Is this true? Does a light source also reflect light? I’m not a physicist so I’m just working with analogies. It seems to me that a lightbulb has more apparent brightness at night than during the day.
Somebody experimented with this in Universe Sandbox 2. Granted, it’s a fairly simplistic simulation based only on Newtonian physics, but still interesting nonetheless.
Analog, volume 109, number 10 (October 1989). “Stellifying Jupiter” by Martyn J. Fogg.
In December of the same year he published the article “Stellifying Jupiter: A First Step to Terraforming the Galilean Satellites,” Journal of the British Interplanetary Society , 42, 587-592 (1989).
I have not been able to find the text either article online.
If you’ve got an academia.edu account, it’s here: (PDF) Stellifying Jupiter: A First Step to Terraforming the Galilean Satellites | Martyn Fogg - Academia.edu
The abstract:
Jupiter might be turned into an artificial star by seeding it with a primordial black hole of approximately 10^-4 Earth masses. Eddington limited accretion onto the hole would produce sufficient energy to create an ecosphere ~ 7x10^8 m from Jupiter, giving effective temperatures for Europa and Ganymede similar to the values for Earth and Mars respectively. As the black hole grows, so does its Eddington limit and its accretion luminosity; Jupiter would exponentially brighten. The Galilean satellite zone would remain habitable for ~ 10 – 100 million years. After this time, Jupiter might be surrounded by a miniature Dyson Sphere until, about half a billion years after stellification, the planet would have to be dismantled to starve the hole of any further mass to prevent it from becoming dangerously over-luminous. The feasibility of this scenario depends upon (1) the prevalence of primordial black holes; (2) the existence of a technologically advanced civilisation within the future Solar System and (3) a modest to high value for the efficiency of conversion of rest mass to energy for black hole accretion from a dense medium. All three of these assumptions are reasonable, given the magnitude of uncertainty in each case.
I found the Analog one very quickly on the first page of results when I had the right name. Scanned and uploaded by me, actually, more than 10 years ago before Scribd became pay-to-play.
Thanks for all of the replies, some of which (like possibly needing to add twelve Jovian masses) is causing me to reconsider my plans. I was trying for something nice for the people of Earth after the shit year they’ve all had but now I’m going to cancel the contract. I told my brother we shouldn’t have neglected the environmental impact statement.
If you had the magic technology to turn Jupiter into a Star, you could probably just import one.
Yes, a lightbulb reflects light.If you look at a lit lightbulb in the daylight you can generally see both the reflected light and the emitted light; in full sunlight the reflected light can be much brighter than the emitted light. At night you generally only see the emitted light - but your eyes adapt, making it look brighter in contrast to the darkness all around.
Your eyes are very, very good at adapting to darkness- sometimes becoming as much as a million times more sensitive to light in the dark.
I think this is an achievable goal, using technology we can just about foresee in the present day. If you want to make Jupiter into a star as seen from Earth, you could use multicoloured, fusion-powered lasers floating in the atmosphere of the planet (either suspended from hot-hydrogen balloons or held up by fusion candles, as described earlier).
Point all the lasers at Earth, and at the very least you could increase the apparent magnitude of that planet, possibly enough to make a difference if you have enough of them.
I fondly imagine that laser-illumination of specific targets could become a significant part of the ecology of the Solar System, giving light and heat to locations far from any other source of energy.
Here’s Randall Munroe, describing a similar thought experiment concerned with illuminating the Moon.
https://what-if.xkcd.com/13/
Which is more or less the mechanism I suggested (though a black hole probably works better, since the minimum size of stable neutronium may be larger than the mass of Jupiter).
You’d be amazed how many GQs start out this way. And how much fun we sometimes have answering them.
But yeah, you hit the nail perfectly there.
You’ve got to admire a guy who considers obtaining a primordial black hole a ten thousandth the size of the Earth and throwing it into a planet to form an Eddington pseudo-star, then later dismantling that star once it gets too hot, to be a “first step” in something.
Big men make big plans.
Do you really need Jupiter to do all that. Wouldn’t it just be easier to construct a million times smaller (empty) orb with all that stuff on it and place it a million times closer to the Earth to create the same effect?
In the short term, yes.
In the long term, no, because Jupiter is a good source of fuel for artificial illumination and power.
Incidentally, today is the day of the Great Conjunction between Jupiter and Saturn; see it if you can. I managed to see it last night in binoculars, and it’s a remarkable sight (the planets are closer together than they have been for hundreds of years, just after sunset, low in the west).
In the book, the effect on Earth was not the point. The effect on Europa (attempt no landings there) was what mattered (as long as the effect on Earth was small enough not to kill us all).
It’s incredible. Easily seen even with large metropolitan area lights all around. I used a set of 10X50 binoculars, but they aren’t necessary to see the planets. (They are to see Jupiter’s moons, Saturn’s rings, and Titan though.)
NASA’s blog page with simulations of the images: Jupiter-Saturn Great Conjunction: Watch Best View Since Middle Ages! – Watch the Skies
Some really stunning photos of the conjunction here: Your photos of 2020's historic Jupiter-Saturn conjunction | Astronomy Essentials | EarthSky
Unless it’s cloudy, as it has been around here for the last week. Almost had enough of a break in the clouds last night to see it, but it stayed cloudy to the west until after it would have set.
Frasier Cain was going to do a virtual star party today during the conjunction, but apparently that got canceled. 
That’s a shame. It’s worth your time to drive to someplace with appropriate weather, if that’s feasible. The images I saw through my binoculars weren’t terribly far from those EarthSky photos I linked to. Especially notable was my surprise at seeing Saturn’s oblong disk (because of the rings), actually being able to see Titan, and the difference in color between Jupiter and Saturn.
I’ve been watching the conjunction for a few days now, and far be it for me to tell astronomers they’re wrong, but it looks like last night might have been the closest approach, and not tonight’s viewing. (Saturn had been to the upper left of Jupiter for every previous viewing besides last night, when it was on the upper right. I’d think it would be even more to the upper right tonight.)
As an aside, Martyn Fogg’s method isn’t a meaningful indication of “how bright Jupiter would be if it were a star”. He started by determining the luminosity he wanted (to give Europa and Ganymede a good climate), and then from that calculated the size of the black hole that would be needed. The luminosity is purely a function of the added black hole, not of any of Jupiter’s own properties.