galaxy types questions
name ______
1. how many stars are in a galaxy?
2. who set up a system to classify galaxies?
3. what are the three basic categories of galaxies?
4. what would be the difference between a \0\ elliptical galaxy and a \7\ elliptical galaxy?
5. what are the two types of spiral galaxies?
tight and loose
6. which type of spiral galaxy is our milky way galaxy?
7. describe the difference between sa, sb, and sc spiral galaxies.
sa is tight spiral, sb is between sa and sc, sc is loose?
8. how big is the milky way galaxy? ______ across ______ thick
9. what are the most plentiful galaxies in the universe?
10. elliptical galaxies contain mostly ______ stars, while spiral galaxies have a mix of ______ and ______ stars.
11. why dont elliptical galaxies make new stars?
12. can galaxies change appearances over time? how do these changes occur?
13. how can two or more spiral galaxies turn into an elliptical galaxy?
14. when galactic collisions occur, do the stars within them get affected? why or why not?
15. hubble based his classification on galaxies solely on their appearances. what types of classifications have astronomers added since hubbles time?
16. how are galaxies named?
©flying colors science

Question

galaxy types questions
name ______
1. how many stars are in a galaxy?
2. who set up a system to classify galaxies?
3. what are the three basic categories of galaxies?
4. what would be the difference between a \0\ elliptical galaxy and a \7\ elliptical galaxy?
5. what are the two types of spiral galaxies?
   tight and loose
6. which type of spiral galaxy is our milky way galaxy?
7. describe the difference between sa, sb, and sc spiral galaxies.
   sa is tight spiral, sb is between sa and sc, sc is loose?
8. how big is the milky way galaxy? ______ across ______ thick
9. what are the most plentiful galaxies in the universe?
10. elliptical galaxies contain mostly ______ stars, while spiral galaxies have a mix of ______ and ______ stars.
11. why dont elliptical galaxies make new stars?
12. can galaxies change appearances over time? how do these changes occur?
13. how can two or more spiral galaxies turn into an elliptical galaxy?
14. when galactic collisions occur, do the stars within them get affected? why or why not?
15. hubble based his classification on galaxies solely on their appearances. what types of classifications have astronomers added since hubbles time?
16. how are galaxies named?
©flying colors science

Accepted Answer

### Question 1: How many stars are in a galaxy?
# Brief Explanations:
Galaxies vary in star count. Dwarf galaxies may have $10^6 - 10^9$ stars, while large spiral/elliptical galaxies can have $10^{10}-10^{12}$ stars (e.g., Milky Way has ~100 - 400 billion stars).
# Answer:
The number of stars in a galaxy varies widely. Dwarf galaxies can have as few as a few million ($10^6$) to a few billion ($10^9$) stars, while large spiral or elliptical galaxies can contain hundreds of billions to trillions ($10^{10}-10^{12}$) of stars. For example, the Milky Way galaxy is estimated to have between 100 billion and 400 billion stars.

### Question 2: Who set up a system to classify galaxies?
# Brief Explanations:
Edwin Hubble developed the Hubble sequence (tuning - fork diagram) to classify galaxies based on their appearance (shape).
# Answer:
Edwin Hubble set up a system (the Hubble sequence, or tuning - fork diagram) to classify galaxies based on their visual appearance (shape).

### Question 3: What are the three basic categories of galaxies?
# Brief Explanations:
Hubble's classification has three main galaxy types: Elliptical (smooth, featureless, range from E0 - E7), Spiral (have a disk with spiral arms, e.g., Sa, Sb, Sc and barred spirals), and Irregular (no distinct regular shape, e.g., Irr I, Irr II).
# Answer:
The three basic categories of galaxies (from Hubble's classification) are:
1. Elliptical galaxies (denoted as "E" with a number from 0 - 7, e.g., E0, E7) - they have a smooth, featureless appearance and range from nearly spherical (E0) to very elongated (E7).
2. Spiral galaxies - they have a disk - like structure with spiral arms. There are normal spirals (denoted as Sa, Sb, Sc) and barred spirals (denoted as SBa, SBb, SBc) which have a bar - shaped structure in the center from which the spiral arms emanate.
3. Irregular galaxies - they do not have a distinct, regular shape. There are two sub - types: Irr I (have some structure but not enough to be spiral or elliptical) and Irr II (highly disturbed, often due to interactions with other galaxies).

### Question 4: What would be the difference between a "0" elliptical galaxy and a "7" elliptical galaxy?
# Brief Explanations:
Elliptical galaxy classification (E0 - E7) is based on elongation. E0 is nearly spherical (least elongated), E7 is highly elongated (most flattened/elongated).
# Answer:
The classification of elliptical galaxies (from E0 to E7) is based on their degree of elongation (or flattening). A "0" elliptical galaxy (E0) is nearly spherical in shape (it has the least amount of elongation or flattening). A "7" elliptical galaxy (E7) is the most elongated (or flattened) among elliptical galaxies, with a much more stretched - out, oval - like appearance compared to an E0 galaxy.

### Question 5: What are the two types of spiral galaxies?
# Brief Explanations:
Spiral galaxies are divided into normal spirals (Sa, Sb, Sc) and barred spirals (SBa, SBb, SBc). Barred spirals have a central bar - shaped structure from which spiral arms extend.
# Answer:
The two types of spiral galaxies are:
1. Normal spiral galaxies (denoted as Sa, Sb, Sc) - they have a spiral - arm structure that emanates from a central bulge without a distinct bar - shaped structure in the center.
2. Barred spiral galaxies (denoted as SBa, SBb, SBc) - they have a bar - shaped structure in the central region, and the spiral arms extend from the ends of this bar.

### Question 6: Which type of spiral galaxy is our Milky Way galaxy?
# Brief Explanations:
The Milky Way is a barred spiral galaxy (SBc or SBb - like), with a central bar and spiral arms (Orion, Perseus, Sagittarius, etc.) extending from the bar.
# Answer:
The Milky Way galaxy is a barred spiral galaxy (often classified as SBc or a type between SBb and SBc). It has a central bar - shaped structure in its nucleus, from which spiral arms (such as the Orion Arm, Perseus Arm, Sagittarius Arm, etc.) extend.

### Question 7: Describe the difference between Sa, Sb, and Sc spiral galaxies.
# Brief Explanations:
Sa, Sb, Sc spirals differ in bulge size, arm tightness, and interstellar matter. Sa: large bulge, tight arms, little gas/dust. Sb: medium bulge, medium arms. Sc: small bulge, loose arms, lots of gas/dust.
# Answer:
- **Sa spiral galaxies**: They have a relatively large central bulge. The spiral arms are tightly wound (close - together) around the bulge. They have relatively little interstellar gas and dust (so there is less ongoing star formation compared to other spiral types).
- **Sb spiral galaxies**: The central bulge is of medium size (smaller than that of Sa galaxies). The spiral arms are moderately wound (less tight than Sa, more tight than Sc). The amount of interstellar gas and dust, and thus the rate of star formation, is moderate.
- **Sc spiral galaxies**: They have a small central bulge. The spiral arms are loosely wound (more spread - out) around the bulge. They contain a large amount of interstellar gas and dust, leading to a relatively high rate of star formation (with many young, blue stars and star - forming regions).

### Question 8: How big is the Milky Way galaxy?
# Brief Explanations:
The Milky Way's diameter (across) is ~100,000 light - years, and its thickness (at the disk) is ~1,000 light - years (bulge is thicker, ~12,000 light - years).
# Answer:
- **Across (diameter)**: The Milky Way galaxy is approximately 100,000 light - years in diameter (this is the distance from one edge of the galactic disk to the other, passing through the center).
- **Thick (thickness of the disk)**: The thickness of the Milky Way's disk (the flat, spiral - arm - containing part) is about 1,000 light - years. The central bulge (the more spherical region at the center) is thicker, with a diameter of around 12,000 light - years.

### Question 9: What are the most plentiful galaxies in the universe?
# Brief Explanations:
Dwarf elliptical galaxies are the most numerous in the universe. They are small, dim, and elliptical - shaped, often found in galaxy clusters.
# Answer:
The most plentiful (numerous) galaxies in the universe are dwarf elliptical galaxies. These are small, relatively dim, elliptical - shaped galaxies. They are often found in large numbers within galaxy clusters and are more numerous than the larger, more well - known spiral or large elliptical galaxies.

### Question 10: Elliptical galaxies contain mostly ______ stars, while spiral galaxies have a mix of ______ and ______ stars.
# Brief Explanations:
Elliptical galaxies have mostly old (Population II, red, low - mass, evolved) stars. Spiral galaxies have a mix of old (Population II) and young (Population I, blue, high - mass, newly formed) stars.
# Answer:
Elliptical galaxies contain mostly $\boldsymbol{\text{old}}$ (and often red, low - mass, evolved) stars, while spiral galaxies have a mix of $\boldsymbol{\text{old}}$ (Population II - type) and $\boldsymbol{\text{young}}$ (Population I - type, newly formed, often blue, high - mass) stars.

### Question 11: Why don't elliptical galaxies make new stars?
# Brief Explanations:
Elliptical galaxies lack cold gas/dust (needed for star formation). They formed stars early, and mergers/processes used up or heated gas, so no new star - forming material is left.
# Answer:
Elliptical galaxies do not make new stars (or make very few new stars) because they lack significant amounts of cold interstellar gas and dust, which are the raw materials required for star formation. Most of the gas in elliptical galaxies has either been used up in the formation of stars early in the galaxy's history, or it has been heated up (due to processes like galactic mergers, interactions with other galaxies, or the activity of supermassive black holes at their centers) to the point where it is too hot to collapse and form new stars.

### Question 12: Can galaxies change appearances over time? How do these changes occur?
# Brief Explanations:
Yes, galaxies change. Interactions (collisions/mergers) distort shapes, trigger star formation, or turn spirals into ellipticals. Internal processes (black holes, stellar evolution) also affect appearance.
# Answer:
- **Can they change?** Yes, galaxies can change their appearances over time.
- **How?**
    - **Galactic interactions (collisions/mergers)**: When two or more galaxies collide or merge, their gravitational interactions can distort their shapes. For example, a spiral galaxy can lose its distinct spiral structure and become more irregular - shaped during a collision. Mergers can also trigger intense bursts of star formation (due to the compression of gas and dust) or, in the case of multiple mergers, can eventually turn a spiral - type galaxy into an elliptical - type galaxy.
    - **Internal processes**: The evolution of stars within a galaxy (e.g., the death of massive stars in supernovae, the aging of stars) and the activity of supermassive black holes at the centers of galaxies can also change a galaxy's appearance. For example, the energy released by a supermassive black hole can heat up gas in the galaxy, affecting star formation rates and the overall structure.

### Question 13: How can two or more spiral galaxies turn into an elliptical galaxy?
# Brief Explanations:
When spiral galaxies collide/merge, gravitational forces disrupt their disks, mix stars/gas, and the resulting galaxy loses spiral structure, becomes elliptical (due to random motion of stars and dissipation of gas).
# Answer:
When two or more spiral galaxies collide or merge:
1. The gravitational forces from the interaction disrupt the orderly, disk - like structure (with spiral arms) of the spiral galaxies.
2. The stars, gas, and dust from the different spiral galaxies get mixed together.
3. Over time, the combined system loses its distinct spiral - arm structure. The stars end up moving in more random, elliptical - like orbits (rather than the more ordered, circular orbits in the disk of a spiral galaxy).
4. Any remaining gas is either used up in a burst of star formation or is heated and dispersed, and the resulting galaxy takes on the smooth, featureless appearance of an elliptical galaxy.

### Question 14: When galactic collisions occur, do the stars within them get affected? Why or why not?
# Brief Explanations:
Stars are rarely directly hit (galaxies are mostly empty space). But their orbits change due to gravitational interactions, and star formation can be triggered (from gas compression).
# Answer:
- **Do stars get affected?** Stars within colliding galaxies are generally not directly "hit" (destroyed) by other stars, but they are affected in other ways.
- **Why?** Galaxies are mostly empty space (the average distance between stars in a galaxy is very large, on the order of light - years). So the probability of two stars colliding during a galactic collision is extremely low. However, the gravitational forces from the interaction between the two (or more) galaxies can change the orbits of the stars. Also, the collision can compress the interstellar gas and dust in the galaxies, triggering new star formation (which affects the stellar population of the galaxies over time).

### Question 15: Hubble based his classification on galaxies solely on their appearances. What types of classifications have astronomers added since Hubble's time?
# Brief Explanations:
Astronomers now classify galaxies by: 1) Physical properties (mass, star formation rate, gas content), 2) Evolutionary stage (how galaxies form/evolve), 3) Interaction history (mergers, collisions), 4) Spectral classification (using light spectra to study composition, temperature, etc.).
# Answer:
Since Hubble's time (when he classified galaxies based only on their visual appearance), astronomers have added several other types of classifications:
1. **Classification based on physical properties**: This includes classifying galaxies by their mass (dwarf, giant), the rate of star formation (star - forming, quiescent), the amount of interstellar gas and dust they contain, and the presence of active galactic nuclei (e.g., galaxies with supermassive black holes that are accreting matter and emitting large amounts of energy).
2. **Evolutionary classification**: Astronomers now try to classify galaxies based on their evolutionary stage, such as how they formed (e.g., through the merging of smaller galaxies) and how they are likely to evolve in the future (e.g., whether a spiral galaxy is likely to merge with another galaxy and become an elliptical galaxy).
3. **Classification based on interaction history**: Galaxies are classified based on their past and present interactions with other galaxies (e.g., galaxies that are in the process of colliding, galaxies that have recently merged, galaxies that are gravitationally interacting with nearby galaxies).
4. **Spectral classification**: By analyzing the spectra of galaxies, astronomers can classify them based on the types of stars they contain (e.g., the proportion of young vs. old stars), the chemical composition of the interstellar medium, and the temperature and motion of the gas within the galaxy.

### Question 16: How are galaxies named?
# Brief Explanations:
Galaxies are named in several ways: 1) Catalog names (e.g., Messier (M), NGC, IC, UGC) from observational catalogs. 2) Descriptive names (e.g., "Milky Way" for our galaxy, "Andromeda Galaxy" for M31). 3) Names based on location (e.g., "Virgo Cluster Galaxies" for galaxies in the Virgo cluster).
# Answer:
Galaxies are named in several ways:
1. **Catalog names**: Most galaxies are named after the catalogs in which they were first recorded. For example:
    - **Messier Catalog (M)**: Galaxies (and other celestial objects) discovered by Charles Messier are named with "M" followed by a number (e.g., M31 is the Andromeda Galaxy).
    - **New General Catalog (NGC)**: A large catalog of nebulae and star clusters (including galaxies) with entries named "NGC" followed by a number (e.g., NGC 4…

Sovi.AI - AI Math Tutor

QUESTION IMAGE

Question

Explanation:

Question 1: How many stars are in a galaxy?

Answer:

Question 2: Who set up a system to classify galaxies?