Friday, July 3, 2015

The Ellensburg WA sky for the week of 7/4/15

Saturday: Tonight, while you are looking at an explosion of fireworks, the NASA spacecraft Kepler may be looking at an “explosion” of exoplanets. So far, Kepler has found 1028 planets whose presence has been confirmed by other means and evidence of 4,664 planet candidates. Something is called a planet candidate when the light from a star being observed by Kepler dims in a systematic way. Astronomers still need to compare the pattern of dimming with the potential pattern of star wobble caused by being tugged on by one or more planets before they can say for certain that they have actually found planets orbiting these stars. But if even half of these stars show the characteristic wobble, it will more than double the number of planets known to orbit other stars, also known as exoplanets. And this is only the beginning. The Kepler spacecraft is monitoring the brightness of over 156,000 stars in the constellations Cygnus the swan and Lyra the lyre. This region is midway between the bright stars Deneb and Vega. It is about the size of your hand held at arm’s length and is about six fists held upright and at arm’s length above due east at 11 p.m. For more information about the Kepler mission, go to

Sunday: Venus and Jupiter shine like two asymmetric headlights; low in the western sky at 10 p.m. Venus is the brighter of the two, on the left. At the same time, Saturn is two and a half fists above due south.

Monday: Hot enough for you? Don’t blame the Earth-Sun distance. Surprisingly, the overall temperature of the Earth is slightly higher in July, when the Earth is farthest from the Sun, than in January, when it is closest. That’s because in July, the Northern Hemisphere is tilted towards the Sun. (This is the real cause of the seasons.) The Northern Hemisphere has more land than the Southern Hemisphere. Thus, in July, the large amount of Northern Hemisphere land heats up the entire Earth about two degrees Celsius warmer than in January. In January, the watery Southern Hemisphere is tilted toward the Sun. But, water does not heat up as fast as land so the Earth is a few degrees cooler. The distance between the Earth and Sun is its greatest today, 152.1 million kilometers. This is called aphelion from the Greek prefix “apo” meaning “apart” and Helios, the Greek god of the Sun.

Tuesday: The nine-year wait is almost over. Next Tuesday morning at 4:49 PDT, the New Horizons mission will make its closest approach to Pluto. As the spacecraft approaches Pluto, the ever less distant images are causing astronomers to ask new questions. What are those equally spaces spots on the equator of Pluto? Why are Pluto and its largest Moon Charon so different in color? Is that really a giant crater on Pluto? For answers to these and other questions, many of which have not even been asked yet, go to While you are waiting, watch this NASA documentary about the mission: Pluto is in the constellation Sagittarius, one and a half fists above the southeast horizon at 11 p.m. It is too dim to be seen with anything smaller than a fairly large backyard telescope.

Wednesday: This morning’s last quarter Moon is in the constellation Pisces the fish.

Thursday: Look straight up at midnight. The head of Draco the dragon will be looking straight down on you. The brightest star in the head is called Eltanin. If you chose to wait a VERY long time, Eltanin will be the brightest star in the night sky. Currently 154 light years away, it is moving towards Earth and will be only 28 light years away in about 1.3 million years, claiming the title as brightest star.

Friday: Mercury peeks up above the northeast horizon at 4:30 a.m., just ahead of the rising Sun.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to

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