Asteroid Apophis Grazed The Earth Last Night, Is Much Larger Than Previously Thought

Scientists using the Herschel Space Observatory made new observations of The giant asteroid Apophis, which grazed the Earth last night, has been found to be much larger than it was previously thought to be. During its approach over the past few days researchers have been able to gather valuable data on it, allowing them to get a better estimate of its size and trajectory. In addition to be larger, the asteroid is also less reflective than previously estimated.


Researchers discovered the asteroid in 2004, at that time it was estimated to have about a 2.7% chance of striking the Earth in 2029. “Additional observations of the asteroid ruled out any possibility of an impact in 2029. However, Apophis is expected to make a record-setting — but harmless — close approach to Earth on April 13, 2029, when it comes no closer than 18,300 miles (29,450 kilometers) above Earth’s surface. The asteroid will make another approach to Earth in 2036. Data collected by telescopes during today’s close approach are expected to refine the asteroid’s orbit to the point where an impact in 2036 can be ruled out.”

“Over the weekend, Herschel gathered data while observing Apophis for about two hours on its approach to Earth, ahead of today’s closest encounter at a little less than one-tenth of the distance from Earth to the sun: about 9 million miles (14.5 million kilometers). The space observatory provided the first thermal infrared observations of Apophis at different wavelengths, which together with optical measurements helped refine estimates of the asteroid’s properties. Previous estimates bracketed the asteroid’s average diameter at about 885 feet (270 meters). Herschel’s observations indicate the space rock is about 1,060 feet (325 meters) across.”

“By analyzing the heat emitted by Apophis, Herschel also provided a new estimate of the asteroid’s albedo — a measure of its reflectivity– of 0.23. This value means that 23 percent of the sunlight falling onto the asteroid is reflected; the rest is absorbed and heats up the asteroid. The previous albedo estimate for Apophis was 0.33.”

Source: NASA/Jet Propulsion Laboratory

Image Credits: ESA/Herschel/PACS/MACH-11/MPE/ESAC

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