Solar system

New Horizons is heading for Cosmic Verweggistan

New Horizons in December 2005 on the launch pad in Cape Canaveral.


A huge precision maneuver is when the New Horizons probe on New Year's Day at 6:33 am our time flies right past the only 30-kilometer-long ice sphere Ultima Thule in the border region of the solar system: the Kuiper belt.

From a distance of only 3500 ki-lo-meters, the probe will, among other things, make close-ups of the soil and collect dust samples.

New Horizons was launched in Cape Canaveral on January 19, 2006 as part of the New Frontiers program of the US space agency NASA.

New Horizons in December 2005 on the launch pad in Cape Canaveral.


The probe's main goal was to investigate the dwarf planet Pluto and its five moons during a six-month passage in 2015. New Horizons did so well that the mission was immediately expanded.

New Horizons weighs 478 kilos: about half an ordinary passenger car.

In August 2015, the 2014 MU69 ice object was designated as the next destination in the Kuiper belt.

And now New Horizons has 1.5 billion kilometers on it. With Pluto in his rearview mirror, he has almost reached his destination: object 2014 MU69, also called Ultima Thule, which means 'outer border'.

New Horizons skimmed past Pluto in the second half of 2015.

On the road for 13 years

If New Horizons passes the Ultima Thule ice object on New Year's Day just 3500 kilometers away, the probe has already traveled 6.5 billion kilometers in the solar system since its launch in January 2006.

  • The first photos

    September 2018: New Horizons takes the first photos of it
    Ultima Thule.

  • Adjustment rate

    October 2018: The course to Ultima Thule is adjusted.

  • Discovery obstacles

    December 2018: Like New Horizons
    obstacles discovered, such as dust clouds or rocks, the course changes so that he
    flies along the celestial body not at 3500 but 10,000 kilometers away.

  • Closest passage

    January 1, 2019 6:33 am: New
    Horizons is approaching Ultima Thule as far as possible.

  • Data sent to earth

    2019-2021: Details about Ultima Thule and photos of at least 25 other objects in the Kuiper Belt are sent to Earth.

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Ultima Thule becomes the furthest object a probe has ever visited, and is also one of the most primitive celestial bodies.

With its seven instruments, New Horizons will not only unravel what the millions of small orbs in the corners of the solar system look like, but also how the four outer planets - Jupiter, Saturn, Uranus and Neptune - were created at the time.

Pluto was the first stop

The Kuiper Belt consists of more than a million objects that revolve around the sun in a billions of miles wide strip, even beyond Neptune. In addition to small ice balls such as Ultima Thule, the belt also contains at least five dwarf planets such as Pluto.

The trip to Pluto, 5 billion kilometers from the Earth, lasted 9.5 years and New Horizons was on standby for almost the entire trip to save energy and fuel.

Little was known about this dwarf planet before the mission. The astronomers only knew that Pluto had five moons, a thin atmosphere and a reddish surface with ice of frozen methane, nitrogen and carbon monoxide. But now they know a lot more.

Pluto photographed by New Horizons on July 14, 2015.


The observations of New Horizons lasted six months and showed that Pluto's diameter was 2376 kilometers, 47 kilometers larger than expected.

The probe also saw mountains of 4.5 kilometers in height with methane ice on top, deep gorges of hundreds of kilometers in length and gigantic glaciers of frozen nitrogen.

The largest, Sputnik Planitia, is larger than France and unique in the entire solar system. This glacier has no impact craters, which means that the ice is constantly growing.

To the surprise of scientists, Pluto is still geologically active, and the core of stone under the ice will therefore contain a heat source that keeps the process going.

New Horizons provided a lot of new knowledge about the five moons of Pluto.

The largest, Charon, has no atmosphere, and old impact craters show that the moon is now a dead lump without geological activity.

Pluto's moon Charon.


But a very long time ago, a huge geological activity on Charon created huge ice plains, huge gorges up to 13 kilometers deep and miles of mountains.

The most surprising observation, however, is that the North Pole is covered with a reddish ice cap of methane and nitrogen, gases that must have escaped from Pluto over time and have frozen to the cold pole of the moon. Astronomers have never seen that before.

According to the scientists, the entire system of Pluto and the five moons was formed in the early solar system more than 4 billion years ago in the collision between two major planetesimals: beginnings of planets that originated at the same time, and which have a diameter of only a few meters to a diameter of one few hundred kilometers.

Probe examines 25 objects
Even before launching in 2006, NASA planned to send the $ 700 million probe deeper into the Kuiper Belt for more observations after the visit to Pluto - if the instruments were working and fuel was left.

New Horizons met both conditions, so in 2016 it was definitively decided to extend the mission.

Telescopes have observed multiple stars (the colored lines) where Ultima Thule (dark spot) blocked the light.


The preparation started in 2011, when the researchers went in search of a suitable ice object with the Magellan telescope in Chile and the Subaru telescope in Hawaii.

The target had to be within 1 degree around the trajectory of the probe, so that not too many course changes and therefore fuel were needed.

143 potential destinations were identified, but they required major changes of course.

Only when the team received observation time with the Hubble telescope did three good candidates emerge - Potential Target 1, 2 and 3.

At the end of 2015, candidate 1, Ultima Thule, was closest to the New Horizons job.

When Ultima Thule was chosen, the researchers thought that the ice sphere had a diameter of 30 to 40 kilometers and the shape of a peanut, but recent observations from the earth indicate that there may be two smaller ice balls that circle around each other.

5 instruments go for the primitive planet

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Ultima Thule can be part of a planetesimal: the beginning of a celestial body. By studying its structure, the instruments of New Horizons can therefore look back to the youth of the solar system.


Only when the probe sends the first photos to the earth comes a definite answer.

According to plan, the Ultima Thule probe passes early on New Year's Day and only 3500 kilometers away: a third of the distance with which he passed Pluto. However, the observation time up close is very short, because the probe skims quickly past the planetesimal.

But the resolution of Ultima Thule will be twice as high as at Pluto, so New Horizons will see details the size of a basketball court.

Planet formation becomes insightful

Ultima Thule is the most pristine object from the creation of the solar system that has ever been studied up close.

New Horizons will investigate 25 objects in the Kuiper Belt during his journey.

Hopefully it will become clear what the shape of the ice-cream ball is, what its temperature is, what the bottom and the core consist of and whether it has an atmosphere and dust rings.

If Ultima Thule is a shard that has fallen off in the event of a collision of a planetesimal, the internal structure of the original planetesimal will be visible on the surface.

In that case the scientists can follow the development of planetesimals and clarify how they originated in the early solar system in the event of collisions between chunks of ice, dust and stone. It will give scientists a better picture of how the planetesimals grew, collided and assembled into planets.

New Horizons must observe at least 25 other ice objects from a greater distance until 2021, ranging from 15 million kilometers for small objects to 1.5 billion kilometers for the possible dwarf planet Quaoar. It is located 8 billion kilometers from the earth, at the same distance from Ultima Thule as the earth-sun distance.

Technicians prepare New Horizons in November 2005 for presentation in a sterile room.


The observations must show the shape of the ice objects and what the soil consists of.

This allows astronomers to place the detailed studies of Ultima Thule in a broader context and to develop a new and better model for the creation of the Kuiper belt and outer planets.

For example, if many planetesimals form dual systems, with two objects revolving around each other, that may explain how such planetesimals developed into the four outer planets 4.5 billion years ago.

The Dutch-American astronomer Gerard Kuiper predicted as early as 1951 that there were many small ice objects outside the orbit of Neptunus, but only in 1992 did scientists observe the first.

Now astronauts think that the belt consists of a disk full of ice balls that circle 4.5 to 7.5 billion kilometers from the sun. The Kuiper belt probably contains millions of small planetesimals such as Ultima Thule, more than 100,000 ice objects with a diameter of more than 100 kilometers and at least five - so maybe even more - dwarf planets.

Cooper belt covers the past

In the early solar system, the belt was larger and closer to the sun. Here small planetesimals clashed again and again, forming the four gas planets Jupiter, Saturn, Uranus and Neptune.

As those planets grew, they tug closer together, causing Jupiter to shoot toward the sun about 4.1 billion years ago, while Saturn, Uranus, and Neptune were hurled out to their current orbit.

The other planetesimals went in all directions. Some flew out of the solar system, others moved in the direction of the sun and the inner planets. The impact craters that they left on the moon and Mars can still be seen.

However, most planetesimals were captured by the Neptune gravitational field. This is how they formed the current Kuiper Belt, where the ice balls fly around in the same disk as the planets.

Four types of objects in the Kuiper belt

  • Dwarf planets

    Five dwarf planets - Eris, Ceres, Haumea, MakeMake and Pluto - in the Kuiper Belt have been recognized by the International Astronomical Union. Furthermore, astronomers have found around 50 possible dwarf planets. New Horizons has to photograph five of the candidates.

  • Large planetesimals

    The Kuiper Belt has around 100,000 large ice balls with a diameter of more than 100 kilometers. New Horizons is going to photograph five.

  • Small planetesimals

    The Kuiper Belt contains millions of small ice balls the size of Ultima Thule or even smaller. New Horizons will take 10 to 20 of them. Together with research into larger planetesimals, this should show how planetesimals collide and grow into dwarf planets and planets.

  • Come eat

    In the interior of the Kuiper belt between Neptune and Pluto, some ice balls have an oval orbit. It takes them far into the solar system, where we see them as comets.

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Here, in the dark and cold outer solar system, the small ice balls have been turning in stable orbits for the last 4 billion years.

The temperature in the Kuiper belt is -223 ° C, and therefore the material in and around the objects does not evaporate. The sun is so far away that light and radiation have not changed the surface of the ice balls.

In other words, the objects in the Kuiper Belt are well-preserved original planetesimals, which originated in the same disk of dust, gas and ice lumps as those from which the four outer planets originate.

New Horizons will therefore teach the researchers a lot about both the early solar system and the formation of the planets.

New Horizons catches the first glimpse of Ultima Thule.


The observations of craters that have been created as a result of collisions with rocks and planetesimals are very interesting.

Close-ups of the probe must show how many craters there are.

Because the objects in the Kuiper Belt have been running in a stable orbit for 4 billion years, the craters were not created recently, but must have been formed in the early solar system, when there were many rocks and planetesimals.

If a large number of craters is present, this means that the belt that supplied the building materials to the planets was full of planetesimals, while a small number of craters indicate that the belt was less full.

The astronomers do not currently have such concrete data, and if they enter the results of the probe into the solar system models, the theory will have a stronger foundation.

Probe works until the 2030s

Because Ultima Thule is 6.5 billion kilometers away, it takes about 21 months for the mountain of data that New Horizons has collected about the ice world to be sent to Earth. The research leader, Sol Alan Stern, currently assumes that the first collection of results will be published in September 2021.

New Horizons is the fifth vessel that has crossed the runway of Neptunus and has reached the Kuiper Belt.

As early as 1983 the NASA Probe Pioneer 10, which set out in 1972, passed the gas giant, after which Pioneer 11 and the two Voyager probes followed. The Pioneers sent the latest data in 2003, but the researchers are still in contact with both Voyagers.

The farthest, Voyager 1, is now 21 billion kilometers from the earth and in 2012 was the first vessel ever to cross the heliopause: the boundary of the solar system and interstellar space, where the amount of solar particles is smaller than particles from outside.

The Voyager probes from NASA have been active for more than 40 years.

© NASA / JPL-Caltech

Earlier probes have come far into the Kuiper Belt, but were launched long before the belt's existence was demonstrated in 1992, so their instruments are not designed to be explored there.

For example, the Voyager cameras are not sensitive enough to navigate around the small celestial bodies. The particle detectors from New Horizons can, and moreover the probe is equipped with a dust collector.

In addition to observing more ice objects, the probe will use the amount of dust and hydrogen gases to determine how the solar wind decreases. According to Stern, New Horizons will send data home until the 2030s. The fuel will run out, but the probe will remain in its orbit and cross the border to the interstellar space around 2040.

Video: New Horizons Ultima Thule Flyby (February 2020).

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