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Beyond Our Galaxy

M82 Galaxy: "Average" CO Intensity

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Earth's location within the Milky Way restricts the perspective we can have of our home galaxy. Peering at faraway galaxies provides a more global understanding of galactic structure, dynamics and evolution.

Among the many different types of galaxies are starburst galaxies. Observing them can aid our understanding of star formation in galaxies and the processes leading to the formation of galaxies themselves. One starburst galaxy, M82, has been extensively studied with the BIMA array. Located about 5 million light years away from Earth, M82 belongs to a triple galaxy system which also includes the spiral galaxy, M81 and a third galaxy, NGC 3077.

Understanding "Global" Star Formation

Comprehensive studies of M82 and its interactions with M81 require observations in several portions of the spectrum.

M82: Optical View

The optical image reveals the presence of dark patches in M81, indicating the presence of dust.

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M82: View in Red Light

These patches appear more prominently in red light, as illustrated in this image.

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Millimeter observations map the emissions from molecules present chiefly in the dense regions of intestellar space inside the galaxy, where stars are forming. Employing the array's spectrometer, astronomers are able to infer wh ere the molecules are distributed how fast they are moving away from us.

Such data may also contain important information about the forces shaping M82 and influencing star formation within the galaxy. Among these forces are the gravitational effects exerted by its neighbor, M81, which may compress the gas in M82. As the densit y of this gas increases, it may collapse due to gravity, thus triggering star formation. Embedded in regions full of dust, young stars emit radiation which is absorbed by the dust and re-emitted as infrared radiation.

M82: Infrared View
In this infrared image, the bright areas indicate warmer regions where starbirth is taking place. Ultraviolet light emitted by young, hot, massive stars dissociates the molecular hydrogen gas into hydrogen atoms, which in turn radiate energy in the centim eter portion of the spectrum.

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Triple Galaxy System: Hydrogen Gas Imaging

Observations of centimeter radiowave emissions show that neutral hydrogen gas flows between M81, M82 and NGC 3077. Astronomers can trace the motion of this atomic gas as it travels into the inner regions of the galaxies.

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Copyright 1995: Board of Trustees, University of Illinois


NCSA. Last modified 11/16/95.