WONDERFUL UNIVERSEGalaxies , stars and their origin

More universes than ours ?Earth-like planets ?

C. de Jager

The constellation Andromeda contains the ‘nebula’ M 31

It took 2.5 million years for these photons to reach

our eyes

When the Neanderthalers still lived here these photons had already

finished 95% of their trip

That ‘nebula’ is our neighbouring sister-galaxy: Messier 31

Distance 2.5 million light years With our galaxy it is one of the two

largest of the ‘local group of galaxies’ (which contains some 20 extragalactic systems)

Diameter about 150 000 light years About 1012 stars Total mass ~1.3 times that of our galaxy

Our sister-galaxy

Many more spiral-galaxies in the sky - the whirlpool galaxy, distance 25

Mlj

M83: a barred spiral – like our galaxy; at 15 Mlj

The sombrero galaxy – gas and dust in the equatorial plane at

30 Mlj

Groups of galaxies: the Virgo cluster at 53 Mlj

Part of the Coma cluster; hundreds of galaxies at 320

Mlj

Deep space up to some 12 Glj (Giga

light years) -– more galaxies than stars on this picture

Farthest known galaxy– at 13.1 Glj

That was a rapid view of our Universe

There were remarkable developments in the early 20th century

An essential question for Einstein (1915): Why

does the universe not collapse – the Earth existsed for hundreds of millions of years if not longer; the galaxies most probably too

Did the universe exist that long without collapsing?

To overcome this Einstein introduced an additional term in his formulae – characterized by the Greek capital Lambda. Keeping the universe in shape

Einstein’s dilemma

Ten years after Einstein Hubble found that the

Universe is expanding Around 1920 - 30 that was already predicted

by De Sitter, Friedman and Lemaître Their suggestion: Universe is either expanding

or collapsing or (most improbable) just in balance

Hubble could measure distances and found: it is expanding

Einstein: “Introducing Lambda was my biggest error”

Einstein’s ‘biggest error’

Hubble’s first diagram – 1929(note: one parsec = 3.26 light years)

A special type of supernovae (Supernovae type Ia)

is the most reliable standard candle A supernova Ia is due to the explosion of a white

dwarf star that, by collecting mass from a companion star, exceeds its limiting mass of 1.4 solar masses

Then it produces a radiation flux of 1010 times solar radiation flux. Therefore visible till far in the depths of the Universe

All SN Ia are equally bright – that makes them a good standard candle

Later improvements based on a reliable standard candle

From Hubble diagram we derive: Universe originated

13,8 Gigayears ago; must have been very small at that time – how small?

Lemaître (Leuven) introduced L’atome primitif: the universe started extremely small ; elaborated by Gamov

The hypothesis of an explosion with extremely small origin met with much sceptisism

Hoyle, cynically: “These fantasists with their big bang” Gradually – after more data and many investigations –

the conclusion became inevitable

“The day without yesterday”(Lemaître)

It was not an explosion !

Not an explosion of matter – space originated and grewBefore, there was no space; nor did time exist.

Before? That notion too had no sense

Universe, space and time, originated from an

instability of the absolute vacuum – the Big Bang, but how?

Perhaps the Casimir-Polder hypothesis (1948)? Basis: even the absolute vacuum does contain energy

in volumes as small as the Planck length – emergence and decay of very enegetic virtual particles with positive and negative energy explosions, and even with positive and negative time excursions.

Could an accumulation of energy in the sub-Planck domain lead to an explosion followed by expansion and decreasing temperature? Still very open question

Big Bang

In times shorter that Planck time (1.35 x !0-43sec)

and space smaller than Planck length (4.05 x 10-35 meter) notions time and space lose their meaning. Virtual particle can originate and decay.

Formation involves positive and negative energy of order of Planck energy (2x 109 Joule) and associated pressures

Corresponding temperature is 3.55x 032 K Could such an explosion have given rise to the

Universe? And: why then only one universe ? A multiverse?

The Planck era and the Multiverse

After its formation the universe expanded and cooled Basic constituents of chemcal elememts originated: Quark–gluon liquid after ~ 10-6 s; T = 1013 K Thereafter protons and neutrons formed and then the

simplest atomic nuclei (H, He, Li) After 300 seconds: T has decreased to ~ 109 K,

universe consisted of positive ions of Hydrogen, Deuterium, Helium-3, Helium-4, Lithium and many electrons

After 370 000 years: T smaller than 4000 K; recombination of protons and electrons: universe became transparent

After Planck era: formation of first chemical elements

This was the standard picture

It was accepted till end of last century. Recent new developments

(a) Study of motions in (groups of) galaxies

shows there must exist more matter than what is visible

Initial estimates: there is about five to ten times more invisible than visible matter. What is it?

Dark matter – nice name but explains nothing (b) But additionally it was found that expansion

of universe is accelerating (Einstein’s Lambda returns!)

Enormous energy needed for this acceleration Dark energy – nice name but explains nothing

Dark matter and dark energy

The relation between velocity of expansion

and distance is not linear – the expansion accelerates!

Acceleration by some form of energy. How much?

We tranform energy into mass with E = m.c2

Best agremeent is found for 30% mass (visible and invisible) and 70% mass corresponding with dark energy

See next graph

More about the acceleration

A closer look at the developing universe

After the first few minutes, the Universe, while continuing to cool down, still consisted only of

atoms of Hydrogen and Helium.

By recombination of electrons and protons the first

hydrogen atoms formed. The universe became practically transparent (apart from absorption by He atoms)

This happened after some 370 000 years . At that time T had decreased till below 4000 K – but by exansion of universe we see T = 2.7 K

Do stars and galaxies originate at that time? Can we see that ?

WMAP and Planck satellites, observing at mm wavelengths gave image of the universe at that time

Result was disappointing: practically smooth universe

After 370 000 years

Planck satellite observing at many mm wavelengths

The universe, 370 000 years old; very smooth; most fluctuations ~ 0.2 mK

Power spectrum

Total relative mass of visible matter (baryons and

electrons) is 0.0486 ± 0.0007 Total relative mass of dark matter is 0.273 ± 0.006 Total relative mass correspoding with dark energy

is 0.68 ± 0.02 Expansion velocity increases wit 67.3 ± 1.2

km/sec/megaparsec (Hubble constant); age of univere 13.8 Giga-years

Hence: visible matter: 5%; dark matter: one-fourth; dark energy: two-thirds

Results of analysis

Birth of galaxies, stars and planets

At that time: only Hydrogen-Helium bodiesHeavier atoms did not exist

Hence: no rocky planets possibleLife was neither possible

With the given densities and radiation flux only

fairly small individual clouds of gas can form Mass of order 10 000 solar masses. This happened after 300 to 500 million years Gradually H2 molecules form, a fraction of 0.001 to

0.000 1 produces sufficient cooling allowing for more mass accretion; thus these clouds grew

After about 600 million year the mass has increased to 1 – 10 million solar masses; not yet a galaxy.

We call these objecs: proto-galaxies

Proto-galaxies

Small density fluctuations in the proto-galaxies can

lead to fragmentation followed by further contraction – thus the first stars form

Size is limited by the absorption in the atmospheres – if this is large enough, atmophere expands and escapes. This limits the size of the star

Present most massive stars contain enough absorbing matter to keep their mass below 60 – 80 solar; their radiation flux is one million times the solar value.

In contrary: the earliest stars of the universe could reach masses up to a thousand solar masses

The first stars - gigantic objects

The early H-He stars had high central pressure and

temperature. Intense nuclear radiation and hence intense radiation flux ( ~108 to 109 times solar value)

Hence shortlived star Compare: sun is expected to live for 10 Gigayears; star of

100 solar masses lives only 1 – 3 million years Star of 1000 solar masses is expected to live not longer

than 30.000 years; ; they radiate few 100 million times more intense than the sun

Explosion at end of life – hypernova Remaining core becomes black hole of ~ 100 solar

masses

Short living objects; hypernovae

At the end of the life of a star heavier than ~

10 solar masses it explodes Core remains and becomes neutron star or

black hole This proces is called a supernova. Atomic

nuclei up to Fe, Ni … etc. .. are formed during explosion

The explosion of the initial very large stars of many hundres of solar masses are called hypernovae

During their explosions large numbers of high-mass atomic nuclei are formed and spread over space

Compare super- and hypernovae

An ordinary supernova and its galaxy SN1994D

Remnants of a supernova expand with 5000 – 10.000

km/sec

GammaRay Burst 030329; may 2003 (compare brightness of burst with that of

neighbour galaxy!) Star was 40 solar; new elements up to Ni formed

Gamma ray burst associated with hypernova 16-09-2008

Source distance : 12.2 Gigalightyears

Universe exists for 13.8 Gigayears 0.37 million years: universe becomes

transparent 400 million years: first matter accumulated 600 million years: protogalaxies; first

hypergiant stars, hundreds to thousand times larger than sun

800 million years: first present-days galaxies; smaller stars

After 1 to 2 Gigayears: first sunlike stars

Summarizing (all data are aproximative)

We exist

You and me: We exist thanks to the supergiant stars and to the

super- and hypernovae

Sun-like stars can only exist if they contain enough

absorbing matter, which is atoms heavier than He In cores of massive stars (20 – 80 times sun)

elements such as O, Ne, Mg, Si are formed In ‘ordinary’ supernovae (mass above 10 solar, and

up to ~ 80 solar) chemical elements up to atomic numbers around Fe and Ni are formed during their explosion

In hypernovae (more massive stars) formation of still much massive chemical elements

Thanks to such stars rocky planets and life can exist

We exist thanks to massive stars

Back to earth

Earth-like planets could therefore exist in the universe

But how about life?

First extrasolar planets discovered in 1992 and 1995. Presently some 1800 known and 3000 candidates; various discovery

methods

Limited habitable area

Planets in habitable area star: Gliese 667C

Only big planets can yet be discovered Only those that revolve close to the parent star Thus ‘hot Jupiters’ are frequently found The Earth reflecting only fraction 10 -10 of the

sun’s light, occulting some 10-4 part of the sun and revolving around the sun in a time as long as one year, would be very difficult to discover

But Jupiter too would be a difficult object in spite of its big mass, because of its long revolution time

Limitations to discoveries

A new approach: starlight being eliminated by

interferometry; three planets found

Set of four spacecrafts, pointing same direction Mutual relative distances and distance to fifth

spacecraft to be controlled with extreme precission Light sent from the four to the central spacecraft By interferometry light of star is eliminated; light

of planet(s) remains Residual light inspected spectroscopically –search

for molecules that relate to life

This is a proposal to ESA – not yet accepted

A fascinating proposal: the Darwin mission

Darwin spacecraft cluster

IR spectra of Earth, Venus, Mars: note O2 , H2O , CO2

That was our Universe

Containing at least one small rocky planet, surrounded by a thin layer of water and

much thinner layer of gas. A good Universe to live in

This presentation can be consulted at

website cdejager.com

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