Astronomers have found a new crop of moons around Jupiter, and one of them is a weirdo
Ten more moons have been confirmed to orbit around Jupiter, bringing the planet's total known satellite count to 79. That's the highest number of moons of any planet in the Solar System. And these newly discovered space rocks are giving astronomers insight as to why the Jupiter system looks like it does today.
Astronomers at Carnegie Institution for Science first found these moons in March 2017, along with two others that were already confirmed in June of last year. The team initially found all 12 moons using the Blanco 4-meter telescope in Chile, though finding these objects wasn't their main goal. Instead, they were searching for incredibly distant small objects — or even planets — that might be lurking in our Solar System beyond Pluto. But as they searched for these fringe space rocks, they decided to take a peek at what might be lurking around Jupiter at the same time. Now, the moons they found have been observed multiple times, and their exact orbits have been submitted for approval from the International Astronomical Union, which officially recognizes celestial bodies.
These moons are all pretty tiny, ranging between less than a mile and nearly two miles wide. And they break down into three different types. Two orbit closer to Jupiter, moving in the same direction that the planet spins. Farther out from those, about 15.5 million miles from the planet, there are nine that rotate in the opposite direction, moving against Jupiter's rotation. But in this same distant region, one strange moon that astronomers are calling Valetudo is moving with Jupiter's spin, like the two inner moons.
Previously: Two Tiny New Moons Found Around Jupiter
Related: Retrograde Jupiter Co-Orbital Asteroid May Have an Interstellar Origin
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Related Stories
A survey searching for objects in the Kuiper Belt has found two undiscovered moons of Jupiter. Jupiter now has 69 known moons:
Until recently the cataloged satellites totaled 67 in number. But only the innermost 15 of these orbit Jupiter in a prograde sense (in the direction of the planet's spin). The rest are retrograde, and are likely captured objects - other pieces of the solar system's solid inventory that strayed into Jupiter's gravitational grasp.
That population of outer moons is mostly small stuff, only a few are 20-60 kilometers in diameter, most are barely 1-2 kilometers in size, and increasingly difficult to spot. Now astronomers Scott Sheppard, David Tholen, and Chadwick Trujillo have added two more; bringing Jupiter's moon count to 69.
These additions are also about 1-2 km in size, and were spotted in images that were part of a survey for much more distant objects out in the Kuiper Belt. Jupiter just happened to be conveniently close in the sky at the time. The moons are S/2016 J1 and S/2017 J1, and are about 21 million km and 24 million km from Jupiter.
The moons are also known as Jupiter LIV and Jupiter LIX, and are members of the Pasiphae group. They are estimated to be about 3 and 2 km in diameter respectively.
Also at Popular Mechanics.
2015 BP519, nicknamed "Caju", is another extreme trans-Neptunian object that points to the existence of Planet Nine. Discovered with data from the Dark Energy Survey, Caju has a relatively large diameter, estimated at around 400-700 km, meaning the object could be a gravitationally rounded dwarf planet. It also has a highly inclined orbit of 54°, which a team of scientists says can be explained by the presence of the hypothetical Planet Nine:
After discovering it, the team tried to investigate 2015 BP519's origins using computer simulations of the Solar System. However, these tests were not able to adequately explain how the object had ended with such an orbit.
But when the team added a ninth planet with properties exactly matching those predicted by the Caltech scientists in 2016, the orbit of 2015 BP519 suddenly made sense. "The second you put Planet Nine in the simulations, not only can you form objects like this object, but you absolutely do," Juliette Becker, a Michigan graduate student and lead author of the study told Quanta.
Some researchers, however, caution that Planet Nine may not be the only explanation for 2015 BP519's strange orbit. Michele Bannister, a planetary astronomer from Queen's University Belfast, in Ireland, who was not involved in the study, told Newsweek that while the latest findings were "a great discovery," other scenarios could account for its tilt. "This object is unusual because it's on a high inclination," she said. "This can be used to maybe tell us some things about its formation process. There are a number of models that suggest you can probably put objects like this into the shape of orbit and the tilt of orbit that we see today."
Also at Quanta Magazine.
Discovery and Dynamical Analysis of an Extreme Trans-Neptunian Object with a High Orbital Inclination (arXiv:1805.05355)
Related: Medieval Records Could Point the Way to Planet Nine
Astronomers have posited an interstellar origin for (514107) 2015 BZ509, the first example of a retrograde co-orbital asteroid with one of the solar system's planets (Jupiter):
An asteroid in Jupiter's orbit [Note: actually orbiting the Sun and crossing the orbit of Jupiter] may have come from outside our Solar System, according to a new study. Unlike 'Oumuamua, the interstellar object which briefly visited the Solar System earlier this year, 2015 BZ509 (affectionately known as BZ) seems to have been here for 4.5 billion years. This makes it the first known interstellar asteroid to have taken up residence orbiting the Sun.
It is not yet known where the object came from. "That's what we need to figure out next," laughs Dr Fathi Namouni from the Universite Cote d'Azur, one of the study's authors. "Because 'Oumuamua was just passing by... it's not that difficult to go back and pinpoint where it came from," he told BBC News. "BZ reached the Solar System when it was forming, when the planets themselves were not exactly where they are now. So it's a little more tricky to figure out where it came from."
Also at Scientific American, Science News, EarthSky, and CNN.
An interstellar origin for Jupiter's retrograde co-orbital asteroid (open, DOI: 10.1093/mnrasl/sly057) (DX)
Related: Possible Interstellar Asteroid/Comet Enters Solar System
Interstellar Asteroid Named: 'Oumuamua
ESO Observations Show First Interstellar Asteroid is Like Nothing Seen Before
Breakthrough Listen to Observe Interstellar Asteroid 'Oumuamua for Radio Emissions (none were found)
'Oumuamua Likely Originated in the Local Association (Pleiades Moving Group)
Collective gravity, not Planet Nine, may explain the orbits of 'detached objects'
Bumper car-like interactions at the edges of our solar system—and not a mysterious ninth planet—may explain the the dynamics of strange bodies called "detached objects," according to a new study. CU Boulder Assistant Professor Ann-Marie Madigan and a team of researchers have offered up a new theory for the existence of planetary oddities like Sedna—an icy minor planet that circles the sun at a distance of nearly 8 billion miles. Scientists have struggled to explain why Sedna and a handful of other bodies at that distance look separated from the rest of the solar system. [...] The researchers presented their findings today at a press briefing at the 232nd meeting of the American Astronomical Society, which runs from June 3-7 in Denver, Colorado.
[...] [Jacob] Fleisig had calculated that the orbits of icy objects beyond Neptune circle the sun like the hands of a clock. Some of those orbits, such as those belonging to asteroids, move like the minute hand, or relatively fast and in tandem. Others, the orbits of bigger objects like Sedna, move more slowly. They're the hour hand. Eventually, those hands meet. "You see a pileup of the orbits of smaller objects to one side of the sun," said Fleisig, who is the lead author of the new research. "These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape." In other words, Sedna's orbit goes from normal to detached, entirely because of those small-scale interactions.
Also at Popular Mechanics, where Planet Nine proposer Konstantin Batygin disputes the findings:
Batygin, of Caltech, tells Popular Mechanics that any sufficiently strong gravitational encounter could detach an object from Neptune's embrace, but for the distant small bodies of the Kuiper belt to have done so through "self-gravity"—as the CU model proposes—there would need to be about five to ten times the mass of Earth in the outer parts of the Kuiper belt. There isn't.
"Unfortunately, the self-gravity story suffers from the following complications," Batygin says. "Both observational and theoretical estimates place the total mass of the Kuiper belt at a value significantly smaller than that of the Earth [only 1 to 10 percent Earth's mass]. As a consequence, Kuiper belt objects generally behave like test-particles enslaved by Neptune's gravitational pull, rather than a self-interacting group of planetoids."
Related: Planet Nine's Existence Disfavoured by New Data
Medieval Records Could Point the Way to Planet Nine
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
Outer Solar System Origins Survey Discovers Over 800 Trans-Neptunian Objects
LSST Could be the Key to Finding New Planets in Our Solar System
Planet Nine: 'Insensitive' Term Riles Scientists
The International Astronomical Union (IAU) famously reclassified Pluto as a "dwarf planet" in 2006. That decision remains highly controversial today, as made clear by the new note, which appeared in the July 29 issue of the Planetary Exploration Newsletter.
The note:
ON THE INSENSITIVE USE OF THE TERM "PLANET 9" FOR OBJECTS BEYOND PLUTO
We the undersigned wish to remind our colleagues that the IAU planet definition adopted in 2006 has been controversial and is far from universally accepted. Given this, and given the incredible accomplishment of the discovery of Pluto, the harbinger of the solar system's third zone — the Kuiper Belt — by planetary astronomer Clyde W. Tombaugh in 1930, we the undersigned believe the use of the term 'Planet 9' for objects beyond Pluto is insensitive to Professor Tombaugh's legacy.
We further believe the use of this term should be discontinued in favor of culturally and taxonomically neutral terms for such planets, such as Planet X, Planet Next, or Giant Planet Five.
35 researchers signed the note, including Alan Stern, principal investigator of the New Horizons mission.
Of more interest may be this proposal concerning future exploration of Uranus and Neptune:
Related: Uranus and Neptune Are Potential Targets for 2030s Missions
Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine Search Turns Up 10 More Moons of Jupiter
The search for Planet X gets a boost with the discovery of a super distant object
A new discovery is strengthening the idea that a large, mysterious planet — known as Planet 9 or Planet X — may be lurking unseen at the Solar System's edge. Astronomers say they have found a tiny object orbiting far out from the Sun that fits with the Planet X theory. In fact, the object may have even been pushed onto the path it takes now by this hidden planet's gravity.
The tiny rock — eloquently named TG387 and nicknamed "The Goblin" — was spotted by astronomers at the Carnegie Institution of Science using a giant Japanese observatory in Hawaii called Subaru. The Carnegie team first spotted the object in 2015 and then followed it on its journey around the Sun for the last four years. Those observations revealed an incredibly distant target. TG387 takes a whopping 40,000 years to complete just one orbit around the Sun. And it's on a very elliptical path far from the inner Solar System; the closest it ever gets to the Sun is 65 Astronomical Units (AU), or 65 times the distance between the Sun and the Earth. For reference, Pluto only gets as far as 49 AUs from the Sun.
This orbit is particularly enticing since it puts TG387 in a select group of distant Solar System objects that all point to the possible existence of Planet X. Right now, there are 14 far-out space rocks that all share similar orbit patterns, suggesting that this planet is out there. Their paths are all super elongated, and they all cluster together in the same area when they approach the Sun. Plus, their orbits are all tilted alike, and they point in the same general direction, as if something big has pushed them into similar places. These objects are the strongest lines of evidence astronomers have for Planet X, and finding a new one that matches this pattern reinforces that idea that this planet is more than just a theory.
Planet Nine and 2015 TG387.
Also at ScienceAlert, The Atlantic, USA Today, and NPR.
A New High Perihelion Inner Oort Cloud Object
Previously: Another Trans-Neptunian Object With a High Orbital Inclination Points to Planet Nine
CU Boulder Researchers Say Collective Gravity, Not Planet Nine, Explains Orbits of Detached Objects
Planet Nine Search Turns Up 10 More Moons of Jupiter
Where *Isn't* Planet 9? Search for Planet Nine still continues
Not long ago astronomers Mike Brown and Konstantin Batygin (the two original people proposing the existence of the planet) used the alignments of the TNO orbits to back-calculate the potential location of the unseen planet in space. It's a kind of treasure map to find the planet.
In a new paper they've put that map to use, looking through survey data in a hunt for Planet 9.
[...] Brown and Batygin wrote software that simulates where Planet 9 would be and how bright it would appears for various values of its size, reflectivity, and orbital shape. They created a database of positions and brightnesses for it, and then combed through the [Zwicky Transient Facility (ZTF)] database to look for it, going through the past three or so years of observations since the facility started its survey campaign.
[...] They ran 100,000 simulations of various parameters for the planet, and looked to see if the ZTF would've seen it if it were indeed smaller and closer to us. They determined that it would've been seen in the survey about 56,000 times out of the 100,000, so just looking at that their non-detection indicates the chance it's smaller and closer is now less than 50%, making it more likely it's farther out, bigger, and fainter.
The larger Vera C. Rubin Observatory is expected to find many previously hidden objects in the solar system, and is scheduled to begin full operations in October 2023. It will accumulate all-sky survey data around 10 times faster than the Zwicky Transient Facility.
Also at ExtremeTech.
(Score: 2) by Arik on Wednesday July 18 2018, @05:51AM (1 child)
And now they're waiting to hear whether they are approved or not. Should the IAU disapprove them, they shall be forced to immediately and retroactively de-orbit. Just like Pluto did.
Oh, wait...
If laughter is the best medicine, who are the best doctors?
(Score: 2) by bob_super on Wednesday July 18 2018, @06:26PM
Considering that one is moving against local traffic, some de-orbiting or collision is likely to happen within hundreds to millions of years, long before the US Congress provides an opinion on any matter.
The IAU is barely faster.
(Score: 2, Troll) by realDonaldTrump on Wednesday July 18 2018, @02:47PM
Saturn, very famous for the rings. Amazing thing, they're not solid. I hear they're not solid, they're little pieces of stuff just floating there. In space. And possibly there are thousands of pieces. Can we call it moons? Why not?