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Asteroid Apophis provides astronomers a chance to study a massive space rock

With asteroid Apophis no longer posing much of a threat to Earth, astronomers are poring over data captured as the monster space rock whizzed passed Earth late Wednesday.

With the latest observations confirming the asteroid will miss Earth by a mere 20,000 miles in 2029 — and by a similar margin seven years later in 2036 — astronomers say they will now focus on crafting a better understanding of the cosmic behemoths.  using the Herschel Space Observatory made new observations of asteroid Apophis as it approached Earth this past weekend. The team, which collected the data that shows the asteroid to be both bigger than first estimated and less reflective, said

“As well as the data being scientifically important in their own right, understanding key properties of asteroids will provide vital details for missions that might eventually visit potentially hazardous objects,” said Laurence O’Rourke from the European Space Astronomy Center (ESAC) near Madrid, Spain. “Apophis is only the second near-Earth asteroid observed by Herschel, and these were the fastest tracked observations by the space telescope — the asteroid moved at a rate of 205 arcseconds per hour as seen from Herschel’s viewpoint.”

Working over the weekend, Herschel — which works in coordination with the U.S. space agency NASA — gathered data while observing Apophis for about two hours on its approach to Earth. The Herschel team was the first to capture images of the asteroid as it closed in on Earth, providing astronomers around the world with the first bits of data. Astronomers used the early sets of data to better revise their estimates of the asteroid’s size, which was later announced to be nearly 20 percent larger than previous estimates — the equivalent of a 75 percent increase in the asteroid’s mass.

“The 20 percent increase in diameter from 890 feet (270m) to 1,065 feet (325m) translates into a 75 percent increase in our estimates of the asteroid’s volume or mass,” said Thomas Müller of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany.

With a world’s worth of astronomers studying the asteroid’s passing, the astronomy community will likely now have access to data that could play a crucial role in a series of planned missions to asteroids around the solar system. Already, NASA has announced plans to send a manned mission to a nearby asteroid, while Russia’s space agency has announced plans to possibly intercept Apophis during its next flyby.

Among astronomer’s most important findings relates to the asteroid’s ability to generate heat. 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. The data will like play a role in how NASA engineers prepare astronauts traveling to asteroids.

With Apophis on its way out, astronomers say they plan to continue to study the massive asteroid and its classification as a near Earth object (NEO).

“Although Apophis initially caught public interest as a possible Earth impactor, which is now considered highly improbable for the foreseeable future, it is of considerable interest in its own right, and as an example of the class of near Earth objects,” said Göran Pilbratt from ESA. “Our unique Herschel measurements play a key role for the physical characterization of Apophis, and will improve the long-term prediction of its orbit.”

The latest data on Apophis comes as NASA issued its first statements on the asteroid’s passing. NASA officials confirmed Herschel astronomer’s data, saying the revised figures show Apophis will not impact Earth in 2036.

“The impact odds as they stand now are less than one in a million, which makes us comfortable saying we can effectively rule out an Earth impact in 2036,” Don Yeomans, manager of NASA’s Near-Earth Object Program Office, said in a statement issued Friday.  “Our interest in asteroid Apophis will essentially be for its scientific interest for the foreseeable future,” Yeomans said.

When Apophis does pass Earth on April 13, 2029, it will come within just 19,400 miles (31,300 km) of Earth. The distance places the asteroid well within the orbit of a number of satellites and it remains unclear if NASA will, at some point, announce plans to avoid paths that place satellites within the path of the 1000-foot asteroid.

“But much sooner, a closer approach by a lesser-known asteroid is going to occur in the middle of next month when a 40-meter-sized asteroid, 2012 DA14, flies safely past Earth’s surface at about 17,200 miles,” said Yeomans. “With new telescopes coming online, the upgrade of existing telescopes and the continued refinement of our orbital determination process, there’s never a dull moment working on near-Earth objects.”

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