Category: Asteroids

In case you had any doubts, it’s now official: Asteroid 2007 TU 24 will not impact or have any affect on Earth. Astronomers have obtained the first images of the near earth asteroid using high-resolution radar data. “With these first radar observations finished, we can guarantee that next week’s 1.4-lunar-distance approach is the closest until at least the end of the next century,” said Steve Ostro, Jet Propulsion Laboratory astronomer and principal investigator for the project. “It is also the asteroid’s closest Earth approach for more than 2,000 years.”

The radar images indicate the asteroid is somewhat asymmetrical in shape, with a diameter roughly 250 meters (800 feet) in size. Asteroid 2007 TU24 will pass within 1.4 lunar distances, or 538,000 kilometers (334,000 miles), of Earth on Jan. 29 at 12:33 a.m. Pacific time (3:33 a.m. Eastern time). So, while this image is pretty faint, (about 20 meters per pixel) as the asteroid gets closer, NASA will be able to obtain better images and more details about the object.

And just to repeat for anyone who still has any doubts, the scientists at NASA’s Near-Earth Object Program Office at JPL have determined that there is no possibility of an impact with Earth in the foreseeable future.

Asteroid 2007 TU24 was discovered by NASA Oct. 11, 2007. The asteroid should be visible to amateur astronomers using 3 inch (7.6 centimeter) telescopes. It will be brightest on January 29-30, reaching an approximate apparent magnitude of 10.3, and then become fainter as it moves farther from Earth. Anyone looking for the asteroid with amateur telescopes will need dark and clear skies. An object with a magnitude of 10.3 is about 50 times fainter than an object just visible to the naked eye in a clear, dark sky.

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called “Spaceguard,” discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet. They use several different tracking devices including the Goldstone’s 70-meter diameter (230-foot) antenna that is capable of tracking a spacecraft traveling more than 16 billion kilometers (10 billion miles) from Earth.

Ostro and his team plan further radar observations of asteroid 2007 TU24 using the National Science Foundation’s Arecibo Observatory in Puerto Rico on Jan. 27-28 and Feb. 1-4.

Original News Source: JPL Press Release

One of the most spectacular sights in the night sky is a fireball; a rock from space impacts the atmosphere and blazes a trail that can last seconds or even minutes. These burn up harmlessly, but when do they turn dangerous? When do asteroids get large enough that they can actually get through the atmosphere and cause some destruction here on the ground?

During an invited talk at the Meteoroids 2007 conference held in Barcelona, Spain, Clark R. Chapman from the Southwest Research Institute delivered a presentation about how to define this line between harmless explosion in the sky and an impact that causes destruction here on the ground. The paper, entitled Meteoroids, Meteors, and the Near-Earth Object Impact Hazard was later published in the journal Earth, Moon and Planets.

Originally, researchers focused their efforts on the largest asteroids: the objects 2 km (1.2 miles) and above. These are the space rocks that could cause wide scale devastation across the planet, affecting the climate and leading the the deaths of hundreds of millions of people. It was calculated that an individual might have a 1-in-25,000 chance of dying in an asteroid impact.

Now that the Spaceguard Survey has discovered 75% of the asteroids 1 km and larger, your chances of dying have dropped to about 1-in-720,000. About the same chance as dying from a fireworks accident or amusement park ride.

According to Chapman, astronomers are now shifting their focus from the largest impacts – like the one that wiped out the dinosaurs 65 million years ago – to the smaller, but still dangerous space rocks. For example, the rock that detonated in the air above Tunguska, Siberia in 1908. That object was probably only between 20-100 metres (65-325 feet) across.

And yet, it leveled the forest for thousands of square kilometres and would have caused immense destruction if it had hit a populated area.

A new survey, informally called the Spaceguard Two Survey, will begin soon with the goal of finding 90% of the near-Earth asteroids larger than 140 metres (460 feet) within the next 15 years.

There are many variables that go into calculating the resulting destruction from an impact. You have to consider the velocity, if it’s a metallic or rocky asteroid, and whether it’s fragmented or not.

What should the response be of national and international emergency management officials to a prediction that a 35 m NEA will strike a populated country a decade in the future? Following current interpretations, we would simply tell people near ground-zero to stay inside and not look directly at the high-altitude explosion. But if objects of that size could cause Tunguska-like damage, we might not only evacuate people for 100 km surrounding ground-zero but we would certainly consider a space mission to move or blow-up the threatening NEA.

Originally, researchers thought that Tunguska level events happened once in 4,000 years, but it might be more common, maybe as often as 1-in-700. And perhaps even smaller, more common, asteroids could still cause destruction on the ground – 1-in-200 years.

If Spaceguard Two Survey gets going, it should locate most of the larger asteroids, but even 50% of the Tunguska-sized impactors. It will even be tracking 1-2 million 30 metre objects.

And if one of those rocks is on a collision course with Earth, governments and space agencies will be able to work out an evacuation or prevention strategy.

Or at least encourage people to avert their eyes.

Original Source: SWRI

When astronomers first made the connection between asteroid impacts and extinction events on Earth, it was kind of frightening. There are hundreds of thousands of those things out there zipping around! But dedicated asteroid hunters have located many of the largest planet smashers, and new programs are in the works to find the rest. But now it seems that even the smaller asteroids could be more destructive than previously believed.

Almost 100 years ago, something detonated in the atmosphere above Tunguska, Siberia, flatting the forest. Had it struck a populated area, the results would have been disastrous.

But now researchers have simulated the kind of spacerock that caused the Tunguska explosion. And here’s the bad news: it was probably a much smaller object than previously believed.

“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”

Since smaller asteroids are more likely to hit the Earth than larger objects, we might want to get a little more concerned about the risks.

A new supercomputer simulation recreated the kind of fireball that could have caused the Tunguska explosion. They took into account how winds travel along the topography of the ground, and the health of the forest to see how easily the trees would be blown down.

What was originally believed to be a 10-20 megaton explosion was probably only 3-5 megatons. So it took a much smaller object to create the devastation in Tunguska.

The researchers didn’t actually suggest a new size for the object, estimating that sounds complicated. “It depends on the speed and whether it’s porous or nonpourous, icy or waterless, and other material characteristics.”

Original Source: Sandia News Release

Remember when I mentioned that ESA’s Rosetta was inbound to make a flyby of the Earth on November 13th? Well, another group of astronomers were watching this “unknown” object, and thought that it was actually an asteroid that was going to be making a close flyby of our planet. The astronomers realized their mistake, but not after an alert was sent out to the astronomical community. Oops.

The alert was sent out by the Minor Planet Center, a clearinghouse of asteroid information organized by the Smithsonian Astrophysical Observatory for the International Astronomical Union.

Astronomers had been tracking the approaching object, designated 2007 VN84. After many observations from astronomers around the world, they calculated that it would pass us by at a distance of 1.89 radii (from the middle of the Earth).

It would have been huge news, but Denis Denisenko from Moscow’s Space Research Institute (IKI) realized that its flight path perfectly matched the upcoming Rosetta flyby.

Here’s a link to an animation, captured by astronomers in Germany, of Rosetta inbound to the Earth.

And so, just to set the record straight, ESA’s Rosetta spacecraft made its flyby on Tuesday, November 13th at 20:57 GMT, passing just 5,301 km above the Pacific Ocean. This has given it the gravitational boost it needs to meet up with Comet Churyumov-Gerasimenko in 2014.

Original Source: MPEC Alert