Evidence for ET?

[Anomalocaris]

Surprise! Other things aren't traveling at our speed.

I disagree.  It seems to me that based on our current knowledge, we should expect extra-solar object ejected from other star systems to commonly possess low relative velocities to local standard of rest.

Here in our solar system a major means to eject an object formed around the sun from the sun’s gravitational influence is through close gravitational interaction between the object and a gas giant, primarily Jupiter, after the object has been initially perturbed into a gas giant crossing elliptical orbit.  A number of comets that have been observed to follow hyperbolic heliocentric trajectories (e>1) due to encounters with Jupiter and Saturn. Although Jupiter’s gravity is powerful enough to slingshot small objects approaching with appropriate encounter geometry to solar escape velocity, it is not powerful enough to do this with any significant margin to spare (e>1, but just barely).   This means as these object follow their Jupiter given escape trajectories, the sun would claw back almost all the extra heliocentric orbital energy imparted by Jupiter before the object can finally escape the sun’s gravity well for good.   So the object will leave with almost zero surplus kinetic energy, and thus very minimal relative velocity with respect to the sun.   So these objects will end up more or less fly in lose formation with the sun in their independent orbits around the Milky Way rather than just zip off at high speed in random directions never to be seen again.

I believe numerical simulation has shown that for a Star such as the sun, it is not difficult to come up with combinations of mass and orbits of gas giant planets that would enable the gas giant to pump other objects in the system up to stellar escape velocity.  But it is much more difficult to come up with plausible combinations of mass and orbits that would enable the gas giant to impart a large amount of surplus kinetic energy to a small object in system beyond what is needed to escape.  So objects thrown out with very little surplus energy should be common.  Objects thrown out with lots of surplus energy sufficient to support galactic orbital vectors substantially different from the parent star would be comparatively uncommon.

The local standard of rest is nothing more than the average velocity of the stars in the broad galactic neighborhood around the sun.  If the escape mechanism powered by a massive planet deep in a star’s gravity well is typical of the star systems in the sun’s neighborhood, then we would expect many of the ejected objects from these systems would end up with very little relative motion to their parent systems.   In other words, we would expect the mean velocity of these interstallar objects to be essentially the same as the local standard of rest.

Just one problem. Almost nothing moves at LSR. There are a couple of different populations of stars moving at different speeds, so almost nothing is going the mean velocity. The Sun is moving something like 10 km/s relative to the LSR, so you'd need a hefty bit of delta-v to leave the solar system with a low velocity relative to LSR. Ditto for most other stars and a complete non-starter for low-metallicity stars, which are really moving. And then you have those weirdoes in retrograde orbits...

So finding an object at low velocity relative to the LSR is odd.

Actually, I believe the sun is moving at something like 20-40 km/s relative to LSR.  There are many individual or collections of stars that move at much higher delta V to LSR than the sun, but I believe the majority move at substantially lower delta V to LSR than the sun. So it should not be surprising that if ejection by close in gas giant is an important mechanism for stocking interstellar space with asteroid/comet like objects, than a sizeable fraction would move with the LSR.

If an object just barely escape the solar system, it would approach majority of local stars at initial relative velocities similar to that which Omaouaoua possessed relative to the sun before her trip into the solar system.