100ft-wide asteroid set to brush by the Earth

Scientists are urging people not to panic after learning a 100ft-wide asteroid could be about to brush by the Earth at a distance close enough to threaten orbiting satellites.

The space rock, named 2013 TX68, is expected to make its nearest approach to Earth early next Tuesday.

But the precise timing of its visit and trajectory will not be known until after the event.

The asteroid could shoot past the Earth inside the ring of communications and GPS satellites located in fixed positions 22,300 miles (35,890 km) above the equator, experts say.

At the other limit of its predicted path range it could remain as far out as 40 times the distance to the moon.

Even if 2013 TX68 were going to make contact with Earth, an asteroid this size poses no catastrophic threat.

While it’s currently the size of a blue whale, Earth’s atmosphere would make quick work of the asteroid, whittling it down to a fraction of its current size. But it could still cause some damage.

If it were to enter earth’s atmosphere it would generate a radiant fireball that would explode close to the surface, but before hitting the ground.

These are called an air burst, and it’s the blast wave from air bursts like these that can be dangerous.

The Chelyabinsk event in 2013, for example, generated three different air bursts, the most powerful of which released the equivalent energy of 500,000 tons of TNT.

US scientist Seán Marshall, of Cornell University in New York, who studies near-Earth objects such as comets and asteroids said: “Should this asteroid come closer than the geostationary satellites, it would be a rare occurrence — that only happens about once per decade for large asteroids.

“What we know for sure is that it will not collide with Earth this month, so do not panic.”

He added: “The large uncertainty in TX68’s orbit makes it difficult to plan observations in advance, but hopefully it will be seen by some of the automated asteroid survey telescopes.

“However, it is possible that TX68 will be so far from Earth that it will be too faint to be seen.

"If TX68 is detected this month, that would greatly reduce the uncertainty in its orbit and allow astronomers to calculate its future trajectory much more accurately.”

Geostationary satellites all circle the equator and have orbits that match the rotation of the Earth, so they remain above one fixed point.