A new paper just published claims that some members of a group of odd objects called centaurs may actually be bodies captured by the Sun from other stars when the solar system was very young. It’s a followup work the same pair of astronomers did where they claimed that a very weird asteroid orbiting near Jupiter was also of interstellar origins.
If true, it’s a very big deal! We’d have samples of objects born around other stars just waiting for us to go and take a look at them. That’s terribly exciting. I’ve seen it getting covered on quite a few news sites, too.
But is it true? Well, it might be, but I’m pretty skeptical (and, to be fair, I was pretty skeptical about their earlier claim about the other weird asteroid as well). To understand why, we need to take a look at these objects, and what the astronomers did.
Centaurs are so named because they’re like half asteroid, half comet. They’re rocky iceballs (or icy rockballs) that orbit the Sun, and, similar to comets, they live far out from the Sun on elliptical orbits, but similar to asteroids their orbits take them in between the orbits of the giant outer planets.
The problem is that, for a small set of them — just 19 — no one knows how they got there. The ones in this group have weird orbits that are highly inclined to the plane of the solar system, and some of them even orbit the Sun retrograde (backward relative to the direction the planets revolve). Either they always had orbits like that, or they somehow started off with normal orbits and got kicked into those weird configurations by getting too close to a planet, which warped their paths.
The thing there is, with the eight major planets we have, there’s just no way interactions would be able to send those centaurs into those odd orbits. Starting with that assumption, the astronomers decided to use a computer simulation to run the orbits of these objects backward in time, to see if they could glean their origin stories. To do this, they use what’s amusingly called a clone swarm: They run the simulation on a million objects that have very similar but not exactly the same orbits as the known objects. We don’t know the orbits of the centaurs precisely, and small changes in the orbit now can mean big changes over billions of years. This kind of simulation accounts for that, allowing you to look at things statistically. A million is a big sample, and gives you a good idea of how changes propagate.
What they found is that in every case, stable orbits exist that go back 4.5 billion years to the beginning of the solar system! From there, they conclude that the objects were therefore in those orbits for that long, and therefore could not have formed with the solar system. They must be alien — formed around another star, and captured into these weird orbits in a close encounter between that star (or stars) and the Sun.
But hang on a sec! Just because stable orbits exist doesn’t mean those centaurs have been in them that long. Also, in every case, only a handful of the clones were able to survive all this time. For the most part, 99.99% of the clones were either ejected from the solar system or crashed into the Sun or a planet, leaving only a few dozen potential stable orbits out of a million. To me that argues that it’s incredibly unlikely these objects survived that long in these orbits! If they were stripped from another star, there would have to be hundreds of thousands of them stolen just so the few we see can make it. That strikes me as unlikely.
Also, there’s another explanation. In a paper published in 2016, a different pair of astronomers* looked at a more local solution to the centaurs. They think there is another, as yet undiscovered, planet orbiting the Sun way out past Neptune, due to the way a lot of small icy bodies out past Neptune appear to have their orbits aligned. A large planet gravitationally tugging on these objects can solve that mystery, and they’ve been looking for “Planet Nine” for some time now.
In their paper they propose that Planet Nine explains the weird centaurs as well. They ran some simulations and found that interactions with this planet slowly affect the orbits of objects, pumping up their orbital inclination, and even driving some to become retrograde. In fact, two of the objects (2011 KT19 and 2008 KV42) were also looked at by both teams, and both claim their method explains why these two objects have orbits nearly perpendicular to the plane of the inner solar system, a configuration that is very difficult to achieve.
So who’s right? Well, to be blunt, that’s not possible to say at this moment. It’s certainly possible the Sun could’ve stolen comets from another star, especially if we were born in a cluster of stars, which means there would be lots of close encounters between them. But the method they employ to show this in their paper … well, it doesn’t convince me. And it involves a stellar encounter or series of encounters we don’t have any evidence for. And the authors assume they have accounted for everything that could affect the centaurs, which is a difficult thing to do. Directly proving this idea is problematic, to say the least.
The Planet Nine idea doesn’t invoke stellar encounters, and uses a simulation method that is more established. You might argue that we don’t know if the planet even exists, which is fair, but this idea solves a lot of peculiar issues in the outer solar system. It’s like a Swiss Army Planet, a tool that can be used to make sense of many mysteries out there. That, to me, lends it credence.
The best (and probably fastest) way to solve this issue is to find the planet. Searches are underway, and if it exists it could be found in the next few years. Once the orbit of it is understood, the simulations could be rerun with more accurate numbers to see if it still explains things like the oddball centaurs.
And if no planet is found? Then that eliminates one possible explanation, and makes these centaurs even harder to explain. Perhaps it would lend more credence to the interstellar thievery idea. But even then, in my opinion, a better case still needs to be made.
*Full disclosure: One of the authors is Mike Brown, who is a friend of mine and to whom I spoke both about this recent work and the earlier one about the weird asteroid near Jupiter.
Astronomers Detect a Suspiciously Shaped Galaxy Lurking in The Very Early Universe
Around 13.8 billion years ago, somehow the Universe popped into existence. But it didn’t come fully equipped. At some point, the first stars formed, and the first galaxies. How and when this happened is still a mystery astronomers are trying to solve… but one galaxy could have a vitally important key.
It’s called DLA0817g – nicknamed the Wolfe Disk – a cool, rotating, gas-rich disc galaxy with a mass of about 72 billion times that of our Sun. And the Atacama Large Millimeter/submillimeter Array has snapped it a massive 12.5 billion light-years away – when the Universe was just 10 percent of its current age.
It’s the earliest rotating disc galaxy astronomers have found yet, and its very existence changes our understanding of galaxy formation in the early Universe.
Most of the galaxies in the early Universe are a hot mess, literally. They’re all blobby, with stars flying every which way, and rather high temperatures. Astronomers have interpreted this to mean that they grew large by colliding and merging with other galaxies – a hot, messy process.
“Most galaxies that we find early in the Universe look like train wrecks because they underwent consistent and often ‘violent’ merging,” explained astronomer Marcel Neeleman of the Max Planck Institute for Astronomy in Germany.
“These hot mergers make it difficult to form well-ordered, cold rotating disks like we observe in our present Universe.”
Under this scenario, it takes a long time for the galaxies to cool down and smooth out into the more orderly rotating disc galaxies like the Milky Way. We don’t generally start seeing them until about 4 to 6 billion years after the Big Bang.
This is the “hot” mode of galaxy formation. But astronomers had also predicted and simulated another way – the “cold” mode.
First, you need to start with the primordial soup, an ionised quark-gluon plasma that filled the Universe before the formation of matter. To go from this homogeneous plasma to a Universe filled with stuff, astrophysicists have run simulations that suggest dark matter is responsible.
We don’t know what dark matter is. We can’t detect it directly, but it interacts gravitationally with normal matter. It helps to hold galaxies together, and we believe that it could be crucial to galaxy formation, clumps of it pulling together gas and stars into galaxies.
Supercomputer simulations have shown that a massive network of dark matter in the early Universe could have facilitated the formation of cool galaxies. If the gas was cool to start with, it could have been fed along filaments of the network into the dark matter clumps, accreting into large, cool, orderly disc galaxies.
But the only way to confirm this model is through observational evidence, so the researchers went looking, using the light of even more distant galaxies, called quasars, to illuminate the way.
Distant galaxies are very hard to see, but quasars are among the most luminous objects in the Universe – galaxies lit by an active supermassive black hole, the space around it blasting out radiation as it feeds. The team turned ALMA’s powerful capabilities to these distant quasars, looking for signatures in their light that showed that it had passed through a gas-filled galaxy on the way.
They found it. The light from one of the quasars they imaged had passed through a region rich with hydrogen – the signature of the Wolfe Disk.
And there was something else. The light on one side of the disc was compressed, or blueshifted. We see this when something is moving towards us. And the light from the other side was stretched, or redshifted – moving away from us. The object was rotating.
Those Doppler shifts, as they are known, then allowed the researchers to calculate the velocity of the galaxy’s rotation: around 272 kilometres per second.
What’s even more wild is that the team believes the Wolfe Disk isn’t one of a kind.
“The fact that we found the Wolfe Disk using this method, tells us that it belongs to the normal population of galaxies present at early times,” Neeleman said.
“When our newest observations with ALMA surprisingly showed that it is rotating, we realised that early rotating disk galaxies are not as rare as we thought and that there should be a lot more of them out there.”
The team will continue their search for these galaxies to find out just how common cold accretion was in the early Universe.
The research has been published in Nature.
NASA’s head of human spaceflight abruptly resigns, citing ‘mistake’ – CNN
His departure was effective on Monday.
When reached by phone Tuesday evening, Loverro declined to comment on the reason for his departure.
Loverro began serving in his role as the head of NASA’s human spaceflight programs in December, replacing William Gerstenmaier, who served in the role for more than a decade. In his nearly 700-word note, Loverro told NASA workers only that leaders are “called on to take risks” and added that, “I took such a risk earlier in the year because I judged it necessary to fulfill our mission.”
“Now, over the balance of time, it is clear that I made a mistake in that choice for which I alone must bear the consequences,” Loverro wrote. “And therefore, it is with a very, very heavy heart that I write to you today to let you know that I have resigned from NASA effective May 18th, 2020.”
Ken Bowersox, NASA’s acting deputy associate administrator for human exploration and operations, will become NASA’s interim head of human spaceflight.
Loverro’s exit immediately raised some eyebrows on Capitol Hill.
Congresswoman Eddie Bernice Johnson, a Democrat from Texas who chairs the House space and science committee, said in a statement that she was “shocked” by the news.
“I trust that NASA Administrator Bridenstine will ensure that the right decision is made as to whether or not to delay the launch attempt,” Johnson said. “Beyond that, Mr. Loverro’s resignation is another troubling indication that the Artemis Moon-Mars initiative is still not on stable footing. I look forward to clarification from NASA as to the reasons for this latest personnel action.”
The timing of Loverro’s departure was related to when Jurczyk, the associate administrator, made a recommendation to NASA Administrator Jim Bridenstine, the source said. It was unrelated to next week’s Crew Dragon launch, the source added.
Jurczyk was the source selection officer for the Artemis lunar lander contract awards, according to public documents.
An agency-wide email sent on Tuesday said Loverro “hit the ground running” after his appointment in 2019 and had made “significant progress in his time at NASA.”
“His leadership of [NASA’s Human Exploration and Operations] has moved us closer to our goal of landing the first woman and the next man on the moon in 2024,” the email said. It said his resignation was effective immediately, though it did not provide details on the reason for his exit.
A NASA spokesperson declined to comment.
Loverro told CNN Business he is “100% confident” that leadership will be able to carry out the SpaceX mission. He added that he believes NASA’s ambitious human spaceflight goals are “doable.” “But,” he added, “it will take risk takers to get us there, and I hope folks who step in my shoes will continue to take risks.”
Next week’s SpaceX launch will mark the space agency’s highest-profile mission since the Space Shuttle program ended in 2011. SpaceX, which has a multibillion-dollar contract under NASA’s Commercial Crew Program, has worked for the better part of a decade to ready its Dragon spacecraft for crewed flights to the International Space Station. Since the Shuttle retired, NASA has had to rely on Russia for rides to the ISS.
In an orange swirl, astronomers say humanity has its first look at the birth of a planet
An image of a mesmerizing cosmic spiral, twisting and swirling around a galactic maw, may be the first direct evidence of the birth of a planet ever captured by humanity.
The European Southern Observatory released a picture Wednesday of what astronomers believe shows the process of cosmic matter at a gravitational tipping point, collapsing into a new world around a nearby star.
Astronomers said the dramatic scene offers a rare glimpse into the formation of a baby planet, which could help scientists better understand how planets come to exist around stars.
“Thousands of exoplanets have been identified so far, but little is known about how they form,” the lead author of a study detailing the discovery, Anthony Boccaletti, an astronomer at the Observatoire de Paris in France, said in a statement.
Planets are thought to form out of the massive discs of gas and dust that surround young stars. As tiny specks of dust circle a star and collide with one another, some material starts to fuse, much like how rolling a snowball through more snow will eventually yield a bigger snowball. After billions of years, the clumps of material become large enough that the force of gravity shapes them into planets.
The new image peers into the disc of material around a young star known as AB Aurigae, which is 520 light-years from Earth in the constellation of Auriga. Amid the hypnotic spiral arms is a “twist,” visible in the photo as a bright yellow region in the center, that is thought to be a sign of a planet being born, said Emmanuel Di Folco, a researcher at the Astrophysics Laboratory of Bordeaux in France, who participated in the study.
When a planet forms, the clumps of material create wavelike perturbations in the gas- and dust-filled disc around a star, “somewhat like the wake of a boat on a lake,” Di Folco said.
The bright region at the center of the new image is thought to be evidence of such a disturbance, which had been predicted in models of planetary birth.
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“The twist is expected from some theoretical models of planet formation,” said Anne Dutrey, an astronomer at the Astrophysics Laboratory of Bordeaux and co-author of the study, published Wednesday in the journal Astronomy & Astrophysics. “It corresponds to the connection of two spirals — one winding inwards of the planet’s orbit, the other expanding outwards — which join at the planet location.”
The new observations of the baby planet were made in 2019 and early 2020 by the European Southern Observatory’s Very Large Telescope in the Atacama Desert in northern Chile. The research team, made up of astronomers from France, Taiwan, the U.S. and Belgium, said the images are the deepest observations of the AB Aurigae system made to date.
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