Photo Release: Hubble dazzles with young stars in Trifid Nebula for 36th anniversary

Reporting by ESA/Hubble

The NASA/ESA Hubble Space Telescope looked at a scene it first captured in 1997 in honour of its 36th anniversary: a small portion of a star-forming region about 5000 light-years away in the constellation Sagittarius, known as the Trifid Nebula. The image shows changes over incredibly short timescales and instills a sense of awe and wonder about our ever-changing Universe.

The colours 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.

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.

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.