The Biggest Explosions of All

I’ve spent a lot of time in my astronomy career pointing telescopes at some of the biggest explosions of all—type 1a supernovae. This kind of supernova starts with a white dwarf star and another star orbiting each other. White dwarfs are very dense stars at the end of their lives. The only objects more dense are neutron stars and black holes. The white dwarf’s gravity draws material off the companion star until it reaches critical mass and the whole thing explodes. One such star that I had the chance to observe in detail in was Supernova 2011fe in the galaxy M101. Here’s an image from the Mayall 4-meter at Kitt Peak, one of the telescopes I used to observe this object. The supernova is the bright blue star outshining everything else in the upper right-hand part of the image.

Image by T.A. Rector (University of Alaska Anchorage), H. Schweiker & S. Pakzad NOAO/AURA/NSF

These cosmic explosions are pretty interesting in their own right. Our own star is expected to end its life as a white dwarf and these explosions give us a glimpse at the hearts of these stellar corpses. These explosions are also one of the ways heavy elements formed in the cores of stars get distributed out into the universe. Supernova 2011fe was, in fact, one of the closest Type 1a supernovae we’ve ever observed. We caught the explosion soon after it happened, watched the supernova brighten to maximum, then start to fade away.

Type 1a supernovae also have another useful property. Because white dwarfs have a fairly uniform mass, the brightness of the explosion is also uniform. So, if every Type 1a supernova observed were placed at the same distance away from you, they would all, more or less, be the same brightness. This means that by measuring the apparent brightness of the supernova, you can figure out how far away it is. This is a bit of an oversimplification, but there are ways to calibrate that information based on the how fast the explosion brightens and fades.

Back in the 1990s, an astronomer named Saul Perlmutter was granted target-of-opportunity time on Kitt Peak telescopes. In this case, it meant if a type 1a supernova went off, he could ask the telescope to point to it and take an image and calibration data. He and his colleagues hoped to get distances to as many galaxies as possible. I helped acquire some of that data which was combined with a lot of other data from a lot of telescopes to provide evidence that the expansion of the universe is accelerating. Perlmutter would go on to share a Nobel prize with Adam Riess and Brian P. Schmidt for this work.

This is one of those discoveries that shows some of the true fun of science. We learned that the expansion of the universe is accelerating, but that raises an even bigger question. Why is it accelerating? Typically that’s attributed to something called “Dark Energy.” This attribution isn’t meant to be an answer in itself. It’s meant to be a placeholder. It’s “Dark” energy because we don’t know precisely what kind of energy it really is, or even if it’s energy at all! Later this year, a new instrument called DESI will be installed on the Mayall 4-meter which will endeavor to get answers to some of those questions. But like all good science, I expect a veritable explosion of new questions raised for every answer we’re able to get.

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On Turning 50

Over the weekend, while at TusCon in Tucson, Arizona, I celebrated my fiftieth birthday. It’s one of those points in life where I find myself looking back to see where I’ve been as well as looking forward to see where I’m going.

david-at-50

In my first fifty years, I’ve written and published nine novels, eighty-four short stories, and fifty-four poems. I’ve edited three anthologies, plus two magazines for ten years each. I contributed to the commissioning of the WIYN 3.5-meter telescope and the NMSU 1-meter telescope. I’m co-discoverer of two variable stars and I helped take data that contributed to the discovery of dark energy. Most of all, I’m proud to be the father of two incredible young ladies, one in high school, the other in college, who have a wide range of talents in such areas as computer science and mathematics.

Looking ahead, my tenth novel, The Astronomer’s Crypt, is nearing release. I have two anthologies in the publication queue: Kepler’s Cowboys and Maximum Velocity: The Best of the Full-Throttle Space Tales. I have four short stories accepted and awaiting publication. Beyond that, I’m in the early phases of writing a new novel and I have a “fix-up” novel a little over half completed. Plus I have story treatments for four more novels. Presuming no major funding shifts, I expect to be involved in commissioning two new instruments at Kitt Peak in the coming years.

As I reach fifty, I’m arguably in the best health I ever have been. The arthritis that plagued me for years is in remission and I regularly take long walks through my neighborhood. Nevertheless, one specter looms over me. My dad was only fifty-two when he died suddenly of a heart attack. In the plus column, my doctor is helping me watch my heart health and both of my brothers have now outlived my dad by over a decade. I have no immediate reason to fear for my imminent demise. Nevertheless, I find myself grieving for how truly short my dad’s life was cut and watching my health has taken on a new urgency.

In short, as I turn fifty, I feel proud of what I’ve accomplished. My regrets are minimal. While there are some harsh words and rash actions I’d take back if I could and some friends I’ve lost touch with over the years, it’s hard to say I’d have a better life if I’d taken a different path. I have several exciting things to look forward to in the coming months and years, plus plans and goals for the years beyond that.

Thanks to my readers for sharing some of this fifty-year journey with me. I look forward to sharing the coming years with you as well.