Hubble turns 36 with a dazzling Trifid Nebula portrait

The colors in Hubble’s visible light image of this shimmering region of star-formation are reminiscent of an underwater scene filled with fine-grained sediments fluttering through the ocean’s depths.

Several massive stars, which are outside this field of view, have shaped this region for at least 300 000 years. Their powerful ultraviolet winds continue to blow an enormous bubble, a small portion of which is shown here, that pushes and compresses the cloud’s gas and dust, triggering new waves of star formation.

This isn’t the first time Hubble has gazed at this scene. The telescope observed the Trifid in 1997 and now, 29 years later, it has leveraged almost its full operational lifetime to show us changes in the nebula on human time scales. Why look at the same location again? In addition to seeing changes over time, Hubble is also equipped with an improved camera with a wider field of view and greater sensitivity that was installed during the fourth servicing mission.

Star formation in the ‘Cosmic Sea Lemon’

Hubble’s view of the Trifid Nebula (also known as Messier 20 or M20) focuses on a ‘head’ and undulating ‘body’ of a rusty-coloured cloud of gas and dust that resembles a marine sea lemon, or sea slug, that appears as if it is gliding through the cosmos.

The Cosmic Sea Lemon’s left ‘horn’ is part of Herbig-Haro 399, a jet of plasma periodically ejected over centuries by a young protostar [1] embedded in the head of the sea lemon. Watch the jet expand. Changes observed allow researchers to measure the speeds of the outflows and determine how much energy the protostar is injecting into these regions. The measurements will provide insights into how newly formed stars interact with their surroundings.

To the immediate lower right is evidence of the counter jet: jagged orange and red lines that ‘run’ down the back of the sea lemon’s neck, where a natural V appears in the brown dust.

The darker, more triangular ‘horn’ on the right of the ‘head’ hosts another young star at its tip. Zoom in to see a faint red dot with a tiny jet. The green arc above it may be evidence that a circumstellar disc is being eroded by the intense ultraviolet light from nearby massive stars. The clearer the area around this protostar suggests it may be almost finished forming.

To the immediate left of the Cosmic Sea Lemon is a small, faint pillar. Much of this pillar’s gas and dust has been blown away, but the densest material at the top persists.

Streaks and sharp lines offer more clues about other young stars’ activities. Spy an example by looking near the center for a rippling angled line that begins in a bright orange and ends in a blazing red. In the image comparison, it appears to move, which means it may be a jet shot out by another actively forming star buried deeply in dust.

Prismatic ‘sea’ of colour

In Hubble’s visible light observations, the clearest view is toward the top left, where it’s bluer. Strong ultraviolet light from massive stars, not in the field of view, stripped electrons from nearby gas, creating a glow, with winds sculpting a bubble by clearing out surrounding dust.

At the top of the Cosmic Sea Lemon’s head, bright yellow gas streams upward. This is an example of ultraviolet light plowing into the dark brown dust, stripping and dismantling the gas and dust.

Many ridges and slopes of dark brown material will remain for a few million years, as the stars’ ultraviolet light slowly eats away at the gas. The densest areas are home to protostars [1], which are obscured in visible light.

The far-right corner is nearly pitch black. This is where the dust is the densest. The stars that appear here may not be part of this star-forming region – they might be closer to us, in the foreground.

Now, scan the scene for bright orange orbs. These stars have fully formed, clearing the space around them. Over millions of years, the nebula’s gas and dust that make up the nebula will disappear – and only stars will remain.

Unprecedented longevity, nonstop discoveries

Hubble’s varied instruments and the expansive range of light it collects – from ultraviolet to near-infrared – have helped researchers make ground-breaking discoveries for decades and supply new data daily that will inevitably lead to more.

In the last year, Hubble has enabled discoveries ranging from a relic of early galaxy formation, to a galaxy so faint it’s nearly invisible, to unknown cosmic anomalies found with the help of AI. Researchers spotted asteroids colliding in another star system for the first time, while in our own Solar System Hubble serendipitously captured a comet breaking up. The long-held prediction that our Milky Way galaxy will collide with Andromeda in the distant future was challenged by a new study, using data from Hubble and ESA’s Gaia. Hubble also tracked the interstellar comet 3I/ATLAS that unexpectedly appeared in the Solar System last year, contributing with a rapid estimation of its size.

Hubble’s 36th year of operations has also brought more impressive views of the cosmos. Among these were the star-forming region N11 in the Large Magellanic Cloud, the shells of stardust that make up the Egg Nebula, the Cat’s Eye Nebula together with ESA’s Euclid, and a brand-new image of the famous Crab Nebula. Hubble also showcased the smouldering heart of M82, swirling spiral galaxies UGC 11397 and Arp 4, dust rings around galaxy NGC 7722, the glittering stars of globular cluster NGC 1786, and the immense galaxy cluster Abell 209.

The telescope has taken over 1.7 million observations to date. Almost 29 000 astronomers have published peer-reviewed science papers using Hubble data collected over the telescope’s 36-year lifetime, resulting in more than 23 000 publications, with almost 1100 in 2025 alone. Since 2022, researchers have regularly combined Hubble’s observations with those from the NASA/ESA/CSA James Webb Space Telescope to push opportunities for discovery further.

[1] A protostar is a mass of interstellar gas and dust in the process of collapsing to form a star.

More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

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