A new theory explains Jupiter’s perplexing origin

A new computer model solves a pair of Jovian riddles.

jupiter's surface
(NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)
  • Astronomers have wondered how a gas giant like Jupiter could sit in the middle of our solar system's planets.
  • Also unexplained has been the pair of asteroid clusters in front of and behind Jupiter in its orbit.
  • Putting the two questions together revealed the answer to both.

Jupiter's long been a puzzler to astronomers. Planet formation theory holds that a gas giant forms far away from its star then moves inward over time until it's in a tight orbit around the sun. Jupiter, though, sits right in the middle of our solar system's planets, between Mars and Saturn. And that's not all that's odd: There's an unexpectedly asymmetrical pair of asteroid clusters — known as the Trojan asteroids — preceding and trailing Jupiter in its orbit. The group in front is 50% larger than the one in back. The most widely accepted idea was that Jupiter formed near the Sun and moved outwards.

That's now been turned on its head by a team of scientists from Lund University who ran a series of models to try to identify a plausible origin story for Jupiter. They discovered that the planet and its clusters would be where they are under only one scenario: Jupiter forming way out near Uranus — as gas giants are supposed to do, after all — and moving slowly toward the Sun, attracting and accreting the asteroids that now form its core, with the leftovers trailing behind. Lead author Simona Pirani says, "This is the first time we have proof that Jupiter was formed a long way from the Sun and then migrated to its current orbit." Including the mystery of the asymmetrical Trojans in the simulations was the key.

Modeling history

Jupiter, right in the middle of everything.

(Christos Georghiou/Shutterstock)

The model that lands Jupiter where it is today, along with its thousand of Trojans, begins four times further away from the Sun than Jupiter currently orbits, just inside of Uranus' orbit. Jupiter first took form about 4.5 billion years back as an icy planetary seedling, an ice asteroid, no bigger than Earth. Somewhere between two and three million years later, the future giant began spiraling slowly inward toward the Sun, pulled by gases circulating throughout the solar system. It took about 700,000 years to get where it is now. Along the way, before it developed its gaseous atmosphere and massive size, Jupiter's gravity pulled the Trojans in — the researchers expect Jupiter's core to be composed of materials similar to the Trojans. They're believed to be rich with dark carbon compounds, and likely rich in water and other volatile materials beneath an outer layer of dust.

Lucy in the sky with Trojans

Trojan clusters held in place by the Sun and Jupiter

(Astronomical Institute of CAS/Petr Scheirich)

In October 2021, NASA plans to launch its Lucy mission to study the Trojans. It's believed that they're very old time capsules from the universe of four billion years ago. The craft will study seven of them: one from the solar system's main asteroid belt, and the remaining six from the clusters leading and following Jupiter in its orbit.

Those two Trojan groups are held in place at stable LaGrange points by the combined gravitation pull of the Sun and Jupiter acting together as a single centrifugal force acting upon them.

NASA has high hopes for the mission as chance to get a closeup look at the type of materials from which our planetary bodies formed.

Meanwhile, Jupiter's seeming a little bit less mysterious now, at least in terms of its origin. It may also be that ice giants Uranus and Neptune, as well as Saturn, have a similar history.

Why are so many objects in space shaped like discs?

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Study: Unattractive people far overestimate their looks

The finding is remarkably similar to the Dunning-Kruger effect, which describes how incompetent people tend to overestimate their own competency.

Sex & Relationships
  • Recent studies asked participants to rate the attractiveness of themselves and other participants, who were strangers.
  • The studies kept yielding the same finding: unattractive people overestimate their attractiveness, while attractive people underrate their looks.
  • Why this happens is unclear, but it doesn't seem to be due to a general inability to judge attractiveness.
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Astronomers find more than 100,000 "stellar nurseries"

Every star we can see, including our sun, was born in one of these violent clouds.

Credit: NASA / ESA via Getty Images
Surprising Science

This article was originally published on our sister site, Freethink.

An international team of astronomers has conducted the biggest survey of stellar nurseries to date, charting more than 100,000 star-birthing regions across our corner of the universe.

Stellar nurseries: Outer space is filled with clouds of dust and gas called nebulae. In some of these nebulae, gravity will pull the dust and gas into clumps that eventually get so big, they collapse on themselves — and a star is born.

These star-birthing nebulae are known as stellar nurseries.

The challenge: Stars are a key part of the universe — they lead to the formation of planets and produce the elements needed to create life as we know it. A better understanding of stars, then, means a better understanding of the universe — but there's still a lot we don't know about star formation.

This is partly because it's hard to see what's going on in stellar nurseries — the clouds of dust obscure optical telescopes' view — and also because there are just so many of them that it's hard to know what the average nursery is like.

The survey: The astronomers conducted their survey of stellar nurseries using the massive ALMA telescope array in Chile. Because ALMA is a radio telescope, it captures the radio waves emanating from celestial objects, rather than the light.

"The new thing ... is that we can use ALMA to take pictures of many galaxies, and these pictures are as sharp and detailed as those taken by optical telescopes," Jiayi Sun, an Ohio State University (OSU) researcher, said in a press release.

"This just hasn't been possible before."

Over the course of the five-year survey, the group was able to chart more than 100,000 stellar nurseries across more than 90 nearby galaxies, expanding the amount of available data on the celestial objects tenfold, according to OSU researcher Adam Leroy.

New insights: The survey is already yielding new insights into stellar nurseries, including the fact that they appear to be more diverse than previously thought.

"For a long time, conventional wisdom among astronomers was that all stellar nurseries looked more or less the same," Sun said. "But with this survey we can see that this is really not the case."

"While there are some similarities, the nature and appearance of these nurseries change within and among galaxies," he continued, "just like cities or trees may vary in important ways as you go from place to place across the world."

Astronomers have also learned from the survey that stellar nurseries aren't particularly efficient at producing stars and tend to live for only 10 to 30 million years, which isn't very long on a universal scale.

Looking ahead: Data from the survey is now publicly available, so expect to see other researchers using it to make their own observations about stellar nurseries in the future.

"We have an incredible dataset here that will continue to be useful," Leroy said. "This is really a new view of galaxies and we expect to be learning from it for years to come."

Protecting space stations from deadly space debris

Tiny specks of space debris can move faster than bullets and cause way more damage. Cleaning it up is imperative.

Videos
  • NASA estimates that more than 500,000 pieces of space trash larger than a marble are currently in orbit. Estimates exceed 128 million pieces when factoring in smaller pieces from collisions. At 17,500 MPH, even a paint chip can cause serious damage.
  • To prevent this untrackable space debris from taking out satellites and putting astronauts in danger, scientists have been working on ways to retrieve large objects before they collide and create more problems.
  • The team at Clearspace, in collaboration with the European Space Agency, is on a mission to capture one such object using an autonomous spacecraft with claw-like arms. It's an expensive and very tricky mission, but one that could have a major impact on the future of space exploration.

This is the first episode of Just Might Work, an original series by Freethink, focused on surprising solutions to our biggest problems.

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Meet the worm with a jaw of metal

Metal-like materials have been discovered in a very strange place.

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