Homepage Educators and Developers Homepage

Discussion questions

> Asteroid with Six Comet-like Tails

DEC. 2013

Asteroid with Six Comet-like Tails Surprises Astronomers

Asteroid with many tails

Asteroid on Sept. 10, 2013:
Many tails are visible

The Hubble Space Telescope has found an odd-looking asteroid with six comet-like tails of dust streaming from its body like spokes on a wheel.

Astronomers spotted the asteroid in our solar system's asteroid belt, a reservoir of space rocks between the orbits of Mars and Jupiter. Asteroids are some of the leftover debris from the construction of our solar system 5 billion years ago.

Comet anatomy promo image

Comet anatomy
changes as it approaches the Sun

The object's unusual appearance has puzzled astronomers. Almost all other known asteroids look like tiny points of light and do not have tails of dust trailing behind them. Tails are normally seen trailing from comets, when they orbit near the Sun. Comets are made up of ice, dust, and some rock. They hail from the outer solar system and visit the inner solar system during their journey around the Sun. As comets get closer to the Sun, they develop tails when some of their ice vaporizes and gets pushed away from them.

Astronomers also noticed that the tail structure of this oddball asteroid changed dramatically over just two weeks as it released dust. Hubble images have shown that the ancient asteroid, known as P/2013 P5, has been ejecting dust periodically for at least five months.

Why is the asteroid losing material? Astronomers hypothesize that over billions of years the asteroid began rotating faster and faster, eventually causing it to start losing material from its surface. The researchers do not think the tails formed from a collision with another asteroid. A collision would cause a large cloud of dust to blast into space all at once. A series of Hubble telescope images, taken over five months, has not shown that type of catastrophic event.

Instead, calculations show that the tails could have formed by a series of dust ejection events, from April 15 to Sept. 4. A rather curious feature is that between the Hubble observations on Sept. 10 and Sept. 23, the entire structure appeared to have swung around.

So far, the asteroid has lost a small amount of its mass. Its nucleus, which measures 1,400 feet wide, is thousands of times more massive than the observed amount of ejected dust.

Astronomers will continue observing the unusual object. Asteroids that fall apart by spinning too fast may be common in the asteroid belt. As one researcher said, "In astronomy, where you find one, you eventually find a whole bunch more."

Asteroid P/2013 P5 may be a fragment of a larger asteroid that broke apart in a collision roughly 200 million years ago. Many collision fragments are in orbits similar to that of P/2013 P5. Meteorites from these bodies show evidence of having been heated to as much as 1,500 degrees Fahrenheit. This evidence means the asteroid is probably made up of rocks and does not hold any ice as a comet does.

The asteroid was discovered as an unusually fuzzy-looking object with the Pan-STARRS survey telescope in Hawaii. The multiple tails were discovered in Hubble images taken on Sept. 10, 2013.


The Star Witness

brings you "tele-scoops" from the Hubble Space Telescope