# On the Existence of Interstellar Meteoroids

A meteoroid in orbit around the Sun has a heliocentric velocity in the vicinity of Earth of about 42.1 km/s. So if a meteoroid has a heliocentric velocity exceeding that, it will have an open (hyperbolic) orbit and would not have originated in the solar system. As a meteoroid encounters Earth's atmosphere it encounters atmospheric atoms and molecules, generating heat that causes atoms to boil off and collide with those in the atmosphere. This produces ionized particles which surround the meteoroid with a glowing envelope leaving a column of plasma. The meteoroid is now seen as a meteor.

Meteor velocities measured by radar and optical means have indicated the detection of many hyperbolic meteoroid orbits (heliocentric velocities exceeding 42.1 km/s), but velocity measurement errors which occur in the 10% range have cast doubt on their interstellar meteoroid status. However, it's clear that the solar system must be embedded in dusts and gasses originating from nearby star systems, so the existence of hyperbolic meteoroids should not be in doubt.

What is the technical difficulty in obtaining sufficiently accurate velocity measurements to prove or disprove the existence of interstellar meteors?

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Microlensing MACHO searches make it very clear that there are many sub-stellar heavy bodies out between the stars, and I don't know of anyone who doubts that there are light objects out there too, it just that Douglas Adams was going down the right road with his "Space is big..." line. –  dmckee Jun 13 '12 at 1:41

Sure. If only because the mean time between encounters goes by $1/v$ most of the extrasolar material will be coming in pretty fast. –  dmckee Jun 13 '12 at 16:43