While we’re gazing up at the stars, most of us don’t often think much beyond the gently twinkling canopy of stars or the steady points of light from planets and their moons.
But looking beyond the familiar we find a host of stellar objects that are stranger than we can suppose. Let’s look a little closer at some space oddities that are enough to blow even Ziggy Stardust’s mind.
Neutron stars
After black holes, neutron stars are the niftiest, smallest and densest known objects in the universe.
Imagine: our Sun has over 300,000 times Earth’s mass (and it’s on the lower end of the scale for stars). Now, imagine squeezing the entire mass of our Sun into a sphere just 20 kilometres across. That’s a neutron star.
Neutron stars form from supernovas, the cataclysmic collapse of massive dying stars, their core compressing to an unbelievably dense, hot form.
These stars spin at spectacular speeds, sometimes hundreds of times per second, possess powerful magnetic fields, and newly-formed neutron stars may have surface temperatures of more than ten million Kelvin.
Pulsars
Pulsars are rapidly spinning neutron stars that pulse beams of radiowaves like a lighthouse. Astronomer Jocelyn Bell-Burnell spotted the first pulsar when she noticed a strange signal in the telescope data she was studying.
Astronomers use pulsars to investigate the universe because these pulses come at precise intervals. Fluctuations in their signals’ timing give astronomers information about what the pulses have travelled through on their journey to Earth.
In the words of Bell-Burnell herself, “scientists use them to test theories of relativity on a cosmic scale. Einstein’s theories are checking out pretty well so far.”
White dwarfs
Most white dwarfs are the dim cores of dead stars not nearly massive enough to become neutron stars. When exploding stars finish shedding their outer layers to form planetary nebula, a white dwarf is what’s left.
White dwarfs are invisible to the naked eye and, even through telescopes, are some of the dimmest stars in globular clusters. But occasionally, white dwarfs are visible in binary systems, and that’s when things get interesting.
Sometimes, when a white dwarf pulls gas from a companion star, this builds up until it ends in a violent explosion. These range in size from a supernova to much smaller explosions that can happen repeatedly.
While White dwarfs start incredibly hot, over billions of years, they stop producing heat or light. The end object, a ‘black dwarf’ star, is still theoretical because the universe hasn’t yet existed long enough for it to happen.
Brown Dwarfs
Brown dwarfs are sometimes unfairly and inaccurately called failed stars. They’re bigger than gas-giant planets but smaller than stars, yet still produce their own light.
The stars aren’t massive enough to start nuclear fusion of ordinary hydrogen into helium in their cores. This means many are much cooler than stars and much dimmer in visible light because of it.
Hunting these enigmatic “substars” produced nothing for a long time, but things changed with improved instruments and techniques. Astronomers have identified many brown dwarfs using infrared surveys of the sky, though they get more puzzling the more we find.
Fast Radio Bursts
Fast radio bursts are perhaps the strangest of all, with astronomers still asking “what are fast radio bursts?”
We do know that FRB are some of the brightest bursts of radio waves ever detected and last mere milliseconds. FRB are incredibly powerful, releasing more energy in a fraction of a second than the Sun in an entire day. Despite this, the signals are extremely faint when they reach Earth. Debate rages around FRB—including whether there might be different types.
Possible culprits for FRBs include magnetars, merging white dwarfs, and colliding galaxies. But even as astronomers float one promising theory, another FRB will upend everything.
While these stellar oddities might remain invisible to the naked eye, their discovery and observation through telescopes expands our understanding of the universe’s diverse and dynamic nature.
Next time you’re out stargazing somewhere dark, remember that these fascinating space oddities are out there, amongst the familiar stars, waiting to be uncovered by astronomers.
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Jay Chesters
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