Moving Toward the Next Kuiper Belt Target

Today we got another green light signal from the New Horizons spacecraft. It’s on the way to its second target in the Kuiper Belt, an odd little place called Ultima Thule. A green light means all the boards are good, the mission is still a “go” and the spacecraft is doing its thing.

Kuiper Belt History

Back when I was in graduate school (SO last century!) the Kuiper Belt was just really beginning to be observed by such astronomers as David Jewitt, colleague Jane Luu, self-described “Pluto Killer” Mike Brown, and many others. It was given the name Edgeworth-Kuiper Belt after two planetary astronomers Ken Edgeworth and Gerard Kuiper. They theorized the existence of a region in the outer solar system populated by “leftovers” such as ice-rock worlds and cometary nuclei. In 1987, Jewitt and Luu began looking for such objects and began finding them.

Since that time, others have been found, dubbed KBOs (for “Kuiper Belt Objects”), “Kuiperoids” and “trans-Neptunian Objects”. It happens to be home of Pluto, as well as the dwarf planets Eris, Haumea, Makemake, and Sedna. Ceres, which is also a dwarf planet “lives” in the Asteroid Belt. There are other worlds “out there”. Some are candidates to be defined as dwarf planets at some point. Yet, there are probably many more that haven’t yet been detected. All in all, the Kuiper Belt is a rich treasury of worlds.

In recent times, people studying the dynamics of comets have come to realize it’s not the home of all short-period comets. They largely come from a “scattered disk” of nuclei that are associated with the Belt. So, there’s a lot more work to be done to understand and chart this distant realm of the solar system.

What’s Coming up Next

In a few months, New Horizons (currently sleeping its way to Ultima Thule) will wake up. That will happen in July. After that, it will be all hands on deck as the spacecraft gets closer. At that time, the cameras and other sensors will do their thing on the way to a late December 2018 encounter.

In the meantime, scientists are still analyzing the Pluto data. They’re also touting images the spacecraft took during its last “waking period” in December 2018. They weren’t of a planet, but rather of a star cluster about 1,300 light-years from Earth. While it’s not the best imagery of the cluster, it is the first imagery from such a great distance from the Sun. Not only did New Horizons snap that image, but it also got pictures of two other Kuiper Belt objects. The spacecraft will take images of as many KBOs as it can, adding to our store of knowledge about this distant region.

Kuiper Belts around other Stars

The green light signal arrived from New Horizons earlier today as it traverses the Kuiper Belt. It tells the NH team that the spacecraft (while mostly asleep) is still safely on its way to the next object on its itinerary. That’s another tiny step in the exploration of the outer solar system.

While this study of our own trans-Neptunian region is underway, keep in mind that it’s probably not the only such region in the galaxy. Other stars that have dusty disks around them are pretty likely to have their own versions of this collection of objects. These “extrasolar” disks and belts could be populated with many of the same types of object that we see in ours.

Why Study these Regions?

A number of stars have dusty planet-forming disks around them. Studying those distant Kuiper Belts helps us understand the region where Pluto, Quaoar, Makemake, and Haumea now orbit. Most are pretty young. These “baby” disks are likely a bit narrower and flatter than the older ones, and their materials are still sorting themselves out. Planets form in the disk, some closer to the star than others. The icy “leftovers” eventually migrate to the outer regions where they won’t be destroyed by the heat of the star.

Without going into gory details about disk dynamics, that’s more or less how our planets got sorted out in the early solar system. The rocky bodies formed close to the Sun. The gas giants may well have formed closer to the Sun than where they are now. However, through the disk’s evolution, they made their way out to cooler regions where their gases and ices could exist. The cometary bodies and dwarf planets (icy or ice-covered bodies for the most part) also settled out in the deep freeze.

Plumbing the Depths of our Own Kuiper Belt

Astronomers use many tools to study the regions beyond Neptune. Joining Hubble Space Telescope in the hunt for worlds “out there” is a myriad of observers using ground-based telescopes such as the Palomar Observatory in California, the European Southern Observatory in Chile, the Keck telescopes in Hawai’i, and orbiting observatories such as the Spitzer Space Telescope (which is sensitive to infrared light). Using infrared telescopes helps astronomers detect the “warmth” of these objects as they orbit in the much-colder outer solar system. Even cold bodies such as Pluto can glow in the infrared, giving off clues about them. Granted, they’re very distant and small. So, even with well-equipped facilities, they can and will continue to be difficult to find.

What tales will they tell us about themselves and maybe our own Kuiper Belt? For one thing, studying them long-term will allow astronomers to watch them evolve (slowly but surely). Look at their structures can reveal gaps where giant planets form. As those worlds coalesce, they can nudge smaller objects out to alien Kuiper Belts. That helps astronomers understand how own Belt and Oort Cloud formed billions of years ago. Finally, studies of the distant regions of those disks may reveal water ice and other frozen constituents of outer-system worlds. They could be very similar to what we see at Pluto and beyond. On the flip side, our own Kuiper Belt can tell astronomers what to look for at other circumstellar disks. It’s win-win all the way around.