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justin stewart

I hope you’re all being gentle with yourself

Black Holes: Seeing the Invisible!

Black holes are some of the most bizarre and fascinating objects in the cosmos. Astronomers want to study lots of them, but there’s one big problem – black holes are invisible! Since they don’t emit any light, it’s pretty tough to find them lurking in the inky void of space. Fortunately there are a few different ways we can “see” black holes indirectly by watching how they affect their surroundings.

Speedy stars

If you’ve spent some time stargazing, you know what a calm, peaceful place our universe can be. But did you know that a monster is hiding right in the heart of our Milky Way galaxy? Astronomers noticed stars zipping superfast around something we can’t see at the center of the galaxy, about 10 million miles per hour! The stars must be circling a supermassive black hole. No other object would have strong enough gravity to keep them from flying off into space.

Two astrophysicists won half of the Nobel Prize in Physics last year for revealing this dark secret. The black hole is truly monstrous, weighing about four million times as much as our Sun! And it seems our home galaxy is no exception – our Hubble Space Telescope has revealed that the hubs of most galaxies contain supermassive black holes.

Shadowy silhouettes

Technology has advanced enough that we’ve been able to spot one of these supermassive black holes in a nearby galaxy. In 2019, astronomers took the first-ever picture of a black hole in a galaxy called M87, which is about 55 million light-years away. They used an international network of radio telescopes called the Event Horizon Telescope.

In the image, we can see some light from hot gas surrounding a dark shape. While we still can’t see the black hole itself, we can see the “shadow” it casts on the bright backdrop.

Shattered stars

Black holes can come in a smaller variety, too. When a massive star runs out of the fuel it uses to shine, it collapses in on itself. These lightweight or “stellar-mass” black holes are only about 5-20 times as massive as the Sun. They’re scattered throughout the galaxy in the same places where we find stars, since that’s how they began their lives. Some of them started out with a companion star, and so far that’s been our best clue to find them.

Some black holes steal material from their companion star. As the material falls onto the black hole, it gets superhot and lights up in X-rays. The first confirmed black hole astronomers discovered, called Cygnus X-1, was found this way.

If a star comes too close to a supermassive black hole, the effect is even more dramatic! Instead of just siphoning material from the star like a smaller black hole would do, a supermassive black hole will completely tear the star apart into a stream of gas. This is called a tidal disruption event.

Making waves

But what if two companion stars both turn into black holes? They may eventually collide with each other to form a larger black hole, sending ripples through space-time – the fabric of the cosmos!

These ripples, called gravitational waves, travel across space at the speed of light. The waves that reach us are extremely weak because space-time is really stiff.

Three scientists received the 2017 Nobel Prize in Physics for using LIGO to observe gravitational waves that were sent out from colliding stellar-mass black holes. Though gravitational waves are hard to detect, they offer a way to find black holes without having to see any light.

We’re teaming up with the European Space Agency for a mission called LISA, which stands for Laser Interferometer Space Antenna. When it launches in the 2030s, it will detect gravitational waves from merging supermassive black holes – a likely sign of colliding galaxies!

Rogue black holes

So we have a few ways to find black holes by seeing stuff that’s close to them. But astronomers think there could be 100 million black holes roaming the galaxy solo. Fortunately, our Nancy Grace Roman Space Telescope will provide a way to “see” these isolated black holes, too.

Roman will find solitary black holes when they pass in front of more distant stars from our vantage point. The black hole’s gravity will warp the starlight in ways that reveal its presence. In some cases we can figure out a black hole’s mass and distance this way, and even estimate how fast it’s moving through the galaxy.

For more about black holes, check out these Tumblr posts!

⚫ Gobble Up These Black (Hole) Friday Deals!

⚫ Hubble’s 5 Weirdest Black Hole Discoveries

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

Nicolas Geiser - Almost, 2015, stylo sur papier, 29,7 x 21 cm

Free Online Language Courses

Here is a masterpost of MOOCs (massive open online courses) that are available, archived, or starting soon. I think they will help those that like to learn with a teacher or with videos.  You can always check the audit course or no certificate option so that you can learn for free.

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Last updated: May 2019

The Sistine Ceiling

Within the vast complex of Vatican City, which is an independent city-state with its own governing body as well as the seat of the Pope in the Roman Catholic faith, is the famed Sistine Chapel (also known as the Venue of the Papal Conclave). The chapel is named after Pope Sixtus IV, who commissioned its restoration in the late 15th century. Originally, it was defined as the chapel of the Vatican fort, known as Cappella Magna. The chapel serves various important functions, from celebrating papal acts to ceremonies of the Catholic rite, but its major religious role is that of the site where cardinals meet to elect the next pope. The building where the Sistine chapel is located of the building very close to St. Peter’s Basilica and the Belvedere Courtyard in the Vatican.

The Sistine Chapel is also the home of 2 magnificent frescoes painted by the famed Michelangelo, the Sistine Ceiling (as it is known by) and later, The Last Judgement. There are also works from other notable Renaissance artists, from the likes of Sandro Botticelli, Pietro Perugino, Pinturicchio, Domenico Ghirlandaio, Cosimo Rosselli, and Luca Signorelli. The ceiling of the Sistine Chapel was originally painted blue and covered with golden stars (think of the ceiling of Sainte-Chapelle’s lower chapel). In 1508, Pope Julius II (1503-1513) commissioned Michelangelo to paint the ceiling of the chapel, instead of leaving it as it was. The pope wanted the ceiling done in a “ geometric ornament with the 12 apostles placed on spandrels around the decoration”. However, Michelangelo suggested that instead of doing ornamentation, he would do a painting of scenes from the Old Testament. Although, at the time, Michelangelo had been known more for his work in sculpture (as he had recently completed his famous sculpture of the Pietá as well as his statue of David, both of which reside in the Vatican) rather than painting. But, never one to be daunted, Michelangelo rose to the challenge and went on to create one of the most famous fresco masterpieces in Western art!

𐰸 Rendering of the Sistine chapel before Michelangelo worked his magic on it 𐰸

The ceiling of the chapel is made up of 33 separate areas, each space containing a different scene. Each scene is divided using a technique called trompe-l'oeil (visual deception, especially in paintings, in which objects are rendered in extremely fine detail emphasizing the illusion of tactile and spatial qualities), giving the impression that each painting is divided by physical molding within the vault. They are painted in monochromatic colors, creating a spatial effect between each panel. In the center of the ceiling is a series of nine narrative paintings, depicting scenes from the book of Genesis. There are five smaller scenes, each framed and supported by four naked youths or Ignudi. The scenes start with the Creation of the World (Gen. 1) and end with Noah and the Flood (Gen 6:9).

The subject matter was, more than likely, laid out with the help of a cleric from the Vatican (and seeing how this was the home of the pope, he wanted to be sure to get it right!) The entire project took Michelangelo 4 years to complete and took a grave toll on his health. He penned this poem, describing how his work was taxing both his body and mind:

I’ve grown a goiter by dwelling in this den– As cats from stagnant streams in Lombardy, Or in what other land they hap to be– Which drives the belly close beneath the chin: My beard turns up to heaven; my nape falls in, Fixed on my spine: my breast-bone visibly Grows like a harp: a rich embroidery Bedews my face from brush-drops thick and thin. My loins into my paunch like levers grind: My buttock like a crupper bears my weight; My feet unguided wander to and fro; In front my skin grows loose and long; behind, By bending it becomes more taut and strait; Crosswise I strain me like a Syrian bow: Whence false and quaint, I know, Must be the fruit of squinting brain and eye; For ill can aim the gun that bends awry. Come then, Giovanni, try To succor my dead pictures and my fame; Since foul I fare and painting is my shame.

The main theme of the frescoes is that of the connection between humans and God, and nowhere is this more evident than in the panel, The Creation of Adam. We are given a breathtaking vision of the spirit of God embodied as a human form, reaching across the heavens, just out of reach of Adam, who lazily reclines on a barren earth. This contact point has previously been described as a spark or current, an electrical metaphor which would be unknown to those in the sixteenth century. Nonetheless, it seems quite a fitting description, considering that the lifeblood which is about to flow into the awaiting Adam is similar to the flow of electric current produced when a wire is connected to a power source. In this case, the power source being God. This particular piece is world-famous and has been reproduced hundreds of thousands of times. And we can see why. It is such a powerful image.

At either end of the ceiling, and beneath the scenes are Prophets and Sibyls (a female prophet or witch, a nod to the pagan beginnings of religion) seated on grandiose thrones that alternate along the long sides, while the shorter sides are taken over by the figures of Zechariah and Jonah (situated above the altar) who has a distinguished position in so much as he is the adumbration of Christ. The crescent-shaped areas, or lunettes, above each of the chapel windows are tablets listing the forerunners of Christ and their accompanying figures. Above them, in the spandrels (the space between the shoulders of adjoining arches and the ceiling or molding above), eight groups of figures are displayed (however, they have not been identified with specific biblical characters). The entire narrative is finished off by four large corner pendentives (a curved triangle of vaulting formed by the intersection of a dome with its supporting arches) each one portraying a dramatic Biblical story. All of this illustrates the connections to Christ, before and after His birth and death, which are embodied in these paintings.

𐰸 map of the architectural features of the Sistine Ceiling 𐰸

𐰸 Guide to the artwork on Sistine Ceiling 𐰸

In 1510, Michelangelo decided that he needed a well-deserved break from this arduous assignment. Upon his return a year later, his style of painting had undergone a noticeable change. Rather than jumbled and multiple images within a scene, as previously done, Michelangelo had decided to minimise details and focus on essential figures, but on a grand scale. Also, he added a strong sense of emotion to the figures as well as dramatic gestures (as in The Creation of Adam). This would enable the viewer on the floor below to have a clear understanding of exactly what the scene was trying to convey. Further, when we look at the commanding figure of God in three of the frescoes, it clearly illustrates the separation of darkness from light, the creation of the heavens and the earth, all radiating its power through God’s body. The influence of these works cannot be emphasized enough. The complexity of design in the individual figures display Michelangelo’s skill in creating a variety of poses for the human figure. His stupendous works have turned the Sistine Chapel into a veritable academy for future artists!

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