Elucidating The Black Holes
"Black holes" is one of the most highly searched terms about our universe. There's a fascination with the idea of a region of space having a gravitational pull so strong, nothing can escape its deadly grasp, not even a sliver of light. Well, not quite. In fact, much of what we think we know about black holes turn out to be myths.
Myth 1 - All black holes are black. As the photograph below from the Event Horizon telescope demonstrated, light can be detected near a black hole's event horizon. This is the boundary between normal space and the space affected by the black hole's gravity, from which no escape is possible. Part of this light comes from the black hole's accretion disk, a flat, pancake like structure composed of dust, gas and other debris. Friction constantly moves the disk's material inward toward the event horizon. Light also comes from jet streams which propel matter outward along the disk's north and south poles.
Myth 2: All black holes are about the same size. Black holes actually come in several different sizes which are defined by their mass. Small black holes are usually the result of a relatively short and violent collapse of a star. Recent work suggests that Intermediate black holes are found in the nuclei of some active galaxies. Super massive black holes on the other hand, are found at the center of nearly every galaxy.
Dr. Dan Evans, an Astrophysicist at NASA Headquarters says, "There's a direct relationship between the beginning of super massive black holes and the beginning of their corresponding galaxy. This strongly suggests the two were born about the same time and slowly grew in size together over billions of years."
Myth 3: If you get within a few thousand miles of a black hole, its super gravity will pull you into its center. It turns out you can get surprisingly close to a black hole. If you approached a black hole with mass equal to our Sun's for example, you could get as close as tens of miles. So imagine if we replaced our sun with a black hole of the same mass. All of the planets would continue to revolve around it, at exactly the same speed and distance as they do now.
Myth 4: Once inside a black hole, nothing ever comes out. Nope. It turns out that radiation can escape from a black hole. One of Stephen Hawking's contributions was a theory that a black hole is not so dense in a quantum mechanical sense. The slow leak of what's now known as Hawking radiation would, over time, cause the black hole to simply evaporate.
The image from the Event Horizon telescope confirmed what Albert Einstein's general theory of relativity predicted over 100 years ago - that a black hole's form is that of a perfect circle. And as scientists learn even more about the properties of this gigantic cosmic mystery we call a black hole, they'll be able to puncture even more myths.
Massive Cloud On Collision Course With Milky Way
In 1963, an astronomy student named Gail Smith working at an observatory in the Netherlands discovered something odd-a massive cloud of gas orbiting the Milky Way galaxy.
Smith's cloud contained enough gas to make 2 million stars the size of our sun, and it was moving through space at 700,000 mph.
30 million years from now, a massive cloud of gas will collide with the Milky Way. Astronomers are studying the incoming cloud and learning more about its origin.
Worlds Within Worlds
Astronomers have discovered an immense cloud of hydrogen evaporating from a Neptune-sized planet named GJ 436b. The planet's atmosphere is evaporating because of extreme irradiation from its parent star
Astronomers using Hubble Space Telescope have discovered an immense cloud of hydrogen evaporating from a Neptune-sized planet named GJ 436b. The planet's atmosphere is evaporating because of extreme irradiation from its parent star.
About 30 light years away, a Neptune-sized planet
is having some of its layers peeled back.
Astronomers using 's Hubble Space Telescope have discovered an immense cloud of hydrogen evaporating from a Neptune-sized planet named GJ 436b.
This cloud is spectacular. The research team has nicknamed it The 'Behemoth.'
The planet's atmosphere is evaporating because of extreme irradiation from its parent star-a process that might have been even more intense in the past.
The parent star, which is a faint red dwarf, was once more active. This means that the planet's atmosphere evaporated faster during its first billion years of existence. Overall, we estimate that the planet may have lost up to 10 percent of its atmosphere.
GJ 436b is considered to be a Warm Neptune because of its size and because it is much closer to its parent star than Neptune is to our own sun. Orbiting at a distance of less than 3 million miles, It whips around the central red dwarf in just 2.6 Earth days. For comparison, the Earth is 93 million miles from the sun and orbits it every 365.24 days.
Systems like GJ 436b could explain the existence of so-called Hot Super-Earths.
Hot Super-Earths are larger, hotter versions of our own planet. Space telescopes such as 's Kepler and the French led CoRoT have discovered hundredsof them orbiting distant stars. The existence of The Behemoth suggests that Hot Super-Earths could be the remnants of Warm Neptunes that completely lost their gaseous atmospheres to evaporation.
Finding a cloud around GJ 436b required Hubble's ultraviolet vision. Earth's atmosphere blocks most ultraviolet light so only a space telescope like Hubble could make the crucial observations.
You would not see The Behemoth in visible wavelengths because it is optically transparent. On the other hand, it is opaque to UV rays. So when you turn the ultraviolet eye of Hubble onto the system, it's really kind of a transformation because the planet turns into a monstrous thing.
The ultraviolet technique could be a game-changer in exoplanet studies, he adds. Ehrenreich expects that astronomers will find thousands of Warm Neptunes and Super-Earths in the years ahead. Astronomers will want to examine them for evidence of evaporation. Moreover, the ultraviolet technique might be able to spot the signature of oceans evaporating on Earth-like planets, shedding new light on worlds akin to our own.
Maybe you can't judge a book by its cover, but you
can judge a planet by its Behemoth.
