Astronomers using the Gemini North telescope at NSF’s International Gemini Observatory have captured 3I/ATLAS as it makes its temporary passage through our cosmic neighborhood.
This image from the Multi-Object Spectrograph (GMOS-N) at the Gemini North telescope shows the interstellar comet 3I/ATLAS. Image credit: International Gemini Observatory / NOIRLab / NSF / AURA / K. Meech, IfA & U. Hawaii / Jen Miller & Mahdi Zamani, NOIRLab.
Interstellar objects are objects that originate outside of, and are observed passing through, our Solar System.
Ranging from tens of meters to a few kilometers in size, these objects are pieces of cosmic debris leftover from the formation of their host star’s planetary systems.
As these remnants orbit their star, the gravity of nearby larger planets and passing nearby stars can launch them out of their home systems and into interstellar space, where they can cross paths with other solar systems.
Interstellar visitors are valuable objects to study since they offer a tangible connection to other star systems.
They carry information about the chemical elements that were present when and where they formed, which gives scientists insight into how planetary systems form at distant stars throughout our Milky Way Galaxy’s history — including stars that have since died out.
3I/ATLAS is only the third interstellar object ever discovered after 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019.
While astronomers think many interstellar objects exist, and likely pass through our Solar System on a regular basis, they are exceptionally difficult to capture since they are only visible when they’re close enough to see and when our telescopes are pointing in the right place at the right time.
Multiple teams around the globe are using a wide variety of telescopes to observe 3I/ATLAS during its temporary visit to our Solar System, allowing them to collectively determine some of the comet’s key characteristics.
Although much remains unknown, it is already clear that 3I/ATLAS is unique compared to 1I/ʻOumuamua and 2I/Borisov.
Observations so far suggest that 3I/ATLAS has an approximate diameter of at most 20 km (12 miles), compared to ‘Oumuamua’s diameter of 200 m and Borisov’s of less than one km.
The new comet also has an exceptionally eccentric orbit, where eccentricity describes how much an object’s orbital pathway is ‘stretched out.’
An eccentricity of 0 is a perfectly circular orbit, while an eccentricity of 0.999 is a very stretched-out ellipse.
An object with an eccentricity above 1 is on a path that does not loop back around the Sun, implying it comes from — and will return to — interstellar space.
3I/ATLAS has an eccentricity of 6.2, which is highly hyperbolic and ensures its classification as an interstellar object.
In comparison, ‘Oumuamua had an eccentricity of about 1.2, and Borisov about 3.6.
Right now, 3I/ATLAS is within Jupiter’s orbit at a distance of about 465 million km (290 million miles) from Earth and 600 million km (370 million miles) from the Sun.
The closest the comet will come to Earth is approximately 270 million km (170 million miles) on December 19, 2025, though it will pose no threat to the planet.
It will reach its closest approach to the Sun around October 30, 2025, at a distance of 210 million km (130 million miles) — just inside the orbit of Mars.
During this close approach, it will be traveling almost 25,000 km (15,500 miles) per hour.
The new image of 3I/ATLAS was captured by the Multi-Object Spectrograph (GMOS-N) at the Gemini North telescope.
“The sensitivity and scheduling agility of the International Gemini Observatory has provided critical early characterization of this interstellar wanderer,” said Martin Still, NSF program director for the International Gemini Observatory.
“We look forward to a bounty of new data and insights as this object warms itself on sunlight before continuing its cold, dark journey between the stars.”