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VLBA Measures Asteroid's Characteristics
In an unusual observation, astronomers used the National Science Foundation's Very Long Baseline Array (VLBA) to study the effects on radio waves coming from a distant radio galaxy when an asteroid in our Solar System passed in front of the galaxy. The observation allowed them to measure the size of the asteroid, gain new information about its shape, and greatly improve the accuracy with which its orbital path can be calculated.
When the asteroid passed in front of the galaxy, radio waves coming from the galaxy were slightly bent around the asteroid's edge, in a process called diffraction. As these waves interacted with each other, they produced a circular pattern of stronger and weaker waves, similar to the patterns of bright and dark circles produced in terrestrial laboratory experiments with light waves.
"By analyzing the patterns of the diffracted radio waves during this event, we were able to learn much about the asteroid, including its size and precise position, and to get some valuable clues about its shape," said Jorma Harju, of the University of Helsinki in Finland.
The asteroid, named Palma, is in the main asteroid belt between Mars and Jupiter. Discovered in 1893 by French astronomer Auguste Charlois, Palma completes an orbit around the Sun every 5.59 years. On May 15, 2017, it obscured the radio waves from a galaxy called 0141+268 with the radio shadow tracing a path running roughly southwest to northeast, crossing the VLBA station at Brewster, Washington. The shadow sped across the Earth's surface at 32 miles per second.
(Score: 3, Informative) by PartTimeZombie on Sunday September 16 2018, @08:59PM (4 children)
Not quite 200 kilometres long.
Also, from the Wikipedia article:
which seems a bit unnecessary, how many main-belt asteroids are going to hit the Earth? It is something of a relief however. My lawn is just starting to look nice and it would make a mess.
(Score: 2) by takyon on Sunday September 16 2018, @11:01PM (1 child)
Pretty big for an asteroid. It's the 32nd largest known asteroid by diameter [wikipedia.org], out of hundreds of thousands known. I read the Wikipedia text you mentioned and yes it is silly.
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(Score: 2) by PartTimeZombie on Sunday September 16 2018, @11:04PM
Oh, yes, quite right. It is big for an asteroid, I think I was trying to make the point that it is small and hard to see from Earth.
(Score: 1, Interesting) by Anonymous Coward on Monday September 17 2018, @01:59AM (1 child)
I did a few calculations, based the stats on the Wikipedia page, for what would happen if it did hit the earth [ic.ac.uk]. The speed of 12.2 km/s is based on the asteroid's mean orbital velocity. The diameter of 191.524 is such that the volume times the listed 1.40 g/cm3 density yields the mass of 5.15×1018 kg. 3.83×1026 joules is about a thousand times more energy than that of the asteroid that killed the dinosaurs. The last time the earth might have experienced such an impact was at latest probably during the Late Heavy Bombardment, before the planet was fully formed.
(Score: 2) by PiMuNu on Monday September 17 2018, @11:16AM
So not good for lawns then?