Space Sunday: black holes, Falcons and moonshots

The first ever direct image of a black hole: M87* at the heart of the galaxy M87, 55 million light years from Earth, released on April 10th, 2019. Credit: the EHT Collaboration

The black hole in the above image resides at the centre of Messier 87 (M87), around 16.4 million parsecs (53 million light-years) from Earth, and part of the Virgo galactic cluster of about 12,000 galaxies. It marks the first time we have directly imaged a black hole – and it is a remarkable achievement for a number of reasons.

Thanks to Hollywood, we’re all very probably familiar with the idea of black holes: a point is space where matter is so compressed that it creates a gravity field from which not even light can escape. However, black holes come in a variety of forms, of which the most unusual might well be those that exist at the centre of many galaxies – including our own. Referred to as “supermassive black holes” on account of their extreme mass, they on a scale many times larger than your typical stellar black hole (which, despite being referred to as “massive” – a reference to their gravitational attraction.

Left: M87 in the Virgo cluster of galaxies, as imaged by the European Southern Observatory’s Very Large Telescope. Note the 5,000 light year-long jet of gas (arrowed) rising from the galaxy. Right: a closer view of M87 and the gas jet captures by the Hubble Space Telescope. Extending well beyond the galaxy, and move at relativistic speeds, the jet is believed to be generated by the black hole at the heart of the galaxy. Credits: ESO (l); J. A. Biretta et al., (STScI /AURA), NASA

We don’t actually understand how galactic black holes like the one at the heart of M87 – and called M87*) formed, but being able to examine them directly could answer some fundamental questions about the nature of the universe and physics, as well as helping us to understand the role they play in the evolution of galaxies. The problem is, actually directly imaging any black hole is actually very hard simply because they are – well, black, and thus not the easiest of things to see against the blackness of space.

Fortunately, there is a way around this problem: black holes are not alone. Their massive gravity means they attract dust and gas, which forms an accretion disk around the black hole, spinning around them at enormous speeds and producing radiation in a range of wavelengths including radio, optical and infra-red. Given given the right capabilities, we can image a black hole against the radiation from this accretion disk.

The composition of a black hole. Credit: ESO, ESA/Hubble, M. Kornmesser/N. Bartmann

But even with an accretion disk to shed light around a galactic black hole has its own set of issues. To image the one at the centre of our own galaxy, for example, is the equivalent of trying to stand in New York’s Times Square and being able to count the dimples on a golf ball 4,000 km (2,450 mi) away; and this despite the fact that the black hole at the centre of our galaxy is thought to be at least 60 million kilometres across.

Nor is trying to image them optically particularly helpful. They need to be imaged across a range of wavelengths – the problem here being that to do so, you need a radio telescope effectively the size of the Earth.

To achieve this, and following an idea first put forward 26 years ago by German radio-astronomer Heino Falcke, the idea of the Event Horizon Telescope (EHT) was developed. This involves linking numerous radio telescopes together so they can jointly examine a single target and gather data on it.

To image M87*, eight of the world’s most powerful radio telescopes and telescope arrays were linked together. Over a period of about a week in 2017, they were used to gather 4 petabytes of data about the light from M87* in the millimetre wavelength. The drives containing this data were then physically shipped from the observatories to the Haystack Observatory and the Max Planck Institute for Radio Astronomy, where they were plugged into a  grid computer made from about 800 CPUs linked through a 40 Gbit/s network, with the data processed by four independent teams using a series of tested algorithms to ascertain the reliability of the results. The final processing run was completed using the two most established algorithms to produce the image seen here.

This is in fact only the first galactic black hole image to b released. As well as studying M87*, the global EHT array has also gathered data on the black hole at the centre of our galaxy (and called Sagittarius A*), and at least two other supermassive black holes. However, imaging our own galactic black hole proved much harder, and delays in getting the physical hardware containing the data captured by the South Pole Telescope shipped from Antarctica to the Haystack Observatory has  meant that processing the data is still in progress.

According to theoretical physics – such as Einstein’s theory of relativity – scientists already knew what the image should look like: the aforementioned glowing accretion disk and the shadow of the black hole at its centre (so beloved of sci-fi films that feature black holes). However, simply seeing an image that matches what we believe we should be theoretically seeing helps further confirm Einstein’s theories about the nature of the universe around us.

Theoretical physics, such as Einstein’s general theory of relativity, had given scientists a means of simulating what an image of a black hole might look like, as with the above picture of M87*, released by the EHT team in April 2017 as they were about to commence their data gathering. Credit: Bronzwaer/Davelaar/Moscibrodzka/Falcke, Radboud University

From the actual image on M87*, scientists have already been able to confirm Einstein’s general theory of relativity under extreme conditions – notably the prediction of a dark shadow-like region, caused by gravitational bending and capture of light. They have also confirmed the shadow is consistent with expectations for that of a spinning Kerr black hole, which Einstein again predicted. Further, by combining the asymmetric nature of the accretion disk with the angle of the relativistic plasma jet created by M87* (not actually visible in the black hole image), astronomers believe M87* is spinning in a clockwise direction.

Further, the image has refined estimates of M87*’s size – 40 billion km across the event horizon (that’s 270 AU or 0.0042 light years; roughly 2.5 times smaller than the shadow circle shown in the image) – and its mass, estimated at 6.5 billion solar masses (± 0.7 billion).

We have taken the first picture of a black hole. This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.

– Sheperd S. Doeleman, EHT project director

The image itself is shown in false colour to indicate the intensity of the emissions from the accretion disk. Yellow represents the most intense emissions, dropping to red as the lower intensity emissions, and black for little or no emissions. Were we able to see M87* with the naked eye, the colours would lightly be white, perhaps slightly tainted with blue or red. And while it has yet to be 100% confirmed, the colour bias towards yellow on the southern arc of the ring, together with its asymmetry, is thought to be the result of the gases in that region moving more in our general direction.

While this image has already revealed much, there are numerous questions we have yet to fathom. We may now know the nature of M87*, but we still don’t know how it was formed, or why so many galaxies have black holes at their centres. Nor do we as yet understand why some (like M87*) produce the great plumes of relativistic gas while others, such as the black hole at the centre of our galaxy do not.  So expect more to come as a result of studies arising from the work of EHT.

Continue reading “Space Sunday: black holes, Falcons and moonshots”

Empty rooms, chocolate factories and kaleidoscopes

Seanchai Library

It’s time to highlight another week of storytelling in Voice by the staff and volunteers at the Seanchai Library. As always, all times SLT, and events are held at the Library’s home at Holly Kai Park, unless otherwise indicated.

Sunday, April 14th:

13:30 Tea-Time with Sherlock Holmes’ Greatest Hits

Illustration by Sidney Paget, in The Strand Magazine

As voted for by Seanchai fans, followers and listeners. This week: The Adventure of the Empty Room, first published in The Strand magazine, and later the 13 stories from The Return of Sherlock Holmes.

Three years after the Death of Sherlock Holmes during his fight with Professor Moriarty at Reichenbach Falls, John Watson investigates the death of Ronald Adair. The young gentleman had been found shot to death in a closed room at his home in Park Lane, with no possible exit through the windows. A quiet young man, Adair’s only hobby was playing cards, and he had just had won £240 with his new partner, one Colonel Sebastian Moran.

As he examines the area around Adair’s house, Watson encounters an old man who eventually follows him to his office – and reveals himself to be Holmes himself. Explaining how he survived his encounter with Moriarty to a shocked Watson, he further reveals that Adair’s card partner, Sebastian Moran is – or was – actually Moriarity’s lieutenant. He further reveals that Moran is aware of Holmes’ survival, and plans to kill him.

But knowing of Moran’s plan, Holmes has one of his own. Not only does he plan to survive the attempt on his life, he plans to thwart Moran and bring him to justice.

With Da5id Abbot, Corwyn Allen, Savanah Blindside, and Kayden Oconnell in the Library’s Fireside Room.

18:00 Magicland Storytime: Charlie and the Chocolate Factory

Have you heard? Willie Wonka is releasing five golden tickets in candy bars! Charlie Bucket may have a chance to find one as Caledonia Skytower continues Roald Dahl’s classic.

Monday, April 15th 19:00: The World’s Best Science Fiction 1969

Gyro Muggins read from this anthology of science fiction short stories, edited by Donald A. Wollheim, featuring nineteen authors, including such names as Brian Aldiss, Poul Anderson, Samuel R. Delany, Fritz Leiber, Robert Silverberg, and Kurt Vonnegut, Jr.

This week, Dance of the Changer by Terry Carr. Are the aliens crazy or just alien? Is there a difference? ; and Fear Hound by Katherine MacLean. A detective novel, but this time it isn’t “elementary” it’s “psychic.”

Tuesday, April 16th 19:00: Kaleidoscope

When a brilliant young violinist dies in a horrific accident, Madame Karitska has only to hold the victim’s instrument in her hands to perceive the shocking truth. But when an insecure wife asks whether her husband will abandon her to join a sinister cult, Madame Karitska–as wise as she is lovely–chooses not to reveal all that she foresees. And when an attaché case is suddenly dropped into her lap by a man fleeing a crowded subway, she knows it’s time to consult her good friend Detective-Lieutenant Pruden.

A nine-year-old accused of murder, a man dying a slow death by witchcraft– for the hunted and the haunted, Madame Karitska’s shabby downtown apartment becomes a haven, where brilliant patterns of violence, greed, passion, and strange obsessions mix and disintegrate with stunning, kaleidoscopic beauty.

With Caledonia Skytower.

Wednesday, April 17th 19:00: TBA

Check the Seanchai Library website for information nearer the day.

Thursday, April 18th

19:00: Rogue One: A Star Wars Story Part 2

With Shandon Loring. (Also in Kitely grid.kitely.com:8002:SEANCHAI).

21:00: Seanchai Late Night

Contemporary Sci-Fi Fantasy with Finn Zeddmore.