PDA

View Full Version : Gliese 581 d



AMCrenshaw
02-04-2009, 08:19 AM
Hey guys. This might be old hat, but is anyone excited about this exoplanet?

http://en.wikipedia.org/wiki/Gliese_581_d

I would appreciate speculations as to the likelihood of life there -- or even signs in that direction. Just curious. Always like to think about these things.

AMC

Smiling Ted
02-04-2009, 11:32 AM
There might be life, but at 44 times the mass of Earth, the odds of large creatures with skeletal structures seems kind of slim.

Nivarion
02-04-2009, 07:35 PM
well, it could happen...

one thing i have always wondered, how do they calcualte the mass of one planet that they can't see? especially since there will be other planets out there?

but I'm sure it would have moons, that may have life.

Pthom
02-04-2009, 10:23 PM
I recall that Carl Sagan envisioned a life form that might exist on Jupiter, as being a sort of a gas-filled jellyfish-like thing, floating in the upper atmosphere.

And as jellyfish apparently are imortal (http://absolutewrite.com/forums/showthread.php?t=129611). . .

kuwisdelu
02-04-2009, 10:53 PM
one thing i have always wondered, how do they calcualte the mass of one planet that they can't see? especially since there will be other planets out there?

From observing its motion, we can use gravity to calculate its mass. With all the variables, it's a complicated process, for sure. But that's why we have computers.

Dommo
02-05-2009, 05:31 AM
Until we've got better detection equipment that might be able to pick up signs of methane or other organic chemicals on that planet, I wouldn't get my hopes up.

Nivarion
02-05-2009, 09:50 AM
yea, yea i know we measure the mass of the planet, but how do we really really know we aren't measuring the mass of everything in orbit around the star.

it is still cool that someone noticed the wiggle effect from the orbits.

kuwisdelu
02-05-2009, 11:30 PM
Until we've got better detection equipment that might be able to pick up signs of methane or other organic chemicals on that planet, I wouldn't get my hopes up.

We can get a pretty good idea of what kinds of gases exist by their spectral absorption and emission lines.


yea, yea i know we measure the mass of the planet, but how do we really really know we aren't measuring the mass of everything in orbit around the star.

it is still cool that someone noticed the wiggle effect from the orbits.

Well, we know how gravity works. It's a pretty complicated set of equations when you're dealing with multiple bodies, but we can tell pretty well where various gravitational effects are coming from.

Dommo
02-06-2009, 05:00 AM
It's the resolution kuwi. I'm not saying we can't, I'm just saying what we've currently got isn't sensitive enough. It's like trying to see a bacteria with a magnifying glass, when what we need is a microscope.

Nivarion
02-06-2009, 06:29 AM
they are building a new telescope that has 7 mirrors that are 20 feet across. (i think hubble only has 1 mirror of 20 feet.) that they will have to build in pieces.

im thinking that that may cut it.

my source is the discovery channel, a little hard to give links too.

TMA-1
02-06-2009, 03:17 PM
Until we've got better detection equipment that might be able to pick up signs of methane or other organic chemicals on that planet, I wouldn't get my hopes up.
Methane, water and carbondioxide have all been found on exoplanets, but the big thing will be when we find oxygen or ozone.

MelancholyMan
02-06-2009, 06:32 PM
Been there. Nothing but outlet malls, gas stations, and a toxic waste dump.

GeorgeK
02-17-2009, 05:10 AM
From observing its motion, we can use gravity to calculate its mass. With all the variables, it's a complicated process, for sure. But that's why we have computers.

Almost all of what I think I know on this could fit on a tv show, however after watching one such show I wondered if they could tell the difference between one large solid planet vs a gas giant being orbitted by a "moon" that was mostly metal?

lpetrich
03-16-2009, 05:41 AM
Almost all of what I think I know on this could fit on a tv show, however after watching one such show I wondered if they could tell the difference between one large solid planet vs a gas giant being orbitted by a "moon" that was mostly metal?
I'd like to find that out myself. Seems to me like someone's speculation about what some hot Jupiter's satellites could be like.

In any case, the physics behind these planet observations is rather simple. The star pulls on a planet, keeping it in its orbit. But the planet also pulls on the star, and makes it move a little bit.

As the planet moves the star, it may go back and forth along our line of sight, giving it a radial velocity that we can measure with a spectroscope.

But to be easy to detect in this fashion, a planet must have a large radial velocity, meaning that it must be (1) large and (2) close to its star, which is why we've seen mostly "hot Jupiters" so far.

Dale Emery
03-16-2009, 06:10 AM
yea, yea i know we measure the mass of the planet, but how do we really really know we aren't measuring the mass of everything in orbit around the star.

Objects orbiting at different distances have different orbital periods, and therefore induce wobbles with different periods on the star (and on each other).

Objects of differing mass exert different force on the star, and therefore induce wobbles of different size.

So if the star's wobble has a regular size and period, you know the wobble is primarily induced by a single dominant object.

Dale

mario_c
04-24-2009, 09:22 AM
Been there. Nothing but outlet malls, gas stations, and a toxic waste dump.You're probably thinking of Secaucus, NJ. :ROFL: Oh stop groaning, I'm from Joisey. So pick your favorite urban pit and have fun with the joke....