NGC 6826

NGC 6826, also known as the Blinking Planetary Nebula, is a planetary nebula located in the constellation Cygnus. It was discovered by William Herschel on September 6, 1793.

The "blinking" effect, from which it derives its popular name, is due to the difference in brightness perception between the bright central star and the fainter, extended halo surrounding it. When viewed directly, the bright central star tends to dominate, making the fainter halo harder to see. However, when viewed with averted vision (looking slightly to the side), the eye becomes more sensitive to the dimmer light of the halo, and it appears to "blink" into view.

NGC 6826 is approximately 2,200 light-years from Earth. The nebula itself is formed from the ejected outer layers of a dying star that has evolved into a red giant. The central star, a white dwarf, is extremely hot and emits ultraviolet radiation, which ionizes the surrounding gas, causing it to glow.

The nebula exhibits a complex structure, including a bright inner shell and fainter outer halos. These structures are likely the result of different phases of mass loss from the central star. The outer halos may represent material ejected during earlier stages of the star's evolution.

Spectroscopic observations of NGC 6826 have revealed the presence of various elements, including hydrogen, oxygen, nitrogen, and helium. The abundance ratios of these elements provide clues about the star's original composition and the processes that occurred during its life cycle.

NGC 6826 is a popular target for amateur astronomers due to its relatively bright magnitude and interesting "blinking" effect. It can be observed with moderate-sized telescopes under dark skies.