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Cosmic discoveries are essential as they push the boundaries of our knowledge about nature and offer opportunities to challenge reality using mathematical models. Here are 10 extraordinary objects that test the limits of both our calculations and imagination.
10. The Smallest Planet Ever Found
Earlier this year, the Kepler Observatory uncovered a star system with three planets, including the tiniest exoplanet ever discovered. Positioned in space, the Kepler telescope enjoys a clear view of the stars, unimpeded by the Earth's atmosphere. Known as Kepler 37-b, this minuscule planet is smaller than Mercury and only about 200 kilometers (124 miles) larger in diameter than Earth's Moon. Unfortunately, it resides just beyond the point where Pluto lost its planet status.
One of the primary methods astronomers use to identify exoplanet candidates is by observing the dimming of a star’s light, caused when a planet passes in front of it. This dimming is more noticeable with larger planets. Most exoplanets discovered so far are significantly larger than Earth, often about the size of Jupiter. The dimming caused by Kepler 37-b, however, would be nearly impossible to detect without precise measurements, making its discovery truly extraordinary.
9. The Milky Way’s Mysterious Fermi Bubbles
When seen flat, the Milky Way galaxy appears vast and sprawling, as depicted in most illustrations. However, when viewed edge-on, it seems much thinner and less impressive. That is, until we observed it in the most extreme wavelengths: X-rays and gamma rays.
The Fermi Bubbles extend vertically from our galaxy's disc and span a staggering 50,000 light-years—roughly half the Milky Way's diameter. While NASA isn't entirely certain about their origin, these bubbles may be remnants of emissions from the supermassive black hole at the center of our galaxy, as gamma radiation is associated with extraordinarily high-energy events.
8. Theia: The Giant That Shaped Our Moon
More than four billion years ago, the early Solar System was a chaotic and dangerous place, filled with planetoids at various stages of development. Our cosmic neighborhood was littered with chunks of rock and ice, resulting in frequent collisions. One of the largest of these impacts is central to one of the most widely accepted theories about the Moon's formation. A Mars-sized object, known as Theia, collided with primordial Earth at a precise angle. The debris left behind is believed to have gathered inside Earth's orbit, eventually forming the Moon.
Had the impact been even slightly different—closer to the poles or the equator—the outcome could have been drastically altered, and the early Earth might have been completely destroyed.
7. The Sloan Great Wall
The Sloan Great Wall is incredibly vast, stretching beyond what we can easily comprehend, especially when we try to compare it to familiar sizes. This colossal structure ranks among the largest in the universe, consisting of a massive chain of galaxies that extend for 1.4 billion light-years.
It holds hundreds of millions of individual galaxies, most of which are part of larger superclusters within the structure. These clusters seem to have formed in regions with varying densities, a consequence of the Big Bang, and can be observed in the cosmic microwave background.
Some experts argue that the Sloan Great Wall should not be viewed as a single entity, as not all of the galaxies within it are gravitationally linked to each other.
6. The Smallest Black Hole
Nothing in the universe strikes as much awe and fear as the immense black hole. In video game terms, it’s the ‘final boss’ of the cosmos. Its gravitational force is so strong that it can trap light itself, which travels at nearly 300,000 kilometers per second (186,000 mi/s). While we’ve discovered massive black holes weighing billions of times more than our Sun, we’ve now encountered one that is surprisingly small.
The previous smallest black hole weighed about 14 times the mass of the Sun, which is enormous by our standards. However, the new discovery, IGR, is only around three times as massive as the Sun. It’s just about the minimum mass needed to cause a star to collapse in on itself when it reaches the end of its life. Any smaller and it would have followed a path similar to that of our Sun—gradually expanding and shedding its outer layers before dispersing most of its material into space.
5. The Smallest Galaxy
Galaxies are massive—vast collections of stars shaped by nuclear forces and gravity. Their immense size and brilliance make many of them visible to the naked eye, even from vast distances. Because of this, it’s easy to overlook the fact that some galaxies are at the opposite end of the scale, being much smaller in comparison.
‘Segue 2’ is a prime example of how something small can surprise us, containing only around 1,000 stars. For comparison, our own galaxy contains hundreds of billions of stars.
The total output of Segue 2 is about 900 times that of our Sun, which is fairly modest given that our Sun isn’t particularly large or remarkable on a cosmic scale. As telescope technology advances, we may uncover more hidden gems like Segue 2, which is exciting for astronomers since galaxies of this size had been predicted but never directly observed until recently.
4. The Largest Impact Crater
For years, scientists have debated what caused the stark difference between the two hemispheres of Mars. One relatively recent theory suggests that this asymmetry was the result of a massive catastrophic impact that reshaped the planet. The Borealis Basin, which holds clues to Mars’ violent history, is the largest known crater in the Solar System, covering roughly 40 percent of the Martian surface—spanning an area of 8,500 kilometers (5,300 miles). The second largest crater, also on Mars, is four times smaller.
To have created such a colossal crater, the ancient impact must have been of an extraordinary scale, with the object responsible believed to have been larger than Pluto.
3. Lakes on Titan
As spring began to emerge and winter clouds retreated, the Cassini spacecraft captured stunning images of the lakes scattered across Titan’s northern polar region. While liquid water cannot exist on this distant moon, the temperatures are just right for liquid methane and ethane to flow freely, emerging from the moon’s interior.
Curiously, this is the first time that the clouds on Titan have cleared enough to provide a clear view of the pole, despite the Cassini probe orbiting the moon since 2004. The largest lakes span hundreds of miles, with Kraken Mare being the largest, comparable in size to ‘the Caspian Sea and Lake Superior combined.’
While liquid environments were crucial for life to form on Earth, seas filled with hydrocarbons present a completely different scenario, as materials do not dissolve in hydrocarbons in the same way they do in water.
2. An Incredibly Ancient Quasar
Some black holes are extraordinarily massive, which makes sense since they devour anything that crosses their path.
ULAS J1120+0641, with a mass two billion times that of the Sun, caught astronomers off guard—not so much because of its size, but due to its astonishing age. This quasar is the oldest ever discovered, having formed less than 800 million years after the Big Bang. This means the light from it has been traveling across the cosmos for 12.9 billion years before reaching Earth. The reason for its immense size is unclear, as there was very little for the black hole to feed on in such the early universe.
1. The Closest Perihelion in the Solar System
Although Mercury is the closest large planet to the Sun, smaller objects can venture much closer. Perihelion refers to the closest point in a body’s orbit to the Sun, and asteroid 2000 BD19 has the tightest orbit, coming dangerously close to the Sun. At just 0.092 astronomical units (about 1/10th the Earth-Sun distance), HD19 gets incredibly hot, reaching temperatures that could melt metals like zinc.
Studying asteroid 2000 BD19 is crucial for understanding how various forces can alter an object’s orbit. One such force is Einstein’s renowned theory of general relativity, and by observing this near-Earth asteroid, we can better understand how this theory plays out in real-world conditions.
