Image caption Esa's Herschel Space Observatory captured Apophis in its field of view in the far-infrared light in January 2013 
 
 A 300 metre-wide asteroid is making a close pass to the Earth. 
 
 Apophis - named after the Egyptian demon of destruction and darkness - has been put on a watch list by scientists. 
 
 They have calculated that in 2036 there is a very small chance it could collide with our planet. 
 
 However, its current fly-by is at a safe distance of about 14 million km - but this is close enough for astronomers to study the space rock and assess its future risk. 
 
 Apophis will not be visible with the naked eye, but space enthusiasts can watch it online via the Slooh space camera's website. 
 
 Collision course? 
 
 The large rocky mass was first discovered in 2004. At the time, it raised alarm when scientists calculated that it had a one-in-45 chance of smashing into the Earth in 2029. 
 
 At some point, we are going to find an asteroid big enough that it could cause damage at ground level if we let it hit Prof Alan Fitzsimmons, Queen's University Belfast 
 
 Later revisions, lifted this threat; instead on the Friday 13 April 2029, it will make a close pass at a distance of about 30,000km. 
 
 However, astronomers say there is still a one-in-200,000 chance that it could strike Earth in 2036. 
 
 Professor Alan Fitzsimmons, an astronomer at Queen's University Belfast, UK, said: "In 2029, it will pass so close to us that Earth's gravity will change its orbit. 
 
 "Most of the potential orbits it will end up on will mean we are safe for the next 100 years. But there is a small region of space - something we call a keyhole - and if it passes through that keyhole in 2029, it will come back and hit us on 13 April in 2036." 
 
 If this happened, it would strike the Earth with 100 times the energy in our largest nuclear bombs, said Prof Fitzsimmons. 
 
 Future hazards 
 
 Astronomers are using the current close encounter as an opportunity to study the asteroid, so they can improve their calculations to predict its future path. 
 
 Prof Fitzsimmons said: "While [the asteroid] is relatively close to the Earth, astronomers can ping it with radar. Radar measurements are incredibly accurate: we get the distance to the asteroid very, very precisely, and we can also get its velocity relative to us. And these two things let us pin its orbit down very precisely. " 
 
 Researchers are becoming increasingly interested in potentially hazardous asteroids. 
 
 So far they have counted more than 9,000 near-Earth asteroids, and they spot another 800 new space rocks on average each year. 
 
 Prof Fitzsimmons said learning more about them was vital. 
 
 "At some point, we are going to find an asteroid big enough that it could cause damage at ground level if we let it hit," he explained. 
 
 "So we should find these objects, we should track them, work out where they are going - and if they stand a chance of hitting us, do something about it." ||||| Apophis hit the headlines in December 2004. Six months after its discovery, astronomers had accrued enough images to calculate a reasonable orbit for the 300-metre chunk of space rock. What they saw was shocking. 
 
 There was a roughly 1 in 300 chance of the asteroid hitting Earth during April 2029. Nasa issued a press release spurring astronomers around the world to take more observations in order to refine the orbit. Far from dropping, however, the chances of an impact on (you've guessed it) Friday 13 April 2029 actually rose. 
 
 By Christmas Day 2004, the chance of the 2029 impact was 1 in 45 and things were looking serious. Then, on 27 December astronomers had a stroke of luck. 
 
 Looking back through previous images, they found one from March on which the asteroid had been captured but had gone unnoticed. This significantly improved the orbital calculation and the chances of the 2029 impact dropped to essentially zero. However, the small chance of an impact in 2036 opened up and remains open today. 
 
 While there is no cause for alarm, similarly there is no room for complacency either. Apophis remains on the list of Potentially Hazardous Asteroids compiled by the International Astronomical Union's Minor Planet Center. 
 
 Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there. Apophis belongs to a group known as the Aten family. These do not belong to the asteroid belt and spend most of their time inside the orbit of the Earth, placing them between our planet and the sun. 
 
 That makes them particularly dangerous because they spend the majority of their orbit close to the sun, whose overwhelming glare obscures them to telescopes on Earth – rather like a second world war fighter ace approaching out of the sun. 
 
 Having crossed outside Earth's orbit, Apophis will appear briefly in the night-time sky. Wednesday 9 January will afford astronomers the rare opportunity to bring a battery of telescopes to bear: from optical telescopes to radio telescopes to the European Space Agency's Infrared Space Observatory Herschel. Two of the biggest unknowns that remain to be established are the asteroid's mass and the way it is spinning. Both of these affect the asteroid's orbit and without them, precise calculations cannot be made. 
 
 Another unknown is the way sunlight affects the asteroid's orbit, either through heating the asteroid or the pressure of sunlight itself. Russia has announced tentative plans to land a tracking beacon on Apophis sometime after 2020, so that its orbit can be much more precisely followed from Earth. 
 
 Wednesday's pass is only really close by astronomical standards, taking place at around 14.5 million kilometres above Earth's surface. The moon's orbit is 385,000 km. The 2029 close pass is another matter entirely, however. 
 
 On Friday 13 April 2029, Apophis will slip past the Earth just 30,000km above our heads – less that one-tenth the distance of the moon and closer even than the communication satellites that encircle the Earth at 36,000km. It will appear as a moderate bright moving object, visible from the mid-Atlantic. Depending upon its composition, astronomers could watch the Earth's gravity pull the asteroid out of shape, offering an unprecedented insight into its composition. 
 
 So, although Apophis poses no immediate danger, we are almost certain to hear a lot more about it over the coming years and decades. Apart from all the science we can learn, its orbit's proximity to Earth's makes it a potential target for future robotic and even manned missions. 
 
 Stuart Clark is the author of Voyager: 101 Wonders Between Earth and the Edge of the Cosmos (Atlantic). ||||| ESA’s Herschel Space Observatory captured asteroid Apophis in its field of view during the approach to Earth on January, 5-6, 2013. This image shows the asteroid in Herschel’s three PACS wavelengths: 70, 100 and 160 microns. 
 
 Credit: ESA/Herschel/PACS/MACH-11/MPE/B.Altieri (ESAC) and C. Kiss (Konkoly Observatory) View full size image 
 
 A European space telescope has captured new images of the huge asteroid Apophis, revealing that the potentially hazardous object is actually bigger than previously thought — and you have a chance to see the space rock yourself in two free webcasts tonight (Jan. 9). 
 
 Asteroid Apophis has long been billed as a "doomsday asteroid" because of a 2004 study that predicted a 2.7 percent chance of the space rock hitting Earth when it passes within 22,364 miles (36,000 kilometers) of the planet in April 2029, European Space Agency officials said. Later studies proved, however, that the asteroid poses no threat to Earth during that flyby, but astronomers continue to track the object since it will make another pass near Earth in 2036. 
 
 At about 36 hours from the minimum distance (9.3 million miles or 15 million kilometers from Earth), potentially hazardous asteroid Apophis was imaged again with the Virtual Telescope, on Jan. 8, 2013. 
 
 Credit: G. Masi & F. Nocentini View full size image At about 36 hours from the minimum distance (9.3 million miles or 15 million kilometers from Earth), potentially hazardous asteroid Apophis was imaged again with the Virtual Telescope, on Jan. 8, 2013. 
 
 Today, ESA officials announced that its infrared Herschel Space Observatory has discovered that Apophis is about 1,066 feet (325 meters) wide, nearly 20 percent larger than a previous estimate of 885 feet (270 m). 
 
 "The 20 percent increase in diameter … translates into a 75 percent increase in our estimates of the asteroid's volume or mass," study leader Thomas Müller of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, said in a statement. [Photos of Near-Earth Asteroid Apophis] 
 
 Tonight's two free webcasts will stream live views of Apophis from telescopes in Italy and the Canary Islands tonight (Jan. 10). The webcasts, offered by the stargazing websites Slooh Space Telescope and Virtual Telescope Project, will show Apophis as a bright light moving across the night sky. The asteroid is too small to be seen through small backyard telescopes. 
 
 The Slooh Space Camera webcast will begin at 7 p.m. EST (0000 Jan. 10 GMT). The Virtual Telescope webcast will begin an hour later at 8 p.m. EST (0100 GMT). You can watch both live webcasts of asteroid Apophis here on SPACE.com tonight. 
 
 Apophis will be just under 9.3 million miles (15 million kilometers) from Earth at the time of tonight’s webcasts, amateur astronomer Gianluca Masi of the Virtual Telescope Project told SPACE.com. 
 
 "Alone among all these near-Earth asteroids that have passed our way in recent years, Apophis has generated the most concern worldwide because of its extremely close approach in 2029 and [chances of a] potential impact, albeit small, in 2036," Slooh president Patrick Paolucci said in a statement. 
 
 An artist's rendering of the asteroid Apophis. 
 
 Credit: European Space Agency View full size image An artist's rendering of the asteroid Apophis. 
 
 In addition to asteroid Apophis, astronomers regularly scan the night sky for asteroids that may pose a potential impact threat to Earth. NASA's Near-Earth Object Office and Asteroid Watch program is based at the agency's Jet Propulsion Laboratory in Pasadena, Calif. 
 
 You can track Apophis directly via the Virtual Telescope Project here: http://www.virtualtelescope.eu/webtv/ 
 
 The webcast from the Slooh Space Camera can also be seen here: http://events.slooh.com/ 
 
 This story was provided by SPACE.com, a sister site to LiveScience. You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.
– The asteroid Apophis, whose reported threat to our planet has attracted widespread attention, is even larger than scientists believed, according to new images. Europe's Herschel Space Observatory says the asteroid is some 1,066 feet feet wide, some 20% wider than previously thought. That "translates into a 75% increase in our estimates of the asteroid's volume or mass," says the study's leader. Fortunately, we survived yesterday's passage, and reports that there was a 2.7% chance it would hit Earth in 2029 have been debunked. But scientists are still investigating the asteroid, which will pass near us again in 2036, LiveScience notes. At that point, there remains a one-in-200,000 chance of a collision, the BBC reports. "There is a small region of space—something we call a keyhole—and if it passes through that keyhole in 2029, it will come back and hit us on 13 April in 2036," says a scientist. It would carry 100 times the energy of our biggest nuclear weapons, he adds. "While there is no cause for alarm, similarly there is no room for complacency," writes Stuart Clark at the Guardian, which has video.