Oct 18th: One Comet, Twin Asteroids, or Both?


Podcaster: Richard Drumm
Space Scoop: One Comet, Twin Asteroids, or Both?

Organization:365 Days Of Astronomy

Link : astrosphere.org ; http://unawe.org/kids/unawe1119/

Description: Space scoop, news for children. 

Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.

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This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.

One Comet, Twin Asteroids, or Both?

A comet has been discovered that is also two asteroids!

Asteroid 288P is located way out in the asteroid belt between Mars and Jupiter, making it a little difficult to observe.

However, in September 2016, it traveled a bit closer to Earth, allowing us to finally get a detailed look with the Hubble Space Telescope. It was also a bit closer to the Sun in its orbit at the same time.

288P is part of a family of at least 11 asteroids that formed from a parent object that was about 10km in diameter. That object was broken up in a collision about 7.5 million years ago.

It was a big surprise to discover that 288P is not one, but two asteroids orbiting each other at a distance of about 100 kilometers! This orbital distance between the two halves is very odd. Usually binary asteroids are much closer than that.

Being in two parts, the asteroid couple is a so-called “binary asteroid”, which means they are siblings that orbit each other. Actually, because these two are almost the same size and mass, they really are like twins!

While binary asteroids are common, 288P is the first to show
– a wide separation,
– high orbital eccentricity,
– similarly sized components and
– mass-loss activity.
All of this is suggestive of a different origin for 288P than the other binary asteroids.

The fact that they’re orbiting each other means that the multinational team of astronomers can do a simple calculation of their masses using Kepler’s third law.

Being able to measure how massive these asteroids are is an impressive accomplishment. On top of that, because the object’s orbit had it closer than normal to the Sun, the astronomers found that these are the first asteroid twins spotted acting somewhat like a comet!

288P had a coma and tail like a comet!

There are ices present on it that are sublimating or turning directly into vapor without passing through a liquid phase. This vapor is forming that coma and tail.

This makes 288P the first binary asteroid that doubles as a comet, making it what we call a main belt comet, or MBC, as it’s in the main belt of asteroids.

The team leader, Dr. Jessica Agarwal, of the Max Planck Institute, thinks that the observed activity of 288P shows us how it formed. After the collision 7.5 million years ago it existed as an elongated single object that had a rapid rotation rate.

The centrifugal forces from its rotation caused it to break apart about 5,000 years ago. The two parts have been moving farther apart ever since by torques caused by the sublimation events when it was closer to the Sun.

There are over a dozen MBCs that have been discovered, and 288P is the first that’s a binary object.

Hey, Here’s A Cool Fact:
Current research suggests that water was not brought to Earth by comets, as had been long thought, but by icy asteroids instead. The deuterium-to-hydrogen ratio in our oceans is different from the ratio seen in regular comets.

They have more deuterium than our oceans, so they aren’t the source of our oceans. As you might guess, more research is needed to determine the deuterium/hydrogen ration of icy asteroids. Then we’ll know the source of our planet’s water and we can drink a toast to it’s, uh, health!

Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org.  This year we will celebrate more discoveries and stories from the universe. Join us and share your story. Until tomorrow! Goodbye!

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