Proposed captions (a.k.a. “solar haiku”) appear in regular typeface.
Comments and image suggestions appear in italics.
Our nearest star, the Sun, provides the energy that makes life on Earth possible.
We monitor and document how the Sun changes over time, in ways that can affect everything from weather on Earth to satellites in space.
The most noticable features on the visible Sun are sunspots, relatively cool regions that appear slightly darker than their surroundings.
The Sun emits most of its light in wavelengths we can see. But it produces an entire spectrum of radiation, from long-wavelength, low-energy radio and infrared light to short-wavelength, high-energy ultraviolet and x-rays.
The Solar and Heliospheric Observatory (SOHO) makes regular observations of the Sun at many different wavelengths, revealing day-to-day changes in the solar environment.
[SOHO is a project of the European Space Agency in collaboration with NASA.]
In extreme ultraviolet light, we see helium heated to 100,000 degrees Fahrenheit...
[The Sun consists primarily of hydrogen; helium accounts for only 10% of the atoms in the Sun.]
And at even shorter wavelengths, we observe plumes at temperatures of more than two million degrees Fahrenheit.
A circle at the center of the image represents the disc of the Sun, blocked by SOHO to create an artificial solar eclipse that allows the telescope to see the faint, tenuous gas in the Sun’s corona.
The small circle at the center again represents the size and position of the Sun, but now we are looking at a region nearly 28 million miles across. Points of light crossing from left-to-right in the image are background stars.
A storm of energetic particles released by the Sun can often overwhelm SOHO’s special detectors, giving images a scratched or mottled appearance.
By viewing the Sun at different wavelengths and monitoring it over time, SOHO and other solar telescopes allow us to gain a fuller understanding of our nearest star.
The Sun takes about a month to rotate once, as seen in this sequence of images from SOHO. Currently, the Sun is near its minimum level of activity, so we see very few sunspots.
The Sun in Visble Light (from MPI)
Helium heated to temperatures around 100,000 degrees Fahrenheit emits light at ultraviolet wavelengths — highlighting solar prominences, fountains of cool, dense gas that originate in regions of magnetic instability.
(N.B. that the preceding image sequence is much shorter than they’d normally be because of the bakeout that just wrapped up on 1 April.)
At even shorter wavelengths, we observe radiation emitted by trace amounts of iron at temperatures over 2 million degrees Fahrenheit, revealing magnetic loops and plumes of outward-flowing gas.
(N.B. that the preceding image sequence is much shorter than they’d normally be because of the bakeout that just wrapped up on 1 April.)
A circle at the center of the image represents the disc of the Sun, blocked by SOHO to create an artificial solar eclipse that allows the telescope to see the faint, tenuous gas in the Sun’s corona.
The small circle at the center again represents the size and position of the Sun, but now we are looking at a region nearly 28 million miles across. Points of light crossing from left-to-right in the image are background stars.