'Dead' galaxies are not so dead after all

May 30, 2011
Individual young stars and star clusters in the 'dead' elliptical galaxy, Messier 105, detected using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). Messier 105 can be seen in the top, left corner, in an image from the Sloan Digital Sky Survey (SDSS; Data Release 8). The outlined region in the center of Messier 105 is expanded to reveal Hubble's unique view of the inner region of Messier 105, which is further expanded to unveil several individual young stars and star clusters (denoted by dashed circles; top, right). These signposts of recent star formation are unexpected in old, 'dead' galaxies. Data from HST's WFC3 and Advanced Camera for Surveys (ACS) were used in the creation of these HST images."

(PhysOrg.com) -- University of Michigan astronomers examined old galaxies and were surprised to discover that they are still making new stars. The results provide insights into how galaxies evolve with time.

U-M research fellow Alyson Ford and astronomy professor Joel Bregman are scheduled to present their findings May 31 at a meeting of the Canadian Astronomical Society in London, Ontario.

Using the 3 on the , they saw individual young stars and in four that are about 40 million light-years away. One light-year is about 5.9 trillion miles.

"Scientists thought these were dead galaxies that had finished making stars a long time ago," Ford said. "But we've shown that they are still alive and are forming stars at a fairly low level."

Galaxies generally come in two types: spiral galaxies, like our own Milky Way, and . The stars in spiral galaxies lie in a disk that also contains cold, , from which are regularly formed at a rate of about one Sun per year.

Stars in elliptical galaxies, on the other hand, are nearly all billions of years old. These galaxies contain stars that orbit every which way, like bees around a beehive. Ellipticals have little, if any, cold gas, and no star formation was known.

"Astronomers previously studied star formation by looking at all of the light from an at once, because we usually can't see individual stars," Ford said. "Our trick is to make sensitive ultraviolet images with the Hubble Space Telescope, which allows us to see individual stars."

The technique enabled the astronomers to observe star formation, even if it is as little as one Sun every 100,000 years.

Ford and Bregman are working to understand the stellar birth rate and likelihood of stars forming in groups within ellipticals. In the Milky Way, stars usually form in associations containing from tens to 100,000 stars. In elliptical galaxies, conditions are different because there is no disk of cold material to form stars.

"We were confused by some of the colors of objects in our images until we realized that they must be star clusters, so most of the star formation happens in associations," Ford said.

The team's breakthrough came when they observed Messier 105, a normal elliptical galaxy that is 34 million light-years away, in the constellation Leo. Though there had been no previous indication of star formation in Messier 105, Ford and Bregman saw a few bright, very blue stars, resembling a single star 10 to 20 times the mass of the Sun.

They also saw objects that aren't blue enough to be single stars, but instead are clusters of many stars. When accounting for these clusters, stars are forming in Messier 105 at an average rate of one Sun every 10,000 years, Ford and Bregman concluded. "This is not just a burst of star formation but a continuous process," Ford said.

These findings raise new mysteries, such as the origin of the gas that forms the .

"We're at the beginning of a new line of research, which is very exciting, but at times confusing," Bregman said. "We hope to follow up this discovery with new observations that will really give us insight into the process of in these 'dead' galaxies."

Explore further: POLARBEAR detects curls in the universe's oldest light

Related Stories

Antennae Galaxies

May 19, 2008

This image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. During the course of the collision, billions of stars will be formed. The brightest and most compact of these star ...

Colliding galaxies make love, not war

Oct 17, 2006

A new Hubble image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. As the two galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The ...

Baby booms and birth control in space

Sep 25, 2007

Stars in galaxies are a bit similar to people: during the first phase of their existence they grow rapidly, after which a stellar birth control occurs in most galaxies. Thanks to new observations from Dutch ...

Hubble Sees Star Cluster 'Infant Mortality'

Jan 10, 2007

Astronomers have long known that young or "open" star clusters must eventually disrupt and dissolve into the host galaxy. They simply don't have enough gravity to hold them together, unlike their much more ...

An abundance of small stars

Dec 10, 2010

(PhysOrg.com) -- Stars form from giant clouds of gas and dust in space, as the matter in these clouds comes together under the influence of gravity.

Survey Reveals Building Block Process For Biggest Galaxies

Apr 12, 2006

A new study of the universe's most massive galaxy clusters shows how mergers play a critical role in their evolution. Astronomers used the twin Gemini Observatory instruments in Hawaii and Chile, and the Hubble Space Telescope ...

Recommended for you

Big black holes can block new stars

1 hour ago

Massive black holes spewing out radio-frequency-emitting particles at near-light speed can block formation of new stars in aging galaxies, a study has found.

POLARBEAR seeks cosmic answers in microwave polarization

1 hour ago

An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, ...

New radio telescope ready to probe

4 hours ago

Whirring back and forth on a turning turret, the white, 40-foot dish evokes the aura of movies such as "Golden Eye" or "Contact," but the University of Arizona team of scientists and engineers that commissioned ...

Exomoons Could Be Abundant Sources Of Habitability

Oct 20, 2014

With about 4,000 planet candidates from the Kepler Space Telescope data to analyze so far, astronomers are busy trying to figure out questions about habitability. What size planet could host life? How far ...

Partial solar eclipse over the U.S. on Thursday, Oct. 23

Oct 17, 2014

People in most of the continental United States will be in the shadow of the Moon on Thursday afternoon, Oct. 23, as a partial solar eclipse sweeps across the Earth. For people looking through sun-safe filters, from Los Angeles, ...

User comments : 6

Adjust slider to filter visible comments by rank

Display comments: newest first

omatumr
2 / 5 (8) May 30, 2011
These findings raise new mysteries, such as the origin of the gas that forms the stars.


I suspect that the gaseous, photon-emitting, envelopes observed around other stars are like the Sun's photosphere:

Waste products of excited neutrons from the solar core that decay into hydrogen and glow "in the photosphere like a frosted light bulb."

"Neutron Repulsion", The APEIRON Journal, in press, 19 pages (2011)

http://arxiv.org/...2.1499v1

With kind regards,
Oliver K. Manuel
Tuxford
2 / 5 (4) May 31, 2011
Easy. Giant ellipticals likely producing new stars at high rate especially near their obscured cores. The huge core star at the galactic center producing and ejecting new matter at high rate to seed these new stars. This is the final stage of galactic evolution. Just a matter of time before this is acknowledged.
frajo
3 / 5 (2) Jun 04, 2011
While some people indulge in giving answers to unasked questions I prefer to ask unanswered questions.

Why are some galaxies called "old"? Usually to be old means to be born earlier than those who are not old. Consequently, an old galaxy should be a galaxy that has come into existence earlier in time than other, "newer", galaxies.
This scenario, however, doesn't fit quite well with the predominant lambda cold dark matter hypothesis according to which the first generation of galaxies has been seeded by primordial fluctuations and all galaxies thereafter are only products of collisions and mergers.
Tuxford
1.8 / 5 (5) Jun 21, 2011
Indeed, it is a continuous process of predominately OLD blue giants producing new matter in their cores in a continuous process. Still the grey 'black' hole at the core will still produce the vast majority of the new matter. New line of research? Just read LaViolette's 'SubQuantum Kinectics'. Why reinvent the wheel?

And now, galaxies either active or inactive:
http://www.physor...eep.html

omatumr
1 / 5 (4) Jun 21, 2011
Perhaps it is my sense of optimism, but I sense tonight that the very foundations of modern science may be strengthened by the rapidly crumbling story of CO2-induced global warming:

http://skepticals...sun-sun/
jsdarkdestruction
1 / 5 (1) Jul 20, 2011
or perhaps your lack of common sense.....