As it makes it trip toward Earth will Apophis get too close for comfort? Photo source: Sky and Telescope
On Friday, April 13th, 2029 we will see the amazing asteroid Apophis as it careens past us, between the Earth and the Sun, on its journey through the cosmos.
WHAT IS AN ASTEROID ANYWAY?
Let’s start the with basics. Asteroids are basically rocks, varying in size, but smaller than planets that float around in space and orbit the Sun just as Earth does.They go by many names, the largest of them are called planetoids, minor planets, or dwarf planets, some are simply referred to as space debris. The most massive asteroid discovered to date is Ceres, which is 590 miles wide (about the size of Texas). Much of this debris orbits relatively near Earth. The asteroid belt is located between Mars and Jupiter, the belt alone has been estimated to contains some 750,000 asteroids.
To really grasp the enormity of just how many space rocks that are in our solar system please take a moments to view to the video below. It illustrates just how many asteroids were discovered between 1980 and 2012. It is utterly impressive!
DOES THE NAME APOPHIS RING A BELL?
There are millions of asteroids in our solar system, but not all of them get a name as ominous as Apophis. The name refers to an evil Egyptian serpent God that represents chaos and darkness in ancient Greek mythology, basically Apophis was the Greek’s version of Satan. So what is about Apophis the asteroid conjures up so much terror?
Knowing how much space debris is out there, what sets Apophis apart form other asteroid: in two words, orbit and size. It’s true that Apophis isn’t the largest asteroid discovered, however, it will be the largest asteroid to orbit so close to Earth in all of human experience, it will come closer than the moon even!
In 2004, when it was discovered, it gave the scientific community quite a scare, which is exactly why it was given the devilish name. At that time, the exact location of its orbit was unclear; scientist were able to calculate that Apophis is going to be making an extremely close approach to Earth on April 13th, 2029, which in that year will be a Friday!
In 2007, NASA concluded an evaluation of the asteroid and the impact that the rock and Earth will have on each other. They state, “The future for Apophis in 2029 includes an approach to Earth…appearing to the naked eye as a moderately bright point of light moving rapidly across the sky”. It will get so close to Earth that it will actually dip below the orbit of our GPS satellites and it will be visible without the use of telescope in the daytime sky. Current estimates put its flyby at distances of only 19,000-22,000 miles from Earth (as a reference, the moon is 238,000 miles away).
This is great news for us, because during the initial uncertainty in 2004, the chance of it hitting Earth was 2.7% (that’s almost 3 in 100), at the peak of the fervor estimates got as large as almost 1 in 37 chances of impact. Which is undoubtedly quite terrifying.
Since then, different groups of scientists, including those at NASA’s Jet Propulsion Laboratory and the European Space Agency, have devoted their lives to studying and understanding Apophis’ size and path through space. It has been ten years since its discovery and the threat of impact has since been downgraded dramatically. Depending on how you calculate it, the odds of impact are now thought to be 1 in a million, luckily the odds are in our favor!
DON’T BE FOOLED, SIZE MATTERS
Apophis orbits the Sun every 324 days and it flies by Earth every 7 years. Knowing the exact orbit of the asteroid is crucial because Earth won’t be getting just one close brush with the asteroid in 2029, there will be an additional near Earth orbit April 13, 2036, seven years later.
Currently it is about nine-million miles away from Earth which makes it perfect for observation.The most recent research, reported in January 2014, suggest that the astroid is 1,066 feet in width (with a margin of error of +/- 49 feet). The calculations were performed by a team from Max Planck Institute for Extraterrestrial Physics in Garching, Germany. They have determined that the size of Apophis is 20% larger than once thought.
Why does that matter? Well, because an increase in width equals an increase in mass and volume, in this case the mass has been increased by 75%, which is definitely substantial. The size of an asteroid plays a major role in how it orbits through space; the more observation that is done on Apophis, the easier it will be to calculate the exact mass and trajectory of the object.
In a quote taken from NASA.gov from their analysis of the asteroid in the article Predicting Apophis’ Earth Encounters in 2029 and 2036,they speak of other factors that can alter the path of the asteroid as it sails through space toward Earth:
“Trajectory predictions for asteroids are normally based on a standard model of the solar system that includes the gravity of the Sun, Moon, other planets, and the three largest asteroids.However, additional factors can influence the predicted motion in ways that depend on rarely known details, such as the spin of the asteroid, its mass, the way it reflects and absorbs sun-light…and the gravitational pull of other asteroids passing nearby.”
The data announced in January, 2014, explains how new radar detections have calculated, not only the new size of the asteroid but also the amount of sunlight it is absorbing. The light it absorbs translates to heat. While it rotates during its orbit, the side facing the sun obviously absorbs more of this heat that the side facing away. Over a long enough period of time this constant heating and cooling can change the trajectory of the object.
What is crucial to note, is that the trajectory of the asteroid as it passes our planet in ’29 will determine whether or not it crash into Earth in ’36 as it makes another close encounter. What is known as the keyhole will play a critical role in the course of Apophis and Earth’s future, as well.
A NEAR MISS: THE GRAVITATIONAL KEYHOLE
The picture to the left illustrates the orbit of satellites around Earth; it also shows Apophis’ orbit if it were to pass through the keyhole. The gravitational keyhole refers to a section of space about a half a mile wide (the bean shaped outline), it it only slightly larger than the asteroid itself. This bit of space is significant because if entered into, Earth’s gravitational pull will change the orbit of the asteroid.
If Apophis were to pass anywhere within the gravitational keyhole, as it flies by us on April 13, 2029, an impact in 2036 will become inevitable. Before you start hoarding canned food and building asteroid shelters let me just reiterate that the odds of this happening are extremely slim.
The asteroid that took out the dinosaurs was six miles wide, Apophis pales in comparison at just above 1000 feet (.2 miles) wide, but that doesn’t mean that the impact wouldn’t cause damage. Since the Earth is primarily water the chances of it hitting an ocean are high. This would cause tsunami waves five stories tall. There would be earth quakes and volcanic eruptions, and if it where to hit land it would undoubtibly modify Earth’s crust.
Luckily, scientists are fairly sure that Apophis will not hit Earth on either of its close orbits, there is a 1 in almost 7 million chance of it entering the keyhole, thus hitting us in ’36. The tricky part is that the keyhole is hard to calculate because we still don’t have all of the critical information necessary to do so. And it won’t be until after the 2029 pass that scientist will know for sure if it passed through the keyhole. The most current calculations suggest that Apophis will pass by Earth in 2036 at 150 lunar distances, much farther away than its orbit in 2029.
References
- Discovery News, Asteroid Apophis Just Got Supersized, Ian O’Neill, Jan.9,2013.
- NASA.gov, Predicting Apophis’ Earth Encounters in 2029 and 2036
- Universe Today, How Many Asteroids Are Out There, Jason Major, Sept.25,2012.
- Space.com, Whew! Huge Asteroid Apophis Won’t Hit Earth in 2036,Tariq Malik, Jan.10,2013.
- Universe Today, Apophis’ Odds of Earth Impact Downgraded, Nancy Atkinson, Oct.7, 2009.
- Livescience.com, What Are an Asteroid, a Meteor and a Meteorite? Marc Lallanilla, Feb.15,2013.
Shout Out Science! 