Very late at night (or tomorrow morning, if you prefer), the New Horizons ship will make the farthest flyer of an astronomical object that you have never tried for humanity. At 05:33 UTC January 1, New Year's Day, it will pass 3,500 kilometers from 2014 MU69, a strange pack of ice and rock that orbits the Sun through Neptune. If successful, the probe will return the first foreground images of a Kuiper Belt Object on the spot, which conveys data in a surprising way 6.600 million kilometers from the Earth.
So yes, this is a big problem.
You can remember New Horizons as the ship that flew to Pluto in July of 2015 and returned a large amount of data from the small frozen world, including magnificent images that changed the way of seeing and thinking about the outer solar system.
But the solar system does not end with either Neptune or Pluto. There is a volume of bagel space occupied by millions of objects that consist mainly of rock and ice. For historical reasons, this is known as the Kuiper belt. Prediction to exist for decades, the first Kuiper waist object (or KBO) was not discovered until the 1990s … and now we know thousands. Some people (including myself) consider that Pluto is the largest of these known objects so far.
Even before Pluto's downfall in 2015, a search was made to find a possible second goal for New Horizons in the Kuiper belt. The story behind this is really great: team member Alex Parker wrote a great blog post for NASA about it, as well as a fantastic thread on Twitter – But to make a long story, KBO was discovered by Hubble in 2014 that was close enough to the spacecraft's trajectory to make it a target with the available fuel. The 2014 MU69 nomination was granted to you, although you will probably hear Ultima Thule, an unofficial nickname that was given after a public contest held by the New Horizons team.
We do not know much about MU69 yet. It is so far and so small that it is hardly possible to see terrestrial telescopes, and even New Horizons did not detect it until August 2018. Its orbit is gently elliptical and holds it in addition to 6 billion kilometers from the Sun, much more than one billion kilometers far beyond Pluto. Some intelligent observations show that MU69 are two objects that orbit very closely (turning it into a binary object) or a double lobed object such as comet 67P / Churyumov-Gerasimenko. Both components probably have about 20 kilometers in length (and perhaps smaller). We know that it is reddish, as many of these objects (the sun's ultraviolet light breaks the molecules based on carbon that are grouped into more complex molecules called tholins, and these tend to be red).
And that is it. But in a few days we will meet one a lot more.
I firmly agree, I invite you to read the breakdown by my friend Emily Lakdawalla about this night's meeting she wrote for The Planetary Society. As always, your article is clear, interesting and has all the information you need to understand what it is.
There are some points I want to do too.
One is that, because MU69 is so small and weak, and only recently discovered, we do not know its position precisely. It is known enough to plan the flyby, but as New Horizons approaches, this uncertainty literally increases. Remember, too, that MU69 only has between 20 and 40 kilometers … and New Horizons will call beyond the KBO at a relative speed of 14 kilometers per second – more than 50,000 kilometers per hour. Due to this, MU69 will not be much more than a pixel or three until almost the same encounter.
Engineers are playing safely, and have programmed the spaceship to return some images from afar that they are sure MU69 will be shot and, once again, closer to where it will be big enough to see some details. But the meeting is so fast that the spacecraft will perform a set of pre-programmed observations during the meeting, spending all the time examining MU69. The images will not be sent until it happens … and even the radio waves are taken, traveling at the speed of light (because they are light), six hours to return to Earth. Even so, they will not be released to the public until scientists have the opportunity to take a look and clean them a bit (raw data from a spaceship should generally be processed to make them easier to examine), so it can be a day or so before you begin to see the actual images.
And what will we see? This is a good question. There have been interesting news that the brightness of MU69 over time (what astronomers call it the curve of light) It's pretty flat, it's strange. If it was lengthened (or two objects that orbit each other), I would expect it to be more bright and moderate over time as it turned. If the surface is irregular, I would expect the brightness to change as you turn. You have not seen anything like this yet. Has nothing Or do we see that he looks down at one of his poles, so that, as he turns, we do not see the new features? This last bit seems improbable, since we have seen that it has two important components, and it is difficult to see how we could separate them, but, look down the pole. So it's strange.
Are there smaller moons that orbit the main body? Could you have rings? Is there a cloud of dust around? Is the surface soft or rough, rugged or flat, crater or soft? All these are important questions that will tell us a lot about this distant object, and all of them, luckily, will be answered by New Horizons.
And they will respond in the next few days.
Having said that, I will add that for the next week I will be in Star Trek: The Cruise III, where the Internet is irregular. I will probably not be able to write about any image that goes down. Thus, check the page of SYFY for other author views, Follow Emily on Twitter, and also your Twitter list of people who cover the flyby. You can also follow it the mission of New Horizons on Twitter, and hey: Give Alex Parker a follow-up, too.
Let's see what's in it.