Earth's Bigger Cousin Detected

[MarkN]

From CNN (http://www.cnn.com/2005/TECH/space/06/13/extrasolar.planet/index.html).

Very interesting, but my not being a scientist I'm totally flummoxed, yet amazed, at how astronomers can more or less accurately calculate the distances and sizes of stars or planets and their orbits that we could never visit, or else at least not for centuries from now.

[Chip]

mis labeled. Gives the wrong impression when it is called earth2.

[Ifitmovesnukeit]

Originally posted by MarkN:
Very interesting, but my not being a scientist I'm totally flummoxed, yet amazed, at how astronomers can more or less accurately calculate the distances and sizes of stars or planets and their orbits that we could never visit, or else at least not for centuries from now. As a budding astrophysicist, I can help to answer the distance issue, but I don't know how much my info was dumbed down at the level I was taught it. av_wink.gif

Basically, due to the Earth's movement relative to stars, it is observed that these stars seem to "move" a small amount over a six-month period. We can measure the angle of this movement (known as the parallax angle). Because every six months we are on opposite sides of the Sun, we can use the Earth's distance from the Sun in our calculation, you may know that this is given as one astronomical unit (AU). Now we have an angle, and a distance. A right-angled triangle is formed, with the Earth, the Sun, and the star in question as the 'points' of the triangle, and 1 AU as the "opposite" side of the triangle. It is now possible to use simple trigonometry to work out the distance of the star given as d = 1AU/tan(p).

Those who know their trigonometry well will recognise that that is simply a rearrangement of tan theta = opposite/adjacent.

I'm fully aware that that might sound a little complex, so I've hunted down this diagram to clarify things. av_wink.gif

http://burro.astr.cwru.edu/Academics/Astr221/Light/parallax.gif

At the risk of sounding patronising, I'll point out from that poorly-labelled diagram that the two blue dots are the Earth at different times of the year, and the pink dot is the Sun. The line going from the middle of the Sun to the star is supposed to be completely horizontal.

NB that this method only works for stars that are 'relatively' close- the parallax angle is already tiny for close stars, hugely exaggerated for the purposes of the above diagram- much further away and the angle is too small to measure.

Hope that clarified things a little! av_smile.gif

[Virus002]

Ok, now i have a headache from what you just said. graemlins/av_barf.gif

[ToddGreenway]

cmom thats really easy...i learned that in high school physics2

[enfestid]

Interesting stuff av_smile.gif Too bad it's so hot... maybe there's still some form of life, though.

[OmegaBob]

I agree with Chip. At first, I thought it was a reference to <evil> Spielberg's TV series.

Earth 2 (http://www.tv.com/earth-2/show/339/summary.html&full_summary=1)

[MarkN]

Thanks, Ifitmovesnukeit. Not how well I understood that overall but I did understand a bit of it. However, when you're talking trig, calculus and algebra then you're getting waaay over my head cuz simple math's the best that I can do and then only up to a certain point. At least I know it well enough to be a cashier for years cuz it's so easy, especially knowing how to make change when someone gives ya a few extra coins to make an even dollar or coinage amount. Seems too many kids these days can't make change without looking at a diagram on the keyboard or something. graemlins/av_cheesygrin.gif

Here's a question about planet size, though. As far as our science knows, does a planet's size determine the strength of its gravity? Jupiter's I dunno how many times bigger than piddly little ol' Earth but its gravity is so exponentially greater than ours that I wonder if planet size is a factor in gravity, or could a planet the size of Pluto have a gravity about equal to Jupiter's?

[Felix]

More mass = more gravitational pull.

[Ifitmovesnukeit]

Mass is indeed the key factor in gravity. A planet consisting mainly of Iron will have more of a gravitational pull than a planet of a similar size consisting mainly of Hydrogen. Generally speaking, however, larger planets tend to have a more powerful gravitational pull than smaller ones.

[One-Winged Angel]

Which is the reason why Jupiter doesn't have an exponentially greater gravitational pull than earth. It is made up of mostly gas, which doesn't contain a lot of mass in and of itself.

Heck, you have a gravitational pull of your own. You just never notice it because your mass isn't that much.

[Rick_browne]

that cant be right, then fat people would have no problems attracting chicks av_biggrin.gif

[CannibalBob]

Originally posted by Felix:
More mass = more gravitational pull. F=GMm/r²

Anyway they figure a lot of stuff out through light. Photons travel through space, as a wave (and a particle). Now due to the "Doppler effect", waves are more condensed if something is moving towards you. So if something is moving towards earth, the wavelengths are higher (ie. green, purple, etc.) if it's moving away it's red.

So they can just gather the light from something moving (ie. a planet orbitting) and figure out how it's moving, the orbit, etc.


Now what amazes me is not how they figure this stuff out, but that we GET this info in the first place. These planets are so mind bogglingly far away that it's difficult to comtemplate. It just makes me realize how little we (humans) know!

[One-Winged Angel]

Well, you also don't know how long it took for us to get that information. Years? Decades? Centuries? Even longer?