Comet 3I/ATLAS: Move along. Nothing to see here.

Despite all the sensational headlines you may read on the internet, Comet 3I/ATLAS remains an unremarkable object in the morning sky. My animated GIF above, taken on December 9th, shows a tiny little comet-like object moving past a background star over a period of about 7 minutes. The planetarium software that I use, Cartes du Ciel, indicated that 3I/ATLAS was around 15th magnitude. I think it looks a little brighter than that, but I have to admit that whatever its official magnitude is, 3I/ATLAS is getting a lot more attention and hype than it deserves!

I didn't go to the trouble of converting pixel counts to stellar magnitudes, but the line graph feature in MaxIM DL CCD software shows that the brightness of 3I/ATLAS maxes out at around 9,100 counts. My camera has a 16-bit digitizer, so the display range for each pixel is from 0 to 65,535, with 0 representing black and 65,535 representing white. In a 15-second exposure, the brightest pixels in 3I/ATLAS are only 14% of full pixel brightness.

By comparison, the 9th magnitude star (BD+04 2476) below 3I/ATLAS in my image doesn't appear very bright, but a line graph reveals that the brightest pixels reach saturation, or max pixel counts of 65,535. Notice that the top of the peak in the graph is flattened off. Thus, you could say that my camera reaches saturation on 9th magnitude stars in less than 15 seconds.

Converting pixel counts to stellar magnitudes is far too complicated for me to do! It requires calibrating the camera using standard stars and standardized photometric filters (which I don't have). But if a 15-second exposure maxes out a 9th magnitude star and leaves the comet at 14% of saturation, then the comet must be quite a lot dimmer than 9th magnitude (which is the very dimmest star you can see through a pair of 8 x 42 binoculars under a very dark sky).

Keep in mind, we're talking about a comet that has already reached its closest point to the sun. In a few days, earth will reach its closest distance to the fleeing comet. Closest approach should be an optimal viewing situation. But yet, the comet is too dim to be seen through a pair of ordinary binoculars. 

That's an unremarkable comet, indeed!

Our solar system has been visited by, as far as we know, three objects that came from interstellar space. The first one caught us quite by surprise. But then when the second interstellar object appeared, we had to get spammed by Avi Loeb who claimed 'Oumuamua was an alien space probe of some sort. But 'Oumuamua left the solar system without leaving any evidence of aliens. And when 3I/ATLAS was found to be interstellar, Avi Loeb had to come back and play the same old game: "It's aliens, folks!"

Nonsense!

Why can't we just enjoy and appreciate 3I/ATLAS for what it is? An interstellar object that has journeyed from afar and is passing through our solar system. It has zero chance of colliding with earth (no matter what the online news media is saying). In fact, it is going to miss us by 167 million miles (nearly twice the earth-sun distance)! It may not look exactly like the comets in our own solar system, but we know from past comets (even Oort Cloud comets in our own solar system) that sometimes an object gets kicked out of its home solar system and wanders out through interstellar space. This happens through natural forces and doesn't require us to invoke aliens to explain it.

UPDATE:

My image from 3 o'clock this morning (December 14) shows that the comet is dimming as earth approaches it. The max counts on my 15-second exposures were less than 7,000, down more than 2,000 counts from the night before. 

In my original post, I compared the comet to magnitude 9.1 star. In 15 seconds, the star saturated and the brightest pixels were cut off at 65,535 pixel counts. This morning's image showed a nearby 10.4 magnitude star (BD+05 2449). This star also saturated in a 15-second exposure. The brightest pixels in the comet, by comparison reached only 10% of saturation (down from 14% the night before).

The point I wish to make with these image comparisons is that Comet 3I/ATLAS is behaving like a comet! Sure. I'm not using spectroscopy, so by "behaving like a comet," I'm merely stating that from my own images, the comet is not acting chaotic or extraordinary compared to other comets I've imaged.

You will recall that JPL's orbital view of 3I/ATLAS at closest approach (see below) shows that the comet is leaving the solar system as the earth comes around toward it from 167,000,000 miles away. This places a disappointing twist on "close approach". The hyped-up media headlines that say 3I/ATLAS is "coming toward us" or, in extreme cases, "going to impact earth" are, in fact, total lies!

To put this "close approach" in the proper perspective, let's imagine two cars driving along two roads. The first car (let's call it 3I/ATLAS) is traveling northbound on a road that intersects with a side street at a T-intersection. The second car (let's call it Earth) is heading westbound on the side street, approaching the intersection. Even though the cars are traveling at right angles relative to one another, they are technically getting closer together as they approach the intersection. If the timing is just right, and if Earth runs the stop sign at the intersection, then 3I/ATLAS could possibly T-bone Earth. In this scenario, closest approach becomes an impact event. 

But this hypothetical collision is not even a remote possibility with the real 3I/ATLAS and the real earth. That is because, for one thing, the space roads upon which these two bodies are traveling do not, in fact, intersect! There is no possibility that the comet can impact the earth, because earth's orbit curves away from the comet's path. And for another thing, 3I/ATLAS has already passed through the hypothetical intersection! So even if earth could somehow run the proverbial stop sign, 3I/ATLAS is long gone!  

As far as visual observations and impressions of 3I/ATLAS as it heads outbound toward Jupiter, there are three important facts to consider here: First, 3I/ATLAS didn't get very close to the sun at its closest point. It was more distant from the sun than the earth is, which means that it didn't experience the extreme intensity of solar radiation that other comets achieve by being inside the orbits of Venus or Mercury at closest approach. This explains why, as comets go, 3I/ATLAS is an underperformer.

Secondly, as an interstellar object, it is moving much faster than normal comets, and also, it's on a much straighter outbound path, so it is moving away from the sun more directly than other comets. Thus, after closest approach to the sun, it is receding faster from intense solar radiation, and its surface is icing over again much faster than normal comets. 

This is why, despite being an interstellar object, it is performing rather like we can expect of a comet or similar natural object. Outgassing activity is slowing much more rapidly than typical comets, which, in turn, causes 3I/ATLAS to grower dimmer faster than normal comets (due to the reasons described above). But it is still behaving more or less like a comet than it is like an artificial spacecraft.

For anyone wanting to believe that 3I/ATLAS is a spacecraft, the first thing they need to explain is why it looks like a comet. Why would, and how could, aliens launch such a huge and massive craft to escape their own star's gravity, with so much apparent excess and unnecessary material that would shed away and produce a large coma and tail as at it approaches a star? 

Some have even suggested that 3I/ATLAS is, in fact, a comet, but that aliens somehow hitched a ride on it. That is the most foolish idea ever! Just ask Philae about its experience landing on Comet 67/P. In addition to having very little control of your interstellar destination on such a haphazard mission, there is no way to predict a "safe spot" to perch a spacecraft on a comet, such that if and when the comet approaches a star, its violent outgassing won't jettison away the hitchhiker with the rest of the debris. 

Remember, too, that this probably isn't 3I/ATLAS's first rodeo. Astronomers believe that 3I/ATLAS may have passed close to as many as 25 stars on its journey across the galaxy. That's a lot of outgassing events for a surface rider to overcome!

The long journey of perhaps several billions of years leads to the second thing necessary to be explained by those who believe in the alien theory of 3I/ATLAS: Why would aliens so far away from us launch a craft to gather information about or perhaps even go to battle with denizens of our solar system? The hypothetical species that sent this spacecraft would be likely extinct before it reached us. Not to mention that 3I/ATLAS may have begun its voyage through the stars long before our sun and its family of planets came into existence.