The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "brown dwarf"

  • Gliese 710, an Orange dwarf star, will be headed our way in 1.5 million years. Gliese 710 is expected to come within 1.1 light years of our Solar System, perturbing the Oort Clouds and its comets. Can it grab some of the moons of the giant gas planets (Jupiter, etc) and make them satellites for itself, re-arranging our Solar System?
  • It is not likely that Gliese 710 will have any effect on the moons of the gas giant planets because 1.1 light years is still a very long way away. For reference, the Sun is about 8 light minutes away from Earth. Pluto is about 5.6 light hours away from the Sun. At 1.1 light years away, Gliese will be over 5 trillion miles from the solar system. This may be close enough for the star’s gravity to have an effect on the edge of the Oort Cloud, as you mentioned, but this will likely mean an increase in meteor showers and comets. It would not completely rearrange our solar system.

    (Tags:  brown dwarf  earth  gravity  jupiter  meteor  planet  pluto  saturn  solar system)
  • I've heard people say Jupiter is a failed star since its made up of mostly Hydrogen and Helium like a star is. I know a Brown Dwarf is essentially a failed star, so would that make it correct to think of Jupiter as a Brown Dwarf? If not, why?
  • Jupiter is not a failed star or a Brown Dwarf. It is a gas giant planet. Brown Dwarfs are objects that are between 10 and 100 times more massive than Jupiter. They are not large enough to sustain Hydrogen fusion in the cores, this is why they are sometimes called failed stars. In order for Jupiter to be considered a Brown Dwarf it would need to get at least 10 times more mass than it currently has.

    (Tags:  brown dwarf  hydrogen  jupiter  star)
  • If Jupiter had developed into a brown dwarf star what effects would that have had on Earth's development? How visible would Jupiter be during the day and at night as a star?
  • If Jupiter was a brown dwarf star, it would not affect Earth very much. Brown dwarfs do not create much light, and since Jupiter is an average of 5 AU from the Earth (5 times the distance between the Earth and the Sun) it would appear as a pinpoint of light, a little brighter than Venus in the night sky. The farther away from the object you get, the dimmer and smaller it appears in the sky. For example, if we were to travel to Pluto, there would be no daytime. The Sun appears as a very bright star compared to the other stars in the night sky. But because it is so far away, it does not cast enough light on Pluto’s surface to have a bright daytime sky.

    (Tags:  brown dwarf  jupiter  pluto  star  sun)
  • Is Jupiter a "brown dwarf" star?
  • No. A brown dwarf is a kind of star. For Jupiter to exhibit any resemblance to a star it would have to fuse lighter elements into heavier ones in the core. An object needs to be about 80 times more massive than Jupiter for this to occur.

    (Tags:  brown dwarf  jupiter  planet  star)
  • What is the possibility of dropping U-238 into Jupiter, for example, to trigger the proton-proton chain reaction? Or, the CNO cycle (carbon-nitrogen-oxygen) to turn all the gas giants into mini-Suns? After all, U-238 has a half life of 4.5 Billion years, and we have a surplus of U-238!
  • Although it may allow us to get rid of our Uranium, this wouldn't work to create another Sun. Atoms bombs like those made with U-238 create fission reactions, which are the opposite of fusion reactions. In fission, you are breaking apart an atom and creating smaller ones – and a lot of energy! In fusion, like within a star, 2 small atoms are joining together to make a larger atom – and again a lot of energy. So, sending our atom bombs to Jupiter would only blow it up, not start a fusion reaction. The only way to start a fusion reaction is to add more mass. To make Jupiter into a small brown dwarf star, we would need to add about 9 more Jupiter’s worth of Hydrogen to the planet. To make a Sun-sized star out of Jupiter, we would have to add 100 more Jupiter’s worth of Hydrogen. That’s a lot of Hydrogen!

    (Tags:  brown dwarf  hydrogen  jupiter  sun)