The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "milkyway galaxy"

  • Are all stars confined to certain galaxies?
  • Yes. In fact, our Sun and the stars we see in our night sky are all confined to the Milky Way galaxy. It is very difficult for people to see the stars of other galaxies because they are so distant. The nearest galaxy is the Andromeda galaxy, which is more than 2 million light years away. This galaxy can be seen in the summer skies in the Andromeda constellation, but you need to get far away from city lights. It will appear as a faint fuzzy object in the sky. If you look at pictures of galaxies taken from the Hubble Space Telescope and others, you may be able to pick out some of the brightest stars, but they are only visible to very large telescopes that have taken very long exposures of the sky.

    (Tags:  andromeda galaxy  milkyway galaxy  star  sun)
  • 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)
  • How do we know what the Milky Way galaxy looks like, if we cannot travel outside it?
  • Astronomers are not certain exactly what the galaxy looks like. But by using telescopes that see in visible, infrared and ultraviolet light, we are able to plot the positions of the stars and get a good guess of what the galaxy would look like, if we could leave it. It helps that we have so many other known galaxies to compare ourselves to.

    (Tags:  milkyway galaxy)
  • 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 we were to reach the end of the universe, what would prevent us from going further?
  • There is no end to the universe. It continues to expand and cool and shows no sign of stopping. In fact, the expansion is accelerating. We are trying to discover what is causing the accelerated expansion. What we do know is that with our current technology it takes decades to get to the outer part of the solar system. It would take hundreds of thousands of years to get to the nearest star. And it would be impossible to leave the Milky Way (let alone the rest of the universe). Even if we could develop the technology to travel at the speed of light, it would still take 30,000 years to leave the Milky Way. The nearest galaxy to us is the Andromeda Galaxy which is 2.5 million light years away (meaning it would take 2.5 million years to reach it, travelling at the speed of light). These distances are just too great to be able to travel them and hope to reach an end of the universe.

    (Tags:  milkyway galaxy  speed of light  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 everything we see in the universe on fire or able to be seen because it is reflecting light from something on fire?
  • The answer kind of depends on what you are referring to. Take the planets of our solar system for example. They do not create their own light, they are just reflecting the Sun’s light back to us, the same is true for our Moon. On the other hand, the Sun, stars, galaxies and nebulae are all creating their own light. But I wouldn't say that they are on fire. It is true that astronomers talk about stars “burning” but we aren't referring to a fire like you may create in your fireplace or grill. What’s actually happening is Hydrogen atoms in the center of the star (like our Sun) are fusing to form Helium atoms. This creates an incredible amount of heat and light. The Sun is more than 10,000 degrees Fahrenheit!

    (Tags:  hydrogen  light  milkyway galaxy  moon  planet  star  sun)
  • 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)
  • When will the Milky Way collide with Andromeda? Are those estimates accurate?
  • The Andromeda Galaxy will collide with the Milkyway in 3 billion years as they are separated by 2.2 million light years and approaching to each other at approximately 500,000 km/hour speed. Are those numbers accurate? Yes and No. We measure distances and velocities accurately. That would allow us to give a specific date and time for the collision, if the galaxies were like solid objects. However, galaxy collisions are not similar to collision of 2 vehicles. Galaxies don’t have sharp boundaries that you can tell when the collision starts. Moreover, the collision will last approximately 1 billion years. During the collision, it is unlikely that any star will run into another! If there is life on a planet at that time, probably the life will not be affected. After the collision, galaxies change their shape, they either merge or form 2 “new” galaxies orbiting each other. Based on scientific data, numerous simulations have been computed and galaxy collision animations created. More specific information and animations can be found at the following link:

    (Tags:  andromeda galaxy  milkyway galaxy  physics  star  universe)