Ophiuchus: colors of the night sky: In most of planet Earth’s nigh sky right now, a very colorful region can be observed to the delight of everyone. Do you know this vibrant region of our home galaxy?
This interesting area is composed of bright colored stars, star clusters, reflection and emission nebulae. It really is something straight out of a sci-fi fantasy but it does exist, and you don’t need a very powerful telescope to see it! This complex, also called the Rho Ophiuchi cloud complex- is located in the constellation Ophiuchus and at the tail end of the constellation Scorpius. Although its colors cannot be picked up with the naked eye, you will spot Ophiuchus right away in the night sky, provided you have a nice flat view south on a clear moonless summer night (if you are in the Northern Hemisphere that is). For people living above 55° North of latitude, it will only be visible for a short window from February till May. After that time, the nights will be too bright to see it and the constellation, which is very low on the horizon, quickly disappears. Ophiuchus is located right ‘east’ of the milkyway core. At mid-northern latitudes, it rises in the southeast and sets in the southwest. Actually the bright yellow star Antares is the first thing you will see rise, and usually is the sign that the whole milky way core is on the rise!
In the lower northern hemisphere and southern hemisphere, Antares rises very high in the sky, enabling you to spot it very easily. Through binoculars, you can see quite stunning details. It’s even better through a telescope, as you can start seeing the dark dust lanes that accompany this mind-boggling region. However to capture the colors in the best way possible, you will need a sensor. Ideally, you need a DSLR, a tracker that enables your camera to follow the stars as they move across the sky, and a good fast sharp lens. As you expose for a longer time, you will start seeing yellow, brown, black, red, pink and blue colors appear between the stars!
Antares, one of the brightest stars of our night sky
Antares, also called alpha Scorpii, is a prominent star in Scorpius (the Scorpion), a constellation that is visible in the southern night sky of most locations in the Northern Hemisphere. Antares is about 604 light-years from Earth. It is 700 times the sun’s diameter, large enough to engulf the orbit of Mars, if the solar system were centered on it. Antares is a red supergiant star that is nearing the end of its life. Once there is no more fuel left to burn, the star will collapse and explode into a supernova. The star is among the 20 brightest visible in Earth’s night sky, although its brightness varies. Amateur observers have pegged its apparent magnitude between 0.88 and 1.16. Additionally, it has a small neighbor star (Antares B) that looks bluish-white and is sometimes called “a little spark of glittering emerald.” Despite its size, the overall density of Antares is less than one-millionth that of the sun. Antares is also relatively cool as stars go, only about 6,500 degrees Fahrenheit (3,593 degrees Celsius) compared to 10,000 F (5,500 C) for the photosphere of the sun. The star’s low temperature accounts for its ruddy color. The word “Antares” means “anti-Ares” or “anti-Mars,” likely because astronomers in ancient times thought the reddish star looked similar to the red planet.
Antares, Mars, Saturn, meteor and milky way core over the Alps
The colors of Ophiuchus
When you take a long exposure of the Rho Ophiuchi cloud complex, you will be amazed at the colors. It’s truly mesmerizing, as if it was only possible in a dream. But it really exists! The colors come from nebulae, these clouds of dust and gas that are the leftovers of previously exploded stars. There are two major kinds of nebulae in the complex: reflection and emission nebulae. The former don’t produce any light but reflect it from nearby stars. For example, the yellow-looking cloud is only yellow because it mirrors the light from the red giant Antares. In the same way, the dark dust lanes called Barnard 44 are only visible because of the bright environment. They would be hardly visible if the billions of stars didn’t illuminate them. The blue nebula on top of the complex is also a on of them and reflects the light of R scorpii star. On the other hand, the red/pinkish nebula (Ced 103) is an emission nebula. It’s also a star nursery where stars are born. Young stars emit a lot of UV light at the start of their lives, which in turn excites atoms and molecules of surrounding gas clouds. It causes the latter to glow a certain color depending on their constituents! Here, hydrogen glows red (H-alpha).
A video first of its kind!
It usually takes a long and difficult astrophotography technique to be able to show the colors of Antares. Thus far it’s only been possible on stills and that’s why it’s never really been shown on film before. I had this crazy idea of taking up the challenge of doing it anyway. I wanted to try and time-lapse the complex in a certain way that would optimize the signal-to-noise ratio and make the colors appear without too much grain. Instead of hours of integration, could I possible do it in only 15 seconds on a series of stills put back to back? It really wasn’t a piece of cake though. I had to buy the best astro-gear on the market, travel to dark enough locations where Ophiuchus would be high enough in the sky. I also had to spend hours perfecting a workflow from finding the best camera settings to post-processing. I used an astro-modded 6D and various fast lenses ranging from 14mm to 135mm to get the best out of each single frame of the timelapse and reveal the beautiful colors. I also used a tracker (Vixen Polarie) and a light-Pollution filter to also increase colors and contrasts! It’s the first ever attempt at a time-lapse of this object with this amount of details and a foregrounds.