Residents of that future galaxy would have a much darker universe to observe, Livio said. They would probably not be able to tell there was a Big Bang. As the early universe inflated, there are some theories that say that different "pockets" broke away and formed different universes. These different places could be expanding at different rates, include other types of matter, and have different physical laws than our own universe.
Livio pointed out there could be galaxies in these other universes — if they exist — but we have no way right now of knowing for sure. So the number of galaxies could even be greater than billion, when considering other universes. In our own cosmos, Livio said, astronomers will be better able to refine the number upon the launch of the James Webb Space Telescope for which his institute will manage the mission operations and science.
Hubble is able to peer back at galaxies that formed about million years after the Big Bang. After James Webb launches in , astronomers anticipate they can look as far back as million years after the Big Bang. While it is interesting to count the number of galaxies in our universe, astronomers are more interested in how galaxies reveal how the universe was formed.
According to NASA, galaxies are a representation of how matter in the universe was organized — at least, on the large scale. Scientists are also interested in particle types and quantum mechanics, on the small side of the spectrum.
Because Webb can look back to the early days of the universe, its information will help scientists better understand the structures of the galaxies around us today. Webb will also allow scientists to gather data on the types of stars that existed in these very early galaxies," NASA said of Webb's mission. These studies will also reveal details about merging galaxies and shed light on the process of galaxy formation itself.
Scientists are also interested in the role that dark matter plays in the assembly of galaxies. While some of the universe is visible in forms such as galaxies or stars, dark matter is what makes up most of the universe — about 80 percent of it. While dark matter is invisible in wavelengths of light or through emissions of energy, studies of galaxies dating back to the s indicated there was far more mass present in them than what was visible with the naked eye. The visible matter we see collects inside this scaffolding in the form of stars and galaxies.
Added to existing Hubble observations, their results suggested such galaxies make up 90 percent of the total, leading to a new estimate—that there may be up to two trillion galaxies in the universe. Such estimates, however, are a moving target. As more observations roll in, scientists can get a better handle on the variables at play and increase the accuracy of their estimates.
In a study presented this week at the American Astronomical Society and soon to be published in The Astrophysical Journal , a team led by astronomers Marc Postman and Tod Lauer described what they found after training the New Horizons telescope on seven slivers of empty space to try and measure the level of ambient light in the universe.
Their findings, they say, allowed them to establish an upper limit on the number of galaxies in existence and indicate space may be a little less crowded than previously thought. According to their data, the total number of galaxies is more likely in the hundreds of billions, not trillions.
The New Horizons spacecraft has now escaped the domain of zodiacal light and is gazing at the darkest sky yet imaged. This offers the opportunity to measure the background light from beyond our galaxy and compare it to known and expected sources. Still, the measurement was not straightforward.
Scientists recently took a deep dive into some unusual sightings out in the solar system, and their findings have to do with everything from the actual number of galaxies in the universe to the types of stars around us. Back in April , NASA first detected a huge flare from its satellites that passed by Mars, and while this intergalactic sighting lasted for a mere milliseconds, a research team in University of Johannesburg now knows that this was a burst from a magnetar, which is a powerful neutron star with a magnetic field.
It originated in a galaxy Soebur Razzaque, a professor from the University of Johannesburg, noted that this sighting isn't too unlikely since there are tens of thousands of neutron stars in the Milky Way, but there are still just 30 that have been uncovered as magnetars.
But so far, we know of only a handful of magnetars that produced giant flares. The brightest we could detect was in With this simple calculation you get something like 10 22 to 10 24 stars in the Universe. This is only a rough number, as obviously not all galaxies are the same, just like on a beach the depth of sand will not be the same in different places. No one would try to count stars individually, instead we measure integrated quantities like the number and luminosity of galaxies.
ESA's infrared space observatory Herschel has made an important contribution by 'counting' galaxies in the infrared, and measuring their luminosity in this range — something never before attempted.
Knowing how fast stars form can bring more certainty to calculations. Herschel has also charted the formation rate of stars throughout cosmic history. If you can estimate the rate at which stars have formed, you will be able to estimate how many stars there are in the Universe today. In , an image from the Hubble Space Telescope HST suggested that star formation had reached a peak at roughly seven thousand million years ago.
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