Now that New Horizons has zipped past Pluto, it’s main mission is to gradually transmit back all the data it gathered during the flyby. We’ve already learned some amazing things from the mission, and we’re certain to learn more as the rest of the data reaches us. But not content with just one flyby, the New Horizons team has another target in their sights.

The target they’ve chosen is known as 2014 MU69. It’s about 35 km across, and is part of the Kuiper belt, which is an icy outer region of objects similar to the asteroid belt between Jupiter and Mars. The encounter will give us an opportunity to see a Kuiper belt object up close, so we should learn a lot form a type of solar system body we currently know very little about.

If all goes as planned, New Horizons should make its flyby of MU69 in January 2019.

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New Horizons is closing in on Pluto, and that means we’re finally getting some detailed images of the small world. With the appearance of new surface features comes a new batch of questions.

The latest comes from a new color images of Pluto and Charon. The images were created by combining high resolution images from the Long-Range Reconnaissance Imager (LoRRI) with color data from RALPH. What’s clear is that there is a chain of features along the equator of Pluto. Whether these are features similar to the equatorial region of Iapetus or some type of cryovolcanic activity is still not clear. It’s also clear from the image that Pluto and Charon are quite different in both color and brightness. Given that the two bodies are thought to have formed from a collision with another body, it will be interesting to see how they can be so different.

The best Hubble image of Pluto and Charon.

We’re still in the speculation stage, since the data is so new, but the exciting thing about these images is that Pluto is no longer a spot a few pixels wide. It’s a world with clear features and with mysteries to be revealed. We’re finally exploring everyone’s favorite little world, and that’s a huge scientific achievement.

New Horizons will make its closest approach on July 14, so we can expect a flurry of images leading up to that time. Of  course it will take months for the all the data to be transmitted back to Earth, so long after the flyby we’ll Pluto is going to be rising in the news.

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NASA has released the first color image of Pluto and its moon Charon from the New Horizons spacecraft. While it may not look like much, it’s only going to get better from now until the spacecraft’s closest approach in July. 

Although the image above is touted as a color image, it’s actually a composite image that approximates Pluto’s actual colors. Like other spacecraft, the CCD cameras on New Horizons only detect brightness within a particular spectral range. These are then combined to create a simulated color image. For this mission there are four detectors, for blue, red, near infrared, and a narrow band filter specifically for methane spectra.

The best Hubble image of Pluto. Credit: HST

While a color image of Pluto and Charon is impressive, it’s an indication that New Horizons is now close enough to get better images than we’ve had before. In addition to the imagery, there are several other detectors on the probe, measuring things like solar wind, dust particles, atmospheric spectra and radio telemetry. Since the spacecraft will make a fast flyby of Pluto, data will need to be gathered quickly.

But for now we can enjoy the distant dwarf planet in living color.

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New Horizons is a small spacecraft on its way to Pluto. It will make its closest approach next Summer. To get to Pluto in a reasonable time, the spacecraft is heading there at high speed. This means it will zip past Pluto and head out into the Kuiper belt. While Pluto is a worthy goal, it would be nice if New Horizons could observe other objects in the outer solar system. But given the high speed of the spacecraft, and the low mass of Pluto, there isn’t a good way to use the planet’s gravity to change direction towards a particular Kuiper belt object (KBO). Basically, New Horizons is on a straight trajectory out of the solar system. So instead astronomers have been searching for KBOs that are along the path of New Horizons, and they’ve found some candidates.

Credit: Alex Parker, SwRI

The three possibilities are KBOs known as PT1, PT2 and PT3. In this case PT stands for “potential target.” Of these PT1 is in best alignment with the trajectory of New Horizons, and thus would require the smallest delta-v adjustment. What’s exciting about this is that we haven’t had a good look at any Kuiper belt objects, given their large distance and small size. The closest we’ve got are moons such as Neptune’s Triton, which we think is a captured KBO.

If successful, New Horizons will make its flyby of PT1 in January of 2019.

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Whenever I talk about the planets of the solar system, someone usually asks “what about Pluto?”  Many people have an emotional attachment to the planet, and feel somewhat offended that the mean astronomers have declared the tiny world to be not a planet.  So what about Pluto?  Well, it turns out we now know a great deal more about the planet than we did when you were little, and we’ll soon know even more.

When Pluto was first discovered in 1930, it was seen only as a faint point of light that moved relative to background stars.  It was only due to photographic observations that it was discovered at all.  Because of its distance it was difficult to determine the characteristics of Pluto.  We had no way to determine its mass, and estimating its size could only be done by guessing its albedo (how much light it reflects).  If it was a bright world it could be rather small, but if it was a dark world it would be rather big.

Left: first image of Pluto with moon Charon.
Right: more modern Hubble image.

Then in 1977 a magnified photographic image of pluto showed a slight bulge.  Analysis of other images showed the bulge appeared with a period of about 6 days.  Pluto’s moon Charon had been discovered.  With the discovery of a moon it was then possible to determine the mass of Pluto.  It was found that Pluto’s mass was quite small, less than a fifth of our own Moon.  Later we determined its diameter is only about 70% that of the Moon.

Pluto is clearly part of the Kuiper family. Credit: Scott Sheppard

That alone is enough to question the idea that Pluto should be considered a planet, but then we began to find more objects with similar distances and orbits as Pluto.  They form the Kuiper belt, which is an icy version of the asteroid belt beyond the orbit of Neptune.  Pluto is the largest Kuiper belt object (KBO), but we now know of more than a thousand KBOs larger than 100 km.  Pluto is very clearly part of a family of objects.  Which is one of the reasons it was demoted from being a planet.

The planet Pluto everyone loved was a dim speck of light.  The last planet at the edge of our solar system.  The dwarf planet Pluto of today is the largest member of an icy belt that marks the beginning of the outer solar system.  It is also the first such object we will explore.  In 2015 the New Horizons spacecraft will make a flyby of Pluto, giving us the first detailed images of a KBO.

So don’t mourn Pluto the dim dot of a planet.  Celebrate Pluto, the king of the Kuiper belt, and guardian of the great beyond.

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