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Planetquest reports on the discovery of the largest known extrasolar planet. TrES-4's mass was found to be only 0.84+/- 0.10 that of Jupiter but its radius is 1.674+/-0.094 Jupiter's. That is, well, large. It works out to ~119,680km (radius, not diameter) if I am lazy and use Wikipedia and Jupiter's equatorial radius.
Aaaanyway, for a long while Jupiter was thought to be about as large as a non-stellar object could get because as mass is piled onto it (pretend you are an advanced alien civilisation that puts stuff on other stuff for fun), the increase in its gravitational field balances its tendency to expand, so that even brown dwarfs many times Jupiter's mass are nearly the same size. It is only when the object is sufficiently massive for fusion to occur that hydrostatic equilibrium shifts again and the object 9star, now, or young massive brown dwarf) expands to much larger size.
Well, this is what was thought when the prevailing opinion was that all gas giants exist comfortably far from any stars, much as Jupiter does. Then we discovered the solar system is not as ordinary as we thought and a great many giant planets orbit their stars with suicidal closeness. External heat sources can do the job of internal ones in a pinch, so many of these 'hot jupiters' (yes, that is what they are being called these days, those wacky astronomers - I can imagine people in the distant future talking about jupiter this and jupiter that and not knowing where that particular technical term came from) are larger in size than our Jupiter, even though they tend to be lower in mass.
Of course in the years since models have been developed to explain the expansion of superheated giant planets, but one of the things that make TrES-4 so interesting is that it is actually larger even than those models predict, so I am very much looking forward to finding out why.
...
People like facts and figures, right? TrES-4 has a density of ~0.2g/cubic cm, roughly the same as balsa wood. It and its host star - which is more massive than Sol and thus entering its giant phase despite being about the same age* - are around 1400 light years distant and its temperature is about 1600 K. Its orbit is only about 4,500,000 km from the surface of its sun and its period is roughly three and a half days.
Happy now? ^_^
Love,
Tricia Fakename
*This world, the same age as our own, is at the end of its natural lifespan. Superheated and boiling away, it will soon be swallowed up and blasted out existence by the death throes of the star which gave birth to it.
Aaaanyway, for a long while Jupiter was thought to be about as large as a non-stellar object could get because as mass is piled onto it (pretend you are an advanced alien civilisation that puts stuff on other stuff for fun), the increase in its gravitational field balances its tendency to expand, so that even brown dwarfs many times Jupiter's mass are nearly the same size. It is only when the object is sufficiently massive for fusion to occur that hydrostatic equilibrium shifts again and the object 9star, now, or young massive brown dwarf) expands to much larger size.
Well, this is what was thought when the prevailing opinion was that all gas giants exist comfortably far from any stars, much as Jupiter does. Then we discovered the solar system is not as ordinary as we thought and a great many giant planets orbit their stars with suicidal closeness. External heat sources can do the job of internal ones in a pinch, so many of these 'hot jupiters' (yes, that is what they are being called these days, those wacky astronomers - I can imagine people in the distant future talking about jupiter this and jupiter that and not knowing where that particular technical term came from) are larger in size than our Jupiter, even though they tend to be lower in mass.
Of course in the years since models have been developed to explain the expansion of superheated giant planets, but one of the things that make TrES-4 so interesting is that it is actually larger even than those models predict, so I am very much looking forward to finding out why.
...
People like facts and figures, right? TrES-4 has a density of ~0.2g/cubic cm, roughly the same as balsa wood. It and its host star - which is more massive than Sol and thus entering its giant phase despite being about the same age* - are around 1400 light years distant and its temperature is about 1600 K. Its orbit is only about 4,500,000 km from the surface of its sun and its period is roughly three and a half days.
Happy now? ^_^
Love,
Tricia Fakename
*This world, the same age as our own, is at the end of its natural lifespan. Superheated and boiling away, it will soon be swallowed up and blasted out existence by the death throes of the star which gave birth to it.
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no subject
Date: 2007-08-16 11:53 (UTC)From:Giant phase XD
I wish cats entered giant phases XD
That sounds interesting tho :O Like something the Enterprise would explore and then promptly find something scary or weird about it, or something would happen that would disable the ship sending them hurtling towards the planet XD
no subject
Date: 2007-08-16 12:03 (UTC)From:I bet it would be a spatiotemporal anomaly of some sort. Involving the Romulan Borg.
no subject
Date: 2007-08-16 20:16 (UTC)From:I find it all fascinating, if a little confusing. I mean, if we're down here what's the point in having all the rest of that stuff up there?
On a more serious note, I've not heard of a brown dwarf before... Wikipedia time.
Alice X