Category: Asteroids

Since asteroids have mass, they have gravity. And if you’ve got gravity, you can have moons. Several asteroids have been discovered in the outer Solar System with smaller asteroidlets circling them. But now the Arecibo radio telescope in Puerto Rico has turned up the closest example – a triple system just a mere 11 million km (7 million miles) from Earth.

Asteroid 2001 SN263 was revealed to be a triple system by Cornell astronomer Michael C. Nolan. The asteroid itself had been discovered back in 2001 as part of an automated survey. He and his colleagues captured radio images of the space rocks on February 11. By studying the images, they realized that they actually had a system of three objects.

The main central asteroid is roughly 2 km (1.5 miles) across. The larger “moon” is about half that size, and the smallest is about 300 metres (1,000 feet) across.

Asteroid systems like this have been seen in the Asteroid Belt, between Mars and Jupiter, but never so close. This allows scientists to image it with unprecedented detail.

As researchers find more and more near-Earth asteroids, they’re starting to realize that binary systems are actually quite common. According to Nolan, one in six near-Earth asteroids is a binary. Although, this is the first near-Earth triple system seen.

Multiple asteroid systems are very useful for astronomers; they provide the mass calculation. In a multiple object system like this, you can calculate the mass of each object by knowing the various periods (the time they take to complete an orbit). Researchers can then compare the mass of the binary objects to the brightness of single asteroids to estimate their masses as well.

One of the big unanswered questions: did the three objects form together, or were they captured later on? By watching the system over time, Nolan and his team will get a better sense if they’re orbiting on the exact same plane (like our Solar System). This will be evidence they formed together billions of years ago.

Arecibo is one of the best asteroid hunting tools available to astronomers; unfortunately, budget cuts in the United States has put the future of the facility in jeopardy.

Original Source: Cornell News Release

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