2009 International Year of
Astronomy
The Sun-Earth
Connection
Dr. Laura Peticolas
Space Sciences Laboratory
University of California at
Berkeley
Tonight’s main talking points
• We learn about our connection to the Sun
through careful observations.
• Tools (such as telescopes, satellites,
computers) help us to understand this
connection.
• The Sun emits light of many different
colors (wavelengths/frequencies) known
as the electromagnetic spectrum.
Tonight’s main talking points
• The Sun is a magnetic and dynamic star,
ever changing in its output of light and
particles.
• Earth is a giant electromagnet.
• The northern and southern lights (auroras)
are global, dynamic glowing light displays
originating at the boundary between
Earth’s atmosphere and space.
• The Sun’s particles affect the magnetic
field surrounding Earth in a dynamic way.
1600s:Birth of the Telescope
Telescopes
increased the
ability of people to
see details in
astronomical
objects such as
the moons around
Jupiter and spots
on the Sun.
Johannes Hevelius
observing with one of his
telescopes (from
galileo.rice.edu)
Galileo’s telescopes
(from galileo.rice.edu)
Sunspots: Observations
In 1612 during the
summer months,
Galileo made a series
of sunspot
observations which
were published in
Istoria e Dimostrazioni
Intorno Alle Macchie
Solari e Loro Accidenti
Rome (History and
Demonstrations
Concerning Sunspots
and their Properties,
published 1613).
Galileo’s sunspot drawing (from galileo.rice.edu)
Sunspots: Observations
Because these
observations were
made at
approximately the
same time of day,
the motion of the
spots across the Sun
can easily be seen.
Conclusion: the Sun
rotates on its axis.
Movie made from Galileo’s sunspot drawings from
June 2, 1613 – July 8, 1613 (from galileo.rice.edu)
Sunspots: A modern
understanding
Sunspots are about 2,000 degrees
Kelvin cooler than the average
temperature on the photosphere
(5,000 degrees Kelvin).
They are bright but appear to be
dark only in comparison to their
very bright surroundings.
Following long-lived sunspots
through time allows one to
determine the rotation rate of the
Sun (25-36 days).
The Sun spins faster at the equator
(25 days) than at the poles (36
days).
What is the Sun?
The Sun is a Star, but seen
close-up.
The Stars are other Suns
but very far away.
Radius
696,000 km (109 times Earth’s radius)
Rotation Rate
27 days (equator) to 31 days (poles)
Luminosity
(Power Output)
3.8 x 1026 watts (10 trillion times the power
consumption of all Earth’s nations combined)
Surface Temperature
5,800 K (average)
Mass
2 x 1030 kg (300,000 times Earth’s mass)
Composition
70% Hydrogen, 28% Helium, 2% heavier elements
(by percentage of mass)
Age
5 billion years (expected to live another 5 billion)
Distance from Earth
The Sun is 150 million kilometers away from Earth.
This is defined as 1 Astronomical Unit (AU)
Stars, including the Sun, are giant
balls of very hot, mostly ionized gas
that shine under their own power
(from nuclear fusion).
Modern Solar Science:
Careful Observations
In 2006 NASA launched the
STEREO (Solar Terrestrial
Relations Observatory)
spacecraft to continue our study
of the Sun in ways not possible
on Earth.
To understand why the scientific
instruments (tools) on the
spacecraft needed to be above
Earth’s atmosphere and
magnetic field, we need a little
more background.
Light: Careful Observations
1666 A.D. Sir Isaac
Newton used a prism
to show that white
light from the Sun
disperses to form a
series of colors called
the spectrum
Prism with white light shining through the
prism, shown at the top of the image, and
the rainbow of colors (spectrum) coming
out of the prism, shown at the bottom of
the image.
Electromagnetic Spectrum
1800 A.D.
Fredrick W.
Herschel used
a prism and
thermometers
to measure the
temperature of
each color of
light. During this
experiment he
placed a
thermometer to
one side of the
spectrum and
discovered
infrared light.
The Multiwavelength Sun
Looking at the Sun in different wavelengths of light reveals
different parts of the Sun with different temperatures.
2 dark spots
2 bright spots
Visible light
(white light):
Wavelength =
400-700 nm
T = 5,800 K
Fe XII Extreme
Ultraviolet light:
Wavelength =
19.5 nm
T = 1.5 million K
2 bright spots
2 bright spots
He II Extreme
Ultraviolet light:
Wavelength =
30.4 nm
T = 60,00080,000 K
Fe IX, X
Extreme
Ultraviolet light:
Wavelength =
17.1 nm
T = 1 million K
The Multiwavelength Sun
The Extreme Ultraviolet Light (EUV light) is blocked by our
atmosphere – we have to go to space to get these images.
2 bright spots
2 dark spots
Earth-based image
Space-based image
(STEREO)
Visible light
(white light):
Wavelength =
400-700 nm
T = 5,800 K
Space-based image
(STEREO)
Fe XII Extreme
Ultraviolet light:
Wavelength =
19.5 nm
T = 1.5 million K
2 bright spots
2 bright spots
He II Extreme
Ultraviolet light:
Wavelength =
30.4 nm
T = 60,00080,000 K
Fe IX, X
Extreme
Ultraviolet light:
Wavelength =
17.1 nm
T = 1 million K
Space-based image
(STEREO)
Observations of the Sun
Images from NASA TRACE
‘Zoom in’ images of the Sun in ultraviolet light reveal
loops of hot ionized gas (plasma) trapped in
magnetic fields above the locations of Sunspots.
The Magnetic Sun
N
S
Above: Magnetic field tracing above
sunspots on the visible Sun.
Left: Magnetic field tracing
using a compass around two
magnetic poles
STEREO Views: June 2007
http://stereo-ssc.nascom.nasa.gov
STEREO camera B
STEREO camera A
STEREO Viewing geometry.
The Sun in 3D
STEREO Views: April 2009
http://stereo-ssc.nascom.nasa.gov
STEREO camera B
Now we can
study the sides
of the Sun we
cannot normally
take images of.
SOHO camera
STEREO camera A
STEREO Viewing geometry.
SOHO is located near Earth
between Earth and the Sun
(i.e. looking straight to the
Sun from Earth)
Atmosphere of the Sun
During a total eclipse of the Sun, the very bright
Photosphere is blocked and the Sun’s outer atmosphere
becomes visible (in white light). We call it the Corona.
Spacecraft, like SOHO and
STEREO, place a disk in front of
their cameras to create an eclipse.
They are then able to take images
with a larger view of the Sun’s
Corona.
It extends far out into the Solar
System, in fact we live in it!
Solar Flares & CMEs
Solar flares are enormous
explosions in the atmosphere of
the Sun.
They release energy in the form of
light, heat, and the movement of large
amounts of plasma.
Coronal Mass Ejections
(CMEs) are literally ejections
of mass from the Sun’s
corona.
CMEs occur when large-scale
magnetic fields “break” and
release energy and enormous
amounts of matter into space.
STEREO CMEs – new!
Coronal Mass Ejections (CMEs) are literally ejections of
mass from the Sun’s corona.
CMEs occur when large-scale magnetic fields “break” and release
energy and enormous amounts of matter into space.
CME
continues into
the solar
system
The Solar Wind
The solar wind is a
stream of mostly
charged particles that
emanate from the Sun
and blow throughout
the Solar System. The
Suns Magnetic field
flows with these
particles.
We have turned the data from these charged
particles and magnetic fields into sounds and
put the sounds with a movie of the outermost
atmosphere of the Sun from STEREO. We are
watching the Sun’s outer atmosphere from far
away while listening to the solar wind data
nearby the spacecraft. Find out more here
http://cse.ssl.berkeley.edu/impact/sounds.html
Earth
Earth’s Magnetic Field:
Careful Observations
In the late 1500's, William
Gilbert realized that the
compass was a tiny
magnet and it was
interacting with a larger
magnetic field in order to
point north.
In 1600, he published "De
Magnete" explaining that
"the globe of the earth is
magnetic, a magnet,"
Chapter 17, Book 1.
Satellite observations:
Earth’s Magnetosphere
The solar
wind is
electrically
and
magnetically
connected to
Earth’s
magnetosphere
Satellite data (from sophisticated compasses and particle
detectors) out into space compared with computer
models gives us this model for Earth’s Magnetosphere.
Aurora Observations in 1800s
La Recherche Expedition, 1838-1840
(woolgathersome.blogspot.com)
August 28, 1859
Galveston, Texas:
“August 28 as early as twilight closed, the northern sky
was reddish, and at times lighter than other portions of
the heavens. At 7:30 PM a few streamers showed
themselves. Soon the whole sky from Ursa Major to the
zodiac in the east was occupied by the streams or spiral
columns that rose from the horizon. Spread over the
same extent was an exquisite roseate tint which faded
and returned. Stately columns of light reaching up about
45 degrees above the horizon moved westward. There
were frequent flashes of lightning along the whole extent
of the aurora. At 9:00 PM the whole of the streaking had
faded leaving only a sort of twilight over the northern
sky.”
Observations from Space
North
Oval
South Oval
Cusp
Aurora
Aurorae are found in an
oval around the North
and South Magnetic
Poles.
These ovals are always
present.
Images on the left
are from the
IMAGE satellite in
2001 and 2004
(UV Light) with
continents drawn
on image.
Image on
the right is from the
Polar Satellite, 2001
(UV Light.)
Both Ovals
Aurora observed in 2008
from the ground (aurora oval detail)
THEMIS All-sky camera mosaic image of aurora across the Northern American
Continent. The cameras looking up using cameras with a wide field-of-view.
Sun-Earth Connection
(1128 A.D.)
In 2001, Astronomers drew a link between
the earliest known record of sunspots, drawn
by John of Worcester in England in AD 1128,
and the aurora borealis (northern lights)
recorded in Korea five days later.
http://www.abc.net.au/science/articles/2001/07/18/330954.htm
Space Weather Effects
• Energy from Solar Flares and CMEs can damage satellites and change
orbits.
• Disrupt radio communications
• CME particles traveling near the speed of light threaten Astronauts.
• CMEs can intensify auroras (Northern and Southern Lights)
• Electric currents from intense aurora can cause power surges and
blackouts.
• Electric currents from intense aurora create interesting magnetic field
variations detectable on Earth.
Magnetic Reconnection Model – confirmed
for one case in 2008
• When a CME passes
Earth, it can “drag” the
magnetic tail far out into
space.
• Stretched magnetic
lines can break and
then reconnect into a
different shape.
• Electrons, guided by
the magnetic field,
speed up towards Earth
and enhance auroras.