During the week of May 13th, the CO2 level at the Mauna Loa Observatory in Hawaii topped 400 ppm repeatedly. Daily levels of CO2 can vary due to weather, and there are seasonal trends as well. The level of atmospheric greenhouse gases continues to increase, now over 120 ppm since the Industrial Revolution began. For more on the Keeling Curve, see http://keelingcurve.ucsd.edu/. Find out more about greenhouse gases and warming.
The week of May 19 brings dozens of tornadoes to Tornado Alley in the states of Oklahoma, Kansas, Iowa, Illinois and Missouri. On May 20th, a massive tornado struck Moore, Oklahoma, devastating communities - destroying over 100 homes and hitting two elementary schools and a hospital - with many casualties and deaths. Our thoughts are with our friends and colleagues suffering from these storms. For more on the May 20th storms, see the NOAA Storm Prediction Center Storm Report.
All through the galaxy, we find stars that pulsate. Gravity makes stars
spherically symmetric. Because of this symmetry, we can describe the
pulsations with mathematical functions called spherical harmonics. The
patterns of these functions depend on two numbers, usually called the
spherical degree ("l") and the azimuthal order ("m").
The spherical degree changes the total number of hot and cool zones on the
surface. The azimuthal order can only be between "-l" and "+l", and
changes how the hot and cool zones are distributed on the surface of the
From a distance, we can only see the brightness of a star change when the
spherical degree is small. Play with the values of "l" and "m" to see some
of the different ways stars can pulsate.
I am Katrien, a Belgian astronomer. I have been working in several European countries and I am currently based in Paris, France. My research is very exciting as I study stars that pulsate! This means...more
Hi to all from the IAC80 telescope on the island of Tenerife, hidden away on the Canary Islands. Last month, one of my friends, Katrien, was here and she told you a little about observing stars that pulsate....more
In recent years astronomers have become able to detect "starspots" on distant stars! Like the sunspots that frequently dot the "surface" of the nearest star, our Sun, starspots are relatively cool, dark...more
Astronomers use the term "magnitude" to describe the brightness of an object. The magnitude scale for stars was invented by the ancient Greeks, possibly by Hipparchus around 150 B.C. The Greeks grouped...more
Because of the rotation of the Earth and its orbit around the Sun, we divide the stars and constellations into two groups. Some stars and constellations never rise nor set, and they are called circumpolar....more
In the 1960's, the United States launched a series of satellites to look for very high energy photons, called Gamma Rays, that are produced whenever a nuclear bomb explodes. These satellites soon detected...more
The introduction of telescopes to the study of astronomy opened up the universe, but it took some time for astronomers to realize how vast the universe could be. Telescopes revealed that our night sky...more