Looking up at the night sky, you might wonder how many stars are in the universe. It is challenging enough for an amateur astronomer to count numbers with the naked eye stars visible and, with larger telescopes, more stars are visible, making counting a lengthy process. So how to do Astronomers find out how many stars in The universe?
The first part is trying to define what “universe” means, said David Kornreich, an assistant professor at Ithaca University in New York state. He is the founder of the “Ask an Astronomer” service at Cornell University.
“I do not know [the answer] because I don’t know if the universe has so big or not,” he said. The observable universe seems to go back in time about 13.8 billion years, but beyond what we can see, there could be much more. Some astronomers also think we could live in a “multiverse“where there will be other universes like ours contained within some sort of larger entity.
The simplest answer might be to estimate the number of stars in a Galaxyand then multiply it by the estimated value number of galaxies in the universe, according to European Space Agency (ESA). But even that is difficult, because some galaxies shine better in the visible region or some in the infrared, for example. There are also estimation hurdles to overcome.
In October 2016, deep-field images from the Hubble Space Telescope showed that there are about 2 trillion galaxies in the observable universe, or about 10 times more than suggested. previously, according to the magazine nature. In an email with Live Science, lead author Christopher Conselice, professor of astrophysics at the University of Nottingham in the United Kingdom, said there are approximately 100 million stars in the average galaxy.
Telescope However, it may not be possible to view all the stars in a galaxy. A 2008 estimate by Sloan Digital Sky Survey (lists all observable objects in a third of the sky) found about 48 million stars, almost half what astronomers expected. A star like our sun might not even appear in such a catalog. So many astronomers estimate the number of stars in a galaxy based on its mass – this has its own difficulties, since dark matter and the galactic rotation must be filtered out before estimation.
Quests such as Gaia’s Quest, a European Space Agency space probe launched in 2013, may provide more answers. Gaia aims to accurately map about 1 billion stars in Galaxy. It builds on the previous Hipparchus mission, which accurately located 100,000 stars, and also mapped 1 million stars with less accuracy. Data from the mission will be released in June 2022, according to ESA.
“Gaia will track each of its 1 billion target stars 70 times over a five-year period, accurately charting their positions, distances, motions and changes in luminosity.” ESA said on its website. “Taken together, these measurements will build an unprecedented picture of the structure and evolution of our galaxy. Thanks to missions like these, we’re one step closer to giving our galaxy a new look.” more reliable estimate for the frequently asked question: ‘How many stars are there in the universe?'”
The observable universe
Even if we narrow down the definition of the “observable” universe – what we can see – estimating the number of stars within it requires knowing how large the universe is. The first is that the universe itself is expanding, and the second is no time can be curved.
For a simple example, light from objects farthest from us would take about 13.8 billion light years to reach. The earth, which takes into account that the youngest objects would be obscured because light could not be carried in the early universe. So the radius of the observable universe must be 13.8 billion light years because light has only that much time to reach us.
Or should it? “It’s a reasonable way to define distance, but not how a relativist defines distance,” says Kornreich. A relativist would use a device such as a measuring stick, measure the distance along the device and then extend it as needed.
This produces another answer, which some sources define as a radius of 48 billion light-years. However, sources differ on this figure. That’s because space-time can be curved. When the observer makes a measurement with the probe, the light travels simultaneously and affects the measurement.
It’s easier to count stars when they’re inside galaxies, because that’s where they tend to be clusterfollow Harvard and Smithsonian Center for Astrophysics. To start estimating the number of stars, you need to estimate the number of galaxies and come up with some kind of average.
Some estimates consider the Milky Way’s stellar mass to be as high as 100 billion”.solar mass“or 100 billion times the mass of Sun. Average the types of stars in our galaxy, this will give the answer about 100 billion stars in the galaxy. However, this can change, depending on the number of stars larger and smaller than our sun. In addition, other estimates say that the Milky Way may have 200 billion or more stars.
The number of galaxies is a staggering number, however, as demonstrated by several imaging experiments conducted by Hubble Space Telescope. Several times over the years, the telescope has pointed a detector at a small spot in the sky to count galaxies, doing the job again after the telescope was upgraded by astronauts in the process. shuttle era.
A 1995 exposure of a small spot in Ursa Major revealed about 3,000 faint galaxies. In 2003-4, using upgraded tools, scientists looked at a smaller point in the Constellation Fornax and found 10,000 galaxies. An even more detailed investigation in Fornax in 2012, with even better instruments, revealed about 5,500 galaxies.
Kornreich used a very rough estimate of the 10 trillion galaxies in the universe. Multiplying it by the Milky Way’s estimated 100 billion stars will produce a really big number: 1,000,000,000,000,000,000,000,000,000,000 stars, or the number “1” with 24 zeros after it (1 one-third in the American numbering system; one-quarter in the European system). That number is likely an underestimate, Kornreich stressed, as more detailed views of the universe would reveal more galaxies.
“The universe has ten times more galaxies than researchers think.” Nature (2016). https://www.nature.com/articles/nature.2016.20809.pdf?origin=ppub
“Sloan Digital Sky Survey reveals a neighbor of the New Milky Way”. SDSS (2006). https://classic.sdss.org/news/releases/20060109.virgooverdensity.html
“Star Cluster”. Harvard and Smithsonian Center for Astrophysics. https://pweb.cfa.harvard.edu/research/topic/star-clusters
“Oases in the Dark: Galaxies as Probes of the Universe”. Utah State University (2007). https://digitalcommons.usu.edu
https://www.space.com/26078-how-many-stars-are-there.html How many stars are there in the universe?