Nice quizz about black holes and some data on Parker probe!

Captain Nemesis

Hi space.com community!

I just solved nice quizz about black holes, with 8/9 accuracy, and I want to give you the link so that you can check your own knowledge:

The article informs us that new black hole has been found, some 5 thousand ly from Earth, but what makes it interesting is that this is the first case of an isolated black hole discovery. Usually, black holes are detected as member of a binary system or, in other words, as the companion of the neutron star. Estimates say that there is around 100 million stellar black holes in the Milky Way which means that one day when we become able to make Dyson sphere there will be plenty of SBH to use as an energy source just in our galaxy. Woohoo!

The quizz is below the article.

I have correctly answered all questions except 4th: 4) When stars die, they become black holes if they have masses of at least - a) half the mass of the Sun (I immediately discarded this answer), b) three times the mass of the Sun or c) twice the mass of the Sun. I couldn`t decide between b) and c) because I know that Chandrasekhar limit is 1.4 solar masses. Therefore, I have chosen answer c) or "twice", as closer to the Chandrasekhar limit. Moreover, there are black holes having two solar masses. It was wrong. The correct answer is b) or three times the mass of the Sun. I checked it and learned that there is another limit called the Tolman–Oppenheimer–Volkoff limit which applies to the stars, while Chandrasekhar limit applies to the white dwarf star. Anyway, I am pleased with 8/9 which is solid 88.9%.

Second thing I want`t to clear is the comment I received from an acquaintance. I said that NASA Parker probe is exploring the Sun as we speak. He asked how is that possible due to the high temperatures? I replied that probe is checking outer layer not the core and that the engineers certainly used special materials and some internal cooling system.

Parker probe will get as close as aproxx. 6 million kilometers near the Sun (periphelion). That is Sun`s atmosphere not the Sun itself. Sun itself has 15 millions of degrees Celsius in the core and 5500 degrees at it surface. In order to sustain the atmospheric temperature of 1400 degrees Celsius, it has 11 cm thick carbon composite shield. Probe will travel around the Sun at the speed of 430.000 miles per hour or 700.000 kilometers per hour. I didn`t find data about internal cooling system which NASA obviously keeps as a secret but I guess that there must be somekind of a cooling device containing liquid Helium or equivalent.

Marvel and Helio

Helio

I just solved nice quizz about black holes, with 8/9 accuracy, and I want to give you the link so that you can check your own knowledge:
...

I have correctly answered all questions except 4th: 4) When stars die, they become black holes if they have masses of at least - a) half the mass of the Sun (I immediately discarded this answer), b) three times the mass of the Sun or c) twice the mass of the Sun. I couldn`t decide between b) and c) because I know that Chandrasekhar limit is 1.4 solar masses. Therefore, I have chosen answer c) or "twice", as closer to the Chandrasekhar limit. Moreover, there are black holes having two solar masses. It was wrong. The correct answer is b) or three times the mass of the Sun. I checked it and learned that there is another limit called the Tolman–Oppenheimer–Volkoff limit which applies to the stars, while Chandrasekhar limit applies to the white dwarf star. Anyway, I am pleased with 8/9 which is solid 88.9%.
Ditto! I knew the Chandrasekhar limit of 1.44, but have always been unclear of a hard black hole mass miniumum, though 3 seems to be far more accurate than 2, though I too guessed two.

It can be a little confusing also because these questions can cause one to think we are talking about the star's mass during its normal life, not after it dies. [This is a much higher number, and not one of the choices in the quiz, admittedly.]

I saw that the quiz became a Star Wars quiz and I got all correct! Also, it was interesting to see that the vast majority seemed to nail each question, so their knowledge of this fiction is much greater than for black holes. I guess I shouldn't be surprised.

Second thing I want`t to clear is the comment I received from an acquaintance. I said that NASA Parker probe is exploring the Sun as we speak. He asked how is that possible due to the high temperatures? I replied that probe is checking outer layer not the core and that the engineers certainly used special materials and some internal cooling system.
The extemely thin atmosphere of the Corona greatly diminishes the overall heating effect. I think solar radiation is far more the challenge than the few very hot ions in the corona. I read once where, ignoring surface radiation from the Sun, an astronaut could survive for a while in the hot, but tenuous, corona gas.

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Captain Nemesis

Chandrasekhar limit 1.4 is for the neutron stars.
Tolman-Openheimer-Volkoff 3.0 limit is for the black holes.

That means that stars which have mass 1.4-2.9 will become neutron stars.
Stars that have solar mass of 3.0 or above will become black holes.

Now I know.

Congratulations on 9/9 quiz, Helio.