WASHINGTON — Jupiter, the solar system’s largest planet, may have been smacked head-on by an embryonic planet 10 times Earth’s mass not long after being formed, a monumental crash with apparent lasting effects on the Jovian core, scientists said on Thursday.
The violent collision, hypothesized by astronomers to explain data collected by NASA’s Juno spacecraft, may have occurred just several million years after the birth of the sun roughly 4.5 billion years ago following the dispersal of the primordial disk of dust and gas that gave rise to solar system.
“We believe that impacts, and in particular giant impacts, might have been rather common during the infancy of the solar system. For example, we believe that our moon formed after such an event. However, the impact that we postulate for Jupiter is a real monster,” astronomer Andrea Isella of Rice University in Houston said.
Under this scenario, the still-forming planet plunged into and was consumed by Jupiter.
Jupiter, a gas giant planet covered in thick red, brown, yellow and white clouds, boasts a diameter of about 89,000 miles (143,000 km). Interior models based on Juno data indicated Jupiter has a large “diluted” core representing about 5 to 15 percent of the planet’s mass comprised of rocky and icy material unexpectedly mixed with light elements like hydrogen and helium.
“Juno measures Jupiter’s gravity field to an extraordinary precision. Scientists use that information to infer Jupiter’s composition and interior structures,” said Shang-Fei Liu, associate professor of astronomy at Sun Yat-sen University in Zhuhai, China, and lead author of the research published in the journal Nature.
Computer models indicated that a head-on collision with a protoplanet – a planet in its formative stages – of roughly 10 Earth masses would have broken apart Jupiter’s dense core and mixed light and heavy elements, explaining Juno’s findings, the researchers said.
This protoplanet, with a composition similar to Jupiter’s primordial core, may have been slightly less massive than the solar system’s most distant ice giant planets Uranus and Neptune and would have become a full-fledged gas giant if it had not been swallowed by Jupiter, Liu said.
Jupiter already would have been fully formed at the time, with its strong gravitational pull perhaps precipitating the collision. Jupiter’s mass is about 320 times that of Earth.
Liu said tens of thousands of computer simulations indicated at least a 40% chance that Jupiter was hit by a protoplanet early in its history, with this impact scenario offering “by far the best explanation” for the nature of Jupiter’s core.
(Reporting by Will Dunham; Editing by Sandra Maler)
SpaceX’s next Starship prototype won’t be just a concept vehicle for much longer.
Construction of the test craft is proceeding apace, as two new photos posted on Twitter today (Sept. 17) by company founder and CEO Elon Musk reveal.
One of the images shows the vehicle — apparently Starship Mk1, which is being assembled at SpaceX’s South Texas facility, near the village of Boca Chica — in the background, standing behind a building that contains a variety of parts and other equipment. (SpaceX is also building a similar prototype, called Starship Mk2, at the company’s Florida facilities, reasoning that a little intracompany competition will improve the vehicle’s final design.)
The Mk1 and Mk2 follow in the footsteps of SpaceX’s Starhopper vehicle, which was retired after acing a big test flight last month. But the new vehicles are far more ambitious and more capable. Whereas Starhopper sported just a single Raptor engine and stayed within a few hundred feet of the ground, for example, the Mk1 and Mk2 will be powered by at least three Raptors and will go much higher.
SpaceX is aiming for a test flight that gets 12 miles (20 kilometers) up in October, followed by an orbital attempt “shortly thereafter,” Musk said late last month.
All of these steps are leading toward the final Starship, SpaceX’s planned Mars-colonizing craft. That Starship will be capable of carrying 100 passengers and will launch atop a huge rocket called the Super Heavy. Both of the elements, rocket and spaceship, will be fully and rapidly reusable, Musk has said.
The final Starship, as currently envisioned, will sport six Raptors, while the Super Heavy will be powered by 35 of the engines. Those numbers could change, however; Musk is scheduled to give a Starship design update on Sept. 28 from the South Texas site.
The Mk1 should be fully assembled by that time, he has said.
The Mk1 and Mk2 test campaigns won’t be terribly lengthy, if SpaceX’s planned schedules hold. Company representatives have said that the first operational flights of Starship, which are likely to be commercial satellite launches, could come as early as 2021. (Eventually, SpaceX plans to use Starship for all the company’s spaceflight needs, from interplanetary colonization missions to satellite launches to point-to-point trips around Earth.)
And SpaceX is targeting 2023 for a crewed mission of the vehicle: a flight around the moon booked by Japanese billionaire Yusaku Maezawa.
When ‘Oumuamua passed through our Solar System two years ago, it set off a flurry of excitement in the astronomical community. Here was the first-ever interstellar object that be observed by human trackers, and the mysteries surrounding its true nature and composition led to some pretty interesting theories. There were even some proposals for a rapid mission that would be able to rendezvous with it.
And now that a second interstellar object – C/2019 Q4 (Borisov) – has been detected traveling through the Solar System, similar proposals are being made. One of them comes from a group of scientists from the Initiative for Interstellar Studies (i4is) in the UK. In a recent study, they assess the technical feasibility of sending a mission to this interstellar comet using existing technology, and found that there were a few options!
In many ways, C/2019 Q4 (Borisov) represents an opportunity to conduct the kinds of research that were not possible with ‘Oumuamua. When that mystery object was first observed, it had already made its closest pass to the Sun, past Earth, and was on its way out of the Solar System. Nevertheless, what we were able to learn about ‘Oumuamua led to the conclusion that it was an entirely new class of celestial object.
In addition to those who ventured that it was either a comet or an asteroid, there were also those who theorized that ‘Oumuamua could be a fragment from a comet that exploded when passing close to our Sun, or even an extra-terrestrial solar sail. Another interesting find was the fact that similar objects likely pass through our Solar System on a regular basis (many of which stay).
For these reasons, a mission that could study such objects up close is very desirable. As Dr. Andreas M. Hein – the executive director of i4is’s board of directors, the chairman of its Technical Research Committee, and one of the co-authors on the recent study – told Universe Today via email:
“Investigating interstellar objects from a close distance would provide us with unique data about other star systems without actually flying to them. They might provide unique insights into the evolution and composition of other star systems and exoplanets in them. Interstellar objects are cool as it’s a bit like: If you can’t go to the mountain, let the mountain come to you. It will likely take many decades until we can send a spacecraft to another star. Hence, interstellar objects might be an intermediate solution for finding out more about other stars and their planets.”
What’s more, he claims, these objects have probably been travelling between star system for hundreds of thousands (or even millions) of years. As a result, they undoubtedly picked up material along the way or bear the marks of encounters with other objects or forces. In short, their composition and surface features can tell us a great deal about what is out there in the interstellar medium.
The project was so-named because of ‘Oumuamua’s origins, which astronomers concluded came from the general direction of Vega – the brightest star in the northern constellation of Lyra. After taking into account the speed with which ‘Oumuamua was leaving the Solar System at the time – 26 km/s (93,600 km/h; 58,160 mph) – they determined that any proposal would be a trade-off between three factors.
These included when a mission could launch, the velocity it could achieve, and the time it would take to rendezvous with the object. Under the circumstances, they felt that the best option was to wait for future technological breakthroughs – such as those being pursued by Breakthrough Starshot (a concept for a laser-driven interstellar solar sail).
These conclusions have proven very applicable, thanks to the detection of a second interstellar object passing through our Solar System in as many years. In their most recent study, the research team once again used Optimum Interplanetary Trajectory Software (OITS) – which was developed by team-member Adam Hibberd – to assess all available options for sending a spacecraft to rendezvous with an interstellar object.
These included the optimal launch vehicle (like NASA’s Space Launch System (SLS) or SpaceX’s Falcon Heavy) the optimal trajectory for the mission, and the best type of spacecraft. In the end, they determined that humanity has the capability of rendezvousing with an interstellar object using existing technology and came up with a mission architecture that could make that happen.
This mission would rely on a heavy-launch vehicle and could alternately employ a 2 ton (1.8 metric ton) or a 3 kg (6.6 lbs) CubeSat spacecraft. Depending on when it launched and what its preferred trajectory would be, it might also need to conduct a Jupiter flyby and Solar Oberth maneuver to catch up with C/2019 Q4 (Borisov). As Dr. Hein explained:
“Our results show that for both, ‘Oumuamua and C/2019 Q4 (Borisov), we already have the technology to visit these objects. Regarding ‘Oumuamua, we can launch a spacecraft towards it even beyond the year 2030. There is plenty of time to develop such a spacecraft. The case for C/2019 Q4 (Borisov) is a bit more tricky, as it is faster than ‘Oumuamua. But even for this object, we could have sent a two-ton spacecraft to it with a Falcon Heavy, if we would have launched it in 2018.”
“Later missions are also possible, but require a bigger launcher. Future telescopes will be able to detect such objects much earlier and with adequate preparation, we can send a spacecraft on an encounter mission. So we have the technology to do this and with the discovery of C/2019 Q4 (Borisov), we also know that we probably have plenty of opportunities to fly to such an object.”
Once again, the presence of an interstellar object in our Solar System is a major source of excitement. In addition to all the opportunities to learn from them, C/2019 Q4 and ‘Oumuamua are encouraging because of the implication their presence has. Not only do they confirm that objects from distant stars pass through our System pretty regularly; they also show that we are at a point where we can detect, track and study them.
But knowing that in the future, we will be able to study them up close is especially exciting! In fact, the ESA is currently working on a mission that could very be the one to rendezvous with a future interstellar object. It’s known as the Comet Interceptor, a “fast-class” concept consisting of three spacecraft that will wait in space until a pristine comet appears, rapidly catch up with it!
“We imagine two types of research,” Dr. Hein said. “First, remote-sensing, for example with a telescope taking pictures. Second, we can analyze material from the object directly by shooting an impactor into it and catching some of the particles from the dust plume which is generated with the main spacecraft. This would provide unique insights into the composition of the object.”
As for what this research could reveal, Dr. Hein has some thoughts on that too: “I can only speculate but we might see evidence that organic molecules, the building blocks for life, actually travel between star systems and who knows, maybe life itself might actually spread between stars in our galaxy.”
KATRIN’s spectrometer, shown here, precisely measures the energy of electrons emitted in the decay of tritium, which has helped scientists come closer to pinning down the mass of the ghost-like neutrino. Credit: The KATRIN Collaboration
Joseph Formaggio explains the discovery that the ghostly particle must be no more than 1 electronvolt, half as massive as previously thought.
An international team of scientists, including researchers at MIT, has come closer to pinning down the mass of the elusive neutrino. These ghost-like particles permeate the universe and yet are thought to be nearly massless, streaming by the millions through our bodies while leaving barely any physical trace.
The researchers have determined that the mass of the neutrino should be no more than 1 electron volt. Scientists previously estimated the upper limit of the neutrino’s mass to be around 2 electron volts, so this new estimate shaves down the neutrino’s mass range by more than half.
The new estimate was determined based on data taken by KATRIN, the Karlsruhe Tritium Neutrino Experiment, at the Karlsruhe Institute of Technology in Germany, and reported at the 2019 Conference on Astroparticle and Underground Physics last week. The experiment triggers tritium gas to decay, which in turn releases neutrinos, along with electrons. While the neutrinos are quick to dissipate, KATRIN’s sequence of magnets directs tritium’s electrons into the heart of the experiment — a giant 200-ton spectrometer, where the electrons’ mass and energy can be measured, and from there, researchers can calculate the mass of the corresponding neutrinos.
Joseph Formaggio, professor of physics at MIT, is a leading member of the KATRIN experimental group, and spoke with MIT News about the new estimate and the road ahead in the neutrino search.
Q: The neutrino, based on KATRIN’s findings, can’t be more massive than 1 electron volt. Put this context for us: How light is this, and how big a deal is it that the neutrino’s maximum mass could be half of what people previously thought?
A: Well, that’s somewhat of a difficult question, since people (myself included) don’t really have an intuitive sense of what the mass is of any particle, but let’s try. Consider something very small, like a virus. Each virus is made up of roughly 10 million protons. Each proton weighs about 2,000 times more than each electron inside that virus. And what our results showed is that the neutrino has a mass less than 1/ 500,000 of a single electron!
Let me put it another way. In each cubic centimeter of space around you, there are about 300 neutrinos zipping through. These are remnants of the early universe, just after the Big Bang. If you added up all the neutrinos residing inside the sun, you’d get about a kilogram or less. So, yeah, it’s small.
Q: What went into determining this new mass limit for the neutrino, and what was MIT’s role in the search?
A: This new mass limit comes from studying the radioactive decay of tritium, an isotope of hydrogen. When tritium decays, it produces a helium-3 ion, an electron, and an antineutrino. We actually never see the antineutrino, however; the electron carries information about the neutrino’s mass. By studying the energy distribution of the electrons ejected at the highest energies allowed, we can deduce the mass of the neutrino, thanks to Einstein’s equation, E=mc2.
However, studying those high-energy electrons is very difficult. For one thing, all the information about the neutrino is embedded in a tiny fraction of the spectrum — less than 1 billionth of decays are of use for this measurement. So, we need a lot of tritium inventory. We also need to measure the energy of those electrons very, very precisely. This is why the KATRIN experiment is so tricky to build. Our very first measurement presented today is the culmination of almost two decades of hard work and planning.
MIT joined the KATRIN experiment when I came to Boston in 2005. Our group helped develop the simulation tools to understand the response of our detector to high precision. More recently, we have been involved in developing tools to analyze the data collected by the experiment.
Q: Why does the mass of a neutrino matter, and what will it take to zero in on its exact mass?
A: The fact that neutrinos have any mass at all was a surprise to many physicists. Our earlier models predicted that the neutrino should have exactly zero mass, an assumption dispelled by the discovery that neutrinos oscillate between different types. That means we do not really understand the mechanism responsible for neutrino masses, and it is likely to be very different than how other particles attain mass. Also, our universe is filled with primordial neutrinos from the Big Bang. Even a tiny mass has a significant impact on the structure and evolution of the universe because they are so aplenty.
This measurement represents just the beginning of KATRIN’s measurement. With just about one month of data, we were able to improve previous experimental limits by a factor of two. Over the next few years, these limits will steadily improve, hopefully resulting in a positive signal (rather than just a limit). There are also a number of other direct neutrino mass experiments on the horizon that are also competing to reach greater sensitivity, and with it, discovery!