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Tonight

Bright moon still close to Spica May 18

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The waxing gibbous moon has moved eastward in its orbit around Earth, but it’s still close to Spica, Virgo’s brightest star.

Bright moon close to Spica on May 17

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Tonight and tomorrow night – May 17 and 18, 2016 – as darkness falls, look for the bright waxing gibbous moon to shine close to Spica, the brightest star in the constellation Virgo the Maiden.

Upcoming Blue Moon near red Mars

Most Blue Moons are not blue in color.  This photo of a moon among fast-moving clouds was created using special filters. Image via EarthSky Facebook friend Jv Noriega.

Most Blue Moons are not blue in color. This photo of a moon among fast-moving clouds was created using special filters. Image via Jv Noriega.

The next Blue Moon will be on May 21, 2016. It’s a seasonal Blue Moon, the third of four full moons between the March equinox and the June solstice of 2016, and it’ll be near the red planet, Mars. Read about the various kinds of Blue Moons, and how often they occur, here.

How to see the legendary green flash

Green flash on upper part of sun, as seen by EarthSky Facebook friend Jim Grant in Ocean Beach, California.

Green flash on upper part of sun, as seen by EarthSky Facebook friend Jim Grant in Ocean Beach, California.

You can see green flashes with the eye, when sky conditions are just right, if you are looking toward a very clear and very distant horizon. That’s why those who see green flashes most often see them over a sea horizon. You also must be looking just at sunset, at the last moment before the sun disappears below the horizon. And you have to be careful not to look too soon. Wait until just the thinnest rim of the sun appears above the horizon. If you look too soon, the light of the sunset will dazzle (or damage) your eyes, and you’ll miss your green flash chance that day.

How to measure star distances

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One very distant star is Deneb. Why don’t astronomers know the exact distance to Deneb, and why are there different estimates for the star’s distance?

Moon and Jupiter on May 14

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As darkness falls on May 14, 2016, use the moon to find the king planet Jupiter. Watch for them. Really. They’ll be a sight to see in your sky on Saturday evening.

Moon and constellation Leo, May 13-15

Watch for the waxing moon to move eastward in front of the constellation Leo the Lion over the next several days. The green line depicts the ecliptic - the sun's yearly path, and the moon's monthly path, in front of the constellations of the Zodiac.

Watch for the waxing moon to move eastward in front of the constellation Leo the Lion over the next several days.

Tonight – May 13, 2016 – and for the next few evenings, as soon as darkness falls, look outside for the moon. On May 13, the moon is at or near its first quarter phase. The nearby point of light will be Regulus, brightest star in the constellation Leo the Lion.

Virgo? Here’s your constellation

Classical illustration of the constellation Virgo the Maiden, via constellationsofwords.com

Classical illustration of the constellation Virgo the Maiden, via constellationsofwords.com

The constellation Virgo the Maiden fully returns to sky at nightfall – with her feet planted on the eastern horizon – by late April and early May. Follow the links inside to learn how to find Virgo, and more about its place in science and history.

Jupiter can guide you to the Beehive

While the moon is still a thin crescent, use the dazzling planet Jupiter to locate the constellation Leo. An imaginary line from Jupiter through the bright star Regulus will enable you to locate the Beehive star cluster in the constellation Cancer. Binoculars transform this wispy cloud-like smudge of light into a sparkling array of stars.

Use the dazzling planet Jupiter to locate the constellation Leo. An imaginary line from Jupiter through the bright star Regulus will enable you to locate the Beehive star cluster in the constellation Cancer. Binoculars transform this wispy cloud-like smudge of light into a sparkling array of stars.

Tonight – May 12, 2016 – it’ll be hard to miss dazzling planet Jupiter. In fact, Jupiter is very prominent on these May, 2016, evenings – even on a moonlit night. Meanwhile, you’ll have difficulty seeing the constellation Cancer the Crab on this night, because it’s faint … and the moon shines right in front of it.

Arcturus cuts through galaxy’s disk

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Artist’s concept of the star Arcturus

Arcturus, a red giant, looks orange to the eye. It’s the brightest star on the northern half of Earth’s sky dome. Arcturus is especially noteworthy for its large proper motion, or sideways motion across our sky. Only Alpha Centauri – our sun’s nearest neighbor among the stars – has a higher proper motion among the first-magnitude, or bright, stars in the stellar neighborhood. What can the proper motion of Arcturus be telling us? Follow the links inside to learn more about this fascinating star.