Can O/B Stars Have Planets?

[t@nn]

From what I've been able to gather, O and B type stars can't have planets, because their heat/solar winds destroy planetary disks before they are formed.

And even if this didn't happen, the star would likely go supernova before the planets could finish forming. Is that about right?

[m1omg]

I tought that too, until I found this I think a year and half ago:

http://www.space.com/scienceastronom...ant_stars.html

So at least it is proven that dusty planet forming disks CAN remain around extreme stars.
And actually the planet formation process is not so long, only the subsequent geological activity cooldown and the formation of oceans, life etc...

[Argos]

Still, they won´t last too long.

[m1omg]

Still, they won´t last too long.

Yeah, of course, but they should be excellent sources of heavier elements due to their youth - meaning the material from which they have formed was more metal enriched than Sunlike stars.

[John Mendenhall]

Still, they won´t last too long.

Keeping in mind that first extrasolar planet ever found is orbiting a neutron star!

[Veeger]

Why couldn't planets form a little more distant from an O/B star? Its really not a gravity question but rather at what point does the solar wind cease to be a disruption to protoplanetary disks. There may be an extended inhabitable zone and then things settle down reasonably well.

Didn't research this - just speculating.

[timb]

Why couldn't planets form a little more distant from an O/B star? Its really not a gravity question but rather at what point does the solar wind cease to be a disruption to protoplanetary disks. There may be an extended inhabitable zone and then things settle down reasonably well.

Didn't research this - just speculating.

I agree that the logic of "the star's intense brightness makes the disk evaporate" is flawed. Irradiance drops with the square of distance, so far enough from even the brightest star it is cool. However, the location of the protoplanetary disk may scale according to gravity, which is proportional to mass, whereas luminosity is proportional to mass^~3.7. I think the correct answer is "we don't know". Planets have been discovered around a sdB star, but this is a postMS type. The earliest MS star known to have a planet is the A3 Fomalhaut. I know that exoplanet searches often exclude types O through A for a variety of reasons.

[antoniseb]

When an O or B star is forming, there is a time when there are starless cores in the collapsing medium. If some of these starless cores are within an order of magnitude of Jupiter's mass, it seems likely that accretion will get turned off when the big star lights up, but the mass of the planet will not shrink thereafter.

As to terrestrial type planets... who knows.

[Eroica]

Keeping in mind that first extrasolar planet ever found is orbiting a neutron star!

Good point. Is there any possibility that those planets formed after the host star went supernova, or would the supernova remnant quickly sweep up all available matter and carry it off into interstellar space?

[m1omg]

When an O or B star is forming, there is a time when there are starless cores in the collapsing medium. If some of these starless cores are within an order of magnitude of Jupiter's mass, it seems likely that accretion will get turned off when the big star lights up, but the mass of the planet will not shrink thereafter.

As to terrestrial type planets... who knows.

Well, I guess there will be actually more terrestrial planets around these stars than around lower mass stars, because as I said the material from which these stars formed was MUCH more enriched in metals than the material from which our Sun formed, so I'd expect to find very many massive and hot terrestrial planets around OB stars.

And coincidentally the dust disk found was extending hundreds to thousands AU from the star, so yeah the planets will simply form more far away, and planetary migration should provide for some very hot planets, and considering many of the most extreme stars are in the galactic center, where there is more carbon in the material...yeah, diamond planets...

I think the A-O stars are mostly excluded from the planet finding simply because of pragmatic reasons - consider the mass of these stars and that the planets would have to be hundreds of AUs away from these stars in order not to evaporate into clouds of gas the tug created by their gravity to their stars would be miniscule and the planet transit events would not be detectable, due to these stars appearing as extremely bright blinding dot from their planets and that these stars can be million times brighter than the Sun.

A good planetary temperature calculator;
http://www.astro.indiana.edu/~gsimon...perature1.html

For example, around 450 AU from Naos (also known as Zeta Puppis, O5 type main sequence star, 59-times as heavy as the Sun) a planet would have roughly Earthlike temperature.

There might even be EXTREMELY RARELY, life on OB stars planets brought somehow from other planets orbiting smaller stars and/or terraformed, through the UV insolation would be so extreme that it would require a very dense atmosphere (or extreme amounts of ozone - not unreallistic on terraformed worlds, because ozone is generated by interaction of UV with oxygen and these stars radiate extreme amounts of it = gigantic ozone layer) to shield the life from the deadly radiation.

[John Mendenhall]

Good point. Is there any possibility that those planets formed after the host star went supernova, or would the supernova remnant quickly sweep up all available matter and carry it off into interstellar space?

That'd be my first guess. Mechanism? Who knows? Maybe reassembly of shattered planetary fragments? Second would be what would happen to. oh, say a 15 Jupiter mass object?

[m1omg]

That'd be my first guess. Mechanism? Who knows? Maybe reassembly of shattered planetary fragments? Second would be what would happen to. oh, say a 15 Jupiter mass object?

Well AFAIK it is almost certain that they are formed from the supernova nebula and that even a brown dwarf in the Oort cloud regions of the system wouldn't stand a chance, we're talking about billions (!) of Solar brightnesses during supernova, but the enviroment around the neutron star is MUCH more extreme than the enviroment around even the hottest Wolf-Rayet stars, as neutron stars radiate hard X and gamma rays + exotic kinds of radiation capable of slowly eroding matter, these planets around NSs would have little atmospheres of nebulous plasma around them, from disintegrating rock...,

http://www.extrasolar.net/starlistto...arcatID=pulsar

[antoniseb]

There might even be EXTREMELY RARELY, life on OB stars planets brought somehow from other planets orbiting smaller stars and/or terraformed, through the UV insolation would be so extreme that it would require a very dense atmosphere (or extreme amounts of ozone - not unreallistic on terraformed worlds, because ozone is generated by interaction of UV with oxygen and these stars radiate extreme amounts of it = gigantic ozone layer) to shield the life from the deadly radiation.

Maybe. If it the life of an O or B star is about 10 million years, it seems unlikely that any planet will have cooled enough to support life before the star explodes.

[m1omg]

Maybe. If it the life of an O or B star is about 10 million years, it seems unlikely that any planet will have cooled enough to support life before the star explodes.

Well, AFAIK the planets cool in thousands of years, and the planets can still be terraformed, OB planetary systems could be great sources of metals and energy.
And it depends on the mass of the star, 10 million years would be the lifetime for an extreme O stars, the smallest B (around 3 Solar masses) main sequence lifetime would be little over 1 billion years, enabling even maybe native life to arise and the smallest O stars (around 18 Solar masses) will last around 30 million years on the main sequence, more than enough time for a planet to cool down.

Also, the temperate zones for hotter stars are very wide, it might be than even after the star leaves the MS the planets can have tolerable temperatures at least for a while, even A star such as Sirius would have habitable zone spanning around 5 AU if I remember correctly I've read that somewhere.

[t@nn]

Thanks for the input, guys (and sorry it took so long to reply: I've been busy and forgot that I'd posted this question. )

I guess planetary formation around those stars isn't as unlikely as I thought.