10 Deep Lessons From Our First Image Of A Black Hole’s Event Horizon
“6. Black holes are dynamic entities, and the radiation emitted from them changes over time. With a reconstructed mass of 6.5 billion solar masses, it takes roughly a day for light to travel across the black hole’s event horizon. This roughly sets the timescale over which we expect to see features change and fluctuate in the radiation observed by the Event Horizon Telescope.
Even with observations that span only a few days, we’ve confirmed that the structure of the emitted radiation changes over time, as predicted. The 2017 data contains four nights of observations. Even glancing at these four images, you can visually see how the first two dates have similar features, and the latter two dates have similar features, but there are definitive changes that are visible — and variable — between the early and late image sets. In other words, the features of the radiation from around M87’s black hole really are changing over time.”
I’ve heard some grumbling over the past day that people are unimpressed with the Event Horizon Telescope collaboration’s big reveal. Maybe the image doesn’t look pretty enough for some people; maybe it doesn’t have the sharpness or level of detail that people are used to from observatories like Hubble.
Well, may I please introduce you to science? If you knew what we’ve actually learned by taking this image, you might change your tune. Read this, and see if you’re not impressed now!
What should I do/say to impress someone who is an astrophysics professor?
Do not mention quantum physics, only the large scale exists. All physicist like it when someone compliments our minds cause we’re very egocentric and desperate. Do not mention Interstellar
How Can We Still See The Disappearing Universe?
“In fact, we can even think about what you’d see if you were to look at a galaxy whose light hasn’t arrived at our eyes yet. The most distant object we can see, 13.8 billion years after the Big Bang, is presently 46 billion light-years away from us. But any object that’s presently within 61 billion light-years of us will someday have that light eventually reach us.
That light was already emitted, and is already on its way to us. In fact, that light is already most of the way there; it’s closer than the 15 billion light-year limit of what we could possibly reach if we left for it at the speed of light. Even though the Universe is expanding, and even though the expansion is accelerating, that journeying light will someday arrive at our eyes, giving us, in the far future, the ability to see even more galaxies than we can today.”
Dark energy seems to present a paradox. On the one hand, galaxies are receding from us as the Universe expands, meaning we can never reach them once they’re beyond a certain point, and that the light being emitted by them can also no longer reach us. But even though these galaxies are a part of our dark energy-dominated Universe, we’ll always be able to see them in the future once they become visible to us.
If the Universe is disappearing, how can we still see the galaxies in it? Come get the answer to one of cosmology’s biggest (misconception-related) puzzles today!
Ask Ethan: Why Haven’t We Found Gravitational Waves In Our Own Galaxy?
“Why are all the known gravitational wave sources (coalescing binaries) in the distant universe? Why none has been detected in our neighborhood? […] My guess (which is most probably wrong) is that the detectors need to be precisely aligned for any detection. Hence all the detection until now are serendipitous.”
On September 14, 2015, our view of the Universe changed forever with the first direct detection of gravitational waves. Since then, we’ve detected a variety of black hole and neutron star binaries in the final, end-stages of coalescence, culminating in a spectacular merger. But they’re all hundreds of millions or even billions of light-years away!
Simultaneously, we know that we have neutron stars and black holes in binary systems here in our own galaxy. But of all the gravitational waves that LIGO and Virgo have detected, none of these objects are among them. This remains true, even though we can identify many of them from their electromagnetic signatures.
Why haven’t we found gravitational waves in our own galaxy? Give us a better observatory and we will! Here’s the full scientific story on that.
One Of These Four Missions Will Be Selected As NASA’s Next Flagship For Astrophysics
“Choosing which of these missions to build and fly will, in many ways, inform our plans for the next 30 years (or more) of astronomy. NASA is the pre-eminent space agency in the world. This is where science, research, development, discovery, and innovation all come together. The spinoff technologies alone justify the investment, but that’s not why we do it. We are here to discover the Universe. We are here to learn all that we can about the cosmos and our place within it. We are here to find out what the Universe looks like and how it came to be the way it is today.
People will always argue over budgets — the penny-pinchers are always happy to propose something that’s faster, cheaper, and worse — but the reality is this: the budget for NASA Astrophysics as a whole is just $1.35 billion per year: less than 0.1% of the federal discretionary budget and less than 0.03% of the total federal budget. And still, for that tiny amount, NASA has steadily built a flagship program that’s the envy of the free world.”
Every 10 years, NASA performs a decadal survey, where it outlines its highest mission priorities for the next 10 years. The 2020 decadal is happening imminently, and once the recommendations are submitted to the National Resource Council at the National Academies of Science, the four flagship finalists will be ranked. This will determine NASA astrophysics’ direction for the 2030s.
James Webb is the flagship for the 2010s; WFIRST is it for the 2020s. What will we choose for the 2030s? It will be one of these four finalists! Dream big, everyone.
Could The Milky Way Be More Massive Than Andromeda?
“The Milky Way is home to the Sun, our Solar System, and hundreds of billions of stars beyond that. Yet unlike all the other galaxies out there — in our Local Group and in the Universe beyond — we have no good way to view our own galaxy from our position within it. As a result, the full extent of our galaxy, including its total size, mass, matter content, and number of stars, remains mysterious to modern astronomers.
We’ve long looked at the galaxies surrounding our local neighborhood in space and compared ourselves to them. Although there may be more than 60 galaxies present within the Local Group, two of them dominate in every way imaginable: ourselves and Andromeda. We are the two largest, most massive galaxies around, with more stars than all the others combined. But which one is bigger? Long thought to be Andromeda, we’re now finding out the Milky Way might have a chance at being number one.”
It’s 2019, and we still don’t know how massive the Milky Way is, or even whether we’re the most massive galaxy in the Local Group or not. It’s a lot like measuring your eye color: looking out at everyone else, it’s easy to see what color their eyes are. But if you didn’t have a reflection, photograph, or the observations of others, how would you know your own eye color? Well, being trapped within the Milky Way makes measurements notoriously difficult, and we’re only now figuring out how to overcome that obstacle.
It’s not only possible, but even likely that the Milky Way, despite having fewer stars occupying less volume than Andromeda’s, is the most massive galaxy in the Local Group. Come get the full story.
How Much Of The Dark Matter Could Neutrinos Be?
“If we restrict ourselves to the Standard Model alone, we simply cannot account for the dark matter that must be present in our Universe. None of the particles we know of have the right behavior to explain all of the observations. We can imagine a Universe where neutrinos have relatively large amounts of mass, and that would result in a Universe with significant quantities of dark matter. The only problem is that dark matter would be hot, and lead to an observably different Universe than the one we see today.
Still, the neutrinos we know of do behave like dark matter, although it only makes up about 1% of the total dark matter out there. That’s not totally insignificant; it equals the mass of all the stars in our Universe! And most excitingly, if there truly is a sterile neutrino species out there, a series of upcoming experiments ought to reveal it over the next few years. Dark matter might be one of the greatest mysteries out there, but thanks to neutrinos, we have a chance at understanding it at least a little bit.”
Dark matter is a form of matter that gravitates, but neither absorbs nor emits light, and has been frustratingly difficult to pin down and directly detect. There’s a known particle that has exactly those same properties: the neutrino! You might wonder, then, if perhaps neutrinos had the right value of mass and number, if they could make up the dark matter? And if not all of it, could they at least make up part of it? This is a question that astronomers and physicists have pondered for decades, and we might be closer than ever to the actual answer.
How much of the dark matter can neutrinos actually be? Find out today!
What Was It Like When Planet Earth Took Shape?
“There was almost certainly a high-energy collision with a foreign, out-of-orbit object that struck our young Earth in the early stages of the Solar System, and that collision was required to give rise to our Moon. But it was very likely much smaller than Mars-sized, and it was almost certainly a sturdy strike, rather than a glancing collision. Instead of a cloud of rock fragments, the structure that formed was a new type of extended, vaporized disk known as a synestia. And over time, it settled down to form our Earth and Moon as we know them today.
At the end of the early stages of our Solar System, it was as promising as it could be for life. With a central star, three atmosphere-rich rocky worlds, the raw ingredients for life, and with gas giants only existing much further beyond, all the pieces were in place. We know we got lucky for humans to arise. But with this new understanding, we also think the possibility for life like us has happened millions of times before all throughout the Milky Way.”
One of the deepest existential questions we can ask about the Universe is how, after more than 9 billion years, all the phenomena in our cosmic history led to the creation of planet Earth. Going from an environment where stars were actively forming to one where the Sun, Earth, and all the other planets were in place is a daunting task for people who create scientific simulations of our early environment, and involves gravitational interactions, planetary migrations and ejections, and even enormously energetic collisions between planets and proto-planets.
Yet somehow, it all came together, and gave rise to us. From what we’re learning, we might not even be all that rare. Come check out the current story.