science – Page 5 – Super Facts

The Bizarre Reality of Black Holes

Superfact 15: A black hole is a region of spacetime wherein gravity is so strong that nothing can escape it, not light, not anything. There are different kinds of black holes. We don’t fully understand black holes, which makes them very interesting to science. The boundary of no escape is called the event horizon. Black holes are invisible. They are truly black. However, we can see what they do to their environment as they consume surrounding matter. Below are some bizarre facts about black holes.

Time runs much slower closer to a black hole.
An object falling towards a black hole will become redder, faint, then infrared, then invisible and all its movements and clocks will freeze.
From the perspective of an outside observer, time appears to stop for someone reaching the event horizon of a black hole. Time will continue for someone falling in.
At the center of a black hole may lie a gravitational singularity, a region where the spacetime curvature becomes infinite. However, since we cannot peer into a black hole we cannot know.
The largest known black hole (TON 618) is more than 287 million times more massive than the most massive known star (R136a1).
If our planet earth collapsed into a black hole, it’s diameter would be 1.75 centimeters or 0.69 inches in diameter. The diameter of the largest known black hole (TON 618) is 242 billion miles, which is more than one million times larger than the distance from the earth to moon.
There are supermassive black holes located at the center of most large galaxies, including our Milky Way. The Milky Way’s black hole is about 4 million times the mass of the Sun.
Astronomers estimate that there are around 100 million black holes in our Milky Way.
When an object (maybe a spaceship, or a person) approaches or falls into a black hole the difference between the gravity on the parts closer to the black hole and those further away will be so large that the object is stretched and ripped apart. This is called spaghettification.
Stretching from the event horizon and out another half radius of the black hole is a region called the photon sphere. In the photon sphere light will travel in a non-stable circular orbit around the black hole. Light will go around and around for a while. If you are in the photon sphere you might be able to see the back of your head.
Above is just a small sample of weird black hole facts.

A black hole sucking in a planet — The understanding of black holes requires the General Theory of Relativity, and it is still a lot we don’t understand about them. Stock Photo ID: 2024419973 by Elena11

The Bizarre Reality of Black Holes

I chose the Bizarre Reality of Black Holes as a super-fact and included the ten facts above because these facts are shocking and yet not well known. Below is a photograph of a supermassive black hole at the center of the galaxy M87 taken by the event horizon telescope in 2017. To create the picture below image processing was needed. It is the first photograph of a black hole. This supermassive black hole is an estimated 6.5 billion times as massive as our sun, and 28 million times as massive as the largest known star.

Below is an animation created by NASA that depicts what an observer falling into a black hole would see.

The fact that from the perspective of an outside observer, time appears to stop for someone reaching the event horizon of a black hole seems to prevent anything from falling into a black hole from an outside perspective. How does anything ever get inside the black hole if it freezes up at the event horizon? Black holes grow, they collide and merge, so clearly things can get inside, right? But how? As I tried to find the answer to this question, I found that I was far from the only one asking this question.

A black hole with an orange accretion disk is approached by futuristic starship. — Realistic spaceship approaching a black hole. This content was generated by an Artificial Intelligence (AI) system. Stock AI-generated image ID: 2448481683 AI-generated image Contributor Shutterstock AI Generator.

I searched physics forums trying to find the answer to this question. There were a lot of discussions but no clear answers. Some said, nothing falls into a black hole. Everything accumulates on the event horizon from the outside perspective and that’s how the event horizon and the black hole grows. The observer crossing the horizon essentially jumps infinitely far into the future, or into a different universe, that’s how he can pass through the event horizon.

Others said that the black hole is not static, it grows, and it shrinks from Hawking radiation, and this complicates the equations so that objects can enter the black hole even from an outside perspective. I have a few physics books on black holes that I have not finished reading. If I learn something better, I will update this post.

A depiction of a black hole surrounded by a space-time geometric grid that is bending due to gravity | The Bizarre Reality of Black Holes — AI-generated image Description : Space Black Hole Blue Illustration Gravity Geometry Vast Line. Stock AI-generated image ID: 2457551367 by AI-generated image Contributor Shutterstock.AI

In the image above the grid demonstrates how a black hole is distorting space-time. Other strange facts about black holes are that they are slowly evaporating through what is called Hawking radiation.

They come in different sizes. The smallest known black hole (XTE J1650-500) has a diameter of approximately 15 miles. Perhaps scariest of all, black holes are nearly undetectable unless they are feeding on star dust or tugging on nearby stars. That means one hungry black hole could be zipping right through our solar system without us knowing. Considering there are an estimated 100 million black holes in our Milky Way space travel might be scary.

Addressing a Good Question

After posting this post I received a question via email regarding this fact “If our planet earth collapsed into a black hole, its diameter would be 1.75 centimeters or 0.69 inches in diameter. The diameter of the largest known black hole (TON 618) is 242 billion miles, which is more than one million times larger than the distance from the earth to moon.” The person who asked thought that 1.75 centimeters was pretty tiny and was wondering how a black hole could be that small.

To create a black hole, you need extremely strong gravity and one way to increase the force of gravity at the surface of a planet is to compress all its mass into a smaller volume.

If you compressed all of earth’s gravity so its diameter was only half of what it is, it would be more compact, and the gravity would be four times stronger at earth’s surface. If you compressed it further so that the earth’s diameter would only be a fourth of its original diameter the gravity at the surface would now be 16 times stronger. If you keep compressing the earth until its diameter is only 1.75 centimeters the force of gravity at the surface would be 132,000 trillion times greater than it currently is according to Newtonian physics, and you would get a black hole.

I should say that it comes out differently with General Relativity and that number is different for different sized black holes. However, this calculation is for demonstrative purposes. For relatively small masses like a planet, you would have to compress so much that it becomes tiny before gravity becomes large enough to make a black hole.

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If you were an astronaut on an interstellar journey, would you be afraid of falling into a black hole?

Astronomer

Daily writing prompt

What alternative career paths have you considered or are interested in?

View all responses

So I am trying out the Daily writing prompt for the first time, answering the question “What alternative career paths have you considered or are interested in?”.

I’ve always been interested in astronomy and astrophysics, and I studied engineering physics, later electrical engineering. I did not think astronomer or astrophysicist was an easily attainable career and perhaps not very well paid either, but I think it would have been a fun job to have.

Celestron Powerseeker 70EQ

I am a bit of an amateur astronomer, and I own a basic telescope for amateurs, a Celestron Powerseeker 70EQ. It is not a great telescope, but it is good enough for observing objects such as Saturn and its rings, Jupiter and its four Galilean moons, Mars, Venus (the crescent), the moon and its craters. Those objects you can see from inside a big city like Dallas. Naturally you can do much better if you leave the city and especially if you visit a dark spot. I am a member of TAS, Texas Astronomical Society and they own a dark spot in Oklahoma. Below is a photo of my Celestron Powerseeker 70EQ standing in my garage.

Black Telescope standing in front of bicycles in a garage — Celestron Powerseeker 70EQ

What Does an Astronomer Do?

Astronomers study the universe, including galaxies, stars, planets, and other celestial objects, using telescopes and other instruments to observe and analyze them. They observe and analyze celestial objects. Depending on their specific area, astronomers have different duties.

They observe celestial objects using telescopes.
They conduct research, analyze data and test hypothesis.
They use and develop models including complex mathematical models and computer simulations to understand complex astrophysical phenomena.
They collaborate with peers, they teach, and they do mentoring and public outreach.

Types of Astronomers

Observational Astronomers use telescopes and other observational instruments to collect data from celestial objects.
Theoretical Astrophysicists use mathematical models and computer simulations to understand the physical processes in the universe. They may study stellar evolution, galaxy formation, cosmology, and black holes.
Planetary Scientists study planets, moons, and other objects within our solar system. They use data collected by space missions, telescopes, and remote sensing techniques.
Stellar Astronomers study stars, their properties, and their life cycles. They may study variable stars, binary star systems, massive stars, stellar remnants such as white dwarfs, neutron stars, or black holes.
Galaxies and Cosmology researchers study galaxies and the large-scale structures in the universe.
Radio Astronomers study celestial objects using radio waves instead of visible light. They may study radio galaxies, cosmic microwave background radiation, and the structure of the Milky Way.
Exoplanet Astronomers study and discover planets orbiting stars outside our solar system. They use techniques such as transit photometry and radial velocity measurements to detect and characterize exoplanets.

Famous Astronomers

Nicolaus Copernicus 1473–1543, discovered the heliocentric model putting the sun at the center of our solar system.
Johannes Kepler 1571–1630, revolutionized our understanding of how planets orbit the Sun. He used the Copernicus heliocentric model and very careful measurements to show that the planets moved in elliptical orbits around the sun and he came with additional laws to describe the speed of the planets in their orbits.
Galileo Galilei, 1564–1642, or Galileo di Vincenzo Bonaiuti de’ Galilei, was an Italian astronomer, physicist and engineer who greatly improved the optical telescope and discovered the four primary moons of Jupiter and the rings of Jupiter. He proved that all falling bodies fall at the same rate, regardless of mass, and developed the first pendulum clock. He got in trouble for defending Nikolai Copernicus idea.
Edmund Halley, 1656–1742, investigated and discovered many things including the nature of comets’ orbits.
Edwin Powell Hubble, United States, 1889–1953. Hubble proved that many objects previously thought to be clouds of dust and gas and classified as “nebulae” were galaxies beyond the Milky Way. He showed that these galaxies were moving away from us and each other leading to the conclusion that the universe was expanding.
Vera Rubin, 1928–2016, studied the rotation of galaxies and uncovered the discrepancy between the predicted and observed angular motion. This led to the discovery of dark matter.

What about you? What alternative career paths have you considered or are interested in?

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Supermoon October 2024

“Supermoon October 2024” is not a super-fact post but some fun facts about the Moon. It is a super-moon post instead.

As many of you probably have read, we currently have a so-called supermoon (October 17 & October 18). The moon’s orbit around earth is not a perfect circle but slightly elliptical. Therefore, the moon’s distance to earth varies.

A supermoon is when a full moon occurs when the moon is at its closest point to Earth, called perigee, making it appear larger and brighter than usual. Or more correctly, the term supermoon is usually used to describe a full moon that comes within at least 90% of the perigee. Since this is a special moon event, I took out my little telescope and looked at the moon and its craters. I also took a look at Jupiter, and I saw three of the four Galilean moons.

A close up photo of the near side of the moon | Supermoon October 2024 — Photo by Pixabay on Pexels.com

Jupiter in the middle. It is a greenish speck with lines. It is surrounded by three white dots. — The green speck is Jupiter. The three little dots are three of the four Galilean Moons. I roughly saw this in my telescope an hour ago, but it is not my photo. Photo by Raoni Aldrich Dorim on Pexels.com

I thought I might as well mention a few interesting facts about the moon.

There is no dark side of the moon

This is a very common misunderstanding. The moon is always showing the same side towards us (or almost exactly the same side). When there is a full moon the backside, or far side, of the moon is dark, but that is not the case when the moon is half, or a crescent, etc. When the moon is new, the far side / backside is “full” from sunlight. If you wondered, NASA and other space agencies have photographed the far side of the moon.

On the left is the near side of the moon and on the right the far side of the moon | Supermoon October 2024 — The near side of the Moon and the far side of the Moon. Comparison between the two hemispheres of the Moon. Elements of this image were furnished by NASA. Stock Photo ID: 2157518223 by Claudio Caridi.

Below is a youTube video showing an animation composed of actual satellite photos by NASA.

A few comments about this animation. You see no stars because the sun is shining, and the earth is also quite bright. The reason you don’t easily see stars during the day is not because the sky is blue but because there is too much light to see them. The sun ruins the starry sky. In addition, stars are not easily captured by cameras when there is ambient light. And again, of course, contrary to the belief of some, the backside of the moon is not always dark.

The far side of the moon is different

As you can see in the YouTube video and the enhanced photo above, the far side looks different from the nearside and it is different in appearance and terrain. The near side of the moon has large, dark, flat-lying basins called maria. They look like oceans. The far side is a lot more rugged and covered by lots of craters. Another difference is that the far side of the moon has a much thicker crust compared to the near side.

Photo of the moon on a blue background | Supermoon October 2024 — Photo by Alex Andrews on Pexels.com

The moon is drifting away from earth at about 3.8 centimeters per year

The moon is moving away from earth due to the gravitational forces between the moon and earth, which also causes tidal bulges in the Earth’s oceans and the moon. Back in high school I took a physics test on which you had to calculate how much the moon was moving away from earth based on the size of the tidal waves on earth. I did not solve that one, but not many did. The calculation made perfect sense though and some geniuses got it.

NASA found water on the moon

In 2020, NASA announced the discovery of water on the sunlit surface of the Moon. You can read about it here.

Drop of water — Photo by Pixabay on Pexels.com

The moon was likely created by a celestial collision : The most widely accepted explanation for the existence of the moon is that the Moon was created when a planet-like object, the size of Mars slammed into Earth, soon after the solar system began forming. That was about 4.5 billion years ago.