Questions and Answers
What is the interstellar medium?
What elements make up our galaxy?
70% H, 28% He, 2% heavier elements
How do we determine the composition of interstellar gas?
From its absorption lines in the spectra of stars
Where do stars form?
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What happens during interstellar reddening?
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Is it possible to observe newborn stars?
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Why do stars form?
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How do clouds resist gravity long enough to grow?
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What is resistance to gravity in star formation?
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What is fragmentation of a cloud?
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What does fragmentation of a cloud create?
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What is a protostar?
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What is a main sequence star?
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Where do stars typically form?
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Why do stars form in certain clouds?
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Trapping of thermal energy means that ______ will happen.
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What happens as a cloud shrinks?
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What causes a cloud to flatten into a disk?
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Study Notes
Interstellar Medium
- The interstellar medium is the gas and dust occupying space between stars, indicating that space is not entirely empty.
Composition of the Galaxy
- Our galaxy mainly consists of 70% hydrogen, 28% helium, and 2% heavier elements.
Determining Interstellar Gas Composition
- The composition of interstellar gas is analyzed through absorption lines observed in stellar spectra.
Formation of Stars
- Stars originate in cold and dense interstellar clouds, known as molecular clouds, where conditions are suitable for star formation.
Interstellar Reddening
- Long-wavelength infrared light can penetrate clouds more easily than visible light, helping observe stars hidden behind dust.
Observing Newborn Stars
- Newborn stars are often concealed within dark, dusty clouds. Infrared observations can reveal these stars despite the obscuring material.
Gravity vs. Pressure in Star Formation
- Star formation occurs when gravity overcomes the thermal pressure within a cloud, aided by emission lines from molecules converting thermal energy into radiation.
Cloud Resistance to Gravity
- Clouds resist gravitational collapse by converting thermal energy into escaping infrared and radio photons, delaying pressure buildup.
Increased Mass Requirement for Contraction
- A cloud must possess additional mass to begin contraction if facing extra forces that oppose gravity.
Cloud Fragmentation
- Turbulence within clouds leads to dense clumps, making it possible for gravity to dominate in smaller areas, causing the cloud to fragment and potentially form multiple stars.
Outcomes of Cloud Fragmentation
- Individual dense clumps from fragmentation can develop into stars, with larger clouds potentially forming star clusters.
Protostar
- A protostar is an early stage in star formation, occurring between the collapse of gas and dust and the onset of nuclear fusion.
Main Sequence Star
- A main sequence star, like our sun, undergoes hydrogen fusion into helium and represents the majority of stars on the Hertzsprung-Russell diagram.
Conditions for Star Formation
- Stars are born in molecular gas clouds at temperatures of 10-30 K, primarily comprised of molecular hydrogen and moderated in temperature by carbon monoxide emissions.
Reasons for Star Formation
- Stars form in sufficiently massive clouds where gravity can counteract other forces, causing contractions and subsequent fragmentation into star-forming regions.
Thermal Energy Trapping
- As a cloud fragments and contracts, thermal energy builds up internally, increasing pressure and stalling contraction, eventually forming a protostar.
Initial Stage of Star Formation
- The protostar represents the first stage in the process of star formation.
Protostar Growth Process
- Matter continues to accumulate on the protostar until external forces, such as a nearby star, disrupt the surrounding gas.
Role of Rotation in Star Birth
- Gas clouds typically exhibit a small net rotation as a result of the random motions of gas particles during their contraction.
Effects of Shrinking Cloud on Rotation
- As a gas cloud shrinks, it spins faster, similar to how an ice skater increases speed by pulling in their arms.
Flattening of the Cloud
- Collisions among particles in the collapsing cloud cause it to flatten into a disk shape, facilitating star formation.
Formation of Jets
- The process of jet formation occurs in the later stages of star births but is not detailed in the provided information.
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Description
Explore the fascinating concepts of the interstellar medium and the elemental composition of our galaxy. This quiz offers flashcards to help you learn about the gas and dust that fills space and the primary elements that make up the Milky Way. Test your knowledge and deepen your understanding of these astronomical phenomena.
