How dark is the sky and what does that tell us about the number of galaxies that are out there? The universe is less crowded than we thought, according to scientists, a finding that has implications for what is known about its makeup. A team led by Texas A&M University says the answer is 100 billion billion times less dense than what appears in the Hubble Space Telescope's view of the universe.
The team discovered the lower density of the universe when it was possible to bring Hubble into closer campaign view mode, so it could look at galaxies merging into larger ones. "Hubble was able to see gas orbiting galaxies," said Sean Carey, the associate director of the Center for Astrophysics at the University of Texas, and the lead author of a new paper appearing today in a special issue of the Monthly Notices of the Royal Astronomical Society.
The observatory can image in 3-D but cannot see across space so the team had to devise a special way to get around that. Optimizing seasonal effects they created a case to see all around the galaxy and determined the dark spots were ultimately caused by various clouds of gas that have successfully clumped over billions of years. These false spots, present in the center of the galaxy NGC 4535, are much too massive to be clouds of gas and contain burnt-out stars.
"All of this makes sense in terms of highly/highly evolved stars," Carey said, "and it makes sense from a dynamical point of view from the point of view of agglomerating galactic-mass clouds."
Such clouds of matter are clumped together to form what is known as an galaxies, which themselves have collective properties because they have mass, heated by the very large amounts of hot, dense, and charged gas within them. Masses of matter can grow and shrink as necessary to have enough motion to be seen over long timescales. More gas pushes stars closer to the center as the sun—a process known as gravitational collapse—activates suns more quickly in these globular clusters, but also blows down gas and generally results in fewer stars.
Astronomers think these multiple factors—exploding stars and a dense globular cluster clouds—were active during the standard period of the universe. Essentially back to the beginning of time, when the universe was younger, much of the mass was very dense. "We believe well over a ten percent of the mass of galaxies could be at the center," Patrick Kelleher, the study's lead author, told i09. "The gas that can grow is out there, and it's barely detectable because it is filled with highly evolved, extremely bright stars." Nonetheless, this slow process of Adding Info The Galaxies Around the Supermassive
The team discovered the lower density of the universe when it was possible to bring Hubble into closer campaign view mode, so it could look at galaxies merging into larger ones. "Hubble was able to see gas orbiting galaxies," said Sean Carey, the associate director of the Center for Astrophysics at the University of Texas, and the lead author of a new paper appearing today in a special issue of the Monthly Notices of the Royal Astronomical Society.
The observatory can image in 3-D but cannot see across space so the team had to devise a special way to get around that. Optimizing seasonal effects they created a case to see all around the galaxy and determined the dark spots were ultimately caused by various clouds of gas that have successfully clumped over billions of years. These false spots, present in the center of the galaxy NGC 4535, are much too massive to be clouds of gas and contain burnt-out stars.
"All of this makes sense in terms of highly/highly evolved stars," Carey said, "and it makes sense from a dynamical point of view from the point of view of agglomerating galactic-mass clouds."
Such clouds of matter are clumped together to form what is known as an galaxies, which themselves have collective properties because they have mass, heated by the very large amounts of hot, dense, and charged gas within them. Masses of matter can grow and shrink as necessary to have enough motion to be seen over long timescales. More gas pushes stars closer to the center as the sun—a process known as gravitational collapse—activates suns more quickly in these globular clusters, but also blows down gas and generally results in fewer stars.
Astronomers think these multiple factors—exploding stars and a dense globular cluster clouds—were active during the standard period of the universe. Essentially back to the beginning of time, when the universe was younger, much of the mass was very dense. "We believe well over a ten percent of the mass of galaxies could be at the center," Patrick Kelleher, the study's lead author, told i09. "The gas that can grow is out there, and it's barely detectable because it is filled with highly evolved, extremely bright stars." Nonetheless, this slow process of Adding Info The Galaxies Around the Supermassive
g
