Category Archives: universe

Death of the Universe

GIF at 11!

This composite picture shows how a typical galaxy appears at different wavelengths in the GAMA survey. This huge project has measured the energy output of more than 200 000 galaxies and represents the most comprehensive assessment of the energy output of the nearby Universe. The results confirm that the energy produced in a section of the Universe today is only about half what it was two billion years ago and find that this fading is occurring across all wavelengths from the ultraviolet to the far infrared. Courtesy: CRAR/GAMA and ESO
This composite picture shows how a typical galaxy appears at different wavelengths in the GAMA survey. This huge project has measured the energy output of more than 200 000 galaxies and represents the most comprehensive assessment of the energy output of the nearby Universe. The results confirm that the energy produced in a section of the Universe today is only about half what it was two billion years ago and find that this fading is occurring across all wavelengths from the ultraviolet to the far infrared. Courtesy: CRAR/GAMA and ESO

While I was out learning how to manipulate the universe inside the Digistar 5 last week, a news story broke about how the universe is slowly dying. Astronomers are doing a survey of galaxies of all shapes and sizes in 21 wavelengths of light, and have discovered that the energy being produced by stars, nebulae, and galaxies in a surveyed portion of the cosmos is about half of what it was just two billion years ago.

Yes, you read that right: the energy emitted is MUCH less than it was in the past. (For reference, the universe is 13.7 billion years old, or thereabouts.) The team looked at more than 200,000 galaxies to come to their conclusion that the universe is settling back for long, quiet old age as it slowly fades away.

The news that the universe is riding off into the sunset (sort of), is not new news. It’s been on scientists’ minds since the 1990s, but this recent survey is the most detailed look at just how much it is fading and how widespread the dimming down is across the cosmos.

How Long Will It Take?

So, now that we know the universe is dying, the big question is, how long will it take to completely cool and die? The best answer I could find among several places that discuss the end-game of the universe puts it at quintillions of years from now. Between now and then, all the stars will eventually die, dimming out the galaxies. The clouds of gas and dust that make up stars (and planets) will be used up, leaving no building blocks for new stars. Some theorists suggest that there will be a time when only black holes will dominate the universe, making the end state of the cosmos a truly Dark Era.

So, the slowly cooling universe will outlive us all, and likely exist long after all in the cosmos is gone (or evolved to something else). But eventually, the cosmos will be cold and dead. It’s a tough scenario to imagine. But, it makes sense; all things must eventually cool down, slow down, and come to a halt. Even the universe.

The story of our dying universe reminds me of a great science fiction story by Isaac Asimov, called The Last Question. It explores this very idea, but through the eyes of a cosmic computer that continues to ask the same question throughout cosmic time: “How can the net amount of entropy of the universe be massively decreased?” (In other words, can the second law of thermodynamics be reversed? (It states that entropy always increases. Read more about it here.)

I won’t give away the answer, so go find the story for yourself and enjoy!  Dr. Asimov created a wonderful thought experiment that goes right along with our newly expanded view of the universe’s impending (and far in the future) death.

Survey the Universe?

How It Has Been Done with SDSS

The Perseus Cluster, as seen through the eyes of the Sloan Digital Sky Survey. Courtesy Robert Lupton. Click to biggify.

The universe is a strange and wonderful place.  How do I know this when I haven’t explored it all? When astronomers are still searching out the distant reaches and early history of the cosmos?  I know it from the work done by scientists using such observatories as the Hubble Space Telescope, the Spitzer Space Telescope, the Wilkinson Microwave Anisotropy Probe, and the phalanx of ground-based observatories such as the Subaru Telescope, the Gemini Observatory, the European Southern  Observatory, and many, many others.  Quite significantly, I know it from the results of a sky survey that revolutionized our view of the universe–mostly of the galaxies, galaxy clusters, and quasars — but also by looking at bodies in our own solar system.  That survey was the Sloan Digital Sky Survey, which has carried out deep multi-color surveys of more than a quarter of the sky. Data from its first surveys were used to create three-dimensional maps of nearly a billion galaxies and more than 120,000 quasars. It’s now in a new program of observations called SDSSIII that will continue until the year 2014.

All this work has been done using a 2.5-meter telescope on a mountain in southern New Mexico. A single telescope!  It’s an amazing and ongoing accomplishment.

The Sloan began operation in 2005, and I often wondered about the people who put it together. Certainly I’d heard plenty about the survey at meetings, and had met some of the Sloan planners. But, as with the Hubble Space Telescope, I really didn’t know much of the history of the project when I first signed on to work with an instrument team back in grad school.  HST piqued my curiosity, and so in 1992 and 1995, I worked on a book with co-author Jack Brandt (a former team lead for the Goddard High Resolution Spectrograph on HST, and now at the University of New Mexico) called Hubble Vision. I also did a planetarium/fulldome show called Hubble Vision about HST’s accomplishments, which I periodically update.

Working on those projects gave me a lot of insight into the people who make such instruments work, and their hopes and dreams for the outcome of their astronomy work.  Hubble’s history is replete with individuals who designed the instruments, solved the problems, recognized the errors of spherical aberration, and who have made the many,  many accomplishments possible.  Some of those same folks have been involved with the Sloan Digital Sky Survey, too.

I just finished reading a book about the Sloan Digital Sky Survey (SDSS, for short) and the folks who made it a reality. The book, called A Grand and Bold Thing, by Ann Finkbeiner, gives us a look not just at Sloan and its accomplishments, but at the dream it sprang from — beginning with the spiral bound notebooks of astronomer Jim Gunn (who first brought the idea up at a meeting in Tucson in 1987), and the further refinements of the first planning documents and taking us to the observations made by this project.  At one level,  the book does what Jack and I tried to do for Hubble: give readers a look at the PEOPLE behind the instruments and accomplishments.  Ann’s writing is clear and wonderful, and she really lets the reader see the history and growth of SDSS quite clearly, through the eyes of the astronomers who made it happen.  These are REAL people who sweated over the development and installation of SDSS, and their accomplishment is considerable.

Along the way, we also learn about the universe that SDSS (and all its observational siblings) has revealed to astronomers.  SDSS’s contributions to understanding the large-scale structure of the universe are considerably one of the most important achievements in astronomy.  Without the data that SDSS, and sibling surveys such as the 2DF and 6DF observations, astronomers might still literally be groping in the dark for an understanding of how matter is distributed throughout the universe.

Finkbeiner weaves in the story of thediscovery of the structure of the cosmos as she tells the story of the SDSS.  For me, entwining together the story of scientific discovery with the tale of the people who enabled the SDSS’s odyssey of discovery is a heady brew. You should drink it in for yourself!