This spectacular view of the Milky Way reveals a detailed map of hydrogen gas in and around our home galaxy.
Improving on earlier maps of its kind, the new atlas ― dubbed HI4PI ― reveals the fine details of the structures between stars for the first time, scientists from Germany and Australia said in a press statement.
“Tiny clouds become visible that appear to have fueled star formation in the Milky Way for billions of years,” stated Lister Staveley-Smith, from Australia’s International Centre for Radio Astronomy Research. “These objects are too dim and too small to be detected even in the other galaxies closest to us.”
The map is constructed from data collected by two enormous radio telescopes ― the 100-meter Max-Planck radio telescope in Germany and the 64-meter CSIRO radio telescope in Australia ― in more than a million individual observations.
Using varying colors, it reveals total hydrogen content and the gas’ velocity relative to the Earth. Hydrogen makes up most interstellar gas and is the building block of the Milky Way. The galaxy’s rotation determines the velocity of the gas ― which scientists use to construct a map.
Maps based on hydrogen data can show us details that visual maps can’t.
“Dust in our galaxy prevents us from seeing all the way into the center of the galaxy, and from seeing the spiral arms on the far side of the center,” said Jay Pasachoff, an astronomer at Williams College who wasn’t involved in the project. “Radio waves from hydrogen, however, penetrate the whole galaxy.”
“Hydrogen is the most basic element in the universe, so it is important to study it in as much detail as possible,” Pasachoff explained. “The new observations map the hydrogen visible all around the sky in unprecedented detail.”
The map will be an important reference for understanding how atomic gas is distributed in the Milky Way, said astronomer Mary Putman of Columbia University. “We can use it to study how our galaxy obtains new star formation fuel and how it blows out the old stuff from stellar explosions.”
Hydrogen is easy for radio telescopes to detect, but noise caused by human activity makes mapping the whole sky much more difficult, said Juergen Kerp, an astronomer from the University of Bonn in Germany.
“Radio ‘noise’ caused by mobile phones and broadcast stations pollute the faint emissions coming from stars and galaxies in the Universe,” Kerp stated. “So sophisticated computer algorithms have to be developed to clean each individual data point of this unwanted human interference.”
Astronomers exploring galaxies other than the Milky Way, too, can benefit from a more detailed view of the hydrogen that exists in and around the Milky Way.
“All observations we receive from the distant Universe have to pass through hydrogen in our own Milky Way,” stated Benjamin Winkel of the Max Planck Institute for Radio Astronomy. “The HI4PI data allows us to correct accurately for all these hydrogen clouds and clean the window we are watching through.”
Last month, data gathered the European Space Agency’s Gaia spacecraft produced another map of the Milky Way. Located 1 million miles from Earth, Gaia has been observing and mapping the stars for more than two years to produce a first-of-its-kind 3D atlas of a billion stars.
That means we only have at least 99 billion more stars to go.