The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "andromeda 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)
  • 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)
  • What technology is used to discover the existence of galaxies?
  • We can see other galaxies with ground and space-based telescopes, like the Hubble Space Telescope, some can even been seen with the unaided eye – like the Andromeda Galaxy. Hundreds of thousands of different galaxies have been seen. A famous image from Hubble, called the Ultra Deep Field Image, shows over 10,000 galaxies in one small part of the sky.

    (Tags:  andromeda galaxy  satellite)
  • 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: http://www.galaxydynamics.org/tflops.html

    (Tags:  andromeda galaxy  milkyway galaxy  physics  star  universe)