ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

How Dangerous Are Near-Earth Objects?

Updated on January 16, 2015
jjheathcoat profile image

J.J. is a freelance researcher, writer, and editor. She loves science, history, and "weirdness". Oh, and gaming. Lots of gaming.

Comet C/2014 Q2 (Lovejoy) is making a big show this month as it nears its perihelion on January 30th. The comet only comes around once every 11000 years. It's also one of the closest comets to come near Earth.
Comet C/2014 Q2 (Lovejoy) is making a big show this month as it nears its perihelion on January 30th. The comet only comes around once every 11000 years. It's also one of the closest comets to come near Earth. | Source

Last year, NASA'S Near-Earth Object Wide-field Survey Explorer (thankfully shortened to NEOWISE) cataloged 245 new near-earth objects, as well as characterized 40 objects we were previously aware of. Eight were classified as PHA's, or "potentially hazardous asteroids". That brings the total PHO count in our solar system to over 1500.

Naturally, such news is often the source for many panicked rantings and inflammatory articles. After all, we know for a fact that devastating impacts have occurred before, and are likely to come again. NASA and other space science groups have dedicated resources to studying these objects for a reason. Last year's Rosetta Philae comet landing was a huge step in our adventure to potentially protect our planet from future hazards.

So, which objects are most likely to come hair-raisingly close to our big blue marble? First, let's take a look at how we measure the risks that NEOs bring along.

Terminology

Perihelion - The point where an object's orbit is closest to the sun. Planets, asteroids, and comets all have their own perihelion.

Near-Earth Object (NEO) - An orbiting object whose perihelion falls under 1.3 AU (120,842,549 miles).

Absolute magnitude - The measurement of how bright an object would appear if it were 10 parsecs (32.6 light years) from the observer. Scientists use this measurement to determine how large a NEO is. This measurement is usually shortened to the letter "H".

Potentially Hazardous Object (PHO) - A NEO with an absolute magnitude about 22.0H or less that will come within 0.05 AU (4,647,790 miles) of Earth. Large objects that come within this distance have the potential to hit Earth and cause serious damage.

How do we know a NEO is dangerous?

A NEO's destructive capability is measured by the "impact hazard" of the potential collision event. This measurement is obtained by using equations measuring size and kinetic energy to narrow down an object's expected energy at impact. There are two different scales used to depict impact hazard.

Palermo Scale

The Palermo Technical Impact Hazard Scale is a complex set of equations and perimeters used to assess potentially hazardous objects in detail. The Palermo scale measures a NEO against the "background hazard" of objects of a similar size or larger to determine if that object has more or less potential risk. These values are expressed in positive or negative numbers. For example, a NEO ranked at 0 has the same hazard valuation of objects of the same background hazard. Objects at +2 are 100 times more hazardous, while those at -2 are 100 times less hazardous. Anything between -2 and 0 is still monitored carefully, but objects over 0 are considered the most dangerous.

Torino Scale

The second scale, known as the Torino Impact Hazard Scale, uses a simple 0 to 10 integer scale to assess the probability an object could hit Earth given its known kinetic energy, plus the damage it could cause. Something at level 0 has very little chance to hit, and the damage associated with it would be negligible. In contrast, an object that ranks level 10 on the Torino scale has almost 100% chance to hit, and the damage caused could destroy life as we know it. Because it is easier to understand than the Palermo scale, the Torino is the scale typically used outside of the scientific community.

Below is a handy table showing the scales in action.

Earth Impact Risk Examples

(click column header to sort results)
Object Name  
Palermo Scale  
Torino Scale  
Impact Risk  
2014 WF6 (asteroid)
-3.90
0
Virtually None
(29075) 1950 DA (asteroid)
-0.81
Not Defined
1 in 20,000
(415029) 2011 UL21 (asteroid)
-0.90 (in Oct 2011)
1
1 in 70 million
A chunk of the famous Chelyabinsk meteor. Thousands of people were injured after it exploded in the sky.
A chunk of the famous Chelyabinsk meteor. Thousands of people were injured after it exploded in the sky. | Source
4179 Toutatis came within 0.05 AU to Earth in 2012. The next time it will be that close will be 2069.
4179 Toutatis came within 0.05 AU to Earth in 2012. The next time it will be that close will be 2069. | Source

How often do NEOs actually hit Earth?

Small scale objects fall to Earth almost every day in the form of small meteorites. Slightly larger objects may hit once every year or so. Very large objects, such as the one that exploded over Chelyabinsk in 2013, come every 100 years. As you can see, larger objects come less frequently than the smaller ones. A truly devastating impact (Torino scale 9 or higher) only occurs every 10,000 to 100,000 years.

Why is that so? Well, the majority of NEO's in our galactic neighborhood are tiny to begin with. It's reasonable to expect that the smaller bodies hit more often because there are more of them out there. Larger objects also tend to have much longer orbits, or they originate at such great distances that it would take over 100 years for them to be considered a threat.

Because most of our calculations depend on the potential for impact within 100 years, many of the larger magnitude objects aren't considered immediate hazards.

Panoramic view of the Barringer Crater in Arizona.  The crater was created nearly 50,000 years ago by a heavy nickle-iron meteorite over 50 meters across.
Panoramic view of the Barringer Crater in Arizona. The crater was created nearly 50,000 years ago by a heavy nickle-iron meteorite over 50 meters across. | Source

Which PHOs are currently considered the most dangerous?

To date, the PHO with the highest probability of hitting Earth is the asteroid 1950 DA. It has a Palermo Scale value around -0.81, making it the highest-ranked object discovered so far. Scientists at NASA's NEO program originally placed 1950 DA at a 1 in 300 probability of impact. That value was significantly lowered to 1 in 20,000. Still, that's a much higher risk probability than most PHOs.

Here's the catch: 1950 DA isn't scheduled for its potentially dangerous rendezvous until 2880. That 800 year wait gives us a lot of time to recalculate its real potential and prepare some manner to deflect it if need be.

Does this mean we won't see a devastating impact in our lifetime?

Not necessarily. New PHO's are being discovered all the time. As our technology continues to advance, so too will our ability to see the potential threats to our planet. That doesn't mean we'll be able to do much about it if "the big one" comes within the next 50 years or so. Unlike the dinosaurs before us, we'll probably see our imminent doom coming.

And that is probably the key to understanding what all the paranoia is about when it comes to NEOs and PHOs. Our exploration of the cosmos has further enriched our understanding of the universe, and how fragile our planet is in the grand scheme of things.

Whether the thought scares you, or fills your mind with a sense of awe and wonder, it's hard to ignore how truly magnificent it is to be conscious of our temporary place in space.

Comments

    0 of 8192 characters used
    Post Comment

    No comments yet.

    working

    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, hubpages.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://hubpages.com/privacy-policy#gdpr

    Show Details
    Necessary
    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)
    Features
    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)
    Marketing
    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.
    Statistics
    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)