The caller on Thom's TV show today claiming that the WISE infrared telescope had found a "brown dwarf" between the orbits of Mars and Jupiter really sounded unlikely. Here are a few facts:
- Satellite telescopes since the IRAS probe in 1983 in have been launched primarily because the earth's atmosphere blocks out almost all the infrared radiation from celestial objects that emit infrared radiation and little or no visible light. "Infrared" is the electromagnetic radiation that is radiated from objects that are cooler than the radiation in the optical spectrum. The latest generation of infrared telescopes use much more sensitive detectors that are cooled with liquid helium to only two degrees Celsius (about four degrees Fahrenheit) above absolute zero. At this temperature, the satellite itself emits only trace amounts of infrared and thus can detect much more infrared emitted by celestial objects.
(This is comparable to, say, building a large telescope with strobe lights pointing down the tube and setting up the telescope in the middle of Manhattan. You can see how this wouldn't be the very best setup to look at faint objects emitting visible light.)
-- A "brown dwarf" is an object that didn't have quite enough mass when it was formed out of an area of gas and dust to start fusion of hydrogen to helium reactions at its core. A brown drawf is doomed to spend its life simply cooling off from mostly the heat generated when the brown dwarf was created. Brown dwarfs would be anywhere from a few times more massive than the gas giant Jupiter up to the mass of 70 to 80 Jupiters.
So... an object even just the mass of Jupiter (and which would therefore never heat up enough to be anything more than a hot gas giant planet and never becoming a brown dwarf would still have so much mass that its gravity would pull greatly on all the other planets in our solar system. This would be such a large pull that we would have noticed something unusual even with the telescopes of severall hundred years ago.
Nevertheless, I think Thom and everyone else on the blogs would enjoy looking up the ACTUAL truly amazing things that the WISE telescope is finding. Just go to www.nasa.gov and put in the search terms "WISE" and "infrared." If you have trouble finding WISE information there, just add a question to this topic, and I'll check back to see if I can help you find what you're interested in.
I used to be a planetarium director, actually GETTING PAID to answer astronomy questions that I'm still happy to talk about for free, so I would be delighted to answer any questions on infrared astronomy.