Young and directly imaged exoplanets offer critical tests of planet-formation models that are not matched by RV surveys of mature stars .
These targets have been extremely elusive to date , with no exoplanets younger than 10–20 Myr and only a handful of direct-imaged exoplanets at all ages .
We report the direct imaging discovery of a likely ( proto ) planet around the young ( \sim 2 Myr ) solar analog LkCa 15 , located inside a known gap in the protoplanetary disk ( a “ transitional disk ” ) .
Our observations use non-redundant aperture masking interferometry at 3 epochs to reveal a faint and relatively blue point source ( M _ { K ^ { \prime } } = 9.1 \pm 0.2 , K ^ { \prime } - L ^ { \prime } = 0.98 \pm 0.22 ) , flanked by approximately co-orbital emission that is red and resolved into at least two sources ( M _ { L ^ { \prime } } = 7.5 \pm 0.2 , K ^ { \prime } - L ^ { \prime } = 2.7 \pm 0.3 ; M _ { L ^ { \prime } } = 7.4 \pm 0.2 , K ^ { \prime } - L ^ { \prime } = 1.94 \pm 0.16 ) .
We propose that the most likely geometry consists of a newly-formed ( proto ) planet that is surrounded by dusty material .
The nominal estimated mass is \sim 6 M _ { Jup } according to the 1 Myr hot-start models .
However , we argue based on its luminosity , color , and the presence of circumplanetary material that the planet has likely been caught at its epoch of assembly , and hence this mass is an upper limit due to its extreme youth and flux contributed by accretion .
The projected separations ( 71.9 \pm 1.6 mas , 100.7 \pm 1.9 mas , and 88.2 \pm 1.8 mas ) and deprojected orbital radii ( 16 , 21 , and 19 AU ) correspond to the center of the disk gap , but are too close to the primary star for a circular orbit to account for the observed inner edge of the outer disk , so an alternate explanation ( i.e. , additional planets or an eccentric orbit ) is likely required .
This discovery is the first direct evidence that at least some transitional disks do indeed host newly-formed ( or forming ) exoplanetary systems , and the observed properties provide crucial insight into the gas giant formation process .