New Interstellar Comet Incoming!

We are being visited by a comet from another solar system. Here’s why it’s historic and what to expect.

by Farmers' Almanac Staff Updated: July 3, 2025

New Interstellar Comet FAQ

Here are 10 frequently asked questions and answers about the comet, 3I/Atlas, discovered by NASA on July 1, 2025:

When is this new comet expected to be visible?

Current estimates suggest 3I/Atlas may be visible in October 2025. Could this be the next Halloween comet? Psst … read about last year’s.

What makes this comet special?

3I/Atlas is special because it is an interstellar object, meaning it is coming from outside our solar system. We only know of two other interstellar objects that have entered into our solar system before, ‘Oumuamua (2017) and Comet 2I/Borisov (2019).

**What is the difference between space and interstellar space?**

“Space” is a general term for the area beyond Earth and between celestial bodies, which begins at theKármán line, about 62 miles (100 km) above Earth’s surface. “Interstellar” refers to a region beyond our solar system, which begins at approximately 11.2 billion (18 billion) miles from the Sun.

Are comets usually from our solar system?

Yes, most of the comets that we observe originate from two places within our solar system: The Kuiper belt, a flat ring of icy bodies beyond the orbit of Neptune, and the Oort cloud, a much more distant cloud of icy objects that extends nearly halfway between Earth and the nearest star (Proxima Centauri).

Kuiper belt icy bodies in our solar system beyond the orbit of Neptune - a theorhetical rendering.

How big is 3I/Atlas?

Scientists are still investigating the brightness and size of 3I/Atlas. While some initial estimates suggest it might be quite large (up to 12-13 miles in diameter), the actual brightness will depend on its composition and how much volatile material it has. A larger comet has more material to sublimate, potentially making it brighter.

How far away is it?

CI/Atlas is currently approximately 420 million miles (670 million kilometers) away, according to NASA.

Which direction is it coming from?

CI/Atlas is currently coming from the direction of the constellation Sagittarius, which appears in the southern sky at midnight around this time of year (summer 2025) in the Northern Hemisphere.

Interstellar comet orbit rendering by NASA showing its trajectory.

Will 3I/Atlas become visible to the naked eye?

No, Astronomers do not expect 3I/ATLAS to be a naked-eye comet. It’s highly unlikely to become bright enough to be seen without a telescope.

Any questions? Let us know in the comments!

Are we sure 3I/Atlas is a comet?

Yes, the Minor Planet Center’s Electronic Circular from Wednesday, July 2, 2025 confirmed that 3I/Atlas is in fact a comet.

Why is it called 3I/Atlas?

The “3” represents the fact that it is the third interstellar object. The “I” stands for interstellar, describing its origin being from outside our solar system. “Atlas” is an acronym referring to the telescope network that discovered it: Asteroid Terrestrial-impact Last Alert System. So, when put together, “3I/ATLAS” literally means “the third interstellar object discovered, found by the ATLAS survey.”

Why are we seeing interstellar objects for the first time in the last decade?

The fact that scientists have confirmed three interstellar objects in less than a decade, after having zero confirmed detections for all of human history before 2017, is not due to a sudden increase in interstellar visitors. Instead, it’s primarily because of significant advancements in observational astronomy and data processing.