If you launch humanity’s strongest telescope, you anticipate outcomes. The JWST has delivered glorious outcomes by detecting historic galaxies, figuring out chemical substances in exoplanet atmospheres, and peering into star-forming areas with extra element and readability than some other telescope.
However each time a brand new telescope is about to enter service, astronomers inform us they’re excited not solely concerning the anticipated outcomes but additionally concerning the stunning outcomes. And like different telescopes, the JWST has additionally delivered some surprises. Whereas going about its enterprise, the JWST has found 21 brown dwarfs.
Brown dwarfs are ‘in between’ objects. They’re typically known as ‘failed stars.’ They’re extra huge than a fuel large, however much less huge than a star. They by no means grew huge sufficient to set off hydrogen fusion, the hallmark of a foremost sequence star.
Brown dwarfs won’t appear very fascinating. They’re not planets, and so they’re not stars. However they’re a part of nature, in order that they match into the grand scheme of issues someway.
There are scientific causes to need to be taught extra about them. “Deciding on and characterizing these sources is important for exploring the stellar initial mass function, understanding binary stellar evolution, and for growing the census of stars round which probably liveable planets could lie,” the authors of a brand new paper clarify.
The paper is “Brown Dwarf Candidates in the JADES and CEERS Extragalactic Surveys,” and it’s out there on the pre-press website arxiv.org. The lead writer is Kevin Hainline, an Assistant Analysis Professor at Steward Observatory.
Brown dwarfs emit most of their gentle within the infrared, which the JWST focuses on sensing. However brown dwarfs are nonetheless troublesome to detect, even for the mighty JWST. The 21 new brown dwarfs have been present in knowledge from two completely different surveys carried out by the JWST that weren’t centered on brown dwarfs: JADES and CEERS.
JADES is the JWST Advanced Deep Extragalactic Survey, and CEERS is the Cosmic Evolution Early Release Science Survey. Each surveys are centered on distant, historic galaxies, one of many JWST’s major science objectives. The brand new brown dwarfs have been hidden in all their knowledge.
These findings are vital due to the situation of the brown dwarfs. Many of the brown dwarfs we learn about are in our stellar neighbourhood, as a result of that’s the place they’re best to see. However that’s an issue as a result of when astronomers need to examine one thing, they want an excellent, consultant pattern. They’ll’t draw any sturdy conclusions from a pattern that’s all from one area of a galaxy.
“It is important to increase on these samples, as brown dwarf stars at these distances assist us perceive the historical past of star formation within the Milky Means,” the authors write. Many of the 21 newly found brown dwarfs are within the Milky Means’s thick disk and halo. They’re between between 0.1 – 4.2 kpc., about 360 light-years to 13,700 light-years away.
A number of the outcomes of this analysis present how a lot we’ve got but to find out about brown dwarfs. Our lack of information shouldn’t come as a shock. Brown dwarfs have been first theorized to exist within the Sixties, however the first unambiguous detections weren’t till the mid-Nineteen Nineties. Astrophysicists are nonetheless determining the place they slot in.
The areas of a number of the brown dwarfs, particularly those within the galactic halo, are at odds with what form we expect galaxies take. “Whereas the vast majority of the sources are within the thick disk, we do discover 4 sources which are probably within the Milky Means halo,” the researchers write. “These sources are poorly match with galaxy template fashions.” Their atmospheric spectra additionally aren’t an excellent match with current models.
The group of researchers discovered these brown dwarfs in simply the primary yr of knowledge from each JADES and CEERS. So they may possible discover extra sooner or later, particularly since this work reveals how completely different JWST filters make the brown dwarfs discoverable. However the true enjoyable would possibly start sooner or later. “These sources present an thrilling alternative for follow-up observations with focused JWST NIRSpec spectroscopy, contemplating their positions inside the Milky Means,” the authors clarify.
Solely not too long ago, a examine within the Astrophysical Journal Letters introduced the very first focused observations of a brown dwarf with the JWST. Its title is “The First JWST Spectral Energy Distribution of a Y Dwarf.” (Brown dwarfs are of spectral sorts M, L, T, and Y.) These observations introduced some outcomes that conflicted with idea. “This supply introduced a problem to theoretical fashions, demonstrating the significance of accelerating the variety of these sources explored spectroscopically,” the authors write. So it’s important to look at extra brown dwarfs with the JWST’s NIRSpec and MIRI devices.
Brown dwarfs are nonetheless elusive targets. They’re very faint and really low-mass in comparison with foremost sequence stars. Some could be as massive as 80 instances extra huge than Jupiter, although they’re all about the identical radius as Jupiter. That’s tiny for a star. Nonetheless, discovering extra of them and finding out them in larger element is important to understanding how stars and planets type. Thankfully, astronomers are about to seek out many extra of them and can start to fill within the gaps of their information.
These 21 brown dwarfs have been present in surveys which are extragalactic. These surveys are designed to detect objects exterior the Milky Means and to keep away from stellar contamination. That’s led us to a contented accident.
“Whereas extragalactic deep fields are designed to level exterior the airplane of our galaxy to attenuate stellar contamination, the utilization of JWST deep observations to gather these sources has implications for the inhabitants of objects exterior of the thick disk, which can be among the many most metal-poor and oldest stars at these temperatures within the galaxy,” the paper states.
There are a number of unanswered questions surrounding brown dwarfs. When one varieties, it varieties in a disk similar to some other star. It’s affordable to imagine that planets type within the disk similar to round different stars. However a brown dwarf’s disk has a lot much less mass than the disk round different stars, in addition to having a lot smaller radii. That ought to favour the formation of terrestrial planets like Earth relatively than fuel giants. However solely observations can conclude if that’s the case.
Brown dwarfs are neither stars nor planets, and their evolution may very well be very unusual. Astrophysicists suppose that as a brown dwarf cools, about 100 million to 500 million years after formation, unusual issues occur in its ambiance. It’s potential that dusty clouds of quartz and different minerals might type.
The authors of this paper are clearly wanting ahead to what may be a coming glut of brown dwarf detections. Some estimates say there are between 25 billion and 100 billion brown dwarfs within the Milky Means. We’re solely within the early days of finishing a census of brown dwarfs, and as astronomers detect increasingly more of them and topic them to review, we’ll perceive the place they slot in nature.
“We anticipate that the big bounty of brown dwarf candidates discovered over the following a number of years will make clear the historical past of star and planet formation in our galaxy.”
