7.2 Interstellar dust and extinction
2 min read•july 25, 2024
plays a crucial role in shaping our universe. These tiny particles absorb and scatter starlight, catalyze chemical reactions, and provide building blocks for planetary systems. They're found throughout galaxies, influencing their dynamics and evolution.
Dust grains are made of silicates, carbonaceous materials, and ices. Their size and composition affect how they interact with light, causing and of starlight. Scientists study dust through various methods, including extinction curves and infrared observations.
Interstellar Dust Properties and Composition
Role of interstellar dust
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Top images from around the web for Role of interstellar dust
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- Microscopic solid particles in space between stars composed of silicates, carbonaceous materials, and ices
- Absorbs and scatters starlight altering observed brightness and color of celestial objects
- Catalyzes chemical reactions in space facilitating formation of complex molecules (water, methanol)
- Provides formation sites for molecules acting as building blocks for planetary systems
- Contributes to overall mass of galaxy affecting galactic dynamics and evolution
- Concentrated in and star-forming regions shapes structure of interstellar medium
- Present throughout galactic disk influences large-scale galactic properties
Composition of dust grains
- Silicates form core of many dust grains (olivine, pyroxene)
- Carbonaceous materials contribute to grain structure (graphite, amorphous carbon)
- Ices coat grains in cold regions preserving volatile compounds (water, carbon dioxide, methane)
- Metals and metal oxides add to grain diversity (iron, magnesium oxides)
- ranges from nanometers to micrometers following power-law distribution
- Majority of grains smaller than visible light wavelengths affects interaction with electromagnetic radiation
- Irregular and non-spherical shapes influence properties and polarization of light
Interstellar Extinction and Observation Techniques
Concept of interstellar extinction
- Attenuation of starlight by dust reduces apparent brightness of stars
- Wavelength-dependent process causes color changes (reddening) of starlight
- Alters spectral features complicating spectroscopic analysis
- Extinction law describes wavelength dependence often parameterized by
- Impacts distance measurements leading to underestimation if not accounted for
- Requires correction for accurate cosmic distance ladder calculations
Methods for studying dust
- Extinction curves plot extinction vs wavelength revealing dust grain properties
- Prominent 2175 Å bump indicates presence of carbonaceous materials
- Color excess measurements indicate dust column density
- Comparison of observed vs intrinsic stellar colors determines reddening
- Linear polarization measurements of starlight by aligned dust grains reveal magnetic field structure
- Infrared observations detect thermal emission from dust grains
- Spectral features in IR indicate dust composition (silicate features at 10 and 18 μm)
- Scattering observations of reflection nebulae and diffuse galactic light provide insights into dust distribution
Key Terms to Review (17)
Albedo: Albedo is the measure of reflectivity of a surface, defined as the ratio of reflected radiation from the surface to the incident radiation upon it. This concept is crucial in understanding how various celestial bodies interact with light, influencing their temperature, climate, and visibility. A higher albedo means more light is reflected, while a lower albedo indicates more absorption of light, which can affect phenomena such as extinction in interstellar dust or the characteristics and classification of exoplanets.
D. J. Thaddeus: D. J. Thaddeus was a significant figure in the study of interstellar dust, particularly known for his research on the properties and behavior of cosmic dust grains. His work has contributed to the understanding of how interstellar dust affects the extinction of light from distant stars and galaxies, which is crucial for interpreting astronomical observations and understanding the structure of the universe.
Extinction: Extinction refers to the reduction of light from celestial objects due to interstellar dust absorbing and scattering the light as it travels through space. This phenomenon plays a crucial role in our understanding of the universe, as it can affect the observed brightness and color of stars, leading to miscalculations of their distances and intrinsic properties.
Galactic ecology: Galactic ecology is the study of the interactions and relationships between various components of galaxies, including stars, interstellar gas, dust, and dark matter. This concept emphasizes the complex web of life cycles, formation, and destruction that governs how materials are exchanged and transformed within a galaxy, influencing its overall structure and evolution.
Grain Growth: Grain growth refers to the process by which small dust grains in space collide and coalesce over time, leading to the formation of larger grains. This phenomenon plays a critical role in the evolution of interstellar dust, affecting how light interacts with these particles and ultimately influencing extinction phenomena as light passes through cosmic dust clouds.
Infrared extinction: Infrared extinction refers to the absorption and scattering of infrared radiation by interstellar dust particles, which diminishes the intensity of this radiation as it travels through space. This phenomenon significantly impacts the observations of celestial objects and influences our understanding of their properties, especially in regions with dense dust clouds.
Interstellar dust: Interstellar dust refers to tiny solid particles found in the space between stars in a galaxy. This dust is composed of various elements and compounds, including carbon, silicates, and ices, playing a crucial role in the formation of stars and planets, as well as influencing the light from distant objects by causing extinction.
Molecular clouds: Molecular clouds are dense regions of gas and dust in the interstellar medium where molecules, primarily hydrogen, can form and exist. These clouds are essential for star formation as they provide the necessary material and conditions for stars and planetary systems to develop. Molecular clouds also play a critical role in the overall composition and structure of the interstellar medium, impacting processes such as extinction and the lifecycle of stellar formations.
Nucleation: Nucleation is the process through which new phases or structures begin to form, typically as small clusters or particles, in a given medium. This process is crucial in the formation of interstellar dust grains and affects how light interacts with matter, leading to extinction effects observed in astronomical observations. Nucleation can happen in various environments, influencing the chemical composition and physical properties of celestial bodies and interstellar space.
Optical extinction: Optical extinction refers to the reduction in the intensity of light as it passes through interstellar dust and gas. This phenomenon plays a crucial role in astrophysics, as it affects our ability to observe celestial objects and influences the brightness and color of light emitted from stars and galaxies.
Photometry: Photometry is the science of measuring the intensity of light, particularly in terms of its brightness as perceived by the human eye. This measurement is crucial in astrophysics for understanding celestial objects and phenomena, as it connects various aspects like light emissions from stars, the effects of interstellar dust on light transmission, and the distribution of light in galaxy clusters.
Reddening: Reddening refers to the phenomenon where light from distant stars appears to be shifted towards longer wavelengths, primarily due to the scattering and absorption of shorter wavelengths by interstellar dust. This effect causes stars that are viewed through dust clouds to appear redder than they truly are, impacting our understanding of their true colors and distances.
Robert E. Williams: Robert E. Williams is an influential astronomer known for his work in the field of interstellar dust and extinction. His research has significantly contributed to understanding how interstellar dust affects the light from distant stars and galaxies, impacting our observations of the universe. This understanding is crucial for accurately interpreting astronomical data and determining the composition and distance of celestial objects.
Scattering: Scattering is the process by which particles or photons change direction as a result of interactions with other particles or fields, altering the distribution of light. This phenomenon plays a crucial role in understanding how light interacts with matter, influencing various radiative processes and affecting the observation of astronomical objects through intervening materials like interstellar dust.
Size Distribution: Size distribution refers to the statistical representation of various sizes of particles within a specific population, particularly in the context of interstellar dust. Understanding size distribution is crucial for determining how these particles affect light absorption and scattering, which ultimately impacts the visibility of astronomical objects through interstellar mediums.
Spectroscopy: Spectroscopy is the study of the interaction between electromagnetic radiation and matter, specifically how light is absorbed, emitted, or scattered by substances. This technique allows scientists to analyze the composition, temperature, density, and motion of celestial objects by examining their spectra, connecting it deeply to understanding astronomical phenomena.
Star Formation: Star formation is the process by which dense regions within molecular clouds in the interstellar medium collapse under their own gravity to form stars. This process involves several stages, including the accumulation of gas and dust, the formation of protostars, and eventually, the ignition of nuclear fusion in the core, leading to a main-sequence star. Understanding star formation connects to the composition of the interstellar medium, how interstellar dust affects observations, and the advantages offered by space-based observatories in studying these distant phenomena.