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8/10/2019 A Brief Summary of Einstein's Work

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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


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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

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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