Category: astrophysics

Physicists Used Einstein’s Relativity To…

Physicists Used Einstein’s Relativity To Successfully Predict A Supernova Explosion

“When the lens and a background source align in a particular fashion, quadruple images will result. With slightly different light-travel paths, the brightness and arrival time of each image is unique. In November 2014, a quadruply-lensed supernova was observed, showcasing exactly this type of alignment. Although a single galaxy caused the quadruple image, that galaxy was part of a huge galaxy cluster, exhibiting its own strong lensing effects. Elsewhere in the cluster, two additional images of the same galaxy also appear.”

We normally think of light traveling in a straight line, but that’s only true if your space is flat. In the real Universe, mass and matter not only exist, but clump together into massive structures like galaxies, quasars, and galaxy clusters. When a background source of light passes through these foreground masses, the light can get bent and distorted into multiple images that are magnified and arrive at slightly different times. If an event occurs in one such image, we can predict, based on General Relativity, cluster dynamics, and dark matter, when that event will appear in the other images.

In November 2014, we discovered a multiply-lensed supernova, and predicted where and when it would appear in the other images. Einstein and dark matter both win again!

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If infinite parallel universes exist…

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Not my proudest fap

What Was It Like When Galaxies Formed The Grea…

What Was It Like When Galaxies Formed The Greatest Number Of Stars?

“The star-formation rate declined slowly and steadily for a few billion years, corresponding to an epoch where the Universe was still matter-dominated, just consisting of more processed and aged material. There were fewer mergers by number, but this was partially compensated for by the fact that larger structures were merging, leading to larger regions where stars formed.

But right around 6-to-8 billion years of age, the effects of dark energy began to make their presence known on the star formation rate, causing it to plummet precipitously. If we want to see the largest bursts of star formation, we have no choice but to look far away. The ultra-distant Universe is where star formation was at its maximum, not locally.”

In a myriad of locations, throughout our galaxy and almost all the galaxies in the known Universe, new stars form wherever a cloud of gas is triggered into collapsing. From the Orion Nebula to dozens of others in our own galaxy, new stars form thousands-at-a-time in regions all throughout our local neighborhood. But as spectacular as these sights are, they’re much, much rarer than they were a long time ago. In fact, we formed stars at a rate that was 30 times faster than today back when the Universe was young. For the last 11 billion years, we’ve been forming fewer and fewer stars everywhere we look.

The Universe is changing even today, and fewer and fewer stars are being newly created as time goes on. There are many reasons why; come learn them today!

Who Really Discovered The Expanding Universe? …

Who Really Discovered The Expanding Universe?

“Recently, what was known for generations as “Hubble’s Law” has now been renamed the Hubble-Lemaître law. But the point shouldn’t be to give credit to individuals who’ve been dead for generations, but rather for everyone to understand how we know the rules that govern the Universe, and what they are. I, for one, would be just as happy to drop all the names from all the physical laws out there, and simply to refer to them as what they are: the redshift-distance relation. It wasn’t the work of just one or two people that led to this breakthrough in discovering the expanding Universe, but of all the scientists I named here and many others as well. At the end of the day, it’s our fundamental knowledge of how the Universe works that matters, and that’s the ultimate legacy of scientific research. Everything else is just a testament to the all-too-human foible of vainly grasping at glory.”

In science, we have a tendency to name theories, laws, equations, or discoveries after the individual who made the greatest contribution towards its development. For generations, we credited Edwin Hubble for discovering the expanding Universe, as his contributions in the 1920s were absolutely tremendous. However, history has not only revealed that Georges

Lemaître

discovered the very law we had named after Hubble two years prior, but that many other people made essential contributions to that realization. The expanding Universe didn’t come about solely because of Hubble’s discoveries, and perhaps we can do better than crediting just a single person.

Here are a slew of advances that led to and supported the expanding Universe, showing that history and science relies on contributions far richer than that of a lone, genius scientist.

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Ask Ethan: When Do Black Holes Become Unstable…

Ask Ethan: When Do Black Holes Become Unstable?

“Is there a critical size for black hole stability? [A] 1012 kg [black hole] is already stable for a couple of billion years. However, a [black hole] in the range of 105 kg, could explode in a second, thus, definitely not stable… I guess there is a critical mass for a [black hole] where the flow of gained matter will equal to the Hawking evaporation?”

Wherever you have a black hole in the Universe, you have two competing processes. On the one hand, anything that crosses the event horizon, whether it’s normal matter, dark matter, or even pure energy, can never escape. If you fall in, you just add to the overall mass of the black hole, and grow it in size, too. But on the other hand, all black holes radiate away energy in the form of Hawking radiation, and that subtracts mass over time, shrinking your black hole. For all realistic-mass black holes, the rate-of-growth far outstrips the rate of mass loss, meaning they’ll grow for a very long time before they start to shrink.

But eventually, they will shrink. And although we think they don’t exist, a low-enough mass black hole would start shrinking today. Find out when black holes become unstable today!

This Is How We Will Discover The Most Distant …

This Is How We Will Discover The Most Distant Galaxy Ever

“Sometime in the distant past, likely when the Universe was less than 2% its current age, the very first galaxy of all formed when massive star clusters merged together, resulting in an unprecedented burst of star formation. The high-energy light from these stars struggles to escape, but the longer-wavelength light can penetrate farther through neutral atoms. The expansion of the Universe redshifts all the light, stretching it far beyond anything Hubble could potentially observe, but next-generation infrared telescopes should be able to catch it. And if we observe the right part of the sky, with the right instruments, for a sufficiently long time to reveal the right details about these objects, we’ll push back the cosmic frontier of the first galaxies even farther.

Somewhere, the most distant, first galaxy of all is out there, waiting to be discovered. As the 2020s approach, we can feel confident that we’ll not only shatter the current cosmic record-holder, but we know exactly how we’ll do it.”

13.8 billion years ago, our Universe as-we-know-it began with the hot Big Bang. There were no stars or galaxies back then; there weren’t even bound structures of any type. Everything was too energetic, and would immediately be destroyed by the unfathomably high temperatures and energies that every particle possessed. Yet, with time, the Universe expanded and cooled. Protons, nuclei, and neutral atoms formed; overdense regions gravitationally pulled-in mass and matter; stars were born, lived, died, and new stars were born in their aftermath. At some point, the first large star clusters merged together, passing a critical threshold and forming the first galaxy in the Universe.

That’s what we want to find. We’ve gone back to when the Universe was just 3% its present age, but that’s not enough. We must go father. We must find the first one. Here’s how we’ll do it.

‘Aliens’ Is Not A Scientific Expla…

‘Aliens’ Is Not A Scientific Explanation For Interstellar Asteroid ʻOumuamua

“We often say that extraordinary claims require extraordinary evidence, and in all of these cases the evidence is very, very ordinary indeed. It’s worth keeping our mind open to the possibility that there’s more out there in the Universe than we presently realize, but not to embrace those possibilities as likely in any way whatsoever. When you leap to explanations that are fantastic, it’s all too easy to forget about the most likely explanations, which often involve nothing more than the natural phenomena already present and well-understood in the Universe we know.

In the case of interstellar interloper ʻOumuamua, we should be looking at the natural explanations first and foremost, not speculating about something for which the only evidence is our own wishful thinking. After all, what can be asserted without evidence can — and should — be dismissed without evidence.”

When you find a new phenomenon in the Universe, one that you’ve never seen before, the opportunity to discover something new about your reality is unparalleled. Oftentimes, you’ll try to use what you know to infer what behavior you expect, but it’s usually just a first-order, naive approximation. Until you collect enough data, find enough objects that fall into the new category, and study them with the required precision and detail, you’ll merely be speculating about what’s going on.

Last year, our Solar System got a visit from an interstellar interloper, marking the first time that’s ever happened. It’s been an interesting ride, full of interesting science and fascinating findings. Which is why it’s maddening that the one time it makes news is when a couple of scientists from Harvard take off their scientist hat and run headlong into sci-fi speculations.

For what I’m sure won’t be the last time, invoking aliens as an explanation for what you don’t understand isn’t science. Don’t fall for it. Get the facts instead!

Ask Ethan: How Do Black Holes Actually Evapora…

Ask Ethan: How Do Black Holes Actually Evaporate?

“[J]ust what is Hawking radiation? The science press articles keep referring to the electron-positron virtual pair production at the event horizon, which makes a lay person think that the Hawking radiation consists of electrons and positrons moving away from the black hole.”

Halloween may be over now, so you are free to return to your regularly scheduled existential crises instead of being scared by ghouls and goblins. To help you with that, let’s think about the fact that everything in the Universe, given enough time, will eventually die and decay away. The longest-lived entities, as far as we know, are the supermassive black holes at the centers of galaxies. While stars will burn out after billions or trillions of years, and white dwarfs will cool down after quadrillions, and galaxies will gravitationally dissociate after perhaps 10^24 years, black holes will stick around for far longer: up to 10^100 years. But even they don’t live forever. Hawking radiation ensures that they will decay away, eventually, too.

But if you learned about Hawking radiation from Hawking’s explanation itself, you were lied to. Come find out how black holes actually evaporate today!