# Does black hole have the following properties? [closed]

1. Black holes emit x-rays lights from within their event horizons (I believe this one is unknown because you cannot see what's going on inside event horizon)

2. A 9 km black hole may be hidden between Saturn and Jupiter (I think it's true because the distance between these planets are larger than 9km).

3. A black hole in a binary system will suck in its companion (Not sure about this one because I don't think the effect is large in a non-close binary system)

4. Singularity of black hole has infinite density (I guess it is true but can't find evidence)

Could someone give any suggestion, please?

• Appears to be homework question. Nov 20 '16 at 11:06
• I'm voting to close this question as off-topic because this looks like someone's homework. Nov 20 '16 at 20:14
• Though it’s interesting to read his thoughts annotated to each question. This shows that what he really needs is a deeper understanding of the particulars. Nov 20 '16 at 20:16
• I agree with @JDługosz that the annotations are interesting, those cause this to be a higher quality question than the usual homework questions. It is still not good, but a small thing like that helps me to keep my faith in humanity. Nov 20 '16 at 23:30

2. A 9km black hole could not lie within the solar system without disrupting the orbits of nearby planets. A black hole 9km across would have to be about 3 times more massive than our sun. You can calculate this by using a simplification of the formula for the Schwarzschild Radius: $r\approx 2.95 \frac{M}{M_{\odot}}$. If this were the case, then the orbital motions of the planets would be dominated more by this black hole than by the sun.