Scholz's Star (WISE J072003.20−084651.2): a nearby binary that passed through the Oort cloud

Identification and orbit

Observations combining infrared detection, astrometry and spectroscopy established the system's trajectory. Backward projection of its motion suggests the system moved through the Solar System's outer reaches roughly 70,000 years ago, close enough to perturb comets in the distant Oort cloud. The motion also showed the object to be a binary, with a faint companion revealed by follow-up studies.

Physical characteristics

• Distance today: about 17–23 light‑years (roughly 5.1–7.2 parsecs) from the Sun.
• Location on the sky: in the southern constellation Monoceros, close to the Galactic plane and therefore projected against a relatively rich stellar background.
• Primary component: a very late M-type red dwarf with a mass near the hydrogen-burning limit—approximately 86±2 times the mass of Jupiter.
• Companion: a likely T-type brown dwarf (mid‑T spectral class) detected through its infrared signature.
• Combined system mass and brightness: total mass is modest (on the order of a few tenths of a solar mass, often quoted near 0.15 solar masses) and the pair is very faint, with an apparent visual magnitude around 18.3.

The primary lies close to the boundary between stars and brown dwarfs, so its properties have been of particular interest for studies of low-mass stellar evolution and the physics of atmospheres at the coolest stellar temperatures. Age estimates place the system at several billion years old, although uncertainties are large enough to allow a wide range (commonly cited values span a few to several billion years).

Close passage and implications

Reconstructing the past orbit of Scholz's Star indicates a flyby through the Oort cloud region. Such encounters are not extraordinarily rare: statistical studies suggest that stars on wide orbits approach or cross the Oort cloud on timescales of order 10^5 years. Because the Oort cloud lies tens of thousands of astronomical units from the Sun, a low-mass star can cross it without coming near the planets, but still gravitationally perturb cometary orbits. Any comets nudged inward by this event would take a long time—typically on the order of millions of years—to arrive in the inner Solar System, and there is no direct evidence linking this particular encounter to known cometary showers.

Scientific significance and future study

Scholz's Star illustrates how faint, low-mass objects discovered in modern infrared surveys can change our view of the local stellar neighborhood and its past interactions with the Solar System. Continued astrometric monitoring refines the system's motion and helps constrain encounter parameters, while spectroscopic study improves estimates of temperature, composition and age. The system remains a useful case study in the broader investigation of how passing stars influence comet reservoirs and long-term solar-system dynamics.

For further context and data resources see catalog entries and follow-up studies linked from survey pages and specialist literature (binary study, kinematic analysis, Oort cloud overviews and survey documentation: parallax reports, constellation mapping, catalog references, Galactic context, spectral types, mass scales, system mass estimates).