It鈥檚 hard to argue against the beauty of stars. The sight of light puncturing night鈥檚 cloak has prompted philosophical musings from many thinkers. Sir John Frederick William Herschel called stars 鈥溾�he land-marks of the universe.鈥� The Lion King鈥檚 Timon, in contrast, thought they were fireflies.
For Dal astrophysicist , they鈥檙e a key that unlocks celestial history.
For over ten years, Dr. Chapman and an international team of astrophysicists have worked to uncover how and when the universe鈥檚 stars and galaxies took shape.
鈥淭here has long been debate over the origins of stars in galaxies even larger than our own Milky Way,鈥� explains Dr. Chapman. 鈥淎re they born over long periods of time or in concentrated bursts?
鈥淏efore stars form there are just raw materials floating around, attracted by gravity,鈥� he says. 鈥淪omehow these materials come together to make stars, assembled together in galaxies.鈥�
Uncovering a 鈥渃osmic baby boom鈥�
The team鈥檚 new study suggests the first galaxies formed in much greater abundance and much earlier in the universe鈥檚 history than previously thought. Researchers looked far into space and found galaxies experiencing a sort of 鈥渃osmic baby boom,鈥� huge numbers of stars forming rapidly in a short period of time. They also found that, on average, these bursts of activity happened 12 billion years ago, a billion years earlier than previously thought.
The new international captured millimeter-wave light from 26 of the surveyed galaxies, which produce light at characteristic wavelengths due to large numbers of rotating carbon monoxide molecules. These wavelengths are stretched by the expansion of the universe over billions of years that it takes light to reach Earth. The team calculated the length of the light鈥檚 journey by measuring this stretch, and placed each galaxy at the right point in cosmic history: a celestial time map.
Master's student will follow up the new paper by scrutinizing the conditions of gas turning into stars and use the galaxies as beacons to probe the nature of the elusive dark matter in the intervening space.
Mapping cosmic history
The team鈥檚 findings will contribute to piecing together galactic history and revising scientific models of galactic formation. A long and complex process, modeling involves building, testing and revising to find a model that supports the evidence that researchers see through their telescopes. A successful model can be used trace the celestial past and understand the present.
Dr. Chapman鈥檚 group has been on a roll lately with research suggesting that current models of galactic formation are incomplete. His team鈥檚 articles have graced the cover of the top journal twice in the last three months. Dr. Chapman led the optical and infrared observations that built to this discovery, and his team鈥檚 identification of the foreground lenses and background galaxies, as well as measuring the distances to the lenses, were crucial to developing these more complex models.
鈥淭o construct a model, you begin with the most obvious and easy solution. If that model doesn鈥檛 fit with what鈥檚 actually happening, it must change,鈥� says Dr. Chapman. 鈥淐urrent models of galaxy formation don鈥檛 explain what our group is seeing, so something more complicated must be happening.鈥�
As Dr. Chapman continues his work, he reflects on the potential impacts of charting celestial history.
鈥淯nderstanding how galaxies formed will shape thinking on everything that comes after, including our place in the universe,鈥� he says. 鈥淭hat鈥檚 pretty cool.鈥�
For more information on Dr. Chapman鈥檚 research, visit .