Transcript Cosmology: Black Holes, Dark Matter and Dark Energy

Cosmology and Astrophysics
Metin Arık
19 March 2009
Sci 102 Lecture
Cosmology: Black Holes, Dark Matter and Dark Energy
The three most iportant aspects of modern cosmology
are Black holes, Dark Matter and Dark Energy. I will
review these concepts which are deeply related to the
evolution of the expanding universe. Black holes are
formed after giant stars undergo a super-nova explosion.
Matter falling into a black hole undergoes the most
violent reaction known in the universe. So we regard
black holes as visible objects. On the other hand dark
matter and dark energy form 97% of the present
universe. We cannot see them directly but we can
deduce their existence indirectly from observations.
ZAMAN
milyarxmilyarxmilyarxmilyar saniye
: proton ömrü bundan daha uzun
milyarxmilyarxmilyar saniye
:?
milyarxmilyar saniye
: evrenin yaşı
milyar saniye
: insan ömrü
bir saniye
: şu an
bir saniyenin milyarda biri
: zayıf bozunma ömrü
bir saniyenin milyarda birinin
milyarda biri
: elektromanyetik bozunma ömrü
bir saniyenin milyarda birinin
milyarda birinin milyarda biri
: kuvvetli bozunma ömrü
bir saniyenin milyarda birinin
miyarda birinin milyarda
birinin milyarda biri
:?
bir saniyenin milyarda birinin
milyarda birinin milyarda
birinin milyarda birinin milyarda biri
: Planck zamanı
BLACK HOLES
May 1, 2006
VLBA Reveals Closest Pair of Supermassive Black Holes
Astronomers using the National Science Foundation's Very Long Baseline Array
(VLBA) radio telescope have found the closest pair of supermassive black
holes ever discovered in the Universe -- a duo of monsters that together are
more than 150 million times more massive than the Sun and closer together
than the Earth and the bright star Vega.
"These two giant black holes are only about 24 light-years apart, and that's
more than 100 times closer than any pair found before," said Cristina
Rodriguez, of the University of New Mexico (UNM) and Simon Bolivar
University in Venezuela. Black holes are concentrations of mass with gravity so
strong that not even light can escape them.
The black hole pair is in the center of a galaxy called 0402+379, some 750
million light-years from Earth. Astronomers presume that each of the
supermassive black holes was once at the core of a separate galaxy, then the
two galaxies collided, leaving the black holes orbiting each other. The black
holes orbit each other about once every 150,000 years, the scientists say.
Redshift 5.0 Quasar The arrow in this image points out the record-breaking redshift 5.0
quasar discovered by the Sloan Digital Sky Survey. That faint red dot of light represents
an object that is actually a hundred times as luminous as a typical galaxy. Sky Survey
astronomers identified this object as a possible high-redshift quasar on the basis of its
exceptionally red color compared to ordinary stars and galaxies. Followup spectroscopy
with the ARC 3.5-meter telescope confirmed that this unassuming speck was indeed the
most distant quasar known to date.
SDSS Collaboration
2000 April 19
Redshift 5.8: A New Farthest Quasar
Credit: Stephen Kent (FNAL), SDSS Collaboration
Sloan Digital Sky
Survey at Apache
Point Observatory
The red dot in this
picture is the most
distant quasar ever
discovered (at least
as of October 2003).
The redshift 6.4
quasar is seen at a
time when the
universe was just
800 million years
old. The light-travel
time from this object
to us is about 13
billion years.
UZAY
milyarxmilyarxmilyar metre
: en uzak galaksi
milyarxmilyar metre
: galaksi içi
milyar metre
: güneş sistemi içi
metre
: insan
bir metrenin milyarda biri
: molekül
bir metrenin milyarda birinin
milyarda biri
: proton
bir metrenin milyarda birinin
milyarda birinin milyarda
biri
: elektron ?
bir metrenin milyarda birinin
milyarda birinin milyarda
birinin milyarda biri
: Planck uzunluğu
VLA image (green)
of radio emission
from HCN gas,
superimposed on
Hubble
Space Telescope
image of the
Cloverleaf
galaxy 11 billion
light years away.
The four images of
the Cloverleaf
are the result of
gravitational lensing
10 December 2003
Astronomers Discover Most Distant Galaxy
Showing Key Evidence For Furious Star Formation
GRAVITATIONAL LENSING
Chandra X-ray Observatory images a distant quasar
The X-ray image of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light years from
Earth, shows an enormous X-ray jet that extends at least a million light years from the quasar. The jet is likely due to the collision
of a beam of high-energy electrons with microwave photons.
The high-energy beam is thought to have been produced by explosive activity related to gas swirling around a supermassive black
hole. The length of the jet and the observed bright knots of X-ray emission suggest that the explosive activity is long-lived but
intermittent.
On their way to Earth, the X-rays from the quasar pass through a galaxy located 4 billion light years away. Atoms of various elements
in this galaxy absorb some of the X-rays, and produce a dimming of the quasar's X-rays, or an X-ray shadow. In a similar way, when
our body is X-rayed, our bones produce an X-ray shadow. By measuring the amount of absorption astronomers were able to
estimate that 4 billion years ago, the gas in the absorbing galaxy contained a much lower concentration of oxygen relative to
hydrogen gas than does our galaxy - about five times lower. These observations will give astronomers insight into how the oxygen
supply of galaxies is built up over the eons.
KOZMOLOJİ: evrenin evrimi
Gözlem: evren genişliyor. Evren sonluysa ve zamanda geri gidersek bir “nokta”
dan başlamış olmalı, buna büyük patlama diyoruz. Büyük patlama yaklaşık 14
milyar yıl önce olmalı.
Evren başta çok sıcak olmalı, madde yerine radyasyon dolu olmalı. Einstein
denklemleri bize böyle bir evrenin gittikçe yavaşlayan bir hızda genişlediğini
gösteriyor.
Evren yeteri kadar genişleyip soğuduğunda atomlar (madde) oluşuyor. Fotonlar
halinde kalan radyasyon soğuyarak bugüne kadar kalıyor ve günümüzde ölçülebiliyor.
Einstein denklemleri madde dolu bir evrenin de gittikçe yavaşlayan bir hızda genişleyeceğini
ve evren sonlu ise bir zaman sonra daralmaya başlayacağını söylüyor.
Böyle bir evrenin niye bugün gözlemlediğimiz kadar büyük olabildiğini açıklamakta
zorlanıyoruz.
Başlangıçta evrenin eksponansiyel artan hızla genişlemiş olduğu bir süreç olmalı,
bu sürece “enflasyon” diyoruz.
Yakındaki galaksileri gözlemleyerek evrenin bugünkü genişleme hızını, uzaktaki
galaksilere bakarak evrenin geçmişteki genişleme hızını ölçebiliyoruz.
Son ölçümler gösteriyor ki evren şu anda da artan bir hızla genişliyor, ama 5 milyar
yıl önce madde dolu bir evren gibi gittikçe yavaşlayan bir hızda genişliyordu.