What’s Scarier… Halloween or the Universe?
'Cheshire Cat' galaxies. Credit: NASA/CXC

What’s Scarier… Halloween or the Universe?

24/10/2018Written by Tori Tasker

Please meet the scariest objects in the universe: black holes, creepy nebulas, and dark matter.

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mascot Telescope Right
'Cheshire Cat' galaxies. Credit: NASA/CXC

From our perspective here on Earth, the universe is stunning.

It’s filled with the majestic births and deaths of stars, planets, and galaxies, captured frozen in time by our telescopes both in space and on the ground.

Up close however, these beautiful objects can get a bit frightening.

Please meet the scariest objects in the universe: black holes, creepy nebulae, and dark matter.

Beastly black holes

Beastly black holes
Simulated black hole. Credit: Alain R
Beastly black holes
Sagittarius A*, centre of the Milky Way. Credit: NASA/CXC/Univ. of Wisconsin/Y.Bai. et al.

A black hole is an incredibly dense object that’s impossible to escape from once you’re too close. Pass within a black hole’s ‘event horizon’ and its gravity is so strong that not even light can escape. This is why we call it a black hole: it’s something we can’t directly see in space.

But that doesn’t mean we can’t find them. For a long time, black holes were simply a theoretical idea, but thanks to telescopes like Hubble, we have confirmed that black holes really do exist in the wild.

To find a black hole, we look at its interaction with the matter and light surrounding it. To find a lonesome black hole, one not part of a galaxy, its gravitational pull will distort light from nearby stars and galaxies. However, the biggest black holes are generally found at the centres of galaxies. In this image we can see the black hole at the centre of our Milky Way, known as Sagittarius A*. To find a black hole such as ours, we look for something called an accretion disk. This is when all the gas and dust heats up as it falls in towards the black hole. Sometimes it gets so hot that it emits high-energy light such as X-rays, and our telescopes can then spot it.

If, like the gas and dust around a black hole, we were to fall into a black hole, our bodies would become spaghettified! Our limbs would stretch like spaghetti because the pull of gravity changes depending on how close you are to the black hole. Your feet would feel a stronger pull than your head until eventually you were ripped apart!

Black holes are created when massive stars reach the end of their lives and gravitationally collapse in on themselves. This means the gravity of the star becomes too strong compared to the pressure inside the star, as it runs out of fuel to burn. The star then collapses in on itself and becomes a black hole. It grows larger by drawing in any nearby gas, dust, or wayward star.

Creepy nebulae

Creepy nebulae
Red Spider Nebula. Credit: ESA/Garrelt Mellema
Creepy nebulae
Tarantula Nebula. Credit: TRAPPIST/E.Jehin/ESO

Did you know that creepy crawly spiders lurk not only under your bed but also in the night sky?

The Red Spider and Tarantula nebulae have been lurking in the universe for thousands of years. They are birth places for many stars, so perhaps they aren’t quite as scary as their names imply. But you wouldn’t want to get too close to the Red Spider Nebula as its powerful winds from new-born stars can reach up to 300 kilometres per second! It is these stellar winds that give this nebula its spidery shape.

The Tarantula Nebula brings its own frightening personality to the sky by being the largest and most violent star forming region in the entire Local Group of galaxies.

The Red Spider and Tarantula nebulae bring both beauty and fright to our deep night skies.

Ghostly dark matter

Ghostly dark matter
Abel 250 cluster, with dark matter shown in blue. Credit: NASA, ESA, CFHT, CXO
Ghostly dark matter
Andromeda spiral galaxy. Credit: Adam Evans

The ghostly spectres of our universe are none other than dark matter and dark energy. They are invisible to us yet make up around 95 percent of our universe. It’s quite daunting to think that everything we know of in the universe is less than 5 percent of what’s really out there.

Dark matter and dark energy may be invisible, but just like ghosts, they pop up anywhere and everywhere!

Dark matter can be ‘seen’ in the rotation of galaxies. Theories predicted that stars and dust on the outskirts of a galaxy should spin slower than those in the centre of the galaxy. Observations, however, proved this to be untrue, so there must be some mysterious form of matter in the galaxy to make everything spin at the same speed regardless of where in a galaxy it is located. We call this dark matter.

It doesn’t emit any light and we don’t yet know what it’s made of. It is a mystery we are constantly searching to solve!

Halloween here on Earth can be pretty scary, but we’re willing to bet that our universe has even more frightening characters. But for everything scary, it brings equal amounts of beauty, majesty, and wonder.

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About the author: Tori Tasker is the Public Programmes Team Leader at the National Space Centre.