Which is the scariest planet?

 In terms of hospitality?

So HD 189733b is probably a planet you wouldn't want to be on.

Located about 64.5 light-years from Earth, this planet is about 13% larger than Jupiter.

Besides, it can hold a little over 1400 Earths, and it has a pretty hot temperature of around 1800°C (3272°F) at times. To give you some perspective, iron melts at 1535°C or 2795°F, so you don't stand much chance of survival.

And that's not the most interesting part about this exoplanet.

If you happen to survive its extremely hot atmosphere, then you will be able to experience another of its main attributes: the wind speed.

With a speed of approximately 5,400 miles per hour (8,690 km/h), its wind speed is the fastest recorded on any planet. The wind is capable of reaching seven times the speed of sound.

The best part is that the winds bring silicate particles and sometimes it rains molten glass.

In short, HD 189733b is a place you wouldn't want to be.

Why do we have so few real photos of planet Earth?

 For a very long time, there were very few photos of planet Earth showing a fully illuminated hemisphere. The reason is relatively simple: to get a photo of an entire hemisphere of the Earth, you have to be far enough away from Earth, and you have to be positioned between the Sun and the Earth.

If you are too close to Earth, like the astronauts on board the International Space Station, at an altitude of about 400 km, you do not see the entire globe, but only a portion: it is then impossible to take a picture of the planet Earth.

Earth photographed from the ISS, with a Soyuz spacecraft (foreground) and a Progress cargo ship (background). While the photo is magnificent and the Strait of Gibraltar is clearly visible, Earth is nowhere to be seen. Credits: NASA

Conversely, the majority of satellites located far from Earth are rarely situated exactly between the Sun and the Earth, which results in photos of crescent Earths: these photos are sublime too, but they do not show the Earth in its entirety.

Photograph of an Earthrise taken during the Apollo 8 mission. The Earth is not shown in its entirety, but rather a crescent shape. Credits: NASA

The consequence is simple: for a long time, the vast majority of images of the Earth were composites of different photos, in order to present an illuminated hemisphere of the Earth.

In practical terms, this means that several photographs of the Earth from space were retrieved, each being a crescent of the Earth for example, showing an illuminated area of ​​the globe, and these photographs were cut out and pasted together, then the colors were reworked so that the seams would not be visible.

To have continuity in the clouds, I suppose the photographs came from satellites that photographed the Earth at relatively short intervals, but I'm not sure.

Note: This does not mean that all photos were composed this way. One of the most iconic photographs of the Apollo era is a photograph showing the Earth fully illuminated. This photo, titledBlue MarbleThe Blue Marble, or the 80-degree blue marble, is one of the most reproduced images in the world. And it was possible because the astronauts had the Sun behind them at that moment.

Blue Marble: the famous photo taken by the crew of Apollo 17 in 1972, the last mission to the Moon, is not a composite image but a single photograph of our planet Earth. Credits: NASA

Much more recently, NASA launched a climate observation satellite, simply calledClimate Observatory from Deep Space, in EnglishDeep Space Climate Obervatory, abbreviated as DSCOVR. It positioned itself approximately 1 million kilometers from Earth, at the L1 Lagrange point of the Earth-Sun system: in practical terms, this means, among other things, that the satellite is permanently located between the Sun and the Earth. And one of its instruments, the EPIC camera, regularly takes pictures of Earth, thus showing photographs of the fully illuminated Earth.

First image of North and Central America returned by the DSCOVR satellite on July 6, 2015. Credits: NASA/EPIC Team

There are several things to know about these photographs.

First, these are not actual photographs as they were taken. In fact, the EPIC camera has several filters, 10 to be exact. Among these filters, several are used for the photographs of Earth seen here: a red filter, a blue filter, and a green filter. Specifically, EPIC takes three photos with very little time between them.

These images are taken in black and white: with a red filter, for example, a white area will be an area where there is a lot of red light, and a black area is an area where there is no red light reflected by the Earth.

These 3 photos are then changed in color to match what they represent: thus, on a photo taken with a red filter, white areas become red, black areas remain black, and shades of grey become shades of red.

Then the three photographs—red, blue, and green—are stacked to create a color image. Incidentally, this type of process is often used for pixel colors in computers, with RGB components.

This can also be seen in some photos, particularly the incredible photographs of the Moon's transit. By zooming in on the Moon's outline, one can often see either a thin green band or a thin red band, because the Moon has moved slightly between the photos: the Moon was positioned in one place during the photo under the green filter and was slightly off-center in the following two, leaving a thin green band in the area that was only covered by one photo.

Photograph of the Moon's transit taken by the EPIC camera aboard the DSCOVR satellite. Zooming in on the Moon, a very thin blue band can be seen on the left, and on the right, two thin red and green bands, remnants of the three superimposed photographs. Credits: NASA/EPIC Team

And that's not all! The images are also processed to correct some distortions, and the colors are then reworked to achieve a rendering similar to what the human eye would perceive.

The EPIC team is also working on color images.augmentedto account for what would be visible without the attenuation of the atmosphere.

What are the unsolved mysteries of our planet and space?

 

• MH370
  What happened to the plane that vanished without a trace?

A crewman on a Royal New Zealand Air Force P-3 Orion Rescue Flight 795 searches for debris from the missing Malaysia Airlines Flight MH370 on April 1.

A Malaysia Airlines flight vanished without a trace while en route from Kuala Lumpur to Beijing on March 8. The weather was clear and there was no distress signal from the cockpit when the plane disappeared from radar screens.

After more than nine months, not a single piece of debris from MH370 has turned up. Despite numerous conspiracy theories we still don't know what happened to the plane. All 239 people on board are presumed dead.

• Pollock Twins

A story from 1957 about supposed reincarnation, two girl sisters 11 and 6 years old killed in a car accident in England, with their mother giving birth to twins the following year

One of the twins bore the exact same birth marks as her deceased sister in exactly the same places, and it got spookier when the girls requested exactly the dead sisters’ toys which they couldn’t possibly have known about

They also asked to be taken to places they’d never heard of, like a park the departed sisters had been too.

• Bermuda Triangle

Known as the Bermuda Triangle, this legendary expanse of ocean can be found between the points of Miami, Bermuda, and Puerto Rico. Pilots often tell of their instruments going haywire and numerous ships have been lost at sea. With explanations ranging from gas bubbles to aliens, no one is sure what is behind the strange phenomena.

• Tamam Shud

Back in December 1948, an unidentified man was found dead in Somerton Beach, located in Adelaide, Australia. Found in one of his pockets was a piece of paper with the words “Tamam Shud” written on it. The words were translated “finished” or “ended” based on excerpts found in The Rubaiyat of Omar Khayyam. Although governments around the world have tried to identify the man his identity has remained mystery.

• Georgia Guidestones

Also identified as the American version of Stonehenge, the Georgia Guidestones located in Elbert County are shrouded in mystery, although they were erected only in 1979. Written on the walls are 10 “new commandments” written in English, Swahili, Hindi, Hebrew, Arabic, China, Russia, and Spanish although no one is sure why or for whom they were meant.

• Bigfoot

Also known as Sasquatch, bigfoot is supposedly a creature that lives in the snowy mountainous regions of the United States and Canada. It may be identified as a gorilla at first, however, its walking posture can be compared to that of a man’s.

• Black Dahlia Murder

22-year old Elizabeth Short was very active at promoting herself into showbiz at the time the Black Dahlia murder occurred, however, no one knew of the killer or who actually did the murder.

• Stonehenge

While Stonehenge is a very fascinating structure due to the big rocks that stand atop one another, the biggest mystery isn’t how it was created but why.

• Severed Foot Beach in British Columbia

is not uncommon for bodies to wash up on beaches but for one beach in British Columbia severed feet have consistently been floating ashore for the past several years causing numerous theories to be put forth.

• DB Cooper

When DB Cooper hijacked a Boeing 727 along with $200,000, he proceeded to jump out of the plane with a parachute. He was never found, however, and this remains the only unsolved case in US aviation history.

• SS Ourang Medan

What happened to SS Ourang Medan or “Man from Medan” in Malaysia is perhaps one of the most fascinating and mind-boggling mysteries that ever existed in seafaring history. Everything began with an SOS message in 1947 that mentioned the captain, along with the rest of the crew, was dead. What’s worse, even the telegrapher died during the transmission of the message. When the Silver Star was able to receive the distress call and went to inspect the ship, they confirmed the deaths of all aboard. Speculations of ghosts, hazardous chemicals, and even aliens have been raised, but there is still no conclusion as to what actually happened.

footnote- 25 Greatest Unsolved Mysteries

What is the creepiest planet in the universe?

 It's 2M1207b.

This gigantic planet (with about four times the mass of Jupiter) lies 170 light-years from Earth, and its distinctive atmosphere is hellish. Temperatures can reach 1400 degrees Celsius, and its rotation speed is astonishing (it completes one rotation in 10 hours compared to Earth's 24 hours, which is remarkable considering it's about 4000 times the size of Earth). And in the planet's stratosphere, highly sophisticated chemical reactions occur, causing glass droplets to rain down on its surface, so sometimes the rain contains not only glass but also molten iron and other materials.

Could humans survive on another planet without a spacesuit?

 If you step onto another planet without a spacesuit, suffocation is the least of your worries. In our solar system alone, you could be crushed, melted, or have your blood literally boil.

Venus offers a crushing atmospheric pressure 90 times that of Earth, temperatures hot enough to melt lead, and rains of sulfuric acid. Mars visually resembles an arid terrestrial desert, but its environment is just as lethal.

A view of the sandy, rocky surface inside Jezero Crater on Mars. Source: Wikimedia Commons.

Standing on this barren surface without a pressurized suit, a human would face an atmosphere 100 times thinner than Earth's, composed almost entirely of carbon dioxide. They would quickly succumb to ebullism—a condition where the boiling point of bodily fluids drops below the body's internal temperature, causing the water in tissue and blood to vaporize. Asphyxiation would follow in minutes. Gas giants like Jupiter and Saturn lack solid surfaces entirely, offering only a descent into crushing pressure and turbulent storms.

To survive without a spacesuit, a person would need an Earth-like exoplanet located in its star's habitable zone—the orbital region where temperatures allow liquid water to pool. This hypothetical planet must meet strict criteria: surface gravity close to 1G, a magnetic field to deflect stellar radiation, and a breathable atmospheric pressure. Crucially, the atmosphere must contain enough oxygen to sustain human metabolism without being so rich that it becomes highly flammable, mixed with an inert buffer gas like nitrogen.

Even if astronomers identify a planet with the perfect temperature and atmospheric composition, the biological reality of stepping outside remains hazardous. On Earth, free oxygen is continuously replenished by photosynthetic life. If an exoplanet has a breathable oxygen atmosphere, it likely harbors its own biosphere. A human arriving on such a world without a spacesuit might face alien microorganisms, allergens, or protein structures that the human immune system is completely unprepared to handle, making the alien air fatal for entirely biological reasons.

An artist's concept of Kepler-186f, an Earth-size exoplanet orbiting within its star's habitable zone. Photo by NASA Ames/SETI Institute/JPL-CalTech. is licensed under CC BY 4.0.

Can you explain how gravity works on a spherical planet?

 Gravity doesn't actually pull you "down." You are locked in a tug-of-war with every speck of dust and chunk of rock on Earth, being yanked in billions of directions at once.

Every atom in the planet exerts a tiny, invisible pull on your body. Because the Earth is a sphere, the rock thousands of miles to your left is pulling you to the left, and the rock thousands of miles to your right is pulling you to the right. The pull from the northern hemisphere cancels out the pull from the southern hemisphere. The only direction that doesn't get canceled out is the straight path toward the center of the planet.

In 1687, Isaac Newton proved this mathematically with what is now called the Shell Theorem. He showed that for any uniform sphere of matter, all the individual gravitational pulls from every particle add up perfectly to simulate a single point of mass at the exact center. As far as physics is concerned, the gravitational pull you feel on the surface is exactly the same as if all of Earth's mass were concentrated into a microscopic dot at the core.

This geometry means "down" is not a fixed direction in space, but simply a local vector pointing toward the center of mass. A person standing in Australia and a person standing in Canada are both pointing their feet toward the same central point without either of them "falling off."

Gravity is also the reason planets are spherical in the first place. Once a rocky body in space reaches a certain mass—usually about 400 miles across—its gravitational pull becomes so strong that it crushes its own material inward. The solid rock behaves like a slow-moving liquid, collapsing under its own weight until all matter is as close to the center of gravity as geometrically possible.

The 'Blue Marble' photograph taken by the Apollo 17 crew in 1972. Earth's gravity pulls its matter inward from all sides, molding it into a sphere over billions of years. Source: Wikimedia Commons.

How close are we to discovering another habitable planet?

 Astronomers have already discovered dozens of "habitable" planets. The catch? Many of these promising worlds are actually bare, irradiated rocks blasted by violent solar flares.

The "habitable zone"—often called the Goldilocks zone—simply refers to the orbital distance from a star where temperatures allow liquid water to exist on a rocky surface. Researchers have identified several promising Earth-sized candidates in these zones, such as Proxima Centauri b, located just four light-years away, and the seven-planet TRAPPIST-1 system.

However, discovering a planet's orbit is only the first step. The current hurdle is proving these worlds actually have atmospheres and water. Most of the best candidates orbit M-dwarf stars (red dwarfs). While these stars are the most common in the galaxy, they are highly volatile and prone to the exact type of magnetic activity that strips away a nearby planet's atmosphere over billions of years.

Scientists are currently using the James Webb Space Telescope (JWST) to analyze these worlds, and the initial results highlight the immense difficulty of the task. JWST observations of the innermost planets in the TRAPPIST-1 system—TRAPPIST-1b and c—suggest they completely lack substantial atmospheres. Hope remains for planets further out in the system, like TRAPPIST-1e, but extracting clear atmospheric data is incredibly challenging because the star's own magnetic activity often mimics or obscures the chemical signatures instruments are looking for.

To actually confirm a habitable planet—one with an atmosphere, water, and perhaps biosignatures like oxygen and methane—astronomers need next-generation tools. NASA is currently developing the Habitable Worlds Observatory (HWO), a flagship mission targeted for the 2040s. Instead of analyzing silhouettes as planets pass in front of their stars, HWO will use advanced coronagraphs to block out starlight. This will allow the telescope to directly image approximately 25 potentially habitable worlds and scan them for the chemical signatures of life.

While scientists have mapped the locations of the most promising interstellar neighbors, definitive proof of an alien atmosphere capable of supporting life is likely waiting on the technology of the 2040s.

An artist's illustration of Kepler-186f, an Earth-sized exoplanet discovered in its star's habitable zone. Photo by Jack Madden is licensed under CC BY-SA 4.0.

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Is a planet's gravity directly proportional to its mass?

 Uranus has 14.5 times the mass of Earth. Yet if you could somehow stand on its cloud tops, you would actually weigh 11% less than you do right now.

A planet's surface gravity is not determined by mass alone. According to Newton's law of universal gravitation, the gravitational force you feel on a planet's surface depends on two variables: the planet's mass and its radius. While gravity is directly proportional to mass, it is inversely proportional to the square of the radius. This means the distance from the center of the planet matters significantly more than the sheer amount of matter it contains.

When a planet gains mass, its physical size usually increases as well. If a planet's radius grows, you are pushed further away from its center of mass. Because the radius is squared in the gravity equation, a large increase in volume can easily overpower a substantial increase in mass.

Saturn is a perfect example of this dynamic. The gas giant contains 95 times more mass than Earth. However, because it is composed mostly of hydrogen and helium, it is far less dense, giving it a radius more than nine times that of Earth. Since you would be so far from Saturn's center of mass, its surface gravity is only 10.44 m/s²—barely stronger than Earth's 9.8 m/s².

This mathematical relationship is also why ultra-dense cosmic objects possess such extreme gravitational pulls. A neutron star has roughly the same mass as the Sun, but it is compressed into a sphere just 20 kilometers across. Because the radius is incredibly small, the surface gravity is billions of times stronger than Earth's. Ultimately, surface gravity is a contest between how much mass a celestial body has and how closely you can stand to the center of it.

Uranus contains significantly more mass than Earth, but its larger radius means its surface gravity is actually weaker. Source: Wikimedia Commons.

Would it be possible for a planet of giants to exist?

 Yes, but you’d need very specific conditions.

Lower gravity, abundance resources, food, and water.

The lower gravity part is important because it becomes more difficult for life to support its own mass as gravity goes up.

This is because of the square-cube trap. As an animal doubles in linear size, it’s volume multiples by eight. It’s leg bones only become four times stronger in this process.

This is, in part, why you see larger animals (like elephants and giraffes) having a much more lumbering gait and movement. They aren’t agile at all and are only just strong enough to support their weight. Whereas you compare this to ants—which are breathtakingly strong for their height.

The low gravity aspect is also well illustrated by the fact that the largest living creatures on Earth are, by far, aquatic species such as whales.

A man petting a blue whale.

Conversely, in higher gravity planets that could support life, I suspect we’d see much smaller species overall.

So yes—it’s entirely possible there are planets with giant lumbering beasts walking about. Or at a minimum, ocean planets with even larger species than we currently have.

What is the most dangerous planet?

 The richest and most dangerous planet.

This planet is renowned for its valuable mineral resources. It is also known as the diamond planet, as almost all of the rocks that make up the planet are diamonds.

The planet 55 Cancri e has been my interest since I was 10 years old. With a mass eight times greater than Earth, it was only discovered by scientists in 2004. It's quite intriguing because it's believed to be a carbon planet, containing more carbon than oxygen. Interestingly, the side exposed to the planet's "sun" can reach temperatures of 1,700 degrees Celsius, hot enough to melt iron.

Although this is a "rich" planet whose rocks are diamonds that could be very profitable if sold on Earth, it is also very dangerous to visit. The diamonds there are not only found on the surface, but also fall from above like rain. Of course, the diamonds that fall there are not polished diamonds like those found in jewelry stores; they are raw, sharp, and capable of ripping through your skin.

I think that's all I can answer. It's been 7 years since I've been introduced to that planet, so explaining it is difficult because I've forgotten a bit.

Could there be a planet with 99% oxygen in space?

 We actually already know of one, but it's a moon, not a planet!

And yet it is so thanks to a small loophole.

This is Europa. It's a moon of Jupiter and is slightly smaller than our Moon. Its surface is composed of layers of ice, probably with liquid water deeper down. On the ice, this moon is constantly bombarded by deadly radiation (caused by the nearby volcanic moon Io and Jupiter's immense magnetic field).

Its atmosphere is composed almost exclusively of oxygen. But oxygen is so rare in the universe, so where does it come from? While oxygen on Earth is formed by plants, the oxygen on Europa is formed by radiation passing through the ice, splitting water molecules into hydrogen and oxygen gas (the hydrogen escapes into space).

But you couldn't breathe in it! Why?

Because Europa's atmosphere is actually very, very, very thin. The air pressure at its surface is only a billionth of that on Earth. So it can barely be said to have an atmosphere.

So here's the loophole: You asked about a planet whose atmosphere is 99% oxygen, which is a ratio. But you didn't ask how much atmosphere there is in the first place.

Is Pluto still a planet, or do astronomers call it a dwarf planet?

When it was discovered in 1930, Pluto was considered to be the ninth planet of the Solar System. It’s quite tiny, though: about half the size of our own Moon.

(Pluto is bottom left)

But over time, astronomers began to realise just how many similar objects there are out there beyond Neptune, in what is called the Kuiper Belt (which is kind of similar to the Asteroid Belt between Mars and Jupiter). Dozens, maybe hundreds or even thousands of them.

So if we are calling Pluto a planet, putting in the same category as Earth, Mars, etc., then there’s potentially a vast number more which should be added to the traditional list of planets. That’s not very convenient or clear.

So in 2006 the International Astronomical Union decided to define exactly what we mean by the word ‘planet’. An upshot of that was that Pluto didn’t fully qualify and came to be redefined as a ‘dwarf planet’. That is,

• it’s a round object and it’s orbiting the Sun just like a planet,
• however, it’s very small, more like the size of a moon or asteroid,
• and as such, it’s not big enough (gravitationally) to ever carve out an orbit all to itself like any big planet would.

Pluto is now just one of several dwarf planets that have been identified, including Haumea, Makemake, Eris and Ceres.

A couple of interesting facts about Pluto:

Pluto’s 248-year elliptical orbit around the Sun sometimes brings it closer to the Sun than Neptune’s orbit.

Pluto has a surprisingly big satellite (moon), called Charon. In effect, it’s a binary system.