# SIMP J013656.5+093347

SIMP J013656.5+093347 (abbreviated SIMP0136) is a planetary mass object at 19.9 light-years from Earth in the constellation Pisces. It belongs to the spectral class T2.5 and its position shifts due to its proper motion annually by about 1.24 arcsec in the right ascension.

## Physical properties

In 2017, it was announced that the object's mass may be as low as 12.7 Jupiter masses and might be considered a rogue planet rather than a brown dwarf as it seems to be a member of the relatively young, 200 million-year-old Carina-Near stellar moving group.
In 2018, astronomers noted, "Detecting SIMP J01365663+0933473 with the VLA through its auroral radio emission, also means that we may have a new way of detecting exoplanets, including the elusive rogue ones not orbiting a parent star ... This particular object is exciting because studying its magnetic dynamo mechanisms can give us new insights on how the same type of mechanisms can operate in extrasolar planets – planets beyond our Solar System ... We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets." During the observation with the VLA only one pulse was detected for SIMP0136. The magnetic flux of SIMP0136 was estimated to be 3.2 kG.
In 2017 the rotational velocity and radial velocity was measured. It was found that we see SIMP0136 almost equator-on with an inclination of 80 ±12°.

### Weather and clouds

This brown dwarf provided the first evidence for periodic variability flux variations among T dwarfs. A team observed this object with the 1.8-m Perkins Telescope Observatory near Flagstaff, Arizona in 2015. SIMP0136 was observed in 15 nights, spread out over 90 days. The variation has been interpreted as a signature of weather patterns coming in and out of view over the object's 2.4h rotation period. The shape of this lightcurve evolves over timescales of days, which has been interpreted as a sign of evolution of the cloud patterns in its atmosphere. In 2016 a phase shift between Spitzer and Hubble observations was noticed, which was measured to be 33.4 ±3.9°. In 2023 a team found that SIMP0136 has patchy forsterite (Mg$_2$SiO$_4$) clouds above an iron cloud deck. This patchy cloud layer covers between 69% and 72% of the surface of the object. In 2024 a team re-analysed the 2015 data and detected a phase shift between the J-band and K$_s$-band of 39.9+3.6 −1.1°. The team concluded that the phase shift can be explained with at least two different patchy cloud layers. The J- and K$_s$-bands both probe different layers of the atmosphere. A study with JWST NIRSpec and MIRI observed two rotations and were used to study the object in detail. The study found that the variability comes from different parts of the atmosphere, depending on the wavelength. A signal deep within the atmosphere is thought to be connected to patchy iron clouds. Another signal higher up could come from patchy silicate clouds. A third signal comes from high above the clouds and is connected to hot spots, which could represent the aurora or upwelling of hot gas. Some of the light curves produced can only be explained with changing carbon chemistry.