how amny stars are there in the universe?

Answer 1

First of all the observable universe is not infinite but is calculated as having a diameter of 156 billion light years. There may or may not be anything beyond what we can observe, but by definition, we will never know that, will we? It may be finlte or it may be infinite, but we will never know that, either. We have no way of telling.

Astronomers from the Australian National University have come up with a best guestimate of 70 sextillion (7 x 10^22) stars in the observable universe. They did this by studying star densities in sample spaces and then working out how many such spaces there are in the observable universe.

Here is an edited version of one article reporting this:

"70 sextillion stars in the 'known' universe!

According to a study by Australian astronomers there are 70 sextillion (70,000,000,000,000,000,000,000) stars in the known universe.

It's also about 10 times as many stars as grains of sand on all the world's beaches and deserts.

The figure was calculated by a team of stargazers based at the Australian National University.

Speaking at the General Assembly of the International Astronomical Union meeting in Sydney, Dr Simon Driver said the number was drawn up based on a survey of one strip of sky, rather than trying to count every individual star.

The team used two of the world's most powerful telescopes, one at the Anglo-Australian Observatory in northern New South Wales state and one in the Canary Islands, to carry out their survey.

Within the strip of sky some 10,000 galaxies were pinpointed and detailed measurements of their brightness taken to calculate how many stars they contained.

That number was then multiplied by the number of similar sized strips needed to cover the entire sky, Driver said, and then multiplied again out to the edge of the visible universe.

He said there were likely many million more stars in the universe but the 70 sextillion figure was the number visible within range of modern telescopes."

Answer 2

Estimated 400 billion in our galaxy, Harder to estimate the number of galaxies with similar accuracy and there is the problem that some are dwarf galaxies of which there are several such in the Local Group of 30 galaxies, in which the Milky Way is second in size only to the Andromeda Galaxy, So to say the number of stars in the Local Group is 30 x 400 billion would be a serious overestimation, the average number of stars per galaxy may well be less than 100 billion.

So cautious realism suggests a figure of 50 billion average per galaxy and if there are indeed 10^11 galaxies that would mean total number of stars = 5 x 10^21

Only guesswork to get ir right to an order of magnitude!

Answer 3

Well it is less than 10^78 which is the number of atoms in the universe and more than 4 x 10^11 (400 billion) which is the number of stars in the Milky Way Galaxy, On the presumption that stars are of a similar range of sizes throughout the universe, I think we are talking about somewhere in the range of 10^20 to 10*25 stars in all

Answer 4

70 sextillion, I can live with that.

But the answerer who asserts "153. It says so in the Bible" must find it harder to live with himself and that idea, The evidence of his own eyes flatly contradicts this idea, provided he views away from city lights and when there is no moon in the sky.

What are those other points of light, then from no 154 onwards? Optical illusions? Unlikely! God putting up the Fairy Lights at Christmas for Jesus' Birthday? I think not! Loads of new asteroids in the Solar System? They wouldn't be that bright (only 4 Vesta is visible) and they would visibly move over a period of weeks and months!

There are more than six hundred stars in the Pleiades Cluster alone!

Answer 5

If brown dwarf stars are quite common and if what starts out as a planet about the mass of ten Jupiters can evolve into a brown dwarf star (as it acquires more mass in sweeping its neighbourhood of debris) and can then start deuterium fusion in its core, the number of stars may be larger than at first thought, as there could feasibly be two or three such large Jupiters around any star that has gas giant planets.

Answer 6

Stars are being "born" and "die" all the time so it is not a static number. They disappear into a black hole, for example. Is the birth rate equal to or greater than the mortality rate, does anyone know?

Because if it is less than the mortality rate then the universe will one day (say in 10 billion years time, when all existing stars will presumably have died) resemble a car scrapyard, with little or no recycling of parts!

Answer 7

The ones we can see with the naked eye (about 4,000-6,000 depending on light pollution in the viewing conditions chosen) are only a tiny tiny percent of the billions that can be seen with ever more powerful telescopes, Especially when those telescopes are in space like the Soitzer and Hubble space telescopes are, thus avoiding all the problems which the earth's atmosphere creates such as clouds,

Answer 8

It's estimated that there are of the order 100 billion stars in our galaxy; there are also estimated to be well over 100 billion galaxies. To keep the numbers simple then, you could say that there are perhaps 1,000 billion billion stars.

And if each star has one chance in a million of having an earth-like planet, and each earth-like planet has a one in a million chance of having a human-like species, and one in a million human-like species invents long-distance space travel, how many visits from our relations can we expect this Christmas?

Answer 9

How many have ended their days as Black holes? And how many stars not yet at the end of their days have supermassive black holes at the centre of galaxies swallowed up?

Might the "casualty rate" be as high as 10%? And will that percentage increase over time, as the universe gets older?

Answer 10

I will go with seventy sextillion, They investigated a strip of sky thoroughly and then multiplied up on the assumption that all such sectors were similarly dense with galaxies, Seems as good a method as any.