Theme 10 – Leftovers: Meteors and Asteroids ASTR 101 Prof. Dave Hanes

Meteors: Individual, or in Groups - not “falling stars!”

To Be Precise Meteoroid = the pebble out in space Meteor = the luminous event we see (the trail of the “falling star”) Meteorite = any surviving lump that we find on the ground

What We Are Seeing Most meteors are small (tiny pebbles, or even grains, of rocky material) They enter Earth’s atmosphere at very high speed (many tens of km/sec) Air resistance slows them and heats both the pebble and the column of air – this is what we see, not the pebble itself

Some Can be Very Bright

A Range of Sizes (‘Pebbles’ burn up!) A Range of Sizes (‘Pebbles’ burn up!)

Ahnigito (“The Tent”) Meteorite 31 tonnes; fell ~ 10,000 years ago

Duck!

Finding Them on the Ground Various types: stony (undistinguished!) carbonaceous chondrites, iron (very distinctive!), …

A Good Hunting Ground!

Meteor Showers Not all meteors come in singly.

Remants of Evaporated Comets A comet breaks up The rubble gets spread out

Moving ‘Gravel Pits’ - and a trick of perspective

The Shower has a‘Radiant’ - hence the name (e.g. the Perseids, in August)

The Leonids in 1833 and 2001

Asteroids

We Can Visit Them (Vesta and Ceres)

Finding New Ones

‘Earth-Crossing’ Orbits

We Do Get Hit! [here, about 30,000 years ago]

The Speed is the Key Factor All of the kinetic energy (the energy of motion) is released when the moving object hits the target. A 1-gram pebble moving 100 km/sec has as much kinetic energy as a 10-ton truck moving along the highway at 100 km/hour old-the-900-mph-supersonic-ping-pong-bazooka

The Same Basic Physics!

Local Examples

Relatively Recently, in Russia

Very Recently in Chelyabinsk, Russia Even a ‘miss’ can be quite destructive

Back to Tunguska

How about biggerstill?