Universa:Let's Explore More

Why is there a monster black hole in the heart of every galaxy?

There are about two trillion galaxies in our Universe and, as far as we know,almost every one contains a central supermassive black hole. They range
in size from monsters, weighing almost 50 billion times the mass of the Sun, to the 4.3-million-solar-mass tiddler known as Sagittarius A in the core of
our Milky Way (one solar mass = mass of our Sun). But how they got there is one of the great unsolved mysteries of cosmology. We know that a stellar
black hole forms in a supernova explosion in which the core of a star implodes. But nobody knows how a supermassive black hole forms. For most of
cosmic history, the centres of galaxies have been where a lot of matter is confined in a small volume. It could be the case that supermassive blackholes
form in a dense star cluster out of stellar black holes which repeatedly merge with each other. Tentative evidence for this comes from a merger
between two black holes revealed by a detection of gravitational waves. One hole was too big to be a supernova relic and so may have originated in an earlier merger.



The Moon’s Magnetic Field

One of the moon’s greatest mysteries—why only some parts of the crust seem to have a magnetic
field—has intrigued astronomers for decades, even inspiring the buried mythical “monolith” in the novel and
film 2001: A Space Odyssey. But some scientists finally think they may have an explanation.
After using a computer model to analyze the moon’s crust, researchers believe the magnetism may be a
relic of a 120-mile-wide asteroid that collided with the moon’s southern pole about
4.5 billion years ago, scattering magnetic material. Others, though, believe the magnetic field may be related to
other smaller, more recent impacts.



What Is Dark Matter?

Astrophysicists are currently trying to observe the effects of dark energy, which accounts for some
70 percent of the universe. But it's not the only dark stuff in the cosmos: roughly 25
percent of it is made up of an entirely separate material called dark matter. Completely invisible to telescopes
and the human eye, it neither emits nor absorbs visible light (or any form of
electromagnetic radiation), but its gravitational effect is evident in the motions of galaxy clusters and individual stars. Although dark
matter has proven extremely difficult to study, many scientists speculate that it might be composed of
subatomic particles that are fundamentally different from those that create the matter we see around us.



How Will the Universe End?

We now believe the universe started with the Big Bang. But how will it
end? Based on a number of factors, theorists conclude that the fate of the universe could take
one of several wildly different forms. If the amount of dark energy is not enough to
resist the compressing force of gravity, the entire universe could collapse into a singular
point—a mirror image of the Big Bang, known as the Big Crunch. Recent findings, though, indicate a
Big Crunch is less likely than a Big Chill, in which dark energy forces the
universe into a slow, gradual expansion and all that remains are burned-out stars and
dead planets, hovering at temperatures barely above absolute zero. If enough dark energy is present
to overwhelm all other forces, a Big Rip scenario could occur, in which all galaxies, stars
and even atoms are torn apart.



What happened to Pluto?

In 2006 the International Astronomical Union (IAU) demoted the much-loved Pluto from its position as the
ninth planet from the Sun to one of five “dwarf planets.” The main event of the
2006 General Assembly of the IAU, the proposal that would come to demote Pluto, was a defining
moment for the rest of the solar system as well. Fiercely debated by the members of
the union, the resolution that was passed officially defined the term planet. What was once
a loose word used to describe a large object within the solar system was now specific: planets
are celestial objects large enough to be made rounded by their gravitational orbit around the Sun and
to have shooed away neighboring planetary objects and debris. Pluto is now classified as a dwarf planet because,
while it is large enough to have become spherical, it is not big enough
to exert its orbital dominance and clear the neighborhood surrounding its orbit.



The Big Bang Theory

The Big Bang theory is the prevailing scientific explanation for the origin of the universe.
It posits that the universe began from an extremely hot and dense state around
13.8 billion years ago and has been expanding ever since. Initially, the universe was a
singularity, an infinitely small and dense point. As it expanded, it cooled down, allowing for
the formation of particles, light elements, and eventually atoms. The release of cosmic microwave
background radiation provided crucial evidence for the theory. Over time, gravity caused
matter to clump together, forming galaxies and other cosmic structures. The Big Bang
theory successfully explains the observed redshift of galaxies, the abundance of light elements,
and the large-scale structure of the universe.