- 3993 - UNIVERSE - beginning with gas clouds. A gas cloud 13 billion light-years away may be the resting place of some of the earliest stars in the universe. Astronomers may have just found the remnants of some of the universe's very first stars.
------------------------ 3993 - UNIVERSE - beginning with gas clouds.
- The chemical signatures of these faraway,
13-plus-billion-year-old objects are remarkably different from those of younger
stars, like our sun. By studying them, scientists hope to shed light on how
stars, galaxies and even basic elements form.
-
- In the earliest days of the universe, only
very simple elements such as hydrogen and helium were available. Of course
“days” were not invented yet. The first
stars ignited from these elements alone.
-
- Over time, their white-hot cores gradually
cooked simple atoms into heavier elements, such as carbon, oxygen, magnesium
and eventually metals. Later generations
of stars formed from clouds of gas containing these heavier atoms, and today
most of the stars scientists observe are rich in metals like iron.
-
- (Our sun is about 98% hydrogen and helium,
but contains trace amounts of heavier elements like iron, neon and carbon.)
-
- Nobody has observed the original
metal-deficient stars directly; most of them probably exploded long ago. But
scientists can still observe some of their dusty remains by setting their
sights billions of light years away.
-
- Using the European Southern Observatory's
“Very Large Telescope” (VLT), astronomers peered into three distant clouds of
star-forming gas. On their own, these clouds wouldn't tell scientists very
much, but incoming light from nearby quasars which are extremely bright
galactic cores formed by dust falling into a supermassive black hole, helping reveal the cloud's secrets.
-
- Based on which wavelengths of light the gas
clouds absorbed, the team determined what elements the stellar remains were
made of. The clouds were extremely poor
in iron and other metallic elements, but rich in carbon, oxygen and
magnesium. This is precisely what would
have been left over after the first stars ran out of fuel and exploded,
according to the researchers.
-
- This tracks with other research into the
origins of stars, and may help explain the composition of younger stars,
including those found in the Milky Way.
When the universe's first stars emerged from the cosmic dark ages, they
ballooned to 10,000 times the mass of Earth's sun, new research suggests.
-
- The
first stars in the cosmos may have topped out at over 10,000 times the mass of
the sun, roughly 1,000 times bigger than the biggest stars alive today. Today the biggest stars are 100 solar masses.
But the early universe was a far more exotic place, filled with mega-giant
stars that lived fast and died very, very young.
- More than 13 billion years ago, not long
after the Big Bang, the universe had no stars. There was nothing more than a
warm soup of neutral gas, almost entirely made up of hydrogen and helium. Over
hundreds of millions of years that neutral gas began to pile up into
increasingly dense balls of matter. This period is known as the “cosmic Dark
Ages”.
-
- In the modern day universe, dense balls of
matter quickly collapse to form stars. That is because the modern universe has
something that the early universe lacked: a lot of elements heavier than
hydrogen and helium. These elements are very efficient at radiating energy
away. This allows the dense clumps to shrink very rapidly, collapsing to high
enough densities to trigger nuclear fusion.
This is the process that powers stars by combining lighter elements into
heavier ones.
-
- The only way to get heavier elements in the
first place is through that same nuclear fusion process. Multiple generations
of stars forming, fusing, and dying enriched the cosmos to its present
state. Without the ability to rapidly
release heat, the first generation of stars had to form under much different,
and much more difficult, conditions.
-
- Astronomers used all the usual cosmological
ingredients: dark matter to help grow galaxies, the evolution and clumping of
neutral gas, and radiation that can cool and sometimes reheat the gas. But
their work includes something that others have lacked: cold fronts, fast-moving
streams of chilled matter, that slam into already formed structures.
-
- They found that a complex web of
interactions preceded the first star formation. Neutral gas began to collect
and clump together. Hydrogen and helium released a little bit of heat, which
allowed clumps of the neutral gas to slowly reach higher densities.
-
- But high-density clumps became very warm,
producing radiation that broke apart the
neutral gas and prevented it from fragmenting into many smaller clumps. That
means stars made from these clumps can become incredibly large.
-
- These back-and-forth interactions between
radiation and neutral gas led to massive pools of neutral gas, the beginnings
of the first galaxies. The gas deep within these proto-galaxies formed rapidly
spinning accretion disks which are fast-flowing rings of matter that form
around massive objects, including black holes in the modern universe.
-
- On the outer edges of the proto-galaxies,
cold fronts of gas rained down. The coldest, most massive fronts penetrated the
proto-galaxies all the way to the accretion disks.These cold fronts slammed
into the disks, rapidly increasing both their mass and density to a critical
threshold, thereby allowing the first stars to appear.
-
- Those first stars weren’t just any normal
fusion factories. They were gigantic clumps of neutral gas igniting their
fusion cores all at once, skipping the stage where they fragment into small
pieces. The resulting stellar mass was huge.
-
- Those first stars would have been incredibly
bright and would have lived extremely short lives, less than a million years.
(Stars in the modern universe can live billions of years). After that, they
would have died in furious bursts of supernova explosions.
-
- Those explosions would have carried the
products of the internal fusion reactions – elements heavier than hydrogen and
helium – that then seeded the next round of star formation. But now
contaminated by heavier elements, the process couldn’t repeat itself, and those
monsters would never again appear on the cosmic scene.
-
May 9, 2023 UNIVERSE - beginning with gas clouds. 3993
----------------------------------------------------------------------------------------
----- Comments appreciated and Pass it on to whomever
is interested. ---
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for
copies or Index of all reviews
--- to:
------
jamesdetrick@comcast.net
------ “Jim Detrick” -----------
--------------------- --- Wednesday, May 10, 2023
---------------------------------
-
No comments:
Post a Comment