What’s the coldest thing in the solar system?

 

Neptune’s moon Triton.

It gets as cold as -235°C. But that isn't what makes it so weird.

Neptune has 14 moons. With the exception of Titan, all the moons are very small, and come in two varieties— regular and irregular.

The regular ones orbit close to the planet, and irregular ones are generally farther from Neptune, with all sorts of crazy orbits..

And then there's Triton. It was discovered by amateur astronomer William Lassell, who, in 1846, spotted the moon a mere 17 days after the discovery of Neptune itself.

There are many reasons that make it strange.

For one, Triton is big. The 7th largest moon of Solar System. It’s over 200 times bigger than all the other moons of Neptune combined.

Second, it's one of the irregular moons, for it orbits the wrong way. It orbits backwards relative to Neptune’s spin, and orbit is almost perpendicular to its parent planet.

Third, it looks like a cantaloupe.Covered in bumpy, wrinkly features nicknamed cantaloupe terrain.

Fourth, it's actually no mere moon, but instead a victim of an interplanetary kidnapping.

Triton is likely a Kuiper belt object, like Pluto and Eris. Long ago, it fell into the vicinity of Neptune and got captured by the planet’s gravity.

Either Triton just got unlucky and had the exact wrong orbit to land itself near Neptune, or it suffered some collision with one of Neptune's own moons and losed enough energy to remain in orbit.

Sadly, it's future isn’t bright either. Due to tidal forces Triton’s orbit is decaying, and it's slowly spiralling into its doom. It’ll either crash into Neptune or will be ripped apart into a spectacular ring system— more dazzling than Saturn's..

Which is the biggest planet and smallest planet of our solar system?

 The largest planet in the solar system is Jupiter, and the smallest is Mercury.

…

Hah, you think I am just going to write some super short answer? Please, that’s just is not my style.

So, let’s start off with the smallest, and one of the coolest planets in my opinion:

Mercury!

Ahh, good ol’ Mercury.

Mercury is the smallest, and innermost planet of our solar system. It is quite similar to our very own Moon, both in looks and surface features. In fact, I like to look at Mercury as the inverted color version of the Moon, because the higher areas of Mercury are darker, and the deep craters are brighter (opposite of our Moon.) Some of these craters, in fact, are so deep, sunlight never reaches parts of those craters. And, in some of those craters, there is actually water ice, just hanging out. This is quite amazing, since the day time temperature on Mercury can reach several hundred degrees Fahrenheit.

Another really cool thing about Mercury is that it has an unusually large iron and nickel core for its size. Scientists think that the core makes up 85% of the planets entire radius. This also makes it the second densest planet, only behind the Earth. Scientists have two different theories as to why the core of Mercury is very large.

The first, and older theory is that Mercury had a collision with another planet when it was first forming, and this blew off most of the silicates and lighter stuff off of baby Mercury and the other planetoid, while also merging the two cores of the planets, making one smaller planet, but with a huge core.

The second, and more exciting theory is that Mercury, a long time ago, used to be a gas giant. But, as it got closer and closer to the sun, more and more of the gas was stripped away from the intense solar winds, until all that was left was a small, metallic core that most gas Giants have. This theory is really cool because it would make our solar system seem a bit more normal, since many other stars have gas giants that orbit really close in to its parent star, but ours does not. It is also a nice feeling to think Mercury used to be a giant once upon a time.

Now, for the largest planet in the Solar System:

Jupiter!

Jupiter is a lot different from Mercury, in almost every way imaginable. First of all, Jupiter is HUGE. Jupiter has a radius of 43,441 miles, compared to tiny Mercury, which only has a radius of 1,516 miles. This means that you could place 28 Mercury-sized planets next to each other, stretch them in a straight line above Jupiter, and Jupiter would still have a larger diameter. Jupiter also has a very thick hydrogen atmosphere, with a cloud layer 30 miles thick, before you reach a point inside Jupiter that is very bizarre.

Once you get past that cloud layer, the hydrogen is so dense now that it takes on a liquid form. But, this isn’t a cold liquid, but is extremely hot, like the molten parts of our planet, only made of hydrogen gas. Past this layer, the hydrogen continues to become more dense to the point it acts like a superheated metal. At this point, anything inside would be burnt beyond recovery, but if you were to send something down there, this is as far as you could get. Below the metallic layer of hydrogen, you have a small rock and ice core (similar to Mercury, actually).

Jupiter has the most moons in the solar system as well, counting 67 so far. Most of these moons are small asteroids that were caught by Jupiter’s immense gravity, but 4 of them, the Galilean moons, are quite unique. The closest one in is Io, which is one of the most volcanically active objects in our solar system, and its surface has a weird mix of colors. Europa has a huge water ocean underneath its thick icy crust, and it is a possible contender to support life because of that. Callisto has one of the oldest surfaces in the solar system, and Ganymede is the largest moon in the solar system, and is bigger than Mercury.

So, there you have it, the largest planet in our solar system, and the smallest, along with some cool details and theories about them. And no, Pluto doesn’t count, it’s classified as a dwarf planet, so leave it at that.

Is it safe to drink water during a solar or lunar eclipse?

 Scientifically, it is perfectly safe to drink water during a solar or lunar eclipse. The celestial events have no effect on the chemical or physical properties of water, and there's no scientific evidence to support the idea that water or food becomes "contaminated" or unsafe during an eclipse.

​Understanding the Science Behind Eclipses 🌑

​A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting a shadow on Earth. A lunar eclipse happens when the Earth passes between the Sun and the Moon, and the Earth's shadow falls on the Moon. These are purely astronomical events. The light and radiation from the sun are not different during an eclipse; the only change is the amount of sunlight that reaches us, which is blocked by the moon's shadow. The sun still emits the same electromagnetic radiation, which doesn't affect food or water on Earth.

Cultural Beliefs and Myths 📜

​The belief that it is unsafe to eat or drink during an eclipse is a cultural and traditional one, not a scientific one. In some cultures, particularly in parts of India, it is believed that the period of an eclipse, known as "Sutak," is inauspicious. During this time, people are advised to fast, avoid cooking, and not consume food or water. These beliefs are often rooted in ancient mythologies that describe eclipses as a time when negative cosmic energies are high, which could contaminate food and affect a person's health.

​The practice of placing tulsi (basil) leaves in food and water during an eclipse is also linked to these beliefs. While it is believed to have a symbolic purpose of purification and protection from negative energies, basil leaves are also known to have natural antibacterial properties, which may have served as a practical way to prevent bacterial growth in a time when refrigeration was not available.

​Ultimately, from a scientific standpoint, there is no harm in drinking water or consuming food during a solar or lunar eclipse. The decision to abstain is a matter of personal or cultural belief.

Mercury is the innermost planet of the Solar System.

 In particular, it is located 58 million km from our star, just over a third of the distance that separates the Earth from the Sun. At this distance corresponds a revolution period, the Mercurian year, of 88 days.

Like all other celestial objects, Mercury also rotates on its axis. Unlike other planets like Earth or Mars, Mercury rotates on itself very slowly, completing a full rotation every 59 days.

In the title of this post, I wrote that a day on Mercury lasts more than a year, but if math is objective, 59 is smaller than 88, so in theory, the year is the longer period of time between the two.

However, this depends on the definition we want to give to the word "day". If by day we mean the period it takes for a planet to complete one rotation on its axis, then a year on Mercury lasts more than a day. This definition is known as a sidereal day.

However, we could consider the day to be the time that elapses between two consecutive culminations of the Sun (that is, when the Sun passes the meridian and reaches its maximum height in the sky). This day is known as the solar day.

The solar day is longer than the sidereal day, since due to the revolution around the Sun the planet must rotate a little more to bring the Sun back to culmination compared to the previous day.

The difference between the two days on Earth is minimal, only 4 minutes. However, on Mercury, while the sidereal day lasts 59 Earth days, the solar day lasts a whopping 176 Earth days! This means that between two consecutive passages of the Sun in the same position in the Mercurian sky, a full 176 days pass!

Depending on the definition of day we choose, here is how on Mercury a day can last longer than a year.

Credit: NASA.

What is the weirdest moon in the solar system?

 I’m gonna go with Saturn's moon Iapetus.

(In Greek mythology, Iapetus is a Titan, a son of Uranus and Gaia, and the father of several well-known figures, including Atlas and Prometheus)

Take a look first

You're seeing this, right? That weird ring of mountain range around the Moon?

So here's what we know about this peculiar ring:

Its average height is 20 KM (about 12 miles), making it the third tallest mountain range in our solar system.

It circles the entirety of the Moon.

And it does so exactly around its equator.

And we haven't the faintest clue as to why.

There are hypotheses: Maybe Iapetus, just like Saturn, the planet it is orbiting, had rings. These rings may have gradually been grown to the moon and eventually crashed, forming the range.

Another suggests that iapetus turned around its axis in extremely high speeds, causing it to warm up and then for some reason slowed down, perhaps abruptly and as it was cooling off it's two halves sort of melted into each other creating this bulge.

Volcanic activity is probably not the answer because Iapetus has a very low density, only slightly greater than that of water ice. This indicates that it's composed predominantly of water ice with only a small fraction of rocky material (around 20%), so this pretty much takes volcanic activity off the list.

So what we can say with certainty is that we haven't got a clue.

But it's a heck of a question.

These photos by the way were taken in 2007 by the cassini probe.

Weird enough, right?

Wrong. It gets weirder. Let's zoom out.

This isn't shade or an area not facing the sun while the photo was taken - Iapetus is spllit into two drastically different hemispheres.

One hemisphere of Iapetus is extremely dark, almost as dark as coal, with a reddish-brown tint. The other hemisphere is remarkably bright, covered in ice, almost as reflective as Europa (one of Jupiter's moons).

The transition between these two very different terrains is quite sharp and distinct, resembling a "yin-yang" or the stitching on a baseball.

Scientists believe the dark material is accumulated dust and debris, primarily from another distant Saturnian moon, Phoebe. Iapetus is tidally locked to Saturn, meaning one side always leads in its orbit, effectively "sweeping up" this dark material like bugs on a car's windshield.

Why? Is that dust the explanation? 🤷 Don’t know.

What we do know is that the dark material absorbs more sunlight and heats up. This causes any ice in the dark regions to vaporize away, leaving behind even darker, carbon-rich residues. The vaporized ice then re-deposits in colder, brighter regions (like the poles or the trailing hemisphere), making those areas even brighter. This process, called thermal segregation, intensifies the already existing color contrast.

Well, a mountain range on the equator and two tones. strange enough!

Nope.

It keeps getting stranger.

Look again:

Iapetus has a weird shape.

It’s oblate Spheroid, but… it's not supposed to be.

Iapetus is oblate spheroid, meaning it's flattened at the poles and bulges at the equator, which is common for rotating bodies (like Earth, which bulges slightly at its equator due to its spin).

So that would work with a moon that would have been spinning much faster in its early history, with a rotation period of only about 16 hours.

But Iapetus is currently tidally locked with Saturn, rotating once every 79 Earth days…

This means Iapetus somehow froze its shape when it was spinning rapidly and then later slowed down its rotation drastically, but its rigid crust retained its original, faster-spinning form. How it slowed down so quickly, given its distance from Saturn, is a subject of debate.

To explain, Iapetus orbits much farther from Saturn than the other major inner moons (like Titan, Rhea, Dione, Tethys, Enceladus, Mimas) and this didn't happen to them.

Well, at least the Orbit is not weird! …is it?

Of course it is.

Most of Saturn's moons orbit pretty much around its equator.

But not Iapetus (of course). Iapetus has a 15 degree inclination, that means sometimes it’e moving up above the equatoral orbit, and sometimes down below it.

Because why not?

The combination of its two-tone surface, the inexplicable equatorial ridge, its "fossil" shape indicating a past rapid spin, and its unusual orbit truly makes Iapetus one of the most mysterious and captivating objects in the solar system. Scientists are still actively researching and debating the origins of these bizarre features.

Iapetus isn't just the weirdest moons in our solar system, in my humble opinion. It's probably one of the weirdest places in our solar system, period.

I think it's awesome.

What would happen if a star 'touched' the solar system?

 

You wake up one morning, turn on the TV, and there is a sci-fi film about people panicking because our Solar System is about to be hit by another star. You hate such movies. You change channels, but surprisingly, there is the same story on other channels as well. It was not fiction at all. It was happening for real. A hypervelocity brown dwarf star about 13 times as massive as Jupiter, approaching at 4% of the speed of light, has only been noticed because such suns can be even at room temperature, and some don't shine much. It will touch our Sun as it will fly by our system in just a few hours.

This violent side collision would shave off a bit of our star. The immense amounts of powerfully ejected matter would blast through the whole Solar System and furiously crash into planets. If the doomed Earth survived at all, it would be ruthlessly resurfaced and changed into liquid magma in which our ruined cities would submerge. The surface would cool again only millions of years later. This would spell the end of our forsaken civilization and possibly even life on our planet. Counterintuitively, the reduction of the mass of our Sun would extend its life by hundreds of millions to billions of years and make the orbits of the surviving planets expand because of the lower gravitational grip on them. Less massive stars have longer lifespans significantly. The blasted matter would eventually settle into a disk in which new planets could form as new neighbors to the ones that survived this surreal armageddon.

And surreal it would be, literally, because it would not be likely to happen. The distances between stars in our part of the galaxy are just too vast. A star touching another star system in our location in the Universe means something else. It would just be an approach that might disrupt some asteroids in the Oort Cloud, resulting in some comet strikes on planets. Infinitely rarely, stars can approach each other somewhat closer. This can result in their planetary systems becoming unstable. Some worlds can change orbits, collide, fall into one of the stars and be destroyed, or some can be ejected and become rogue planets.

Stars occasionally collide directly in some dense clusters of stars and in the galaxy's central bulge. There is evidence of it because blue straggler stars have been detected in these locations. They formed via the collisions of stars. They are brighter, and their light is bluer than similarly massive stars that formed in a usual way. If suns collide at a very high speed, they can dissipate and become gas clouds. If they hit each other at an angle, they might start revolving around their common center of mass, the barycenter, ever closer until even billions of years later when they might collide. Such impacts can expel massive amounts of matter, forming a protoplanetary disk where new worlds can coalesce.

Why is Pluto no longer considered a planet?

 The reason that Pluto is no longer a planet is not because of its size. In fact, it passes the test for "size" (mass).

The definition of 'planet' was made more strict. It is as following:

1. Massive enough to be round. Very massive bodies have so much gravity that they crush down any irregular edges towards their centre, and so become ball-like.

2. The primary object orbiting the Sun. For instance, the Moon orbit's the Sun, but it does so by orbiting the Earth. The Earth is the primary object orbiting the Sun.

3. Has cleared it's own orbit. Planets clear their orbits of debris/asteroids (by attracting them with their gravity).

Pluto passes 1 and 2, but has not passed 3. It has not cleared it's orbit of debris.

Objects like Pluto are called Dwarf Planets.

Are all the planets in the solar system formed (almost) at the same period?

 The gas giants are first generation planets and were formed 4.6 billion years ago: first Jupiter and Saturn, then Neptune and Uranus.

Jupiter is said to be the oldest planet in the solar system and was formed shortly after the Sun. It would have been followed by Saturn.

We know this because unlike Uranus, Neptune and the rocky planets, Jupiter and Saturn are rich in helium and hydrogen.

By the time the other planets were formed, much of the hydrogen and helium in the primordial cloud in the solar system had disappeared. Jupiter and Saturn are representative samples of this cloud.

Among the rocky planets there are first, second and perhaps third generation planets.

According to the "giant impact hypothesis", the Earth is a second generation planet formed by a collision between rocky planets of the primitive solar system, Gaia and Theia.

These two planets collided 4.468 billion years ago, more than 100 million years after their formation.

The hypothesis proposes that Theia was formed at a Lagrange point of the Gaia-Sun system, at the same distance from the Sun as Gaia, but forming with them an equilateral triangle.

After Theia had reached the current size of Mars, 6,500 km in diameter, the other planets would have destabilized it and caused its collision with Gaia.

Theia would have struck Gaia at a speed of 40,000 kilometers per hour at an oblique angle, ejecting portion of both Theia and Gaia into space and creating a ring of debris around the new Earth. By accretion, between one and a hundred years later, half of this debris would have given birth to the Moon.

Mercury would also be a second generation rocky planet. Indeed the core of Mercury has a higher iron content than that of any other planet.

Mercury would have been formed by collision between an ancient planet of approximately 2.25 the current mass of Mercury and a planet of approximately 1/6 of this mass. The impact would have removed much of the mantle of the old planet, leaving the core behind at the base of the formation of Mercury.