Universe, Black hole, Sun - Current Affairs Questions and Answers

1)   A middle sized black hole weighing how much was recently found by scientists?

a. 2,200 suns
b. 2,300 suns
c. 2,400 suns
d. 2,500 suns
Answer  Explanation 

ANSWER: 2,200 suns

An important cosmic missing link has been found: a middle sized black hole.

Till now, scientists had found either small black holes weighing a few Suns or supermassive black holes weighing millions or billions of Suns, like the one at the centre of our galaxy, the Milky Way.

But in an ancient cluster of stars some 13,000 light years away from Earth, scientists discovered an intermediate-mass black hole (IMBH) weighing 2,200 Suns.

It was hiding at the centre of the globular star cluster 47 Tucanae.

Such holes serve as missing link between stellar-mass and supermassive black holes. They may be the primordial seeds that grew into the monsters seen in the centres of galaxies.

47 Tucanae had been examined for a central black hole before without success.

In most cases, a black hole is found by looking for X-rays coming from a hot disk of material swirling around it.

This method only works if the black hole is actively feeding on nearby gas.

The centre of 47 Tucanae is gas-free, effectively starving any black hole that might lurk there.

A black hole also betrays its presence by its influence on nearby stars causing them to speed up.

But the crowded centre of 47 Tucanae makes it impossible to watch the motions of individual stars.

Scientists studying 47 Tucanae found that heavy stars nearer the centre were getting speeded up and flung away as if a cosmic "spoon" was stirring the pot.

This was measured by the astronomers and compared with computer simulations, leading them to conclude that there was some very heavy body at the center causing this gravitational stirring.

Pulsars were also found at greater distances from the cluster's centre than would be expected if no black hole existed.

Combined, this evidence suggests the presence of an IMBH of about 2,200 solar masses within 47 Tucanae.

47 Tucanae: Know More

  • 47 Tucanae is a 12-billion-year-old star cluster located in the southern constellation of Tucana the Toucan.
  • It contains thousands of stars in a ball only about 120 light-years in diameter.
  • It also holds about two dozen pulsars that were important targets of this investigation.

2)   What is the Zero Shadow Moment?

a. When the sun is directly overhead
b. When there is no shadow of an object
c. When the sun is setting
d. When the sun is rising
Answer  Explanation 

ANSWER: When the sun is directly overhead


  • During the zero shadow moment/day, the sun is directly overhead and the shadow is cast below the object.
  • If the object is on the ground it is difficult to see its shadow and it may look like there is no shadow. However this is not the case. There is shadow which may not be easily visible.
  • For those between the latitudes 23.5 deg. south (the tropic of Capricorn) and 23.5 deg. north (the tropic of Cancer) can experience the sun right overhead at Zenith - twice every year, once between December solstice (21st/22nd December) and June solstice (20th/21st June) and then between June solstice and December solstice.