Featured Research

from universities, journals, and other organizations

'Wimpy' dwarf fossil galaxy reveals new facts about early universe

Date:
May 1, 2014
Source:
Massachusetts Institute of Technology
Summary:
Out on the edge of the universe, 75,000 light years from us, a galaxy known as Segue 1 has some unusual properties: it is the faintest galaxy ever detected. It is very small, containing only about 1,000 stars. And it has a rare chemical composition, with vanishingly small amounts of metallic elements present.

The Magellan Telescopes at Las Campanas Observatory, Chile, where some of the new research on the Segue 1 galaxy was conducted.
Credit: Anna Frebel

Out on the edge of the universe, 75,000 light years from us, a galaxy known as Segue 1 has some unusual properties: It is the faintest galaxy ever detected. It is very small, containing only about 1,000 stars. And it has a rare chemical composition, with vanishingly small amounts of metallic elements present.

Related Articles


Now a team of scientists, including an MIT astronomer, has analyzed that chemical composition and come away with new insights into the evolution of galaxies in the early stages of our universe -- or, in this case, into a striking lack of evolution in Segue 1. Commonly, stars form from gas clouds and then burn up as supernova explosions after about a billion years, spewing more of the elements that are the basis for a new generation of star formation.

Not Segue 1: In contrast to all other galaxies, as the new analysis shows, it appears that Segue 1's process of star formation halted at what would normally be an early stage of a galaxy's development.

"It's chemically quite primitive," says Anna Frebel, an assistant professor of physics at MIT, and the lead author of a new paper detailing the new findings about Segue 1. "This indicates the galaxy never made that many stars in the first place. It is really wimpy. This galaxy tried to become a big galaxy, but it failed."

But precisely because it has stayed in the same state, Segue 1 offers valuable information about the conditions of the universe in its early phases after the Big Bang.

"It tells us how galaxies get started," Frebel says. "It's really adding another dimension to stellar archaeology, where we look back in time to study the era of the first star and first galaxy formation."

Metal-poor stars: a telltale sign

The paper, "Segue 1: An Unevolved Fossil Galaxy from the Early Universe," has just been published by Astrophysical Journal. Along with Frebel, the co-authors of the paper are Joshua D. Simon, an astronomer with the Observatories of the Carnegie Institution, in Pasadena, Calif., and Evan N. Kirby, an astronomer at the University of California at Irvine.

The analysis uses new data taken by the Magellan telescopes in Chile, as well as data from the Keck Observatory in Hawaii, pertaining to six red giant stars in Segue 1, the brightest ones in that galaxy. The astronomers are able to determine which elements are present in the stars because each element has a unique signature that becomes detectable in the telescope data.

In particular, Segue 1 has stars that are distinctively poor in metal content. All of the elements in Segue 1 that are heavier than helium appear to have derived either from just one supernova explosion, or perhaps a few such explosions, which occurred relatively soon after the galaxy's formation. Then Segue 1 effectively shut down, in evolutionary terms, because it lost its gas due to the explosions, and stopped making new stars.

"It just didn't have enough gas, and couldn't collect enough gas to grow bigger and make stars, and as a consequence of that, make more of the heavy elements," Frebel says. Indeed, a run-of-the-mill galaxy will often contain 1 million stars; Segue 1 contains only about 1,000.

The astronomers also found telling evidence in the lack of so-called "neutron-capture elements" -- those found in the bottom half of the periodic table, which are created in intermediate-mass stars. But in Segue 1, Frebel notes, "The neutron-capture elements in this galaxy are the lowest levels ever found." This, again, indicates a lack of repeated star formation.

Indeed, Segue 1's static chemical makeup even sets it apart from other small galaxies that astronomers have found and analyzed.

"It is very different than these other regular dwarf-type galaxies that had full chemical evolution," Frebel says. "Those are just mini-galaxies, whereas [Segue 1 is] truncated. It doesn't show much evolution and just sits there."

"We would like to find more"

Dwarf galaxies, astronomical modeling has found, appear to form building blocks for larger galaxies such as the Milky Way. The chemical analysis of Segue 1 sheds new light on the nature of those building blocks, as Frebel notes.

Indeed, other astronomers suggest that the study of galaxies such as Segue 1 is a vital part of progress in the field. Volker Bromm, a professor of astronomy at the University of Texas, says the new paper is "very nice and important," and "substantiates the idea" that analyzing faint dwarf galaxies produces new insight into the universe's development.

As Bromm points out, when it comes to the chemical composition of early stars, any search for clues among stars closer to us in the Milky Way can be problematic; most such stars have had "a very complex assembly and enrichment history, where many generations of supernovae contributed to the abundance patterns [of elements] seen in those stars." Dwarf galaxy stars do not come with that problem.

The findings on Segue 1 also indicate that there may be a greater diversity of evolutionary pathways among galaxies in the early universe than had been thought. However, because it is only one example, Frebel is reluctant to make broad assertions.

"We would really need to find more of these systems," she notes. "Or, if we never find another one [like Segue 1], it would tell us how rare it is that galaxies fail in their evolution. We just don't know at this stage because this is the first of its kind."

Frebel's work often focuses on analyzing the chemical composition of unusual stars closer to us. However, she says she would like to continue this kind of analysis for any other galaxies like Segue 1 that astronomers may find. That process could take a while; she acknowledges that any such future discoveries will require "patience, and a little luck."


Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Peter Dizikes. Note: Materials may be edited for content and length.


Journal Reference:

  1. Anna Frebel, Joshua D. Simon, Evan N. Kirby. SEGUE 1: AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE. The Astrophysical Journal, 2014; 786 (1): 74 DOI: 10.1088/0004-637X/786/1/74

Cite This Page:

Massachusetts Institute of Technology. "'Wimpy' dwarf fossil galaxy reveals new facts about early universe." ScienceDaily. ScienceDaily, 1 May 2014. <www.sciencedaily.com/releases/2014/05/140501101135.htm>.
Massachusetts Institute of Technology. (2014, May 1). 'Wimpy' dwarf fossil galaxy reveals new facts about early universe. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2014/05/140501101135.htm
Massachusetts Institute of Technology. "'Wimpy' dwarf fossil galaxy reveals new facts about early universe." ScienceDaily. www.sciencedaily.com/releases/2014/05/140501101135.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Space & Time News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Spokesman: 'NORAD Ready to Track Santa'

Spokesman: 'NORAD Ready to Track Santa'

AP (Dec. 19, 2014) Pentagon spokesman Rear Adm. John Kirby said that NORAD is ready to track Santa Claus as he delivers gifts next week. Speaking tongue-in-cheek, he said if Santa drops anything off his sleigh, "we've got destroyers out there to pick them up." (Dec. 19) Video provided by AP
Powered by NewsLook.com
NASA's Planet-Finding Kepler Mission Isn't Over After All

NASA's Planet-Finding Kepler Mission Isn't Over After All

Newsy (Dec. 18, 2014) More than a year after NASA declared the Kepler spacecraft broken beyond repair, scientists have figured out how to continue getting useful data. Video provided by Newsy
Powered by NewsLook.com
Rover Finds More Clues About Possible Life On Mars

Rover Finds More Clues About Possible Life On Mars

Newsy (Dec. 17, 2014) NASA's Curiosity rover detected methane on Mars and organic compounds on the surface, but it doesn't quite prove there was life ... yet. Video provided by Newsy
Powered by NewsLook.com
Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Evidence of Life on Mars? NASA Rover Finds Methane, Organic Chemicals

Reuters - US Online Video (Dec. 16, 2014) NASA's Mars Curiosity rover finds methane in the Martian atmosphere and organic chemicals in the planet's soil, the latest hint that Mars was once suitable for microbial life. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

More Coverage


Nearby Galaxy Is a 'fossil' From the Early Universe

May 1, 2014 Scientists analyzed the chemical elements in the faintest known galaxy, called Segue 1, and determined that it is effectively a fossil galaxy left over from the early universe. Stars form from gas ... read more

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins