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atomiclaser
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- definition of foreground and background in astrophysical observation
During the astrophsyical observation, what is the definition of foreground and background in astrophysical observation?
thanks for your explanation.jedishrfu said:I don't think there's a hard and fast definition. Foreground objects are in front of the object you are looking at and affect your viewing of the object.
An example, would be taking a photo of the Andromeda galaxy. The photo will be littered with foreground stars from our own galaxy and taking any measurements from the observation would require knowing what stars are what and how far away they are so that foreground stars can be eliminated. Parallax is often used to eliminate these stars as they will move depending on where we take our photo ie spring time vs fall time when we are at opposite ends of the Earth orbit.
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Early universe objects are affected by lensing, dust clouds absorbing light, expansion ... and many other effects that must be accounted for to get your measurements.
Background objects
The Openstax online Astronomy may answer more of your questions.
https://openstax.org/details/books/astronomy
Foreground refers to objects or phenomena that are closer to the observer, while background refers to objects or phenomena that are further away. In astrophysical observation, foreground objects may include stars, planets, or galaxies within our own Milky Way galaxy, while background objects may include distant galaxies or clusters of galaxies.
Foreground objects can block or distort the view of background objects, making it difficult to observe them accurately. However, foreground objects can also act as gravitational lenses, bending and magnifying the light from background objects, providing valuable information about the mass and distribution of matter in the universe.
Yes, astrophysicists use various techniques, such as spectroscopy and photometry, to distinguish between foreground and background objects. Spectroscopy allows scientists to analyze the light emitted or absorbed by an object, providing information about its composition and distance. Photometry measures the brightness of an object at different wavelengths, helping to determine its distance and distinguish it from foreground or background objects.
Astrophysicists use various methods to account for foreground objects, such as subtracting their contribution to the observed signal or creating models to correct for their effects. They may also use statistical techniques to identify and remove foreground objects from the data set.
Foreground objects in astrophysical observations may include stars, planets, gas clouds, or dust within our own galaxy. Background objects may include distant galaxies, quasars, or cosmic microwave background radiation. For example, the cosmic microwave background radiation is a remnant of the Big Bang and is considered to be a background object in astrophysical observations.