近日，美国加州理工学院的Jerry W. Xuan及其研究团队取得一项新进展。经过不懈努力，他们发现低温褐矮星Gliese 229 B是一颗密近双星。相关研究成果已于2024年10月16日在国际权威学术期刊《自然》上发表。

该研究团队利用GRAVITY干涉仪和位于超大望远镜上的CRIRES+光谱仪分别对格利泽229B进行了观测。这两组观测结果均独立地将格利泽229B解析为两个组成部分，即格利泽229Ba和Bb，从而解决了理论与观测之间的矛盾。在2微米的波长下，这两个天体的流量比为0.47±0.03，质量分别为38.1±1.0和34.4±1.5个木星质量（MJup）。

它们以0.042天文单位（au）的半长轴每12.1天绕彼此旋转一周。格利泽229BaBb的发现，每个天体的质量仅比最重的行星大几倍，且两者之间的距离是地月距离的16倍，这引发了关于恒星周围紧密双星褐矮星形成和普遍性的新问题。

据悉，由于与巨型系外行星的相似性，恒星周围的褐矮星伴星为行星形成和演化的基本过程提供了洞见。根据它们的轨道，发现一些褐矮星伴星的质量超过了根据其亮度和主星年龄所作的理论预测。这要么意味着理论尚不完善，要么意味着这些天体并非单一实体。例如，它们可能是两个各自质量较小、本征亮度较低的褐矮星。其中最成问题的是格利泽229B，尽管其动力学质量测得为71.4±0.6个木星质量（M_Jup），但其亮度却比模型预测低了至少2到6倍。

附：英文原文

Title: The cool brown dwarf Gliese 229 B is a close binary

Author: Xuan, Jerry W., Mrand, A., Thompson, W., Zhang, Y., Lacour, S., Blakely, D., Mawet, D., Oppenheimer, R., Kammerer, J., Batygin, K., Sanghi, A., Wang, J., Ruffio, J.-B., Liu, M. C., Knutson, H., Brandner, W., Burgasser, A., Rickman, E., Bowens-Rubin, R., Salama, M., Balmer, W., Blunt, S., Bourdarot, G., Caselli, P., Chauvin, G., Davies, R., Drescher, A., Eckart, A., Eisenhauer, F., Fabricius, M., Feuchtgruber, H., Finger, G., Frster Schreiber, N. M., Garcia, P., Genzel, R., Gillessen, S., Grant, S., Hartl, M., Haumann, F., Henning, T., Hinkley, S., Hnig, S. F., Horrobin, M., Houll, M., Janson, M., Kervella, P., Kral, Q., Kreidberg, L., Le Bouquin, J.-B., Lutz, D., Mang, F., Marleau, G.-D., Millour, F., More, N., Nowak, M., Ott, T., Otten, G., Paumard, T., Rabien, S., Rau, C., Ribeiro, D. C., Sadun Bordoni, M., Sauter, J., Shangguan, J., Shimizu, T. T., Sykes, C., Soulain, A., Spezzano, S., Straubmeier, C., Stolker, T.

Issue&Volume: 2024-10-16

Abstract: Owing to their similarities with giant exoplanets, brown dwarf companions of stars provide insights into the fundamental processes of planet formation and evolution. From their orbits, several brown dwarf companions are found to be more massive than theoretical predictions given their luminosities and the ages of their host stars. Either the theory is incomplete or these objects are not single entities. For example, they could be two brown dwarfs each with a lower mass and intrinsic luminosity. The most problematic example is Gliese229B , which is at least 2–6 times less luminous than model predictions given its dynamical mass of 71.4±0.6 Jupiter masses (M_Jup) . We observed Gliese229B with the GRAVITY interferometer and, separately, the CRIRES+ spectrograph at the Very Large Telescope. Both sets of observations independently resolve Gliese229B into two components, Gliese229Ba and Bb, settling the conflict between theory and observations. The two objects have a flux ratio of 0.47±0.03 at a wavelength of 2μm and masses of 38.1±1.0 and 34.4±1.5M_Jup, respectively. They orbit each other every 12.1days with a semimajor axis of 0.042 astronomical units (au). The discovery of Gliese229BaBb, each only a few times more massive than the most massive planets, and separated by 16 times the Earth–moon distance, raises new questions about the formation and prevalence of tight binary brown dwarfs around stars.

DOI: 10.1038/s41586-024-08064-x

Source: https://www.nature.com/articles/s41586-024-08064-x