Hubble Celebrates 36 Years with Fascinating View of the Trifid Nebula
The Hubble Space Telescope of NASA/ESA has once again focused on a scene it first captured in 1997, in honor of its 36th anniversary: a small section of a star formation region in the constellation Sagittarius, about 5,000 light-years away, known as the Trifid Nebula.
The Hubble Space Telescope of NASA/ESA has once again focused on a scene it first captured in 1997, in honor of its 36th anniversary: a small section of a star formation region in the constellation Sagittarius, about 5,000 light-years away, known as the Trifid Nebula. The image shows changes occurring over incredibly short time spans and evokes awe and wonder at our ever-evolving universe.
The colors in Hubble's image of the shimmering star formation region in visible light resemble an underwater landscape filled with fine-grained sediments swirling through the depths of the ocean. Several massive stars, located outside this image section, have shaped this region for at least 300,000 years. Their strong ultraviolet winds continue to inflate a massive bubble, a small part of which is visible here. This bubble compresses and pushes the gas and dust of the cloud, triggering new waves of star formation.
This is not the first time Hubble has observed this motif. The telescope studied the Trifid Nebula back in 1997 and has now, 29 years later, utilized almost its entire operational lifespan to show us changes in the nebula within a timeframe comprehensible to humans. So why observe the same location again? In addition to monitoring changes over time, Hubble is also equipped with an improved camera that features a wider field of view and higher sensitivity, installed during its 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 a wavy "body" of a rust-colored cloud of gas and dust that resembles a sea lemon or a sea snail, gliding through the cosmos. The left "horn" of the cosmic sea lemon is part of Herbig-Haro 399, a plasma jet that has been ejected at regular intervals by a young protostar [1] embedded in the head of the sea lemon for centuries. Observe how the jet expands. By measuring the observed changes, researchers can gauge the speeds of the outflows and determine how much energy the protostar is feeding into these regions. The measurements provide insights into how newly formed stars interact with their environment.
Just below, signs of the counter-jet can be recognized: jagged orange and red lines running down the back of the sea lemon's neck, where a natural V shape is outlined in the brown dust. The darker, more triangular "horn" to the right of the "head" houses another young star at its tip. Zoom in to see a faint red dot with a tiny jet. The green arc above may indicate that a circumstellar disk is being eroded by the intense ultraviolet light of nearby massive stars. The clearer the area around this protostar, the more likely it is that its formation is nearly complete.
Immediately to the left of the Cosmic Sea Lemon is a small, faint pillar. Much of the gas and dust of this pillar has been blown away, but the densest material at its tip has remained. Stripes and sharp lines provide further clues about the activity of other young stars. One example can be found near the center: a wavy, diagonally running line that starts in bright orange and ends in a brilliant red. In the image comparison, it appears to be moving, suggesting it could be a jet ejected by another actively forming star hidden deep in the dust.
Prismatic "Sea" of Colors
In the visible light observations of the Hubble Telescope, the view in the upper left is the clearest, where the image appears bluish. Strong ultraviolet light from massive stars that are not in the field of view has ionized electrons from the nearby gas, creating a glow, while winds shape a bubble by sweeping away the surrounding dust. At the tip of the head of the Cosmic Sea Lemon, bright yellow gas rises. This is an example of how ultraviolet light penetrates the dark brown dust, dissolving and breaking down gas and dust.
Many ridges and slopes of dark brown material will remain for several million years, while the ultraviolet light from the stars slowly erodes the gas. In the densest areas are protostars [1] that are hidden in visible light. The farthest right corner is almost pitch black. Here, the dust is densest. The stars that appear here may not belong to this star formation region—they could be closer to us, in the foreground.
Now keep an eye out for bright orange spheres. These stars have fully formed and cleared the space around them. Over millions of years, the gas and dust that make up the nebula will vanish—and only the stars will remain.
Unprecedented Longevity, Uninterrupted Discoveries
The diverse instruments of the Hubble Telescope and the broad spectrum of light it captures—from ultraviolet to near-infrared—have helped researchers make groundbreaking discoveries for decades, providing new data daily that will inevitably lead to further findings.
In the past year, Hubble's discoveries ranged from a relic of early galaxy formation to a galaxy so faint it is nearly invisible, as well as unknown cosmic anomalies found with the help of AI. Researchers observed for the first time asteroids colliding in another star system, while Hubble serendipitously captured a breaking comet in our own solar system. The long-standing prediction that our Milky Way will collide with Andromeda in the distant future has been called into question by a new study using data from the Hubble Telescope and the ESA probe Gaia. Hubble also tracked the interstellar comet 3I/ATLAS, which unexpectedly appeared in the solar system last year, contributing to a rapid estimate of its size.
The 36th operational year of the Hubble Telescope has also provided further impressive insights into the cosmos. These included the star formation region N11 in the Large Magellanic Cloud, the shells of stellar dust that make up the Egg Nebula, the Cat's Eye Nebula along with the ESA probe Euclid, and a brand-new image of the famous Crab Nebula. Hubble also showcased the glowing heart of M82, the swirling spiral galaxies UGC 11397 and Arp 4, dust rings around the galaxy NGC 7722, the sparkling stars of the globular cluster NGC 1786, and the massive galaxy cluster Abell 209.
The telescope has conducted over 1.7 million observations to date. Nearly 29,000 astronomers have published scientific articles in peer-reviewed journals based on Hubble data collected over the 36-year operational period of the telescope. This has led to more than 23,000 publications, including almost 1,100 in 2025 alone. Since 2022, researchers have regularly combined Hubble observations with those from the James Webb Space Telescope to expand possibilities for new discoveries.
Notes
[1] A protostar is a collection of interstellar gas and dust that is currently collapsing to form a star.
Background Information
The Hubble Space Telescope is a project of international collaboration between ESA and NASA.
Image credit: NASA, ESA, STScI. Image processing: J. DePasquale (STScI)
