![]() ![]() We cannot observe our own past that way, but we can do the next best thing: All our current knowledge points towards the fact that, on average, the universe is the same everywhere. If we point our telescopes at one of our nearest neighbors, the Andromeda galaxy M31, we see that galaxy as it was 2.5 million years ago, because it took the light we receive now 2.5 million years to travel from Andromeda to us. Keeping track of change is possible because astronomers always look into the past. Keep track of how those inventories change over time, reconstruct the supply chain, and you can learn about the production history of stars. There is a huge reservoir of ionized hydrogen in the vast spaces between galaxies, warm intergalactic plasma that contains more than 90% of all hydrogen in the universe. The atomic hydrogen inventory can be replenished as well. Such cool gas is produced when a sufficiently dense cloud of warmer gas made of hydrogen atoms cools down – under the right conditions, the hydrogen atoms pair off, each pair forming a hydrogen molecule H 2. In order to produce stars, we need cool gas made of hydrogen molecules. Stars form whenever the conditions are right for them to form, whenever the right material is available. When galaxies form stars, there is of course no planning behind it, economic or otherwise. Documenting the factory's inventory of the necessary components or raw material is a useful way of learning about the production history. If supplies are missing, production will slow down, or might even grind to a halt. Tracing the origin of a common household item, like an appliance, amounts to reconstructing a supply chain: the raw materials transformed into more elaborate components, and those components assembled into a finished product. Dalcanton, Dark Energy Survey, Department of Energy (DOE), Cerro Tololo Inter-American Observatory/NoirLab/National Science Foundation/Association of Universities for Research in Astronomy (AURA), Sloan Digital Sky Survey (SDSS) Acknowledgment: J.Space Telescope Science Institute and ASPECS team ![]() As common as such interactions may be, it is rare to capture an image of two galaxies interacting in such a visibly dynamic way. Galaxies can merge, collide, or brush past one another – each interaction significantly affecting their shapes and structures. The image reveals this process in action as delicate streams of matter visibly link the two galaxies.Īstronomers now accept that an important aspect of how galaxies evolve is the way they interact with one another. When two galaxies tidally interact, gas, dust, and even entire star systems can move toward one galaxy and away from the other. The direction of tidal forces is away from the lower-mass object and toward the higher mass object. Tidal forces occur when an object’s gravity causes another object to distort or stretch. If the image revealed the full emission of both AGNs, their brilliance would obscure the beautifully detailed tidal interactions we see in this image. Interestingly, both galaxies have monumentally energetic cores known as active galactic nuclei (AGN), although that is difficult to tell from this image, which is fortunate. The image shows Arp 282, an interacting galaxy pair composed of the Seyfert galaxy NGC 169 (bottom) and the galaxy IC 1559 (top). This image from the NASA/ESA Hubble Space Telescope feels incredibly three-dimensional for a piece of deep-space imagery. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |