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The total amount of energy that a star can generate through nuclear fusion of hydrogen is limited by the amount of hydrogen fuel that can be consumed at the core. For a star in equilibrium, the thermal energy generated at the core must be at least equal to the energy radiated at the surface. Since the luminosity gives the amount of energy radiated per unit time, the total life span can be estimated, to first approximation, as the total energy produced divided by the starās luminosity.46For a star with at least 0.5 Mā, when the hydrogen supply in its core is exhausted and it expands to become a red giant, it can start to fuse helium atoms to form carbon. The energy output of the helium fusion process per unit mass is only about a tenth the energy output of the hydrogen process, and the luminosity of the star increases.47 This results in a much shorter length of time in this stage compared to the main sequence lifetime. (For example, the Sun is predicted to spend 130 million years burning helium, compared to about 12 billion years burning hydrogen.)48 Thus, about 90% of the observed stars above 0.5 Mā will be on the main sequence.49 On average, main-sequence stars are known to follow an empirical mass-luminosity relationship.50 The luminosity (L) of the star is roughly proportional to the total mass (M) as the following power law:
This relationship applies to main-sequence stars in the range 0.1ā50 Mā.51The amount of fuel available for nuclear fusion is proportional to the mass of the star. Thus, the lifetime of a star on the main sequence can be estimated by comparing it to solar evolutionary models. The Sun has been a main-sequence star for about 4.5 billion years and it will become a red giant in 6.5 billion years,52 for a total main sequence lifetime of roughly 1010 years. Hence:53
Humans are very funny. Even thought we know that, doing the same thing over and over again and expecting different results is Insane. We keep doing the same thing over and over again. Example: Daylight Saving Time (DST) .
FreihEitner Premium Member almost 4 years ago
Iāll observe the getting of the popcorn.
Major Matt Mason Premium Member almost 4 years ago
ā¦Donāt forget the runaway llamas.
Bilan almost 4 years ago
Iāll be the first one to say . . .
So much for there being intelligent life out there.
Imagine almost 4 years ago
But if itās just some brainless entertainment youāre looking for, you canāt top this place.
PICTO almost 4 years ago
āThereās one born every minuteā¦ā Barnum was only right by halfā¦
Gent almost 4 years ago
On the internet, nobody knows youāre a cat. Unless you is a lawyer.
The Reader Premium Member almost 4 years ago
Where can we subscribe to Brewster Rockit, Cat Filter Edition?
geese28 almost 4 years ago
Nothing beats a cat video
Michael G. almost 4 years ago
It really happened, and it was hilarious.
PS3T74 almost 4 years ago
The two Observers standing next to each other in Panel #1. The Bat-Man symbol between their collars!
St. Pillsbury almost 4 years ago
The total amount of energy that a star can generate through nuclear fusion of hydrogen is limited by the amount of hydrogen fuel that can be consumed at the core. For a star in equilibrium, the thermal energy generated at the core must be at least equal to the energy radiated at the surface. Since the luminosity gives the amount of energy radiated per unit time, the total life span can be estimated, to first approximation, as the total energy produced divided by the starās luminosity.46For a star with at least 0.5 Mā, when the hydrogen supply in its core is exhausted and it expands to become a red giant, it can start to fuse helium atoms to form carbon. The energy output of the helium fusion process per unit mass is only about a tenth the energy output of the hydrogen process, and the luminosity of the star increases.47 This results in a much shorter length of time in this stage compared to the main sequence lifetime. (For example, the Sun is predicted to spend 130 million years burning helium, compared to about 12 billion years burning hydrogen.)48 Thus, about 90% of the observed stars above 0.5 Mā will be on the main sequence.49 On average, main-sequence stars are known to follow an empirical mass-luminosity relationship.50 The luminosity (L) of the star is roughly proportional to the total mass (M) as the following power law:
This relationship applies to main-sequence stars in the range 0.1ā50 Mā.51The amount of fuel available for nuclear fusion is proportional to the mass of the star. Thus, the lifetime of a star on the main sequence can be estimated by comparing it to solar evolutionary models. The Sun has been a main-sequence star for about 4.5 billion years and it will become a red giant in 6.5 billion years,52 for a total main sequence lifetime of roughly 1010 years. Hence:53
blakerl almost 4 years ago
Humans are very funny. Even thought we know that, doing the same thing over and over again and expecting different results is Insane. We keep doing the same thing over and over again. Example: Daylight Saving Time (DST) .
stamps almost 4 years ago
What if the universe is Godās filter?
drycurt almost 4 years ago
Theyāre overlays, not filters. Iām not woke to this new terminology.
mistercatworks almost 4 years ago
Eventually we will connect to the Outernet, if we can afford the fees.
oakie817 almost 4 years ago
that would be worth it
Doug K almost 4 years ago
not into seeing the big picture.
David Huie Green LikeNobody'sEverSeen almost 4 years ago
Hard to set proper priorities.
WCraft almost 4 years ago
Donāt forget the politician who crossed the aisle and shook hands with the other sideā¦or was that in an alternate universe?