| 31. | This planetary nebula has a nearly uniform spherical shell.
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| 32. | This object was the first planetary nebula to be discovered; by Charles Messier in 1764.
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| 33. | There is one prominent planetary nebula in Andromeda : NGC 7662 ( Caldwell 22 ).
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| 34. | There is one bright planetary nebula in Centaurus, NGC 3918, also known as the Blue Planetary.
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| 35. | It covers 0.25 square degrees, making it also the largest planetary nebula as seen from Earth.
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| 36. | Another planetary nebula in Lyra is Abell 46.
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| 37. | :That " butterfly " is a planetary nebula.
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| 38. | It is possible to determine distances to the nearest planetary nebula by measuring their expansion rates.
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| 39. | The Boomerang Nebula is believed to be a star system evolving toward the planetary nebula phase.
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| 40. | However, when the spectrum was examined again in August 1892, it appeared to be a planetary nebula.
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