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Kullat Nunu
2008-Sep-15, 10:24 AM
To be confirmed. (http://www.gemini.edu/sunstarplanet)

arXiv.org preprint (http://fr.arxiv.org/abs/0809.1424)

frankuitaalst
2008-Sep-15, 11:19 AM
This would be a really great discovery ! .
Seems we'll have to wait a couple of years before confirmation the body is gravitationally bounded to the star.
It surprises me , when looking at the picture the planet has a distance of 330 Au to the sun . Seems to be much closer on the picture . I guess the sun is overexposed ?

mantiss
2008-Sep-15, 02:08 PM
This would be a really great discovery ! .
Seems we'll have to wait a couple of years before confirmation the body is gravitationally bounded to the star.
It surprises me , when looking at the picture the planet has a distance of 330 Au to the sun . Seems to be much closer on the picture . I guess the sun is overexposed ?

My guesses are: 1) Both objects are overexposed which of course would give a false illusion of closeness. 2) Perspective is tricking you, the putative planet might be far behind the star and look closer, this is plausible since being behind the star it would reflect most of the starlight at us, instead of looking like a half moon or a quarter moon. I don't think our technology however allows us to distinguish between phases at that distance yet.

Ilya
2008-Sep-15, 03:33 PM
My guesses are: 1) Both objects are overexposed which of course would give a false illusion of closeness. 2) Perspective is tricking you, the putative planet might be far behind the star and look closer, this is plausible since being behind the star it would reflect most of the starlight at us, instead of looking like a half moon or a quarter moon. I don't think our technology however allows us to distinguish between phases at that distance yet.

The picture is taken in infrared, and the planet's light is its own infrared emission, not the reflected light from its star. It would not show any phases.

eburacum45
2008-Sep-15, 08:23 PM
A planet 330 AU from its star, with 8 times the mass of Jupiter, is like nothing in our Solar System.

timb
2008-Sep-15, 09:40 PM
A planet 330 AU from its star, with 8 times the mass of Jupiter, is like nothing in our Solar System.

More like a very small binary companion than a planet. Why does this body's existence challenge current theories of planet formation? We already know stellar companions can exist at wide separations.

toothdust
2008-Sep-15, 09:45 PM
Seems kind of far from its parent star to be lit up bright enough for us to see.

Edit: I see now that they imaged it in infrared. If Jupiter is only at about 160degrees K, and this body is at around 1800degrees K, could this be some kind of as yet to be discovered class of star?

Has the possibility of binary been ruled out?

Romanus
2008-Sep-15, 10:31 PM
Assuming it's confirmed, it would indeed be an exciting first. However, I'm still holding out for imaging an older, "settled" planet or planets, such as the one around Epsilon Eridani. Planets fresh out of the oven, as it were, just don't intrigue me as much, though YMMV.

neilzero
2008-Sep-16, 03:10 AM
1800 degrees k likely means it is a new planet that has not cooled much yet and/or a recent impact heated it's surface. 8 times Jupiter's mass is still a planet. Our solar system likely has only Mercury mass objects or lighter at about 330 AU = astronomical units. Neil

CuddlySkyGazer
2008-Sep-16, 05:42 AM
Given the relative masses and distance, the centre of gravity of the star and 'planet' will lie well outside the star. There'll be some dispute therefore as to whether or not the object is orbiting the star, as opposed to them orbiting each other, and therefore as to whether or not this object is a planet.

I notice the discoverers in their paper are very careful not to call this object a planet, referring to it as the star's companion or as a planetary mass object instead.

timb
2008-Sep-16, 06:01 AM
Given the relative masses and distance, the centre of gravity of the star and 'planet' will lie well outside the star. There'll be some dispute therefore as to whether or not the object is orbiting the star, as opposed to them orbiting each other, and therefore as to whether or not this object is a planet.

I notice the discoverers in their paper are very careful not to call this object a planet, referring to it as the star's companion or as a planetary mass object instead.

According to the IAU 2003 draft guideline (http://en.wikipedia.org/wiki/Extrasolar_planet#Definition) it's a planet if it orbits the star, because its mass is less than 13 Jupiters. That doesn't mean that it formed in the way that planets normally form. I don't think the question of whether they orbit each other is relevant or even meaningful. In any such binaries both objects orbit the barycenter, which may or may not lie inside one of the objects. The barycenter of the Sun-Jupiter pair lies outside the Sun, but that has no bearing on whether Jupiter is a planet. I assume the authors are cautious because they haven't proved that the two are gravitationally bound.

Kullat Nunu
2008-Sep-16, 06:26 AM
This planet seems more like a sub-brown dwarf than a normal planet. Hard to see how it could get so far from its star if it formed from a protoplanetary disk unless something threw it out. More likely it formed directly from the collapsing protostellar nebula. Still, if the mass estimation is correct, it should be called a planet no matter how it formed since it is more like a giant planet and will not ever fuse deuterium like real brown dwarfs (m >= 12 MJ).

timb
2008-Sep-16, 10:33 AM
This planet seems more like a sub-brown dwarf than a normal planet. Hard to see how it could get so far from its star if it formed from a protoplanetary disk unless something threw it out. More likely it formed directly from the collapsing protostellar nebula. Still, if the mass estimation is correct, it should be called a planet no matter how it formed since it is more like a giant planet and will not ever fuse deuterium like real brown dwarfs (m >= 12 MJ).

Much my thoughts. Failed brown dwarf. The something threw it out hypothesis can't be rejected out of hand. Playing with an orbit simulator I find it's not too hard for planets to be ejected or thrown into orbits of extreme eccentricity by close encounters with larger planets or stellar companions. It's not obvious how by pertubations a planet would get into an less eccentric orbit with such a large sma.

ryanmercer
2008-Sep-16, 11:02 AM
If it pans out to bet rue... awesome.

AndreasJ
2008-Sep-16, 11:10 AM
Cool. :) Or rather, at 1800 K, hot! ;)

Fiery Phoenix
2008-Sep-16, 11:18 AM
That's right, Nunu. It could be some kind of a dwarf star; and so it's a binary system. If it is indeed a planet, though, then I am nothing but amazed.

Let's just wait for the confirmation.

CuddlySkyGazer
2008-Sep-16, 12:09 PM
According to the IAU 2003 draft guideline (http://en.wikipedia.org/wiki/Extrasolar_planet#Definition) it's a planet if it orbits the star, because its mass is less than 13 Jupiters. That doesn't mean that it formed in the way that planets normally form. I don't think the question of whether they orbit each other is relevant or even meaningful. In any such binaries both objects orbit the barycenter, which may or may not lie inside one of the objects. The barycenter of the Sun-Jupiter pair lies outside the Sun, but that has no bearing on whether Jupiter is a planet.
I said there will be a dispute, and there will be, because the definition of when one object orbits another and when they orbit each other, and whether there is any difference between the two is disputed, and what is also disputed is which one is relevant when classifying planets etc. (The IAU 2003 draft guideline is a draft guideline because the astronomers on the relevant IAU committee couldn't decide on these and other questions.)

Is Pluto/Charon a dwarf planet and moon, or a double dwarf planet? Is Earth/the Moon a planet and moon or a planet/dwarf planet double? But yes, the Sun/Jupiter situation is a reasonable counter-argument, but not a good one because it depends on a priori classification rather than determining a set of criteria and then applying it. Pluto used to be a planet, until new discoveries meant the criteria changed. This is the sort of discovery that produces such results - we'll have to see what the outcome is.


I assume the authors are cautious because they haven't proved that the two are gravitationally bound.
Possible, but I wouldn't assume it. :) (Especially given the fact that they refer to this planemo as the star's 'companion'!)

Gigabyte
2008-Sep-16, 12:32 PM
Pluto used to be a planet, until new discoveries meant the criteria changed.

That is called Wikiality. Where consensus is used to decide what is truth.

mantiss
2008-Sep-16, 03:50 PM
I sure hope they don't call it an Extra-Solar Mega-Plutoid :lol:

mantiss
2008-Sep-16, 03:53 PM
The picture is taken in infrared, and the planet's light is its own infrared emission, not the reflected light from its star. It would not show any phases.


You're right, it pays to read and I should have read the article in more details. Thanks for the clarification.

AndreasJ
2008-Sep-16, 04:45 PM
My guesses are: 1) Both objects are overexposed which of course would give a false illusion of closeness. 2) Perspective is tricking you, the putative planet might be far behind the star and look closer, this is plausible since being behind the star it would reflect most of the starlight at us, instead of looking like a half moon or a quarter moon. I don't think our technology however allows us to distinguish between phases at that distance yet.
Actually, 330 AU appears to be a minimum separation, assuming the star and companion to be at exactly the same distance from us.

From the paper, the separation angle is 2.2'' and the distance is 150 pc. This works out to a separation of 330/cos(i) AU, where i is the angle between the plane of the sky and the actual separation vector.

toothdust
2008-Sep-16, 05:16 PM
1800 degrees k likely means it is a new planet that has not cooled much yet and/or a recent impact heated it's surface. 8 times Jupiter's mass is still a planet. Our solar system likely has only Mercury mass objects or lighter at about 330 AU = astronomical units. Neil

Fresh out of the oven at 330 AU? That must have been one hell of a planetary nebula. I wonder why we see no planets closer in?

Gigabyte
2008-Sep-16, 05:48 PM
It is still really really cool.

toothdust
2008-Sep-16, 06:26 PM
It is still really really cool.

Agreed!:)

timb
2008-Sep-17, 03:10 AM
I said there will be a dispute, and there will be, because the definition of when one object orbits another and when they orbit each other, and whether there is any difference between the two is disputed, and what is also disputed is which one is relevant when classifying planets etc.


Disputed by whom? can you cite a reliable source? The diameter of a star or gas giant planet is somewhat vague, most stars change greatly in size over their life time, and some do so periodically. Your suggestion would mean that the status of many objects would vary between "planet" and sub-brown-dwarf. When the primary ends its life as a neutron star or black hole even surviving Earth-mass planets would have to be reclassified as sub-brown-dwarfs because the barycenter would now lie outside the primary.

Planetary orbits are also subject to change.



(The IAU 2003 draft guideline is a draft guideline because the astronomers on the relevant IAU committee couldn't decide on these and other questions.)

Is Pluto/Charon a dwarf planet and moon, or a double dwarf planet? Is Earth/the Moon a planet and moon or a planet/dwarf planet double? But yes, the Sun/Jupiter situation is a reasonable counter-argument, but not a good one because it depends on a priori classification rather than determining a set of criteria and then applying it.


One of the main goals when developing a definition for a term already in use is that it conform to established usage. Such a definition is an attempt to abstract a rule from data that already exists. Changes to the status quo are controversial and confusing. Adding a demand that the barycenter lie within one of the objects would serve no useful purpose and would confuse the status of Jupiter. Sometimes the process reveals that a much cleaner rule can be derived if a small subset is reclassified. That is what happened in the case of Pluto.


Pluto used to be a planet, until new discoveries meant the criteria changed. This is the sort of discovery that produces such results - we'll have to see what the outcome is.


So do you forecast that Jupiter's days as a planet are numbered?

CuddlySkyGazer
2008-Sep-17, 11:59 AM
Disputed by whom? can you cite a reliable source?
I am a reliable source. :)

(More seriously, this is a forum, not a science journal. Believe me or not, it's no skin off my nose. If you want to prove me wrong, you do the research.)


Your suggestion ...
I have made no suggestion.


One of the main goals when developing a definition for a term already in use is that it conform to established usage. Such a definition is an attempt to abstract a rule from data that already exists. Changes to the status quo are controversial and confusing.
All true, but controversial changes to established usage do occur.


Adding a demand that the barycenter lie within one of the objects would serve no useful purpose...
That's opinion, which may not be shared by others.


Sometimes the process reveals that a much cleaner rule can be derived if a small subset is reclassified. That is what happened in the case of Pluto.
I don't think so! It would have been a much clearer rule if the definition favoured by Stern and others was adopted - i.e. any hydrostatically round object orbiting the Sun.


So do you forecast that Jupiter's days as a planet are numbered?
The only thing I forecast was that there'll be a dispute as to whether the newly discovered object is a planet or not - but seeing as you ask, I rather doubt it! :)

Noclevername
2008-Sep-22, 02:48 AM
That's right, Nunu. It could be some kind of a dwarf star; and so it's a binary system. If it is indeed a planet, though, then I am nothing but amazed.

Let's just wait for the confirmation.

The article says eight times the mass of Jupiter, so a planet, not a star. Not enough mass to ignite a fusion reaction.