Inner Oort Cloud objects ( IOCs ) are Trans-Plutonian for their entire orbits .
They are beyond the strong gravitational influences of the known planets yet close enough to the Sun that outside forces are minimal .
Here we report the discovery of the third known IOC after Sedna and 2012 VP113 , called 2015 TG387 .
2015 TG387 has a perihelion of 65 \pm 1 au and semi-major axis of 1170 \pm 70 au .
The longitude of perihelion angle , \bar { \omega } , for 2015 TG387 is between that of Sedna and 2012 VP113 , and thus similar to the main group of clustered extreme trans-Neptunian objects ( ETNOs ) , which may be shepherded into similar orbital angles by an unknown massive distant planet , called Planet X or Planet Nine .
2015 TG387 ’ s orbit is stable over the age of the solar system from the known planets and Galactic tide .
When including outside stellar encounters over 4 Gyrs , 2015 TG387 ’ s orbit is usually stable , but its dynamical evolution depends on the stellar encounter scenarios used .
Surprisingly , when including a massive Planet X beyond a few hundred au on an eccentric orbit that is anti-aligned in longitude of perihelion with most of the known ETNOs , we find 2015 TG387 is typically stable for Planet X orbits that render the other ETNOs stable as well .
Notably , 2015 TG387 ’ s argument of perihelion is constrained and its longitude of perihelion librates about 180 degs from Planet X ’ s longitude of perihelion , keeping 2015 TG387 anti-aligned with Planet X over the age of the solar system .
We find a power law slope near 3 for the semi-major axis distribution of IOCs , meaning there are many more high than low semi-major axis IOCs .
There are about 2 million IOCs larger than 40 km , giving a mass of 10 ^ { 22 } kg .
The IOCs inclination distribution is similar to the scattered disk , with an average inclination of 19 degs .