Podcaster: Richard Drumm
Title: Space Scoop: What Do You Call A Comet Without A Tail?
Organization: 365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1610/
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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Transcript:
This is 365 Days of Astronomy. 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.
Today’s story is: What Do You Call A Comet Without A Tail?
Whether it’s a loaf of bread or a space rock, the best way to preserve anything is in a freezer.
Our Solar System has its own deep freeze compartment: the Oort Cloud. The Oort Cloud is a gigantic group of comets beyond Neptune’s orbit. It is thought that it is the leftovers from the original protoplanetary disc that formed the planets in our solar system.
Leftovers. Yet another thing you might find in the deep freeze…
It’s named for Dutch astronomer Jan Oort who analyzed comet orbits and saw that there were a large percentage of them whose farthest part of their orbit, called the aphelion, lies at 20,000 AU. This suggested to him that there was something like a reservoir of comets out at that distance.
The Oort Cloud is a quasi-theoretical cloud of icy bodies. Quasi-theoretical because we’ve never taken a photograph of it but we have evidence that it is there. It appears that it exists in 2 regions, the inner and the outer Oort clouds.
The inner cloud, also called the Hills Cloud after American astronomer Jack Hills, appears to be doughnut-shaped and is from 2,000 to 20,000 AU from the Sun roughly in the plane of the ecliptic, the plane of the orbits of the planets.
The outer cloud lies from 20,000 to 50,000 AU and is spherical instead of ring shaped. The orbits of comets out here have likely been circularized by tidal forces from nearby stars early on in the life of our Sun and by tides from the rest of the galaxy.
These orbits, being circular, don’t bring the comets into the inner solar system. Instead, comets there are quite content to stay put in the deep freeze of the outer Oort cloud.
Comets that come from here, like Comet Hale-Bopp, can come from any direction.
These long period comets are likely from the Oort Cloud and pay us in the inner solar system a visit when their stable orbits get perturbed by a passing star or interaction with other objects it meets way out there.
Comets that return to the Sun every 200 years or less are called “short period” comets. Those with periods over 200 years are the long period comets.
The short period comets were once thought to originate in the Kuiper belt but now we suspect that they come from the so-called “scattered disk”. The Kuiper belt extends from Neptune’s orbit, 30 AU out to 50 AU, and is home to Pluto, Haumea and Makemake, 3 dwarf planets.
The Kuiper belt orbits are stable, so not many comets come from there, but the scattered disk on the other hand produces many.
The scattered disc extends from 30 AU like the Kuiper belt, out to 150 AU from the Sun. The dwarf planet Eris is a scattered disc object.
Because the orbits here are more elliptical than Kuiper belt orbits and they come close to Neptune, they can get disturbed by Neptune and get hurled outward into the Oort cloud or thrown inward toward the Sun.
But let’s turn our attention back out to the Oort cloud and get to talking about this comet with no tail!
It’s so far from the Sun’s heat, that temperatures in the Oort Cloud can drop to minus 250°C and lower! A very deep freeze indeed!
This cold, dark place is ideal for preserving ancient relics from the earliest days of our Solar System — including the Manx Comet, also called C/2014 S3 (PANSTARRS).
Despite its name, it is believed that the Manx Comet is actually an asteroid. While comets are icy bodies, asteroids are chunks of rock left over from the birth of our Solar System’s rocky planets: Mercury, Venus, Earth and Mars.
The Manx Comet was born close to the Sun 4.5 billion years ago, at the same time as the Earth. Soon afterwards, this unlucky asteroid was flung into the shadows at the edge of the Solar System.
Now, billions of years later, it was discovered by chance at a little over 2AU from the Sun as it headed back towards the warmth of the Sun.
It was producing a tiny bit of comet-like activity, with water ice sublimating directly from solid ice to water vapor, but at a rate that is one millionth as strong as is typical for long period comets. So there IS a little fuzziness in the image of it in today’s album artwork. But only a little.
Recently, at least on cosmic time scales, the Manx Comet was nudged out of the Oort Cloud on to a path that brings it closer to the Sun. In its new orbit, the Manx Comet will fly past our part of the Solar System every 860 years!
Our Solar System contains thousands of asteroids, all of them have been baked by spending billions of years near the Sun.
Except the Manx Comet.
The Manx Comet has been preserved in the Oort Cloud — the best deep freeze our Solar System has to offer!
This is the first rocky asteroid ever observed coming from the Oort Cloud. It’s a perfect fossil from when the Solar System was very young and could reveal exciting new information about how our home in the Universe came to be.
Hey, Here’s A Cool Fact:
When comets travel near the Earth, some of their ices evaporate because of the heat of the Sun, creating a wonderful “tail” as it travels across the night sky.
The Manx Comet isn’t made of the same material as other comets, so it doesn’t have a tail. This is why it was named after the famous, tailless “Manx” cat.
End of podcast:
365 Days of Astronomy
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