New Horizon’s Next Target – First Image of Ultima Thule

On New Year’s Day the New Horizons spacecraft will make the most distant planetary encounter ever attempted, and for the first time, it has its target in its sights. Welcome back to Launch Pad Astronomy, I’m Christian Ready your, friendly neighborhood astronomer. New Horizons took this image of the tiny Kuiper belt object 2014 MU69 when it was at a distance of over 6 billion kilometers from Earth. The Kuiper belt is a doughnut shaped region of small icy bodies out beyond the orbit of Neptune. Some of these objects, such as Pluto and Eris can be relatively large, while most of these objects are small primordial icy bodies – essentially comet nuclei. MU69 was discovered by the Hubble Space Telescope which searched for potential objects New Horizons could fly past after its encounter with Pluto in 2015. Hubble was able to determine MU69’s orbit and verified that it did in fact lay within New Horizons flight path. That allowed the New Horizons team to adjust the spacecraft’s trajectory to intercept the object on New Year’s Day 2019. The team gave MU19 the unofficial nickname of Ultima Thule, latin for ‘beyond the borders of the known world’. However, New Horizons itself hadn’t actually seen its target yet. So in August 16th of this year, the New Horizons team pointed its Long Range Reconnaissance Imager or LORRI telescope at the position where they expected Ultima Thule to be. The object was located amidst a crowded field of bright stars. But after doing some extensive image processing, Ultima emerged as a faint glow exactly where the team predicted it would be. And this is important because it meant that New Horizons would not have to make any additional course adjustments, and that saved precious onboard fuel for science. But in order to do that science, the team needs to know as much about Ultima as possible. An opportunity to learn more about Ultima came in 2017 when it passed in front of a star causing the star to temporarily wink out. This event is known as an occultation, and by observing the occultation from slightly different locations along a north-south line in Argentina, the team was able to put together a picture of the possible shape of Ultima Thule. But what they found was a surprise; Ultima Thule may not be one object but could be two! It has a double lobe structure and we’ve seen the structure like this before when the Rosetta spacecraft encountered Comet 67P/Churyumov-Gerasimenko. Its two lobes may in fact be two smaller comets that came together and are bound by gravity. Or it could be a single large object that lost most of its central region either through outgassing or a possible collision. However, Comet 67P is only four kilometers wide – Ultima Thule has two lobes of 20 and 18 kilometers, respectively. Now obviously we’re going to learn a lot more about Ultima when New Horizons passes by on New Year’s Day. It will pass just 3,500 kilometers away from the object – that’s three times closer than New Horizons got to Pluto! But the encounter will only last a couple of hours because New Horizons is traveling more than 14 kilometers per second. That’s fast enough to go from New York to LA in under five minutes. But here on Earth, were going to have to be patient because it takes light over six hours to travel from the spacecraft across the solar system to Earth. Not only that but the download rate is pretty low – about one kilobit per second. That means it’ll take several days and weeks just to get the low-res preview images, and another couple of years to download all of the data from the spacecraft. But it’ll be worth the wait because this is an opportunity to glimpse the earliest formation of our solar system from 4.6 billion years ago when the solar system was just beginning to form. Now if you’d like to learn more about the formation of the solar system and a few of the cool things that have been happening in it, I’ll have some links here and in the description below. So let me know what are your plans for New Year’s Day? You gonna to catch the game, watch the Mummers parade, or download telemetry from an outbound spacecraft? Let me know in the comments below and I’ll be sure to check them out. And if you’d like to join me on this journey through this amazing universe of ours, well please make sure to subscribe and ring that notification bell so that you don’t miss out on any new videos. Until next time, I’m Christian Ready, and keep watching the skies. [BEEP] Horizons is the same spacecraft that flew past Pluto in 2015. This mission was designed as a flyby mission because to slow down… this mission was designed to be a flyby of….[BEEP] New Horizons made history when a flew past Pluto and …. how many times have I said this line man? [laughs] It’s nice and quiet though cicadas finally stopped… …well sort of… [cicadas singing] no they didn’t. [BEEP]


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