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Select the correct answer from the list.(1 point) To form a nebula, Select Answer pulls matter together or causes Select Answer .

To form a nebula, gravity pulls matter together or causes gravitational collapse.

Which of these characteristics of a star make it most likely to become a black hole? Select the two correct answers.(1 point) Responses Its mass is equal to that of the sun. Its mass is equal to that of the sun. It has an abundant supply of hydrogen. It has an abundant supply of hydrogen. It is dying. It is dying. Its mass is greater than 20 times the mass of the sun.

The correct answers are:

- Its mass is greater than 20 times the mass of the sun.
- It is dying.

Which description best summarizes the steps that take place during black hole formation, in the correct order?(1 point) Responses Supernova explodes a massive star; remaining core expands; nuclear reactions diminish the effects of gravity. Supernova explodes a massive star; remaining core expands; nuclear reactions diminish the effects of gravity. Supernova triggers fusion reactions; massive star implodes due to extreme radiation; volume and mass of star increase rapidly. Supernova triggers fusion reactions; massive star implodes due to extreme radiation; volume and mass of star increase rapidly. A small star gains mass through fusion reactions; core of star collapses; increased radiation triggers a supernova. A small star gains mass through fusion reactions; core of star collapses; increased radiation triggers a supernova. A massive star depletes its nuclear fuel; gravity overpowers the star; supernova occurs; core of star collapses.

The correct answer is: A massive star depletes its nuclear fuel; gravity overpowers the star; supernova occurs; core of the star collapses.

How do emission and reflection nebulae differ?(1 point) Responses contain remnants of stars contain remnants of stars interactions with light interactions with light hard line edges hard line edges the presence of young stars

Emission and reflection nebulae differ in the following way:

- Emission nebulae contain remnants of stars and are formed by interactions with light emitted by hot, ionized gas.
- Reflection nebulae are formed by the interactions of starlight with dust particles and do not contain remnants of stars.
- Emission nebulae often have a red glow due to the presence of ionized hydrogen gas, while reflection nebulae have a bluish appearance as they reflect the light of nearby stars.
- Emission nebulae usually have a diffuse and irregular shape, while reflection nebulae often have well-defined edges.
- Both types of nebulae can contain young stars, but the presence of young stars is more commonly associated with emission nebulae.

Select the correct answer from the list.(1 point) Astronomers think that most galaxies are centered by a Select Answer , which exerts Select Answer that binds the galaxy together.

Astronomers think that most galaxies are centered by a supermassive black hole, which exerts gravitational force that binds the galaxy together.

What is the main challenge astronomers face when trying to directly detect black holes?(1 point) Responses Black holes are too black. Black holes are too black. Black holes trap all light. Black holes trap all light. Black holes are too small. Black holes are too small. Black holes are empty.

The main challenge astronomers face when trying to directly detect black holes is that black holes trap all light.

Where could scientists look to observe a black hole?(1 point) Responses the solar system asteroid belt the solar system asteroid belt the center of the sun the center of the sun the edge of the solar system the edge of the solar system the center of the Milky Way the center of the Milky Way

Scientists could look to the center of the Milky Way to observe a black hole.

Which statement best describes the galaxies closest to the Milky Way?(1 point) Responses These galaxies are independent of and unaffected by the Milky Way's gravitational pull. These galaxies are independent of and unaffected by the Milky Way's gravitational pull. These galaxies include irregular, spiral, and elliptical types. These galaxies include irregular, spiral, and elliptical types. These galaxies consist of mostly old stars. These galaxies consist of mostly old stars. These galaxies are all identified as spiral.

The statement "These galaxies include irregular, spiral, and elliptical types" best describes the galaxies closest to the Milky Way.