Anyone here big on Astronomy?

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That's how they discovered the first extra-solar planets. Many are likely brown dwarves, or Jupiter-like megaplanets. Over 150 discovered to date.

They say the mark of good vision in Indian tribes (American Aborigines, for y'all overseas... was to be able to see the double star in the Big (I think) dipper.

Also, I didn't know until a month ago that Mercury's orbit increases and decreases in 3 million-year intervals.

It was actually the Pleiades that was used for this (if you could see 7 separate stars, your vision was good). Your mix-up could've been from the origin myth, where seven sisters/maidens are trying to escape a giant bear, so they climbed up a large rock, the bear scratches away at its sides (creating Devils Tower), so they escape into the heavens, becoming the Pleiades. I'm pretty sure that the bear then follows and becomes Ursa Major (the big dipper), but I could be wrong on this last bit.

Firstly, you are correct with the mythology. I have been to Devil's Tower (It's amazing!), and they shared this legend with us. Also, I can see the double stars in Ursa, but it's not as clear as with binoculars. Look at the second to the last star in the 'handle' of the Big Dipper. A telescope actually is of little use here (at least mine is) as they magnify the space so much, you cannot see both stars at once. Binoculars, though, show both stars clearly.
Also, on a side note, they are NOT binary stars. In reality, they are 3ly apart, but are loosely bound by a gravity well (theorized to be a black hole) between them.

-TheBookkeeper

So axial wobble (I was unfamiliar with this exact term) in this case is being measured by (edit:astro)metric techniques.

TheBookkeeper, you mention the figure of 0.002 as a percentage at first, then in degrees. Which is it?

Also, I looked up this system and 47 ursae Majoris is a G-type star like our own, but older. It is way beyond the planet-forming stage; its planet-forming accretion disk would have been processed billions of years ago. How could a new planet have formed recently?

Last edited by outlier on 03 Jun 2009, 7:27 pm, edited 1 time in total.

Firstly, axial wobble is measured in degrees. If I wrote percentages, I apologize. I was likely thinking of something else.

As far as the planet may/may not be concerned, there are other ways planets can start life. Pluto, for instance, was a rogue celestial body that was trapped by Neptune. Eris (a large, round asteroid in our Asteroid Belt) used to be a planet (until the whole Pluto thing) and was formed by large asteroids lumping together under pressure from Jupiter's orbit. Accretion discs are the MAIN way planets form.

And I thought 47 Ursa was a K-Type star, not a G-Type, but I could be wrong. May I ask where you heard that? I'm not discrediting you, I just want to know. If I'm wrong I'll happily admit it - I love being wrong because it means I can learn new things.

-TB

I got the G-type star information from a couple of websites, one of which was this:

http://www.astro.illinois.edu/~jkaler/sow/47uma.html

Where did you obtain the 0.002 degree wobble information? I cannot find the information and you've piqued my curiosity.


EDIT:

OK, I think the terms are being confused here. I don't think axial wobble is the correct term, which is why I didn't recognise it in this context. The bodies orbit about the centre of mass of the system; using the word axial seems very inaccurate.

Eris is not part of the asteroid belt, but way beyond in the Kuiper belt. It would not have formed under the influence of Jupiter. Besides, it is probably as old as the solar system.

It takes thousands or millions of years to form a planet, even a small one, they don't just form within a few short days or years.

Perhaps it was Ceres that formed in the Asteroid belt. I know there's one there, I'm just full of bang ups today, aren't I? I'm usually at the top of my game here.

As far as the .002 wobble, that was done with my telescope and my astronomy teacher. He and I watched 47UMA until he told me what the wobble was. And I know it takes thousands/millions of years to form a planet, I'm just saying that the LIGHT is just reaching us NOW because of the time delay in Light Years.

-TB

I know how you feel. I'm experiencing similar.



That sounds fun! What equipment is needed to observe that? I assume a CCD and some perseverance.
Your astronomy teacher sounds cool.



Oh, you gave the impression you thought a planet might have formed recently.