Astronomy

Do the actual false colours in the M87 black hole picture convey information?

Do the actual false colours in the M87 black hole picture convey information?


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As for the title. The picture could have been plotted in grey scale, B&W, whatever couple of colours, or perhaps using a window of wavelength in order to show shift of the Doppler/relativistic Doppler kind.

Discarding the obvious dark, shall the picture be watch at merely in term of brightness, or considering yellow and red as well?

And independently, why those colours have been choose? Just an aesthetic and suggestive choice, or that should be the apparent image as seen by eyes if we could go there?

I resume: is the picture a radio waves intensity or brightness map, or conversely a kind of "as it would be" picture in the Vis (modelled from the behaviour of the collected radio waves and theories)?


See this article recently published by the EHT collaboration describing how they generated the image. Specifically, chapter 5 of that article describes the origin of the image. To quote the article (specifically the caption of figure 3):

The image is shown in units of brightness temperature, ${T}_{{ m{b}}}=S{lambda }^{2}/2{k}_{{ m{B}}}{ m{Omega }}$, where S is the flux density, λ is the observing wavelength, $k_{B}$ is the Boltzmann constant, and Ω is the solid angle of the resolution element.

The false colors in the image convey the surface T brightness (a sort of measurement of the intensity or flux from that area) of the material surrounding the black hole's event horizon. Brighter color means higher brightness temperature. There is not information about the physical T of the in falling materials as the collected radiation is of synchrotron type and not that of a black body. As you say, the image could have been shown in grayscale or any other color scale. The fact that it is shown in an orange-ish color is merely the convention chosen by the scientists who generated the image.

BUT there's a lot more information in the image than just how bright the material is. For example, the fact that the material is brighter on one side than on the other can tell us about the geometry of the material surrounding the black hole, or about how that material is rotating around it. If you have the time, check out this article and read up on the actual journal articles published by the Event Horizon Telescope collaboration linked at the bottom.


This comment is too long for a comment.

I could not find a source (yet) stating explicitly that it is a scalar quantity that is plotted, so I thought I would investigate the colors themselves for any sign of additional information.

What I found was inconclusive.

From https://eventhorizontelescope.org/ I found the smaller size imagehttps://static.projects.iq.harvard.edu/files/styles/os_files_xlarge/public/eht/files/20190410-78m-800x466.png">

import numpy as np import matplotlib.pyplot as plt from mpl_toolkits.mplot3d import Axes3D fname = '20190410-78m-800x466.png">ShareImprove this answeranswered Apr 11 '19 at 8:54uhohuhoh28.5k6 gold badges55 silver badges172 bronze badges 

Do the actual false colours in the M87 black hole picture convey information? - Astronomy


  • Cygnus X-1 is a black hole about 15 times the mass of the Sun in orbit with a massive blue companion star.
  • Astronomers used several telescopes including Chandra to study Cygnus X-1.
  • The combined data have revealed the spin, mass, and distance of this black hole more precisely than ever before.
  • Stephen Hawking lost a bet &mdash originally placed in 1974 &mdash that Cygnus X-1 did not contain a black hole.

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

A trio of papers with data from radio, optical and X-ray telescopes, including NASA's Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon &mdash the point of no return for material falling towards a black hole &mdash is spinning around more than 800 times a second.

Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory's Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.


40 Years of Black Hole Imaging (2): Colors and movies, 1989-1993

Sequel of the previous post 40 Years of Black Hole Imaging (1) : Early Work 1972-1988

First Flight into a Black Hole

In 1989-1990, while I spent one year as a research visitor at the University of California, Berkeley, my former collaborator at Paris-Meudon Observatory, Jean-Alain Marck, both an expert in general relativity and computer programming, started to extend my simulation of 1979. The fast improvement of computers and visualization software (he used a DEC-VAX 8600 machine) allowed him to add colors and motions. To reduce the computing time, Marck developed a new method for calculating the geodesics in Schwarzschild space-time, published only several years later (Marck 1996). In a first step Marck started from my model of 1979 and calculated static images of an accretion disk around a Schwarzschild black hole according to various angles of view, see Figure 1 below.

Figure 1. False-Coloured images of a black hole accretion disk for various angles of view by J.-A.
Marck & J.-P. Luminet , 1989 (unpublished).

In 1991, when I went back to Paris Observatory, I started the project for the French-German TV channel Arte of a full-length, pedagogical movie about general relativity (Delesalle et al. 1994). As the final sequence dealt with black holes, I asked Marck to introduce motion of the observer with the camera moving around close to the disk, as well as to include higher-order lensed images and background stellar skies in order to make the pictures as realistic as possible. The calculation was done along an elliptic trajectory around a Schwarzschild black hole crossing several times the plane of a thin accretion disk and suffering a strong relativistic precession effect (i.e. rotation of its great axis), see figure 2 below.

Compared to my static, black-and-white simulation of 1979, the snapshot reproduced in Figure 3 below shows spectacular improvements:

Figure 3. Colored image of a black hole accretion disk as seen by a moving observer at 7°
above the disk’s plane. The observer uses a camera equipped with filters to convert into
optical radiation the emitted electromagnetic radiation. The arbitrary coloring encodes the
apparent luminosity of the disk, the brightest and warmest parts being colored yellow, the
colder parts red. The transparency of the disk was enhanced in order to show the secondary
image through the primary, as well as some background stars. Compared with figure 8 there
are additional distortions and asymmetries due to the Doppler effect induced by the motion of
the observer himself. As a result the region of maximum luminosity has no more the shape of a
crescent (from Marck 1991)

The full movie is available on my youtube channel :


Pixels to Stitches: Embroidering Astronomy Images

While an emeritus professor at Harvard University in the 1970s, the astronomer Cecilia Payne-Gaposchkin received an unusual request: Would she embroider an x-ray image of the supernova remnant Cassiopeia A? A practitioner of needlepoint embroidery as well as of stellar spectroscopy, she obliged. Now, decades later, many astronomy researchers and enthusiasts are translating pixels of screen light to pixels of colored thread, rendering astronomical data and images in cross stitch, another form of embroidery.

Why is cross stitching especially well-suited to recreating astronomy data? &ldquoBasically, it&rsquos pixel art,&rdquo says Yvette Cendes, an astronomer at the Center for Astrophysics, Massachusetts, and an avid cross stitcher. Cross-stitched designs consist of row after row of x-shaped stitches in a specialized fabric that has a grid of tiny holes (needlepoint designs are similar, but the stitches are different, and a type of canvas is typically used as the base fabric). To create designs, cross stitchers normally follow a cross-stitch pattern&mdasha diagram that dictates which color of thread to use for any given square of the grid. Since astronomers often go through a similar process in presenting their data in 2D grids of pixels, cross stitch is a natural needle-and-thread cousin of astronomy.

Cendes has recreated a variety of astronomical data through cross stitch, from a radio image of a star being torn apart by a black hole to the Arecibo message that was broadcast into space in 1974. She has even stitched a reproduction of a figure from one of her papers&mdasha 37-panel behemoth depicting snapshots of the famous supernova SN1987A&rsquos remains over a span of 25 years. She took great care in preserving the accuracy of the data she was stitching, including the color scale and coordinates. &ldquoIt&rsquos the same information,&rdquo Cendes says. &ldquoIt&rsquos just in cloth instead of on your screen.&rdquo

Like researchers fiddling with colors and axes on their plots, cross stitchers can control the look of their creations by adjusting several parameters. Thread colors offer an array of choices, of course, but changing the thickness of threads or the spacing of holes in the cloth can also affect how a piece looks.

&ldquoThat&rsquos kind of what we do in astronomy, if you think about it,&rdquo Cendes says. &ldquoWe spend a lot of time trying to make the plot look pretty, right?&rdquo

Many other researchers have reproduced astronomical data in cross stitch. Mia de los Reyes, a graduate student in astronomy at Caltech, created a cross-stitch version of the supernova remnant x-ray image that Payne-Gaposchkin rendered in needlepoint decades ago. Adi Foord, an astrophysicist at Stanford University, converted the Event Horizon Telescope&rsquos now-iconic black hole picture into a cross-stitch pattern, depicting the black hole&rsquos photon ring with a blaze of red, orange, and yellow threads on black cloth.

When it comes to extremely detailed astronomical images, such as photos of Solar System planets taken with the Hubble Space Telescope, translating them into manageable cross-stitch patterns can be challenging. Clare Bray, a cross stitcher in the UK who designs and sells cross-stitch templates in her online shop, bases many of her products on real astronomical images. To make a pattern of a celestial object, she uses a specialized computer program that allows her to draw the image and fill in colors on a grid. She takes care to ensure that the stitched versions of astronomical observations have enough detail and complexity to be recognizable and attractive without requiring a daunting&mdashand expensive&mdashnumber of thread colors. &ldquoIt&rsquos quite a balancing act,&rdquo Bray says.

One of Bray&rsquos recent designs featured nine different astronomical objects as varied as Jupiter, the Crab Nebula, and the Andromeda Galaxy&mdashall based closely on real images. She wondered if the montage would seem too serious, she says, but the design has been far more popular than she anticipated. She thinks people appreciated the specificity of the depictions&mdashthat it didn&rsquot include a generic drawing of a made-up galaxy, for example, but a faithful reproduction of an actual galaxy.

&ldquoI tend to be slightly literal when it comes to space,&rdquo Bray says. &ldquoI didn&rsquot think there was much point in making things up, because there&rsquos such great stuff out there anyway.&rdquo

Bray, who has a bachelor&rsquos degree in physics, also wrote descriptions to go along with each of the featured objects in the design, including explanations of false color images and even some nuclear physics. Her customers range from cross-stitching research astronomers, including Cendes, to cross stitchers who know little about space but are drawn to the designs.

&ldquoYou've really got the whole range, which has been really nice,&rdquo Bray says. &ldquoThis is for everyone.&rdquo

Erika K. Carlson is a Corresponding Editor for Physics based in New York City.


Why does NASA put false colours EVERYWHERE?

Why do they "lie" to us, making lots of people think that space look like a LSD trip, although it is actually bland with few colours?

Where is it possible to see all celestial bodies in their REAL COLOURS, to see how they would look like if you were at less than 5 ly from them, looking at them with naked eyes? With no bullshit colors like in NASA pictures.

Because the pictures are imaged at light frequencies not perceived by the human eye, such as infra-red and ultra-violet. So the full majesty of the image can be conveyed, those parts of the spectrum that can't be observed unaided are converted to the light range we can see.

Uhh, no, that's not the crab nebula in reality. In reality, the crab nebula is invisible to the naked eye. Youɽ only see it as black even if you were standing within it, because the human eye didn't evolve to do long-exposure astrophotography.

The human eye is crappy when it comes to seeing the universe. It can't do exposures, it can only see an extremely narrow slice of the electromagnetic spectrum, and even then it is biased towards colours like green and doesn't see the "true" spectrum of visible light. Oh and colours don't exist, they're just a construct by the human brain to make the processing of visual data easier. Those false colour images are just as 'real' as what the human eye sees.

NASA shouldn't have to go out of their way to remove all detail and making a scientifically useless image just to please you (and your crappy eyes)

It's like asking why the map is stretched in polar regions and not continuous, but cut in the middle of Pacific Ocean.

It is not because anybody wants us to believe in a lie. It is simply they "best of all the inaccurate ways" to present the data we have collected about space. Some nebulas and other interstellar objects have much more complex structures that the things we can only see in the visivble spectrum, so to give us a better idea of their internal structure and actual size, all wavelenghts are translated into the narrow stretch of what our senses are able to take.

In general it is MUCH MORE important from a scientific perspective to know all the size and structure details, than to know the "real color" of an object, because it is about understanding how things behave and how they form and evolve over time. Knowing if it is really as pretty as it is in the picture is more or less useless for scientists.

Edit: Or another analogy - it's more useful to color a weather forecast map all the way from blue to red, even if the temperature outside does not cause our planet to suddenly shift colors. It is just the best way we can think of to present the data we have.


Starship Asterisk*

APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by APOD Robot » Wed Dec 18, 2019 5:05 am

Explanation: What do neutron stars look like? Previously these city-sized stars were too small and too far away to resolve. Recently, however, the first maps of the locations and sizes of hotspots on a neutron star's surface have been made by carefully modeling how the rapid spin makes the star's X-ray brightness rise and fall. Based on a leading model, an illustrative map of pulsar J0030+0451's hotspots is pictured, with the rest of the star's surface filled in with a false patchy blue. J0030 spins once every 0.0049 seconds and is located about 1000 light years away. The map was computed from data taken by NASA's Neutron star Interior Composition ExploreR (NICER) X-ray telescope attached to the International Space Station. The computed locations of these hotspots is surprising and not well understood. Because the gravitational lensing effect of neutron stars is so strong, J0300 displays more than half of its surface toward the Earth. Studying the appearance of pulsars like J0030 allows accurate estimates of the neutron star's mass, radius, and the internal physics that keeps the star from imploding into a black hole.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by bystander » Wed Dec 18, 2019 6:01 am

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Boomer12k » Wed Dec 18, 2019 10:37 am

From a search, "A neutron star is formed during a supernova, an explosion of a star that is at least 8 solar masses. The maximum mass of a neutron star is 3 solar masses. If it gets more massive than that, then it will collapse into a quark star, and then into a black hole."

Sooo. um. if it has less than 3 solar masses. as I understand it, it can't implode further into a black hole. at 1.4 solar masses, this is not going to happen with J0030.
So. I logically submit, Captain, with J0030, it is NOT "internal physics" keeping it from imploding. it is simply its lack of mass.

With two poles in the same hemisphere. the shock seems to have really rent it asunder. Like taking Magnetic North and putting it in Australia, and the Magenetic South, in Tierra del Fruego.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by JohnD » Wed Dec 18, 2019 10:53 am

We get discussions here about the way that colours are interpreted in astronomical photos, and it often seems to be either an aesthetic argument, or one of interpretation, using false colours to make the image clearer. But here, there is a clear misinterpretation, if not an aim to mislead the viewer.

in the small print we read, "the rest of the star's surface filled in with a false patchy blue". If the rest of the disc had been a plain, unmarked colour, that would be a true picture of this remarkable acheivement in imaging. To insert apparent markings is incorrect, with no evidence to substantiate it.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by orin stepanek » Wed Dec 18, 2019 12:06 pm

Smile today tomorrow's another day!

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Boomer12k » Wed Dec 18, 2019 1:07 pm

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by BDanielMayfield » Wed Dec 18, 2019 1:41 pm

We get discussions here about the way that colours are interpreted in astronomical photos, and it often seems to be either an aesthetic argument, or one of interpretation, using false colours to make the image clearer. But here, there is a clear misinterpretation, if not an aim to mislead the viewer.

in the small print we read, "the rest of the star's surface filled in with a false patchy blue". If the rest of the disc had been a plain, unmarked colour, that would be a true picture of this remarkable acheivement in imaging. To insert apparent markings is incorrect, with no evidence to substantiate it.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by [email protected] » Wed Dec 18, 2019 2:32 pm

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Chris Peterson » Wed Dec 18, 2019 2:36 pm

From a search, "A neutron star is formed during a supernova, an explosion of a star that is at least 8 solar masses. The maximum mass of a neutron star is 3 solar masses. If it gets more massive than that, then it will collapse into a quark star, and then into a black hole."

Sooo. um. if it has less than 3 solar masses. as I understand it, it can't implode further into a black hole. at 1.4 solar masses, this is not going to happen with J0030.
So. I logically submit, Captain, with J0030, it is NOT "internal physics" keeping it from imploding. it is simply its lack of mass.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Chris Peterson » Wed Dec 18, 2019 2:42 pm

We get discussions here about the way that colours are interpreted in astronomical photos, and it often seems to be either an aesthetic argument, or one of interpretation, using false colours to make the image clearer. But here, there is a clear misinterpretation, if not an aim to mislead the viewer.

in the small print we read, "the rest of the star's surface filled in with a false patchy blue". If the rest of the disc had been a plain, unmarked colour, that would be a true picture of this remarkable acheivement in imaging. To insert apparent markings is incorrect, with no evidence to substantiate it.

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by TheOtherBruce » Wed Dec 18, 2019 3:21 pm

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Chris Peterson » Wed Dec 18, 2019 3:44 pm

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by Ralphbolt » Wed Dec 18, 2019 3:59 pm

Re: APOD: A Hotspot Map of Neutron Star. (2019 Dec 18)

Post by neufer » Wed Dec 18, 2019 4:03 pm

<<Over time, neutron stars slow, as their rotating magnetic fields in effect radiate energy associated with the rotation older neutron stars may take several seconds for each revolution. This is called spin down. The rate at which a neutron star slows its rotation is usually constant and very small.

The spin-down rate (P-dot) of neutron stars usually falls within the range of 10 −22 to 10 −9 , with the shorter period (or faster rotating) observable neutron stars usually having smaller P-dot. As a neutron star ages, its rotation slows (as P increases) eventually, the rate of rotation will become too slow to power the radio-emission mechanism, and the neutron star can no longer be detected.

P and P-dot allow minimum magnetic fields of neutron stars to be estimated. P and P-dot can be also used to calculate the characteristic age of a pulsar, but gives an estimate which is somewhat larger than the true age when it is applied to young pulsars.

P and P-dot can also be plotted for neutron stars to create a P–P-dot diagram. It encodes a tremendous amount of information about the pulsar population and its properties, and has been likened to the Hertzsprung–Russell diagram in its importance for neutron stars.>>


**Black Holes in Living Color:

What can one say that isn't obvious. Just stunning to look at. I never thought that there was so much color around them. I always thought Dark and Ugly looking. I guess for TV/Movies.

The sourec has more pics. Take a look and enjoy. If you can add anything, please do but I think this is one of those threads that speak for its self.

Take care and enjoy them all.

Im not sure what you are referring to, as to artist doing etc. These four I posted are photos-released by NASA. Please check the source link for the others-which at least one is an artist rendition.

The last image in the OP is an artist rendering. The rest are actual photographs. Mind you, they may have been photoshopped to enhance the color. However, as long as their have been color cameras astronomers have been taking color photographs. Generally speaking, most planetary pictures will state 'false color' additions.

I thought the last pic looked like an artists rendition. How do they know the density of the black holes?

Fancy math. Namely observing the gravitational effects the body has on another body.

I thought their might be some discussion on the last one as to what it was.

And, I agree. I saw it is an artist work. But, going to the source article link, then to picture # 8 and you will see this below the photo:

Black Holes in Living Color # 8

GRO J1655-40 (in blue) is the second so-called 'microquasar' discovered in our Galaxy. Microquasars are black holes of about the same mass as a star.
(Photo: European Space Agency, NASA, Felix Mirabel and the Institute for Astronomy and Space Physics/Conicet of Argentina)

I don't know, you tell me? lol

I would bet its a paintjob. Maybe we should call them on it. say HEY.

Ah, Okay thank you for the insight well. after reading the other replies as well I'm left scratching my head a bit, I think I'll just take the safe right and see that I like all the color added to the space pictures

You bring up a very good point. I can't believe I didn't come up with that. There does seem to be a lot of material around them.

Maybe someone can explain that. I would have to say that we are use to the movie concept of a black hole and not a real one.

I mean how in the world can they know that? That means the object we're looking at probably doesn't even exist any more. It might have moved, disappeared or changed like 49.9 million years ago since we are now only seeing it’s light reaching us.
What we see now is so far in the past then that everything we know about the universe is wrong.
Outdated… 50 million years ago.

Am I just not understanding this??

You actually worded it nicely-the issue.

This stuff could have been wiped out and rejuvinated by the time we see it (maybe even twice).

Messes with our minds and what we think we know.

As for the plume's of matter When a massive object, like a star, or several stars, are being ripped apart and experiencing increased gravity they create an enormous amount of energy. The closer to the center of the black hole, the greater the effect of gravity, the black hole is also spinning, so the matter not only falls but orbits at an extremely high speed. This causes friction which results in heat, a lot of it. This also creates an amazing amount of energy, x-rays and gamma rays, some of which can 'escape' the black hole in plumes of matter that are light-years long, travelling near the speed of light, these plumes are just condensed rays of energy. Think death rays or lasers.

They don't really escape the black hole in the sense that they enter and then leave, they're nearing the event horizon without ever actually going into the black hole.

The pictures above are examples of active galactic nuclei, which are just black holes that are actively feeding off of surrounding gas and matter. Unlike our somewhat inactive Milky Way center.

Star for you as it is well deserved. Thanks for making it understandable-to me at least.

I just checked out that link you put in your post. I put that site in my favorites right away. Nice.


Analysis, presentation, and understanding in experimental fluid flow studies: A colourful evolutionary story

The digital computer has revolutionised the ability of the experimentalist to obtain, analyse and interpret physical data, and no-where is this more apparent than in the study of fluid flow and heat transfer problems. The emergence of digital methods is reviewed, with the discussion reflecting the first author's personal experience over the past 50 years.

To illustrate how modern experimental study relies heavily on digital technology, representative results are presented for a number of fluid flow problems that have been investigated using advanced forms of optical instrumentation—namely laser light sheet visualisation, three-component laser Doppler anemometry (LDA), and particle image velocimetry (PIV). These examples are used to emphasise the importance of digital methods for data capture and analysis, with samples of the reduced results being presented in the form of multi-functional colour graphs and images. The discussion shows how the processed data can yield improved understanding, revealing complex three-dimensional flow features that probably could not have been identified, and certainly could never have been quantified, in previous years.

Colour, specifically, is shown to have emerged with increasing prominence in the last few decades, and its various uses are now seen to be crucial for the modern experimentalist. These aspects are comprehensively discussed.


Starship Asterisk*

APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by APOD Robot » Fri Apr 16, 2021 4:07 am

Explanation: Light rays from accretion disks around a pair of orbiting supermassive black holes make their way through the warped space-time produced by extreme gravity in this stunning computer visualization. The simulated accretion disks have been given different false color schemes, red for the disk surrounding a 200-million-solar-mass black hole, and blue for the disk surrounding a 100-million-solar-mass black hole. That makes it easier to track the light sources, but the choice also reflects reality. Hotter gas gives off light closer to the blue end of the spectrum and material orbiting smaller black holes experiences stronger gravitational effects that produce higher temperatures. For these masses, both accretion disks would actually emit most of their light in the ultraviolet though. In the video, distorted secondary images of the blue black hole, which show the red black hole's view of its partner, can be found within the tangled skein of the red disk warped by the gravity of the blue black hole in the foreground. Because we're seeing red's view of blue while also seeing blue directly, the images allow us to see both sides of blue at the same time. Red and blue light originating from both black holes can be seen in the innermost ring of light, called the photon ring, near their event horizons. Astronomers expect that in the not-too-distant future they’ll be able to detect gravitational waves, ripples in space-time, produced when two supermassive black holes in a system much like the one simulated here spiral together and merge.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by alter-ego » Fri Apr 16, 2021 4:42 am

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Ann » Fri Apr 16, 2021 4:46 am

So. how about diving into a black hole in the hopes of finding a wormhole inside?

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Chris Peterson » Fri Apr 16, 2021 4:50 am

So. how about diving into a black hole in the hopes of finding a wormhole inside?

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by shaileshs » Fri Apr 16, 2021 5:06 am

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by JohnD » Fri Apr 16, 2021 8:52 am

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by rj rl » Fri Apr 16, 2021 9:15 am

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Knight of Clear Skies » Fri Apr 16, 2021 10:17 am

Merging masses: chart showing the ten black-hole mergers (top) and one neutron-star merger (bottom). Also shown are black holes and neutron stars observed using electromagnetic (EM) radiation. (Courtesy: LIGO-Virgo/Frank Elavsky/Northwestern)

I agree the music was distracting but my mute button took care of that.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by orin stepanek » Fri Apr 16, 2021 12:38 pm

Smile today tomorrow's another day!

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Chris Peterson » Fri Apr 16, 2021 1:06 pm

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by De58te » Fri Apr 16, 2021 1:07 pm

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Chris Peterson » Fri Apr 16, 2021 1:10 pm

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by orin stepanek » Fri Apr 16, 2021 1:26 pm

Smile today tomorrow's another day!

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by sillyworm 2 » Fri Apr 16, 2021 1:42 pm

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Chris Peterson » Fri Apr 16, 2021 1:51 pm

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by E Fish » Fri Apr 16, 2021 2:44 pm

That's an excellent video, and I appreciate that they anticipated my own questions about the distorted secondary image I was noticing during the orbit. I think I've found another video to show my astronomy class.

The first book I read on black holes was back in the 90s in my high school library. It was the only one they had and it was written back in the 60s. So it took me a while to get up to date on what black holes were and the fact that we've detected them. But I've long been fascinated by them and I love introducing students to them because it's a way to get their brains a little stretched.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Ann » Fri Apr 16, 2021 3:04 pm

Like the Milky Way's own supermassive black hole, I think.

Not that it couldn't get hungry in the future, when the Milky Way is getting too close for comfort to the Andromeda galaxy.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Chris Peterson » Fri Apr 16, 2021 3:31 pm

Like the Milky Way's own supermassive black hole, I think.

Not that it couldn't get hungry in the future, when the Milky Way is getting too close for comfort to the Andromeda galaxy.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by neufer » Fri Apr 16, 2021 3:47 pm

<<The Brodie helmet is a steel combat helmet designed and patented in London in 1915 by John Leopold Brodie. A modified form of it became the Helmet, Steel, Mark I in Britain and the M1917 Helmet in the U.S. Colloquially, it was called the shrapnel helmet, battle bowler, Tommy helmet, tin hat, and in the United States the doughboy helmet. It was also known as the dishpan hat, tin pan hat, washbasin, battle bowler (when worn by officers), and Kelly helmet. The German Army called it the Salatschüssel (salad bowl).

At the outbreak of World War I, none of the combatants provided steel helmets to their troops. Soldiers of most nations went into battle wearing cloth, felt, or leather headgear that offered no protection from modern weapons. The huge number of lethal head wounds that modern artillery weapons inflicted upon the French Army led them to introduce the first modern steel helmets in the summer of 1915. The first French helmets were bowl-shaped steel "skullcaps" worn under the cloth caps. These rudimentary helmets were soon replaced by the Model 1915 Adrian helmet, designed by August-Louis Adrian. The idea was later adopted by most other combatant nations.

At about the same time, the British War Office had seen a similar need for steel helmets. The War Office Invention Department was ordered to evaluate the French design. They decided that it was not strong enough and too complex to be swiftly manufactured. British industry was not geared up to an all-out effort of war production in the early days of World War I, which also led to the shell shortage of 1915.

John Leopold Brodie (1873–1945), born Leopold Janno Braude in Riga, was an entrepreneur and inventor who had made a fortune in the gold and diamond mines of South Africa, but was working in London at that time. A design patented by him in August 1915 offered advantages over the French helmet. It was constructed in one piece that could be pressed from a single thick sheet of steel, giving it added strength and making it simple to manufacture. Brodie's patent deals mainly with the innovative lining arrangements an engineer called Alfred Bates of the firm of Willis & Bates of Halifax, Yorkshire, manufacturer of Vapalux paraffin pressure lamps, claimed that he was asked by the War Office to find a method of manufacturing an anti-shrapnel helmet and that it was he who had devised the basic shape of the steel shell. Aside from some newspaper articles, there is nothing to substantiate

Brodie's design resembled the medieval infantry kettle hat or chapel-de-fer, unlike the German Stahlhelm, which resembled the medieval sallet. The Brodie had a shallow circular crown with a wide brim around the edge, a leather liner and a leather chinstrap. The helmet's "soup bowl" shape was designed to protect the wearer's head and shoulders from shrapnel shell projectiles bursting from above the trenches. The design allowed the use of relatively thick steel that could be formed in a single pressing while maintaining the helmet's thickness. This made it more resistant to projectiles but it offered less protection to the lower head and neck than other helmets.>>

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by Ann » Fri Apr 16, 2021 4:27 pm

They really don't gobble up much. Even truly massive black holes like the one in M87, massing more than a billion suns and active enough to have jets, still take a decade just to suck in one additional solar mass. And the overwhelming majority of black holes pretty much suck in nothing at all.

Like the Milky Way's own supermassive black hole, I think.

Not that it couldn't get hungry in the future, when the Milky Way is getting too close for comfort to the Andromeda galaxy.

Point taken, but what about Andromeda's black hole? It's a lot bigger than out own, and our two galaxies are set to merge in the future.

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by johnnydeep » Fri Apr 16, 2021 4:55 pm

There are at least two statements here I don't quite understand:

1. ". material orbiting smaller black holes experiences stronger gravitational effects that produce higher temperatures."

Is this due to the tidal effects being greater for smaller black holes? Meaning that the gravity gradient is steeper around a smaller black hole and thereby tears at orbiting matter more greatly?

2. ". relativity causes the black holes to appear smaller and brighter as they approach the camera and larger and fainter as they recede."

This I don't get at all. Does it matter which BH is closer to the camera and/or whether they are eclipsing each other or not? And either way, I still don't get it

Re: APOD: The Doubly Warped World of Binary. (2021 Apr 16)

Post by neufer » Fri Apr 16, 2021 5:03 pm

Like the Milky Way's own supermassive black hole, I think.

Not that it couldn't get hungry in the future, when the Milky Way is getting too close for comfort to the Andromeda galaxy.

Hungrier, maybe. But it will still not absorb very much. How could it?

Its size does not exceed that of Neptune's orbit- a volume so small that any collisions with passing stars is extremely unlikely, even in the densest parts of the collision zones.

"[Recent] observations of the star S14 showed the mass of Milky Way's Sgr A* to be about 4.1 million solar masses within a volume with radius no larger than 45 AU or about 6.7 billion kilometres. S175 passed within a similar distance. For comparison, the Schwarzschild radius is 0.08 AU. "

The Schwarzschild radius of Milky Way's Sgr A* is only 12.25 million kilometers.

(As of its last perihelion on 17 January 2021,
the Parker Solar Probe's closest approach to the Sun was at 13.5 million kilometers.)

However, the Andromeda Galaxy is thought to harbor two massive
black holes of radii 0.8 AU & 3.2 AU orbiting about 4.9 ly apart.

(The Schwarzschild radius of Messier 87's black hole is

125 AU.
Voyager 1&2 are currently at 152.5 AU & 126.8 AU from the Sun.)

<<The Andromeda Galaxy is known to harbor a dense and compact star cluster at its very center. In a large telescope it creates a visual impression of a star embedded in the more diffuse surrounding bulge. In 1991, the Hubble Space Telescope was used to image the Andromeda Galaxy's inner nucleus. The nucleus consists of two concentrations separated by 1.5 pc (4.9 ly). The brighter concentration, designated as P1, is offset from the center of the galaxy. The dimmer concentration, P2, falls at the true center of the galaxy and contains a black hole measured at 3–5 × 10 7 M in 1993, and at 1.1–2.3 × 10 8 M in 2005. The velocity dispersion of material around it is measured to be ≈ 160 km/s.

Chandra X-ray telescope image of the center of the Andromeda Galaxy. A number of X-ray sources, likely X-ray binary stars, within the galaxy's central region appear as yellowish dots. The blue source at the center is at the position of the supermassive black hole.

It has been proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole. The eccentricity is such that stars linger at the orbital apocenter, creating a concentration of stars. P2 also contains a compact disk of hot, spectral-class A stars. The A stars are not evident in redder filters, but in blue and ultraviolet light they dominate the nucleus, causing P2 to appear more prominent than P1.

While at the initial time of its discovery it was hypothesized that the brighter portion of the double nucleus is the remnant of a small galaxy "cannibalized" by the Andromeda Galaxy, this is no longer considered a viable explanation, largely because such a nucleus would have an exceedingly short lifetime due to tidal disruption by the central black hole. While this could be partially resolved if P1 had its own black hole to stabilize it, the distribution of stars in P1 does not suggest that there is a black hole at its center.>>

https://en.wikipedia.org/wiki/Sagittarius_A* wrote:
<<Since the 1980s it has been evident that the central component of Sgr A* is likely a black hole. Infrared and submillimetre spectroscopy by a Berkeley team involving Nobel Laureate Charles H. Townes and future Nobelist Reinhard Genzel showed that the mass must be very tightly concentrated, possibly a point mass.

On October 16, 2002, an international team led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics reported the observation of the motion of the star S2 near Sagittarius A* throughout a period of ten years. According to the team's analysis, the data ruled out the possibility that Sgr A* contains a cluster of dark stellar objects or a mass of degenerate fermions, strengthening the evidence for a massive black hole. The observations of S2 used near-infrared (NIR) interferometry (in the K-band, i.e. 2.2 μm) because of reduced interstellar extinction in this band. SiO masers were used to align NIR images with radio observations, as they can be observed in both NIR and radio bands. The rapid motion of S2 (and other nearby stars) easily stood out against slower-moving stars along the line-of-sight so these could be subtracted from the images.

The VLBI radio observations of Sagittarius A* could also be aligned centrally with the NIR images, so the focus of S2's elliptical orbit was found to coincide with the position of Sagittarius A*. From examining the Keplerian orbit of S2, they determined the mass of Sagittarius A* to be 2.6±0.2 million solar masses, confined in a volume with a radius no more than 17 light-hours (120 AU). Later observations of the star S14 showed the mass of the object to be about 4.1 million solar masses within a volume with radius no larger than 6.25 light-hours (45 AU) or about 6.7 billion kilometres. S175 passed within a similar distance. For comparison, the Schwarzschild radius is 0.08 AU. They also determined the distance from Earth to the Galactic Center (the rotational center of the Milky Way), which is important in calibrating astronomical distance scales, as (8.0±0.6) kiloparsecs. In November 2004 a team of astronomers reported the discovery of a potential intermediate-mass black hole, referred to as GCIRS 13E, orbiting 3 light-years from Sagittarius A*. This black hole of 1,300 solar masses is within a cluster of seven stars. This observation may add support to the idea that supermassive black holes grow by absorbing nearby smaller black holes and stars.

After monitoring stellar orbits around Sagittarius A* for 16 years, Gillessen et al. estimated the object's mass at 4.31±0.38 million solar masses. The result was announced in 2008 and published in The Astrophysical Journal in 2009. Reinhard Genzel, team leader of the research, said the study has delivered "what is now considered to be the best empirical evidence that supermassive black holes do really exist. The stellar orbits in the Galactic Center show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt."

On January 5, 2015, NASA reported observing an X-ray flare 400 times brighter than usual, a record-breaker, from Sgr A*. The unusual event may have been caused by the breaking apart of an asteroid falling into the black hole or by the entanglement of magnetic field lines within gas flowing into Sgr A*, according to astronomers. On 13 May 2019, astronomers using the Keck Observatory witnessed a sudden brightening of Sgr A*, which became 75 times brighter than usual, suggesting that the supermassive black hole may have encountered another object.>>


Inside-out toad

Sorry for the gross picture. This was a toad - but it was turned inside out. I&rsquove never seen anything like it before - the result of some kind of predator? @MyFrogCroaked pic.twitter.com/HwuZPLmq9pMarch 24, 2019

Sometimes gross is also "amazing," as in this inside-out toad! Jan Freedman, curator of natural history at The Box museum in Plymouth told Live Science that he was walking with his family at a reservoir when his 8-year-old son spotted the gory corpse. You can see the toad's translucent intestines spilling out, while the peeled skin of its underside, which is still attached below the jaw, stretches over the toad's back.


Do the actual false colours in the M87 black hole picture convey information? - Astronomy

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming.

The black hole is in a galaxy cluster named RX J1532.9+3021 (RX J1532 for short), located about 3.9 billion light years from Earth. The image here is a composite of X-ray data from Chandra revealing hot gas in the cluster in purple and optical data from the Hubble Space Telescope showing galaxies in yellow. The cluster is very bright in X-rays implying that it is extremely massive, with a mass about a quadrillion &mdash a thousand trillion &mdash times that of the sun. At the center of the cluster is a large elliptical galaxy containing the supermassive black hole.

The large amount of hot gas near the center of the cluster presents a puzzle. Hot gas glowing with X-rays should cool, and the dense gas in the center of the cluster should cool the fastest. The pressure in this cool central gas is then expected to drop, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. However, astronomers have found no such evidence for this burst of stars forming at the center of this cluster.

This problem has been noted in many galaxy clusters but RX J1532 is an extreme case, where the cooling of gas should be especially dramatic because of the high density of gas near the center. Out of the thousands of clusters known to date, less than a dozen are as extreme as RX J1532. The Phoenix Cluster is the most extreme, where, conversely, large numbers of stars have been observed to be forming.

What is stopping large numbers of stars from forming in RX J1532? Images from the Chandra X-ray Observatory and the NSF's Karl G. Jansky Very Large Array (VLA) have provided an answer to this question. The X-ray image shows two large cavities in the hot gas on either side of the central galaxy (mouse over the image for a labeled version). The Chandra image has been specially processed to emphasize the cavities. Both cavities are aligned with jets seen in radio images from the VLA. The location of the supermassive black hole between the cavities is strong evidence that the supersonic jets generated by the black hole have drilled into the hot gas and pushed it aside, forming the cavities.

Shock fronts &mdash akin to sonic booms &mdash caused by the expanding cavities and the release of energy by sound waves reverberating through the hot gas provide a source of heat that prevents most of the gas from cooling and forming new stars.

The cavities are each about 100,000 light years across, roughly equal to the width of the Milky Way galaxy. The power needed to generate them is among the largest known in galaxy clusters. For example, the power is almost 10 times greater than required to create the well-known cavities in Perseus.

Although the energy to power the jets must have been generated by matter falling toward the black hole, no X-ray emission has been detected from infalling material. This result can be explained if the black hole is "ultramassive" rather than supermassive, with a mass more than 10 billion times that of the sun. Such a black hole should be able to produce powerful jets without consuming large amounts of mass, resulting in very little radiation from material falling inwards.

Another possible explanation is that the black hole has a mass only about a billion times that of the sun but is spinning extremely rapidly. Such a black hole can produce more powerful jets than a slowly spinning black hole when consuming the same amount of matter. In both explanations the black hole is extremely massive.

A more distant cavity is also seen at a different angle with respect to the jets, along a north-south direction. This cavity is likely to have been produced by a jet from a much older outburst from the black hole. This raises the question of why this cavity is no longer aligned with the jets. There are two possible explanations. Either large-scale motion of the gas in the cluster has pushed it to the side or the black hole is precessing, that is, wobbling like a spinning top.

A paper describing this work was published in the November 10th, 2013 issue of The Astrophysical Journal and is available online. The first author is Julie Hlavacek-Larrondo from Stanford University. The Hubble data used in this analysis were from the Cluster Lensing and Supernova survey, led by Marc Postman from Space Telescope Science Institute.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.


Watch the video: Die Theorie der Halbbildung und die studentischen Bildungsproteste Ein Gespräch mit Eva Klinkisch (May 2022).