Outer Space: Top 5 Unsolved Mysteries in the Universe

Liputan6.com, Jakarta - The vast and boundless Outer Space continues to present puzzles that challenge human understanding.

Although advances in technology and astronomical research have opened up many new insights, there are still many phenomena in space whose existence is palpable yet their nature remains mysterious.

Scientists around the world continue to strive to unravel these cosmic secrets.

Exploring these mysteries not only expands our understanding of the cosmos but also challenges existing theories of physics.

Dark matter is a mysterious, invisible and hypothetical type of matter that does not interact with light or other electromagnetic radiation, estimated to make up about 27% of the universe, far more than ordinary matter, which only makes up about 5%.

Dark matter does not absorb, reflect, or emit light, making it extremely difficult to detect directly.

Scientists first inferred the existence of dark matter in 1933 when astronomer Fritz Zwicky observed that galaxies in the Coma cluster were moving too fast for the gravity exerted by ordinary, visible matter.

This suggested the presence of invisible matter holding the galaxies together.

The most common explanation is that dark matter is an as-yet-undiscovered subatomic particle, such as Weakly Interacting Massive Particles (WIMPs) or axions.

Dark energy is a proposed form of energy that affects the universe on the largest scales, estimated to account for about 68% of the total energy in the observable universe today.

The discovery of the universe's accelerating expansion in the late 1990s, through observations of Type Ia supernovae, suggested that an unknown force was causing the universe to expand faster over time.

Before this discovery, scientists thought that the gravitational pull of matter and energy in the universe would cause the universe's expansion to slow down over time.

Dark energy is the name scientists give to whatever is causing our universe to expand at an accelerating rate over time.

This remains one of the unsolved cosmic mysteries in space.

Fast radio bursts (FRBs) are extremely intense, transient radio waves lasting milliseconds, caused by high-energy astrophysical processes that are not yet fully understood.

FRBs were first discovered in 2007 by American astronomer Duncan Lorimer, and they became known as "Lorimer Bursts."

Despite being highly energetic at their source, the signal strength reaching Earth has been described as 1,000 times weaker than that from a cell phone on the Moon.

The exact cause and origin of FRBs remains the subject of intense investigation.

Proposed candidates include compact stellar remnants such as neutron stars and magnetars, which are highly magnetic types of neutron stars.

The Great Attractor is a region of gravitational pull in intergalactic space and the apparent central point of gravity of the Laniakea Supercluster, includes the Milky Way galaxy and approximately 100,000 other galaxies.

This region is located between 150 and 250 million light-years from the Milky Way, in the direction of the constellations Triangulum Australe and Norma.

The existence of the Great Attractor is inferred from its effect on the motions of surrounding galaxies, suggesting that these galaxies are moving toward a massive gravitational focus.

Despite having a mass equivalent to tens of thousands of galaxies, the Great Attractor is difficult to observe directly because it is obscured by the plane of the Milky Way galaxy, known as the Zone of Avoidance.

The ultimate fate of the universe depends heavily on the nature of dark energy, which remains a major mystery in space.

Each scenario offers a different view of how the cosmos will end.

• Heat Death / Big Freeze: The universe will continue to expand indefinitely, gradually cooling over time where stars will exhaust their fuel, galaxies will drift apart, and the universe will become dark and empty.
• Big Rip: If dark energy is a form of "ghost energy" with an equation-of-state parameter w < -1, the universe's expansion will accelerate faster and faster until it rips everything apart.
• Big Crunch: This scenario is the opposite of the Big Bang when dark energy weakens or reverses, gravity could eventually halt and reverse the expansion.