It is natural for mankind to look to the heavens and wonder where we are, and where we will be in the future. As humans, it is difficult to grasp how large the Universe is, and yet even more difficult, that it continues to grow. Astrophysicists have dared to ask the question, "What will happen to the Universe?" , and with the help of modern technology, they are aggressively seeking an answer. Due to recent advances in technology scientists have shifted their theories about the Universe expansion and/or contraction in the last five years. Using this technology they have found distant supernovae that suggest the universe is expanding eternally.
To understand what supernovae have to do with the expansion of the Universe, one must know what a supernova is and which type of supernova scientists are looking for. There are two types of supernovae, Type I and Type II. Type I supernovae are the brightest, having a magnitude of -18.6, or 2.5 billion times as bright as our Sun. Type II supernovae only reach about one billion times as birth as our Sun. It is also said that Type I supernova, after reaching their peak brightness, grow dim in a regular fashion. Type II supernovae are said to be much more irregular. There can be seen a clear difference between Type I and Type II in their light spectra. Type I is almost completely missing hydrogen, while Type II has a lot of hydrogen spectral lines. The location of Type II supernovae is in the arms of spiral galaxies. Type I supernovae tend to exist everywhere, in the arms of spiral galaxies and their centers as well as in elliptical galaxies too.
Scientists working on the "Supernova Cosmology Project" find Type Ia supernovae in the hopes they can use them to gain insight and predict the ultimate fate of the Universe. While it is known that the Universe is expanding (Hubble), scientists are striving further to answer the question whether the universe will expand forever, or slow down to a halt , and contract to a point. This contraction is called "The Big Crunch". It doesn't sound like a very pleasant way to end the Universe, eternal expansion is not much better. The Universe would continue to grow cold and dark, until 10 trillion years into the future when the last of the stars would die. (Kahn, The Cosmic Village, fall 1997) "Astrophysicists measure the 'deceleration'--the rate of which the Universe's known continual expansion is slowing down." (Yarris, Jan 16, 1996) If the deceleration is sufficiently large, "The Big Crunch" theory becomes a likely scenario. However, if research leads to a small deceleration, the expansion of the Universe will continue on forever. The current expansion rate, called the "Hubble Constant", compared with the ages of the oldest stars, creates discrepancies that could point to the acceleration of the expansion of the Universe.
Technology for testing these theories has steadily increased. Scientists working with the Supernova Cosmology Project developed an effective way to find and measure Supernovae. "An ultra-sensitive electronic camera attached to a telescope is used to photograph thousands of deep space galaxies at the time of a new moon." (Yarris, Dec. 15, 1995) Another group of images is taken at the next new moon. The two sets of images are compared using a computer, light from the older image is subtracted from the light of the newer image to "reveal the appearance of supernovas." (Yarris, Dec 15, 1995) This technique has been perfected over five years. In 1993, the Supernova Cosmology group found one new supernova, seven new ones in 1994, and eleven new supernovae in 1995 using the more sensitive, updated version of the same technique. The Cerro-Tololo Inter-American Observatory, The Hubble Space Telescope, and the WIYN telescope on Kitt Peak all take measurements of distant supernovae.
Recent observations made by astronomer , Dr. Adam Riess, and a team of scientists from all over the world, show that the universe is not only expanding, but expanding faster than it was seven billion years ago. This discovery was made by observing how fast supernovae were expanding when the star exploded. When the observations were analyzed some more the teams noticed that there was evidence that the cosmological constant had an effect on how fast the star was expanding after it exploded. The cosmological constant acts the opposite of gravity by pushing mater outwards. Other groups have also supported this theory of the cosmological constant aiding in the expansion of the universe. The group High-Z Supernova Search team has observed fourteen supernovae that support the evidence of the cosmological constant. Dr. Brian Schmidt from the Mount Stromlo and Siding Spring Observatory in Australia and his team "concluded with a statistical confidence of between 98.7 and 99.9 percent that cosmic expansion is receiving an antigravity boost, presumably from energy of the cosmological constant" (Wilford, 3). The cosmological constant could make up to 65 percent of the critical density. "Thus closing the gap between known mass and the much-admired model in which the universe is characterized as omega equaling one" (Wilford 3).
In conclusion, we've found that by understanding supernovae we can understand how the Universe expands. By using current technology , we can observe distant supernovae and their remnants, and using this data we are able to get an idea of how fast the Universe is expanding. We also learned about the "cosmological constant" ( the opposite of gravity) and if it is proven will explain why the universe will eternally expand.