Interstellar Message

 

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The Following is a Simulation Only!

On Monday, March 26th, 2007 at 6:24:28 a.m. Universal Time the first page of a seven-page interstellar message was received by radio telescopes on the earth.  Scientists have concluded that the radio message could only be the work of an extraterrestrial intelligence.  The radio message came from the star 47 Ursae Majoris in the constellation Ursa Major (i.e., the Big Dipper).  There are two known planets orbiting the star 47 Ursae Majoris.  One A.U. (astronomical unit) is the average distance of the earth from the sun (i.e., 149.6 million kilometers = 93 million miles).  The following table contains a description of the star itself:

47 Ursae Majoris

Parameter

Value

Constellation Ursa Major (i.e., Big Dipper)
Type single star system
Distance from Earth 45.9 light-years
Right Ascension 10h 59m 28.0s
Declination +40deg 25' 49"
Apparent Magnitude +5.03
Spectral Type G1V (yellow dwarf)
Mass 1.03 solar masses
Radius 1.26 solar radii
Luminosity 1.54 suns
Surface Temperature 5,740 deg Kelvin
Rotation Period ~21 days
Metallicity 110% of sun's iron content
Age ~6 billion years
Habitable Zone (Surface temperature of planet is 0 - 50 deg Celsius) 0.96 to 1.40 A.U.

 

The following table contains a description of the known planets of the star:

Planets of 47 Ursae Majoris

Planet

Parameter

Value

b Mass > 2.6 Jupiter masses
b Orbital Period 3.0 years
b Semi-major Axis 2.1 A.U.
b Orbital Eccentricity 0.06
b Year of Discovery 1996
c Mass > 0.79 Jupiter masses
c Orbital Period 7.1 years
c Semi-major Axis 3.8 A.U.
c Orbital Eccentricity 0.0
c Year of Discovery 2002

 

The following table contains a basic description of the radio signal.  A jansky is a unit which measures the power flux received at the receiver per unit of bandwidth.  One jansky equals 1.0E-26 watts per square meter per hertz.

Radio Signal

Parameter

Value

Carrier Frequency 1420.4058 MHz (i.e., galactic emission frequency of neutral hydrogen)
Carrier Wavelength 21.106 cm
Modulation Type Frequency Modulation (FM)
Signal Bandwidth 592.9 Hz
Signal Strength at Earth 5.0 janskies during a pulse, 0.0 janskies in between pulses

If we assume that the radio transmitter is a parabolic dish with a diameter of 100 meters then a received signal strength of 5.0 janskies translates into a power of 31.7 megawatts emitted by the transmitter.  The following table gives some signal strengths of various natural radio sources in the sky at a frequency of 1420 MHz:

Natural Radio Sources

Object

Description

Signal Strength

Cassiopeia A brightest radio source in the sky 2,240 janskies
Sagittarius A supermassive blackhole at center of Milky Way galaxy 1,300 janskies
Cygnus A brightest extragalactic radio source in the sky 1,260 janskies
Crab Nebula (M1) supernova remnant 926 janskies
Eta Carinae variable star 650 janskies
Orion Nebula (M42) diffuse nebula 410 janskies
Virgo A (M87) radio galaxy 220 janskies
M82 radio galaxy 8 janskies

 

The radio signal from 47 Ursae Majoris is divided into pulses.  Each pulse lasts 0.38 seconds followed by a delay of 0.38 seconds before the next pulse.  Each pulse is rectangular in shape.  Pages are delimited by extended delays lasting 24.32 seconds (64 times the duration of a single pulse).  Each page is repeated 1,024 times before being replaced by the next page.  There are seven pages in total.  Each pulse is frequency shifted relative to the carrier frequency by one of the following 13 values.  We denote each specific frequency shift by a unique letter starting at A.

Frequency Shifts relative to Carrier Frequency

Frequency Shift

Symbol

84.7 Hz A
100.7 Hz B
119.8 Hz C
142.4 Hz D
169.4 Hz E
201.5 Hz F
239.6 Hz G
284.9 Hz H
338.8 Hz I
402.9 Hz J
479.1 Hz K
569.8 Hz L
677.6 Hz M

Each frequency shift is 1.189 (i.e., the 4th root of 2.0) times the previous frequency shift.  We can convert the frequency shifts into sound pulses for the purposes of this web site.  This allows us to listen to each page as a piece of interstellar music.

 

Click on each of the following links to go to the specific page of the interstellar message.  Each page has both a symbol representation and a sound representation plus notes on how to translate the message into English.

Page 1
Page 2
Page 3
Page 4
Page 5
Page 6
Page 7