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On July 4, 1054, a supernova (SN 1054) was observed by astronomers and stargazers across the Northern Hemisphere, and possibly Australia. Its remnant, the Crab Nebula, is among the most-studied objects outside our solar system.
 
A supernova is one of the most explosive events in the universe. A supernova occurs when a massive star runs out of nuclear fuel (mostly hydrogen and helium). The core of the star collapses, violently ejecting its outer envelope of material into space in a huge shock wave. These blast materials are the filaments still visible as the Crab Nebula. 
 
The star that went supernova in 1054 was so massive that it left only a rapidly rotating ball of neutrons called a pulsar. The Crab Pulsar is only about 20 kilometers (12 miles) in diameter, but has a mass greater than the Sun! The Crab Pulsar pulses, or spins, about 30 times a second.
 
SN 1054 was visible as a bright, glowing star for about two years! Astronomers in China, Japan, and what is today Iraq recorded the event. Some historians think that petroglyphs left by Ancestral Puebloans may also have recorded SN 1054. Other historians think the oral tradition of Aboriginal Australians may also refer to SN 1054.
Aboriginal Australian
Noun

people and culture native to Australia and its surrounding islands. Also called Aborigine.

Ancestral Puebloans
Plural Noun

(1200 BCE-1300 CE) people and culture native to what is now the southwestern United States. Also called Anasazi.

astronomer
Noun

person who studies space and the universe beyond Earth's atmosphere.

collapse
Verb

to fall apart completely.

Noun

the extremely hot center of Earth, another planet, or a star.

diameter
Noun

width of a circle.

eject
Verb

to get rid of or throw out.

envelope
Noun

material found in a roughly spherical shape around a star.

filament
Noun

very thin fiber or thread-like structure.

mass
Noun

measure of the amount of matter in a physical object.

massive
Adjective

very large or heavy.

nebula
Noun

cloud of gas and dust in space.

neutron
Noun

particle in an atom having no electrical charge.

Northern Hemisphere
Noun

half of the Earth between the North Pole and the Equator.

observe
Verb

to watch.

oral tradition
Noun

history, characteristics, and mythology of a culture transmitted through vocal, not written, methods.

petroglyph
Noun

carving or drawing on rock.

pulsar
Noun

rapidly spinning neutron star that emits beams (pulses) of radiation.

rapidly
Adverb

fast.

record
Verb

to preserve observations with notes, drawings, photographs, audio or video recordings.

refer
Verb

to direct attention to something.

remnant
Noun

something that is left over.

shock wave
Noun

moving, measurable change in pressure and density of a material.

solar system
Noun

the sun and the planets, asteroids, comets, and other bodies that orbit around it.

star
Noun

large ball of gas and plasma that radiates energy through nuclear fusion, such as the sun.

supernova
Noun

sudden, violent explosion of a massive star.

telescope
Noun

scientific instrument that uses mirrors to view distant objects.

universe
Noun

all known matter, energy, and space.

violent
Noun

strong, destructive force.

visible
Adjective

able to be seen.

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