The Science of Interstellar: Chapter II. Gargantua (Chapter 8. Imaging Gargantua) + and my winter break story

 

The Science of Interstellar: Chapter II. Gargantua

Chapter 8. Imaging Gargantua

Hello everyone! Are you all having a wonderful December? In Korea, it started to snow (a lot). I am having THE BEST winter break ever with my friend who is studying in the UK. We haven't met for 3 months, so I am spending a lot of time reading, studying, and hanging out with him. I showed him my blog and he said that it is fascinating, but a bit hard at the same time. 

I am curious about your thoughts! Please leave comments if you need anything, want any changes / have recommendations, etc. Your comments are welcome always :)

Title: Interstellar

Director: Christopher Nolan

Cast: Matthew McConaughey, Anne Hathaway, Jessica Chastain, Matt Daymon

Genre: Science Fiction, Dystopia, Documentary, Action, Adventure

Language: English

Rated PG-13

Running time: 169 minutes

My Rating: 9.9/10

Today's post, as I informed you last time, will be about the Imaging of the Gargantua. 

Have you ever thought how we can see black holes? Isn't it weird? Black holes' strong gravity pulls all of the light into the middle of the black hole. How is this possible?

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The answer is "because we see the black holes by their influence on light from other objects." 

In the Interstellar movie, the light source is the black hole accretion disk, i.e., the light emitted by some matter that is orbiting around the black hole. As it orbits around, friction between disk particles produces some heat, which makes the particles slowly spiral toward the black hole, and, more importantly here, produces some light in sufficiently large amounts to be seen. 

Actually, such an accretion disk can be extremely hot and thus emits a large amount of visible light and an even larger amount of X-rays. The accretion disk that is depicted in the Interstellar movie is therefore in an unusually non-active state, or, in astrophysicists' vocabulary, in a quiescent state.

Gravitational lensing occurs when a massive celestial body bends light from a distant source as it travels toward an observer. Gargantua casts a black shadow on the field of stars, and deflects the light rays from each star, distorting the stellar pattern the gravitational lensing that the camera sees. 

The image above shows a rapidly spinning black hole as it would appear to you if you were in Gargantua's equatorial plane. 

The totally black region in the middle is Gargantua's shadow. Immediately outside the shadow's edge is a very thin ring of starlight called the "ring of fire."

https://www.youtube.com/watch?v=CbW2jKXq3gE

This is a simulation video that shows Starfield under the influence of gravitational lensing for reference. It is very (very) cool, so I recommend having a look at it! (it is only 16 sec long)

Gargantua is a fast-spinning black hole. However, for a fast spin, a mass audience could be confused by the flattening of the left edge of Gargantua’s shadow and by some peculiar feature of the star streaming and the accretion disk, so Christopher Nolan chose a smaller spin (60% of the max.)

The Shell of Fire

The Shell of Fire plays a key role in producing Gargantua's shadow and the thin ring of fire along it. The shell of fire is the region surrounding the black hole, and it contains nearly trapped photon orbits. To make it easy to understand, I have made a summary note/poster about the shell of fire with images. For a high-quality image, you need to click the image :)

There are 2 types of lensing: lensing by a nonspinning black hole and lensing by a rapidly spinning black hole (Gargantua).

1. Lensing by a nonspinning black hole

Let's start with a nonspinning black hole and with light rays that emerge from a single star. 

Two light rays travel from the star to the camera. They each travel along the straightest line they can in the hole’s warped space, but because of the warping, each ray gets bent. 

Have a look at this image for your reference (you will need to click the image!)

One bent ray travels around the hole’s left side; the other, around its right side. Each ray brings the camera its own image of the star. The right image is much closer to the hole’s shadow than the left image ⇒ because its bent ray passed closer to the hole’s event horizon

The black hole’s shadow consists of directions from which no rays can come to the camera. All the rays that “want to be” in the shadow got caught and swallowed by the black hole.

This is a summary note of the lensing of a nonspinning black hole! Feel free to have a look at it :)

2. Lensing by a rapidly spinning black hole

click the image for a high-quality image!

Creating Interstellar’s Black-hole and Wormhole Visual Effects

The team that produced the visual effects in the movie Interstellar consisted of: Christopher Nolan, Kip Thorne, Double Negative (https://www.dneg.com/), and Oliver James (a chief scientist). 

Kip Thorne, the author of "The Science of Interstellar" said he actually did this just because it’s fun. He states, 

“During my half-century physics career, I put great effort into making new discoveries myself and mentoring students as they made new discoveries… Why not, for a change, do something just because it’s fun even though others have done it before me? And I went for it. And it was fun. And to my surprise, as a byproduct, it produced new discoveries.”

Kip worked out the equations that compute the trajectories of light rays that begin at some light source and travel inward through Gargantua’s warped space and time to the camera. From those light rays, the equations then compute the images the camera sees, taking into account not only the light’s sources and Gargantua’s warping of space and time but also the camera’s motion around Gargantua.

Then he used a computer software called Mathematica to compare images produced by the computer code produced by Alain Riazuelo’s image (a researcher who is an expert in this).

To generate the ultra-high-quality IMAX images needed for the movie, Olive and Kip did it in steps. They began with a nonspinning black hole’ and a nonmoving camera. Then they added the black hole’s spin. Then they added the camera’s motion: first motion in a circular orbit, and then plunging into a black hole. And then they switched to a camera around a wormhole.

To model some of the more subtle effects, they needed not only equations describing the trajectory of a ray of light but also equations describing how the cross-section of a beam of light changes its size and shape during its journey past the black hole.

Fortunately, people at the University of Toronto had derived the necessary equations in almost the form he needed in 1977.

At Double Negative, an accretion disk was added and created the background galaxy with its stars and nebulae that Gargantua would lens. Then added the Endurance and Rangers and landers and the camera animation, and moulded the images into intensely compelling forms.

The film clips are like experimental data for Kip Thorne. They revealed things he never could have figured out on his own, without those simulations.

Imaging a Gravitational Slingshot

There are more than just black holes to image! The team also had to show how the gravitational slingshot would look to Copper in the movie. 

The images show what gravitational slingshots would look like to Copper as he piloted the Ranger toward Miller’s planet.

The sequence of images as Cooper’s Ranger swings around an IMBH (intermediate-mass black hole)

1. Gargantua is in the background with the IMBH passing in front of it. The IMBH grabs light rays from distant stars that are headed toward Gargantua swings the rays around itself, and ejects them toward the camera. This explains the doughnut of starlight that surrounds the IMBH’s shadow.
2. As the IMBH appears to move rightward, it leaves Gargantua’s primary shadow behind itself and it pushes a secondary image of Gargantua’s shadow ahead of itself. It is Gargantua’s shadow that is being lensed, by the IMBH.
3. the secondary shadow is shrinking in size, as the IMBH moves onward. By this time the slingshot is nearly complete, and the camera, on board the Ranger, is headed downward, toward Miller’s planet.

As a sci-fi movie lover, I have always been interested in visual effects which look realistic (not in the past, but it is becoming more realistic in every new movie). While I was reading and researching about this topic, I was so fascinated to find out how the production team has actually produced the visual effects on the imaging of Gargantua. Also, after reading Kip Thorne's story of participating in the visual effects team, I was truly inspired by him. Although I am planning to become a researcher or engineer, I want to contribute to sci-fi movie production as a scientist, engineer, or whatever I become in the future! That has become my dream. 

Since I have been posting a lot only about the movie Interstellar, I feel like we need a new refreshing movie. So, in the next post, I will be introducing a new movie to you!

"The Theory of Everything" 

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This is my second favourite movie, and it is about Stephen Hawking's life who I respect the most and is my role model. 

I'll come back in a week with a touching story of Stephen Hawking and about his groundbreaking physics discoveries!