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NASA scientists have recalculated the path of the large asteroid Apophis, significantly downgrading the odds of it hitting Earth. Using new information, the refined path indicates a 1 in 250,000 chance of impact in 2036, reduced from the 1 in 45,000 odds calculated earlier. The asteroid is expected to make a record-setting — but harmless — close approach to Earth on Friday, April 13, 2029, when it comes no closer than 18,300 miles above Earth's surface.
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On Friday April 13th, 2029 the asteroid Apophis will make its closest approach to Earth ever! There is no reason to be alarmed, though. NASA has ruled out the chance for an Earth impact. The biggest unknown about this asteroid passing is whether or not it will hit a gravitational keyhole and have its trajectory changed enough to causes an impact when it passes again in 2036.

To explain what could happen on April 13th, 2029, it would probably help if you were given an idea as to what a gravitational keyhole is. A gravitational keyhole is a region of an orbit where a small gravitational input could cause a small body to collide with the large body it is orbiting. With the asteroid Apophis the chance of a trajectory change after hitting such a keyhole would effect its passing of the Earth in 2036. The asteroids trajectory could be changed by as much as 28°. Scientists can not predict if it will be drawn towards the Earth or away. They can not tell if the change will cause it to hit Earth or another solar system body at an earlier point in its new orbital path.

The Earth is impacted by small asteroids and meteorites on a monthly basis. All of them are small enough to burn up in the atmosphere, leaving a nice light show as the only evidence of their passing. On April 13th, 2029 things could be a little different. This asteroid is 320 m wide. That is enough to destroy an area the size of the Quebec province if it hit land or to cause horrific tsunamis if it hit an ocean. A little chilling for an asteroid that was predicted to have a one in sixty chance of hitting the Earth.

The asteroid Apophis will add to the list of creepy things that have happened on Friday the 13th when it passes on April 13th, 2029. For once, something pleasant will happen: the Earth will be safe from an asteroid impact. The day will go unnoticed for all of those people who are not familiar with astronomy, but astronomers will hold their breath until they are able to plot a new orbit for this asteroid.

NASA has a nice article on the asteroid Apophis. Find out more on gravitational keyholes here. On Universe Today we have a good article on the April 13th, 2029 asteroid and another on the 2029 asteroid. Astronomy Cast has a nice episode on death from the skies.

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Apophis 2036 has caused quite a stir in the astronomy community. It might be better to give you a little history of the asteroid Apophis first so that you have as much information as possible. In 2004 the asteroid Apophis was given as 2.7% chance of impacting the Earth. That in and of itself is not a major concern, but the size of Apophis, 270 m and a mass of 2.1 x 10¹⁰ kg, caused concern for everyone involved with the asteroid. Even a small chance of an asteroid that size impacting the Earth is a reason to study the living daylights out of an it. It was eventually found to be of no threat in 2004 or its next pass in 2029, but what about the pass in 2036?

Apophis 2036 is still something that scientists are a little nervous about because of the chance it may hit a gravitational keyhole in 2029. The gravitational keyhole, which is generated by the Earth, could effect the trajectory and orbit of Apophis enough to make the pass in 2036 actually closer to Earth and put it on a definite impact course with the planet. Many scientists downplay the possibility, but the chances are real. This asteroid will return every seven years until it hits something in space.

The threat from Apophis 2036 is real enough that some scientists have proposed that it be nudged out of its present orbit so that it will miss the keyhole. According to NASA scientist David Morrison" after 2029, the deflection would have to be vigorous enough to miss not just a tiny keyhole but the much larger target of the Earth itself and such a deflection is far beyond present technology for an asteroid this large."

Apophis 2036 is shaping up to be a pivotal stressor on the ability of NASA and the astronomy community to protect the Earth from impending impact. Will science be able to prevent the possible deaths of hundreds of thousands of people and the devastation that a large impactor would create? I guess we will have to wait and see.

Wikipedia offers a nice article on gravitational keyholes and NASA shows some news about a possible impact on their website. Here on Universe Today there is a great article on the asteroid Apophis as well as a description of exactly how big Apophis 2036 is.

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Radar observations taken at the Arecibo Observatory in Puerto Rico on January 27, 29, and 30, 2005 have significantly improved our estimate for the orbit of asteroid 2004 mn4 and changed the circumstances of the Earth's close approach in 2029. On April 13, 2029, the predicted trajectory now passes within 5.7 Earth radii, 36,350 km, of the Earth's center. That is just below the altitude of geosynchronous Earth satellites; however, an Earth collision in 2029 is still ruled out.

The asteroid 2004 mn4 is also called Apophis. With a size of 320 m and a mass of 2.1 x 10¹⁰ kg, Apophis could have lived up to its Egyptian name for Uncreator. It is thought that a strike by an object that size could destroy 10% to 25% of the life on Earth. Apophis's orbit will take it past the Earth every seven years. Each orbit will com a fraction closer to this planet. It is possible for there to be an impact event if the asteroid 2004 mn4 were to be pulled closer by a gravitational keyhole.

Maybe Friday the 13th isn't as unlucky a day as everyone thinks. Think about this: on April 13th, Friday the 13th, 2029, millions of people are going to go outside, look up and marvel at their good luck. A point of light will be gliding across the sky, faster than many satellites, brighter than most stars.
What's so lucky about that? It's asteroid 2004 mn4 … not hitting Earth. The asteroids orbits after that will be the subject of further study. Many astronomers fear that Apophis will steadily come closer to the Earth and eventually impact. The asteroid is about 320 meters wide. "That's big enough to punch through Earth's atmosphere," devastating a region the size of, say, Texas, if it hit land, or causing widespread tsunamis if it hit an ocean.

The orbit and trajectory of asteroid 2004 mn4 will bend by about 28 degrees during its close encounter with the Earth in 2029. That makes an accurate prediction of its future path very hazy to say the least. Astronomers will be watching how things go very closely. A possible collision with the Earth can only be ruled out, with any authority, for the 2029 event. 2035 is still up in the air.

There are two very interesting pages on NASA.gov about the asteroid 2004 mn4. Here on Universe Today we have a page on the Torino scale score of Apophis and a detailed story about the asteroid 2004 mn4. Astronomy Cast has a great episode on death from above.

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There is a little debate as to which asteroid is the closest asteroid to Earth. Asteroid FU162 has been determined to be the closest, but because it is less than 10 m in diameter, some scientists do not think that it is as significant as Apophis. Apophis is thought to be much more significant because if its size (at 50 km it would be like a city hitting the Earth at 50,000 kph). FU162 passed the Earth at 6500 km above the surface. The previous close-distance record was held by asteroid 2004 FH, which came within 50,000 km.

The closest asteroid FU162 was discovered on March 31 2004, just hours before its closest approach, by the LINEAR survey system in New Mexico, which tracked it over a 44-minute period. The fast-moving image was later identified in processing the images, but it was too late to obtain further observations since the asteroid exited from the dayside of the Earth.

Tim Spahr of the Minor Planet Center contacted the NASA NEO Program Office at JPL to try to extract an orbit, even though the data spanned only a short arc. No pre-recovery data were found, and indeed this asteroid is so small that it could not be seen by survey telescopes except when it was very close to Earth. Orbit calculations, however, did show that this asteroid had come closer than any previously discovered NEA. Based on this orbit, the asteroid was given an official designation. This asteroid shows the capability of LINEAR to find a few of the tiny NEAs that pass very close by the Earth.

The closest asteroid, FU162, is another indicator that the LINEAR program is running very well and efficiently finding NEAs before they can impact the Earth. Thankfully we have several different programs to make sure that we have early enough warning in case of an impact event.

There is a good article on the NASA website about the closest asteroid. Universe Today has an article on asteroid near misses and Astronomy Cast has a good episode on sky surveys.

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The Torino scale uses a score from 0 to 10 to grade the likelihood that an object will impact the Earth. A zero indicates that an object has a very low chance of hitting the Earth or is small enough to burn up in the atmosphere. On the other hand, a 10 indicates an impact that will cause global devastation no matter where on Earth it hits. The scores are calculated based on the likelihood of an Earth impact and and the amount of kinetic energy, in megatons, that will be released.

The Torino Scale was created by Professor Richard Binzel. The first version, called "A Near-Earth Object Hazard Index", was presented at a United Nations conference in 1995. A revised version of the "Hazard Index" was presented at a June 1999 international conference on NEOs held in Torino, Italy. The city lent its name to the scale and the modern Torino Impact Hazard Scale was born.

There have only been three objects that have achieved a score of two or higher on the Torino scale: 2004 VD17, 2007 VK184, and 2004 MN4 Apophis. The first two never registered on other scales for various reasons, Apophis is still the record holder. Apophis hit a 4 on the Torino scale and measured on every other scale for this category of event. A 4 on the Torino scale means that “a close encounter meriting study. A chance greater than 1% of impact causing regional devastation. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.” As you can imagine, Apophis led to quite a bit of excitement in the astronomy realm. Apophis is the first object to be given a rating higher than 1 and still holds the record for the highest score on the Torino scale.

The Torino scale is the most comprehensive scales in astronomy. Nearly every object that is discovered is rated a one on the scale until it is studied a little more, then they are downgraded to a zero. Apophis was an exception to that rule. Science is still a little uncertain what will happen to its orbit after it comes close to a gravitational keyhole in 2029. More study will definitely be in order. Whatever happens you can be assured that the asteroid will be measured accurately by the Torino scale.

Here is a link to the complete Torino scale and another one to its history and use. There are several good articles related to the revised Torino scale and the asteroid Apophis as well as an interesting episode of Astronomy Cast.

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Very few people had heard of near Earth asteroids (NEAs) until 2004. Science went through a brief period where it thought that the Earth was going to be struck. Mock-ups were done to determine the number of people who would be killed and what could be done to avert the tragedy, but nothing was needed. NASA found old records that helped them to prove that the Earth was safe from Apophis once again. It almost sounds like an episode of Stargate SG-1 doesn't it?

With a size of 270 meters and a mass of 2.1 x 10¹⁰ kg, asteroid Apophis could have lived up to its Egyptian name for Uncreator. It is thought that a strike by an object that size could destroy 10% to 25% of the life on Earth. The team of Tholen and Tucker who discovered the asteroid Apophis on June 19, 2004 are also fans of the science fiction television show SG-1. From that show you will recognize the name of the main antagonist for the first several seasons. A true case of art imitating life.

After the Minor Planet Center confirmed the June discovery of the asteroid Apophis, an April 13, 2029 close approach was flagged by NASA. This will make for some spectacular viewing with the unaided eye in rural areas. The asteroid will be visible with binoculars from the brightest suburban areas. The asteroid will pass again in 2036. The 2029 pass will actually be closer than the first predictions, but an impact has been ruled out. Also, the pass on April 13, 2036 carries little risk of an impact.

A brief sense of science fiction come true is the biggest claim to fame that the asteroid Apophis has to its name at this time. Should it hit a gravitational keyhole and change it course enough, we may find ourselves needing a space missile defense system. This asteroid was a test for NASA's Sentry system and the system passed admirably.

Some scientists think that Apophis makes an idea asteroid to visit by spacecraft, to better study the movements of a potentially devastating near Earth asteroid. By placing a beacon direction on the asteroid, astronomers would be able to pinpoint its movements precisely and rule out a risk completely – or give governments time to prepare for an impact…

We have written many articles about Apophis for Universe Today. Here's an article about the size of Apophis.

Want more resources on Apophis? Here's a link to Wikipedia's resource page, and here's NASA's Near Earth Asteroid page.

We have recorded two episodes of Astronomy Cast about asteroids. There's Episode 55: The Asteroid Belt, and here's Episode 29: Asteroids Make Bad Neighbors.

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Question: How Big is Apophis?

Answer: In case you haven't heard, Asteroid 99942 Apophis is a near Earth asteroid that astronomers think will make a close flyby to the Earth in 2029. When its trajectory was first calculated back in 2004, it had one of the closest visits to Earth astronomers had seen, and had a 2.7% chance of hitting the Earth.

But follow-up observations brought that risk down to 1 in 45,000. Right now, astronomers think that Apophis is essentially no risk to the Earth. In April, 2008 media reported that a 13-year old German student had caught a math mistake made by NASA, and the risk of an Earth strike was actually 1-45. This later turned out to be a hoax.

Because of its close approach to Earth, space advocacy societies, including the Planetary Society think that Apophis would make an ideal target for a human mission, and allow engineers to test out strategies for moving asteroids away from dangerous Earth-crossing orbits.

So back to the original question, how big is Apophis? The best estimate puts it at 270 meters (885 feet across), and it has a mass of 2.1 x 10¹⁰ kg. To give you a sense of scale, the Eiffel Tower in Paris is 324 meters tall.

But now you know its mass and size, you're probably wondering: what would happen to the Earth if it struck? NASA estimated that a strike by Apophis would release the equivalent of 880 megatons of energy. Just as a comparison, the object that carved out Meteor Crater in Arizona probably released 3-10 megatons of energy.

If Apophis struck land, it would flatten thousands of square km of land, killing millions of people if it hit a densely populated area. But it wouldn't cause the kinds of long term climate destruction that 1 km and larger asteroids can do. If it hit an ocean, it would create devastating tsunamis in all directions.

Here's an article explaining techniques that might be used to move an asteroid. And here's NASA's official page on Apophis.

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