New Horizons in the Outer Solar System

A Closeup Look at NASA's Mission to Pluto and Beyond

An artist's idea of what New Horizons will look like as it flies by and studies Pluto and Charon in July, 2014. NASA

The outer solar system is the region of space beyond the planet Neptune, and the last frontier. The Voyager 1 and 2 spacecraft have passed beyond the orbit of Neptune, but have not encountered any more worlds.

That all changed with the New Horizons mission. The spacecraft spent 10 years flying out to Pluto, and then swept past the ​dwarf planet on July 14, 2015. It not only looked at Pluto and its five known moons, but the spacecraft's cameras mapped part of the surface.

Other instruments concentrated on finding out more about the atmosphere.

New Horizons mages show that Pluto has a complex surface with icy plains made of nitrogen ice, surrounded by jagged mountains consisting mostly of water ice. It turns out that Pluto was far more fascinating than anyone expected! 

Now that it has passed Pluto, New Horizons will explore the Kuiper Belt — a region of the solar system that stretches out beyond the planet Neptune and populated with so-called Kuiper Belt Objects (KBOs). The best-known KBOs are dwarf planets Pluto, Haumea, Makemake, Eris, and Haumea. The mission has been approved to visit another dwarf planet called 2014 MU69, and will sweep past it on January 1, 2018. Luckily, this little world lies right along the mission's flight path. 

In the far distant future, New Horizons will enter the fringes of the Oort Cloud (the shell of icy particles that surrounds the solar system, named for astronomer Jan Oort).

 After that, it will traverse space forever. 

New Horizons: Its Eyes and Ears​

New Horizons science instruments were designed to answer questions about Pluto, such as: what does its surface look like? What surface features does it have, such as impact craters or canyons, or mountains? What's in its atmosphere?

Let's take a look at the spacecraft and its specialized "eyes and ears" that have shown us so much about Pluto. 

Ralph: a high-resolution mapper with visible and infrared cameras to gather data that will help create very good maps of Pluto and Charon.

Alice: an imaging spectrometer sensitive to ultraviolet light, and built to probe Pluto’s atmosphere. A spectrometer separates light into its wavelengths, like a prism does. Alice works to produce an image of the target at each wavelength, and will be able to study the “airglow” at Pluto. Airglow happens when gases in the atmosphere are excited (heated). Alice will track light from a distant star or the Sun through Pluto’s atmosphere to pick out wavelengths of light absorbed by Pluto's air, which tells us what the atmosphere contains.

REX: short for "radio experiment." It contains sophisticated electronics and is part of the radio telecommunications system. It can measure the weak radio emission from Pluto, and take the temperature of its night side. 

LORRI: the Long Range Reconnaissance Imager,a telescope with a 8.2-inch (20.8-centimeter) aperture that focuses visible light onto a charge coupled device (CCD). Near the time of closest approach, LORRI was built to look at Pluto's surface at football-field size resolution.You can see some early images from LORRI here.

Pluto travels through the solar wind, a stream of charged particles sweeping out from the Sun. So, New Horizons has the Solar Wind Around Pluto (SWAP) detector to measure charged particles from the solar wind to determine whether Pluto has a magnetosphere (a zone of protection created by its magnetic field) and how fast the Plutonian atmosphere is escaping.

New Horizons has another plasma-sensing instrument called the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI). It will search for neutral atoms that escape Pluto's atmosphere and subsequently become charged by their interaction with the solar wind.

New Horizons involved college students from the University of Colorado as builders of the Venetia Burney Student Dust Counter, which counts and measures the sizes of dust particles in interplanetary space.