# Webb's Capotauro, an early-galaxy candidate, shifted 0.13 arcseconds in 3.5 years; likely a brown dwarf

- Published: 2026-11-14 02:33 UTC
- Section: Sky & Space › Astronomy
- Tags: Capotauro, James Webb Space Telescope, early galaxy candidate, Y dwarf, cold brown dwarf, proper motion, CEERS survey, University of Edinburgh, redshift 32, NIRCam
- URL: https://realtech.media/news/rt-b533e56c86472af0dcdd1930_webb_s_capotauro/

**Repeat Webb images from June 2026 show the red point moved about 0.13 arcseconds since December 2022, which, the authors say, rules out a distant galaxy.**

![Webb's Capotauro, an early-galaxy candidate, shifted 0.13 arcseconds in 3.5 years; likely a brown dwarf](https://realtech.media/media/2026/11/27488e03a579a141.jpg)
*Earth.com*

A team led from the Institute for Astronomy at the University of Edinburgh reports that Capotauro, a compact red point once considered a candidate for the earliest galaxy, is a cold brown dwarf in the Milky Way. The James Webb Space Telescope recorded the object in December 2022 during the CEERS survey and returned to the field in June 2026, when the point had moved by 132 milliarcseconds, give or take 20, about 0.13 arcseconds, according to Earth.com [1]. The detection exceeds 6 sigma [1].

## Why it looked like a galaxy

The object, catalogued as U-100588, was picked out by Giovanni Gandolfi and colleagues, who named it Capotauro. It appeared only in the reddest NIRCam filters and vanished at shorter wavelengths, a pattern typical of distant galaxies, whose shorter wavelengths are absorbed by early-universe hydrogen [1]. Gandolfi's team favored a redshift of about 32, while the confirmed record at the time was near redshift 14, a galaxy seen 280 million years after the Big Bang [1]. The same team also listed a cold brown dwarf or a free-floating planet as possibilities [1].

According to Liu's team, water, methane and ammonia in a Y dwarf's atmosphere can erase almost all light through the F356W filter. The brightness then rises sharply near 4 to 5 microns, which, read as a hydrogen break, gives a redshift of about 30 to 32 [1].

## Measurement and remaining uncertainty

Two Webb programs, MINERVA and SPAM, covered the field in mid-to-late June 2026, giving a second epoch about 3.5 years after the discovery data. First author Fengyuan Liu's group measured the position in four images and built a local reference frame from 68 compact sources within 3 arcminutes. It also ran 1,200 trials with artificial moving sources at 75 blank positions to test the noise [1]. The paper states that the data "completely exclude" any extragalactic source, and the brightness did not change significantly over 3.5 years [1].

The best template match is spectral type Y1, with a temperature near 350 Kelvin, about 77 degrees Celsius. The estimated distance is 730 parsecs, with an uncertainty of 110, or about 2,400 light-years, and the sideways speed is about 132 kilometers per second [1]. This distance is not a direct measurement: parallax could not be determined, and the figure comes from scaling template brightness. The template library stops at type Y1, so the object could be colder and closer [1]. The authors suggest a third set of Webb images timed for parallax, and call detailed spectroscopy "inherently impractical" [1].

## Sources

1. [Earth.com](https://www.earth.com/space/capotauro-webb-galaxy-candidate-brown-dwarf)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-b533e56c86472af0dcdd1930_webb_s_capotauro/