Space and Astronomy News for the 3rd of July 2025

Another interstellar visitor to the Solar System - meet  A11pl3Z or Comet 3I/ATLAS

(I'm putting this blog entry up a couple of days early as there's been some breaking news astronomy news overnight.)

Observers using the ATLAS telescopes in Chile have observed a new object in the Solar System, called A11pl3Z for now, on the 1st of July 2025. It has been confirmed as a visitor from interstellar space.

Provisional naming also has this called 3I/ATLAS as it's highly likely to be a comet.

Once it was found, researchers were able to look at images from the 14th to the 21st of June 2025 and found it there as well. There's been over 100 other confirmed observations and this number is expected to grow dramatically. It is currently about as far out as Jupiter's orbit. You can find more information via the Minor Planet Center listing here 

The discovery of new bodies travelling around the Sun happen every day and the number of known objects in the Solar System grow by many thousands each year. This new observation is of something quite different. Rather than finding another member of the local family, A11pl3Z appears to have arrived at the Solar System from another star. It won't go into orbit around the Sun and will depart for interstellar space.  A11pl35Z / 3I/ATLAS is travelling at around 60 km per second or around 216,000 km per hour which means it's going too fast to be captured by the Sun's gravity.

A11pl3Z or 3I/ATLAS, as seen by Deep Random Survey, Chile. You can see it near the middle of the image moving compared to the background stars. Image via K Ly (astrafoxen)

This is also only the third* object from deep-space to visit the Solar System that we have found and quite different from the other two visitors from other stars we've seen previously. 

First of all, A11pl3Z won't hit Earth. 

"It will fly deep through the solar system, passing just inside the orbit of Mars." said Richard Moissl who is the European Space Agency's head of planetary defence. 

The predicted high-speed path of A11pl3Z through the inner Solar System. Image via Catalina Sky Survey

How big is this new object?

Current size estimates have it at 10-20 km wide. This figure is likely to be updated as more observations are made. Given its speed, location and recent discovery, there are no plans to send a space mission to intercept or observe it.  We simply don't have anything that would be able to catch it! There have been a number of proposals of how to intercept interstellar visitors such as this one from MIT, but none of these are likely to be built soon.

Can I see it with my telescope?

"It will get brighter and closer to the sun until late October and then still be observable (by telescope) until next year." Moissl added. 

However statements like these are about A11pl3Z   3I/ATLAS being visible in extremely large, professional telescopes located in major observatories. You won't be able to see or photograph it with your own telescope at this point. We will be publishing charts to show which region of the sky it's located in as it progresses through the Solar System.

Where did A11pl35Z 3I/ATLAS come from and has it encountered any stars previously? Where's it heading to next?

Good questions! We'll soon know more about what part of the Milky Way it arrived from as more is known about its path. It may have originated from a nearby star and had its orbit disturbed by another large planet or passing star, ejecting it from is host system. It might have also been travelling from a far more distant part of the Milky Way. Along the way if A11pl35Z encountered other stars, it might have even experienced in increase in speed as it "slingshotted" around them, much like we use gravity assisted flybys for space missions. 

What were the other two known visitors from interstellar space and is A11pl35Z different?

There's been two other confirmed interstellar objects. The first was ʻOumuamua (1I/2017 U1) which was found in 2017. This is quite a fascinating object and nothing like anything we've seen before or since. It was a reddish coloured body that seemed to be tumbling. It also appeared to be highly elongated, and accelerated slightly as it "left" the Solar System, likely due to outgassing or pressure from Solar radiation. It was travelling from the Sun's perspective at less than half the velocity of A11pl35z, although this speed almost matched the Local standard of Rest for this part of the Milky Way. In other words, from our home galaxy's point of view, it was keeping still while the Sun, the Earth and other parts of the Solar System passed by.  There's a LOT of things we don't know about ʻOumuamua and this will be a topic of research and discussion for some time.

Comet 2I/Borisov (C/2019 Q4) was found in 2019 by amateur astronomer and telescope maker, Gennadiy Borisov. Rather than being an exotic body like ʻOumuamua, Comet Barisov behaved like a fairly standard comet as it entered the Solar System from interstellar space. It's chemical composition was rare, but not unheard of. It disintegrated as it made its closest approach to the Sun as many comets do. 

A11pl3Z  / 3I/ATLAS appears to be a circular as there's no variations in brightness observed so far. This could change as it gets closer to the Sun. 

Are we going to find more interstellar visitors and why are the important?

With new, large survey telescopes becoming operational, it's highly likely we will discover more interstellar visitors. Many expect the Vera. C. Rubin Observatory which we talked about last weekend could find one new interstellar object per month.  Visitors like these, even though they might be beyond our capabilities to visit close up or land on for the foreseeable future, do allow us to observe chunks of other star systems in more detail than if they were orbiting their host stars light years away. They could help us learn more about exoplanet formation. We could also discover more about the conditions for life on other star systems if chemicals like amino acids are found as well.

Planetary astronomers David Jewitt and Darryl Z. Seligman modelled data in a 2023 study that proposed there could be as many as 10,000 interplanetary visitors passing through the Solar System at any one time. We've obviously got a lot more to find.

There's going to be a lot of news about this discovery in the coming days. I'll update this article as we know more. 

Gilmour Space Launch slips another week or so

We mentioned last week that Gilmour Space was planning to attempt a launch from their base in Bowen QLD of their Eris-1 spacecraft. This would be the first commercial launch of a mission into orbit from Australia.

This has now slipped another week or so, with a NET (No Earlier Than) date of July 16th 2025. You can stay up to date with their progress here.

Cheers,

Earl White 

BINTEL

3rd July 2025

PS: *Ok, so while I've said this is the third visitor to the Solar System, there have been a couple of other objects that are not fully accepted by the wider scientific community. This includes Interstellar meteor 1 (IM1) or CNEOS 2014-01-08 which is thought to have impacted off the coast of Papua New Guinea in early 2014.