The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "black hole"

  • Can we experience weightlessness near a black hole?
  • I don’t think that you would feel weightless around a black hole, because the difference in gravity between your head and feet is so great that you will be stretched into a long thin string. Even if you can get into a fast orbit around the black hole that would attempt to balance the gravitational forces, creating a free fall situation (exactly the same situation the astronauts have around Earth) you would still feel this stretching on your body. Some astronomers like to call this stretching effect, spaghettification, because it stretches you into a thin piece of spaghetti. You will eventually become stretched so much, that the bonds holding your atoms together will break, so it won’t be you that enters the black hole, but the protons, neutrons and electrons that make you up.

    (Tags:  black hole  gravity)
  • Could phenomena occur where planets align in a way that impacts Earth?
  • There are no planetary alignments in the next few decades, Earth will not cross the galactic plane in 2012, and even if these alignments were to occur, their effects on the Earth would be negligible. Each December the Earth and Sun align with the approximate center of the Milky Way Galaxy but that is an annual event of no consequence.

    (Tags:  2012  apocalypse  black hole  earth  gravity  milkyway galaxy)
  • Do rogue or lonely things in space such as stars, planets, etc exist... or is everything a part of a group of some sort?
  • Not everything in the universe is grouped together. Astronomers have started to find planets that are not attached to a parent star. And theory tells us black holes and stars can be flung out of galaxies when they collide.

    (Tags:  black hole  exoplanet  planet  star)
  • How can an astronomer test to see if gas and dust from a star are being drawn into a black hole?
  • There are two ways of knowing this: 1. When dust and gas approaches a black hole, strong gravitational forces spin the dust and gas nearly at the speed of light. Accelerating particles produce X-ray radiation which radiates perpendicular to the orbital plane of the gas and dust. We can detect this radiation if the radiation direction is just right (towards Earth). The first discovered black hole, Cygnus X-1, was detected this way. 2. Computer simulations suggest if a star is nearby a black hole, star atmosphere (dust and gas around stars) would be pulled by the gravity of the black hole.

    (Tags:  black hole  gravity  light  physics  star  universe)
  • How can black holes be so small but have such an incredibly large mass?
  • The mass of a black hole is determined by the mass of the star. When a star explodes as a supernova, much of the matter is sent into space, but the core of the star remains and collapses in on itself until a black hole is formed. The mass gets compressed so much that the electrons combine with protons in the nucleus of an atom - creating neutrons. If the compression stops the core becomes a neutron star instead of a black hole. Astrophysicists are not sure how matter can condense further than this to create a black hole because this process is unexplained by our current understanding of the universe. We can determine the radius of a black hole however, using an equation called the Schwarzschild radius. For a black hole of mass m, the Schwarzschild radius RS is given by RS = 2Gm/c2, where G is the universal gravitational constant and c is the speed of light. The Schwarzschild radius for a black hole of solar mass is about 3 km/1.9 mi.

    (Tags:  black hole  gravity  neutron star  physics  supernova)
  • How might the sky appear if we were in the Milky Way center?
  • There are a few ways to answer your question. The first is that the sky would probably be dark, because if we were at the center of the galaxy, then we would find ourselves in the middle of a black hole. But, if we are near the center of the galaxy, or we remove the black hole, the view would be very different from the view we are used to on Earth. There would be a higher density of stars around us in the sky, with no visible Milky Way band (like we see in the real night sky). Our constellations would also change rather rapidly, as the stars closest to the center of the Milky Way orbit rapidly and chaotically around the center of the galaxy.

    (Tags:  black hole  milkyway galaxy  star)
  • If a black hole is a tunnel in a new universe, why haven't humans tried to explore it yet?
  • There are a few reasons why humans haven't yet explored a black hole to see if there is a tunnel to another universe. Right now, astronomers and mathematicians have proven that it is mathematically possible that a black hole is a gateway to another universe -- sometimes called a white hole, or worm hole. But, we have no way to test if this is actually true. The closest black hole is many thousands of light years away, which means that if we were traveling at the speed of light - which is currently impossible — it would take a few thousand years to reach the black hole. Then, if we can imagine that we have made it to the black hole, once a person or satellite enters the black hole, we will no longer receive any transmissions from them because they will be caught in the black hole’s extreme gravity. This means that even if we could safely send someone through the black hole, we would never know what happened to them, regardless if they made it through safely or not.

    (Tags:  astronaut  black hole  gravity  physics  theory of general relativity  universe)
  • In pictures of a galaxy, I notice a big bright star in the center, is that really a gigantic star and how come I can't see that star in the night sky of the milky way?
  • First, when you are looking at a picture of a galaxy, you are not looking at our galaxy the Milky Way. The Milky Way galaxy is about 30,000 light years across, a distance far to great for us to reach. So we have never left our Milky Way galaxy to see it from above. Second, what you did see in the galaxy image was probably not one bright star but hundreds. At the center of most galaxies we have found evidence of supermassive black holes (hundreds of times the size of our sun). Orbiting around this black hole are hundreds, even thousands of very large hot stars that would glow very brightly. This is what you are seeing when you look at images of galaxies. Third, let's imagine for a moment that the galaxy image you were looking at was our Milky Way galaxy, and you went looking for the bright object in our sky. You would still not see the bright object at the center. We know this to be true because when we look towards the center of the Milky Way (near the constellation Sagittarius) we can not see the very center because there is a lot of gas and dust, called Interstellar Material, that is blocking our view. The only way that astronomers can study the center of our Milky Way galaxy is by looking at the Infrared light (heat energy) of stars, since it is the only form of energy which does not get absorbed by clouds of gas and dust.

    (Tags:  andromeda galaxy  astronomy  black hole  light  milkyway galaxy  star  universe)
  • Is a black hole a tunnel to another part of the Universe?
  • Not sure. There is an idea that under extreme conditions you could tunnel in this way, but it is all theory at this point.

    (Tags:  black hole  universe)
  • The center point of the Moon's rotation is Earth, the center point of the Earth;s rotation is the Sun, the center point of the Sun's rotation is the black hole at center of our galaxy; does that mean that the universe has a central point that can be pinpointed provided we had the instruments to measure this vast distance?
  • The center of the universe would be the location where the Big Bang happened. Since that time, all matter has moved uniformly away from this point in all directions. This expansion of the universe is still happening today and is actually accelerating. So instead of orbiting some central part of the universe, the universe is actually moving away from the center. Scientists are trying to discover what is causing the acceleration of the expansion of our universe.

    (Tags:  big bang  black hole  earth  milkyway galaxy  moon  sun  universe)
  • There's so much talk about the alignment of the earth and sun on 12-21-2012...But what about the other planets in the same alignment? Do solar flares affect other planets when they align with the sun and the blackhole?
  • We’ve answered the first half of the question before. There are no planetary alignments in the next few decades, Earth will not cross the galactic plane in 2012, and even if these alignments were to occur, their effects on the Earth would be negligible. Each December the Earth and Sun align with the approximate center of the Milky Way Galaxy but that is an annual event of no consequence. The black hole at the center of the galaxy is over 26,000 light years away (meaning it would take 26,000 years to reach it if you were travelling at 186,000 miles per second!) This is incredibly far away, so it’s effects are not noticeable to us. Solar flares are not at all related to the black hole at the center of the galaxy. Solar flares are a natural occurrence on all stars. The number of flares and sunspots seen on the Sun changes on an 11 year cycle. Currently we are nearing a solar maximum, meaning there is an increase in solar activity including flares. The effects of these flares are seen on the other planets too. NASA has many pictures of auroral displays on Jupiter and Saturn.

    (Tags:  2012  apocalypse  black hole  milkyway galaxy  planet  solar system  star  sun)
  • What determines the outcome of a supernova? Is there a way to know if it will become a black hole instead of a neutron star?
  • The mass of the star is what determines what will happen to it after it goes supernova. All massive stars go supernova, but after they explode, the core of the star remains. Small cores will become neutron stars, larger cores will continue collapsing until they turn into a black hole.

    (Tags:  black hole  neutron star  star  supernova)
  • What happens if you get too close to a black hole?
  • Near the visible edge of the black hole (called the "event horizon") gravitational forces are so great that you would be stretched out like a long piece of spaghetti. Eventually your atoms and molecules would be ripped apart, and your mass would add to the mass of the black hole.

    (Tags:  black hole  gravity)
  • What is a black hole?
  • A black hole is what happens to large stars when they run out of energy. During the main part of a its life, a star exists in a balance. Gravity tries to pull the star in closer to the middle and energy pressure pushes the star out from the core. These forces cancel out for most of the star's life. When the energy production quits in large stars, gravity pulls the star in rapidly and violently, creating a shockwave which blasts apart the outer part of the star. The inner part continues to collapse from the gravity, to the point where the gravity becomes "infinite." Nothing can get out of this corpse star, not even light, which is pulled down by the gravity, as well.

    (Tags:  black hole  gravity  light  sun)
  • What is the difference between a gamma ray burst and a supernova?
  • A gamma ray burst is thought to originate from a black hole when it takes in a large amount of mass in a short time. A supernova is the explosive death of a large star, which can lead to the formation of a neutron star or a black hole, depending on the mass of the object after it goes supernova.

    (Tags:  black hole  gamma ray burst  neutron star  star  supernova)
  • When is the Sun predicted to become a black hole?
  • The Sun will never become a black hole. A black hole is what remains after a star, many times larger than the Sun, dies. The star will explode in a supernova, and then collapse in on itself, until it disappears completely, leaving only its gravity behind. The Sun, which is too small to become a black hole, will die. In about 5 billion years, the Sun will use up all its Hydrogen, and expand. Then it will shoot off the outer layers of the atmosphere, leaving just the core behind. We see many examples of stars that have died this way, just search the internet for pictures of Planetary Nebulae. One of the most famous of these planetary nebulae is the Ring Nebula, in the constellation of Lyra, the Harp.

    (Tags:  black hole  gravity  physics  star  sun)