Infrared telescopes might pick out a black-painted artificial object of sufficient size, since it would probably still radiating in the infrared relative to background. Assuming it’s big enough and close enough to register, and especially if it’s moving across the background. But the imagery may take literally months to be processed for that kind of detection to happen.
At 38,000 miles per hour, it took Voyager 2 about 12 years just to reach Neptune. That’s a long time to be couped up in a fighter jet sized container.
If it’s a functioning spacecraft, its IR signiture is going to be huge. All that electrical equipment generates a lot of excess heat. A ship the size of the Moon is going to need to be about half radiators just ot keep the temp down to something livable. And then painting it black means sunlight gets absorbed and reradiated as IR (there’s a reason most, if not all, spacecraft have highly reflective outer surfaces). If the Webb Telescope points at it, it’ll show up like a sore thumb, even if it’s in the outer system.
But it might avoid Webb, because that instrument has a fairly narrow field of view. But we got that covered too. Or will in a few years. The Nancy Grace Roman Space Telescope (formerly WFIRST) is a wide field IR survey instrument and should be launched within 5 years.
Anything that’s radiating in the near infrared is going to be too hot to be habitable for anything resembling humans.
That’s why they’re aliens!
Why do you think that means anything? V’ger was coasting, because we don’t have anything better. At one g constant acceleration it would take about a week.
Maybe it’s only the radiators that are that hot. They have really really good heat pumps.
Seriously, the Roman Space Telescope will also see in the visible and it has a primary mirror about the same size as Hubble. But it has, as its original name suggests, a wide field of view. It’ll be surveying the universe, so it’ll cover everything. Unless the aliens are hiding behind Uranus, a ship the size fo the moon should easily be visible to it and for that matter, other ground-based survey telescopes.
And no I don’t believe they’ll have painted their ship black. There’s a very good reason all spacecraft have highly reflective surfaces and those will apply to any aliens too. In this solar system, we obey the laws of thermodynamics.
A well-designed starship would have the habitable section thermally isolated from the hot parts. Any ship that is decelerating from interstellar speeds will be using astronomical amounts of power to do so; that is why most reasonable interstellar ship designs have vast radiators between the propulsion unit and the payload. The radiators wouldn’t be the brightest part of the ship however; the rocket itself would be far brighter, and pointed almost directly towards us.
All this assumes that the ship uses a reaction drive; but even a magical reactionless drive would surely consume energy and produce waste heat.
The most bizarre thing is that the drone explanation, which has now been readily accepted by the Navy, seems to be wrong in at least some of the clips associated with those articles. Analysis by Mick West and other contributors to Metabunk seems to show that one of the clips shows an ordinary aircraft seen at long range, which has been misidentified as a nearby drone, and another clip shows nothing but distorted but still identifiable stars.
This seems to suggest that the Navy are consistently incompetent at interpreting this data; I decline to accept the alternative hypothesis, that it is all deliberate misinformation, but YMMV.
Yeah but when you arrive at your destination you’re going too fast to do anything useful. You gotta turn around at the halfway point and decelerate the rest of the way. So two weeks.
Four weeks, actually. Which is still trivial for a civilization that can spend many years traveling between stars.
OK, so make the parts that face inwards mirror-polished, and just make sure that the mirrors are angled such that the Sun isn’t reflected to any of the planets in the system. Your radiator surfaces, of course, are pointing away from the Sun.
Just out of curiosity, is this a logistical debate or do you think we’ve been visited by aliens in airplane sized craft? Not a judgement, of course, because I certainly don’t know, it just extremely unlikely to my way of thinking.
I beg your pardon, my butt is not that big. 
No, I don’t. But arguing that aliens can’t have visited us because it takes years for us to travel Neptune is silly. If aliens are here, one would not be wrong in assuming they can go faster than 38K mph. And no one in their right mind, human or alien, is going to land a ship the size of a moon on Earth. (The sequel to Independence Day was stupid in that detail.) So, assuming no ST transporter tech, small landing craft make sense.
I don’t think ANY reported UFOs are aliens. Not a one. But I am on record here in my opinion that they aren’t all hoaxes either. I think there is some little-understood natural phenomenon or trick of human perception that presents in such a way as to have been interpreted as “UFOs”. (in the past, it was interpreted as ghosts, or angels, or demons, or bigfoot or swamp lights or whatever the then-current philosophy supports) The trouble is, you have the two sides, the true believers (they’re here!) and the hardcore skeptics (you’re all lying or crazy!) arguing past each other.
Someone needs to do a proper investigation, and Project Blue Book wasn’t it.
eta: the Navy videos are system anomalies.
With the caveat that “little-understood” means “little-understood by the people reporting the phenomena”, not necessarily “little-understood by the experts”. I mean, maybe the experts don’t understand it, either, but that’s not necessary to account for the puzzled observers.
Fair enough, however that wasn’t actually the crux of my argument, the conversation just kind of morphed there in a rather light-hearted way. To me, the biggest arguments against aliens having visited us has nothing to do with speed (although that’s certainly a biggie) but rather how they would have targeted us in the first place.
I think the problem with (most) believers is they believe their eyes. They generally refuse to think about the logistic of finding us or crossing the vast distances involved in getting here. When they do, they hand-wave it away with warp-drive, worm holes, gravity waves or the like.
As it happens I’ve been on a Drake/Fermi/are-we-alone? Podcast jag recently and I’m starting to come around to a Rare Earth Hypothesis point of view on the subject. I certainly don’t rule out other rocket building technologies, I just think they are a LOT more rare than Drake predicts.
I’m so glad I wasn’t the only person who remembered that scene.
It looks like a Cylon Baseship.
This might be an IMHO question, but I felt this thread seems like a good spot for it. How seriously should we take the House hearing, in which former military personnel are claiming knowledge of the US gov’t possessing actual evidence of “non-human biologics” from UFO crash sites. I would think that, if true, it would be much bigger news.