Astro 101: Your 5 biggest questions about black holes answered

    New online course by University of Alberta explores the universe’s most captivating phenomenon.

    By Andrew Lyle on November 9, 2018


    Astro 101, a new online course by the University of Alberta, is educating students and the public on black holes—and busting some of the biggest myths orbiting these captivating subjects.

    Headed by Sharon Morsink, associate professor in the Department of Physics and director of the University of Alberta Astronomical Observatory, the online course dives into the science behind black holes with educational animations and video.

    “Black holes are a fun way to educate people on the concepts of physics and astronomy,” said Morsink. “Whenever I talk to people about astronomy, they almost always ask questions about black holes,” said Morsink. “Studying them draws on a lot of areas, so a course that is centred on black holes can be used as a way to learn many fundamental physics concepts.”

    Astro 101 is the one of the latest massive open online courses, or MOOCs, from the University of Alberta. Designed to be accessible for those without a physics background, the course is free for the public or can be taken as a credit course by UAlberta students.

    With that in mind, we answer five of the top questions about black holes and the science behind them, courtesy of Morsink and Astro 101:


    1. How dangerous are black holes?

    It turns out that in astronomical terms, black holes really aren’t much more dangerous than other stellar bodies.

    “People often think that black holes are incredibly dangerous vacuum cleaners that pull in material from all around,” said Morsink. “But really, a black hole is no more dangerous than the sun.

    “If you aim a rocket towards a black hole, it will be trapped by the black hole. But if you aim a rocket in the same way at a star like the sun, the rocket will burn up in the star. While you don’t want to get too close, in both cases you can safely orbit around them instead of falling in or crashing.”

    2. Do black holes work for time travel?

    You may have guessed the answer to this one: no. Most black holes in movies and popular culture are pure science fiction. Time travel? Escaping a black hole? Not so likely.

    “The 2009 reboot of Star Trek has lots of weird stuff that they made up about black holes,” said Morsink. “They invented something called ‘red matter’ that creates black holes. They fly the Enterprise into a black hole, which then acts as a time machine. None of which makes any sense.”

    However, that doesn’t mean Hollywood never gets it right.

    “The movie Interstellar did a great job with the science and the visualizations of the region outside of a black hole,” said Morsink. “But they engaged in a lot of speculation about what happens inside—because we don't really know what happens there.”

    A composite view of spiral galaxy M106—with a black hole at the centre

    At the centre of spiral galaxy M106 lurks a giant black hole. This image displays the galaxy as a composite of X-ray, optical, infrared, and radio images. Image credit: NASA

    3. What’s the biggest mystery surrounding black holes?

    What happens inside a black hole remains one of the biggest mysteries facing scientists. One of the big puzzles about black holes that still hasn’t been answered is the “black hole information paradox.”

    “The basic idea is that we don't know what happens to information when it enters a black hole,” explained Morsink. “If you throw a one kilogram jar of peanut butter or a one kilogram weight from the gym into a black hole, the black hole's mass increases the same amount, but afterward there’s no way to tell the difference between the stuff that went in. This is still an open problem down to the smallest quantum scales.”

    4. If we can’t see black holes, how do we know where they are?

    Black holes absorb all light and information—so how do scientists know where they are and observe them? The answer has to do with objects near black holes that emit light.

    “The light from gas or stars orbiting black holes gives away their presence, as the light is affected by nearby black holes,” said Morsink. “More recently, it has been possible to detect something called gravitational radiation that is emitted when black holes merge. But that's a topic for the most advanced chapter of the course.”

    5. What do black holes and vampires have in common?

    Admittedly, this might not have been your most pressing question about black holes. But “stellar vampires” are real—though despite their name, the physics concept doesn’t mean space is home to bloodsucking undead.

    Craig Heinke, professor in the Department of Physics, is one of several guest experts featured in Astro 101’s collection of videos. He explains the fanciful—and apt—name.

    “A stellar vampire is a star that is dead but still sucking the mass away from another star,” said Heinke. “Those dead stars, such as black holes or neutron stars, can act as stellar vampires when they end up nearby another lower-mass star, tearing material off the edge of the other star and absorbing it.”


    Interested in learning more about black holes and space? You don’t need a physics background to start learning.

    “Astro 101 is very introductory and doesn't assume much in the way of prior physics or mathematics knowledge,” said Morsink. “The content has been put together into some very engaging videos. The writing team put a lot of effort into finding fun analogies and explanations.”

    The University of Alberta offers a number of massive open online courses (MOOCs), including Astro 101, four paleontology courses, and several courses in other disciplines, including computing science.

    These engaging online courses are open to the public, and some may be taken for credit by University of Alberta students. Learn more or register for Astro 101 today.