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Dust clouds along the line of sight scatter and absorb light coming from distant objects. We therefore see these objects as dimmer and redder than they really are.

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Extinction event
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Definition: : The failure of a taxonomic group to produce direct descendants, causing its worldwide disappearance from the record at a given point in time.
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Extinction, Scattering, and Absorption
Astronomers who specialize in photometry need to compensate for atmospheric extinction: the reduction in a celestial object's apparent brightness when its light passes through the atmosphere.

As for the other events, while an asteroid impact almost certainly caused the demise of the dinosaurs, environmental factors such as climate variation, sea level change or intense geologic activity could have been the trigger instead.

Late Triassic The Late Triassic extinction occurred about 200 million years ago, and it killed about 50 percent of all marine species. It was belived to be caused by volcanism and global warming.

However, in the case of the Cretaceous-Tertiary (KT) that killed the dinosaurs 65 million years ago, there is ample evidence of both an asteroid strike and catastrophic volcanic upheaval (the Deccan Traps).

Starlight passing through a dust cloud can be affected in a couple of ways.

, atmospheric. The diminishing of light from astronomical objects due to the earth's atmosphere, in which molecules (air, dust, etc.) of the atmosphere absorb, reflect, and refract light before it reaches the ground.

Extinction- the apparent reduction in the brightness of a star or planet when low over the horizon because more of its light is absorbed by the Earth's atmosphere ...

Loss of light from an object as a consequence of absorption or scattering by an intervening medium. An example is the atmospheric of light from stars near the horizon.

The dimming effect of the interstellar medium on starlight passing through it.
An optical instrument constructed of lenses which magnifies and focuses the incoming light gathered from a telescope.

The dimming of light by intervening material; commonly, dimming by the interstellar medium.
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Extinction and survival
Crocodilians, pterosaurs, dinosaurs, and champsosaurs survived the Triassic-Jurassic extinction event
Triassic-Jurassic extinction event ...

- In astronomy, the dimming of starlight as it passes through the interstellar medium. Dust scatters some of the light, causing the total intensity of the light to diminish.

Extinction. The apparent reduction in brightness of a celestial object when it is low in the sky and much of its light is absorbed by Earth's atmosphere.

- The dimming of starlight due to absorption and scattering by interstellar dust particles.

(a) Attenuation of starlight due to absorption and scattering by Earth's atmosphere, or by interstellar dust. The longer the path through the dust, and the denser the dust, the more the starlight is reddened.

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extinction The dimming of starlight as it passes through the interstellar medium.
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is inversely proportional to wavelength so red light is less affected than blue light. Distant stars thus appear more red than they actually are.

The apparent dimming of star or planet when low on the horizon due to absorption by the Earth's atmosphere.
A term that means outside of or beyond our own galaxy.

The of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds.

Mass extinction is the process in which huge numbers of species die out suddenly. The dinosaurs (and many other species) went extinct during the K-T extinction, which was probably caused by an asteroid colliding with the Earth.

ELE = Level Event as far as i know
@Gray (No.12): Yes, that's pretty much it. The light from Betelgeuse takes 600 years to reach us, so any event we can see from Earth happened 600 years ago.

3. Extinction is the _____ of starlight by interstellar _____. (Hint)
4. The density of interstellar matter can be characterized as being very _____. (Hint)
5. Interstellar gas is composed of 90 percent _____ and 9 percent _____. (Hint) ...

Atmospheric is the term used for defining the absorption of starlight light by the earth's atmosphere. At an altitude of 52 degrees and higher, atmospheric has a factor of zero.

interstellar extinction - (n.)
The obscuration of starlight by interstellar dust. Light is scattered off of dust grains, so that a distant star appears dimmer than it otherwise would.

Interstellar : As light from a star travels through interstellar space it encounters some amount of dust. This dust scatters some of the light, causing the total intensity of the light to diminish.

interstellar extinction
The dimming of starlight as it passes through the interstellar medium.
interstellar medium
Gas and dust in interstellar space.

(Galileo Project Glossary - JPL) The failure of a taxonomic group to produce direct descendants, causing its worldwide disappearance from the record at a given point in time.

extinction The attenuation of light; that is, the reduction of illuminance of a collimated beam of light as the light passes through a medium wherein absorption and scattering occur.

extent could be measured, as distinguished from a point source. Now, one which has a large angular extent and is strongest at longer wavelengths (distinguished from a compact source). Most extended sources tend to be polarized. [H76]

Because of dust extinction, one always wants to use lines at the longest possible wavelength. As Susan Kleinmann once said, "I don't care if it's plastic, as long as it's in the infrared and you can see it".

expanding cosmological model exploding galaxy Galaxy in which powerful explosions are occurring in its central region and which is emitting nonthermal radiation. extragalactic ...

This theory is that a large asteroid, meteor, or comet hit the Earth 65 million years ago, causing huge atmospheric and geologic disruptions, leading to a mass extinction which killed the dinosaurs and many other species.

The last such eruption occurred some 65 million years ago (press release, Basu et al, 1993), created India's Deccan Traps, and -- in combination with the Chicxulub meteorite impact -- contributed to the of the dinosaurs.

This is an extreme example of interstellar extinction which is the dimming of star light caused by the presence of interstellar material. In the dust lanes the extinction is complete. But in other regions it is only partial.

In 1980, physicist Luis Alvarez and coworkers reported finding a very high concentration of the element iridium in the sedimentary clay layer laid down at the time of the K-T .

See also: See also: Earth, Astro, Planet, Sun, Solar

Astronomy  Explorer XI  Extragalactic

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