Gently singing Twinkle, twinkle, little star may lull a baby to sleep, but beyond the confines of Earth’s atmosphere, the words aren’t exactly accurate. A correct, albeit less soothing, rendition might be: Emit, emit, gigantic ball of gas. Stars are huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores. Aside from our sun, the dots of light we see in the sky are all light-years from Earth. They are the building blocks of galaxies, of which there are billions in the universe. It’s impossible to know how many stars exist, but astronomers estimate that in our Milky Way galaxy alone, there are about 300 billion. The life cycle of a star spans billions of years. As a general rule, the more massive the star, the shorter its life span.

Birth takes place inside hydrogen-based dust clouds called nebulae. Over the course of thousands of years, gravity causes pockets of dense matter inside the nebula to collapse under their own weight. One of these contracting masses of gas, known as a protostar, represents a star’s nascent phase. Because the dust in the nebulae obscures them, protostars can be difficult for astronomers to detect. As a protostar gets smaller, it spins faster because of the conservation of angular momentum—the same principle that causes a spinning ice skater to accelerate when she pulls in her arms. Increasing pressure creates rising temperatures, and during this time, a star enters what is known as the relatively brief T Tauri phase. Millions of years later, when the core temperature climbs to about 27 million degrees Fahrenheit (15 million degrees Celsius), nuclear fusion begins, igniting the core and setting off the next—and longest—stage of a star’s life, known as its main sequence. Most of the stars in our galaxy, including the sun, are categorized as main sequence stars. They exist in a stable state of nuclear fusion, converting hydrogen to helium and radiating x-rays. This process emits an enormous amount of energy, keeping the star hot and shining brightly.

Let's Talk about Black Holes

Black holes are among the strangest things in the universe. They are massive objects – collections of mass – with gravity so strong that nothing can escape, not even light. The most common types of black holes are the stellar-mass and supermassive black holes. Stellar-mass black holes are created when massive stars explode, leaving behind a black hole with the mass of just a few suns. Supermassive black holes exist in the hearts of galaxies and usually contain the mass equivalent of millions of suns.

The massive gravitational influence of a black hole distorts space and time in the near neighbourhood. The closer you get to a black hole, the slower time runs. Material that gets too close to a black hole gets sucked in and can never escape.

Black holes have this incredible ability to literally stretch you into a long spaghetti-like strand. Appropriately, this phenomenon is called 'spaghettification'. Look it up. The way it works has to do with how gravity behaves over distance. Right now, your feet are closer to the centre of Earth and are therefore more strongly attracted than your head. Under extreme gravity, say, near a black hole, that difference in attraction will actually start working against you. As your feet begin to get stretched by gravity's pull, they will become increasingly more attracted as they inch closer to the centre of the black hole. The closer they get, the faster they move. But the top half of your body is farther away and so is not moving toward the centre as fast. The result: spaghettification!

The “point of no return” around a black hole is called the “event horizon”. This is the region where the gravity of the black hole overcomes the momentum of material spinning around it in the accretion disk. Once something cross the event horizon, it is lost to the pull of the black hole.

First Black Hole Photo

This is what a black hole looks like. A black hole isn’t really a hole. It’s an object in space with incredible mass packed into a very small area. All that mass creates such a huge gravitational tug that nothing can escape a black hole, including light.

“We have seen what we thought was unseeable,” Sheperd Doeleman said April 10 in Washington, D.C. “We have seen and taken a picture of a black hole,” he reported at one of seven concurrent news conferences. Doeleman is EHT’s director. He also is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Results from his team's work appear in six papers in the Astrophysical Journal Letters. The concept of a black hole was first hinted at back in the 1780s. The mathematics behind them came from Albert Einstein’s 1915 general theory of relativity. And the phenomenon got its name “black hole” in the 1960s. But until now, all “pictures” of black holes have been illustrations or simulations.

WHAT IS A PLANET?

The answer to this question is a highly controversial one. This has not always been the case, though. In fact, before 1978 the definition of a “planet” was not really necessary. Until that time a planet simply meant a body in orbit around the Sun, that reflected sunlight, and was not a planetary moon, asteroid, or comet. However, with the discovery of Pluto’s moon Charon in 1978 scientists were able to calculate Pluto’s mass much more accurately than ever before and soon realized that it was much smaller than they had previously believed. At a tiny fraction of the mass of Mercury, Pluto was clearly a body much smaller than any other planet. This discovery led some to question whether Pluto was actually a planet or some other type of object. In the 1990s and early 2000s the discovery of several objects in the outer solar system similar in size to Pluto made it all but necessary to come to a definitive definition of a planet. Such a definition was needed to separate those types of objects like Pluto into a distinct class, otherwise all of the newly found objects would have to be called planets as well. In response to this uncertainty, the International Astronomical Union (IAU), the official governing body for matters concerning naming astronomical objects, came to a definition of the term “planet.” According to the IAU, a planet is a celestial body that meets the following criteria: is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and has cleared the neighbourhood around its orbit.

But before we end this, I want you to watch this and be with me until in the end...