spiraling in very strong magnetic fields at relativistic speeds is?
Synchrotron radiation produces a ________ spectrum.
Synchrotron radiation produces a ________ spectrum.
The energy radiated by a typical quasar requires that its black hole accrete about?
The energy radiated by a typical quasar requires that its black hole accrete about?
Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiated energy.
Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiated energy.
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Study Notes
Galaxy Types and Classifications
- M87 is classified as a spherical galaxy, resembling a globular cluster, identified as type E0.
- The classification of elliptical galaxies ranges from E0 (flattest) to E7; E7 is the flattest elliptical.
- Hubble's classification places the Large and Small Magellanic Clouds under Irr I, indicating irregular galaxies.
- The Milky Way is categorized as an intermediately wound, barred spiral galaxy, specifically type SBb.
Mass and Energy in Black Holes
- About 20% of total mass-energy can be radiated away when mass is accreted into a black hole.
- The phenomenon of black holes is influential in understanding the dynamics of immense regions of space.
Local Group and Galaxy Clusters
- The Virgo Cluster represents the nearest huge cluster of galaxies to our Local Group, containing thousands of galaxies.
- Local Group galaxies predominantly consist of small irregulars and ellipticals, including companions of M31 in Andromeda.
- Regions within the constellations Coma and Virgo comprise the largest nearby super-clusters of galaxies.
Distance Measurement Techniques in Astronomy
- The Tully-Fisher relation correlates a galaxy's luminosity with its rotation speed.
- Cepheid variables in the spiral arms of M31 (Andromeda) were key to determining its distance by Hubble.
- Quasars' distances are typically measured using Hubble's Law, which relates redshift to distance.
Observations and Theories of Active Galaxies
- The spectral lines of quasars exhibit emission lines with large redshifts, indicative of their significant distances and energy outputs.
- Active nuclei sources, like Seyfert galaxies, are considered compact due to rapid light variability.
- Quasars create the appearance of being stellar because they are extremely bright over vast distances.
Black Holes and Synchrotron Radiation
- A billion solar mass black hole has a surprisingly small radius of only 20 AU.
- Synchrotron radiation arises from electrons spiraling in strong magnetic fields and produces a continuous non-thermal spectrum.
- The intensity of synchrotron radiation is independent of temperature, influenced instead by electron speed and magnetic field strength.
Quasars and Their Characteristics
- Quasars may require their black holes to accrete about one solar mass per year to emit their immense energy.
- They are observed as ordinary faint stars, but their luminosity greatly exceeds that of typical stars due to enormous energy outputs.
- Quasar jets result in observable features like blazars when viewed along the jet direction.
Redshift and Cosmic Expansion
- According to Hubble's Law, a greater redshift indicates a galaxy is farther from us, reflecting the universe's expansion.
- Distant galaxies show redshifts in hydrogen lines, indicating they are moving away from the observer.
Conclusion
- Understanding these concepts is essential for grasping galaxy classification, distance measurement, the dynamics of black holes, and the nature of cosmic entities such as quasars and active galactic nuclei.
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