Hubble captures breathtaking picture of dark and light nebulae
Hubble has captured a stunning photo of a baby star in close proximity to both a light nebula and a dark nebula overlapping.
This photo might not be the most spectacular of the nebula photos take by the Hubble telescope over the years, but there is a lot more going on than a first glance by an untrained eye would indicate.
Just above the centre of the image, a bright star shines. Still in its infancy, the star -- located in the constellation of Perseus -- has not yet reached full growth. It is circled by accretion disc, nebular dust and gas being drawn in an orbital motion into the star by its gravity, feeding its growth. This stage of a star's growth typically lasts 10 million years.
Below the star -- classified a YSO, or young stellar object, and catchily named SSTC2D J033038.2+303212 -- is a white cloud shaped like a half-moon. This is a reflection nebula, so named because it is reflecting light from stars -- in this case, the nebula, called [B77] 63, is lit from within by the stars inside it. These include emission-line stars -- that is, a star whose spectrum displays emission lines -- EM* LkHA 326 and LZK 18.
But that dark space that creates the moon shape is not the border of the reflection nebula. It's actually another nebula -- a kind known as a dark nebula. These nebulae are so dense that they block the light coming from behind them, often looking like holes in other nebulae. They are actually relatively common, which is why astronomers rely on radio and infrared astronomy.
The innermost parts of dark nebulae are filled with sub-micrometre dust particles coated with frozen carbon monoxide and nitrogen. These dust particles scatter and absorb all light on visible wavelengths, and the internal temperature of a dark nebula is very low. This low temperature will gradually allow the dense matter inside the nebula to collapse under its own gravity, forming into a rotating disc -- a very young baby star, known as a protostar.
This particular dark nebula, called Dobashi 4173, looks like it has stars inside or behind it. In fact, we can't see anything behind Dobashi 4173 in this image: the stars that appear scattered over its dark surface are in front of the nebula, between Dobashi 4173 and Earth.