When we look at stars in the night sky, what we see isn’t always their true color or brightness.
Cosmic dust clouds spread across our galaxy can make distant objects appear redder and dimmer, like looking through a dirty window.
To help astronomers get clearer views of space, scientists have created the most detailed 3D map of cosmic dust ever made.
This groundbreaking work was done by Xiangyu Zhang, a Ph.D. student at the Max Planck Institute for Astronomy (MPIA), and his advisor Gregory Green, a research group leader at MPIA.
Their map, published in Science, gives astronomers a much better understanding of how dust affects what we see in space.
Why does cosmic dust matter?
Dust in space isn’t just an obstacle for astronomers. It plays a key role in star and planet formation.
Stars are born inside giant clouds of gas and dust, which also help form planets. In fact, much of the material that makes up planets—including Earth—comes from cosmic dust grains.
To study distant stars accurately, astronomers need to understand how much dust is in between and how it affects the light we see.
Dust absorbs and scatters blue light more than red light, a process known as “reddening”. It also makes objects appear fainter, an effect called “extinction”. Scientists can study how different wavelengths of light are affected by dust using something called an extinction curve.
How did scientists create the map?
Zhang and Green used data from the European Space Agency’s (ESA) Gaia mission, which measured the properties of over a billion stars. They focused on 130 million stars with reliable data to analyze how dust affected their light.
However, Gaia’s data provides only low-resolution information. To improve accuracy, the researchers combined it with high-resolution data from the LAMOST survey in China. This extra data helped them determine the true properties of stars, such as their temperature and brightness, so they could separate the effects of dust from the actual characteristics of the stars.
Using advanced artificial intelligence (AI) techniques, they trained a neural network to model the dust’s effect on starlight. By applying this model to the Gaia data, they were able to map out the 3D structure of dust across the Milky Way like never before.
Surprising discoveries about cosmic dust
Not only did this research create the best dust map yet, but it also revealed unexpected properties of interstellar dust clouds. Scientists had believed that in denser dust clouds, the extinction curve would become flatter, meaning dust would affect all wavelengths of light more evenly. However, Zhang and Green found the opposite—in some areas, dust absorbs shorter wavelengths (blue light) even more strongly than expected.
They believe this might be due to the growth of polycyclic aromatic hydrocarbons (PAHs), complex molecules that are common in space. These molecules are important because they may have played a role in the origins of life. The team is already planning follow-up observations to explore this exciting possibility.
A clearer view of the universe
This 3D dust map will help astronomers see space more clearly and make more precise observations of distant stars and galaxies. It could also improve our understanding of how dust contributes to the formation of planets and possibly even life itself.
By removing the “dirty window” effect caused by dust, scientists are bringing us one step closer to a clearer and more accurate picture of the universe.
Source: Max Planck Society.
