Five thousand light-years away, in the constellation Gemini, a star that ran out of fuel is wearing a lion’s face. The James Webb Space Telescope pointed its NIRCam and MIRI cameras at NGC 2392, better known now as the Lion Nebula, last November, and NASA released the results this August. We keep going back to them!
Everything in the frame came out of one star. The bright point at the center, which NASA likens to the lion’s button nose, is a white dwarf: the leftover core of a lower-mass star that burned through its nuclear fuel, began to pulse, and spent several thousand years shedding its outer layers. That core is still fiercely hot. Its radiation is ionizing the gas around it, in NASA’s words “cooking” the nebula from the inside, and the glowing bubble of hydrogen it makes is the lion’s face. Look closely and the face is all ribbed shells and rings, with tendrils that destroy dust wherever they reach.
The mane is dust. More precisely, it’s the inside wall of a dust shell, lit by the star at the center. Toward its edges sit small, dense knots trailing tails like comets. They’ve survived the radiation so far and they shade the material behind them, which is why the mane looks combed outward. Little yellow pockets in the full-color image are clumps of molecular hydrogen.
Webb’s mid-infrared camera on its own sorts the scene even more sharply. Here the mane turns cyan and the hardy knots go purple.
A face with a few names
NGC 2392 has been making people see faces since William Herschel found it in 1787. Through small telescopes on the ground it looked like a face peering out of a fur-lined hood, which earned it a nickname NASA stopped using in 2020 because the word is a colonial term with a racist history for Arctic Indigenous peoples. Others have called it the Clown Face Nebula. The lion is the newest, and it’s the one that suits Webb’s picture best.
One small warning if you go looking for more. An unrelated cloud in Cepheus, Sharpless 2-132, also goes by the Lion Nebula, and its lion is seen side on, walking.
Twenty-six years after Hubble
Hubble photographed the same nebula in January 2000. It was the telescope’s first look at the sky after astronauts serviced it the month before, and the picture became the famous one: warm and orange, with a green glow and a ring of comet-shaped knots. In some ways it’s the more leonine of the two. Webb keeps the same overall shape but splits the scene into its ingredients, the haze of ionized gas, the dust, the molecular hydrogen. We lined the two up at the same scale. Drag across them and watch a quarter century of telescope progress sweep over one dying star!
Hubble · 2000
Webb · 2026
A snapshot, not a statue
Webb's frame covers about 2.6 light-years. It took several thousand years for the star's leftovers to settle into this shape, and they haven't stopped moving. Astronomers expect NGC 2392 to drift apart completely in about 10,000 years, a blink by the standards of stars.
Our Sun is a lower-mass star too, and billions of years from now it should go out in much the same way. We hope it makes a face this good!
Webb images: NASA, ESA, CSA, STScI; image processing by Alyssa Pagan (STScI). Hubble image: NASA, ESA, Andrew Fruchter (STScI) and the ERO team. Read NASA's release, Lion Nebula Roars to Life With NASA's Webb. (via Colossal)
Keep exploring: Webb's portrait of another dying star, the Red Spider Nebula; the Pillars of Creation in infrared; and our roundup of the best images Webb has taken so far.
