Objects - The Sun

Obects & Observing Tips:

The Sun

NASA photo of the Sun
[NASA photo]

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Sun Facts
Spectral type	G2 V
Distance from Earth	Mean: 150 million km (= 1 AU) Range: 147-152 million km
Temperature	Surface: 5800° K Chromosphere: 30,000° K Core: 16,000,000° K
Mass	2 x 10^{30 kg}	^{333,000 times that of Earth The Sun contains 99.86% of the mass in the solar system.}
Diameter	1,400,000 km	109 times that of Earth
Volume	10 trillion km³	1.3 million times that of Earth
Density	1.4 g/cm³	1/4 that of Earth
Magnitude	Visual: -26.74	Absolute: 4.8
Apparent diameter	32 arcminutes
Rotation period	25 Earth days at equator; 35 days near the poles
Age	4.6 billion years	(expected total lifespan: 10 billion years)
Data sources: NASA factsheet and Solar System Exploration site (see below) Robert Burnham et al., Advanced Skywatching, 1997

Sunspots:
Great storms originate from Sunspots. These are call CMEs (Coronal Mass Ejections). The average amount of matter shot off into space by CME is 80,000,000 tons. These magnetically charged photons rush off into space in all directions. When a storm is directed at Earth it arrives about 2 days later and can cause gorgeous aurora borealis displays. Our electrical systems can also be damaged severely under the right circumstances. This is why it is very important to keep close watch of the Sun. Also, anyone in space, such as on the ISS or space shuttles need to take cover to protect themselves against dangerous radiation during these storms.
Measuring Up:
By mass, our Sun is in the top 15% or so of stars, but is small in comparison with the many "giant" stars. The red giant Betelguese, for instance, is so enormous it would fill up the entire area encircled by the orbit of Mars.
Cycles:
the Sun becomes very active with flares and storms about every 11 years, then becomes quiet again. We are currently experiencing Double Solar Max. The Sun is not quieting on schedule, but is continuing its fury with great spots and CME's. Auroras are being been seen as far south as our southern states and northern Mexico.

Observing Notes:

The sun can be safely observed by projection - as with our Sunspotter, or with an appropriate solar filter. The Sun can be The Observatory does not own a solar filter for any of its telescopes, but several volunteers have scopes equipped with filters for viewing sunspots. We generally have solar viewing on second Saturdays.
One of our goals is to obtain a hydrogen-alpha filter for viewing solar flare and prominences

ACRIMSAT (acrim.jpl.nasa.gov): measuring the sun's energy
RHESSI (hesperia.gsfc.nasa.gov/hessi): studies the physics of solar flares
SOHO, Solar & Heliospheric Observatory: sohowww.nascom.nasa.gov
SOHO orbits the Sun about 1.5 million km away from Earth, sending back solar data and images, along with comet discoveries and other observations.
Factsheet (pdf): sohowww.nascom.nasa.gov/mission/SOHO_Fact_Sheet.pdf
SORCE, Solar Radiation and Climate Experiment: lasp.colorado.edu/sorce
TRACE, Transition Region and Coronal Explorer: vestige.lmsal.com/TRACE
Ulysses (ulysses.jpl.nasa.gov) studies the sun at all latitudes

Websites for Information on the Sun:

NASA factsheet: nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
NASA Solar System Exploration site: solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Sun
Space Weather: www.spaceweather.com
current location of sunspots and other information about the sun's activity
SDAC (Solar Data Analysis Center, NASA): umbra.nascom.nasa.gov/
SOHO's "Our Star" site: sohowww.nascom.nasa.gov/explore/sun101.html
NASA's Solar Physics site - full of facts, photos and articles with details of solar features