When I look up at the night sky, I’m torn. On the one hand, we know so much more about the heavens than our ancestors who slept beneath the same blanket of stars. But on the other hand, we still know almost nothing.
These are just a few of the biggest mysteries of the cosmos.
Let us know: what do you wonder about?
We all know that our galaxy is in constant motion. After all, the universe is expanding, and the Milky Way is part of the universe.
But scientists have been puzzled by the unusual direction were moving in.
It turns out that our galaxy is hurtling towards a point 220 million lightyears away, known simply as The Great Attractor.
Nobody is certain what it is, and some have suggested that the dense star fields Milky Way itself may be blocking our view of the object (or objects).
But whatever The Great Attractor really is, it must be extremely massive, because our galaxy is hastening toward it at a staggering 1.4 million mph.
In 2013, NASAs Cassini space probe saw something strange happening along the outer edge of Saturns ring system. It looked like a bunch of debris was in the process of clumping together, forming a possible new moon.
This oject was given the provisional name Peggy.
Nothing like it had ever been seen before. Bizarrely, Peggy didnt grow any larger and may have broken apart completely. Nobodys really sure.
Tabbys Star is, in many respects, quite similar to our own sun. At a distance of 1,280 lightyears, its about 1.4 times the mass of our parent star, and shares a familiar yellowish hue.
But thats where the similarities end.
Tabbys Star appears to have a very strange companion orbiting around it. Whatever this object is, it doesnt seem to be a planet. That has raised more than a few questions, and one particularly intriguing possible answer.
The object was discovered because it blocks about 20% of the light emanating from Tabbys Star as it orbits.
For reference, Jupiter, the largest planet in our solar system, would block about 1% of the suns light to an outside observer.
This effectively rules out the possibility that the mystery object is a planet, since any known object large and massive enough to block 20 times as much light as Jupiter would also have a dense enough core to become a star in its own right.
So what are we dealing with here?
One theory is that the object may be a Dyson swarm, a hypothetical energy collector that harnesses the power of a star to feed an advanced civilization.
However, radio observation of Tabbys Star has yielded no evidence that its being used as an alien power plant. Maybe these aliens are smart enough to keep their mouths shut, but it’s more likely that they simply aren’t there.
If youre hoping to find life-bearing planets in our galaxy, dont let Tabbys Star get you down. Theres a far better candidate much closer to our own solar system.
Trappist-1 is a tiny star, barely larger than Jupiter, and only 8% as massive as the sun. Even though its one of our closest neighbors – at 39.5 lightyears – its still far too dim to be seen with the naked eye.
But size isnt everything.
Trappist-1 hosts by far the most interesting family of planets weve seen in the cosmos thus far. In 2015, scientists began finding earth-like planets in close orbit around this mini-star.
In total, 7 rocky planets have been found, all of them between 20% and 170% the mass of the Earth.
At least three of them appear to orbit within the habitable zone of the star – the distance at which surface temperatures are suitable for liquid water.
Are any of these planets capable of sustaining life? We just dont know. Yet.
Of course, if youre looking for life in the universe, you may not even need to leave the solar system.
There are three very interesting bodies in our solar system that scientists think could potentially harbor life. Not only are these worlds not in the so-called habitable zone, theyre not even planets.
Europa, a moon of Jupiter, and Enceladus and Titan, moons of Saturn, have attracted the attention of space explorers interested in finding life in our own backyard.
Amazingly, scientists believe Europa likely has an ocean of liquid water beneath its icy crust. In fact, it may have substantially more water than the Earth.
How is it possible to have so much liquid water so far from the sun? Underwater volcanoes. The tidal effects Jupiter exerts on Europa could create enough energy to fuel volcanism beneath the surface, warming a liquid ocean, and possibly sustaining life.
That idea isn’t so crazy when you consider that there are entire ecosystems in our oceans that draw all their energy from deep-sea volcanic vents. They don’t need the sun at all.
Enceladus is even more inviting than Europa. It is actually giving off a plume of salty water as it orbits Saturn, much like the tail of a comet in the inner solar system. Enceladus is much smaller than Europa, but it may still possess a liquid ocean as large as Lake Superior.
Titan, also a moon of Saturn, warrants a mention as well. Although its average surface temperature hovers around -270 F, it is the only body in the solar system apart from Earth that has liquid on its surface.
Unlike Earth, however, that liquid is methane and ethane. So… no smoking on Titan, I guess.
I dont mean to be alarmist, but humans really understand almost nothing about the universe – and I mean that in an extremely literal sense.
It turns out that all the matter of which we have any feeble comprehension – the stuff that makes up stars, planets, the dust-lanes of the galaxies – it all amounts to less than 5% of the total mass-energy content of the universe.
That means that virtually the entire cosmos is invisible to us, detectable only though the gravitational effects it has on the things we can see. As far as we can tell, we’re like the sprinkles on a giant ice cream cone made of god-knows-what.
What is that invisible 95% of creation? Well, we have some thoughts on that.
In 1933, the Swiss-American astrophysicist Fritz Zwicky was studying galaxy clusters. Galaxies tend to clump together in filaments which stretch out in all directions like the threads of a spider web, bound together by their mutual gravity.
Only one problem. As Zwicky observed, at the speeds the galaxies are moving, there is no way they should be able to stick together; based on the mass of the observable matter in these clusters, they should have flown apart long ago. But they haven’t.
Zwicky concluded that there must be enormous quantities of what he called dark matter – so called because its undetectable and doesnt interact with anything else in the universe – holding the galaxy clusters together. He further concluded that there must be far more dark than regular matter. It was the only way he could explain the motions of the galaxies.
Subsequent research has confirmed Zwicky’s basic observation. Our best estimate today is that dark matter comprises 26.8% of the universe.
But that still leaves the majority of the cosmos unaccounted for. What could it be?
The remaining 68.3% is thought to be dark energy, a completely unexplained force that appears to be causing the universe to expand at an ever-accelerating pace.
Dark energy is far less dense than either regular or dark matter. But on large scales, it seems to dominate our universe because its evenly spread across all of space – even the vast “empty” voids between galaxies.
Strictly speaking, it may be more accurate to describe dark energy as a feature of space itself rather than as some separate force. Then again, Neil deGrasse Tyson and others have mused that dark energy may actually be the gravitational impress of another universe bleeding into our own.
We just don’t know enough to say.
I could probably write a whole article just about how freaky weird black holes are.
The off-the-shelf explanation of black holes is that theyre the ghostly remnants of extremely large stars.
Stars are engaged in a constant war against their own gravity. Through nuclear fusion, they are able to generate enough outward energy to keep from collapsing under their own crushing weight.
But fusion turns lighter elements into heavier ones. When a very large star reaches a critical mass threshold, the outer layers explode in a supernova, while the core collapses to a point so dense that not even light can escape from its monstrous gravity.
But this is only part of the story. We might understand something about how and why black holes form, but there is much we don’t know – or maybe can’t know.
To begin with, there are different types of black holes, and they may form in different ways.
First, there are stellar-mass black holes. They form via the process I described above – from the implosion of gargantuan stars. These black holes generally have a mass between 5-30 times that of the sun.
But there are also supermassive black holes. These monsters, weighing millions or billions of times more than our sun, are found at the centers of most large galaxies – including the Milky Way. That would seem to suggest that they have their origins in the very early cosmos – maybe even before the galaxies themselves. How? Why? Who knows.
More recently, scientists have discovered intermediate-sized black holes, which may be several thousand times the mass of the sun, but are still substantially smaller than the supermassive black holes that serve as galactic centrepieces. Their provenance is still debated.
But perhaps the greatest mystery of all lies inside the black hole. Classical physics suggests that the heart of a black hole is a singularity – a point of infinitely small size, and infinite density. This marks the end of our traditional understanding of spacetime. All known laws and norms break down under such conditions, and we are powerless to predict what actually goes on there.
Matter that gets sucked into the heart of a black hole leaves the universe as we know it, bequeathing only the whisper of its gravity.
But many physicists insist that there’s no such thing as a singularity, positing instead that we simply lack the theoretical framework necessary to describe the true nature of black holes.
If that is the case, then the real singularity is our own ignorance.