As just the third known asteroid to enter our solar system from interstellar space, it should be expected that things aren’t going to proceed exactly according to predictions, but 3I/ATLAS has been beyond surprising in many ways.

Recently, the European Very Large Telescope used its Ultraviolet and Visual Echelle Spectrograph (UVES) to analyze the asteroid as it continues its journey toward the inner solar system. In a yet-to-be-peer-reviewed paper, astronomers found that this asteroid has far more nickel and iron in its gas plume than they ever would have predicted.

They explain why this is such a difficult situation to understand:

“At the distances at which comets are observed, the temperature is far too low to vaporize silicate, sulfide, and metallic grains that contain nickel and iron atom. Therefore, the presence of nickel and iron atoms in cometary coma is extremely puzzling.”

The analysis took place over the course of six data points, each one as the asteroid got closer. Of course, as the asteroid gets closer, it is also going to get warmer as it approaches the sun (though it is still very far away). They found that nickel was present on all of the readings that they took. Iron, on the other hand, only showed up on the points where the object was 2.64 astronomical units away (or closer).

How such an old and fast moving object could still have enough metal in it to eject is something of a mystery at this point. Proposals have been that it was a metal-rich object to begin with, or it has some chemical anomalies that cause it to create new metal.

The object is about the same distance from us as Mars is and getting closer. This is by far the largest interstellar object to have ever been studied. Astronomer Avi Loeb recently wrote a blog post about this, saying:

“In a recent paper, I derived that the diameter of 3I/ATLAS is larger than [3.1 miles] — the width of Manhattan Island. The first recognized interstellar object, 1I/`Oumuamua, was pancake-shaped and [360 feet] in diameter — the size of a football field. Why is the third interstellar object 3I/ATLAS a million times more massive than the first one?”

Having such a large object is interesting, but more importantly, should allow astronomers to get more information about it. A greater number of telescopes and other instruments will be able to spot the object as it approaches and eventually passes out of our solar system. This means far more data that can be analyzed.

Loeb has even proposed using NASA’s Mars Reconnaissance Orbiter to get an even closer look at the object, though as of now that has not been planned, and the window of opportunity for this will soon be closing.

For now, astronomers are using any tools that they have at their disposal to learn more about the object, and they continue to be surprised.

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