Hot Jupiters are rarely accompanied by other planets within a factor of a few in orbital distance .
Previously , only two such systems have been found .
Here , we report the discovery of a third system using data from the Transiting Exoplanet Survey Satellite ( TESS ) .
The host star , TOI-1130 , is an 11th magnitude K-dwarf in Gaia G band .
It has two transiting planets : a Neptune-sized planet ( 3.65 \pm 0.10 R _ { \earth } ) with a 4.1-day period , and a hot Jupiter ( 1.50 ^ { +0.27 } _ { -0.22 } R _ { J } ) with an 8.4-day period .
Precise radial-velocity observations show that the mass of the hot Jupiter is 0.974 ^ { +0.043 } _ { -0.044 } M _ { J } .
For the inner Neptune , the data provide only an upper limit on the mass of 0.17 M _ { J } ( 3 \sigma ) .
Nevertheless , we are confident the inner planet is real , based on follow-up ground-based photometry and adaptive optics imaging that rule out other plausible sources of the TESS transit signal .
The unusual planetary architecture of and the brightness of the host star make TOI-1130 a good test case for planet formation theories , and an attractive target for future spectroscopic observations .