The story of “New Horizons” doesn’t end at Pluto. “New Horizons” will surely continue to do exciting research also after the close encounter with Pluto. The spacecraft has a limited amount of fuel remaining, enough to nudge it towards another one or two conveniently placed targets.
The best article summarizing the “New Horizons” mission I have found on Internet is “Beyond Pluto: New Horizons' Mission Is Not Over Yet” by Jonti Horner and Jonathan P. Marshall, first published on The Conversation, and re-published on IFLScience. The article ends with the diagram by NASA: New Horizons' will continue its mission after flying past Pluto, studying objects in the Edgeworth-Kuiper belt.
The article by IFLScience ends with these words:
“Since the launch of New Horizons, astronomers have been searching for suitable targets for it to visit as it hurtles outward through the Edgeworth-Kuiper belt, en-route to the stars. In October 2014, as a result of that search, three potential targets were identified. Follow up observations of those objects narrowed the list of possible destinations to two, known as 2014 MU69 (the favoured target) and 2014 PN70. The final decision on which target to aim for will be taken after New Horizons has left Pluto far behind, but we can expect to keep hearing about the spacecraft for years to come.”
I would like to propose here one much more exciting target for “New Horizons” to visit in coming one or two years. At the distance of about 10 AU behind Pluto's position in year 1989 we can imagine a cube of the cosmic space with an edge length of about 1 AU, a part of the Kuiper Belt, where the remnants of the Andrea star are to be expected. The debris do not belong to a “lost planet” of our Solar System, but to a brown dwarf, an original companion of the Proto-Sun, that was born together with our Sun more than 7 milliard years ago, and was damaged in a huge collision 3507 million years ago. Pluto, with its moons system, is the oldest known to us member of the debris cloud. It still circulates around the original center of mass of the Andrea star, in the distance of 10 AU, once in about 247.2 years, and simultaneously around the center of mass of the entire Solar System (including the Andrea star, of course), with exactly the same period. This double revolution is the reason, why the orbit of Pluto is inclined by about 17 degree to the ecliptic.
It can be simply explained, why we have not yet discovered the more of Andrea-star debris till now. First of all, we have not expected its existence. Therefore, we have also ignored (or misunderstood) the double-step structure of our present Solar System. The four terrestrial planets are twice as old, as the four gaseous giants; and our Moon too. Secondly, the remnants of the brown dwarf are mostly, like the cores of many comets, very dark, or even completely black; each of them could be really very cold and light. Thirdly, although their total mass has to be estimated at about 17 Jupiter masses, they distribution in the “debris cloud” can be imagined a single football located in a cube of space with an edge length of about 150 meters. Try to imagine a looking for a single football inside of an empty Olympic arena.
Let us calculate a little bit now. A diameter of the Pluto system, with its moons, is about 150.000 km. The unit 1 AU is about 150.000.000 km, one thousand times larger. Therefore inside of our imaginary cosmic cube, containing Andrea-star debris, we can contain one milliard Pluto systems. Pluto_mass (neglecting the mass of its moons) is about 1,3x1022kg, what is about 0,00218 Earth_mass. It means, inside our imaginary debris cloud, we have one milliard Pluto_mass or 2,2 million Earth_mass. Because Jupiter is 317 times as massive as the Earth, our imaginary cloud would contain about 7.000 Jupiter masses. It is definitively about one thousand times too much. Therefore, we can finally dilute the cloud density by the factor one thousand, what means a increasing of the edge length for every single Pluto system by a factor of ten. We can thus assume a single Pluto system inside of a cube with an edge length of 1.500.000 km (instead of previously chosen 150.000 km). At the end we obtain our debris cloud with its dimension of 1 AU, including the total mass of about 7 Jupiter_mass, if we imagine just a single Pluto system completely lost inside of its “own cube” with an edge length of 1,5 million km.
I hope for “New Horizons” that it has a better chance to meet Andrea-star debris than to find a single football inside of an empty Olympic arena. Good luck, “New Horizons”.