Rogue asteroid a fifth bigger than thought, says ESA

Agence France Presse

Published — Friday 11 January 2013

Last update 11 January 2013 12:44 am

| نسخة PDF Print News | A A

PARIS: An asteroid believed to pose a remote risk of colliding with Earth this century is 20 percent bigger than previously thought, the European Space Agency (ESA) said on Wednesday.
In a press release, ESA said its Herschel deep-space telescope had scanned a space rock called 99942 Apophis last weekend as it headed toward its closest flyby with our planet in years on Wednesday.
Previous estimates bracketed the asteroid’s average diameter at 270 meters (877 feet) give or take 60m (195 feet), representing a mass that would equal the energy release of a 506-megaton bomb, according to NASA figures.
In a two-hour observation, Herschel returned a diameter of 325m (1,056 feet), with a range of 15m (48.75 feet) either way, ESA said.
“The 20-percent increase in diameter, from 270 to 325m (877 to 1,056 feet), translates into a 75-percent increase in our estimates of the asteroid’s volume or mass,” said Thomas Mueller of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, who led the data analysis.
Named after the god of evil and darkness in Egyptian mythology, Apophis sparked a scare when it was first detected in 2004. Early calculations suggested a 2.7-percent probability of collision in 2029, the highest ever for an asteroid, but the risk was swiftly downgraded after further observations.
A distance of 35,000 kilometers (22,500 miles), meaning it will flit past inside the orbit of geostationary satellites, is the latest estimate for 2029, ESA said.
There remains a tiny impact risk of about one in 250,000 on April 13, 2036, when it will pass even closer to Earth, according to NASA’s Jet Propulsion Laboratory (JPL). Astronomers hope that Wednesday’s flyby, with Apophis due to zip past at a distance of some 14.5 million kilometers (nine million miles), will help them fine tune the 2029 and 2036 estimates.
Herschel, using thermal sensors, also found that Apophis is somewhat darker than thought, ESA added.
Only 23 percent of light that falls on it is reflected, and the rest is absorbed by the asteroid. Previous estimates of this reflectivity, known as albedo, were in the order of 33 percent.
This finding is important because asteroids experience something called the Yarkovsky effect, or an increase in thrust that comes from alternate heating and cooling as the rock slowly turns in space.
Over time, this momentum can change the body’s trajectory as it moves through the Solar System.
On Feb. 15, a 57-meter (185-feet) asteroid, 2012 DA14, will skim the planet at just 34,500 kilometers (21,600 miles), making the narrowest approach so far of any detected asteroid.

What's happening around Saudi Arabia

RIYADH: A number of parents have complained about the lack of hygiene in schools, expressing fears about the potential spread of the MERS virus with the beginning of the new academic year. This comes in the backdrop of another death due to the deadly...
JEDDAH: Disputes over sharing of property or inheriting family business are common. But Dhahran has witnessed an unusual fight among four brothers — over donating kidney to their youngest brother.Coincidentally, all the brothers were found fit to don...
JEDDAH: A number of visually impaired citizens are expecting candidates to address their problems and make life easier for them after winning the Dec. 12 municipal elections.A section of these voters have also sought special programs so that they can...
RIYADH: The Ministry of Interior recently launched a series of training programs to upgrade the efficiency of its female staff as a new step to empower women and give them an opportunity to shine in security-related fields.Maha Frehi, the manager of...
RIYADH: Sixty-one Filipinos, who met with a vehicular accident on the day of Arafat on Nov. 5, 2011, hope to come to the Kingdom as the guests of Custodian of the Two Holy Mosques King Salman.Most of them could not complete the Haj rituals because of...
JEDDAH: At the start of each academic year, parents face a common and expected problem — their children are afraid of going to school.After spending five years in the arms of their mothers and siblings, children know leaving home means entering a new...

Stay Connected