Comments of the Week #164: From black holes to moons with moons of their own [Starts With A Bang]

“There are two types of people who will tell you that you cannot make a difference in this world: those who are afraid to try and those who are afraid you will succeed.” -Ray Goforth

We’ve really investigated some amazing scientific stories this week here at Starts With A Bang! There’s always so much to consider, think about and enjoy, and I’m already looking ahead to what’s on the plate for this week: a new podcast to put together, progress on designing and constructing our timeline-of-the-Universe poster, and putting the final touches on my upcoming book, Treknology! In fact, I had an incredible chance to talk about it with Richard Jacobs on the Future Tech Podcast, which — if you have 36 minutes — you should take a listen to, as there’s so much we explore!

We’ve had a pretty incredible week of stories, of course, and if you missed anything (or want a second look), here’s the recap:

• How many black holes are there in the Universe? (for Ask Ethan),
• The scientific story of how each element was made (for Mostly Mute Monday),
• How much CO2 does a single volcano emit?,
• We’re way below average! Astronomers say Milky Way resides in a great cosmic void,
• New LIGO signal raises a huge question: do merging black holes emit light?, and
• Can moons have their own moons?

So it’s been a typical week: I’ve written six new articles, and you’ve responded with nearly 100 comments for me! What else does that inspire? Let’s find out in our comments of the week!

Image credit: Keck / UCLA galactic center group / A. Ghez et al., via http://astro.uchicago.edu/cosmus/projects/UCLA_GCG/.

From Paul Dekous on the orbits of stars around our galaxy’s central black hole: “…why aren’t those orbits more coplaner like the planets in our solar system, should’t those stars align much more if there was indeed a massive object tying everything together?”

This is a very interesting question, but let me ask you a question to get you thinking in the right direction: why are the planets in our Solar System all in a plane, but the Oort cloud objects have a diffuse, spherical distribution? Or why is our galaxy mostly a disk, except with a bulge in the center?

It’s because the “disk” part comes about when you form a structure: something that gets pancaked or funneled into a particular shape based on what’s energetically favorable. But over time and through chaotic interactions, or because you were never subjected to the forces that made a disk in the first place, you obtain random properties that allow you to be distributed more like a “swarm.” The interactions that give rise to stellar orbits around the galactic center are much more a part of the latter category, and that’s why they — like elliptical galaxies, our bulge, or the objects in the Oort cloud — have somewhat random distributions in terms of their orbital axes.

The simulated decay of a black hole not only results in the emission of radiation, but the decay of the central orbiting mass that keeps most objects stable. Image credit: the EU’s Communicate Science.

From Denier on a view of quantum gravity and where he’s in error: “If Classical Physics held true all the way down you’d be right on the money but Quantum Gravity is the probabilistic movement of particles and has nothing to do with the warpage of space-time. With Quantum Gravity there is a direct outward path through space from the center to the horizon.”

I think this is where the error arises, but you must recognize that I’m extrapolating from quantum field theory for the other forces because we don’t have a quantum theory of gravity. The way quantum electrodynamics works, for example, is that you consider all possible paths a particle could take, integrate over them weighted by their probabilities (no matter how infinitesimally small), and you arrive at the total probability and amplitude of a particle’s distribution. But what you’re describing as a “direct outward path” should be a path with exactly zero probability, meaning it won’t contribute anything at all.

There is a physical limit in space and time of “wavefunction spreading” which is defined by quantum operators, which don’t simply allow you to get “any result at all” like you might intuit. Even virtual particles can’t do anything at all, like you will them to. They are still bound by the laws of physics, even if their existence is calculational/mathematical in nature.

From Elle H.C. on a new idea of particles: “A wave is like a Spring, a compressed spring is harder, but it is still the same spring, moving along or against the grain. So what you’re measuring could be different compression states of the same spring, and not different particles.”

This is actually a super old idea, and the idea that higher massed-versions are simply “excited states” or resonances of lower-mass ones have been ruled out through experimental particle physics. It isn’t to say it’s a bad idea; it’s not, in principle. But it isn’t how our Universe works, and if you don’t believe it, try explaining how a muon decays (and doesn’t decay) with it; you can’t.

Although we’ve seen black holes directly merging three separate times in the Universe, we know many more exist. Here’s where they must be. Image credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet).

From Omega Centauri on stellar-mass black holes vs. (super)massive black holes: “So the total mass of stellar BHs may be comparable to the total mass of MBHs. This either implies that perhaps half of stellar mass BHs have been absorbed by MBHs, -or that MBHs have another major growth mechanism beyond eating stellar mass BHs?”

I am just assuming that when you say “MBH,” you mean “SMBH,” for supermassive black hole, and not “micro-black holes,” which I will not address here, now, or in the foreseeable future due to the number of times I’ve addressed them and their lack of existence.

So what we expect is that on average, you expect somewhere around 1/1000 stars that form to create black holes, but that this is heavily mass-weighted, so that perhaps a few percent of all the stars that form by mass wind up creating black holes. If we take a look at supermassive black holes, the largest black holes (like the 6 billion solar mass one in M87) come in the galaxies with the largest stellar mass populations (M87 has roughly 10^13 solar masses in stars), while our galaxy (with more like 10^11 solar masses in stars) has only a 4 million solar mass black hole. If we just take those two numbers, we find that there’s roughly a factor of about 100-1000 difference between the total mass of stellar black holes and the mass of a supermassive black hole in galaxies. It isn’t close to half; it’s more like 1:100 to 1:1000.

Don’t rush to implications just yet!

The most current, up-to-date image showing the primary origin of each of the elements that occur naturally in the periodic table. Neutron star mergers and supernovae may allow us to climb even higher than this table shows. Image credit: Jennifer Johnson; ESA/NASA/AASNova.

From Michael Kelsey on making the light elements: “The main figure (annotated periodic table) shows exactly this: Lithium is mainly yellow (“dying low mass starts”), with most of the rest the pink corner (“cosmic ray fission”, or what I would have called spallation), and a thin strip of dark blue (“big bang fusion”) for the primordial Li-7.
For beryllium and boron, both have only single stable isotopes, which makes their production tricky. B-10 is the daughter of Be-10 decay, but Be-10 itself is hard to produce — neutron absorption onto stable Be-9 produces alphas (Be-9(n,2n)Be-8*, Be-8* -> 2a), so you won’t get Be-10 in stars.”

There are a few way to make the rare elements lithium, beryllium and boron, but most important isotopes are unstable, and the elements you do make are easily destroyed. The Universe is full of hydrogen (normally H-1) and helium (normally He-4), where isotopes like deuterium and He-3 are stable, while tritium (H-3) is long-lived. But there are no stable mass-5 or mass-8 nuclei, so you can only make lithium-6 and lithium-7 (or beryllium-7, which decays to lithium-7 on long timescales) out of them. But lithium-6 and lithium-7 are easy to blow apart in stars, so you not only don’t do well to make them there, if you get pre-existing Li-6 or Li-7 and it makes its way into a star, it’s not going to last long.

So you can get a little help in the final stages of red giant stars, which is what “dying low mass stars” that produce planetary nebulae are for lithium, but beryllium and boron can’t do even that. As Michael Kelsey alluded to, you might think, “oh, I know Be-9 is stable and I can start with a bit of that, and then hit it with a neutron, making Be-10 which decays to stable B-10.” It’s a good idea, since you get free neutrons in stars all the time, and Be-9 isn’t super-easily destroyed like lithium is. But there’s a problem when you add a neutron to Be-9; you don’t get the ground state of Be-10, but an excited one: Be-10*, which immediately emits two neutrons in response. The daughter product, Be-8, then only lives for ~10^-16 seconds before decaying into two He-4 nuclei, and that’s the end of boron and beryllium. So far, cosmic rays are the only way we know how to get there.

Understanding the cosmic origin of all the elements heavier than hydrogen can give us a powerful window into the Universe’s past, as well as insight into our own origins. Image credit: Wikimedia Commons user Cepheus.

From eric on the highest elements of all: “It would be great if Walt Loveland (or a collaborator) could update The Elements Beyond Uranium. I was going to recommend it to folks who wanted to learn more about the discovery of the man-made elements…then I realized that it only covers about 15 of them, and there are now 24. So it misses a full third!”

This is one of my favorite things about science: the ongoing process. When I was a kid, the periodic table went up to 106, provisionally, and people argued if there was an “island of stability” somewhere higher up there, while Bismuth, element 83, was the heaviest stable element. Now? We’re up to 118, inclusively, which is a big deal because 119 starts the next row of the periodic table! We’re almost up to the “eighth period,” and element 126 is where that supposed “more stable” isotope would be. If we’re lucky, and if we’re ingenious enough, we’ll be able to test that out. Oh, and bismuth? It decays after ~10^19 years, a billion times longer than the age of the Universe. Wait long enough, and it will all become lead.

From CFT on a little bit of climate misdirection: “Oh Nooooooooooes!! Quck, everyone, stop breathing while there’s still time!
Too bad Ethan didn’t mention the number one greenhouse gas. Water vapor. Damn. Too bad our planet is 71% covered with water and the damn sun keeps evaporating it.”

From the article:

“The pressure allows water to exist in the liquid phase, and the heat-trapping clouds and gases like water vapor, methane, and carbon dioxide give us the warmth necessary to have oceans. Carbon in particular is a tremendous part of our planet; it’s the fourth most abundant element in the Universe, the essential element for organic matter, and – other than the Sun – is the most important factor in determining Earth’s temperature. It’s also the essential element in two of the three major greenhouse gases playing a role in our temperature, with water vapor varying tremendously based on other factors. But most of that carbon is sequestered not in the Earth’s crust, but deep within the mantle.”

But that’s not even the point. The point is that this article was about how much CO2 volcanoes emit and how that compares to the CO2 that humans emit. And that was handled extremely accurately. You clearly don’t like the conclusion, but you’re going to have to get used to it. The world doesn’t care about your counterfactual conclusions; it simply does what physical science demands of it.

Hundreds of active and dormant volcanoes worldwide, like the ones shown here in Kamchatka, continually degas and emit CO2. Image credit: Cosmonaut Fyodor Yurchikhin / Russian Space Agency Press Services.

From SteveP on how he sees the climate wars of today: “The tendency of simians to band together in tribes, teams, and clans with common misperceptions is a fascinating part of the human experience. Among the cultural values of the Fossil Fuel tribe ( the FoFu), for instance, is the belief that anyone without the same stripes as them is a foe, so an outsider trying to help the FoFu understand their existential predicament is a little like a naturalist trying to warn a badger away from a leg hold trap.
Despite their acquisition of language and reasoning skills, the FoFu are a puzzle. They have yet to realize that a near ubiquitous, persistent, steadily accumulating , acidic, non-condensing infrared active waste product that they are actively creating is poised to wreck their comfortable niche in the universe. Whether or not they can be alerted to the problem in time to avert disaster is a question. Is anyone out their fluent in FoFu?”

I think it’s a lot more than that, SteveP. There was a very prescient book called Culture Wars (pick it up!) that was written in 1991, and I think we’re seeing the endgame (or maybe not; maybe just the middlegame) playing out today. It’s a question of identity that I think is at the core of this conflict. How do we define ourselves? Who do we think is “like us” or different from us, who is on “our side” versus who isn’t, who is “fighting the good fight” and who’s a villain in the story of our world today?

When we think in these terms, we lose the ability to look at the pros and cons of an argument. We lose the nuance. We lose any pretense of objectivity that we had. And it’s something we all have to fight against by asking questions and being open to new information. I spent most of yesterday at a Sheriff’s workshop on civilian responses to public threats, ranging from lone gunmen (it’s 98% men who are shooters) to knife-wielding maniacs to bombers and more. You might not think there’d be a bunch of lefties in the workshop, but there we were. Regardless of where you stand on a variety of political issues, this world is all of ours, and it’s up to each of us to contribute to making it better.

The construction of the cosmic distance ladder involves going from our Solar System to the stars to nearby galaxies to distant ones. Each “step” carries along its own uncertainties; it also would be biased towards higher or lower values if we lived in an underdense or overdense region. Image credit: NASA,ESA, A. Feild (STScI), and A. Riess (STScI/JHU).

From Anonymous Coward on the cosmic distance ladder: “Is it possible to measure the Hubble constant using supernovae or a Cepheid variables from galaxies outside the KBC void?”

Supernovae? Yes. Cepheids? Nope. In fact, supernovae are really the only standard candle that serves as a distance indicator that can take us beyond the KBC void. The whole point is that we may be biasing ourselves towards higher values of H by being situated where we are. If this idea is correct, we should be able to determine this with future surveys that get large numbers of distant supernovae like Euclid, WFIRST and the LSST. I am hopeful.

From chris heinz on our likelihood and location: “Our solar system is in a relative void too: the outskirts of a spiral galaxy. between arms. Antropic principle maybe selects for voids to support life because of lower radiation levels?”

We’re not that far towards the outskirts; we’re about halfway between the edge of the arms and the center. We’re on a spur of one of the arms, so not exactly between arms, and that situation is temporary, as stars move in-and-out of the arms. But why would you think we need a void to support life, or that elevated radiation levels would be dangerous to life on a planetary scale? Our Sun’s protective effects and the Earth’s magnetosphere do a wonderful job of protecting us from cosmic rays, and there’s no reason to believe they wouldn’t also be sufficient anywhere else in the galaxy. Don’t assume we need to resort to anthropic arguments when there may not even be a problem or puzzle here.

The simulated large-scale structure of the Universe shows intricate patterns of clustering that never repeat. But from our perspective, we can only see a finite volume of the Universe. What lies beyond this edge? Image credit: V. Springel et al., MPA Garching, and the Millenium Simulation.

From JonW on what makes an average density to the Universe: “Is “average” density defined via random sampling of galaxies (observers) or random sampling of points in the universe?”

Neither. It’s a random sampling of volumes in the Universe, which allows us to determine the overall average as well as the variation from that average on any scale we look at. Small scales have larger magnitude variations; large scales have small magnitude variations.

From Sinisa Lazarek on why light could be delayed: “if both EM waves and grav. waves propagate at the same speed, why a delay of 19 hours?”

19 hours ought to be too much; we don’t think that’s likely. But! Sometimes you make signals that take some time to travel through a medium or through matter. Light from a supernova needs to travel through the outer material of the progenitor star, and so there’s a delay there. Light from other sources may need to travel through other media or matter, and so may have its arrival time delayed in a way that gravitational waves do not. But 19 hours is probably too much.

A blazar coming from the same region of the sky where ultramassive black hole OJ 287 resides. Images credit: Ramon Naves of Observatorio Montcabrer, via http://cometas.sytes.net/blazar/blazar.html (main); Tuorla Observatory / University of Turku, via http://www.astro.utu.fi/news/080419.shtml (inset).

From Denier on visualizing a blaze of fantastic radiation: “What would it look like to the instruments if a black hole jet was pointed at us for a fraction of a second?”

We don’t need to imagine; these objects are known as Blazars and exist in some significant abundance. Most AGNs (which arise from black hole jets) aren’t pointed at us, but a few are!

Of course, a Kuiper belt object would need to have a moon with its own moon to be considered a moon having a moon. The distances at play would likely need to be very great; at some point, the gravitational binding energy becomes very small and the region you have for success is extremely narrow. Image credit: Robert Hurt (IPAC).

From Anonymous Coward on whether moons could have moons: “To have a stable moon with a moon system requires finding a stable solution to the three-body problem, which is the classical example of a chaotic dynamical system.”

Well, let’s not go that far. When we say “stable,” we don’t mean 100% stable on all timescales permanently forever and ever, which we never have. In 10^150 years, the Earth would spiral into the Sun due to gravitational radiation, even if Earth and Sun were the only two masses in the Universe. But we consider our Moon orbiting Earth orbiting the Sun to be stable, because it’s stable on the timescales of the Solar System. If a moon of a moon only lasts a few million or even a few hundred million years, it isn’t a good deal for the Solar System.

Mars’ Phobos might be interesting, but there was probably a larger, third, inner moon that was created when Phobos an Deimos were, but it’s already fallen back onto Mars. Phobos is likely next, but Deimos might be stable, now, after all.

Jupiter with its four largest moons. Image credit: Mike Hankey, via http://www.mikesastrophotos.com/planets/amateur-astronomer-strikes-again/.

And finally, from Tom P. on what a moon of a moon would need to survive: “In summary, it sounds like you are saying there’s no reason a moon couldn’t have a moon but it probably couldn’t hold on to it for very long. Is it possible to make an order of magnitude estimate of how long the more likely satellites could keep a moon?”

If you’re talking about something a few thousand or tens-of-thousands of kilometers away, a moon could theoretically last billions of years around Callisto, the outermost Galilean moon of Jupiter. If you can steer clear of having your orbit perturbed too severely by Ganymede, you ought to be good to go for a very long time, but that may be the limiting factor. We also don’t know the extent of Callisto’s atmosphere, as it’s never gotten a good mission to go by it. Billions of years are plausible for Triton as well, but our own Moon, honestly, may be a better candidate than Triton for gravitational regions of stability.

It’s not as much a question of “could,” though, as it is a question of “what do we actually have.” If I gave optimal orbital parameters for a hypothetical moon around one of these existing moons, I could make it work. But did nature make that? That’s the question we still don’t know the answer to.

Thanks for a great week, everyone, and see you back here for more next time!