The interplay of energy and matter creates beautiful sights. Here on Earth, we enjoy rainbows, auroras, and sunsets and sunrises. But out in space, nature creates extraordinarily dazzling structures called nebulae that can span hundreds of light-years. Nebulae are probably the most beautiful objects out there.
While searching for young stars and their circumstellar disks, Hubble captured a classic reflection nebula.
A nebula starts with a cloud of interstellar dust. There are many clouds of dust out there in space, but it’s the proximity of a star that brings a nebula to life. The light from the star scatters through the cloud and reflects off of the gas, creating a beautiful display. Nebulae are often blue due to the way light scatters. Blue light, because of its wavelength, is more easily reflected from grains of dust.
In the early days of astronomy, astronomers weren’t certain what they saw when they spotted a nebula. The word nebula means ‘cloud’ or ‘fog’ in Latin, so early astronomers called anything that appeared cloud-like a nebula. They even called galaxies nebulae.
As time went on and telescopes and observations improved, they figured more things out. In 1912, American astronomer Vesto Slipher understood that light from a nearby star lights nebulae up rather than some intrinsic characteristic of the nebula itself.
IC 2631 is a reflection nebula about 500 light-years away in a giant star-forming region called the Chamaeleon Cloud Complex. A star named HD 97300 provides the light. HD 97300 is a young, massive star that hasn’t entered the Main Sequence yet. As a protostar, it hasn’t gathered enough mass to trigger the nuclear fusion that takes place in older stars. Instead, its light comes from radiation surface shocks. As gas falls into the young protostar, it creates shocks on its surface that radiate energy.
Hubble took this image of IC 2631 while it was looking for young stars and their protoplanetary disks. The disks consist of gas and dust, and each young star forms with one of these disks. The gas and dust are matter that wasn’t taken up by the star as it forms. Eventually, planets form from this leftover material.
There’s no visible protoplanetary disk around HD 97300. But there are other features in the image. Above the reflection nebula are two dark clouds called dark nebulae. They’re so dense that no starlight can pass through them. And they’re a clue to what might happen in the future.
Nebulae don’t last forever. Once the star matures and gathers more gas, it’ll enter the main sequence and begin fusing hydrogen in its core. Ironically, the star will be smaller then and not as bright. In a sense, the young star—called a T-Tauri star—is a more youthful, more brilliant version of its adult self. Eventually, the star won’t light the nebulae up so brightly.
But there’s a lot of gas and dust in the region, and other stars may form. If and when they do, they may light up the surrounding gas into another nebula.
But humanity may be long gone before that ever happens, if it does. So let’s enjoy the sights while we still can.