Astronomers calculate the total amount of starlight ever produced in the observable universe

The universe has been making stars for a good 13 billion years or so, and a natural question to ask might be “how many stars have existed in that time?” But now astronomers have taken it several steps further and asked “how much light has been emitted in that time?” Using a new measurement method, the team has apparently managed to quantify all the starlight every produced in the observable universe – and the result is a figure that’ll make your eyes water.

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Tau.Neutrino said:

Astronomers calculate the total amount of starlight ever produced in the observable universe

The universe has been making stars for a good 13 billion years or so, and a natural question to ask might be “how many stars have existed in that time?” But now astronomers have taken it several steps further and asked “how much light has been emitted in that time?” Using a new measurement method, the team has apparently managed to quantify all the starlight every produced in the observable universe – and the result is a figure that’ll make your eyes water.

more…

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

mollwollfumble said:

Tau.Neutrino said:

Astronomers calculate the total amount of starlight ever produced in the observable universe

The universe has been making stars for a good 13 billion years or so, and a natural question to ask might be “how many stars have existed in that time?” But now astronomers have taken it several steps further and asked “how much light has been emitted in that time?” Using a new measurement method, the team has apparently managed to quantify all the starlight every produced in the observable universe – and the result is a figure that’ll make your eyes water.

more…

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

What sets the limits?

The Rev Dodgson said:

mollwollfumble said:

Tau.Neutrino said:

Astronomers calculate the total amount of starlight ever produced in the observable universe

The universe has been making stars for a good 13 billion years or so, and a natural question to ask might be “how many stars have existed in that time?” But now astronomers have taken it several steps further and asked “how much light has been emitted in that time?” Using a new measurement method, the team has apparently managed to quantify all the starlight every produced in the observable universe – and the result is a figure that’ll make your eyes water.

more…

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

What sets the limits?

Singularity?

The way the singularity came into being ?

The far reaches of the expanding universe?

Tau.Neutrino said:

The Rev Dodgson said:

mollwollfumble said:

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

What sets the limits?

Singularity?

The way the singularity came into being ?

The far reaches of the expanding universe?

The way matter and antimatter annihilated each other?

The Rev Dodgson said:

mollwollfumble said:

Tau.Neutrino said:

Astronomers calculate the total amount of starlight ever produced in the observable universe

The universe has been making stars for a good 13 billion years or so, and a natural question to ask might be “how many stars have existed in that time?” But now astronomers have taken it several steps further and asked “how much light has been emitted in that time?” Using a new measurement method, the team has apparently managed to quantify all the starlight every produced in the observable universe – and the result is a figure that’ll make your eyes water.

more…

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

What sets the limits?

The limits as in 10^84, 10^46 or 10^100?

I said 10^46 because that’s less than the number of atoms on Earth.

10^100 because that’s larger than anything, anything at all, in the past universe. To get up to 10^100 you have to look at things like the time it takes a galactic black hole to evaporate.

The number of atoms in the visible universe is quoted on the internet as between 10^78 and 10^82 but that’s ridiculous, because it has to be known far more accurately than that. You couldn’t run a cosmology calculation that could be in error by up to a factor of 10,000. It would give a wildly inaccurate age of the universe for starters.

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

> Let’s get this number out of the way first. According to the team’s measurements, the amount of photons emitted by stars in the past 13 billion years is expressed as 4 × 10^84. In English, that’s a 4 followed by 84 zeroes. That’s 4 septenvigintillion, for those of you playing at home.

Yeah. That looks about right. I knew it would be a lot larger than 10^46 and a lot smaller than 10^100.

The number of neutrinos emitted in the same period would be very close to that.

What sets the limits?

The limits as in 10^84, 10^46 or 10^100?

I said 10^46 because that’s less than the number of atoms on Earth.

10^100 because that’s larger than anything, anything at all, in the past universe. To get up to 10^100 you have to look at things like the time it takes a galactic black hole to evaporate.

The number of atoms in the visible universe is quoted on the internet as between 10^78 and 10^82 but that’s ridiculous, because it has to be known far more accurately than that. You couldn’t run a cosmology calculation that could be in error by up to a factor of 10,000. It would give a wildly inaccurate age of the universe for starters.

Let’s see if I can get it more accurate. The baryon density of the universe is 0.02230 * 1.87847 * 10^-26 kg/m^3. Convert that to atoms using the ratio of hydrogen to helium (a minor correction). Multiply it by the number of atoms per kg (Avagadro’s number 6.02214 * 10^26) and by the volume of the visible universe (radius from speed of light times 13.80 * 10^9 years). To get an answer correct to almost 3 significant figures.