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Spring dust makes stars look redder

The first total lunar eclipse of 2014 as seen Tuesday morning high above Durango. It was the first of a “tetrad” of four lunar eclipses in 2014 and 2015; the next one being Oct. 8. This eclipse was what some term a “blood moon” because of the red that was displayed as sunlight was bent by the Earth’s atmosphere.

Greetings, stargazers.

Visitors to the Four Corners are often blown away by our outstanding skies. This month I have been blown away too, but that has been from the all-too-often red flag conditions in the afternoon. Unfortunately, during most evenings the “seeing,” or how astronomers describe the stability of the atmosphere for stargazing, has been terrible as a result of these conditions.

In addition to the turbulence from the wind, there is also the dust and smoke that comes with it. If you haven’t noticed, dust in the atmosphere makes things look much browner or redder than they normally would. This is because blue light is scattered away from its initial path much more efficiently than red light, leaving the redder colors to reach our eyes more easily.

The same blue scattering happens with clear air, just not as noticeably. This is why sunsets are red – when the sun is on the horizon there is a longer path through the air for the light to traverse, and thus more opportunity for the blue light to be scattered away.

The reddening of stars also happens when their light has to go through interstellar clouds of gas and dust before it gets to us. This is particularly noticeable for stars seen along the plane of the Milky Way. Some of those clouds are so thick that even visible red light is scattered away, leaving only infrared light that gets through. Instruments that are sensitive to infrared light, such as the new James Webb Space Telescope, are particularly useful for seeing stars through these clouds.

This month

Sunday night we will be treated to a total lunar eclipse. If you have a clear horizon to the east, you can watch the full moon rise shortly after 8 p.m. Although the penumbral (partial) eclipse will have already started by then, the moon will look bright and fully lit.

By 9:29 p.m., it should be entirely in the Earth’s shadow, and have the rusty, “blood” red color these eclipses are known for. The red comes from what little light is hitting the edge of the Earth and passing through the thin atmospheric layer where the blue light is scattered away. Totality will last until 10:54 p.m.

Useful links

NASA ECLIPSE PAGE: https://go.nasa.gov/38mKETt.

INTERNATIONAL DARK-SKY ASSOCIATION: www.darksky.org.

ASTRONOMY PICTURE OF THE DAY: http://apod.nasa.gov/apod.

OLD FORT LEWIS OBSERVATORY: www.fortlewis.edu/observatory.

AN ASTRONOMER’S FORECAST FOR DURANGO: https://bit.ly/2eXWa64.

FOUR CORNERS STARGAZERS: https://bit.ly/2pKeKKa.

https://bit.ly/3hOMKwh.

Many are familiar with the pointer stars in the Big Dipper. Because the North Star is rather dim and the Big Dipper is relatively bright, it is easier to find Polaris using the pointers Duhbe and Merak. This month the Dipper is at its highest point in the sky in the early evening, with the handle pointing to the east. In this orientation, Duhbe and Merak are the leftmost stars. You would follow the line made by these two stars almost straight down about 30 degrees to find Polaris.

What most people don’t know is that the same two pointer stars can be used to find Leo. By going along the same line, but in the opposite direction, you can find the bright star Regulus near the head of the lion. Both Ursa Major and Leo have lots of galaxies that can be seen with small telescopes, but you should get a star chart to help locate the brightest ones.

The easily seen planets Saturn, Mars, Jupiter and Venus make a nice line along the ecliptic in the early morning sky. Uranus, Neptune and Pluto are also there, but you would need a telescope. By the beginning of June, Mercury will join the party, giving us a rare opportunity to see all the planets in such a line.

Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory. Reach him at hakes_c@fortlewis.edu.