Back for another night? I'm glad. Pull up the blanket, because I've gathered ten more corners of the cosmos that we haven't explored together yet.
Tonight's path runs past a black-hole jet that stretches for thousands of light-years, a neutron star whose magnetic field makes atoms behave strangely, an asteroid carrying some of the chemical ingredients of life, tiny galaxies bursting with new stars, and a pulsar that gave us the first evidence for gravitational waves. Near the end, we'll find our own motion written into the oldest light in the universe, and face one of cosmology's deepest puzzles: why most of the universe seems to be made of something we can't identify.
Settle in. 🌙
1. 🌌 M87's jet extends thousands of light-years from its black hole
The supermassive black hole in Messier 87 became famous as the first black hole whose shadow was imaged by the Event Horizon Telescope. But the structure streaming out of its neighborhood is vastly larger than that shadow.
M87 launches a relativistic jet that stretches for thousands of light-years.
The jet doesn't come from inside the event horizon. Instead, magnetic fields in the hot, swirling plasma just outside the horizon tap energy from the inflowing gas, and probably from the black hole's spin, and channel particles outward at nearly the speed of light.
So the tiny region the Event Horizon Telescope photographed is physically connected to a glowing structure that reaches deep into an entire galaxy.
A black hole's immediate surroundings can shape a region of space millions of times wider than its horizon.
2. 🧲 Magnetar magnetic fields distort atomic structure
Magnetars have magnetic fields reaching roughly 10¹⁰–10¹¹ tesla near their surfaces. Fields that intense break our everyday intuition about atoms.
On Earth, an atom's electron cloud is shaped mainly by electric forces. Near a magnetar, the magnetic field can become strong enough to reshape the electron orbitals, stretching atoms out along the field lines. At still more extreme strengths, quantum electrodynamic effects kick in, and even the vacuum behaves in unfamiliar ways.
We can't produce sustained magnetar-strength fields in a laboratory, so the universe runs the experiment for us.
A magnetar isn't just a star with a souped-up version of Earth's magnetic field. It's a place where magnetism becomes one of the main forces deciding the shape of matter itself.
3. 🪨 Asteroid Ryugu contains ingredients used by biology
Japan's Hayabusa2 spacecraft collected material directly from asteroid Ryugu and brought it back to Earth in 2020.
Because the samples were gathered in space and carefully sealed, scientists could study primitive asteroid material with far less worry about earthly contamination than with meteorites picked up off the ground.
The samples contain organic compounds, including uracil, one of the nucleobases used in RNA, as well as niacin and many amino-acid-related compounds.
This isn't evidence that Ryugu holds, or ever held, life. The importance is subtler: chemistry that makes some of biology's molecular ingredients happens naturally in lifeless Solar System material.
Some of the building blocks later used by life on Earth may have been forming inside asteroids before our planet had even finished becoming a planet.
4. 🌌 "Green pea" galaxies are tiny factories of new stars
Citizen scientists taking part in the Galaxy Zoo project noticed unusual little green objects in astronomical images. They nicknamed them green pea galaxies.
Their green look in survey images comes largely from extraordinarily strong emission by ionized oxygen, which falls into the green color channel.
These compact galaxies are forming stars at remarkably high rates for their small size. Their low metallicities and intense radiation make them useful nearby stand-ins for galaxies in the early universe, and some leak significant amounts of ionizing radiation, helping astronomers understand how ancient galaxies may have contributed to cosmic reionization.
A handful of volunteers noticing strange green dots on their screens helped uncover nearby laboratories for conditions that existed billions of years ago.
5. 🧲 A pulsar helped provide the first indirect evidence for gravitational waves
Long before LIGO detected a gravitational wave directly, astronomers already had compelling evidence that gravitational radiation was real.
In 1974, Russell Hulse and Joseph Taylor discovered the binary pulsar PSR B1913+16. By timing its radio pulses with exquisite precision, astronomers measured its orbit, and found the orbital period slowly shrinking.
The rate matched Einstein's prediction for energy carried away by gravitational waves, to extraordinary precision. Hulse and Taylor later received the Nobel Prize.
For decades, we knew gravitational waves were real not because we'd detected the waves themselves, but because we watched two dead stars gradually fall toward each other exactly as if invisible ripples were stealing their orbital energy.
6. 🪐 The exoplanet Beta Pictoris b was photographed moving around its star
Beta Pictoris is a young nearby star wrapped in a spectacular debris disk, and inside that system lies the giant planet Beta Pictoris b.
Astronomers imaged it directly and kept watching for years. The images showed the planet changing position along its orbit.
That sounds mundane until you consider the scale. Beta Pictoris lies about 63 light-years away, and the planet is lost in the glare of a star vastly brighter than it. Adaptive optics, coronagraphs and infrared imaging still let us watch an alien planet physically travel along part of its orbit.
We're used to animations of exoplanet systems. Beta Pictoris b belongs to the select group for which the orbital motion itself shows up in real astronomical images.
7. 🌠 The Tunguska explosion was probably an asteroid exploding in the atmosphere
On 30 June 1908, something exploded in the sky over Siberia near the Tunguska River. The blast flattened roughly 2,000 square kilometers of forest, yet investigators found no great impact crater.
The leading explanation is an airburst: a small asteroid, perhaps tens of meters across, hit Earth's atmosphere at cosmic speed and blew apart several kilometers above the ground, releasing energy comparable to a large nuclear weapon.
Tunguska shows why planetary defense isn't only about kilometer-wide, extinction-class asteroids. A fairly modest object can devastate an area the size of a city without ever reaching the ground in one piece.
It's a reminder that Earth's atmosphere is both a shield and, in extreme cases, the place where the explosion happens.
8. 🕳️ Quasars can outshine entire galaxies
A quasar can come from a region roughly the size of our Solar System, yet radiate more energy than hundreds or thousands of billions of stars.
The engine is a feeding supermassive black hole. Gas falling inward forms a hot accretion disk, where friction, magnetic turbulence and relativistic effects turn gravitational energy into radiation with enormous efficiency.
Because quasars can be seen across most of the observable universe, they serve as beacons lighting up cosmic history. Some already existed when the universe was less than a billion years old.
The contrast is worth lingering on. A galaxy may hold hundreds of billions of stars spread across 100,000 light-years. Yet the activity around one central black hole can become so intense that the rest of the galaxy is visually overwhelmed.
9. 🌌 The cosmic microwave background has a tiny dipole caused by our own motion
The cosmic microwave background is almost perfectly uniform in every direction. But one side of the sky is slightly warmer and the opposite side slightly cooler. This large-scale pattern is called the CMB dipole.
The leading explanation is beautifully simple: we're moving relative to the frame in which the CMB looks the same in all directions. Our motion Doppler-shifts the microwave photons slightly up in energy ahead of us and down behind us.
The effect shows that the Solar System is moving at roughly 370 km/s relative to the CMB.
So cosmology hands us a universal speedometer. By measuring a temperature difference of only a few thousandths of a kelvin across the sky, we can work out how fast our corner of the universe is moving relative to ancient light from the Big Bang.
10. 🌌 Dark energy appears to dominate the universe
In the late 1990s, astronomers studying distant Type Ia supernovae expected to measure how much cosmic expansion was slowing down under gravity. Instead, they found evidence that it's speeding up.
The unknown cause got a deliberately vague name: dark energy. In the standard cosmological model, it makes up roughly two-thirds of the universe's total energy density.
A cosmological constant, energy built into empty space itself, is the simplest explanation that fits much of the current evidence. But we don't understand why its observed value is so tiny compared with naive quantum-field-theory expectations.
Modern surveys keep testing whether its behavior might change over cosmic time, and recent results from the DESI survey have hinted that it might.
We've given the dominant component of the universe a name. That shouldn't be confused with understanding it.
🌙 One last thought before you sleep
Tonight, think about the darkness between the stars. It looks empty.
But passing through your room right now are photons from the cosmic microwave background, neutrinos streaming out of the Sun's core, cosmic rays from distant accelerators and, almost certainly, gravitational waves far too weak for you to feel.
Earth is traveling around the Sun at roughly 30 kilometers per second. The Sun is carrying us around the Milky Way at roughly 230 kilometers per second. And our galaxy is moving relative to that ancient cosmic background at hundreds of kilometers per second.
You feel none of it. Your pillow feels still. Your room feels still. The night feels still.
Yet "stillness" only exists relative to whatever you've chosen to call stationary.
There may be no better thought to fall asleep on: you can lie completely motionless while the universe carries you through space.
That's the last stop for tonight. Thanks for drifting along with me. Good night, and clear skies. 🌌
— Kasi