The lovely Perseids’ comet could end life on Earth

The Swift-Tuttle comet is the source of the lovely Perseid meteor shower each August. It’s also getting closer and closer, making it "the single most dangerous object known to humanity."

The Perseids are arguably the most famous annual meteor shower. Silently streaking across the mid-August heavens each summer, it's a profound and beautiful event for anyone with a dark sky and the discipline to just. Keep. Looking. Up. The often-exquisite shooting stars come from a comet that's drawing ever closer to Earth. Dangerously close, actually: Radio astronomer Gerrit Verschuur has called Comet 109P/Swift-Tuttle "the single most dangerous object known to humanity." Apparently, our inspiring, transcendent meteor shower may also be the harbinger of humanity's doom, give or take a few thousand years.



Perseids, 2013 (Credit: Flicker user the very honest man)

Why Swift-Tuttle is such a threat

Swift-Tuttle passes through our solar system at a steep angle compared to the solar system's planets every 133 years. It swings around the sun, and as it does, melts slightly, casting off a massive debris field of ice and rock that's estimated to grow as wide as 10 million miles and with a length of more than 75 million miles. This stuff is what rains down on us at an average of 37 miles per hour each August as what astronomers call “fireballs." NASA's Paul Chodas says, “The debris is coming in faster than many other comets because it's a very elongated orbit … so that makes the show a little more spectacular because of the speed."


Swift-Tuttle orbit (Credit: NASA/JPL)

What concerns scientists about Swift-Tuttle is that each time it passes Earth, it's slightly closer. There's not much change year to year, but over time it adds up. In 1992, it was 110 million miles away, but in 2126 it will be a mere fraction of that: 14.2 million miles. In 3044, it will be less than a million, a frighteningly small distance in galactic terms. Current calculations have us as probably safe until 4479, though each time Swift-Tuttle sheds materials near the sun, the comet gets just a bit smaller, and it's possible that planetary gravitational effects will eventually alter its orbit.


Swift-Tuttle in 1992 (Credit: NASA)

And Swift-Tuttle is big, with a nucleus of 16 miles (26 km) across. It's more than twice the size of the Chicxulub impactor, the asteroid believed to have wiped out the dinosaurs. The energy it releases could be 27 times greater than that extinction event. Astrophysicist and author Ethan Siegel writes in Forbes that a collision with Swift-Tuttle would "release more than one billion megatons of energy: the energy equivalent of 20,000,000 hydrogen bombs exploding all at once."


NASA visualization of Chicxulub impact.

History of Swift-Tuttle

Reports of visits by Swift-Tuttle go all the way back to 69 B.C, though Swift-Tuttle was officially discovered and named in 1862 by American astronomers Lewis Swift and Horace Tuttle, who both discovered it independently. The “P" in “109P" refers to it being a periodic comet. Giovanni Schiaparelli realized in 1865 that it was the source of the Perseid meteor shower.

How to watch the Perseids

The Perseids this year can be seen from August 9 through the 14th and are expected to be even more impressive—200 fireballs an hour—than usual, thanks to the pull of Jupiter. On the other hand, lunar light will get in the way early on the night of peak visibility August 11-12 as the moon is 63% illuminated in its waxing gibbous phase. Waiting until the moon sets and the constellation Perseus rises around 1 am, however, still provides a 3.5-hour optimal viewing window between 1 am and 4:20 am.

NASA's Bill Cooke shared the best advice for catching the Perseids or any meteor shower this or any year with Space.com.

"Meteor-shower observing requires nothing but your eyes; you want to take in as much sky as possible. Go outside in a nice, dark sky, away from city lights, lie flat on your back and look straight up. [Take] your choice of beverage and snacks and things like that."

You should plan to spend at least a few hours skywatching — your eyes won't even fully adapt to the darkness for about 30 minutes. As Space.com puts it, “most showers only reveal their splendor in time." And Cooke points out, “You can't observe a meteor shower by sticking your head out the door and looking for five minutes."

Stand up against religious discrimination – even if it’s not your religion

As religious diversity increases in the United States, we must learn to channel religious identity into interfaith cooperation.

Sponsored by Charles Koch Foundation
  • Religious diversity is the norm in American life, and that diversity is only increasing, says Eboo Patel.
  • Using the most painful moment of his life as a lesson, Eboo Patel explains why it's crucial to be positive and proactive about engaging religious identity towards interfaith cooperation.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less

Moon landing astronauts reveal they possibly infected Earth with space germs

Two Apollo 11 astronauts question NASA's planetary safety procedures.

Credit: Bettmann, Getty Images.
Surprising Science
  • Buzz Aldrin and Michael Collins revealed that there were deficiencies in NASA's safety procedures following the Apollo 11 mission.
  • Moon landing astronauts were quarantined for 21 days.
  • Earth could be contaminated with lunar bacteria.
Keep reading Show less

NASA's idea for making food from thin air just became a reality — it could feed billions

Here's why you might eat greenhouse gases in the future.

Jordane Mathieu on Unsplash
Technology & Innovation
  • The company's protein powder, "Solein," is similar in form and taste to wheat flour.
  • Based on a concept developed by NASA, the product has wide potential as a carbon-neutral source of protein.
  • The man-made "meat" industry just got even more interesting.
Keep reading Show less

Where the evidence of fake news is really hiding

When it comes to sniffing out whether a source is credible or not, even journalists can sometimes take the wrong approach.

Sponsored by Charles Koch Foundation
  • We all think that we're competent consumers of news media, but the research shows that even journalists struggle with identifying fact from fiction.
  • When judging whether a piece of media is true or not, most of us focus too much on the source itself. Knowledge has a context, and it's important to look at that context when trying to validate a source.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less