There may be a large number of undetected giant planet-like bodies in the neighborhood of our Sun, according to a Carnegie-led team of astronomers from Canada, the United States and Chile. <\/p>\n
An artists conception of a free-floating planet-like object. Image credit: NASA \/ JPL. <\/p>\n
Similarly-aged stars moving through space together in a group are of great interest to astronomers, because they are considered a prime target to hunt for brown dwarfs and free-floating planetary-mass objects. <\/p>\n
Recent studies of the TW Hydrae (TWA) group have revealed some of the first known isolated giant planet-sized objects in the solar neighborhood, roughly 100 light-years away. This group contains a few dozen 10-million-year-old stars, all moving together through space. <\/p>\n
Two recent discoveries in particular demonstrate the interest of TWA as a laboratory for understanding this isolated planetary-mass population, said Carnegies astronomer Jonathan Gagn and co-authors. <\/p>\n
2MASS J11193254-1137466 and 2MASS J11472421-2040204 are both candidate members of TWA with spectral types L7 that display signs of youth, and with estimated masses as low as 5-7 Jupiter masses. Their close distances to the Sun place them at the nearer side of the TWA spatial distribution. <\/p>\n
In order to determine whether or not there are more stand-alone planetary mass-sized objects like these in TWA, the astronomers undertook the calculation of an astronomical measurement called the initial mass function. <\/p>\n
This function can be used to determine the distribution of mass in the group and to predict the number of undiscovered objects that might exist inside of it. <\/p>\n
The initial mass function of TWA had never been published before, Dr. Gagn noted. <\/p>\n
In the process of this analysis, the researchers were able to determine that there are probably many more objects 5-7 times the mass of Jupiter in the association that havent been discovered yet. <\/p>\n
A tentative overpopulation of isolated planetary-mass members similar to 2MASS J114724212040204 and 2MASS J111932541137466 is identified, they said. <\/p>\n
This indicates that there might be as many as 10+13-5 similar members of TWA with hot-start model-dependent masses estimated at 5-7 Jupiter masses, most of which would be too faint to be detected in the Two Micron All Sky Survey (2MASS). <\/p>\n
TWA extends out to a distance of 250 light-years, but our instruments arent sensitive enough yet to detect giant planets-like members at this distance, hence many of them might remain to be discovered, Dr. Gagn explained. <\/p>\n
The research is published in the Astrophysical Journal Supplement Series (arXiv.org preprint). <\/p>\n
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Jonathan Gagn et al. 2017. BANYAN. IX. The Initial Mass Function and Planetary-mass Object Space Density of the TW HYA Association. ApJS 228, 18; doi: 10.3847\/1538-4365\/228\/2\/18 <\/p>\n
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