In astronomy, the brightest objects dominate the light we receive.

When new stars form, it’s the blue supergiants that shine brightest.

The same region of space, just to the right of the central bright cluster of stars in Pismis 24, shows several stars against a black background in the Hubble image (at right), but many more stars and an eerie blue haze in the JWST image (at left). The blue color is caused by the emission of neutral hydrogen atoms, recombining after being ionized by the intense ultraviolet radiation emanating from the young surrounding stars.

Alongside them, fainter, dimmer stars are much more abundant.

Whereas only the brightest stars, and the star in the foreground of neutral material, are visible to primarily optical observatories like Hubble, JWST reveals bright stars, faint stars, and even background stars of the Milky Way, despite the enormous quantities and densities of gas and dust. For studying the properties and evolution of these young, massive stars, there is no better tool than JWST for the endeavor at present.

Below the mass threshold to form stars, sub-stellar objects may yet outnumber the stars.

This glowing region, filled with wispy gas, dark red dust, and brilliant blue and white stars, lies inside the nebulous star cluster Westerlund 2, located 20,000 light-years away in the constellation of Carina, toward the galactic center. With JWST, it isn’t only the bright stars that dominate, but cooler ones, brown dwarfs, and even planetary mass objects as small as the mass of several Jupiters. The infrared glow of that material, visible to JWST’s NIRCam and/or MIRI instruments, enables the detection of fainter, cooler objects than ever before.

In nebulae such as:

• the Cosmic Cliffs,

This three-panel image shows the view of the Carina Nebula’s “cosmic cliffs” as seen by Hubble (top), JWST’s NIRCam instrument (middle), and JWST’s MIRI instrument (bottom). With its first science release in July of 2022, a new era in astronomy has truly arrived.

• the great Orion Nebula,

These two side-by-side views are centered on the Trapezium Cluster within the Orion Nebula, and show both short-infrared-wavelength (top) and long-infrared-wavelength (bottom) views of this region of space, as taken with JWST’s NIRCam imager.

• and the Rho Ophiuchi cloud complex,

This image of the Rho Ophiuchi molecular cloud complex was released for the first science anniversary of JWST back in 2023. It showcases young stars carving out features in the surrounding star-forming material, including stellar winds and outflowing jets. Despite the apparent chaos, this is actually one of the quieter stellar nurseries known.

brown dwarfs and super-Jupiter objects appear to JWST’s eyes.

Five different JuMBOs, or Jupiter-Mass Binary Objects, found within a very small region of the Orion Nebula. Note that these particular JuMBOs are numbered 31-to-35, indicating that there are dozens of these objects. Of all the Jupiter-mass objects found by this survey, about 9% of them are locked up in binary systems.

Within these regions, cold clouds of gas collapse, creating massive stellar seeds.

This JWST image shows the large, asymmetric protostellar jet emerging from the young star-forming region Sharpless 2-284. Located 15,000 light-years away, the protostellar jet spans an impressive 8 light-years across: driven by the most massive young star(s) and protostars within them. While some of the objects shown here are full-fledged stars, the majority of stars still within the nebulous region at the center remain in the protostellar phase, having not yet reached the main sequence as far as stellar evolution goes.

Ultraviolet radiation and winds from massive stars race to blow that gas away.

Embedded within a cloud of gas and dust, these two nearby stars are in very different environment. The brighter, orange star is more deeply wrapped in gas and dust, and the effects of the star’s winds and radiation can be seen carving features in and evaporating the neutral matter surrounding it. In time, the surrounding, shrouding material will be evaporated away entirely.

While the brightest stars become cosmic winners, even more losers — failed stars — persist.

This zoomed-in region from JWST’s NIRCam imager shows a portion of the Orion molecular cloud complex, complete with new protostars and young protoplanetary disks. Stellar outflows and dusty, shrouded regions are all visible alongside one another, showcasing a wide range of phenomena found within star-forming regions.

JWST’s unique long-wavelength capabilities reveal these sub-stellar objects.

Preliminary total system throughput for each NIRCam filter, including contributions from the JWST Optical Telescope Element (OTE), NIRCam optical train, dichroics, filters, and detector quantum efficiency (QE). Throughput refers to photon-to-electron conversion efficiency. By using a series of JWST filters extending to much longer wavelengths than Hubble’s limit (between 1.6 and 2.0 microns), JWST can reveal details that are completely invisible to Hubble. The more filters that are leveraged in a single image, the greater the amount of details and features that can be revealed.

Within nearby nebula IC 348, 1000 light-years away in Perseus, a new record was set in 2023.

This 2023-era image from JWST shows the star-forming nebula IC 348. Searching the cluster for free-floating brown dwarfs, astronomers uncovered several objects, highlighted in the inset panels labeled 1, 2, and 3, that are less than 8 times the mass of Jupiter, including a then-record holder just 3-4 times Jupiter’s mass. For comparison, the lower mass limit for brown dwarfs was thought to be 13 solar masses, raising questions about just what these objects are and how they came to be.

A warm, glowing super-Jupiter object, just 3-4 times Jupiter’s mass, was discovered.

This all-new JWST image of the nebula IC 348 extends and enhances all previous views, with the reflective interstellar material bearing many similarities to the famous “fox fur nebula” and the blue region to the upper right showcasing Herbig Haro objects with plasma outflows emanating from them. Thousands of new stars and protostars dominate this scene, just 1000 light-years away from Earth.

That same team has now re-broken that record: with objects just twice Jupiter’s mass.

This image, which focuses on the central star cluster within the star-forming region IC 348, is dominated by two similarly-massed bright blue stars. However, many lower-mass stars, as well as sub-stellar objects and protostars, can be seen amidst the interstellar material that reflects this cumulative starlight as well. Among them are low-mass brown dwarfs and even objects thought to be less massive than the brown dwarf minimum mass.

Glowing like brown dwarfs, they’re likely below the deuterium-fusion mass threshold.

This tiny region of the full JWST NIRCam mosaic of IC 348 showcases a gas-and-dust-rich region with stars and protostars of an enormous variety of masses inside. While some of the “dots” are background galaxies poking through the mist and the big, bright, blue, spike-rich features are the most massive new stars, among the faintest of the objects are sub-stellar objects known as brown dwarfs and even lower-mass objects that are consistent with super-Jupiter mass planets, but glow like brown dwarfs do. This could represent a new class of object in astronomy.

Spectroscopic follow-ups confirmed their properties: just 0.19% the Sun’s mass.

These images show NIRCam images of pairs of brown dwarfs and one pair of candidate brown dwarfs (lower right), while the spectra acquired with NIRSpec, at far right, confirm the nature and masses of these objects. With one pair having a mass of just 2 Jupiter masses, it is consistent with being the lightest brown dwarf known, despite being below the mass limit to fuse deuterium in theory.

One possesses a disc.

These two different-looking, bright stars are actually similar in mass and intrinsic color, but the upper one is behind a much larger amount of shrouded material. The faint red blobs and streaks are shockwaves in the surrounding gas, while the faint background dost are a mix of significantly lower-mass stars and much more distant background galaxies.

Several show signatures of hydrocarbons.

This gorgeous but chaotic image shows a region of nearby star-forming region IC 348, as imaged with JWST’s NIRCam imager, which hosts a number of protostars and complex outflows driven by a special class of star: Herbig-Haro stars. Several other protostars and lots of interstellar material, reflecting the light from other stars, can be seen as well. The material is rich in complex carbon-containing molecules known as PAHs: polycyclic aromatic hydrocarbons.

These new observations suggest a surprising all-new class of sub-stellar objects.

Within nebula IC 348, A large number of stars of different masses were discovered with earlier JWST imagery (black points). With follow-up work, including spectroscopy, there are new candidates added, particularly at the low-mass end of the spectrum. This includes the lowest-mass brown dwarfs ever detected: potentially a mysterious new class of sub-stellar object.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.

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