Right Ascension	03 : 46.3 (h:m)
Declination	+23 : 56 (deg:m)
Distance	0.44 (kly)
Visual Brightness	13 (mag)
Diameter	0.5 (arc min)

Discovered by E.E. Barnard in 1890.

In 1890, American astronomer E. E. Barnard, observing visually with the Lick Observatory 36-inch telescope in California, discovered an exceptionally bright nebulosity adjacent to the bright Pleiades star Merope. It is now cataloged as IC 349, or "Barnard's Merope Nebula." IC 349 is so bright because it lies extremely close to Merope -- only about 3,500 times the separation of the Earth from the Sun, or about 0.06 light-year -- and thus is strongly illuminated by the star's light.

NASA's Hubble Space Telescope has caught the eerie, wispy tendrils of this dark interstellar cloud being destroyed by the passage of one of the brightest stars in the Pleiades star cluster. Like a flashlight beam shining off the wall of a cave, the star is reflecting light off the surface of pitch black clouds of cold gas laced with dust - these are called reflection nebulae.

In the new Hubble image, Merope itself is just outside the frame on the upper right. The colorful rays of light at the upper right, pointing back to the star, are an optical phenomenon produced within the telescope, and are not real. However, the remarkable parallel wisps extending from lower left to upper right are real features, revealed for the first time through Hubble's high-resolution imaging capability. Astronomers George Herbig and Theodore Simon of the University of Hawaii obtained these broadband observations with Hubble's Wide Field and Planetary Camera 2 on September 19, 1999.

Herbig and Simon propose that, as the Merope Nebula approaches Merope, the strong starlight shining on the dust decelerates the dust particles. Physicists call this phenomenon "radiation pressure."

Smaller dust particles are slowed down more by the radiation pressure than the larger particles. Thus, as the cloud approaches the star, there is a sifting of particles by size, much like grain thrown in the air to separate wheat from chaff. The nearly straight lines pointing toward Merope are thus streams of larger particles, continuing on toward the star while the smaller decelerated particles are left behind at the lower left of the picture.

Over the next few thousand years, the nebula--if it survives the close passage without being completely destroyed--will move on past Merope, somewhat like a comet swinging past our Sun. This chance collision allows astronomers to study interstellar material under very rare conditions, and thus learn more about the structure of the dust lying between the stars.

Image Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: George Herbig and Theodore Simon (Institute for Astronomy, University of Hawaii)

Pleiades Bright Stars and Nebulae

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Hartmut Frommert
Christine Kronberg
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Last Modification: August 31, 2001