
Explore the galactic map that could guide aliens to Earth
To potentially help extraterrestrials locate Earth, a pulsar map was first sent into space in 1972 attached to Pioneer 10. That spacecraft is still traveling on to the stars, but time and space are taking a toll on the cosmic coordinates it carries. The map gets increasingly unreliable as the galaxy rotates and our sun and its reference points—pulsars, the spinning cores of collapsed stars—change their relative positions. So one astronomer, Scott Ransom, is proposing a new map to overcome these weaknesses.
BY MATTHEW W. CHWASTYK & DIANA MARQUES
The original map contained four elements
An atomic hydrogen diagram marks a 21-cm distance.
Old pulsar map
Human figures are shown to scale in front of the Pioneer spacecraft.
Pioneer’s trajectory is shown on a solar system diagram.
What is a pulsar?
After a supernova—the titanic explosion of a massive star—the star’s core can become incredibly dense. It is called a “pulsar” if it’s set spinning, emitting radio waves that appear to pulse on and off like a lighthouse.
The Crab Nebula is a supernova remnant with a pulsar at its core.
To make a new map,
start with stable signposts
If a small, dense pulsar is paired with another star, it siphons material and energy from its companion, accelerating the pulsar’s already rapid rotation.
At up to 43,000 rotations per minute, the radiation appears to pulse and acts like a beacon. This system is a reliable signpost for mapping within the Milky Way.
Millisecond pulsar
Magnetic
field
Companion
white dwarf star
Radiation
beam
Pulsar
rotation
System rotation
Then, add reference points
Much like how the Global Positioning System (GPS) works on Earth, these galactic beacons could provide a map to the sun. By identifying these specific pulsars and how much their
spins have changed, you reveal the sun’s location—and Earth is right nearby.
Earth orbital plane
Pulsar 1
Outer planetary orbit
Inner
solar
system
Pulsar 2
Pulsar 3
Finally, add a universal ruler
Our measurements of time and distance would be unfamiliar
to aliens. Hydrogen is a good universal alternative. When a hydrogen electron flips the direction of its spin, it emits a radio wave with a wavelength
of about 21 centimeters, the distance light travels in just
over 0.7 nanoseconds.
Spins are parallel
Hydrogen atom
Proton
Electron
21-cm
wavelength radiation
Spins are antiparallel
The new map
These new coordinates might
more accurately guide extrater-
restrial life to Earth for the next
billion years or so. Both more
distant and relatively closer guide
pulsars are used. The map
encodes how quickly rapidly
spinning pulsars rotate (rotational
periods) and how quickly star-
pulsar systems revolve around
each other (orbital periods).
DISTANT Pulsars
|--||--|-|--|-|--|-|||-X-|-||-||--|||-|-|-|-|-|-||||--||
47 Tucanae
(two binary pulsars)
|---|-||--|-|---|||--|-X-||-|-----||-|-|-|-||---|-|-|
|-----|||--|-|------||---|--||||-|--|----|---|---
|||||-|||||--||--||----|-|||-----|-----|||-|||--
Terzan 5
(two binary
pulsars)
|-|||-||||-|-|||||||-|||X|--||-|-||||--|--|-|---|||
|-|-||-----||--||-|-|-||----|||-|--|||---|---
||--||||-||-|-||||-|-|-|X|||||||-|||--|--|||---|--|||
NGC 1851
(one binary pulsar)
|--|-|----||-|---||------|------||-------|---|--
||-||----|-|-|--------|X|--||---|||-|||-||-|------|-||
|-----||----|-|||--|||-||-|-||--||--||-||||||||-----
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
|----|||--|-|-||-||--||X-||-|-||--|-|---|-||-||-||-||
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
Near Pulsars
|----|-------|||-|--|-|-|||-|-||-||--|-||-|-||||-
|---||--|---|--|-|||||-||||--||||||--|-|-|---|--
|--||---|||-|||-|-|||-|X-||-|------|||||--||---|||||-|
J0218+4232
Messier 13
(two binary
pulsars)
Near Pulsars
|---|---|--|-|---|----|X-|-|---||||-----|||--|||--|||
||||--|--||--|----||-----||--|--------||-||||-|---
J1614-2230
J0614-3329
|---|----|||||--|---|--X-||---|||--||--||--------|||
|-|||-|-|||--|||--||------|--|--|--|-|-||||--||------
J2043+1711
||--|||--|-|--|-|-|--|X|-||-||-|-|--|-||-||-|-|--||
|-|--|-|-|||--|-|-----||||-|-|-|---|||--|-|||---
Binary ( | = 1 or - = 0, X=decimal point)
encoding for the rotational period of the pulsar and orbital period of the star pair in units of time based on the hydrogen wavelength
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
J0218+4232
SEAN MCNAUGHTON; NEW PULSAR MAP: SCOTT RANSOM; MILKY WAY: ANTOINE COLLIGNON
SOURCES: NASA GODDARD SPACE FLIGHT CENTER; NATIONAL RADIO ASTRONOMY OBSERVATORY; HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
READ THE FULL STORY

Explore the galactic map that could guide aliens to Earth
To potentially help extraterrestrials locate Earth, a pulsar map
was first sent into space in 1972 attached to Pioneer 10. That
spacecraft is still traveling on to the stars, but time and space are
taking a toll on the cosmic coordinates it carries. The map gets
increasingly unreliable as the galaxy rotates and our sun and its
reference points—pulsars, the spinning cores of collapsed
stars—change their relative positions. So one astronomer, Scott
Ransom, is proposing a new map to overcome these weaknesses.
BY MATTHEW W. CHWASTYK & DIANA MARQUES
The original map
Atomic hydrogen diagram marks a 21-cm distance.
Human figures are shown to scale in front of the Pioneer spacecraft.
Old pulsar map
Pioneer’s trajectory is shown on this solar system diagram.
What is a pulsar?
After a supernova—the titanic explosion of a massive star—the star’s core can become incredibly dense. It is called a “pulsar” if it’s set spinning, emitting radio waves that appear to pulse on and off like a lighthouse.
The Crab Nebula is a supernova remnant with a pulsar at its core.
To make a new map, start with stable signposts
If a small, dense pulsar is paired with another star, it siphons material and energy from its companion, accelerating the pulsar’s already rapid rotation. At up to 43,000 rotations per minute, the radiation appears to pulse and acts like a beacon. This system is a reliable signpost for mapping within the Milky Way.
Millisecond pulsar
Magnetic
field
Companion
white dwarf star
Radiation
beam
Pulsar
rotation
System rotation
Then, add reference points
Much like how the Global Positioning System (GPS) works on Earth, these galactic beacons could provide a map to the sun. By identifying these specific pulsars and how much their spins have changed, you reveal the sun’s location—and Earth is right nearby.
Pulsar 1
Outer planetary orbit
Pulsar 2
Inner
solar
system
Pulsar 3
Finally, add a universal ruler
Our measurements of time and distance would be unfamiliar to aliens. Hydrogen is a good universal alternative. When a hydrogen electron flips the direction of its spin, it emits a radio wave with a wavelength of about 21 centimeters, the distance light travels in just over 0.7 nanoseconds.
Spins are parallel
Hydrogen atom
Proton
Electron
21-cm
wavelength radiation
Spins are antiparallel
The new map
These new coordinates might more accurately guide extraterrestrial life to Earth for the next billion years or so. Both more distant and relatively closer guide pulsars are used. The map encodes how quickly rapidly spinning pulsars rotate (rotational periods) and how quickly star-pulsar systems revolve around each other (orbital periods).
DISTANT Pulsars
|--||--|-|--|-|--|-|||-X-|-||-||--|||-|-|-|-|-|-||||--||
47 Tucanae
(two binary pulsars)
|---|-||--|-|---|||--|-X-||-|-----||-|-|-|-||---|-|-|
|-----|||--|-|------||---|--||||-|--|----|---|---
|||||-|||||--||--||----|-|||-----|-----|||-|||--
Terzan 5
(two binary pulsars)
|-|||-||||-|-|||||||-|||X|--||-|-||||--|--|-|---|||
|-|-||-----||--||-|-|-||----|||-|--|||---|---
||--||||-||-|-||||-|-|-|X|||||||-|||--|--|||---|--|||
|--|-|----||-|---||------|------||-------|---|--
NGC 1851
(one binary pulsar)
||-||----|-|-|--------|X|--||---|||-|||-||-|------|-||
|-----||----|-|||--|||-||-|-||--||--||-||||||||-----
Messier 13
(two binary pulsars)
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
|----|||--|-|-||-||--||X-||-|-||--|-|---|-||-||-||-||
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
Near Pulsars
|----|-------|||-|--|-|-|||-|-||-||--|-||-|-||||-
|---||--|---|--|-|||||-||||--||||||--|-|-|---|--
|--||---|||-|||-|-|||-|X-||-|------|||||--||---|||||-|
J0218+4232
|---|---|--|-|---|----|X-|-|---||||-----|||--|||--|||
||||--|--||--|----||-----||--|--------||-||||-|---
Near Pulsars
J1614-2230
J0614-3329
|---|----|||||--|---|--X-||---|||--||--||--------|||
|-|||-|-|||--|||--||------|--|--|--|-|-||||--||------
||--|||--|-|--|-|-|--|X|-||-||-|-|--|-||-||-|-|--||
J2043+1711
|-|--|-|-|||--|-|-----||||-|-|-|---|||--|-|||---
Binary ( | = 1 or - = 0, X=decimal point)
encoding for the rotational period of
the pulsar and orbital period of the
star pair in units of time based on the
hydrogen wavelength
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
J0218+4232
Earth in the Milky Way
This rendering shows how the mapped
pulsars relate to our solar system.
270°
240°
300°
0°
210°
Terzan 5
19,200 LY
30°
below
galactic
plane
Terzan 5
19,200 LY
Core
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
J1614-2230
2,100 LY
60°
47 Tucanae
(NGC 104)
14,700 LY
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
SOLAR SYSTEM
NGC 1851
39,500 LY
J2043+1711
4,500 LY
J0614-3329
2,000 LY
J0614-3329
2,000 LY
above
galactic
plane
90°
Direction of
galactic rotation
J0218+4232
10,300 LY
120°
150°
Millisecond pulsar
(pulsar with a rotational period
measured in fractions of a second)
Globular cluster containing
millisecond pulsar
SEAN MCNAUGHTON; NEW PULSAR MAP: SCOTT RANSOM; MILKY WAY: ANTOINE COLLIGNON
SOURCES: NASA GODDARD SPACE FLIGHT CENTER; NATIONAL RADIO ASTRONOMY OBSERVATORY; HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
READ THE FULL STORY

Explore the galactic map that could guide aliens to Earth
To potentially help extraterrestrials locate Earth, a pulsar map was first
sent into space in 1972 attached to Pioneer 10. That spacecraft is still
traveling on to the stars, but time and space are taking a toll on the cosmic
coordinates it carries. The map gets increasingly unreliable as the galaxy
rotates and our sun and its reference points—pulsars, the spinning cores of
collapsed stars—change their relative positions. So one astronomer, Scott
Ransom, is proposing a new map to overcome these weaknesses.
BY MATTHEW W. CHWASTYK & DIANA MARQUES
The original map
Atomic hydrogen diagram marks a 21-cm distance.
Human figures are shown to scale in front of the Pioneer spacecraft.
Old pulsar map
Pioneer’s trajectory is shown on this solar system diagram.
What is a pulsar?
After a supernova—the titanic explosion of a massive star—the star’s core can become incredibly dense. It is called a “pulsar” if it’s set spinning, emitting radio waves that appear to pulse on and off like a lighthouse.
The Crab Nebula
is a supernova remnant with a pulsar at its core.
To make a new map, start with stable signposts
If a small, dense pulsar is paired with another star, it siphons material and energy from its companion, accelerating the pulsar’s already rapid rotation. At up to 43,000 rotations per minute, the radiation appears to pulse and acts like a beacon. This system is a reliable signpost for mapping within the Milky Way.
Millisecond pulsar
Magnetic
field
Companion
white dwarf star
Radiation
beam
Pulsar
rotation
System rotation
Then, add reference points
Much like how the Global Positioning System (GPS) works on Earth, these galactic beacons could provide a map to the sun. By identifying these specific pulsars and how much their spins have changed, you reveal the sun’s location—and Earth is right nearby.
Pulsar 1
Outer planetary orbit
Pulsar 2
Inner
solar
system
Pulsar 3
Finally, add a universal ruler
Our measurements of time and distance would be unfamiliar to aliens.
Hydrogen is a good universal alternative. When a hydrogen electron flips
the direction of its spin, it emits a radio wave with a wavelength of about
21 centimeters, the distance light travels in just over 0.7 nanoseconds.
Spins are parallel
Hydrogen atom
Proton
Electron
21-cm
wavelength radiation
Spins are antiparallel
The new map
These new coordinates might more accurately guide extraterrestrial life to Earth for the next billion years or so. Both more distant and relatively closer guide pulsars are used. The map encodes how quickly rapidly spinning pulsars rotate (rotational periods) and how quickly star-pulsar systems revolve around each other (orbital periods).
DISTANT Pulsars
|--||--|-|--|-|--|-|||-X-|-||-||--|||-|-|-|-|-|-||||--||
47 Tucanae
(two binary pulsars)
|---|-||--|-|---|||--|-X-||-|-----||-|-|-|-||---|-|-|
|-----|||--|-|------||---|--||||-|--|----|---|---
|||||-|||||--||--||----|-|||-----|-----|||-|||--
Terzan 5
(two binary pulsars)
|-|||-||||-|-|||||||-|||X|--||-|-||||--|--|-|---|||
|-|-||-----||--||-|-|-||----|||-|--|||---|---
||--||||-||-|-||||-|-|-|X|||||||-|||--|--|||---|--|||
|--|-|----||-|---||------|------||-------|---|--
NGC 1851
(one binary pulsar)
||-||----|-|-|--------|X|--||---|||-|||-||-|------|-||
|-----||----|-|||--|||-||-|-||--||--||-||||||||-----
Messier 13
(two binary pulsars)
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
|----|||--|-|-||-||--||X-||-|-||--|-|---|-||-||-||-||
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
Near Pulsars
|----|-------|||-|--|-|-|||-|-||-||--|-||-|-||||-
|---||--|---|--|-|||||-||||--||||||--|-|-|---|--
|--||---|||-|||-|-|||-|X-||-|------|||||--||---|||||-|
J0218+4232
|---|---|--|-|---|----|X-|-|---||||-----|||--|||--|||
||||--|--||--|----||-----||--|--------||-||||-|---
Near Pulsars
J1614-2230
J0614-3329
|---|----|||||--|---|--X-||---|||--||--||--------|||
|-|||-|-|||--|||--||------|--|--|--|-|-||||--||------
||--|||--|-|--|-|-|--|X|-||-||-|-|--|-||-||-|-|--||
J2043+1711
|-|--|-|-|||--|-|-----||||-|-|-|---|||--|-|||---
Binary ( | = 1 or - = 0, X=decimal point)
encoding for the rotational period of
the pulsar and orbital period of the
star pair in units of time based on the
hydrogen wavelength
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
J0218+4232
Earth in the Milky Way
This rendering shows how the mapped
pulsars relate to our solar system.
270°
240°
300°
0°
210°
Terzan 5
19,200 LY
30°
below
galactic
plane
Terzan 5
19,200 LY
Core
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
J1614-2230
2,100 LY
60°
47 Tucanae
(NGC 104)
14,700 LY
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
WE ARE HERE
SOLAR SYSTEM
NGC 1851
39,500 LY
J2043+1711
4,500 LY
J0614-3329
2,000 LY
J0614-3329
2,000 LY
above
galactic
plane
90°
Direction of
galactic rotation
J0218+4232
10,300 LY
120°
150°
Millisecond pulsar
(pulsar with a rotational period
measured in fractions of a second)
Globular cluster containing
millisecond pulsar
SEAN MCNAUGHTON; NEW PULSAR MAP: SCOTT RANSOM; MILKY WAY: ANTOINE COLLIGNON
SOURCES: NASA GODDARD SPACE FLIGHT CENTER; NATIONAL RADIO ASTRONOMY OBSERVATORY; HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
READ THE FULL STORY

Explore the galactic map that could guide aliens to Earth
To potentially help extraterrestrials locate Earth, a pulsar map was first sent into space in 1972 attached to Pioneer 10. That spacecraft is still traveling on to the stars, but time and space are taking a toll on the cosmic coordinates it carries. The map gets increasingly unreliable as the galaxy rotates and our sun and its reference points—pulsars, the spinning cores of collapsed stars—change their relative positions. So one astronomer, Scott Ransom, is proposing a new map to overcome these weaknesses.
BY MATTHEW W. CHWASTYK & DIANA MARQUES
The original map
Atomic hydrogen diagram marks a 21-cm distance.
Human figures are shown to scale in front of the Pioneer spacecraft.
Old pulsar map
Pioneer’s trajectory is shown on this solar system diagram.
What is a pulsar?
After a supernova—the titanic explosion of a
massive star—the star’s core can become
incredibly dense. It is called a “pulsar” if it’s
set spinning, emitting radio waves that
appear to pulse on and off like a lighthouse.
The Crab Nebula
is a supernova remnant
with a pulsar at its core.
To make a new map, start with stable signposts
Millisecond pulsar
If a small, dense pulsar is paired with
another star, it siphons material and
energy from its companion, accelerating
the pulsar’s already rapid rotation. At up
to 43,000 rotations per minute, the
radiation appears to pulse and acts like a
beacon. This system is a reliable signpost
for mapping within the Milky Way.
Magnetic
field
Companion
white dwarf star
Radiation
beam
Pulsar
rotation
System rotation
Then, add reference points
Pulsar 1
Much like how the Global Positioning System (GPS) works on Earth, these galactic beacons could provide a map to the sun. By identifying these specific pulsars and how much their spins have changed, you reveal the sun’s location—and Earth is right nearby.
Outer planetary orbit
Pulsar 2
Inner
solar
system
Pulsar 3
Finally, add a universal ruler
Spins are parallel
Hydrogen atom
Our measurements of time and distance would be
unfamiliar to aliens. Hydrogen is a good universal
alternative. When a hydrogen electron flips the
direction of its spin, it emits a radio wave with a
wavelength of about 21 centimeters, the distance
light travels in just over 0.7 nanoseconds.
Proton
Electron
21-cm
wavelength radiation
Spins are antiparallel
|---|---|--|-|---|----|X-|-|---||||-----|||--|||--|||
||||--|--||--|----||-----||--|--------||-||||-|---
The new map
These new coordinates might more accurately guide
extraterrestrial life to Earth for the next billion years
or so. Both more distant and relatively closer guide
pulsars are used. The map encodes how quickly
rapidly spinning pulsars rotate (rotational periods)
and how quickly star-pulsar systems revolve around
each other (orbital periods).
Near Pulsars
J1614-2230
J0614-3329
|---|----|||||--|---|--X-||---|||--||--||--------|||
|-|||-|-|||--|||--||------|--|--|--|-|-||||--||------
||--|||--|-|--|-|-|--|X|-||-||-|-|--|-||-||-|-|--||
J2043+1711
|-|--|-|-|||--|-|-----||||-|-|-|---|||--|-|||---
Binary ( | = 1 or - = 0, X=decimal
point) encoding for the rota-
tional period of the pulsar and
orbital period of the star pair in
units of time based on the
hydrogen wavelength
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
DISTANT Pulsars
|--||--|-|--|-|--|-|||-X-|-||-||--|||-|-|-|-|-|-||||--||
47 Tucanae
(two binary pulsars)
|---|-||--|-|---|||--|-X-||-|-----||-|-|-|-||---|-|-|
|-----|||--|-|------||---|--||||-|--|----|---|---
|||||-|||||--||--||----|-|||-----|-----|||-|||--
Terzan 5
(two binary pulsars)
|-|||-||||-|-|||||||-|||X|--||-|-||||--|--|-|---|||
|-|-||-----||--||-|-|-||----|||-|--|||---|---
||--||||-||-|-||||-|-|-|X|||||||-|||--|--|||---|--|||
|--|-|----||-|---||------|------||-------|---|--
NGC 1851
(one binary pulsar)
||-||----|-|-|--------|X|--||---|||-|||-||-|------|-||
|-----||----|-|||--|||-||-|-||--||--||-||||||||-----
Messier 13
(two binary pulsars)
|||---|--|||--|||--|||-||--||||-|--|--||--||-|--
|----|||--|-|-||-||--||X-||-|-||--|-|---|-||-||-||-||
||--|--|-||--||--|--||X--|---||-||---||---||-||-|-||
Near Pulsars
|----|-------|||-|--|-|-|||-|-||-||--|-||-|-||||-
|---||--|---|--|-|||||-||||--||||||--|-|-|---|--
|--||---|||-|||-|-|||-|X-||-|------|||||--||---|||||-|
J0218+4232
J0218+4232
Earth in the Milky Way
This rendering shows how the mapped
pulsars relate to our solar system.
300°
270°
0°
240°
30°
Terzan 5
19,200 LY
below
galactic
plane
Core
Terzan 5
19,200 LY
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
210°
60°
J1614-2230
2,100 LY
Messier 13
(NGC 6205)
23,100 light-years
(LY) from the sun
47 Tucanae
(NGC 104)
14,700 LY
WE ARE HERE
SOLAR SYSTEM
above
galactic
plane
NGC 1851
39,500 LY
J2043-1711
4,500 LY
J0614-3329
2,000 LY
J0614-3329
2,000 LY
90°
Direction of
galactic rotation
180°
J0218+4232
10,300 LY
120°
Millisecond pulsar
(pulsar with a rotational period
measured in fractions of a second)
150°
Globular cluster containing
millisecond pulsar
SEAN MCNAUGHTON; NEW PULSAR MAP: SCOTT RANSOM; MILKY WAY: ANTOINE COLLIGNON
SOURCES: NASA GODDARD SPACE FLIGHT CENTER; NATIONAL RADIO ASTRONOMY OBSERVATORY; HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS
READ THE FULL STORY