When it comes to the distant universe, even the keen vision of NASA’s Hubble Space Telescope can only go so far. Teasing out finer details requires clever thinking, and a little help from a cosmic alignment with a gravitational lens.
By applying a new computational analysis to a galaxy magnified by a gravitational lens, astronomers have obtained images 10 times sharper than what Hubble could achieve on its own. The results show an edge-on disk galaxy, known as SDSS J1110+6459, studded with brilliant patches of newly formed stars.
The findings appear in a paper published in The Astrophysical Journal Letters (“Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation Down to 30 pc Scales“), and two additional papers published in The Astrophysical Journal on July 10 (“Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110=6459. I. Lens Modeling and Source Reconstruction” and “Star Formation at z=2.481 in the Lensed Galaxy SDSS J1110+6459. II. What is Missed at the Normal Resolution of the Hubble Space Telescope?”
“When we saw the reconstructed image, we said ‘Wow, it looks like fireworks are going off everywhere,’” says astronomer Jane Rigby of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, a co-author on the papers.
Adds UConn astronomer Kate Whitaker, assistant professor of physics and another co-author on each of the three papers, “The cosmic explosions forming new stars across this galaxy are happening on surprisingly small scales. Previously it was thought that these distant, early galaxies formed new stars in giant supersized star clusters, but we lacked the angular resolution to know this for sure. These observations challenge that commonly held idea.”
The galaxy in question is so far away that we see it as it appeared 11 billion years ago, only 2.7 billion years after the big bang. It’s one of more than 70 studied as part of the Sloan Giant Arcs Survey, an imaging survey that searched 240 galaxy clusters to find new examples of gravitational lensing.
The gravity of a giant cluster of galaxies between the target galaxy and Earth distorts the more distant galaxy’s light, stretching it into an arc and also magnifying it almost 30 times. The team had to develop special computer code to remove the distortions caused by the gravitational lens, and reveal the disk galaxy as it would normally appear.
The resulting reconstructed image revealed two dozen clumps of newborn stars, each spanning about 200 to 300 light-years. This contradicted theories suggesting that star-forming regions in the distant, early universe were much larger, 3,000 light-years or more in size.
“There are star-forming knots as far down in size as we can see,” says doctoral student Traci Johnson of the University of Michigan, lead author of two of the three papers describing the research.
Without the magnification boost of the gravitational lens, Johnson adds, the disk galaxy would appear perfectly smooth and unremarkable to Hubble. This would give astronomers a very different picture of where stars are forming.
While Hubble highlighted new stars within the lensed galaxy, NASA’s James Webb Space Telescope will uncover older, redder stars that formed even earlier in the galaxy’s history. It will also peer through any obscuring dust within the galaxy.
“With James Webb,” says Rigby, “we’ll be able to tell you what happened in this galaxy in the past, and what we missed with Hubble because of dust.”
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.