James Webb spots tiniest known brown dwarf in stunning star cluster

By Georgina Torbet Updated December 15, 2023

A new image from the James Webb Space Telescope shows a stunning view of a star cluster that contains some of the smallest brown dwarfs ever identified. A brown dwarf, also sometimes known as a failed star, is an object halfway between a star and a planet — too big to be a planet but not large enough to sustain the nuclear fusion that defines a star.

It may sound surprising, but the definition of when something stops being a planet and starts being a star is, in fact, a little unclear. Brown dwarfs differ from planets in that they form like stars do, collapsing due to gravity, but they don’t sustain fusion, and their size can be comparable to large planets. Researchers study brown dwarfs to learn about what makes the difference between these two classes of objects.

“One basic question you’ll find in every astronomy textbook is, what are the smallest stars? That’s what we’re trying to answer,” explained lead author of the Webb research, Kevin Luhman of Pennsylvania State University, in a statement.

The central portion of the star cluster IC 348. Astronomers combed the cluster in search of tiny, free-floating brown dwarfs. — This image from the NIRCam (Near-Infrared Camera) instrument on the NASA/ESA/CSA James Webb Space Telescope shows the central portion of the star cluster IC 348. Astronomers combed the cluster in search of tiny, free-floating brown dwarfs: objects too small to be stars but larger than most planets. They found three brown dwarfs that are less than eight times the mass of Jupiter. The smallest weighs just three to four times as much as Jupiter, challenging theories for star formation. NASA, ESA, CSA, STScI, and K. Luhman (Penn State University) and C. Alves de Oliveira (European Space Agency)

This image shows the star cluster IC 348, which is young and is located in a star-forming region called Perseus. Within this cluster, the researcher found three small objects with a mass between three and eight times that of Jupiter, with surface temperatures between 830 and 1,500 degrees Celsius. That’s hot for a planet but not hot enough to be a star. The smallest they found was just three or four times the mass of Jupiter, making it the smallest brown dwarf identified to date.

The fact the object is so small means it’s difficult to explain how it formed. “It’s pretty easy for current models to make giant planets in a disc around a star,” said researcher Catarina Alves de Oliveira of the European Space Agency. “But in this cluster, it would be unlikely that this object formed in a disc, instead forming like a star, and three Jupiter masses is 300 times smaller than our Sun. So we have to ask, how does the star formation process operate at such very, very small masses?”

The research is published in The Astronomical Journal.

Topics

Tech News

Georgina Torbet

Space Writer

Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…

Space

See a stunning 3D visualization of astronomy’s most beautiful object

This image is a mosaic of visible-light and infrared-light views of the same frame from the Pillars of Creation visualization. The three-dimensional model of the pillars created for the visualization sequence is alternately shown in the Hubble Space Telescope version (visible light) and the Webb Space Telescope version (infrared light).

This image is a mosaic of visible-light and infrared-light views of the same frame from the Pillars of Creation visualization. The three-dimensional model of the pillars created for the visualization sequence is alternately shown in the Hubble Space Telescope version (visible light) and the Webb Space Telescope version (infrared light). Greg Bacon (STScI), Ralf Crawford (STScI), Joseph DePasquale (STScI), Leah Hustak (STScI), Christian Nieves (STScI), Joseph Olmsted (STScI), Alyssa Pagan (STScI), Frank Summers (STScI), NASA's Universe of Learning

The Pillars of Creation are perhaps the most famous object in all of astronomy. Part of the Eagle Nebula, this vista was first captured by the Hubble Space Telescope in 1995, and has captivated the public ever since with its dramatic rising pillars of dust and gas that stretch several light-years high. The nebula has been imaged often since then, including again by Hubble in 2014 and more recently by the James Webb Space Telescope in 2022.

Space

Gorgeous Webb image of Serpens Nebula shows a strange alignment

This image shows the centre of the Serpens Nebula as seen by the NASA/ESA/CSA James Webb Space Telescope’s Near-InfraRed Camera (NIRCam).

The Serpens Nebula, located 1,300 light-years from Earth, is home to a particularly dense cluster of newly forming stars (about 100,000 years old), some of which will eventually grow to the mass of our Sun. Webb’s image of this nebula revealed a grouping of aligned protostellar outflows (seen in the top left). These jets are identified by bright clumpy streaks that appear red, which are shock waves caused when the jet hits the surrounding gas and dust. NASA, ESA, CSA, STScI, K. Pontoppidan (NASA’s Jet Propulsion Laboratory), J. Green (Space Telescope Science Institute)

This stunning new image from the James Webb Space Telescope shows the famous Serpens Nebula, a dense star-forming region where new stars are being born amid clouds of dust and gas. Unlike some other nebulae, which are illuminated by radiation from stars that causes them to glow, this is a type called a reflection nebula, so it only shines due to the light that reflects from other sources.

Space

Well-known star turns out to be not one star, but twins

This artist’s concept shows two young stars nearing the end of their formation. Encircling the stars are disks of leftover gas and dust from which planets may form. Jets of gas shoot away from the stars’ north and south poles.

This artist’s concept shows two young stars nearing the end of their formation. Encircling the stars are disks of leftover gas and dust from which planets may form. Jets of gas shoot away from the stars’ north and south poles. U.S. NSF/NSF NRAO/B. Saxton

There are some regions and objects that become favorite targets for astronomers -- often because they are nearby (and so easier to observe) and because they are a well-known example of an object like a stellar nursery or a black hole. But occasionally, even these well-known objects turn out to be hiding surprises. This was the case recently, when observations from the James Webb Space Telescope revealed that a particular star, WL 20S, in the frequently observed WL20 region, turned out not to be a single star at all, but actually a pair.