Category: SCIENCE

Dark matter doesn’t absorb or emit light, but it gravitates. Instead of something exotic and novel, could it just be dark, normal matter?

Out there in the Universe, our cosmic inventory is divided up into two categories:

• normal stuff, which includes all the known, discovered particles of the Standard Model and everything they compose,
• and dark stuff, which appears to come in the forms of dark matter, which clumps and gravitates, and dark energy, which dominates the expansion of the Universe.

While normal matter makes up all the things we’ve ever directly detected and interacted with, including atoms, gas, dust, plasma, stars, planets, black holes, neutrinos, light, and even gravitational waves, that only sums up, in total, to about 5% of the total energy of the Universe. The overwhelming majority of the cosmic energy budget comes to us in the form of dark stuff, with dark energy (68%) dominating dark matter (27%) for the past few billion years.

Even though dark energy and dark matter dominate most of the Universe, we’ve only ever detected them indirectly, leading many to doubt, or at least question, their existence. That’s what Richard Whitrock is…

At extremely close distances to their stars, even rocky planets can be completely disintegrated. We’ve just caught our first one in action.

For planets, just like in real estate, the most important property they can possess is “location.” If you want to form a rocky planet, that’s no problem if you’re in the inner part of your stellar system: interior to the analogue of the asteroid belt in our own Solar System. Further out, beyond those frost lines, ices and other volatiles can dominate, giving rise to solid-surfaced worlds that are more akin to giant iceballs than to planets like Mercury, Venus, Earth, or Mars. However, if you venture too close to your parent star, it won’t just be ices and volatiles that get vaporized, but even the layers of the planet itself: atmosphere, crust, mantle, and even the core in the most extreme scenarios.

While “hot Jupiter” exoplanets were among the first planets beyond our Solar System ever discovered, only a few have been caught close enough to their parent stars that their atmospheres are in the process of evaporating. Even more rarely, planets have been caught being completely swallowed by their parent stars. But rocky planets, too, can have their contents evaporated away if they’re heated sufficiently: to conditions where even the heavy elements composing their solid surfaces and…

Here in our own Solar System, we have at least three notable large, terrestrial-sized bodies with impressive lunar systems of their own: the Earth-Moon system, the Mars-Phobos-Deimos system, and the Plutonian planetary system. Pluto, interestingly, is orbited by Charon, which is very large and massive compared to Pluto, an unusual and possibly unique, or most extreme, configuration of all known such bodies. But how did it get to be that way? That’s the…

The primary causes of global climate change are all due to human activity. Adding aerosols to our atmosphere only exacerbates the problem.

All across the world, temperatures and weather conditions vary tremendously, as they always have. But if we look to global conditions, by averaging our data about the entire world together, we find that there have been some rapid, even alarming changes happening on a global scale. The biggest changes, overall? They’re threefold.

1. There have been significant changes to the contents of Earth’s atmosphere, largely due to industrial human activity, and those changes have also affected the land, oceans, and clouds as well.
2. There has been a significant rise in the average temperature of Earth: locally in nearly all places, as well as globally, with some places experiencing greater warming than others.
3. And, coincident with those changes, there has been a tremendous decrease in the percentage of Earth’s surface that is wild, versus the percentage that has been used for human (residential, agricultural, industrial, commercial, etc.) purposes.

Although many had hoped that a long-term fix involving the development and global…

Historically, astronomers have often named things creatively, bizarrely, and often inaccurately. But which terms are the most egregious?

Out there in the Universe, there are all sorts of fascinating objects, phenomena, and events that have been either predicted, theorized, or directly observed. Some of them are named rather intuitively, as we have no problem with names like star-forming region or stellar remnant. Others are named a little more poetically, like kugelblitz, which refers to a (theoretical) black hole formed from radiation alone, or syzygy, which is the alignment of three (or more) astronomical bodies. Still others are words that were derived from acronyms, with objects like quasars derived from the acronym QSRS: quasi-stellar radio sources. While astronomers are kind of notorious for concocting unnecessary acronyms (astronomer Glen Petitpas has created a Dumb Or Overly Forced Astronomical Acronym Site, or DOOFAAS database), we can go further, and look to astronomy names that are complete misnomers: named in such a way that the literal meaning of the words used to describe the object or phenomenon inaccurately represent what it actually is.

That’s the inquiry of Patreon supporter Tim Graham, who was reading this recent article on the T…

If we wish to tackle the very real problems society faces, we require expert-level knowledge. Valuing it starts earlier than we realize.

All across the country, you can see how the seeds of it develop from a very young age. When children raise their hands in class because they know the answer, their classmates hurl the familiar insults of “nerd,” “geek,” “dork,” or “know-it-all” at them. The highest-achieving students — the gifted kids, the ones who get straight As, or the ones placed into advanced classes — are often ostracized, bullied, beaten up, or worse. It’s a version of the social effect known as tall poppy syndrome: where if someone dares to stand out, intellectually in this case, the response of the masses is to attempt to cut them down.

The social lessons we learn early on are very simple: if you want to be part of the cool crowd, you can’t appear too exceptional. You can’t be:

• too knowledgeable,
• too academically successful,
• too advanced compared to your peers,
• or too smart.

Someone who knows more, is more successful, or who seems to be smarter than you is often seen as a threat, and so in order to…

There are only four super star clusters in all the Local Group: rarities today. Here’s what the youngest, the just-discovered N79, shows us.

All throughout cosmic history, star-formation has illuminated the darkness of deep space.

For more than 13 billion years, our Universe has been fully reionized: transparent to starlight.

Although star-formation has slowed to a trickle today, it was 30–50 times more vigorous long ago.

Instead of today’s modern small star-forming regions, giant ones were the norm 6+ billion years ago.

Here in our Universe, both normal and dark matter can be measured astrophysically. But only normal matter can collapse. Why is that?

Here in our Universe, it may be the normal matter that we can directly detect, measure, manipulate, experiment with, and observe, but it’s the dark matter that represents most of the mass in the Universe. Whereas all the “stuff” that the planets, stars, gas, plasma, and dust are composed of represents about 4.9% of the total energy in the Universe, the mysterious dark matter — whose nature is unknown but for which the observational astrophysical evidence is overwhelming — makes up a whopping 27% of the cosmic energy budget. Only dark energy, making up 68% of the Universe, is more important from an energy density perspective.

And yet, dark matter is only ever found in diffuse halos, never in collapsed clumps like normal matter. Why is that? That’s the subject of this week’s question, coming all the way from Barry Lewis in New Zealand, who wants to know:

“How does dark matter, while being gravitational, not collapse? I can’t think of any discussion I’ve come across that addresses this apparent need for it to experience some sort of mutual repulsive force.”

From LIGO, there weren’t enough neutron star-neutron star mergers to account for our heavy elements. With a JWST surprise, maybe they can.

Where do the heaviest elements in the Universe come from? If you were like most astrophysicists during the 20th century, you might’ve said from supernova explosions: stellar cataclysms that occur either within the cores of massive stars or from stellar corpses (white dwarfs) that undergo destructive, energy-releasing events that trigger a rapid succession of nuclear fusion reactions. Unfortunately, a comprehensive study of these classes of events — including both type II (core-collapse) and type Ia (exploding white dwarf) supernovae — showed that, although they do produce large sets of fusion reactions, they really only produce elements up to about zirconium (element #40) on the periodic table.

Beyond that, or for more than half of the known elements that exist, a different set of processes are required. While the slow neutron capture process (s-process) can occur within evolved, Sun-like stars, accounting for large fractions of certain elements, such as niobium, tin, barium, and lead, the majority of heavy elements require another process to explain their observed abundances.

Matter is made up largely of atoms, where atomic nuclei can contain up to 100 protons or more. But how were the heaviest elements made?

Across the Universe, in all directions, there’s practically nowhere we can look that isn’t filled with some sort of matter: stars, galaxies, dust, gas clouds, and plasma chief among them, with small bodies scattered throughout each individual stellar system. When we examine this matter in detail, we find that it isn’t just made of the most common elements — hydrogen, helium, oxygen, carbon, and more — but that the full suite of elements found in the periodic table are found in various amounts all across the Universe. Here in our Solar System, we’ve been able to identify the abundance of these elements most precisely, but we also find them elsewhere: in and around newborn stars, in the interstellar medium, in supernova and kilonova remnants, in planetary nebulae, and much, much more.

But how, where, and when are these elements made? And, in particular, while the lighter elements are relatively easy to make, there are only two sources of production for the heaviest of all; why is that? That’s what Vince Tseng wants to know, asking:

“My question is on how the heaviest elements are…