With the recent hoax of having Jupiter ignite and become a second sun a question developed. What would actually happen if Jupiter did ignite into a second sun ? Would we vaporize ? The oceans boil away ? Proof of global warming ? Extra high SPF lotions or just a new feature in the sky ? Thought about sending it to Uncle Cecil but I thought I’d start here.
This is not possible under the current laws of physics as we know them and our knowledge of the properties of Jupiter. If it were to happen, it would mean that either the laws of physics as we know them are wrong, the laws of physics have changed, the properties of Jupiter as we know them are wrong, or the properties of Jupiter changed. Without knowing what the new, true laws of physics and properties of Jupiter are, we cannot begin to speculate on what the results would be.
What recent hoax?
Jupiter isn’t sufficiently massive to ignite. Something massive enough to ignite in a Jovian orbit would significantly affect the orbits of all the other planets.
I think Hubble has detected some strange monoliths orbiting it, and for that reason, NASA is a little concerned.
Jupiter would have to be something like 75-80 times as massive as it is now to become a Main Sequence star (which means it would burn hydrogen in its core). Bringing that mass into the Solar System would potentially be fairly disruptive to the planets, asteroids, comets, etc, that are here now.
Even if a brown dwarf (a star that is too small to fuse hydrogen in its core) will do, you’d need Jupiter to be about 13 times as massive as it is to fuse deuterium (which is the easiest element to fuse). You still need to get 12 times the mass of Jupiter into the solar system.
Isn’t Jupiter farther away from us than our sun is? Like a whole order of magnitude farther away?
I don’t think much would happen to us even if Jupiter did ignite and become a second sun. Aurora Borealis woud be spectacular, but that is about it.
Jupiter is 5.2 AU (astronomical units) from the Sun. 1 AU is the distance between the Earth and the Sun. Jupiter’s minimum distance from us is 4.2 AU, or a little over four times as far away as the Sun. Jupiter’s maximum distance from us is 6.2 AU. A second sun would still be pretty bright at a distance of 4-6 AU. It would be maybe 20-30 times fainter than it is now, but the Sun is more than 400,000 times brighter than the full Moon, so it would still be a lot brighter than the full Moon.
You mean if Jupiter was a third sun. We might already have a second sun. 
I heard that these monoliths appeared to be sucking up the Jovian atmosphere.
Okay, let’s start to make some assumptions. If Jupiter becomes about as luminous as the faintest white dwarf we can spot with fairly standard telescopes, like Barnard’s star or Proxima Centauri, that’ll make it much less brighter again, but probably still better than moon level.
Is there any way to estimate the effect this would have on the Earth’s climate, from radiative heating??
Hmm… Proxima Centauri has an absolute magnitude of 15.49, which is pretty dim, but it’s also a flare star. :eek: And our sun has an absolute magnitude of 4.83 - so how much brighter is the sun than Proxima Centauri under ordinary conditions, not considering distance?
What can this lead to? Something wonderful, I hope.
Proxima Centauri and Barnard’s star aren’t white dwarfs. They’re red dwarfs. If you want a white dwarf, Sirius B is a good nearby example.
If you wanted to turn Jupiter into a white dwarf, you’d have to turn it into a star that could fuse hydrogen and let that star run out of hydrogen and helium fuel (the more massive the star is, the faster this will happen). That would be a lot harder than turning it into a red dwarf.
A difference of one magnitude is a difference of about 2.5 times in brightness. Raise 2.5 to the 15.49 - 4.83 power to get the difference in brightness. The answer comes out to be that the Sun is about 17,500 times brighter than Proxima Centauri in absolute magnitude.
Proxima Centauri would appear about 1/17,500 as bright as the Sun if it were where the Sun is now. It would appear 20-30 times fainter than that if it were where Jupiter is now, because it would be further away. It would be 350,000 - 525,000 times as faint as the Sun, depending on how close to it we were at any given time (it’s going to vary as Earth and Proxima Centauri orbit the Sun). The full Moon is in that range of brightness. It would sometimes be brighter and sometimes fainter than the full Moon.
Probably. I don’t remember how to do it offhand.
I can make a guess, though. The full Moon doesn’t appreciably affect temperatures on Earth. Since Proxima Centauri in Jupiter’s orbit would be roughly the same order of magnitude of brightness, I’m going to guess that it wouldn’t either.
But the climate isn’t just affected by light, is it? Wouldn’t the increase in solar radiation in other ranges of the EM spectrum (which the moon cannot generate) be prone to have some effect?
Nitpick: you mean red dwarfs.
And from wikipedia, the full Moon has an apparent magnitude of −12.6 and the Sun (at 1 AU) has an apparent magnitude of −26.73. A star in Jupiter’s orbit would vary in distance between 4 AUs and 6 AUs. Am I wrong in thinking that if the sun were 4 times farther away we’d get 1/4th the solar radiation? Someone else is going to have to do the math…
1/16- remember the inverse square law.
Replacing Jupiter with a red dwarf like Proxima Centauri is not going to vaporize the Earth or boil the oceans (ignoring any effect that getting another star into the solar system might have on Earth’s orbit).
Probably not. Sunscreen is designed to protect against ultraviolet light. Red dwarf stars emit a lot less ultraviolet light than the Sun does.
I thought Nemesis was big and black? 
Yes I did mean red dwarfs, sigh. :smack:
For the record – the line between brown dwarfs (AKA superjovian planets) and Jovians is pretty much arbitrary, AFAIK. There is a real nitpicky, technical sense in which Jupiter, as it is now, could be considered an ultrasmall failed star. Like this:
The Main Sequence is comprised of stars which ‘burn’ hydrogen (by fusion) in their cores (and I’ll accept any correction needed on what happens in the cores of O and B main sequence stars at the bright end of the continuum.) But the point to the Main Sequence is that there is a clear interrelationship: the more massive the star, the hotter and brighter it is, and the faster it uses its hydrogen ‘fuel’. Conversely, at the lower end, the M and N stars (red dwarfs) are least massive, dimmest, and the most (relatively) cool and slow-burning. At some point, continuing down the scale, you get a – well, star in the most generic sense, a ball of warm gas – which is inadequately massive to get the temperature and pressure needed to burn hydrogen in the core. As Anne Nevile noted, there’s a range where the star is not hot enough to burn protium (H[sub]1[/sub]) but will burn deuterium (H[sub]2[/sub]). How any protostar gets to the point of ignition, if it does, though is to contract, which heats up the core, and that heat eventually spreads to heat up the outer layers and the surface. So your typical big superjovian is going to be a body of gas, mostly hydrogen, radiating dimly in the infrared – i.e., warm gas. Not with the Sun’s 6000 K surface temperature, nor even the ~4000 K surface temperature of a M star, but maybe 1500 K or less. Keep making it less massive and it will be cooler (less gravitational heat of contraction), less like a small dim star and more like a gas giant planet.
Jupiter’s surface temperature (visible surface, cloud tops, that is) is about -100 C. But its black body temperature if it were simply heated by the Sun would be about -200 C. Its core is clearly being heated by gravitational contraction, and that in turn is raising its temperature above the inert external-heat-source-only blackbody figure. So Jupiter has a very nitpicky claim to being the smallest, coldest failed star on record, radiating at a temperature colder than the coldest temperature ever recorded on Earth.
According to the Bad Astronomer’s new book, Death from the Skies and a little math, even if we (somehow) replaced Jupiter with a twin of the Sun it wouldn’t boil Earth’s oceans away (assuming the process of getting another Sun into the solar system didn’t change Earth’s orbit. Of course it would, but you can’t calculate how it would change Earth’s orbit, so we’ll pretend it wouldn’t.). The Sun is getting brighter as it ages, and he says that the oceans will evaporate when the Sun is about 40% brighter than it is now, in about 3.5 billion years. I calculated earlier that a star like the Sun in Jupiter’s orbit would look at least 20 times fainter than the Sun from Earth. That means we’d only be getting 5% more light from the Sun plus the new star, not the 40% more that would be needed to evaporate the oceans.
If it wouldn’t boil the oceans, of course it’s not going to vaporize rock.