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hullaballo
2001-Oct-30, 12:39 PM
I need some help please!!! /phpBB/images/smiles/icon_eek.gif I'm giving a talk for my daughter's 6th grade science class on space. We are going to be building a scale of the Solar System. Since there unit is supposed to be about space travel I wanted to add distances to stars.

What is the closest system that has extra solar planets, and what is the closest single (not part of a multiple star system) Sun like, star. I'm looking for close by candidits to travel to that would support life.

Thank you for your support!:D


<font size=-1>[ This Message was edited by: hullaballo on 2001-10-30 07:41 ]</font>

Russ
2001-Oct-30, 01:14 PM
On 2001-10-30 07:39, hullaballo wrote:
I need some help please!!! /phpBB/images/smiles/icon_eek.gif I'm giving a talk for my daughter's 6th grade science class on space. We are going to be building a scale of the Solar System. Since there unit is supposed to be about space travel I wanted to add distances to stars.

What is the closest system that has extra solar planets, and what is the closest single (not part of a multiple star system) Sun like, star. I'm looking for close by candidits to travel to that would support life.

Thank you for your support!:D


<font size=-1>[ This Message was edited by: hullaballo on 2001-10-30 07:41 ]</font>


I can't give you answers but can suggest you goto your search engine and search on Goeff Marcy, Berkley. Sorry, I didn't bookmark it, or I'd give your the URL. His site is quite informative.

I did a couple of talks to my sons 6th grade class. The first one, I took them to the football field, hung solar system object names on them and we made a human solar system map on a one hundred yard scale. We had great fun. At that scale, Prox. Cent. is about 435 miles away. The kids were staggered by that fact. It really put things in perspective for them.

The second talk, I took my telescope up and we looked a Sun spots until it clouded over. Again, great fun.

I hope I helped.

ToSeek
2001-Oct-30, 01:40 PM
On 2001-10-30 07:39, hullaballo wrote:
I need some help please!!! /phpBB/images/smiles/icon_eek.gif I'm giving a talk for my daughter's 6th grade science class on space. We are going to be building a scale of the Solar System. Since there unit is supposed to be about space travel I wanted to add distances to stars.

What is the closest system that has extra solar planets, and what is the closest single (not part of a multiple star system) Sun like, star. I'm looking for close by candidits to travel to that would support life.

Thank you for your support!:D


<font size=-1>[ This Message was edited by: hullaballo on 2001-10-30 07:41 ]</font>


Two Websites for starters (I did a Google search on "extrasolar planets"):

The Extrasolar Planets Encyclopedia:
http://www.obspm.fr/encycl/encycl.html
provides info on all the extrasolar planets found.

This article: http://physicsweb.org/article/world/14/1/7
indicates that the closest one is around Epsilon Eridani (10.7 ly away).

This is cool, by the way, because according to Star Trek lore E Eridani is the solar system of the planet Vulcan.

Bob S.
2001-Oct-30, 03:03 PM
Additional links:

Exoplanets - Introduction
http://www.generation.net/~mariob/astro/exoplan/intro-e.htm

Terrestrial Planet Finder
http://tpf.jpl.nasa.gov/index.html

Extrasolar Visions - An Extrasolar Planets Guide
http://www.jtwinc.com/Extrasolar/mainframes.html

From the last one, it seems Proxima Centauri may have an extra-solar planet (unless it's a brown dwarf companion).

Bob
2001-Oct-30, 05:54 PM
http://www.geocities.com/atlasoftheuniverse/12lys.html

Tau Ceti (11.9 ly) is the nearest sun-like star.

Phobos
2001-Nov-01, 12:02 PM
Remember that not all Extra-Solar planets seem to need a star. I seem to recall a number of the ones found so far were "drifters" without a homestar.

Jeff

hullaballo
2001-Nov-01, 12:31 PM
Thanks for all the responses. This is 3-4 year I've done this for this teacher, and I try to add a little something each year.

If you want to do this, (it is a real eye openner, for me too) a great web site is;
http://www.exploratorium.edu/ronh/solar_system/

You can create different scales for your model.

Rob Thorpe
2001-Nov-01, 04:04 PM
A question for those in the know. As long as I have been around occasionally (every couple of years or so) people have said that they have detected the presence of an extrasolar planet by the wobble it causes the star it orbits. Generally when this has happened they have been roundly trashed by every other astronomer soon afterwards. Recently however astronomers seem to have gained the ability to detect extrasolar planets and claim to have found several. What has changed? Do astronomers now have any more evidence than they did before? If so what is it?

ToSeek
2001-Nov-01, 04:59 PM
Having just finished Ken Croswell's excellent book on the subject ("Planet Quest"), I feel eminently qualified to respond.

First, there seems to have been a lot of wishful thinking in terms of detecting planets: too-quick announcing, optimistic interpretation of results. (Someone allegedly found a planet whose period was -- surprise, surprise! -- exactly the same as that of the earth. It took some investigation to realize that this was a systematic error, though it amazes me that this finding made it to publication at all.)

Second, some of the former debunkers are now among the finders. Geoff Marcy, who may be the world leader in the area, was once notorious for discrediting previous supposed discoveries.

Third, techniques and technology have improved. Rather than astrometry (seeing if the stars change position in the sky), Marcy & co. use Doppler shift detection, which is vastly harder to do but less susceptible to systematic errors. Interferometry is going to be coming into play in the near future, which should lead to a huge increase in planet discoveries.

Hope this helps.

The Bad Astronomer
2001-Nov-01, 05:50 PM
From the last one, it seems Proxima Centauri may have an extra-solar planet (unless it's a brown dwarf companion).


The results are still too marginal to say anything one way or another. Observing Proxima is very difficult, and even the extremely high-resolution Hubble guidance camera data is not good enough to know for sure.

ToSeek
2001-Nov-01, 07:01 PM
Upon reflection, I wonder how much science really does proceed two steps forward, one step back (like the planet discoveries). It's just more visible in this case because each proposed discovery makes headlines.

Perhaps the BA or some of the other pros here could comment.

Kaptain K
2001-Nov-02, 10:33 AM
The results are still too marginal to say anything one way or another. Observing Proxima is very difficult, and even the extremely high-resolution Hubble guidance camera data is not good enough to know for sure.
/phpBB/images/smiles/icon_confused.gif BA, could you please expand on this? I'm not sure I follow the reason for the difficulty. Is it because they are looking for an astrometric displacement rather than a doppler shift? /phpBB/images/smiles/icon_confused.gif

Ben Benoy
2001-Nov-02, 08:41 PM
On 2001-11-01 07:02, Phobos wrote:
Remember that not all Extra-Solar planets seem to need a star. I seem to recall a number of the ones found so far were "drifters" without a homestar.

Jeff


Ok, here it is, post number 51. Let's make it a good one...

How the heck can you detect an extra-solar planet which doesn't orbit a star? Planets are really small, in the grand scheme of things. And it's not like they have neon signs that say "look! Over here, I'm a planet!"

We can barely find Proxima Centauri, which is a small star, but still a star.

Also, if it's just wandering through the universe, why is it a planet and not just space junk. Which brings us again to the definition of planet, viz Pluto. I seem to recall that none of the definitions of planet which were offered up would classify a big old chunk of rock moseying through our corner of the galaxy as a planet.

Which brings us to the Death Star and small moons (Star Wars, taking over the world again). If it's not orbiting something, why would it be a moon? Likewise, if it's not grinding around a star, why would it be a planet?

Ok, that's enough. I love the repeated question... Ahh...

Ben

/phpBB/images/smiles/icon_biggrin.gif

The Bad Astronomer
2001-Nov-02, 08:54 PM
BA, could you please expand on this?

The Fine Guidance Sensors can give you extremely sensitive astrometry (position measurements) of a star. They were used repeatedly to look for a wobble in the motion of Proxima as it moves across the sky, and none was found. Oddly, I cannot seem to find any reference about this on the web, which makes me wonder if I am mis-remembering it (I know the Faint Object Spectrograph on Hubble was used and found interesting but not conclusive results). If/when I find more I'll post again.

David Hall
2001-Nov-03, 09:19 AM
On 2001-11-02 15:41, Ben Benoy wrote:

Ok, here it is, post number 51. Let's make it a good one...

How the heck can you detect an extra-solar planet which doesn't orbit a star? Planets are really small, in the grand scheme of things. And it's not like they have neon signs that say "look! Over here, I'm a planet!"

Ben


Well, this is my 51st post, so I'll try to give you a good answer. /phpBB/images/smiles/icon_smile.gif

Recently, several objects were detected by microlensing during observation of a globular cluster. I don't know how they determined it exactly, but these objects seem to be very small. Less massive than brown dwarfs for example.

Of course, microlensing is a non-repeatable observation, so it would be almost impossible to confirm any individual observation, but with so many events detected here, chances are good that we will be able to observe more of them.

Here's a link to it.

http://origins.jpl.nasa.gov/library/extrasolar/062701-a.html

The Bad Astronomer
2001-Nov-04, 12:10 AM
Oddly, I cannot seem to find any reference about this on the web


I found it: http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1994AAS...184.4304B&db_key=AST&high=38e0b7728728595 for those interested.

Kaptain K
2001-Nov-04, 12:50 PM
Okay. Says should be confirmed or refuted by fall of '94. It is now fall of '01. /phpBB/images/smiles/icon_confused.gif Was it?

GrapesOfWrath
2001-Nov-05, 12:06 AM
Ben, David

Shooting star fireworks for y'all (http://antwrp.gsfc.nasa.gov/apod/ap011101.html)

David Hall
2001-Nov-05, 08:46 AM
On 2001-11-04 19:06, GrapesOfWrath wrote:
Ben, David

Shooting star fireworks for y'all (http://antwrp.gsfc.nasa.gov/apod/ap011101.html)


Whoo! A galaxy-sized roman candle. I want one of those. /phpBB/images/smiles/icon_biggrin.gif Thanks!

Hmm, wonder what it would look like on a planet near (but not TOO near /phpBB/images/smiles/icon_smile.gif) something like that. Let's say about 50,000ly off to one side. It does say it's visible in optical wavelengths, but I wonder if it would it be visible to the naked eye from that distance or if it would it be too diffuse?

Bob S.
2001-Nov-05, 05:08 PM
How the heck can you detect an extra-solar planet which doesn't orbit a star? Planets are really small, in the grand scheme of things.

Heat. Free-range planets, especially those approaching brown-dwarf size, might put out enough of a thermal signature to be detectable against the cold background of space. Though they would have to be awfully close to be indistinguishable from simple data errors in any image from an infra-red telescope.



Also, if it's just wandering through the universe, why is it a planet and not just space junk.

Guessing:
Size and shape.
There are probably min and max size limits (too big to be oort cloud debris, too small to start fusion at its core).



Which brings us to the Death Star and small moons (Star Wars, taking over the world again). If it's not orbiting something, why would it be a moon?

Size and shape expectations. Conventionally, we visualize moons as spherical but asteroids as freshly dug potatoes. There are notable exceptions of course. From a distance, the Death Star appeared spherical with one heckuvva impact crater on the northern hemisphere AND it was found not far from Alderran (or its remains), so Luke might be forgiven for assuming it was a small moon of that planet.

David Hall
2001-Nov-05, 06:41 PM
Of course, whether a free floating body could be considered a planet depends on what definition of "planet" you are using. I think I can feel safe to say that most of the people here would not technically think of such a body as a planet, per the recent discussions we've had about it.

But, on another level, a more casual one, I don't think it's a crime to call such an object a planet. If it's roughly planet-sized and either rocky or gaseous then it could be called a planet as a sort of shorthand. I suppose such objects would more properly be termed "planetoids" or "free-floating planetary objects" or some such jargonese. But as long as we know what we're talking about we can use whatever is generally understood.

And of course this could also apply to moons, a-la the Star Wars thing. /phpBB/images/smiles/icon_smile.gif
_________________
David Hall
"Dave... my mind is going... I can feel it... I can feel it." (http://www.occn.zaq.ne.jp/cuaea503/whatnots/2001_feel_it.wav)

<font size=-1>(Edited a small mistake I made)</font>

<font size=-1>[ This Message was edited by: David Hall on 2001-11-05 13:52 ]</font>

Ben Benoy
2001-Nov-05, 11:05 PM
Thanks for the info about lensing. That's pretty cool. As far as the other poster, whose name I have conveniently forgotten ( /phpBB/images/smiles/icon_smile.gif ), I don't think that planets are hot enough that we could find them by "conventional" methods like IR radiation. Like I said, I thought that brown dwarves were nigh impossible to find. But anyway...

Ben Benoy

David Hall
2001-Nov-05, 11:44 PM
You're welcome. I found it really exciting myself. I never thought we could detect something so small and remote. And I agree about finding things by IR also. Unless it's pretty hot or very close, I doubt we'd be able to spot it at all.

But who knows, with the improving state of telescopes and interferonomers (am I spelling that right?), it's already become possible to detect things we never thought we'd see. Maybe future designs will be capable of such astounding feats.

Here's hoping! /phpBB/images/smiles/icon_biggrin.gif

Manchurian Taikonaut
2004-Mar-05, 09:19 AM
:D
some good stuff on the subject! Are we alone?

http://cfa-www.harvard.edu/afoe/they-are-everywhere.gif


http://news.bbc.co.uk/1/hi/sci/tech/1494864.stm


US scientists have found evidence that more than one planet is orbiting a star called 47 Ursae Majoris a mere 50 light years away from Earth.

The planet spotters said they are likely to find signs of even more planets as instruments become more sensitive and sky surveys become more comprehensive.

Now the scientists are pushing for funds to develop new telescopes that do nothing but look for planets orbiting nearby stars

http://planetquest.jpl.nasa.gov/SIM/sim_index.html

http://www.seds.org/billa/tnp/other.html
The planet around 70 Vir orbits the star in an eccentric, elongated orbit every 116 days and has a mass about nine times that of Jupiter. Using standard formulas that balance the sunlight absorbed and the heat radiated, Marcy and Butler calculated the temperature of the planet at about 85 degrees Celsius (185 degrees Fahrenheit), cool enough to permit water and complex organic molecules to exist. The star 70 Vir is nearly identical to the Sun, though several hundred degrees cooler and perhaps three billion years older.

http://www.obspm.fr/encycl/bibli.html
http://www.esa.int/export/esaSC/SEMYM6XO4HD_index_0.html
http://zenith.as.arizona.edu/~burrows/evolution3.html
55 Cancri b &amp; c planets, Gliese gas planet, child of aldebaran, Upsilon Andromedae b,
"hot-jupiter" in Delphinus, Bellerophon, Rho Coronae Borealis b, Goldilocks, iota Horologii b, , Tau Bootes system, 70 Virginis b, , PSR 1257 pulsar planet, Epsilon Eridani planet, 51 Pegasi b.

http://www.kepler.arc.nasa.gov/
http://www.esa.int/export/esaSC/SEMYZF9YFDD_index_0.html

Corot will be the first mission capable of detecting rocky planets, several times larger than Earth, around nearby stars (planets outside our Solar System are referred to as ‘exoplanets’). It consists of a 30-centimetre space telescope. It will be launched at the end of 2005.
http://origins.jpl.nasa.gov/library/exnps/ch04_0.html#4.1

http://www.obspm.fr/encycl/sites.html

For Darwin's objective to find and investigate Earth-like planets, it will work in nulling mode. The light reaching some of the telescopes will be very slightly delayed before it is combined. This will cause light from the central star to be 'cancelled out' in the resultant data. Light from planets, however, is not affected in this way and can be seen. If it were not for this 'nulling', the starlight would overwhelm the planet's feeble glow. In 'imaging' mode, none of the light is delayed and Darwin will work like a single large telescope, providing images of many types of celestial object in detail.

There are six telescope spacecraft. The telescopes themselves are a standard design, known as a Cassegrain, similar to that used in the Hubble Space Telescope. The overall dimensions of each telescope assembly will be 2.8 metres long by 1.7 metres wide.

http://vpl.ipac.caltech.edu/
http://planetquest1.jpl.nasa.gov/atlas/atlas_index.cfm
http://www.lpl.arizona.edu/
That new planet, "almost next door" (says the New York Times, Page One) is only 15 light years away from us. It orbits a star called GLEISE 876 M 4 V and it has two or three planet companions, probably also cold and gaseous
http://exoplanets.org/almanacframe.html
http://www.aao.gov.au/local/www/cgt/planet/aat.html