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Here’s How Interstellar Objects and Rogue Planets Can be Trapped in the Solar System
When Oumuamua traversed our Solar System in 2017 it was the first confirmed Interstellar Object (ISO) to do so. Then in 2019, Comet 2l/Borisov did the same thing. These are the only two confirmed ISOs to visit our Solar System. Many more ISOs must have visited in our Solar System’s long history, and many more will visit in the future. There are obviously more of these objects out there, and the upcoming Vera Rubin Observatory is expected to discover many more.
It’s possible that the Sun could capture an ISO or a rogue planet in the same way that some of the planets have captured moons.
It all comes down to phase space.
What would happen to our mature, sedate Solar System if it suddenly gained another member? That would depend on the object’s mass and the eventual orbit that it found itself in. It’s an interesting thought experiment; while Borisov and Oumuamua were smaller objects, a more massive rogue planet joining our Solar System could generate orbital chaos. It could potentially alter the course of life on Earth, though that is highly improbable.
How likely is this scenario? A new research note in Celestial Mechanics and Dynamical Astronomy outlines how our Solar System could capture an ISO. It’s titled “Permanent capture into the solar system,” and the authors are Edward Belbruno from the Department of Mathematical Sciences at Yeshiva University, and James Green, formerly of NASA and now from Space Science Endeavours.
Phase space is a mathematical representation that describes the state of a dynamical system like our Solar System. Phase space uses coordinates that represent both position and momentum. It’s like a multidimensional space that contains all of the possible orbital configurations around the Sun. Phase space captures the state of a dynamical system by tracking both position and momentum characteristics. Our Solar System’s phase space has capture points where an ISO can find itself gravitationally bound to the Sun.
Phase space is complex and is based on Hamiltonian mechanics. Things like orbital eccentricity, semi-major axis, and orbital inclination all feed into it. Phase space is best understood as a multidimensional landscape.
Our Solar System’s phase space includes two types of capture points: weak and permanent.
Weak capture points are regions in space where an object can be temporarily drawn into a semi-stable orbit. These points are often where the outer edges of objects’ gravitational boundaries meet. They’re more like gravitational nudges than an orbital adoption.
Permanent capture points are regions in space where an object can be permanently captured into a stable orbit. An object’s angular momentum and energy are an exact configuration that allows it to maintain an orbit. In planetary systems, these permanent capture points are stable orbital configurations that persist for extremely long periods of time.
Our Solar System’s phase space is extremely complex and involves many moving bodies and their changing coordinates. Subtle changes in phase space coordinates can allow objects to transition between permanent capture states and weak capture states. By the same token, subtle differences in ISOs or rogue planets can lead them into these points.
In their research note, the authors describe the permanent capture of an ISO this way: “The permanent capture of a small body, P, about the Sun, S, from interstellar space occurs when P can never escape back into interstellar space and remains captured within the Solar System for all future time, moving without collision with the Sun.” Purists will note that nothing can be the same for all future time, but the point stands.
Other researchers have delved into this scenario, but this work goes a step further. “In addition to being permanently captured, P is also weakly captured,” they write. It revolves around the notoriously difficult to solve three-body problem. Also unlike previous research, which uses Jupiter as the third body, this work uses the galaxy’s tidal force as the third body, along with the P and S. “This tidal force has an appreciable effect on the structure of the phase space for the velocity range and distance from the Sun we are considering,” they explain in their paper.
The paper focuses on the theoretical nature of phase space and ISO capture. It studies “the dynamical and topological properties of a special type of permanent capture, called permanent weak capture which occurs for infinite time.” An object in permanent weak capture will never escape, but will never reach a consistent stable orbit. It asymptotically approaches the capture set without colliding with the star.
There’s not much debate that rogue planets exist likely in large numbers. Stars form in groups that eventually disperse over a wider area. Since stars host planets, some of these planets will be dispersed through gravitational interactions prior to co-natal stars gaining some separation from one another.
“The final architecture of any solar system will be shaped by planet-planet scattering in addition to the stellar flybys of the adjacent forming star systems since close encounters can pull planets and small bodies out of the system creating what are called rogue planets,” the authors explain.
“When taken together, planet ejection from early planet-planet scattering and stellar encounters and in the subsequent evolution of a multi-planet solar system should be common and supports the evidence for a very large number of rogue planets that are free floating in interstellar space that perhaps exceed the number of stars,” the authors write, noting that that assertion is controversial.
So what does this all add up to?
The researchers developed a capture cross-section for the Solar System’s phase space then calculated how many rogue planets are in our Solar System’s vicinity. In our solar neighbourhood, which extends to a radius of six parsecs around the Sun, there are 131 stars and brown dwarfs. Astronomers know that at least several of them host planets, and all of them may very well host planets we haven’t detected yet.
Every million years, about two of our stellar neighbours come within a few light years of Earth. “However, six stars are expected to closely pass by in the next 50,000 years,” the authors write. The Oort Cloud’s outer boundary is about 1.5 light years away, so some of these stellar encounters could easily dislodge objects from the cloud and send them toward the inner Solar System. This has already happened many times, as the cloud is likely the source of long-period comets.
The familiar Solar System with its 8 planets occupies a tiny space inside a large spherical shell containing trillions of comets – the Oort Cloud. Gravitational perturbations dislodge comets from the cloud, sending some of them into the inner Solar System. Image Credit: Wikimedia CommonsThe researchers identified openings in the Solar System’s phase space that could allow some of these objects, or ISOs or rogue planets, to reach permanent weak capture. They’re openings in the Sun’s Hill sphere, a region where the Sun’s gravity is the dominant gravitational force for capturing satellites. These openings are 3.81 light years away from the Sun in the direction of the galactic center or opposite to it.
“Permanent weak capture of interstellar objects into the Solar System is possible through these openings,” the authors state. “They would move chaotically within the Hill’s sphere to permanent capture about the Sun taking an arbitrarily long time by infinitely many cycles.” These objects would never collide with the Sun and could be captured permanently. “A rogue planet could perturb the orbits of the planets that may be possible to detect,” they conclude.
We’re still in the early days of understanding ISOs and rogue planets. We know they’re out there, but we don’t know how many or where they are. The Vera Rubin Observatory might open our eyes to this population of objects. It may even show how they cluster in some regions and avoid others.
According to this work, if they’re close to any of the openings in the Sun’s Hill sphere, we could have a visitor that decides to stay.
The post Here’s How Interstellar Objects and Rogue Planets Can be Trapped in the Solar System appeared first on Universe Today.
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NASA Leadership to Provide Update on Artemis Campaign
Lee esta nota de prensa en español aquí.
NASA Administrator Bill Nelson and leadership will hold a news conference at 1 p.m. EST, Thursday, Dec. 5, at the agency’s headquarters in Washington to provide a briefing about the agency’s Artemis campaign.
Watch the media event on NASA+. Learn how to stream NASA content through a variety of platforms, including social media.
Participants include:
- NASA Administrator Bill Nelson
- NASA Deputy Administrator Pam Melroy
- NASA Associate Administrator Jim Free
- Catherine Koerner, associate administrator, Exploration Systems Development Mission Directorate, NASA Headquarters
- Amit Kshatriya, deputy associate administrator, Moon to Mars Program Office, Exploration Systems Development Mission Directorate
- Reid Wiseman, NASA astronaut and Artemis II commander
Media interested in participating in-person or by phone must RSVP by 11 a.m. on Dec. 5 to: hq-media@mail.nasa.gov. The news conference will take place in the James E. Webb Auditorium at NASA Headquarters in the Mary W. Jackson building, 300 E St. SW, Washington. A copy of NASA’s media accreditation policy is online.
Through the Artemis campaign, the agency will establish a long-term presence at the Moon for scientific exploration with our commercial and international partners, learn how to live and work away from home, and prepare for future human exploration of Mars. NASA’s SLS (Space Launch System) rocket, exploration ground systems, and Orion spacecraft, along with the human landing systems, next-generation spacesuits, Gateway lunar space station, and future rovers are NASA’s foundation for deep space exploration.
For more information about Artemis, visit:
-end-
Meira Bernstein / Rachel Kraft
Headquarters, Washington
202-358-1600
meira.b.bernstein@nasa.gov / rachel.h.kraft@nasa.gov
MeerKAT Confirms the Gravitational Wave Background of the Universe in Record Time
The Universe is a turbulent place. Stars are exploding, neutron stars collide, and supermassive black holes are merging. All of these things and many more create gravitational waves. As a result, the cosmos is filled with a rippling sea of gravitational vibrations. While we have been able to directly detect gravitational waves since 2016, gravitational wave astronomy is still in its infancy. We have only been able to observe the gravitational ripples of colliding stellar black holes. Even then, all we can really detect is the final gravitational chirp created in the last moments of merging.
We can, however, gather indirect evidence of the cosmic background of gravitational waves. Last year, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) released their first observations, which were based on millisecond pulsars.
The idea behind the NANOGrav project is that pulsars emit very regular radio pulses. Millisecond pulsars are just rapidly rotating neutron stars that happen to sweep a beam of radio energy in our direction with each rotation. So, unless a neutron star experiences a rare starquake, the pulsar timing is so consistent we can use it as a cosmic clock. This means any small variation in the timing is due to a change in relative motion. As the cosmic gravitation waves ripple past a pulsar, its observed timing changes slightly. The shift isn’t large enough to observe with an individual pulsar, but it is large enough that a statistical analysis of many pulsars reveals the gravitational waves.
MeerKAT results showing pulsar correlations across the sky. Credit: Miles, et alIn the 2023 results, NANOGrav found evidence of cosmic gravitational waves but didn’t have enough data to pin down the source. But even this was a tremendous result. It took 15 years of observations just to prove the existence of these cosmic waves. Now a new observatory has released a data set, and it’s a game changer.
The MeerKat radio array is a collection of 64 antennas located in South Africa and run by the South African Radio Astronomy Observatory (SARAO). This week, SARAO released a series of papers on their results after just four and a half years. Where NANOGrav looked at 67 millisecond pulsars, MeerKAT gathered data on 83. It observed these pulsars with a similar resolution as NANOGrav, but did so in a third of the time. These results again confirm the existence of cosmic gravitational waves, but like the NANOGrav don’t confirm the origin. We still need more data to prove they are generated by binary black holes. But now that we have two observational teams working on it, that necessary evidence should be found in the relatively near future.
Reference: Agazie, Gabriella, et al. “The NANOGrav 15 yr data set: Evidence for a gravitational-wave background.” The Astrophysical Journal Letters 951.1 (2023): L8.
Reference: Miles, Matthew T., et al. “The MeerKAT Pulsar Timing Array: The 4.5-year data release and the noise and stochastic signals of the millisecond pulsar population.” Monthly Notices of the Royal Astronomical Society (2024): stae2572.
Reference: Miles, Matthew T., et al. “The MeerKAT Pulsar Timing Array: The first search for gravitational waves with the MeerKAT radio telescope.” Monthly Notices of the Royal Astronomical Society (2024): stae2571.
Reference: Grunthal, Kathrin, et al. “The MeerKAT pulsar timing array: Maps of the gravitational-wave sky with the 4.5 year data release.” Monthly Notices of the Royal Astronomical Society (2024): stae2573.
The post MeerKAT Confirms the Gravitational Wave Background of the Universe in Record Time appeared first on Universe Today.
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Hawaiian Crows Return to the Wild, Where They Are ‘Guides to Souls’
The Hawaiian crow, or ‘alalā, has been extinct in the wild since 2002. A new effort to reintroduce birds of this species—considered important guides to the souls of the dead in Hawaiian tradition—is underway