Localizing The First Interstellar Meteor With Seismometer Data
Amir Siraj · Abraham Loeb
Signals · 2023
Acoustic timing from a single seismometer (AU MANU) shrinks IM1's ocean search area from ~120 km² to ~16 km², a 7.5× improvement over DoD-provided coordinates.
Brief
Siraj & Loeb (2023) use the arrival time and peak amplitude of air-mediated sound waves recorded by the AU MANU seismometer, located 83.9 ± 0.7 km from the fireball, to constrain the 2014 interstellar meteor IM1 to a 16 km² zone off Papua New Guinea. The DoD's ~120 km² uncertainty box arose solely from rounding coordinates to the tenths place in latitude and longitude. The derived altitude of 16.9 ± 0.9 km and ram pressures up to 244 ± 27 MPa at the third lightcurve peak are consistent with prior DoD data. A second station, AU COEN, placed ~1,480 km away, independently corroborates the AU MANU constraint.
Metadata
- Category
- Phenomenon
- Venue
- Signals
- Type
- Peer-reviewed
- Year
- 2023
- Authors
- Amir Siraj, Abraham Loeb
- arXiv
- 2303.07357
- Access
- Open access
- Length
- 4 pages
- Programs
- Galileo Project, Breakthrough Prize Foundation
- Instruments
- AU MANU seismometer, AU COEN seismic station
- Data sources
- CNEOS catalog, DoD sensor reports, National Weather Service Global Ensemble Forecast System
- Tags
- interstellar-meteor, acoustic-localization, fireball, ocean-expedition, CNEOS, seismology
Key points
- Seismic acoustic timing reduces IM1's search footprint from ~120 km² to ~16 km², a factor of ~7.5 in area.p.3
- Sound signal first arrival: 270.5–271.5 s post-fireball; peak amplitude: 296–297 s post-fireball, these two constraints jointly solve for r = 83.9 ± 0.7 km and z = 16.9 ± 0.9 km.p.2
- Three lightcurve peaks correspond to altitudes 21.2 ± 0.9 km, 19.2 ± 0.9 km, and 16.9 ± 0.9 km, with ram pressures of 143 ± 16, 183 ± 21, and 244 ± 27 MPa respectively.p.2
- DoD coordinates are rounded to 0.1° increments, producing the original ~120 km² uncertainty box centered at (−1.3°, 147.6°).p.3
- AU COEN seismic station signal at 2014-01-08 18:23:53 implies a source distance of 1470–1490 km, fully consistent with the AU MANU solution.p.3
- IM1's direction of travel was perpendicular to the vector extending to AU MANU, eliminating x-y motion as a confound in acoustic timing.p.2
- Numerical reflection model (spherical blast wave re-radiating off ocean surface) confirms the r and z solution by reproducing the rise, peak, and tail of the second seismic packet.p.3
Verbatim
“We use data from a nearby seismometer to localize the fireball to a ∼ 16 km 2 region within the ∼ 120 km 2 zone allowed by the precision of the DoD-provided coordinates.”
p.1“The material strength of IM1 appears to be higher than all other 272 meteors in the CNEOS catalog (Siraj & Loeb 2022b).”
p.1“The locations reported by the DoD in the CNEOS catalog are rounded to the tenths place in longitude and latitude.”
p.3“The improved localization is of great importance for a forthcoming expedition to retrieve the meteor fragments.”
p.1
Most interesting
- The entire 7.5× search-area reduction was achieved using a single off-the-shelf seismometer 83.9 km away, no new instrumentation required.
- IM1's trajectory happened to run perpendicular to the AU MANU bearing, which simplified the acoustic geometry and made the solution cleaner than it would otherwise have been.
- The DoD's ~120 km² uncertainty box is an artifact of decimal rounding, not sensor precision, the underlying measurements are more accurate than the reported coordinates suggest.
- Ram pressures at the three burst peaks (143–244 MPa) are extraordinarily high; IM1's material strength already exceeded all 272 meteors in the CNEOS catalog in prior analysis.
- A station ~1,480 km away (AU COEN) provided an independent corroborating arc, meaning two geographically separated seismometers both point to the same 16 km² patch of ocean.