Enjoying EarthSky? Subscribe.

159,554 subscribers and counting ...

How do fireworks get their colors?

Photo credit: Jeff Golden

Photo credit: Jeff Golden

If you’re celebrating the 4th of July by attending a fireworks display, maybe you’ll look up and wonder: What creates those red, orange, yellow, green, blue and purple colors exploding in the night sky?

Stars’ spiral arms cradle baby planets

Astronomer Alan Boss' theoretical model of a protoplanetary disk around a young star.  Notice the spiral structure. Image via Carnegie Institution for Science.

A protoplanetary disk around a young star, from a new theoretical model by astronomer Alan Boss. Notice the spiral structure extending outward from the central star. Image via Carnegie Institution for Science.

A new study from the Carnegie Institution for Science in Washington D.C. offers a potential solution to the question of how small rocky planets like our Earth come to be. A puzzle relates to how dust grains in a disk around a newly forming star avoid being dragged into the star before enough of the grains stick together to have strong-enough gravity to begin pulling in more grains … and ultimately grow into planets.

Star of the week: Antares is Heart of the Scorpion

Red star Antares, right, and nearby star cluster M4 via StargazerBob.com@aol.com

Red star Antares, right, and nearby star cluster M4 via StargazerBob.com@aol.com

Bright reddish Antares – also known as Alpha Scorpii – is easy to spot on a summer night. It is the brightest star – and distinctly reddish in color – in the fishhook-shaped pattern of stars known as the constellation Scorpius the Scorpion. Follow the links inside to learn more about this wonderful star.

Find M4, a globular cluster by the Scorpion’s heart

Messier 4 or M4 from European Southern Observatory.

Messier 4 or M4 from European Southern Observatory.

At nightfall, look in your southern sky for the bright ruddy star that is called the Scorpion’s Heart – Antares, the brightest star in the constellation Scorpius. Antares is always up on summer evenings. It’s a bright red star known for twinkling rapidly. If you have binoculars, sweep for an object near Antares on the sky’s dome. This object is called M4, and it’s a globular star cluster located just one degree to the west of Antares.

Mercury and more before dawn

Mercury, Aldebaran, Pleiades on June 30, 2015 by Ken Christison.

Planet Mercury, star Aldebaran, Pleiades star cluster on June 30 by Ken Christison in Conway, North Carolina.

Ken Christison caught Mercury in the east before dawn this week. He couldn’t see it with the eye that day, but you might see it, if you look. Details inside.

Blue Moon of July 2015 and future Blue Moons

Image credit: Tim Geers

Image credit: Tim Geers

Image credit: Tim Geers

The first of two July 2015 full moons falls today, on July 2. The second full moon of the month comes on July 31, 2015, and by popular acclaim, this full moon is known as a blue moon. Read about the blue moon and the 19-year Metonic cycle inside . . .

Every nineteen years, the phases of the moon recur on or near the same calendar dates. This is the Metonic cycle. Therefore, nineteen years from now, in 2034, we’ll again have two full moons in July 2034 and another blue moon on July 31, 2034.

First of two July full moons on July 1

Full moon over Rillings Hills near Colorado Springs, Colorado by Forrest Boutin Photography.

Last month’s full moon – June 2, 2015 – near Colorado Springs, Colorado by Forrest Boutin Photography.

July 2015 has two full moons. That’s somewhat unusual. Most months only have one. But in cycles of 19 years, or 228 calendar months, seven to eight calendar months will always have two full moons. In other words, there’s a month with two full moons every two to three years. When it happens, the second one is popularly called a Blue Moon.

Countdown to Pluto!

Image credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute

Image credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute

New Horizons gets ‘all clear’ for Pluto flyby, only 2 weeks away! Newest images of Pluto and Charon. Plus … methane detected on Pluto.

Are those sinkholes on Rosetta’s comet?

This close-up image shows the most active pit, known as Seth_01, observed on the surface of comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft. A new study suggests that this pit and others like it could be sinkholes, formed by a surface collapse process similar to the way these features form on Earth. Image via Vincent et al., Nature Publishing Group

Close-up of pit on comet 67P/Churyumov-Gerasimenko. This is the most active pit, known as Seth_01. A new study suggests this pit and others like it could be sinkholes. Image via Rosetta spacecraft, Vincent et al., Nature Publishing Group

Scientists announced this week that deep, almost perfectly circular pits on the surface of Comet 67P/Churyumov-Gerasimenko may be sinkholes. Sinkholes on Earth happen when a subsurface cavern collapses. On the comet, the caverns may be created by ices turning to gas, as the comet nears the sun.

July 2015 guide to the five visible planets

Skywatcher, by Predrag Agatonovic.

Skywatcher, by Predrag Agatonovic.

Venus and Jupiter are spectacular now, and they’ll stay close together throughout July. Check out what July’s planets will do, here.