Douglas Scott
Professor
University of British Columbia
It remains a bunch of stars orbiting the centre of the galaxy in a stable manner. Unless it interacts with another galaxy.

Dr. Michael M. Davis
Astronomer
SETI Institute
For a long time, the gas and dust thrown out from the explosions will form into new stars, but we don't see much of that happening in elliptical galaxies at the present time. So my guess is that as the stars use up their nuclear fuel and go through their final stages of evolution, a large chunk of the star gets tied up in white dwarfs (very hot but inactive stellar remnants) that gradually cool off to invisibility. So the galaxy may possibly just disappear after a few more Hubble times (one Hubble time is the present age of the universe).

Yervant Terzian
Professor
Cornell University
Large objects become black holes, others neutron stars and white dwarfs. The nucleus of the galaxy may create a very massive black hole that will attract most other matter.

Mordecai-Mark Mac Low
Curator/Professor of Astrophysics
American Museum Natural History
It becomes very very dim. However, low-mass stars live for over a 100 billion years (ten times as long as the current age of the Universe, so this will take a while!

Astronomer*
The galaxy still has mass, but no light.

Andrew Liddle
Astronomer
University of Sussex, UK
I suppose it just fades away. Eventually the material will condense to the centre, perhaps forming a supermassive black hole.

Karen Vanlandingham
Assistant Professor
Columbia University's Biosphere 2 Center
The galaxy would become dark. Most of the stars are still there, they just don't shine anymore. They still have mass and, therefore, gravity, so they have an effect on one another as well as other masses (other galaxies, for example). We just wouldn't be able to see the galaxy any more.

Astronomer*
Gravitationally, the galaxy would still have an influence on other nearby galaxies since the matter in a star never goes away. It would become nearly invisible depending on how one defines a dead star. For stars with less mass than our sun, this would take many times the current age of the universe..

Eilat Glikman
Graduate Student
Columbia University
New stars are being born all the time! When stars die they shed lots of gas, either as a massive explosion known as a supernova or a more quiescent shedding of gas over time, into beautiful planetary nebulae. This shedding of gas provides the materials for new stars. And what is left over are the cores that were too dense to explode or be shed. The cores of these old stars are known as white dwarfs and neutron stars. These stars remain in a galaxy forever.

Professor*
In the absence of gas, it gets dark but it still exists and is then made of stellar remnants (white dwarfs, neutron stars and stellar-mass black holes). But the lowest mass stars live for hundreds of billions of years - much longer than the present age of the Universe - so the above will not happen for a long time.

However, many ellipticals contain a lot of gas that currently is very hot. Even if it does not cool before the stars die, it will cool afterward and make new stars. This will keep the galaxy visible for another long time.

If the galaxy can swallow gas that falls in from outside, the same thing will happen: new stars are likely to form.

So it will take a long time (much longer than the present age of the Universe) for ellipticals (or any other galaxies) to become completely dark.

Walter Harris
Astronomer
University of Wisconsin-Madison
The galaxy itself would still be there, but instead of bright stars, a collection of dead remnants (white dwarfs, neutron stars, and black holes). The matter is still there, but has been reorganized into a non-luminous form. For the record, this process would take a VERY long time. The faintest stars can burn for hundreds of billions of years, and star formation is still going on in most galaxies.

Graduate Student*
First of all, astronomers have never seen anything like this. Astronomers think that elliptical galaxies contain lots of small red stars that seem to last for a very long time while barely changing. Because they can last so long, the red stars in elliptical galaxies may last for a very long time.

However, even if all of the red dwarfs in an elliptical galaxy ran out of hydrogen for fuel, they would probably only change into red giants and then white dwarfs. White dwarfs also last for a very long time. They may run out energy eventually, but I'm not really certain what happens when they do or even if they can.

Ed Churchwell
Professor/Astronomer
University of Wisconsin
Good question. We have never seen such a galaxy so we don't really know the answer to this. However, it is likely that as the stars are converted to white dwarfs, neutron stars, and black holes these will all slowly loose all their thermal (heat) energy and they will become cold and black. So, I would postulate that the galaxy would become cold and dark and only visible through its gravitational interactions with other galaxies.

Don Brownlee
Astronomer
University of Washington
neutron stars, white dwarfs and black holes

Prof. Wayne G. Roberge
Theoretical Astrophysicist
Rensselaer Polytechnic Inst.
The stars become dark "black dwarfs" when they use up their nuclear fuel. The last stars to burn out are the lightest ones (red dwarfs, which use their fuel very slowly). The last red dwarfs will become black dwarfs in about 10**14 (ten to the power 14) years. After about 10**20 years, most of the black dwarfs will have been "kicked out" of the galaxy by chance encounters with other stars. Eventually, (after about 10**30 years) the stars left behind will coalesce into a black hole. You can read more about this in the August, 1998 issue of Sky and Telescope magazine.

Martin Duncan
Professor of Physics
Physics Department, Queen's University
The very low mass stars live for a very long time, so as the galaxy ages, mostly remnants like black holes, neutron stars, white dwarfs are left, together with faint dim red stars. Of course on very long timescales it might interact with one or more of its neighboring galaxies.

Steven Balbus
Astronomy Professor
University of Virginia
The stars evolve to stable "solids" known as white dwarfs, and the galaxy will eventually evaporate, but only after eons of time.

Professor Rex A. Saffer
Physicist, Astronomer, Educator
Dept. of Astronomy & Astrophysics, Villanova University
It is still there, but the stars (or what is left of them, like white dwarfs, neutron stars, and black holes) don't glow brightly anymore. The material is still there, but it is dark and cannot be seen in the kind of light we can detect with our eyes. Other effects, though, like the gravity of the matter, could still be detected by their effects on other objects like other nearby galaxies.

Bob Mathieu
Professor of Astronomy
Department of Astronomy, University of Wisconsin - Madison
When a star "dies" it simply runs out of fuel. The vast majority of stars turn into white dwarfs, which while very small in radius still have stellar masses. So they still respond to
gravity, and still continue to orbit in the galaxy. So when all the stars in an elliptical galaxy die, the galaxy will fade out but not really go away.

David Batuski
Astronomer
University of Maine
For a long time, it will just sit there getting darker, losing a few stars to space, then gradually it will collect into black holes.

Eric McKenzie
Graduate student
University of Florida
The mass is mostly still there, even though all the stars have gone out, so the galaxy will stick together for a long time, but it will be a burnt-out cinder. For questions about the long-term fate of the universe, I recommend Paul Davies' book The Last Three Minutes.

Astronomy Professor*
The galaxy consists of very old stars like white dwarfs, neutron stars and black holes, all of which will eventually run out of energy sources.

John Huchra
Astronomer/Professor
Harvard-Smithsonian
This takes a long time (100+ Billion years), and for a while you have a dark galaxy with
periodic flashes of light as the burned out husks of stars crash into each other. Eventually
the galaxy turns into one big black hole and then it evaporates.

*Respondents opted for anonymity and we respect their wishes.