HONG KONG: Using two orbiting space telescopes, astronomers have captured a striking new image of the nebula NGC 3242
It was discovered on February 7, 1785 by German-born British astronomer and composer William Herschel.
The nebula is sometimes called the Jupiter’s Ghost, or the Ghost of Jupiter, for its similar appearance to the familiar gas giant.
In the small telescope it shows as a pale bluish softly glowing disc.
The total magnitude is 9; the bright 11th magnitude (11.4) central star, with a temperature of 90,000 Kelvin, shines with the total light of around 1,000 suns.
The new composite image reveals how mighty winds released by the central star – the white dwarf – are shaping the double-shell structure of the nebula.
The blue glow filling the inner bubble represents X-ray emission from hot gas, heated up to over 2,000,000 degrees by shocks in the fast stellar winds, gusting at about 2,400 km/s against the ambient gas.
The green glow marks cooler concentrations of gas seen in optical light through the emission of oxygen, revealing the edge of the inner shell in contrast to the more diffuse gas making up the outer shell.
The two flame-shaped features, visible in red to the upper right and lower left of the inner bubble, are pockets of even cooler gas, seen also in optical light through the emission of nitrogen.
