Freethought & Rationalism Archive

JaeIsGod · 07-12-2003, 02:17 AM

So I was watching the news the other day and they said there a new planet had been discovered and that it was I believe 13 billion years(though not sure) old. Now I dont know much about all that stuff , so my question is how did they date that planet?

Lobstrosity · 07-12-2003, 02:22 AM

I assume you date the star about which it orbits and go under the assumption that the planet formed from the same gas cloud that formed the star.

JaeIsGod · 07-12-2003, 03:21 AM

I see , how do you date a star then? Im a science n00b =]

Coragyps · 07-12-2003, 06:40 AM

Stars are dated, in an oversimplified explanation, by measuring their mass and the time at which they use up all their hydrogen and start "burning" helium instead. The first quantity can be measured accurately by computing orbits of double stars, and the second by measuring the spectra of the star's light. You need a cluster of stars to get good numbers, 'cause there are statistical arguments involved - globular clusters like M$ are especially good, as they have LOTS of stars to pick from.
http://map.gsfc.nasa.gov/m_uni.html has a pretty good intro to this, with some of the difficulties mentioned, too.

Shadowy Man · 07-12-2003, 06:45 AM

In this case, the planet was found around a star in a globular cluster (M4). The age of a globular cluster can be determined by looking at the evolutionary states of the different stars.

While stars are in their "normal" phase, burning hydrogen into helium, there is a distinct relationship between the mass of the star and its luminosity and temperature. If you plot the luminosity and temperature of stars in a cluster (you know that all the stars are at the same distance so you don't need to worry about the dimming of the stars at different distances throwing off your luminosity measurement) you see that the different mass stars line up in what is called the "Main Sequence".

After a certain amount of time, the stars move on to the next evolutionary phase, and leave the main sequence. The more massive the star is, the earlier it leaves the main sequence. So, if you look at this plot (called an Hertzsprung-Russell Diagram) you can see the highest mass star that is still on the main sequence. This tells you the age of the cluster, if you know how long it takes for a given mass star to leave the main sequence.

Does this help?

If you want more information about these recent planet (which was actually discovered 10 years ago) go to this page:

Hubblesite info on the oldest planet

JaeIsGod · 07-12-2003, 08:04 AM

Ah , yes , I think I understand it now.

Thanks =]

Azathoth · 07-12-2003, 10:57 AM

A movie's good,maybe a walk in the country.And,if you're asked whether they look fat,by all means,say no.

agnawstick · 07-12-2003, 11:16 AM

Well, if you want to date a planet, I am sure that flowers might help. Also, think up a good opening line. Your atmosphere smells like a Class B Quasar on a trip around a new nebulus or something.

GunnerJ · 07-12-2003, 11:26 AM

GOD TWO PEOPLE CAME UP WITH THE SAME BAD JOKE (EXACTLY AT THE SAME TIME I DID) HATING ALL OF YOU RIGHT NOW.

ALSO BRING CHOCOLATES HURF EL OH EL

Nom · 07-12-2003, 11:51 AM

Quote:

Originally posted by agnawstick
Well, if you want to date a planet, I am sure that flowers might help. Also, think up a good opening line. Your atmosphere smells like a Class B Quasar on a trip around a new nebulus or something.

"Hey, baby. Nice moons. Wanna go for a ride in my new galaxy?"

07-12-2003, 02:17 AM	#1
JaeIsGod Senior Member Join Date: Jun 2003 Location: Netherlands Posts: 760	How do you date a planet? So I was watching the news the other day and they said there a new planet had been discovered and that it was I believe 13 billion years(though not sure) old. Now I dont know much about all that stuff , so my question is how did they date that planet?

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07-12-2003, 02:22 AM	#2
Lobstrosity Senior Member Join Date: Feb 2003 Location: San Diego, California Posts: 719	I assume you date the star about which it orbits and go under the assumption that the planet formed from the same gas cloud that formed the star.

07-12-2003, 03:21 AM	#3
JaeIsGod Senior Member Join Date: Jun 2003 Location: Netherlands Posts: 760	I see , how do you date a star then? Im a science n00b =]

07-12-2003, 06:40 AM	#4
Coragyps Veteran Join Date: Aug 2001 Location: Snyder,Texas,USA Posts: 4,411	Stars are dated, in an oversimplified explanation, by measuring their mass and the time at which they use up all their hydrogen and start "burning" helium instead. The first quantity can be measured accurately by computing orbits of double stars, and the second by measuring the spectra of the star's light. You need a cluster of stars to get good numbers, 'cause there are statistical arguments involved - globular clusters like M$ are especially good, as they have LOTS of stars to pick from. http://map.gsfc.nasa.gov/m_uni.html has a pretty good intro to this, with some of the difficulties mentioned, too.

07-12-2003, 06:45 AM	#5
Shadowy Man Veteran Member Join Date: Jun 2002 Location: A Shadowy Planet Posts: 7,585	In this case, the planet was found around a star in a globular cluster (M4). The age of a globular cluster can be determined by looking at the evolutionary states of the different stars. While stars are in their "normal" phase, burning hydrogen into helium, there is a distinct relationship between the mass of the star and its luminosity and temperature. If you plot the luminosity and temperature of stars in a cluster (you know that all the stars are at the same distance so you don't need to worry about the dimming of the stars at different distances throwing off your luminosity measurement) you see that the different mass stars line up in what is called the "Main Sequence". After a certain amount of time, the stars move on to the next evolutionary phase, and leave the main sequence. The more massive the star is, the earlier it leaves the main sequence. So, if you look at this plot (called an Hertzsprung-Russell Diagram) you can see the highest mass star that is still on the main sequence. This tells you the age of the cluster, if you know how long it takes for a given mass star to leave the main sequence. Does this help? If you want more information about these recent planet (which was actually discovered 10 years ago) go to this page: Hubblesite info on the oldest planet

07-12-2003, 08:04 AM	#6
JaeIsGod Senior Member Join Date: Jun 2003 Location: Netherlands Posts: 760	Ah , yes , I think I understand it now. Thanks =]

07-12-2003, 10:57 AM	#7
Azathoth Veteran Member Join Date: Nov 2002 Location: The centre of infinity Posts: 1,181	A movie's good,maybe a walk in the country.And,if you're asked whether they look fat,by all means,say no.

07-12-2003, 11:16 AM	#8
agnawstick Junior Member Join Date: Jun 2003 Location: arcadia California Posts: 65	Well, if you want to date a planet, I am sure that flowers might help. Also, think up a good opening line. Your atmosphere smells like a Class B Quasar on a trip around a new nebulus or something.

07-12-2003, 11:26 AM	#9
GunnerJ Banned Join Date: Sep 2001 Location: a place where i can list whatever location i want Posts: 4,871	GOD TWO PEOPLE CAME UP WITH THE SAME BAD JOKE (EXACTLY AT THE SAME TIME I DID) HATING ALL OF YOU RIGHT NOW. ALSO BRING CHOCOLATES HURF EL OH EL

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