# Could we detect an alien starship entering Earth's Solar System? Or in it? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 21, 2008, 7:59pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840 "2008-08-21T19:59:22Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [August 21, 2008, 7:59pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/1 "2008-08-21T19:59:22Z")
Could we detect an alien starship entering Earth’s Solar System? We can discuss 3 kinds– [ol] [li]A slow ship, driven by nuclear explosions.[/li][li]A Bussard Ramjet, possibly multi-generational.[/li][li]An FTL vessel, using the disorted space bubble/wavefront warp theory.[/li][/ol] Assuming no cloaking/spoofing/stealth/ECM, which of these could we detect approaching our solar system? Which could we detect entering it? Which could we detect _inside_ the system, & how close? ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [August 21, 2008, 8:12pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/2 "2008-08-21T20:12:08Z")
I don’t see how we could detect any of those until it was within the moon’s orbit. I don’t care what its albedo is; any starship is likely to be far, far too small to be visible from Earth. Moreover, I can’t imagine the FTL ship being perceptible by any means to observers lacking FTL tech, at least nto while it’s using its hyperdrive. ---
**Author:** ![Zebra](https://avatars.discourse-cdn.com/v4/letter/z/c0e974/32.png) [@Zebra](https://boards.straightdope.com/u/Zebra)\ **Post date:** [August 21, 2008, 8:18pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/3 "2008-08-21T20:18:31Z")
If it gave off light it might be spotted. ---
**Author:** ![LiveOnAPlane](https://avatars.discourse-cdn.com/v4/letter/l/3d9bf3/32.png) [@LiveOnAPlane](https://boards.straightdope.com/u/LiveOnAPlane)\ **Post date:** [August 21, 2008, 10:21pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/4 "2008-08-21T22:21:57Z")
I think we might be able to detect scenario #1. What was the name of that, Daedaleus or something? If it was using the nukes to slow down, then they would be on our side of the shield/impact absorber, and we could maybe see the detonations. If there was nothing between us and them. If someone with a good telescope happened to be watching when one or two went off. At what range we could detect a nuclear dvice detonating, I have no idea, though I think it could be a ways out if we got lucky. ---
**Author:** ![Full\_Metal\_Lotus](https://avatars.discourse-cdn.com/v4/letter/f/df705f/32.png) [@Full\_Metal\_Lotus](https://boards.straightdope.com/u/Full_Metal_Lotus)\ **Post date:** [August 21, 2008, 11:43pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/5 "2008-08-21T23:43:34Z")
Just a WAG here, but supernovae are nopt detected visually much any more, but by the wave of high energy particles that they produce. I imagine that in scenario 1, the nuclear blasts, (and accompanying high energy particles) even at the limits of the solar system would be magnitudes “brighter” than those distant super novae. And noticed fairly quickly by the same instruments… As to the other two, I have no idea. FML ---
**Author:** ![The\_Vorlon](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@The\_Vorlon](https://boards.straightdope.com/u/The_Vorlon)\ **Post date:** [August 21, 2008, 11:52pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/6 "2008-08-21T23:52:41Z")
In case #1, I would think that the modern version of the Vela sats would go nuts at over a light year out. The rest depends on what hand waveing they use for a drive. ---
**Author:** ![OtakuLoki](https://avatars.discourse-cdn.com/v4/letter/o/ac8455/32.png) [@OtakuLoki](https://boards.straightdope.com/u/OtakuLoki)\ **Post date:** [August 22, 2008, 1:41am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/7 "2008-08-22T01:41:30Z")
I am of the opinion that either #1 or #2 could be very visible if they have to do (as seems likely) any kind of course correction, or deceleration, as they pass through the heliopause, for a rough guesstimate on range. I’m going to guess that both would be very “cometary” in their optical signature, and we usually pick up comets heading into our neighborhood while they’re still a ways out. As for #3 - without a reaction drive involved, I see no reason to assume that they’d be any more visible than an Icarus object of similar size. In which case it’s unlikely that we’d see them unless they were either effing huge, or they wanted to be seen. ---
**Author:** ![Clothahump](https://avatars.discourse-cdn.com/v4/letter/c/51bf81/32.png) [@Clothahump](https://boards.straightdope.com/u/Clothahump)\ **Post date:** [August 22, 2008, 2:12am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/8 "2008-08-22T02:12:32Z")
We haven’t yet. And they’ve probably been here and left a sign on the other side of the moon that reads “DANGER! QUARANTINE AREA!”. ---
**Author:** ![OtakuLoki](https://avatars.discourse-cdn.com/v4/letter/o/ac8455/32.png) [@OtakuLoki](https://boards.straightdope.com/u/OtakuLoki)\ **Post date:** [August 22, 2008, 2:13am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/9 "2008-08-22T02:13:54Z")
What? No “Hyperspace Bypass Coming Soon!” sign? ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [August 22, 2008, 4:05am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/10 "2008-08-22T04:05:44Z")
[QUOTE=Clothahump] left a sign on the other side of the moon that reads “DANGER! QUARANTINE AREA!”. [/QUOTE] I suspect it reads, “Tastes like chicken!” ---
**Author:** ![CutterJohn](https://avatars.discourse-cdn.com/v4/letter/c/91b2a8/32.png) [@CutterJohn](https://boards.straightdope.com/u/CutterJohn)\ **Post date:** [August 22, 2008, 6:46am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/11 "2008-08-22T06:46:47Z")
1 and 2 would be detectable. A new star that is quite explicitly blinking would be noticed readily. A constant thrust engine would be more difficult to spot though. However, depending on what speed these ships are going when they begin to slow down, they would build up what amounts to a sonic boom, only with light. A big ship with a big drive going a significant fraction of C before it begins to decelerate would be very obvious. If we were actively looking for intrusions, then there is no way they could get close without being spotted first. Disregarding sci fi gimmicks like cloaks, it is virtually impossible to hide in space for more than a short time. The only ways of doing it are hiding behind something larger than you, cooling the hull and storing the heat internally(obviously this can’t be kept up forever), or keeping the sun to your back. Oh, and the FTL ship would be undetectable, since we have no ftl sensors. It would show up on our doorstep completely unannounced, since they would be traveling faster than the EM radiation we would use to detect them(indeed… once they arrived we would have an interesting view of their ship flying _away_ from us.) ---
**Author:** ![SuntanTigerTamer](https://avatars.discourse-cdn.com/v4/letter/s/e5b9ba/32.png) [@SuntanTigerTamer](https://boards.straightdope.com/u/SuntanTigerTamer)\ **Post date:** [August 22, 2008, 8:24am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/12 "2008-08-22T08:24:13Z")
[QUOTE=carnivorousplant] I suspect it reads, “Tastes like chicken!” [/QUOTE] “Highly Probe-able Asses and Lack Basic Phaser Technology” ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [August 22, 2008, 8:43am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/13 "2008-08-22T08:43:31Z")
We could detect all of them if the aliens conveniently fitted them with transponders like those used on commercial aircraft. ---
**Author:** ![Walker\_in\_Eternity](https://avatars.discourse-cdn.com/v4/letter/w/46a35a/32.png) [@Walker\_in\_Eternity](https://boards.straightdope.com/u/Walker_in_Eternity)\ **Post date:** [August 22, 2008, 9:12am UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/14 "2008-08-22T09:12:09Z")
It’s possible that [LISA](http://lisa.nasa.gov/), when in place, could detect a ship travelling using type 3 drive. Although LISA isn’t in place yet, I think we have some ground based installations doing similar things (can’t remember the names off hand). As the distortion of spacetime caused by the drive is likely to be several orders of magnitude larger than that from distant black holes then we may be able to detect them with current technology. There are number of space based satelites that detect gamma ray bursts, these are likely to be able to detect the gamma rays from nuclear explosions. Not sure about the ramjet, I suspose it depends on how bright it is when it slows down coming into the solar system and if any one is looking in the right direction. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [August 22, 2008, 3:05pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/15 "2008-08-22T15:05:34Z")
[QUOTE=CutterJohn] The only ways of doing it are hiding behind something larger than you, cooling the hull and storing the heat internally(obviously this can’t be kept up forever), or keeping the sun to your back. [/QUOTE] If you only cared about hiding from one direction, you could radiate the heat away in the other direction, rather than having to store it. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [August 22, 2008, 3:38pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/16 "2008-08-22T15:38:46Z")
[QUOTE=CutterJohn] 1 and 2 would be detectable. A new star that is quite explicitly blinking would be noticed readily. A constant thrust engine would be more difficult to spot though. However, depending on what speed these ships are going when they begin to slow down, they would build up what amounts to a sonic boom, only with light. A big ship with a big drive going a significant fraction of C before it begins to decelerate would be very obvious. If we were actively looking for intrusions, then there is no way they could get close without being spotted first. Disregarding sci fi gimmicks like cloaks, it is virtually impossible to hide in space for more than a short time. The only ways of doing it are hiding behind something larger than you, cooling the hull and storing the heat internally(obviously this can’t be kept up forever), or keeping the sun to your back. [/QUOTE] What about a laser to dump heat in the form of light? If aimed away from the star, how could this be easily detected? > [@](#): > > Oh, and the FTL ship would be undetectable, since we have no ftl sensors. It would show up on our doorstep completely unannounced, since they would be traveling faster than the EM radiation we would use to detect them(indeed.. once they arrived we would have an interesting view of their ship flying _away_ from us.) Tachyons? We can detect those, somewhat. ---
**Author:** ![Full\_Metal\_Lotus](https://avatars.discourse-cdn.com/v4/letter/f/df705f/32.png) [@Full\_Metal\_Lotus](https://boards.straightdope.com/u/Full_Metal_Lotus)\ **Post date:** [August 22, 2008, 4:00pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/17 "2008-08-22T16:00:15Z")
What’s all this about “Earth’s Solar System”, you bipedal warm blooded thingy? This entire arm of the Galaxy is part of the Glorius Jhinsti Empire… Xarm Broodeater ---
**Author:** ![The\_Understander](https://avatars.discourse-cdn.com/v4/letter/t/3da27b/32.png) [@The\_Understander](https://boards.straightdope.com/u/The_Understander)\ **Post date:** [August 22, 2008, 4:38pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/18 "2008-08-22T16:38:17Z")
[QUOTE=Full Metal Lotus] What’s all this about “Earth’s Solar System”, you bipedal warm blooded thingy? This entire arm of the Galaxy is part of the Glorius Jhinsti Empire… Xarm Broodeater [/QUOTE] That may be, oh Imperial Alien Overlord… but at least _we’ve_ mastered spell-check. Earth 1, Jhinsties EL ZIPPO If you’re going to vaporize me, not in the face! Not in the face! ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [August 22, 2008, 4:54pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/19 "2008-08-22T16:54:08Z")
[QUOTE=Full Metal Lotus] What’s all this about “Earth’s Solar System”, you bipedal warm blooded thingy? This entire arm of the Galaxy is part of the Glorius Jhinsti Empire… Xarm Broodeater [/QUOTE] That’s all lies! The Jhinsti Empire does not exist, nor has it ever. Your puny planet is in no danger whatsoever. Ignore Xarm. He’s new here. Please resume your quaint human activities, like bowling, knitting, and searching your primitive information system for images of naked human specimens. No space defense mechanism is needed at this time. Oh, and can someone kindly point out where your leaders are? ---
**Author:** ![Tristan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tristan/32/18058_2.png) [@Tristan](https://boards.straightdope.com/u/Tristan)\ **Post date:** [August 22, 2008, 5:53pm UTC](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840/20 "2008-08-22T17:53:01Z")
LaRouche was right! /Homer [Next page](https://boards.straightdope.com/t/could-we-detect-an-alien-starship-entering-earths-solar-system-or-in-it/460840.md?page=2)