Upload
melissa-choi
View
219
Download
0
Embed Size (px)
Citation preview
8/10/2019 A Brief Summary of Einstein's Work
1/3
EINSTEINALL THE TIME
More than a century has passed since Albert Einsteins miraculous year in whichhe published three papers, all within a few months, describing ideas that have since
inuence a of moern physics. The rst paper caime that ight must sometimes
behave ike a stream of partices with iscrete energies, quanta. The secon paper
offere an experimenta test for the theory of heat. The thir paper aresse a
central puzzle for physicists of the daythe connection between electromagnetic
theory an orinary motionan sove it using the principe of reativity.
Einsteins ngerprints can be foun on virtuay every scientic resut obtaine with
Chanra X-ray Observatory ata. These resuts in turn have expane our concept ofthe Universe far beyon what was imagine at the beginning of the 20th century. Three
of Einsteins discoveriesthe photoelectric effect, the theory of special relativity, and
the theory of general relativity (published in 1915)are described here, with examples
of how his work is use extensivey by X-ray astronomers.
NASAs CHANDRA X-RAY OBSERVATOHTTP://CHANDRA.HARVARD.EDU
8/10/2019 A Brief Summary of Einstein's Work
2/3
INSTEIN ALL THE TIME
TOELECTRIC EFFECT
well known that Einsteins work on relativity
formed the landscape of physics, but it is not generally
eciated that he received the Nobel prize fo r his work
e photoeectric effect. His prizewinning work showe
the emission of electrons from a substance when high-
gy light strikes it can be explained if light is composed
otons that behave ike partices.
The operation of Chanra an the interpretation of the ata gathere
by Chandra would be impossible without an understanding of the
photoeectric effect. Chanras two X-ray etectors make use of the
ejection of eectrons from atoms by X-rays via the photoeectric effect.
This process is aso responsibe for the absorption of X-rays by the
Earths atmosphere, which is why Chandra has to be in space in the first
pace.
The roe of the photo eectric effect in X-ray astronomy is crucia. Amost
every spectrum of an X-ray source that Chandra makes shows evi dence
of the photoelectric absorption of X-rays either by atoms in interstellar
space between the source and Chandra, or by atoms and ions clumped
around a cosmic source, such as a cloud of cool gas around a young
star, or an accreting back hoe. This effect aows astrophysicists to
determine the amount and composition of cool gas and dust in space,
an to trace the motion of iron atoms orbiting very near back hoes.
CIAL RELATIVITY
ng other things, the theory of special relativity
es that: time passes at different rates for reference
es in relative motion; that radiation from electrons
ng at near the speed of light is highly beamed and
ted in energy; and that matter-antimatter pairs of
rons can be create from very high-energy photons.
e effects are neee to interpret the ight observe from pusars, gamma ray bursts, an from X-ray
hat o rigina te near supermassive b ack hoes an exte n over hunre s of thous ans o f igh t years .
GENERAL RELATIVITY
The theory of genera reativity impies that mass curves space which
in turn impies the existence of back hoes.
Many of the powerful X-ray sources observed by Chandra are thought
to be due to X-radiation from gas that is heated to millions of degrees
as it swirs towar back hoes. The th eory of genera reativity is use
together with X-ray observations to determine how much gas is falling
into these back hoes, an to set imits on their masses.
A careful study of the X-rays from gas falling toward black holes may
utimatey test the preictions of genera reativity. Areay, Chanra
observations have provided evidence for the dragging of space around
back hoes, an for the existence of event horizons.
Another consequence of the bending of space by matter is the bending of light, which cause
gaaxies an gaaxy custers to act ike gravitationa enses. This phenomenon has enabe
using Chandra to study distant quasars, and, through comparison with optical observations, to
conitions in gas cous aroun back hoes with unpreceente accuracy.
Finay, genera reativity is the fu namenta theory neee to unerstan the evoution of the
Chandra observations of distant clusters of galaxies enable astronomers to inventory the amou
matter an ark energy, the two ominant components of mass an energy in the Universe.
MIRRORS OF X-RAY TELESCOPES
X-ray telescopes in orbit above the Earths atmosphere can
coect X-rays from energetic sources biions of ight years away.
These cosmic X-rays are focuse by barre shape mirrors onto an
instrument especially designed to measure properties such as theincoming irection an energy of the X-ray photon. A gaseous or
solid material in the instrument absorbs the X-rays by the photo-
eectric effect.
The buiing an operation of an X-ray observatory is a marve of
moern technoogy an ingenuity. Because the Earths atmosphere
absorbs X-rays, X-ray observatories must be placed high above
the Earths surface. This means that the utra-precise mirrors an
detectors, together with the sophisticated electronics that conveys
the information back to Earth must be able to withstand the rigors of
a rocket aunch, an operate in the hostie environment of space.
4 NestedParaboloids4 Nested
HyperbooisDoubly
ReecteX-rays
FocalSurface
8/10/2019 A Brief Summary of Einstein's Work
3/3
EINSTEIN & CHANDRA: CHANDX-RAY CENASTROPHYSICS OF THE HIGH-ENERGY UNIVERSE
A NEW BRANCH OF SCIENCE Within a ecae after Einsteins eath in 1955, the e of X-ray astrophy
was born. With the beginning of the Space Age, an humanitys abiity to sen instruments above the Ear
atmosphere, the Universe was opened for the study of high-energy phenomena and therefore for testing m
of Einsteins preictions. Toay, NASAs agship mission of X-ray astronomy is the Chanra X-ray Observato
name for another eaing physicist of the 20th century an coeague of Einstein, Subrahmanyan Chanrasek
Using Chanra, scientists are now abe to probe many of the ieas rst introuce by Einstein in the miracu
year a century earier.
MKN 421 The photoeectric effect can probe the Universe, as shown by
tronomers stuying X-rays of istant objects. With a quasar acting as a i
house in a fog, scientists discovered two huge intergalactic clouds of diff
hot gas that possiby constitute a arge chunk of materia in the Unive
X-rays from Chanra show the cous of hot gas are tering out, or absorb
X-rays from a istant quasar known as Markarian 421 (see p.2). These co
are the best evidence yet that a vast cosmic web of hot gas contains the lo
sought missing matterabout haf of the atoms an ions in the Universe.
M87 Chandra observed an enormous jet blasting out the core of the g
eiptica gaaxy known as M87. Not ony impressive because it stretches
thousands of light years, this jet also represents an important testing gro
of Einsteins Specia Reativity theory. Astronomers must take the reat
tic effects into account when studying the high-energy environment aro
back hoes, ike the one foun at the center of M87 that prouces this je
CLOVERLEAF QUASAR (A.K.A. H1413+117) One of the most dramatic
examples in the cosmos of Einsteins theories is the so-called gravita-iona ens. When X-rays an other forms of ight from a istant source
pass by a arge intervening mass, the ight is bent. This bening can
prouce mutipe images of that istant source. In the case of the Co-
verleaf Quasar, Chandra detects what appears to be a cloverleaf-like
pattern of sources. But, in fact, the gravitationa e from some fore-
groun objectikey one or more gaaxieshas bent an magnie
he ight from this singe quasar to prouce mutipe images.
CHANdRA
GALAXY
MICROLENSINGSTAR
VIEW FROM CHANdRA
D
SOUR
ABELL 2029, MS2137.3-2353, AND MS1137.5+6624 Einsteins
heories continue to provide the framework for understand-ng the evolution of the Universeincluding the mysterious
dark matter and dark energy that astronomers now believe
o be its ominate components. Using Chanra, scientists can
attempt to better understand dark matter and dark energy
by stuying custers of gaaxies. For instance, researchers
used 26 Chandra imagesthree of which are shown hereto
conrm that the expansion of the Universe is sowing own
ue to the effects of ark energy.
ABEll 2029 MS2137 MS1137
Smithsonian Harvard-Smithsonian Center for Astrophysics For more information,Astrophysical Observatory 60 Garden Street, Cambridge, MA 02138 http://chandra.harvar