Black Hole Coming Toward Earth – Is Our World Going to Smash to a Million Pieces?

The closest black hole coming toward Earth is Gaia BH1. It’s three times closer than the next nearest black hole at only 1,560 light-years away. But is it really coming for us? And if it is, what can we do about it? 

Scientists use different technologies to detect black holes, which we’ll explore below. Today we’re investigating the closest black hole and what it means to Earthlings. Could our home planet be sucked right in? Is that even possible? Let’s jump right in with how black holes form and how scientists find them.

How Do Black Holes Form?

Most black holes form when a giant star dies in a supernova explosion. This explosion happens in stars with about three times the Sun’s mass, while smaller dying stars turn into dense neutron stars.

The massive stars burn all their nuclear fuel and collapse under gravity’s influence. But as it collapses, the star’s surface reaches an imaginary surface or “event horizon.” If you were watching from far away, it would appear that time stands still and the collapsing star freezes in space.

Supermassive black holes come from stellar collisions. If a black hole collides with a neutron star, it produces a supermassive (but still invisible) black hole.

Scientists think there are countless stellar mass black holes throughout the Universe. They range in size from about 10 to 24 times the Sun’s mass. And researchers usually find them when a star gets close enough to the black hole’s gravity to get tugged toward it, emitting X-rays as it goes. Scientists judge the number of stellar black holes ranges from ten million to billions, based on the number of stars (in the Milky Way alone) large enough to produce them.

Detecting Black Holes

There are four primary ways astronomers detect black holes. Let’s delve into it.

How to Detect A Black Hole Coming Toward Earth: X-Ray Light Emissions

It’s tricky searching for black holes since you can’t see them. But one method scientists use to detect black holes is by searching for the X-rays of hot gas disks that swirl toward black holes. Particles within the disk experience friction that heats them to millions of degrees, where they produce X-rays. 

Scientists find these disks in binary star systems where a regular star remains in a close orbit around a stellar black hole. They also find them around the supermassive black holes in the galaxies’ centers.

NASA uses the Chandra X-Ray Observatory to detect matter around black holes, galaxy clusters, and exploded stars. It is a specifically designed telescope that detects X-ray emissions from the Universe’s hottest regions.

In conjunction with the Event Horizon Telescope (EHT), Chandra captured the first image of an event horizon on the black hole within M87, an elliptical galaxy in the constellation Virgo. But don’t worry, this black hole isn’t coming toward Earth since it’s some 54 million light-years away!

The EHT is a network of global radio antennae observatories that combine as one telescope with an Earth-sized aperture to observe the radio light (X-rays) associated with black holes. Over its twenty-year mission, Chandra returned to study M87 many times, and it sees a much wider field of view than the EHT. Chandra’s image on the left below has a plus sign, “+,” to mark the EHT image location on the right.

Black Hole Coming Toward Earth
Image: Left: NASA, CXC, and SAO; Right: Event Horizon Telescope Collaboration

Since scientists can’t directly observe black holes, they can observe nearby matter and how it is affected. For example, when a black hole passes through an interstellar matter cloud, it accretes the matter or draws it inward.

The same type of process happens if a star passes near a black hole. Gravity pulls the star toward the event horizon and can tear it apart. Then, as the attracted matter speeds up, it heats to incredibly high temperatures. And finally, it emits X-rays that radiate into the space around it. This phenomenon is what scientists observe. Intense bursts of gamma rays flow through the area around black holes while the invisible masses devour nearby stars.

How to Detect A Black Hole Coming Toward Earth: Star Observation

Scientists used data from ESA’s Gaia mission to discover Gaia BH1 and Gaia BH2 by a new method. They’re respectively located in the direction of the constellation Ophiuchus at 1,560 light-years away and in the Centaurus constellation, 3,800 light-years from Earth. In terms of the entire galaxy, these black holes are in our cosmic backyard.

Researchers found the closest black hole coming toward Earth by observing an individual star over time. In doing so, they detected unusual patterns in how the star moved through the sky.

The companion stars of both black holes wobbled in a helix-like shape, moving like they were orbiting an invisible mass. Scientists determined that the stars orbited a non-light-emitting object with ten times the Sun’s mass, significantly influencing it. In other words, they decided the stars circle enormous black holes. They ruled out other massive companions, such as double-star systems, since the objects emitted no light.

How to Detect A Black Hole Coming Toward Earth: Star Observation
Image: ESA Gaia

Scientists think NASA’s upcoming Nancy Grace Roman Telescope will detect closer and more numerous black holes coming toward Earth. In addition to a broader viewing lens than Hubble, the Roman Telescope will also use microlensing to see dark matter, which we’ll discuss below.

How to Detect A Black Hole Coming Toward Earth: Gravitational Waves

The universe consists of a chaotic ocean of ripples in space-time. Those ripples are gravitational waves. And astronomers use the Fermi Gamma-ray Space Telescope and LIGO detectors to find them. Fermi detects gamma rays, light’s highest-energy form, while LIGO is the Laser Interferometer Gravitational-Wave Observatory. 

When black holes orbit one another or when stars orbit them, astronomers believe surrounding gravitational waves are light-years long. The waves have specific frequencies and amplitudes depending on the masses and their separations of the orbiting objects. LIGO detectors started operations in 2015, finding dozens of black hole pairs since then.

LIGO’s teams are developing software for early-warning systems to raise quick awareness about neutron star mergers. And from here, they might be able to predict cosmic collisions before they happen. So we’ll know if an unlikely black hole is coming toward Earth.

How to Detect A Black Hole Coming Toward Earth: Gravitational Waves
Image: LIGO and Caltech

How to Detect A Black Hole Coming Toward Earth: Gravitational Microlensing

The last method we’re discussing for detecting black holes hasn’t been highly successful thus far. But gravitational microlensing holds promise for revealing more black holes than science has discovered yet.

Scientists can now find black holes based on binary stars or systems nearby. But there are indeed multitudes of black holes without another object in their orbit or close cosmic neighborhood. However, every Universe mass, black holes included, exerts a gravitational influence on the space around it. Space curves around mass, wherever that mass happens to lie.

Scientists know that at some point in time, a black hole and telescope will align with a background light source (distant galaxy or star.) It often happens when one planet moves before a star or when the Sun and Moon eclipse one another.  

So when it happens, the background light appears brighter and then distorts due to curved space-time effects. And that phenomenon is gravitational lensing, or microlensing for small point masses. It enables scientists to reconstruct foreground mass properties, even when the mass is invisible, like a black hole coming toward Earth.

Check out this quick illustration of a free-floating planet coming before a star and distorting its background light. Scientists can use gravitational microlensing to detect black holes in the same way. The black hole will reveal itself when it comes between Earth (or a space-based telescope or observatory) and a bright star. Since the black hole’s gravity bends the space around it, the star’s light travels through the warped space and appears oddly, almost like a cosmic doughnut.

Simulated visualization of a gravitational lensing by a free-floating planet in the Galaxy

Credit: Jan Skowron, Astronomical Observatory, and University of Warsaw.

What Happens As A Star Gets Eaten By A Black Hole?

In December 2022, several NASA telescopes observed a massive black hole tearing apart a nearby star, essentially eating it. Astronomers found the pair in the center of another galaxy, about 250 million light-years away.

After the black hole’s gravity ruptured the star, scientists saw an increase in high-energy X-ray light around the pair. The radiation indicated the intense heat of the stellar material as the black hole pulled it toward its doom. Then, a scorching corona formed around the black hole.

NASA’s Nuclear Spectroscopic Telescopic Array (NuSTAR) satellite observed the light’s wavelengths and provided a never-before-seen view of the forming and evolving corona. A star’s destruction by a black hole is called a tidal disruption event, and NuSTAR’s observations help researchers better understand what happens when black holes capture neighboring objects.

From start to finish, tidal disruption events (TDE) can take a few weeks or months. And that short duration makes them attractive to researchers since they can use observations to understand how the black hole’s immense gravity manipulates surrounding material. The observations yield real-time views of a massive black hole feeding on its cosmic neighbors while lurking about in the center of the galaxy. It sounds rather ominous and like a science fiction space documentary! The black hole is coming toward Earth, so save your women and children! And while Earth isn’t very likely to get eaten by a black hole, it’s just the sort of movie that makes you perch on the edge of your seat.

AT2021ehb Tidal Disruption Event

The illustration below depicts a tidal disruption event, AT2021ehb, first spotted in March 2021. The TDE occurred between a star and a gigantic black hole about 10 million times more massive than the Sun. The side of the star nearest the black hole got pulled so hard it stretched to become a long hot gas noodle (scientists call it spaghettification.)

Researchers studying the event think the gas stream got whipped around, colliding back on itself. It created shock waves and gas flows so intense as to generate visible, ultraviolet, and X-ray light. Then the material settled into a rotating disk, swirling around the black hole like water circles a drain. And while it stirred, the friction generated lower-energy X-rays that formed a corona, like in the illustration below.

All of this activity happens relatively quickly. AT2021ehb took just over one hundred days for the black hole to consume the star.

AT2021ehb Tidal Disruption Event
Image: NASA and JPL Caltech

Conclusion: Is A Black Hole Coming Toward Earth?

There is no threat, now or foreseen, of a black hole coming toward Earth. But that doesn’t lessen the danger that black holes cause for objects lying near their destructive paths.

Black holes are born when an enormous star explodes into a supernova, collapsing in on itself to form a singularity. The event horizon gives scientists an idea of the black hole’s enormity because the larger it is, the larger the hole.

Scientists detect black holes by the surrounding material and do it in one of four primary ways.

  • X-ray light emissions: As a black hole attracts surrounding matter, say a star, gravity pulls the object closer. As it stretches and speeds up, the stellar matter reaches intensely hot temperatures and then emits X-ray light, which scientists can capture.
  • Stars behave with erratic orbits when submitted to the gravity of a nearby mass. When scientists can’t see the mass, they can rule out other options until they know the star’s behavior comes from a black hole.
  • All objects create gravitational waves or ripples in space-time. Scientists use LIGO to detect the waves and detect black hole pairs.
  • Gravitational microlensing occurs when an object passes between Earth and a bright background source. The background light reacts to gravity, alerting astronomers of a mass in is foreground.

And finally, black holes cause tidal disruption events that last a relatively short time, weeks to months. During that period, researchers study the black hole feeding on a star to learn what might happen to Earth if a black hole drifted a little too close.