A black hole is an object so compact that nothing can escape its gravitational pull. Not even light. On Earth an object needs to be launched with a speed of 11 km/s if it is to escape the planet's gravity and go into orbit. But the escape velocity of a black hole exceeds the speed of light. Since nothing can travel faster than this ultimate speed, black holes suck in everything including light, which makes them utterly dark and invisible. In this image, we can see a black hole, but only because it is surrounded by a superheated disc of material, an accretion disc. The closer to the hole the material gets, the more and more of its light is captured, which is why the hole grows darker towards its cente.

140891305

A black hole is an object so compact that nothing can escape its gravitational pull. Not even light. On Earth an object needs to be launched with a speed of 11 km/s if it is to escape the planet's gravity and go into orbit. But the escape velocity of a black hole exceeds the speed of light. Since nothing can travel faster than this ultimate speed, black holes suck in everything including light, which makes them utterly dark and invisible. In this image, we can see a black hole, but only because it is surrounded by a superheated disc of material, an accretion disc. The closer to the hole the material gets, the more and more of its light is captured, which is why the hole grows darker towards its cente.

Photo by: Science Photo Library - MARK GARLICK

Science Photo Library - MARK GARLICK

Too Big to be a Neutron Star, Too Small to be a Black Hole. What Am I?

Okay, stars die in all sorts of interesting and cosmically expressive ways (except the red dwarf stars, who just sort of…stop).

July 08, 2020

The most massive stars die in fantastic and titanic supernova explosions, leaving behind a dead remnant of what was once a beautiful factory of fusion.

Birth of a Neutron Star

If conditions are right, the core inside a massive star experiences an extremely uncomfortable gravitational squeeze, so impressively powerful that the force is able to shove electrons into protons, turning the whole core into a giant city-sized ball of neutrons: a neutron star. The birth of that neutron star triggers (through a variety of complex and not-yet-fully-understood physics) the supernova explosions that we see throughout the universe. And when the party’s over, the neutron star is left behind to wait around and stare at the cosmos for eons.

But if the gravity is way too strong, even that ball of stubborn neutrons gets crushed, leading the formation of one of the most enigmatic objects in the entire universe: a black hole.

Black hole or a neutron star and pulling gas from an orbiting companion star.

679607618

Black hole or a neutron star and pulling gas from an orbiting companion star.

Photo by: Pitris

Pitris

We’ve been observing neutron stars for decades (because they glow brightly), and black holes for less so (because they don’t). The best way to catch a black hole is to wait for it to randomly crash into another one, an event that sends out a few bajillion gigatons worth of energy in the form of gravitational waves – ripples in the fabric of spacetime itself, which we can detect with extremely expensive/sensitive instruments like LIGO.

Is It a Neutron Star?

LIGO has observed dozens of mergers, but the latest one is causing a stir: one of the objects has a mass of merely 2.6 solar masses (which means it weighs 2.6 times as much as the sun).

Here’s why it’s a stir. We don’t fully understand what goes on inside neutron stars – the physics of giant, super-dense balls of neutrons gets a little bit weird – but our best guess as to an upper limit for them is just a hair above 2 solar masses. Anything bigger, and the exotic quantum forces holding them up should fail, leading to the formation of a black hole. So the object that LIGO saw merge is too big to be a neutron star.

Or Black Hole?

Neutron stars are the end points of stars whose inert core's mass after nuclear burning is greater than the Chandrasekhar limit for white dwarfs, but whose mass is not great enough to overcome the neutron degeneracy pressure to become black holes

495668455

Neutron stars are the end points of stars whose inert core's mass after nuclear burning is greater than the Chandrasekhar limit for white dwarfs, but whose mass is not great enough to overcome the neutron degeneracy pressure to become black holes

Photo by: 7activestudio

7activestudio

But it takes a lot to make a black hole. Supernovas and the deaths of giant stars are, well, energetic events, and most of the dying star gets flung out into the vastness of space, not crammed down into a tiny little sphere. We don’t fully understand what happens during supernovas – the physics giant, exploding balls of plasma gets a little bit weird too – but our best guess as to a lower limit for black holes is around 5 solar masses. The universe just has a really hard time making black holes smaller than that. So the object that LIGO saw merge is too small to be a black hole.

Surprise!

Too big to be a neutron star, too small to be a black hole. It’s a riddle all right.

Either we’re getting the detailed physics of neutron star interiors wrong, and they can be bulkier than we thought (which wouldn’t be a surprise), or we’re getting the detailed physics of supernovae wrong, and giant stars can pop out small black holes if they feel like it (which also wouldn’t be a surprise).

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

Or both. Both is definitely an option.

Next Up

How to Save Humanity from Extinction

Here are some goals we need to achieve if we want to reach our 500,000th birthday as a species.

Quiz: Test Your Space Exploration Knowledge

Ahead of the historic May 27th NASA and SpaceX crewed space launch, test your space exploration knowledge!

How 3D Print Building is Changing the Future

Building with 3D printing technology is sparking widespread interest in the construction industry. Besides reducing waste and our impact on the environment, it can speed up construction from weeks, or months, to days. Projects that use simple raw materials like soil, straw, and even salt, can be built in a fraction of the time and cost of traditional construction.

Extreme Weather Tests the Durability of Solar and Wind Power

As category four Hurricane Ian swept across the Caribbean into south west Florida on 28 September 2022, knocking out Cuba’s electricity grid along the way, hundreds of thousands of homes were hit by flooding and power loss. In contrast, the solar-powered community of Babcock Ranch 24 miles to the north of coastal town Fort Myers survived intact.

India’s Space Agency is Going Big… By Going Small

Astrophysicist Paul M. Sutter shares the latest in the world of rocket launches and what India’s SSLV is all about.

Voyager 2 is Really Far Out There, Man

Currently Voyager 2 is about 11 billion miles from the Earth, and has been traveling at speeds of tens of thousands of miles per hour since its launch in 1977. Read more to see where it is now and what we've learned.

The Perseid Meteor Shower Reaches its Peak

Stargazers rejoice! The annual Perseid meteor shower is upon us. Here's what you need to know...(updated August 11, 2022)

SpaceX vs. the Universe

Fans of space are having a tough time picking sides over a recent controversy between SpaceX and astronomers. But what's the big debate all about? Astrophysicist Paul M. Sutter digs into both perspectives.

NASA and SpaceX are Going on a Date, and We're All Invited

Save the date--On May 27th, if everything goes as planned, a rocket will launch from Kennedy Space Center in Cape Canaveral, Florida. Watch SPACE LAUNCH LIVE: AMERICA RETURNS TO SPACE on Discovery and Science Channel starting at 2P ET.

2020: A Year of Big Leaps for Mankind

Here are a variety of some amazing space launches to look forward to in 2020.

Related To: