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Do you ever wonder about the stars: how did they form, what are they are composed of, why are they different colors, how did the universe form, is there life elsewhere? All of these questions are being answered by measuring light energy, both in the visible (what we can see) and also, at the invisible. Astronomical objects radiate energy in all parts of all wavelengths from long radio waves to short gamma rays. NASA’s Multiwavelength Milky Way project looks at our home galaxy, the Milky Way across the electromagnetic spectrum. It looks at the same area of our galaxy using different wavelengths of energy.
In the game of 20 questions, the more questions asked, and information gathered, the easier it is to identify the object. Why look at the stars and galaxies using more than one energy source? If you start doing a puzzle, but are missing pieces of it you don’t get the complete picture. If you look at the night sky in only say the visible light range, you miss most of the objects and information available. Each type of light, both visible and invisible, gives us different information. In addition, the only way we can explore distant objects is by analyzing the light they emit.
Another name for light is electromagnetic radiation. The full electromagnetic spectrum is shown below. The electromagnetic spectrum is broken up into: radio waves, microwave radiation, infrared radiation(like heat from the sun), visible light (ROYGBIV-rainbow), ultraviolet radiation, x-rays, and gamma radiation (the highest energy).
Astronomers use telescopes to collect light and a variety of energy emissions using detection devices that can sense and analyze light of different wavelengths. These measurements can be represented as color maps that we can see and interpret. Taking a “multi wavelength” approach gives the most complete picture of an object.
The Crab Nebula, first seen in 1054 A.D. is the remnant of a supernova explosion. This explosion was initially so bright, that it could been seen in the daytime sky. Today, a pulsar , a collapsed dense remnant of the exploded star, lies in the center of the Crab Nebula. The nebula itself is comprised of material blown from the exploded star. In the optical range, one can see the outer edges of stellar nebula. In the ultra-violet range, scientists found evidence for a theory on the supernova remnant. Lastly, in the x-ray range, a “condensed core” near the central pulsar in the nebula, shows a strong magnetic field.
Andromeda Galaxy M31
There is more to the universe than meets the eye. Looking at our galaxy in a multiwavelength aspect expands your knowledge of the formation and evolution of our galaxy and opens a window into the universe.
optical milky way image 460x 103 GHz
Since man has walked on Earth the sense of sight has drawn us to the heavens and made us ponder our origins and our future. In this Optical image above , created from eight separate photographs, we see dark patches which are due to absorbing dust clouds, which are also evident in the Atomic Hydrogen and Infrared images (seen below). Because of the obscuration of interstellar gas and dust, the light (image above) that you see comes from stars within a few thousand light years from the sun. Considering our Milky Way is about 100,000 light years in diameter, the optical image gives us a limited but nonetheless spectacular view of the galaxy.
Radio astronomy, for example, has brought a new perspective to astronomy. Objects that appear bright in the optical portion of the spectrum are not necessarily strong radio emitters, and very often, strong radio sources are completely undetectable in visible wavelengths. Radio observations have allowed us to find and study new classes of objects that have previously been completely unknown. Interstellar dust clouds block visible light but not the longer wavelength radio waves. Studying the radio emissions of our galaxy shows us quite well the effects of star formation and evolution. In the 2.7 GHz radio image below, you are seeing the ionized gas of individual star forming regions of gas being ionized.
radio milky way image 2.7 GHz
The Atomic Hydrogen image below, also from radio telescopes, shows us where the raw materials for star formation is located in our galaxy.
radio image of atomic hydrowgen in the milky way 1.4 GHz
In viewing the image above you see the thin layer of hydrogen. Looking at the location of the raw materials and the sites of new star formation can give us glimpses into our galaxy’s past, present and future.
In space, many areas are hidden from optical telescopes because they are embedded in dense regions of interstellar gas and dust. However, infrared light, having wavelengths intermediate between visible and radio wavelengths, can pass through dusty regions of space without being scattered, similar to radio waves. This means we can study objects hidden by dust and gas in the infrared, which we cannot see in visible light, such as the center of our galaxy and areas of newly forming stars. The infrared picture below shows the thermal emission from interstellar clouds warmed by absorbed starlight.
infrared milky way image3.0x103 GHz
The near infrared image below refers to the part of the infrared spectrum that is closest to visible light. It gives us our clearest view of the overall distribution of stars in our galaxy. This image gives us our first good look at the galactic bulge, found
at the center of our galaxy and our first good look at the galactic bulge.
near infrared milky way image 86x103 GHz
When looking at the X-ray image below, you see a clear picture of where hot ionized gas is being emitted.
x-ray milky way image 6.0x 106 GHz
The X-ray image shows perfectly in the right hand corner the emissions of a supernova. This gives a better picture into areas where massive explosions have taken place and where hot, new stars have formed and recently died.
The interactions of cosmic rays with interstellar gas produces gamma rays, the the most energetic form of light. Supernova explosions, and pulsars, are also seen in the gamma ray image below. When looking at this image, bright compact sources stick out, indicating a high energy phenomena.
gamma ray milky way image 2.4 x 10 13 GHz
Through studying the Milky Way at different wavelengths, astronomers can find stellar nurseries and observe star births and deaths. They can find chemical elements (like hydrogen and nitrogen, etc.) in molecules and atoms. In addition, the mysterious black hole in the center of our galaxy is being investigated. The Multiwavelength Milky Way allows us to expand our own visual perceptions of our galaxy and “see” what no one has before.
Credits:
Lisa Alter
Lisa Bruck
Dr. David Leisawitz, COBE Project Scientist
Dr. Beth Brown, National Research Council, Research Associate
Dr. Seth Digel
