Time capsules from the birth of our Solar System more than 4 billion years ago, the swarms of Trojan asteroids associated with Jupiter are thought to be remnants of the primordial material that formed the outer planets. The Trojans orbit the Sun in two loose groups, with one group leading ahead of Jupiter in its path, the other trailing behind. Clustered around the two Lagrange points equidistant from the Sun and Jupiter, the Trojans are stabilized by the Sun and its largest planet in a gravitational balancing act. These primitive bodies hold vital clues to deciphering the history of the solar system, and perhaps even the origins of organic material on Earth.
NASA’s Lucy will be the first space mission to study the Trojans. The mission takes its name from the fossilized human ancestor (called “Lucy” by her discoverers) whose skeleton provided unique insight into humanity’s evolution. Likewise, the Lucy mission will revolutionize our knowledge of planetary origins and the formation of the solar system.
Lucy is slated to launch in October 2021 and, with boosts from Earth’s gravity, will complete a 12-year journey to eight different asteroids — a Main Belt asteroid and seven Trojans, four of which are members of “two-for-the-price-of-one” binary systems. Lucy’s complex path will take it to both clusters of Trojans and give us our first close-up view of all three major types of bodies in the swarms (so-called C-, P- and D-types).
This diagram illustrates Lucy’s orbital path. The spacecraft’s path (green) is shown in a frame of reference where Jupiter remains stationary, giving the trajectory its pretzel-like shape. After launch in October 2021, Lucy has two close Earth flybys before encountering its Trojan targets. In the L4 cloud Lucy will fly by (3548) Eurybates (white) and its satellite, (15094) Polymele (pink), (11351) Leucus (red), and (21900) Orus (red) from 2027-2028. After diving past Earth again Lucy will visit the L5 cloud and encounter the (617) Patroclus-Menoetius binary (pink) in 2033. As a bonus, in 2025 on the way to the L4, Lucy flies by a small Main Belt asteroid, (52246) Donaldjohanson (white), named for the discoverer of the Lucy fossil. After flying by the Patroclus-Menoetius binary in 2033, Lucy will continue cycling between the two Trojan clouds every six years.
Image Credit: Southwest Research Institute
Last Updated: Sep 22, 2021
Editor: Yvette Smith
Far out!
I’d like to see a discussion of UFOs on this blog- now that we got the not so great June 24th Pentagon Report.
What is there to discuss? The truth is out there.
Scully was a babe….
Still is.
For a woman in her 50’s, Gillian Anderson is ageing very well.
I want to see some good, detailed pictures of UFO’s. I haven’t seen any yet, although there are some intriguing pictures.
I think if UFO’s become more than speculation, they will be discussed at WUWT.
First hand testimony from Air Force pilots are describing something tangible, and should not be dismissed out of hand.
I think if we ever do discover we are not alone and our space neighbors can travel from one star to another, then it will be off to the races for the human race. Once we realize it can be done, we will find the way to do it ourselves, if our neighbors in space won’t lend us the technology. Then, we will travel all over the galaxy/universe depending on the available technology.
Humans are just taking baby steps when it comes to understanding the physical universe. We keep discovering new particles all the time.
Recent research does seem to favor the conditions for life to develop around many stars. It seems all it would take is to have a world large enough to have water on its surface, and then the claim is that just about any asteriod strike on the planet would create the conditions within the area struck so that life could emerge. A Yellowstone Park type of environment. If that’s all it takes to create living creatures, then every planet with at least a modest environment should have something alive living on it.
So how many of those lifeforms would go on to develop space flight?
Every discovery will be an unexpected surprise that contradicts standard models and their underlying theory, but rather than changing the theory to be consistent with observations, they’ll come up with ad-hoc explanations for why these particular surprises don’t actually change anything.
This is science now.
What they will likely discover is that the asteroid belt is made from a planet that had increasing amounts of CO2 in its atmosphere, and became so hot that it exploded. I really, really wish that I could add a sarc tag, but I’m afraid that in all honesty I cannot.
I would like that graphic to include the actual positions of the planets and such with time. Jupiter’s orbit is just under 12 years, so it will be similar to how it started when it reaches the second Lagrange point, but if it takes 6 years to get to the first one, that will be in a very different location.
I am also curious about Earth’s location during the multiple passes of Earth’s orbit. Is it checking our Lagrange points? Will we finally get to see the spot 180 degrees opposite of earth in such a way that we can prove nothing is there?
But, if we want to truly know what these ‘primordial materials’ are, shouldn’t we be landing on them or carrying a gun to blow debris into space so that we can see what they are made of?
The wording up at the top of the image states that the frame (of reference) rotates with Jupiter, i.e. Jupiter is stationary in this frame of reference. And so is the Sun (approximately, Jupiter’s orbit is, like all planets, slightly elliptical, so the Sun would wobble back and forth a bit). It would be the Earth that moves, as well as the background stars (if they were drawn).
As for Earth’s Sun-Earth Lagrange points, the James Webb space telescope is supposed to set up work at the L2 point. The L3 point has been observed by other spacecraft, although they didn’t (afaik) actually pass through it. It is at any rate an unstable Lagrange point, because Venus passes close enough to it to evict anything that was orbiting the Sun there.
Landing on an asteroid requires a great deal more fuel than flying by it–not because the asteroid has a deep gravity well (they don’t), but because you have to match speeds.
@James – On the second question, we already know that there is nothing (of any significance or permanency) in the “counter Earth” position. The L1, L2, and L3 positions are inherently unstable – anything in those positions will drift out of them without constant station-keeping adjustments.
Only L4 and L5 are stable. “Metastable,” actually – objects there orbit around the point, they don’t “sit” right on it.
Incidentally, I’m pretty sure that there are images somewhere of the Sun-Earth L3 point. Whether for checking calculated positions against the stars, or to get a wider baseline for more precise parallax computations, cameras on missions to other planets get pointed every which way.
According to this 1969 sci-fi film, there was a “mirror” Earth on the other side of the sun.
https://en.wikipedia.org/wiki/Doppelg%C3%A4nger_(1969_film)
Jupiter’s LaGrange points aren’t equidistant from it and the Sun. They lie on Jupiter’s orbit.
Pretend for a moment that the orbit is a pure circle, radius R. Farthest point on the orbit is a distance 2 R from the planet. So there must be points on the orbit that are a distance R from the planet.
To find those points, draw a circle, radius R with the sun as the center, Jupiter’s orbit, and a circle, radius R with Jupiter as the center. The two intersections are where the Lagrange points should be.
It would help if you have a good compass or a good drawing program. But you can always use any circular object with a flat bottom as a template for the circle.
Why would the distance from Jupiter to the LaGrange point be equal to the orbital radius? If an object were equally distant from Jupiter and the Sun, the force of gravity due to the Sun would be greater, due to the greater mass of the Sun. This would tend to pull the object toward the Sun, into an orbit closer to the Sun than Jupiter’s orbit.
The distance along Jupiter’s orbit to the LaGrange point (so that the gravitational acceleration from Jupiter and the Sun are equal) would be given by
r = R * sqrt (Mj / Ms)
where Mj is the mass of Jupiter, and Ms is the mass of the Sun.
Have they changed the system recently? I always thought that L3 and L4 were in those positions with L5 being on the opposite side of the sun and L1 and L2 being on either side of the planet with L1 to sunward.
Someone got it wrong in something that you’ve read. It’s always been L1, L2, L3 in the line through the two masses, and L4, L5 at sixty degrees each way. (Referenced from the more massive object, and the points being where the line intersects the orbit of the less massive object.) Oh, and L4 is the point ahead of the less massive object in its orbit, while L5 is the point behind.
James Bailey answers this in some detail, but more briefly: yes, they are equidistant from Jupiter and from the Sun, AND they lie on Jupiter’s orbit.
I get what the author was saying now. Thanks.
“..with boosts from Earth’s gravity”.
Yeah, right. This kind of science “communiucation” probably causes more science ignorance in the long run.
Presumably, what they mean to say is that the trajectory of the ship will at one or more points, bring it back within the significant gravitational influence of the Earth to cause acceleration/deceleration and/or a change in direction. Earth’s gravity only “boosts” downwards, towards the surface of the Earth. All that feersum engine power is mostly required to “boost” rockets away from Earth’s gravity.
You time your use of thrusters to when you enter a gravity well, thus increasing the DeltaV you get from your thrust. I forget what the maneuver is technically called- I’m sure someone else here can remind me.
Anyway- that is one crazy trajectory there..
I think it’s referred to as “gravity assist”. It’s been a wonderfully useful manoeuvre over many decades to save fuel and time as the spacecraft passes into and out of the Earth (or another planet’s) gravity well.
I think it is also colloquially referred to as a ‘slingshot’. This is because it works in a very similar way to a slingshot itself. Abd yes, Jupiter is the most effective planet for this. The sun can be used, but you obviously cannot get too close.
I don’t believe the sun can be used since the energy to increase the velocity comes from the planet’s orbital energy.
I’m feeling somewhat old, here – I’ve known about that maneuver since I attained my first of six plus decades.
It was a major plot element in Robert A. Heinlein’s “The Rolling Stones” novel. (Called a “juvenile” then, would be a “YA” novel now.)
The family departed Luna on an orbit towards Earth, then thrusted at perigee to send their ship on a much faster and economical orbital path to Mars. There was a whole bit about the time for this actually being a “window” – outside of which it would not work. Capitalism at work – the middle of the window, being the best time, incurred an extra fee to Traffic Control, which the family could not pay; only the big luxury passenger liners used that period and paid the money. If I recall correctly, the Stone family used the earlier part of the window that had no fee, and cost more in fuel – but not as much as paying the fee would have been.
A bit of drama inserted when the youngest member looked like they would not be able to adapt to free fall, and the father contemplated changing his maneuver to return to Luna (which would have had him up in front of the Admiralty Board, losing his pilot’s license, and possibly ending up in prison for endangering the long line of ships following him).
Thanks for the reminder.
The energy boost comes from the orbital energy of the planet, not gravity. As the object approaches the planet from behind “equal and opposite” forces cause the object to speed up and the planet to slow minusculely. Proper orientation of the orbits mean that the energy imparted to the object is not returned to the planet as the object retreats.
Again, others have answered this in more detail, but the reason Earth (or any other planet) can boost the spacecraft with its gravity is that the Earth is not stationary. (I think Galileo pointed that out.) The trajectories are calculated to rob a miniscule amount of energy from Earth and add that to the spacecraft’s energy.
The maneuver can use the spacecraft’s engines to get an even greater boost during the fly-by. The engine-powered boost is sometimes called an Oberth maneuver, after Hermann Oberth, who described it nearly a century ago.
Gosh, a century ago…there’s obviously nothing new under the Sun!
“Hermann Oberth”
A pioneer of space flight.
From the article: “The Trojans orbit the Sun in two loose groups, with one group leading ahead of Jupiter in its path, the other trailing behind.”
A little history: One of those groups used to be called the “Greeks”. Greeks and Trojans.
The Lagrange points occupy very shallow gravity field depression. Objects in them are easily disrupted by other planets and many objects aren’t even in the Lagerange area stably. Becaue of that it seems extremely unlikely that they will contain anything that has been there for a long time. Whoever thinks they are “remnants of the primordial material that formed the outer planets” is either fooling themselves or trying to fool those in charge of appropriations.