First ever probable discovery of moon out of the solar system

Many exoplanets may have moons orbiting them.  (Credit: NASA/JPL-Caltech)
Many exoplanets may have moons orbiting them. (Credit: NASA/JPL-Caltech)

Main Point:

Astronomers have probably found the first exomoon located about 1800 light years away from us.

Published in:


Study Further:


An exoplanet is the planet that is rotating a star outside of our solar system. Similarly, exomoon is the moon that orbits a planet outside of our solar system.


When an object moves in front of a remote star from Earth, the object’s gravity bends the light coming from the star in the background, presenting it like a lens, and temporarily increases the brightness of the star, if looked from a specific angle. This process is microlensing and is used to study the objects that emit little or no light.

Gravitational microlensing - A Horseshoe Einstein Ring from Hubble (Image Credit: ESA/Hubble & NASA)
Gravitational microlensing – A Horseshoe Einstein Ring from Hubble (Image Credit: ESA/Hubble & NASA)

Present Study:

In the present study, astronomers found a microlensing event in 2011 with the help of different telescopes from around the world. They found the differences in brightness of a star’s light. The light first increased 70 times in brightness and after one hour another smaller increase in brightness was observed.

This change in brightness (for two times) showed that there were two celestial objects that passed closed to that star but scientists are still unclear whether these two objects were a planet and its moon moving relatively near to our solar system, i.e. about 1800 light years away, or a pair of a very small or failed star and a Neptune-mass planet moving relatively farther from solar system.

“The data are well fit by this exomoon model, but an alternate star+planet model fits the data almost as well,” Scientists wrote.

If the smaller object is the exomoon, it would be the first moon ever found in history outside of our solar system. Astronomers have reported that the planet is about four times the mass of Jupiter and the moon is about half the mass of Earth.


D. P. Bennett, V. Batista, I. A. Bond, C. S. Bennett, D. Suzuki, J. -P. Beaulieu, A. Udalski, J. Donatowicz, F. Abe, C. S. Botzler, M. Freeman, D. Fukunaga, A. Fukui, Y. Itow, N. Koshimoto, C. H. Ling, K. Masuda, Y. Matsubara, Y. Muraki, S. Namba, K. Ohnishi, N. J. Rattenbury, To. Saito, D. J. Sullivan, T. Sumi, W. L. Sweatman, P. J. Tristram, N. Tsurumi, K. Wada, P. C. M. Yock, M. D. Albrow, E. Bachelet, S. Brillant, J. A. R. Caldwell, A. Cassan, A. A. Cole, E. Corrales, C. Coutures, S. Dieters, D. Dominis Prester, P. Fouque, J. Greenhill, K. Horne, J. -R. Koo, D. Kubas, J. -B. Marquette, R. Martin, J. W. Menzies, K. C. Sahu, J. Wambsganss, A. Williams, M. Zub J. Y. Choi, D. L. DePoy, Subo Dong, B. S. Gaudi, A. Gould, C. Han, C. B. Henderson, D. McGregor, C. -U. Lee, R. W. Pogge, I. -G. Shin, J. C. Yee, M. K. Szymaski, J. Skowron, R. Poleski, S. Kozowski, L. Wyrzykowski, M. Kubiak, P. Pietrukowicz, G. Pietrzyski, I. Soszyski, K. Ulaczyk, Y. Tsapras, R. A. Street, M. Dominik, D. M. Bramich, P. Browne, M. Hundertmark, N. Kains, C. Snodgrass, I. A. Steele, I. Dekany, O. A. Gonzalez, D. Heyrovsky, R. Kandori, E. Kerins, P. W. Lucas, D. Minniti, T. Nagayama, M. Rejkuba, A. C. Robin, & R. Saito (2013). A Sub-Earth-Mass Moon Orbiting a Gas Giant Primary or a High Velocity Planetary System in the Galactic Bulge arXiv arXiv: 1312.3951v1

Usman Zafar Paracha

Usman Zafar Paracha is Assistant Professor, Pharmaceutics, in Hajvery University, Lahore, Pakistan.