Very late in the evening (or, if you will, very early tomorrow morning), the New Horizons spacecraft will perform the farthest flight of an astronomical object ever undertaken by mankind. At 05:33 UTC on January 1, the New Year, it will pass about 3,500 kilometers from 2014 MU69, a strange wad of ice and rocks revolving around the Sun far beyond Neptune. If successful, the probe will return the first close-up images of the Kuiper Belt object in situ, transferring data from a stunning 6.6 billion kilometers from the earth.
So yes, this is a pretty big deal.
You may remember the New Horizons as a spacecraft that flew over Pluto in July 2015 and returned a wealth of data about the tiny ice world, including magnificent images that changed how we see and perceive the external solar system.
But the solar system does not end with Neptune and Pluto. There is a donut-shaped space occupied by millions of objects, consisting mainly of rock and ice. For historical reasons, this is called the Kuiper belt. Predicted to exist for decades, the first Kuiper belt object (or BWC) was not discovered until the 1990s … and now we know thousands. Some people (including me) consider Pluto to be the largest of the currently known objects.
Even before the passage of Pluto in 2015, the search continued for a potential second target for New Horizons in the Kuiper belt. The story behind this is really cool – team member Alex Parker wrote a great message for NASA about it, and awesome twitter thread – but, briefly, in 2014, Hubble discovered the KBO, which was close enough along the trajectory of the spacecraft to make it a target with the remaining amount of fuel. He was given the designation MU69 2014, although you will probably hear that he is called Ultima Thule, the unofficial nickname given to him after a public competition held by the New Horizons team.
We still know little about MU69. It is so far and so small that it is barely visible to earth telescopes, and even New Horizons did not notice it until August 2018. Its orbit is slightly elliptical and holds it at a distance of more than 6 billion kilometers from the Sun, over a billion kilometers farther than Pluto. Some clever observations have shown that MU69 is either two objects rotating very close to each other (which makes it a binary object), or an object with a double blade, such as comet 67P / Churyumov-Gerasimenko. The two components are likely to be about 20 kilometers wide (and possibly smaller). We know that this is a reddish color, like many such objects (UV light from the Sun splits carbon-based molecules that are rearranged into more complex molecules called tolins, and they are usually red).
And it's all. But in a few days we will find out lot More.
I urge you to read the story of my friend Emily Lakdavalla about today's meeting she wrote for the Planetary Society. As always, her article is clear, interesting and contains all the necessary information to understand what's what.
I also want to make a few comments.
First, since the MU69 is so small and weak, and was only recently discovered, we do not know its position. exactlyIt is well known how to plan a flight, but as New Horizons approaches, this uncertainty literally grows. Remember also that the MU69 has a width of only 20-40 kilometers or so … and the New Horizons will scream past KBO with relative speed 14 kilometers per second – more than 50,000 kilometers per hour. Because of this, the MU69 will not be much larger than a pixel or three across, until almost the fight itself.
Engineers try not to risk, and programmed the spacecraft so that it returns some images at a sufficiently early distance so that they are sure that MU69 will be in the frame and then a little closer where it will be large enough to see some details. But the collision is so fast that the spacecraft will perform a pre-programmed set of observations during the collision itself, wasting all its time studying the MU69. Images will not be sent back until they pass … and even then radio waves moving at the speed of light (because they are bright) will take six hours to return to Earth. Even then, they will not be published until scientists have the opportunity to look and clean them up a bit (the raw data from a spacecraft usually needs to be processed so that they are easier to examine), so this may be a day or so before start seeing real images.
And what will we see? This is a good question. There were some interesting news that the brightness of the MU69 over time (what astronomers call light curve) pretty flat, which is weird. If it were elongated (or two objects rotating around each other), then one would expect it to become brighter and dimmer with time as it rotates. If the surface is spotty, it can be expected that the brightness will change to its rotation. So far, nothing like this has been seen. Is it faceless? Or do we accidentally see that he is looking directly at one of the poles, so that while he rotates, we do not see how new functions appear? This last bit seems unlikely, as we have seen that there are two large components in it, and it is difficult to understand how we can separate them, and at the same time look down. So weird.
Are there smaller moons revolving around the main body? Could it be rings? Is there a cloud of dust around it? Is the surface smooth or rough, hilly or flat, cellular or smooth? All these are important questions that will tell us a lot about this remote object, and, I hope, all of them will be answered by “New Horizons”
And they will respond in the coming days.
Having said that, I will add that over the next week I will be on Star Trek: The Cruise III, where the Internet is heterogeneous. I, most likely, will not be able to write about any images that come down. So check out the SYFY homepage for the views of other authors, follow emily on twitter, and her list of twitter people covering circlingYou can also follow mission "New Horizons" on twitter and hey: give Alex parker follow too.
Let's see what's there.