Monday Bites: Clown & Cleopatra

 Monday Bites: Clown & Cleopatra

Eskimo/Clown-faced Nebula
Credit: Public Domain,
via Wikimedia Commons.

NGC 2392, a planetary nebula in the Northern constellation of Gemini, has many names. Squinting at their telescope's eyepiece, to some, the outer shell of expanding gas, ionized and propelled to breakneck speeds under the influence of a dying star at its center, decked with filaments of expulsed stellar material, gives the appearance of someone wearing a parka. Hence the name Eskimo Nebula. To others, the parka hood reflects a lion's mane. And there are those who see a clown. However, the IAU notes that the names are derogatory, and instead, its catalog number, NGC 2392, should be used. 

All controversy apart, NGC 2392, in the constellation of Gemini, is undeniably a spectacle of the Northern winter nights. There's considerable uncertainty regarding its distance from Earth, as estimates vary from around 2,500 to 6,500 light-years. Hubble's photograph (taken in 2000) here doesn't directly convey to the layman that NGC 2392 is a bipolar nebula, with two spherical blobs of gas expanding on either side of the central star. At the nebula's heart sits an O-type star that has already left the main sequence some 10,000 years ago and is puffing out material from time to time. 

O-type stars are a rare class of hot, blue-white, giant stars having surface temperatures upwards of 30,000 K and weighing over 40 to 200 times the mass of our Sun. They are the colossal giants and are extremely luminous. While stars like our Sun end up with their cores left behind as a cooling white dwarf inside a glowing planetary nebula of expulsed stellar material, O-type stars end their lives as Wolf-Rayet (WR) stars.  

In this photograph, the frontal bubble of stellar material obscures the lower lobe. Both the lobes fly outward from the central stars at a mind-shattering velocity of 1.5 million km/h (or about 900,000 mph). The parks-hood, the equatorial material, spreads sideways, squealing at 115,000 km/h (72,000 mph). The bubbles display complex intermingling of gas. Astronomers believe that the equatorial dispersion of stellar material happened during the central star's red-giant phase. Its vibrant colors result from ionized gases.