https://avi-loeb.medium.com/a-new-hubble-space-telescope-image-of-3i-atlas-926b4c7b2dd0
A New Hubble Space Telescope Image of 3I/ATLAS
Avi Loeb
4 min read
·
2 hours ago
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A post-perihelion image of the interstellar object 3I/ATLAS taken by the Wide Field Camera 3 onboard the Hubble Space Telescope on November 30, 2025. At that time, 3I/ATLAS was 286 million kilometers from Earth. Background stars appear as streaks of light. The glowing halo (coma) has a teardrop shape with an anti-tail elongated towards the Sun. The sunward direction is pointing towards the lower left, as marked by the yellow arrow. (Image credit:
NASA, ESA, STScI, D. Jewitt (UCLA), M.-T. Hui (Shanghai Astronomical Observatory). Image Processing: J. DePasquale (STScI).
The interstellar visitor
3I/ATLAS was reobserved by the Hubble Space Telescope from a distance of 286 million kilometers on November 30, 2025, a month after its closest approach to the Sun (perihelion). The image shows a teardrop-shaped glowing halo that extends towards the Sun.
This sunward anti-tail extension was also apparent in the pre-perihelion Hubble image of 3I/ATLAS, taken on July 21, 2025, as 3I/ATLAS was approaching the Sun from a distance that is 56% larger from Earth. The new radius of the glow is about 40,000 kilometers and its anti-tail extension goes out to about 60,000 kilometers.
In a recent paper, accessible
here, I suggested that the teardrop of the coma in post-perihelion images of 3I/ATLAS is associated with a large number of macroscopic non-volatile objects that separated from it as a result of its measured non-gravitational acceleration away from the Sun.
My paper predicted that by November 30th, the swarm of objects would be closer to the Sun than 3I/ATLAS by about 60,000 kilometers if the objects overlapped with 3I/ATLAS at perihelion. This separation is in perfect agreement with the anti-tail extension of the teardrop shape in the new Hubble image.
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A pre-perihelion image of 3I/ATLAS by the Hubble Space Telescope on July 21, 2025.
The brightness contours feature an elongation of scattered sunlight towards the Sun and not away from it, as commonly observed for solar system comets. The yellow and green arrows mark, respectively, the projected negative heliocentric velocity vector and the projected anti-solar direction. The angular scale bar of 4” corresponds to 8,650 kilometers at 3I/ATLAS’ distance of 2.98 times the Earth-Sun separation. (Credit:
Jewitt et al. 2025)
We are awaiting the release of the full Hubble data set which includes ultraviolet spectroscopy to determine the composition of the gas plume around 3I/ATLAS.
In the meantime, amateur astronomers continue to provide magnificent large-scale images that extend out to millions of kilometers around 3I/ATLAS.
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An image of the interstellar object 3I/ATLAS, taken at 1:39 on December 2, 2025 by a 12-inch telescope in Farm Tivoli, Namibia with exposures lasting 20,6,6 and 6 minutes.
North is up. The sunward direction is pointing to the lower left. The field of view is 75 by 110 arcminutes corresponding to 6.1 by 9 million kilometers at the distance of 280 million kilometers between 3I/ATLAS and Earth on that date. (Image credit: Gerald Rhemann and Michael Jäger, posted
here)