Comet 3I/ATLAS gains Hubble focus in recent observation of coma and gaseous tails

Telescópio Espacial Hubble captured a new image of the interstellar comet 3I/ATLAS on November 30, 2025, when the object was 286 million kilometers from Terra. Essa observation, carried out by Agência Espacial Norte-Americana (NASA) in partnership with Agência Espacial Europeia (ESA), reveals a bluish coma around the nucleus, indicating the release of gases and dust. The comet, the third interstellar visitor confirmed in Sistema Solar, remains in a hyperbolic orbit after its perihelion in October.

Astronomers point out that Hubble tracked the rapid movement of 3I/ATLAS, resulting in background stars appearing as streaks of light in the image. Essa technique allowed details of the expanded gaseous atmosphere to be recorded. The capture comes months after the comet’s initial discovery on July 1, 2025, by the ATLAS system on Chile.

• Nucleus estimated between 0.32 km and 5.6 km in diameter, with a probability of less than 1 km.
• Current speed around 30 km/s, accelerating as it approaches Sol.
• Composition rich in carbon dioxide, methanol and cyanide, detected by missions such as James Webb.

3I/ATLAS should reach its closest point to Terra on December 19, 2025, 269 million kilometers away, without posing a risk of collision.

Initial observations and evolution of the coma

NASA and ESA astronomers have been coordinating efforts to monitor 3I/ATLAS since July. The first record of Hubble, on July 21, occurred 450 million kilometers away, showing a dust plume facing Sol.

This evolution reflects the heating of the core, which sublimates ice into gas and lifts particles. Dados preliminary data indicate the ejection of 6 kg of fine dust per second in July.

The coma, a gaseous envelope surrounding the nucleus, has visibly expanded in the recent image. Telescópios terrestrials on Havaí and Chile confirmed tail lengthening in August.

Contributions of the Juice probe to chemical data

ESA’s Juice probe observed 3I/ATLAS in November 2025 with five scientific instruments. The Essa mission, heading to the moons of Júpiter, captured images from 66 million kilometers away on November 2.

Details of the tails captured by Juice

Juice’s navigation camera recorded the coma and signs of two tails: one of plasma, opposite to Sol, and another of dust. Apesar Despite not being optimized for science, the image revealed post-perihelion activity.

Astronomers note that the probe’s proximity allowed a clear view of the structure. Complete Dados arrive in February 2026, due to the position of Juice behind Sol.

• Navigation camera: Resolução limited, but sufficient for tails.
• Scientific instruments: Análise of composition and movement.
• Distance: 66 million km, ideal for the active phase.

This contribution complements observations from other probes, such as Mars Express in October.

Juice travels at 30 km/s towards Júpiter, using the comet as an extra opportunity. Expected Resultados include gaseous emission spectra.

Other NASA missions that tracked 3I/ATLAS

Several NASA probes have incidentally recorded the comet in recent months. The Psyche mission, in September 2025, measured colors and light to refine the trajectory.

Multi-platform data integration

James Webb Space Telescope observed in August, detecting water ice, steam and carbon monoxide. Esses findings indicate a composition similar to solar comets, but with excess carbon dioxide.

The STEREO mission captured ultraviolet emissions in October, showing elongation of the tail. PUNCH, monitoring another comet, recorded 3I/ATLAS by chance in combined images.

• Psyche: Medições of color in September.
• James Webb: Espectro NIRSpec on August 6th.
• STEREO: Atividade solar and tail in October.

These platforms provide a 360-degree view of the object.

The Very Large Telescope detected cyanide and nickel vapor at typical concentrations. Hubble plans more ultraviolet spectroscopy in December.

Trajectory and composition reveal distant origins

3I/ATLAS remains hyperbolic, originating from another star system. Sua reddish color suggests irradiated organic compounds, such as tholins.

Spectral analysis and detected elements

Observations of Hubble in November focused on the sulfur-to-oxygen ratio in emissions. Grãos of 1 micrometer dust comes out at 22 m/s, while larger ones, 100 micrometers, at 2 m/s.

In August, the coma lengthened against Sol, with a fan-shaped plume. Pós-perihelion, the dust tail measures 50 arc seconds, or 100 thousand km.

This dynamic tests models of planetary formation. The comet preserves chemistry from remote galactic regions.

Astronomers predict increasing annual detections with telescopes like Vera C. Rubin. ESA’s Comet Interceptor mission plans to intercept similar comets.

Earth observations and current visibility

Amateur telescopes see 3I/ATLAS at Virgem and Leão. Magnitude 11.5 on December 6, 2025 allows detection with medium equipment.

Preparation for upcoming passage in December

On December 19, the comet reaches 1.8 astronomical units from Terra. Observatórios global intensifies tracking to refine orbit.

ESA and NASA maintain updates on dedicated websites. Juice and Hubble will continue monitoring until March 2026, when 3I/ATLAS will pass Júpiter at 0.357 AU.

These data support studies of small objects in Sistema Solar. The Interstellar Visitor offers lessons about star formation beyond our own.