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Almost all observations of the universe

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come by collecting
light in various wavelengths.

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This light can show variations
in brightness,

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reveal structure in cosmic objects,
and contain huge amounts of information

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in how its wavelengths are distributed
across a spectrum.

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Space isn't static, and recording data
through a given duration called 

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Time-Domain Astronomy tracks
how details of an object change.

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An object can vary,

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it can move, or it can do both.

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There are three main classes
of how an object can vary in time.

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Periodic, quasiperiodic, and transient. Periodic change

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means there is a regular fixed pattern
to the change.

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Sunrise and sunset
or a blinking pulsar are examples.

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Quasiperiodic means
that there is a pattern and the change

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or event happens again and again,
but not as regularly,

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like hurricanes or flashes
from hot material around black holes.

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Transient events are less predictable
and often happen only once.

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Earthquakes and supernovas are transients.

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These are the hardest to observe because
they can be brief and start unexpectedly.

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If telescopes aren't looking in the
right place, they miss the beginning or

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even the entire event.