NASA interstellar comet 3I/ATLAS: new Hubble image, mission flybys, and what to watch next

Interstellar comet 3I/ATLAS is back in the spotlight this week as a fresh Hubble Space Telescope image, captured on November 30 and released in recent days, confirms the visitor’s post-perihelion activity and pins down its path through the inner solar system. The update matters because 3I/ATLAS—only the third confirmed interstellar object—offers a one-time laboratory for testing how “dirty snowballs” from another star behave, what they’re made of, and how their chemistry compares with comets born around the Sun.

3I/ATLAS at a glance: what’s new and what’s next

• Status: Interstellar comet (designation 3I/ATLAS, also known as C/2025 N1).

• Perihelion: October 29–30, 2025 (about 1.4 AU from the Sun, just inside Mars’ orbit).

• Distance now: Receding from the Sun; roughly hundreds of millions of kilometers from Earth.

• Closest approach to Earth: Expected around December 19, at a safe distance near 270 million km (≈170 million miles).

• Threat assessment: None—3I/ATLAS will remain far from Earth.

The new Hubble frame, taken after perihelion, shows a compact nucleus embedded in a soft, asymmetric coma with background stars streaked by Hubble’s tracking. The geometry and brightness confirm the comet’s activity remains robust even after its swing past the Sun.

Multiple “eyes” on an interstellar visitor

While Hubble provides the crispest resolved view from Earth’s neighborhood, NASA’s Psyche spacecraft has also contributed: earlier multispectral snapshots taken in September refined the trajectory and probed the faint coma. In Europe, ESA missions have teased additional glimpses—JUICE’s navigation camera, for instance, hinted at ongoing activity as the comet brightened this season. Combined, these vantage points let scientists compare how 3I/ATLAS looks from deep space and from Earth orbit, tightening orbit models and pointing ground-based telescopes to the right place at the right time.

What the brightness and “breath” of 3I/ATLAS tell us

3I/ATLAS has displayed a dynamic coma and evolving tail structures before and after perihelion, consistent with vigorous outgassing. Researchers track the comet’s “heartbeat” through repeated images: subtle brightening pulses, shifts in tail orientation, and jets that turn on and off as sunlight warms different patches of the surface. Early spectral analyses this fall emphasized a strong role for carbon-dioxide and other volatiles, a sign that portions of the nucleus may be mantled by fresh ices not yet baked by repeated solar passes—unsurprising for a first-time visitor from another star.

Why this matters: If the coma’s chemistry echoes what we see in long-period solar-system comets, it suggests broadly similar processes shaping icy bodies across planetary systems. If it differs—say, in the balance of CO₂, CO, water ice, or trace organics—it hints at distinct birth conditions around 3I/ATLAS’s original star. Either outcome is a win for comparative planetology.

Skywatching guide: how to try for 3I/ATLAS

3I/ATLAS will not become a naked-eye spectacle, but dedicated observers have a shot:

• When: The best opportunities cluster around mid-to-late December, with the comet highest in the pre-dawn sky.

• Where: Near Regulus in Leo as it arcs west to east before sunrise (check a current star chart for your location).

• Gear: A small telescope under dark skies is recommended; binocular visibility remains uncertain and will depend on local conditions and the comet’s day-to-day activity.

• Times: For convenient planning, aim roughly 4:00–6:00 a.m. ET in North America and 05:00–07:00 GMT in the UK, adjusting by latitude and date.

As always, visibility is “live”—the comet’s brightness can shift with outbursts, dust production, and viewing geometry, so observers should be flexible.

Science priorities now that perihelion has passed

With 3I/ATLAS receding from the Sun, teams are prioritizing:

1. Composition mapping: Narrowband imaging and spectroscopy to sample gas species (e.g., CO₂, CO, CN) and dust grain sizes.

2. Jet physics: High-cadence imaging to time rotational modulation—do certain jets repeat on a regular spin period?

3. Tail dynamics: Modeling ion and dust tails to back out the solar-wind conditions interacting with an interstellar coma.

4. Precision orbit work: Continued astrometry to refine the inbound/outbound hyperbolic trajectory, enabling better comparisons with 1I/ʻOumuamua and 2I/Borisov.

These efforts will help answer whether 3I/ATLAS is compositionally “ordinary” or an outlier among comets—and by extension, how typical other planetary nurseries might be.

Timeline: 3I/ATLAS milestones

• May–July 2025: Precovery and discovery images establish the object’s interstellar nature and 3I designation.

• July 2025: Early Hubble imaging captures a compact coma pre-perihelion.

• September 2025: Psyche’s multispectral imager records multiple looks from deep space.

• Oct 29–30, 2025: Perihelion at ~1.4 AU; activity peaks around solar passage.

• Nov 2025: Ground-based campaigns resume as the comet emerges into better morning geometry.

• Nov 30, 2025: Hubble reobserves 3I/ATLAS post-perihelion, confirming sustained activity.

• Mid–Late Dec 2025: Closest approach to Earth (~270 million km) and best amateur observing window.

NASA’s interstellar comet 3I/ATLAS

The latest Hubble image and ongoing cross-mission coverage cement 3I/ATLAS as a scientifically rich, safely distant traveler from another star. Over the next two weeks, expect a steady stream of measurements on its chemistry, jets, and tail. For skywatchers, the pre-dawn window around December 19 is the marquee target; for scientists, the data pouring in now will anchor comparisons with past interstellar visitors and sharpen our picture of how—and how often—planet-building ingredients are cooked across the galaxy.