Specific allegation
Nemesis was proposed as a faint solar companion whose long orbit might perturb comets and periodically increase impacts. A stronger claim says a star is approaching now and is concealed. The proposal predicts a nearby gravitationally bound object, separate from debates over extinction periodicity.
Chronology and context
The idea emerged in the 1980s after suggestions that mass extinctions might recur on a roughly 26-million-year cycle. Later statistical analyses questioned that pattern. Infrared surveys improved detection of faint cool stars, but no coherent orbit or confirmed companion emerged.
Observations and physical record
A companion massive enough to disturb the Oort cloud would have infrared emission, proper motion, and gravitational effects. WISE performed an all-sky survey and astrometric catalogs track stars. No object with the required mass, distance, and orbit has been identified; the fossil record cannot substitute for observing the star.
Established scientific account
WISE constrains many nearby brown dwarfs and stars, while planetary and comet dynamics test the perturbation prediction. An object at a great distance might evade a particular survey, but would not match the classic nearby periodic companion. Extinction timing is uncertain and does not establish the missing body.
Limits and contrary evidence
No survey excludes every tiny body at every distance, and geological dating has finite precision. These limits leave open separate research questions, not evidence that Nemesis exists. A nearby stellar companion should be detectable across infrared and astrometric records, which presently show no matching source.
What could change the assessment
Require independent parallax, proper motion, spectral or thermal mass constraints, and a stable orbit that reproduces predicted comet perturbations. A statistical extinction cycle alone would not suffice. Survey limits and new astrometry can directly test the companion hypothesis.
The original motivation depended partly on whether extinction intervals were periodic, a statistical premise that later work disputed. Even if a periodic component were established, identifying a cause would still require a companion with measured parallax and orbit. Statistical pattern and physical object are separate links in the proposed chain.
Calibrated conclusion
The classic Nemesis companion is unsupported and strongly constrained by infrared and astrometric surveys.
Sources and scope
- WISE all-sky missionInfrared search directly constrains nearby cool objects.
- Luhman: WISE search for a solar companionPeer-reviewed null search within defined sensitivity.
- NASA Solar SystemOrbital context; overview is not a dedicated survey.