Meet the remarkable nebula shaped like a Christmas tree

Arrayed with a simple triangular outline above S Monocerotis, the stars of NGC 2264 are popularly known as the Christmas Tree star cluster. Image Credit & Copyright: Michael Kalika, NASA (with permission).

To mark the Christmas period, astronomers from NASA have drawn attention to a spectacular region of space that looks remarkably like a glowing Christmas tree (in the shape of a Nordic tree and lit with merry lights).

Known as NGC 2264, this distant star-forming region sits about 2,700 light-years away and is filled with newborn stars lighting up clouds of gas and dust. The stars form a triangular shape called the Christmas Tree cluster, crowned by the dramatic Cone Nebula and wrapped in the swirling Fox Fur Nebula below.

This region, the constellation Monoceros, is positioned near the celestial equator and close to the flat disk of the Milky Way, which makes it visible from many locations on Earth during certain seasons. The binary star system A0620-00 in the constellation of Monoceros is at a distance of roughly 3,300 light-years (1,000 parsecs) away.

The combination of these features creates a festive cosmic scene spanning nearly 80 light-years, showing how young stars shape their surroundings on a truly galactic scale.

Why does the image resemble a Christmas tree?

The scene, as captured in the iages, is filled with enormous clouds of interstellar gas and dust, the raw ingredients needed to form stars. As young stars ignite within these clouds, they release intense energy that causes the surrounding hydrogen gas to glow red.

These glowing regions are known as emission nebulae. An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. Here, the most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star.

Dark dust clouds thread through the area as well, blocking light from stars behind them and creating dramatic shadows. In places where this dust lies close to hot, newly formed stars, it reflects their light instead of absorbing it, producing soft blue regions called reflection nebulae.

Describing the Christmas Tree

In a research note, the scientists behind the observation state: “Near the center of NGC 2264 is S Monocerotis, a bright variable star whose brightness changes over time. This star is surrounded by a noticeable blue glow caused by reflected starlight from nearby dust. Above S Monocerotis, a group of young stars forms a simple triangular pattern. Because of this distinctive shape, the cluster has become widely known as the Christmas Tree star cluster.”

At the top of this star filled scene sits the Cone Nebula, a tall structure of gas and dust shaped by powerful radiation from nearby young stars. Beneath it spreads a tangled and glowing cloud called the Fox Fur Nebula, named for its textured, fur like appearance. These features are constantly being reshaped as energetic starlight pushes and sculpts the surrounding material.

The Cone Nebula spans about 7 light-years and is mainly composed of molecular hydrogen gas and interstellar dust. The Christmas Tree Cluster contains more than 600 young stars, some of which are spectral types O and B that emit intense ultraviolet radiation. This radiation interacts with the surrounding molecular cloud, causing photo-ionization of the gas and the formation of an H II region.