[ Sandy/NASAChatHost - 0 - 06:01:01 ]
Hello and welcome to another NASA Space Scientists Online QuestChat! Today's special guest will be Physics Researcher Perry Gerakines from NASA's Goddard Space Flight Center in Greenbelt, Maryland. Be sure to read Perry's bio BEFORE coming to the chat-- http://quest.arc.nasa.gov/sso/team/gerakines.html -- Perry will be here and ready to take your questions at 11 am Pacific (2 pm Eastern). "See you" then!

[ Sandy/NASAChatHost - 6 - 11:11:20 ]
Welcome everyone! Perry Gerakines is here and will start answering your questions...

[ PerryGerakines/PhysicsResearch - 7 - 11:11:39 ]
RE: [SusanDePrima] Hi, I am a second greade teacher and I'm here with my students. We are learning about meteors and astronauts. How big ias the largest comet that you have ever seen?
Hi everyone. I guess I should get started, then.. I've probably only seen the same comets as you have: Hyakutake and Hale-Bopp a few years ago. They were many kilometers across (the size of a small town), and they were travelling so fast that we only had a few weeks to look at them.

[ Sandy/NASAChatHost - 8 - 11:12:32 ]
RE: [Stephanie/Edmonton] Hi Sandy!
Hello Stephanie! Very glad to "see you" :-)

[ PerryGerakines/PhysicsResearch - 10 - 11:16:28 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Is the lense of the telescopes you usually use 16 inches wide? How far can you see? We are from san jose, Ca.
I've used many telescopes, from my personal one at home with a 3.5-inch diameter to ones at Mauna Kea observatory which were about 10-feet wide!

[ PerryGerakines/PhysicsResearch - 11 - 11:18:31 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Is the lense of the telescopes you usually use 16 inches wide? How far can you see? We are from san jose, Ca.
The answer to your second question is harder, since telescopes do not actually allow us to see farther away, but to see fainter things (which are usually farther away, hence the confusion). A 16-inch telescope will let you see things about a million times fainter than you can see with only your eye. (In astronomy lingo, we say "6 magnitudes fainter").

[ PerryGerakines/PhysicsResearch - 13 - 11:25:05 ]
RE: [PerryGerakines/PhysicsResearch] Hi everyone. I guess I should get started, then.. I've probably only seen the same comets as you have: Hyakutake and Hale-Bopp a few years ago. They were many kilometers across (the size of a small town), and they were travelling so fast that we only had a few weeks to look at them.
I should probably add that a comet's speed is always changing. In the outer Solar System, they travel very slowly. Then they fall in towards the Sun, always picking up speed, until they turn around and start going away from the Sun, always slowing down.

[ PerryGerakines/PhysicsResearch - 15 - 11:27:26 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] What is the ice like in space? Does it differ from location to location?
Ice changes everywhere you go. In comets, we think ices are mixtures of dust, water and things like methane or carbon monoxide. They are also very cold. On Jupiter's moon Europa, they are also mostly water, but mixed with things like sulfuric acid and carbon dioxide. Underneath, there may even be an ocean!

[ PerryGerakines/PhysicsResearch - 16 - 11:28:49 ]
RE: [Jared-Stephanie/Edmonton] Have you discovered any comets?
No, unfortunately, I don't get to the telescope as often as I would like. Even then, discovering a comet is not so easy...

[ PerryGerakines/PhysicsResearch - 18 - 11:32:00 ]
RE: [PerryGerakines/PhysicsResearch] No, unfortunately, I don't get to the telescope as often as I would like. Even then, discovering a comet is not so easy...
Many comets are discovered at "star parties". Large groups of amateur astronomers who get together just to watch the sky all night. One such comet was Comet Schoemaker-Levy! (the one that hit Jupiter)

[ PerryGerakines/PhysicsResearch - 19 - 11:34:10 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Why do comets look like fire balls?
When comets are close enough to the Sun that we can see them, they are actually evaporating very quickly! What we are seeing are all the gases coming off of the ices and forming a cloud around the comet itself and the comet's tail. (To me, they always looked like cotton swabs...)

[ PerryGerakines/PhysicsResearch - 21 - 11:36:16 ]
RE: [PerryGerakines/PhysicsResearch] Many comets are discovered at "star parties". Large groups of amateur astronomers who get together just to watch the sky all night. One such comet was Comet Schoemaker-Levy! (the one that hit Jupiter)
also, most comets are discovered while they are still very far from the Sun, when they are quite faint. It takes some careful observing to even see them at all!

[ PerryGerakines/PhysicsResearch - 23 - 11:38:19 ]
RE: [Stephanie/Edmonton] What is the principal composition of comets?
It is thought that comets are like "dirty snowballs" of mostly water and dust collected from the cloud from which the planets were formed. No direct samples of cometary ice have ever been taken (yet!) but we are pretty sure from watching them evaporate as they approach the Sun.

[ PerryGerakines/PhysicsResearch - 25 - 11:39:52 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Has your daughter ever seen a shooting star...meteorite?
I don't think she has... She's just starting to appreciate seeing the stars at night, though.

[ PerryGerakines/PhysicsResearch - 26 - 11:41:24 ]
RE: [Stephanie/Edmonton] Is there any chemical reaction (give an equation) that happens as the gases from the comet come in contact with the solar wind?
I think I'll leave the chemical equations for another time, but one of the effects of the Solar wind is to ionize the gases that come from the comet.

[ PerryGerakines/PhysicsResearch - 28 - 11:47:11 ]
RE: [PerryGerakines/PhysicsResearch] I think I'll leave the chemical equations for another time, but one of the effects of the Solar wind is to ionize the gases that come from the comet.
Most of the gases observed either came directly out of the comet's ice (called "parent" species), or were formed by reactions of parent species (called "daughter" species). As an example, water is a parent species, but when water breaks up (H2O -> H + OH), we observe it's parts (like OH) as duaght species.

[ PerryGerakines/PhysicsResearch - 29 - 11:49:19 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Is there any certain month that more meteorites are viewed?
Meteor showers occur at special times in the year, like the Perseids on August 11th, the Leonids on Nov. 11th, because that's when the Earth moves through a trail of debris left behind by comets.

[ PerryGerakines/PhysicsResearch - 33 - 11:51:19 ]
RE: [PerryGerakines/PhysicsResearch] Meteor showers occur at special times in the year, like the Perseids on August 11th, the Leonids on Nov. 11th, because that's when the Earth moves through a trail of debris left behind by comets.
Also, the Geminids are in December. I don't think there is any "special" reason why they occur at certain times of the year. Each meteor shower is also different every year! I believe this past year's Leonid shower was very spectacular.

[ PerryGerakines/PhysicsResearch - 34 - 11:53:01 ]
RE: [Sandy/NASAChatHost] Stacy from Throckmorton's 4th graders asks: At what age did you want to become a scientist? How many people work with you and study stars?
I don't think I realized I wanted to be a scientist until middle school or high school. I've wanted to be a lot of different things, like a musician or an actor...

[ Sandy/NASAChatHost - 35 - 11:53:17 ]
EVERYONE: There are about 10 minutes left in our chat with Perry today. please let us know how we did by answering a very short survey at-- http://quest.arc.nasa.gov/qchats/qchat-surveys

[ PerryGerakines/PhysicsResearch - 38 - 11:54:36 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Which planets have the largest moons and the greatest amounts of water?
Jupiter, Saturn, Uranus and Neptune all have about 10-20 moons each. As far as water goes, Europa may be the only one with liquid water anywhere. Most other moons are so cold that all the water is frozen solid.

[ Sandy/NASAChatHost - 39 - 11:55:23 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Good bye and thank you for sharing. Mrs. DePrima's Second Graders
Thank you so much for coming today and for your excellent questions! We hope you can join us again next week! Please be sure to fill out our short survey, mentioned above. Thanks!

[ PerryGerakines/PhysicsResearch - 40 - 11:55:48 ]
RE: [Sandy/NASAChatHost] Maranda from Throckmorton's 4th graders asks: What is your favorite thing about your job?
My very favorite thing about my job is that I get to wonder "Why?" and get paid to try to come up with the answer...

[ PerryGerakines/PhysicsResearch - 41 - 11:56:26 ]
RE: [SusanDePrima-SusanDeprima/silveroakelementary] Good bye and thank you for sharing. Mrs. DePrima's Second Graders
Thanks for coming and asking good questions!

[ PerryGerakines/PhysicsResearch - 43 - 11:57:00 ]
RE: [Sandy/NASAChatHost] Charon from Throckmorton's 4th graders asks: Did you want to be anything else besides a scientist? Do you want to go into space, closer to the stars?
I've always thought I'd make a pretty good astronaut...

[ PerryGerakines/PhysicsResearch - 46 - 11:58:39 ]
RE: [Sandy/NASAChatHost] Lamar from Throckmorton's 4th graders asks: What do you like the most about science?
Science is logical. It doesn't have prejudices. Science is meant to answer questions and explain the wonders of our universe....

[ PerryGerakines/PhysicsResearch - 48 - 11:59:48 ]
RE: [Sandy/NASAChatHost] Blair from Throckmorton's 4th graders asks: Why were you so interested in space? Does your work involve tons of math, or just a little? What is your favorite space movie?
I suppose I read too much Science Fiction as a teenager... yes, lots of math, but I like that! :^)

[ PerryGerakines/PhysicsResearch - 49 - 12:01:08 ]
RE: [Sandy/NASAChatHost] Hope from Throckmorton's 4th graders asks: Do you get nervous when you have to write research proposals? (We just took a writing test that will decide if we pass our grade.)
Yes I get very nervous! It just takes time to build up experience, I think. I'm still quite new to the whole process.

[ PerryGerakines/PhysicsResearch - 50 - 12:02:13 ]
RE: [Sandy/NASAChatHost] Desmond from Throckmorton's 4th graders asks: Do you ever get confused by your work? Thanks for getting these in for the webchat!
I must get confused by my work almost every day! It's one of the things I find most exciting about it.

[ PerryGerakines/PhysicsResearch - 51 - 12:04:17 ]
RE: [Sandy/NASAChatHost] Blair from Throckmorton's 4th graders asks: Why were you so interested in space? Does your work involve tons of math, or just a little? What is your favorite space movie?
My favorite space movie is probably 2001: A Space Odyssey.

[ Sandy/NASAChatHost - 52 - 12:04:41 ]
Ok everyone, it's time to let Perry get back to his "other" work! Thanks to all of you for the great questions! Today's chat with Perry will be archived later today. Be sure to fill out the short survey for us. We hope you can join us again next week for a Mars chat with Ken Edgett.