# Red giant J0008+0128 has an invisible companion of 1.8–2.8 solar masses, possibly a neutron star

- Published: 2026-11-13 06:32 UTC
- Section: Sky & Space › Astronomy
- Tags: supermassive neutron star, J0008+0128, invisible companion, red giant binary, low-mass black hole, Science Advances, LAMOST APOGEE Gaia, Keplerian orbit
- URL: https://realtech.media/news/rt-74bf7dc73b2fde1499de507a_red_giant_j0008/

**Astronomers measured the orbit of a red giant in a wide binary and found an unseen companion that may be a supermassive neutron star or a low-mass black hole.**

![Red giant J0008+0128 has an invisible companion of 1.8–2.8 solar masses, possibly a neutron star](https://realtech.media/media/2026/11/3d0ab731c2c2afbb.jpg)
*Наука 2.0*

A team of astronomers reported in Science Advances a wide binary system, J0008+0128, in the constellation Pisces, about 4.8 thousand light-years from Earth. It consists of a red giant and an invisible companion. The mass of the companion lies in the range of 1.8 to 2.8 solar masses, with a best-fit value of 2.20 (+0.14, −0.13) solar masses [1].

The system was identified in data from the LAMOST telescope and the APOGEE project, together with data from the Gaia observatory.

## Orbit and mass of the companion

The authors combined radial velocity measurements from LAMOST and APOGEE with astrometric data from the Gaia DR2 and DR3 catalogs and derived a Keplerian orbit [1]. The orbital period is about 1218 ± 3 days, the eccentricity is about 0.09 ± 0.01, and the inclination is about 73° ± 11° (1σ uncertainty) [1].

Spectral disentangling of high-resolution near-infrared APOGEE spectra showed no absorption features from an additional component. According to the authors, this suggests a compact object: either a supermassive neutron star or a low-mass black hole [1]. The mass potentially places the companion within the gap between neutron stars and black holes. For comparison, most neutron stars weigh about 1.4 solar masses.

## Why the origin is unclear

The authors note that such a wide, low-eccentricity orbit is difficult to explain through standard binary evolution channels, and that improved theoretical models are needed [1].

Astronomer Scott Ransom of the National Radio Astronomy Observatory said the stars are too far apart for matter to have ever flowed from the red giant onto the companion. In his view, two options remain: neutron stars can be considerably more massive than assumed, or the supernova that produced the object followed a merger of two white dwarfs. He also allowed that the companion could be a pair of neutron stars or a neutron star with a white dwarf.

Ransom added that a nearly circular orbit may point to a black hole rather than a neutron star, since the birth of a black hole is thought to be calmer. He considers it unlikely that radio pulsations will be detected, because the object has already been observed with the best radio telescopes, so its nature may remain unconfirmed.

## Sources

1. [Science Advances](https://doi.org/10.1126/sciadv.aeg3307)
2. [Наука 2.0](https://naukatv.ru/news/nevidimyj_obekt_v_kosmose_mozhet_byt_sverkhmassivnoj_nejtronnoj_zvezdoj_astrofiziki)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-74bf7dc73b2fde1499de507a_red_giant_j0008/