Spotless Sun: Blankest Year of the Space Age

Oct 01, 2008
Image: NASA

Astronomers who count sunspots have announced that 2008 is now the "blankest year" of the Space Age.

As of Sept. 27, 2008, the sun had been blank, i.e., had no visible sunspots, on 200 days of the year. To find a year with more blank suns, you have to go back to 1954, three years before the launch of Sputnik, when the sun was blank 241 times.

"Sunspot counts are at a 50-year low," says solar physicist David Hathaway of the NASA Marshall Space Flight Center. "We're experiencing a deep minimum of the solar cycle."

A spotless day looks like this (see image above).

The image, taken by the Solar and Heliospheric Observatory (SOHO) on Sept. 27, 2008, shows a solar disk completely unmarked by sunspots. For comparison, a SOHO image taken seven years earlier on Sept. 27, 2001, is peppered with colossal sunspots, all crackling with solar flares (right). The difference is the phase of the 11-year solar cycle. 2001 was a year of solar maximum, with lots of sunspots, solar flares and geomagnetic storms. 2008 is at the cycle's opposite extreme, solar minimum, a quiet time on the sun.

And it is a very quiet time. If solar activity continues as low as it has been, 2008 could rack up a whopping 290 spotless days by the end of December, making it a century-level year in terms of spotlessness.

Hathaway cautions that this development may sound more exciting than it actually is: "While the solar minimum of 2008 is shaping up to be the deepest of the Space Age, it is still unremarkable compared to the long and deep solar minima of the late 19th and early 20th centuries." Those earlier minima routinely racked up 200 to 300 spotless days per year.

Some solar physicists are welcoming the lull.

"This gives us a chance to study the sun without the complications of sunspots," says Dean Pesnell of the Goddard Space Flight Center. "Right now we have the best instrumentation in history looking at the sun. There is a whole fleet of spacecraft devoted to solar physics--SOHO, Hinode, ACE, STEREO and others. We're bound to learn new things during this long solar minimum."

As an example he offers helioseismology: "By monitoring the sun's vibrating surface, helioseismologists can probe the stellar interior in much the same way geologists use earthquakes to probe inside Earth. With sunspots out of the way, we gain a better view of the sun's subsurface winds and inner magnetic dynamo."

"There is also the matter of solar irradiance," adds Pesnell. "Researchers are now seeing the dimmest sun in their records. The change is small, just a fraction of a percent, but significant. Questions about effects on climate are natural if the sun continues to dim."

Pesnell is NASA's project scientist for the Solar Dynamics Observatory (SDO), a new spacecraft equipped to study both solar irradiance and helioseismic waves. Construction of SDO is complete, he says, and it has passed pre-launch vibration and thermal testing. "We are ready to launch! Solar minimum is a great time to go."

Coinciding with the string of blank suns is a 50-year record low in solar wind pressure, a recent discovery of the Ulysses spacecraft. The pressure drop began years before the current minimum, so it is unclear how the two phenomena are connected, if at all. This is another mystery for SDO and the others.

Who knew the blank sun could be so interesting? More to come...

Source: Science@NASA, by Dr. Tony Phillips

Explore further: UI researchers launch rockets in search of unseen parts of universe

add to favorites email to friend print save as pdf

Related Stories

Sun's activity in 18th century was similar to that now

Feb 09, 2015

Counting sunspots over time helps in knowing the activity of our star but the two indices used by scientists disagree on dates prior to 1885. Now an international team of researchers has tried to standardise ...

How do we study the Sun?

Feb 09, 2015

A quick think about optical astronomy would have you imagine that most of it takes place at night. Isn't that when the stars and galaxies come out to play? Well, that assumption makes at least one glaring ...

Sun may determine lifespan at birth, study finds

Jan 07, 2015

Could the Sun be your lucky—or unlucky—star? In an unusual study published Wednesday, Norwegian scientists said people born during periods of solar calm may live longer, as much as five years on average, ...

Stars' spins reveal their ages

Jan 05, 2015

When you're a kid every birthday is cause for celebration, but as you get older they become a little less exciting. You might not want to admit just how old you are. And you might notice yourself slowing ...

Recommended for you

Scanning Earth, saving lives

14 hours ago

A high-speed camera for monitoring vegetation from space and combating famine in Africa is being adapted to spot changes in human skin cells, invisible to the naked eye, to help diagnose skin diseases like ...

THEMIS camera helps NASA pick site for next Mars lander

17 hours ago

NASA's next Mars space probe, a lander named InSight, is due to touch down on the Red Planet in September 2016 with a mission focused on the planet's internal properties. Its landing place has been chosen ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

Sirussinder
1 / 5 (3) Oct 02, 2008
The sunspots are on the other side of the sun.
Velanarris
not rated yet Oct 04, 2008
The sunspots are on the other side of the sun.


/facepalm

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.