Researchers use Hubble Telescope to look at star formations
The key to understanding the birth of our galaxy and stars is suspected to lie far, far away in the stars that are old enough to tell many stories of their own. Some of these stars are billions of years old — almost as old as the universe itself.
University researchers are investigating different parts of the universe using the Hubble Telescope in the Hubble Telescope Ultraviolet Ultra-Deep Field to further understand star formation in galaxies similar to ours.
“We’re studying galaxies in the particular regions of sky in the southern hemisphere that’s been studied with the Hubble Space Telescope to detect galaxies in the distant universe,” said Peter Kurczynski, a research assistant in the Department of Physics and Astronomy.
They have discovered galaxies at a redshift of near three, he said. These redshift values estimate the age of the galaxy to be about 11 billion years old, only 2 billion years after the Big Bang.
“Ultraviolet observations see the light from young, massive, hot stars,” said Harry Teplitz, the principal investigator of the UVUDF project. “Understanding star formation helps us to understand how galaxies evolved into the ones we see today.”
The space between distant galaxies and the earth absorbs light that is in the ultraviolet wavelength, he said. They use the colors the galaxies emit to estimate the distance of the galaxy from our planet.
“This is called the Lyman break technique, which uses the colors the galaxies emit,” said Eric Gawiser, assistant professor in the Department of Physics and Astronomy. “We get different sets of galaxies and get to study the evolution in time in this early epoch of the universe.”
If the team sees it in a blue waveband and it drops out to an ultraviolet waveband, they can use that information to infer how far away that galaxy is, Kurczynski said. The shorter the wavelength, the farther away the object is expected to be.
“One person’s nuisance is another person’s science. In this case, when you’re working with visible light you don’t want there to be dust because it blocks light,” he said.
Galaxies emit both visible light and microwaves, which they use to get data on radiation that tells them how fast galaxies are forming stars and how long ago that happened, he said.
The team observes some galaxies where stars form dense clumps, Teplitz said. These stars migrate together to form larger structures within the galaxy.
“What makes these galaxies stand apart is that they’re generally very blue, but at certain parts of the spectrum they’d drop red,” Gawiser said. “There are blue galaxies in the universe, there are red galaxies in the universe, but these are galaxies that are blue all the way across, but then suddenly look red.”
This is because they are so far away the hydrogen between them and the earth is absorbing their light, making them look red, he said. The Lyman break method takes advantage of this.
“It works because Hydrogen atoms between us and the galaxy absorb much of the light from hot stars. Very little light is seen at shorter wavelengths,” said Teplitz, a staff scientist in California Institute of Technology.
Until the UVUDF project, there had been very little ultraviolet data taken on the ultra-deep field, he said.
“One of the things that we’d like to study in these galaxies that we’re able to study is their dust content,” Kurczynski said.
It is significant in scientists’ overall understanding of star formation to understand dust itself, he said. Dust obscures about half of the starlight in the universe.
“Dust affects galaxies [like] dust affects something like the sunset that you see on earth,” he said. “As the sun gets lower on the horizon and goes through a layer of dust, it makes the sun look red-orange. The light from a galaxy becomes red the same way.”
Before light reaches the Earth from stars, it has to pass through dust in the galaxy to get out, he said.
“In order to measure the dust in galaxies, we have to measure the light from these galaxies in a whole different bunch of wavebands put together and get an overall picture of a spectrum of light that’s emitted,” he said.
The ones that are really blue have no dust, the ones that are somewhat blue have some dust and every once in a while they look a little red because they have a lot of dust in one place, Gawiser said.
“They don’t assume how much dust a galaxy will have, we actually measure the dust empirically and see how it affects the color,” he said.
As dust absorbs the starlight, it heats up to negative 279 degrees Fahrenheit, Kurczynski said.
This is nonetheless detectable on earth because although that dust is very cold, it is still giving off some heat, he said.
“Time is very useful to us because then telescopes become time machines,” Gawiser said. “I could have a nearby sample of galaxies to study today, one from 100 millions years ago, one I can study from billion years ago and so on.”
The galaxies they’re discovering in the UVUDF project are very dim, and extremely far away, he said.
“As we look out into the universe, we discover how vast and an amazing place it is,” Kurczynski said. “It’s a testament to human creativity and ingenuity and hard work that we’re able to learn so much about the universe from what are fundamentally very faint signals.”