What Are Black Holes?

Updated on May 9, 2019
Larry Slawson profile image

Larry Slawson received his Masters Degree at UNC Charlotte. He specializes in Russian and Ukrainian History.

Artist rendering of Supermassive Black Hole.
Artist rendering of Supermassive Black Hole. | Source


Black holes refer to a region of space that exhibits such strong gravitational force that nothing (not even light) can escape from its grasp. But what exactly are black holes? Where do they come from? Finally, and perhaps most importantly, why are they important in understanding our overall universe? This article, through an analysis of current theories and research, explores the concept of black holes in an attempt to better understand not only their origins, but also their place and importance within the universe at large. Although theories pertaining to black holes remain limited, given the lack of data and empirical observation of these space entities, this article aims to provide its readers with a fundamental understanding of current hypotheses that dominate the scientific community today.

Black Holes Defined

Although the name “black hole” gives rise to the concept of “nothingness,” black holes are anything but empty. Scientists believe that the holes contain tremendous amounts of matter, and may result from the death of massive stars. Once a massive star dies, implodes, and undergoes a supernova explosion, it is believed that they sometimes leave behind a small, but dense remnant core that is approximately three times the mass of our Sun (science.nasa.gov). The result of such mass (in a relatively small space) is an overwhelming force of gravity that overcomes all objects that surround it (including light), creating the appearance of a black hole.

The concept of black holes is nothing new within the scientific community, as scientists and astronomers from the Eighteenth Century (most notably, John Michell) proposed that such objects may exist in our universe. In 1784, Michell argued that black holes were likely the result of Stars whose diameter exceeded the diameter of our Sun by a factor of 500. He also correctly observed that the holes could potentially be observed through an analysis of their gravitational pull on nearby celestial bodies. Michell remained perplexed, however, over how a supermassive object could effectively bend light. Albert Einstein’s theory of “general relativity” (1915) later helped demonstrate how this was possible. Expanding on Einstein’s theory, German physicist and astronomer, Karl Schwarzschild, helped develop the first modern version of what a black hole was in 1915, arguing that “it was possible for mass to be squeezed into an infinitely small point” that would not only bend spacetime (due to its incredible gravitational pull), but would also prevent “massless photons of light” from escaping its grasp as well (sciencealert.com). Despite his theories, however, credit for the term “Black Hole” lies with physicist John Wheeler, who first proposed the name in December of 1967.

Artist rendering of black hole.
Artist rendering of black hole. | Source

Types of Black Holes

Currently, there are five types of black holes that have been identified by astronomers. These include miniature, stellar, intermediate, primordial, and supermassive black holes. No black hole, however, is alike as some (such as the supermassive black hole at the center of the Milky Way) contains masses that are equivalent to several billion Suns, while miniature black holes (which remain only theoretical at this time) are believed to be quite smaller in mass.

Scientists also believe that black holes change in size throughout their lifetime as well, growing with the absorption of gas, dust, and objects (including planets and stars) that pass by their event horizon (point where nothing can escape from the black hole’s pull). Scientists have also theorized that black holes can merge with other black holes. This merger would help to explain the size of supermassive black holes that exist throughout the universe.


Primordial black holes are believed to be ancient (as the name implies) as they likely formed soon after the Big Bang occurred. It is likely that the first primordial black holes were extremely small, with many evaporating over time. Other primordial holes, with larger masses, may still exist today. However, such speculation remains only a theory at this time, as no primordial black hole has been detected or observed in the visible universe so far. Some scholars, such as the late Stephen Hawking, believe that primordial black holes may hold the key to understanding “dark matter” in the universe.


The most common form of black holes are stellar-mass objects. It is believed that stellar-mass black holes result directly from supernova explosions, caused by the implosion of a supermassive star once it exhausts all of its internal fuel sources. For this reason, stellar-mass black holes are often found scattered throughout the galaxy. Stellar-mass black holes are approximately five to ten times the mass of our Sun. However, recent scientific research has indicated that some stellar-mass black holes may reach sizes up to 100 times the mass of our Sun.


These black holes range in size from hundreds to several hundred-thousand times the overall mass of our Sun. Although none have ever been detected with a high-level of certainty, there is abundant evidence to support their existence in the universe. Astronomers and scientists, alike, believe that intermediate-mass black holes can form from three separate scenarios: A.) They are primordial black holes that formed from materials in the early cosmos, B.) They possibly formed in regions of space that contained a high-density of stars, or C.) They developed from the merger of two smaller black holes (stellar-mass) that collided with one another. For these reasons, intermediate-mass black holes are believed to exist at the center of globular clusters in the galaxy.


Supermassive black holes, as the name implies, are the largest forms of black holes in the universe, and often contain masses that are millions (and sometimes billions) of times larger than our own Sun. Currently, it is believed that supermassive black holes are at the center of almost every observable galaxy in the universe. Unlike stellar-mass black holes that form from the collapse of massive stars, it remains a mystery how supermassive black holes form. Powerful quasars, however, may hold the answer to their formation.

Black holes are believed to be at the center of most galaxies in the universe.
Black holes are believed to be at the center of most galaxies in the universe. | Source


In 1974, Stephen Hawking revolutionized the study of black holes with his theory known as “Hawking Radiation.” In this theory, Hawking proposed that black holes were not entirely black, and argued that the holes “emit small amounts of thermal radiation” (Wikipedia.org). The theory was revolutionary in that Hawking’s analysis demonstrates that black holes are capable of shrinking and evaporating over time “as they lose mass by the emission of photons and other particles” (Wikipedia.org). Although the evaporation rate of supermassive black holes is incredibly long (approximately 2x10100 years for an average-sized supermassive black hole), the theory demonstrates that black holes are like the rest of the universe in that they are also in a state of decay.


Scientists have been unable to observe black holes with telescopes that detect forms of electromagnetic radiation. However, their presence has been inferred through the observation of their effect on matter within their general vicinities. For example, when distant objects are seen orbiting around seemingly invisible objects, or when objects move erratically, astronomers believe that black holes are likely to blame.

Black holes are sometimes more obvious, however, as their consumption of surrounding stars sometimes superheats gas and dust that surround the black hole, causing it to emit visible radiation. Occasionally, this radiation “envelops the black hole in a whirling region called an accretion disk” (nationalgeographic.com), making it partially visible to observers on Earth. Similarly, black holes can even eject stardust, giving a comparable radiation effect on the dust particles that are exiting.

Direct photos of black holes were largely considered impossible until earlier this year, when the “Event Horizon Telescope” (EHT), which consists of a large network of radio telescopes operating in unison, were able to construct the first image of a black hole at the center of Messier 87. Using complex algorithms and image reconstruction (known as CLEAN), astronomers have now developed a means for using radio frequencies (radio astronomy) to provide images of our distant neighbors.

Up-close image of black hole at Messier 87. First photo of black hole ever taken.
Up-close image of black hole at Messier 87. First photo of black hole ever taken. | Source

What Happens To Objects That Fall Into Black Holes?

What happens to objects that fall into black holes? Although little is known about what transpires inside a black hole, scientists and astronomers believe that subjects that pass the hole’s event horizon are subjected to tremendous tidal stress. The object (or individual) would quickly find itself stretched and squeezed in all directions, before finally being torn completely apart. These tidal forces are the same phenomenon “responsible for ocean tides on Earth,” in relation to the Moon’s gravitational pull (Chaisson and McMillan, 599). The difference between a black hole and Earth’s tidal forces is that the black hole’s are incredibly stronger, and remain the strongest force known to exist within the universe at this time.

In addition to being stretched in all directions, matter entering the black hole is also squeezed and “accelerated to high speeds” (Chaisson and McMillan, 600). With countless objects being stretched, torn apart, and accelerated, violent collisions are believed to also occur between these particles, creating frictional heating. This, in turn, causes the matter to emit radiation as it plunges into the black hole through the form of x-rays. For this reason, some scientists believe that the region surrounding a black hole may be a potential source of energy.

Is Time Travel Possible Inside a Black Hole?

One popular element of science fiction and popular culture is the notion that black holes may hold the power for individuals to travel in time. Assuming an individual could pass beyond the event horizon of a black hole without being torn apart, and assuming that an object/individual could exit the black hole at their own choosing (which remains theoretically impossible at the present time), scholars believe that time travel is, indeed, possible with black holes. Due to the tremendous gravitational pull of a black hole, scientists believe that time slows down for objects approaching its event horizon. Clocks onboard a spacecraft entering a black hole would show “time dilation” in relation to clocks operating outside of the event horizon. As a result, scientists believe that once the spacecraft exited the black hole, it would appear days (even years) into the future, depending on how long it remained inside.

For the outside observer witnessing the spacecraft’s approach toward the event horizon, the journey would appear to take forever. For the space-crew onboard, however, scientists believe that time would appear completely normal; thus, making time travel into the future a real possibility.

Black Hole at Messier 87, zoomed out. Notice the tiny black dot at its center.
Black Hole at Messier 87, zoomed out. Notice the tiny black dot at its center. | Source

Black Holes in Popular Culture

Black holes continue to play a prominent role in Hollywood and pop culture, alike. Although human understanding of black holes continues to remain miniscule, the human imagination (particularly in science fiction) has proven quite wild in more recent years with the portrayal of these deep-space objects. Here is a list of popular movies with references to black holes:

  • Supernova
  • Star Trek
  • The Black Hole
  • Event Horizon
  • Interstellar

“Black holes are where God divided by zero.”

— Albert Einstein

Quotes About Black Holes

Quote #1: “Black holes are where God divided by zero.” – Albert Einstein

Quote #2: “The black holes of nature are the most perfect macroscopic objects there are in the universe. The only elements in their construction are our concepts of space and time.”

Quote #3: “The black hole teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but.” – John Wheeler

Quote #4: “Black holes are the seductive dragons of the universe, outwardly quiescent yet violent at the heart, uncanny, hostile, primeval, emitting a negative radiance that draws all toward them, gobbling up all who come too close. These strange galactic monsters, for whom creation is destruction, death life, chaos order.” – Robert Coover

Quote #5: “Consideration of particle emission from black holes would seem to suggest that God not only plays dice, but also sometimes throws them where they cannot be seen.” – Stephen Hawking

Quote #6: “We have this interesting problem with black holes. What is a black hole? It is a region of space where you have mass that’s confined to zero volume, which means that the density is infinitely large, which means we have no way of describing, really, what a black hole is!” – Andrea M. Ghez

Quote #7: “Do you realize that if you fall into a black hole, you will see the entire future of the Universe unfold in front of you in a matter of moments and you will emerge into another space-time created by the singularity of the black hole you just fell into?” – Neil deGrasse Tyson

Quote #8: “If you want to see a black hole tonight, tonight just look in the direction of Sagittarius, the constellation. That’s the center of the Milky Way Galaxy and there’s a raging black hole at the very center of that constellation that holds the galaxy together.” -- Michio Kaku

Quote #9: “Black holes provide theoreticians with an important theoretical laboratory to test ideas. Conditions within a black hole are so extreme, that by analyzing aspects of black holes we see space and time in an exotic environment, one that has shed important, and sometimes perplexing, new light on their fundamental nature.” – Brian Greene

Quote #10: “Data suggest that central black holes might play an important role in adjusting how many stars form in the galaxies they inhabit. For one thing, the energy produced when matter falls into the black hole may heat up the surrounding gas at the center of the galaxy, thus preventing cooling and halting star formation.” – Priyamvada Natarajan


Do you believe that black holes will make the prospect of time travel a reality in the future?

See results


In closing, black holes continue to be one of the most fascinating (and strangest) objects to inhabit our vast universe at large. Although information about their existence and internal structure continues to be limited for the time being, it will be interesting to see what new forms of information can be gleaned about these fascinating deep-space objects in the near future. What can black holes tell us about our universe? How did they form? Finally, and perhaps most importantly, what can they us about the formation of our universe and the early cosmos? Only time will tell.

Works Cited:

Chaisson, Eric and Steve McMillan. Astronomy Today, 6th Edition. New York, New York: Pearson, Addison Wesley, 2008.

NASA. Accessed May 04, 2019. https://science.nasa.gov/astrophysics/focus-areas/black-holes.

Wei-Haas, Maya. "Black Holes, Explained." What Is a Black Hole? December 17, 2018. Accessed May 04, 2019. https://www.nationalgeographic.com/science/space/universe/black-holes/.

Wikipedia contributors, "Black hole," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Black_hole&oldid=895496846 (accessed May 4, 2019).

Wikipedia contributors, "Event Horizon Telescope," Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Event_Horizon_Telescope&oldid=895391386 (accessed May 4, 2019).

Questions & Answers

    © 2019 Larry Slawson


      0 of 8192 characters used
      Post Comment
      • Miebakagh57 profile image

        Miebakagh Fiberesima 

        12 months ago from Port Harcourt, Rivers State, NIGERIA.

        Well noted.

      • Larry Slawson profile imageAUTHOR

        Larry Slawson 

        12 months ago from North Carolina

        Thank you Paula! I'm so glad you enjoyed it. And I completely agree with you, 100 percent! Haha.

      • fpherj48 profile image


        12 months ago from UpstateWestern,New York

        Larry...another great article. And for me, quite educational, which I love! I am a seeker of knowledge too! "Learning" is my avocation! I firmly believe we must NEVER stop yearning to learn more!

        I enjoyed this tutorial immensely!

      • Larry Slawson profile imageAUTHOR

        Larry Slawson 

        12 months ago from North Carolina

        Thank you everyone! @Marie, I totally and completely agree. I thought it was a nice quote as well :)

        @Pamela I'm so glad you enjoyed :) Black holes are such weird objects in space. Its interesting that we still don't fully understand what they are.

        @Miebakagh I'm glad you enjoyed :)

      • Marie Flint profile image

        Marie Flint 

        13 months ago from Tawas City, Michigan USA

        Good job. Quote #7 comes closest from a spiritual channeled message (Kryon/Carroll) I rather liked. Essentially it stated that black holes were portals to other dimensions.

      • Miebakagh57 profile image

        Miebakagh Fiberesima 

        13 months ago from Port Harcourt, Rivers State, NIGERIA.

        Hello, Pamela, you are welcomed. The solar system or milky way is still a mystery and a puzzle world. But men and scientists are here to demystify all as time goes on. on. It is a step by step processes. Your comment is useful to me and the others. Many thanks, and happy Sunday!

      • Pamela99 profile image

        Pamela Oglesby 

        13 months ago from Sunny Florida

        This is an awesome article about something i have always wanted to understand. I didn't know there were so many types of black holes. I saw a picture taken recently of a black hole that was very colorful, like some you displayed. I always thought a black hole was black. Your explanation for black holes was very good.

      • Miebakagh57 profile image

        Miebakagh Fiberesima 

        13 months ago from Port Harcourt, Rivers State, NIGERIA.

        Hey, Larry, I think this also explains why stars do not die when falling down to earth as brilliant ash dust. Though they subsequently ascend higher into the universe, perhaps. Do some fall into the black hole?

      • Larry Slawson profile imageAUTHOR

        Larry Slawson 

        13 months ago from North Carolina

        Thank you Liz! I'm glad you enjoyed :)

      • Eurofile profile image

        Liz Westwood 

        13 months ago from UK

        This is an interesting and well-structured article. I had heard of Stephen Hawking's work on black holes. You give a good explanation of black holes.


      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, owlcation.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://maven.io/company/pages/privacy

      Show Details
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
      ClickscoThis is a data management platform studying reader behavior (Privacy Policy)