Searching for Extragalactic Supernovae

I'll soon be doing an extragalactic supernova search, monitoring a small group of 5 or 6 spiral galaxies, similar in structure, to our Milky Way, barred-spiral galaxy - in the Virgo galaxy cluster.

The Virgo Cluster of galaxies is (around) 30-50 million light-years from the "Local Group" - the Milky Way's home, galactic cluster. The Virgo galactic cluster contains a spiral galaxy, M66, in the constellation Leo. It is some 35+ million light-years distant.

Back on 11 February 1989, at around 02:15am EST, Insight Observatory Managing Member and Project Developer, Michael Petrasko, and I, independently co-discovered a supernova (SN1989b), within one of the outer spiral arms of M66 (Michael, was the actual discoverer; I just "looked"!).

The Local Group and other galaxy cluster groups. Graphic by Dale Alan Bryant.

Supernova events within any given galaxy are estimated to occur only two or three times in a century. I'll see if I can refine that estimate, somewhat, over the course of a few months of nightly or bi-nightly photographic time-exposures of the group, using one of Insight Observatory's remote astrographs (photographic telescope) - ATEO-1, or ATEO-2A. The instruments are situated in the western New Mexico region, respectively - some of the clearest and darkest skies in the world.

Typically, an SN burst is so energetic that its brilliance, temporarily, outshines the combined light of all of the billions of stars within a given galaxy. Any SN event will stand out as a tiny, bright, dot, superimposed against the overall, dim, oval blur of light of the main body of the galaxy. It is during a supernova burst that the heavy elements of our universe are forged (iron, nickel, and other heavy metals). From there, the energy of the blast disperses the elemental metals into the surrounding space including any nearby molecular clouds which ultimately condense and become planetary systems (such was the case in our "Solar" system).

This is the history of the metallic content of Earth's mantle and crust, and, its solid iron core.

Dale Alan Bryant
Senior Contributing Science Writer

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Fore!

Though I've never played a game of golf in my life - I used to frequent the Woods Hole Golf Club's course, at Woods Hole, Mass. - in the middle of the night, that is. You see, I'm an astronomer/astrobiologist.

On any given clear night, fellow astronomer Mike Petrasko, and I, used to drive our car and light pickup, equipped with my 8-inch, and Mike's 6-inch, 50-inch long, 70-inch high Newtonian reflector telescopes, up onto a fairway at the golf course, in Woods Hole, to about the course's center.

Woods Hole Golf Course, Woods Hole, MA.

There, we set up the telescopes and connected their motorized clock drives, to our vehicle batteries, with cables and alligator clips; this was necessary so that, as the Earth rotates during the night - and the stars drift slowly across the sky, the telescopes, when aimed at an object, could counter that motion and follow along, defeating any tendency for the object to drift, in the telescope's field of view.

During the winter months, we'd usually arrive at the golf course just before midnight, set up the equipment, and prepare to spend several hours in sub-freezing temperatures - many times, in the single digits. We'd break down the equipment and leave just after dawn. This happened three or four nights a week - regardless of our regular work schedules, of course.

Meade 826C Newtonian  8" Telescope.

We chose that particular observing site because the sky there is relatively dark, free of light pollution, to the north, and absolutely black in the south, over Vineyard Sound. Mike and I had been monitoring a list of galaxies, for possible, extra-galactic, supernovae outbursts.

Extragalactic supernovae are exploding stars, located in galaxies beyond our own Milky Way galaxy, the closest being several thousand light-years away. These outbursts occur, on average, only once every hundred years, or so, in any given galaxy - including our Milky Way. We actually discovered one, one morning, in February of 1989. It is known, today, as SN1989b and is located in the spiral galaxy, M66, in the constellation Leo, the lion. I remember that night very well... - it was 4°F!

One morning, around 4:00am, a local police officer drove up onto the course in his cruiser, with spotlights glaring, and parked next to my truck. In a mock tone of extreme concern, he asked me, what kind of weapon it was that I was using, and what it was pointed at! I told him that, that was highly-classified information and that I could not give him a meaningful answer. He enjoyed the comeback.

After we had explained that we were astronomers, with the SUNSEARCH program, of the Harvard-Smithsonian Observatory in Cambridge, and that the unusual-looking instruments in question were astronomical telescopes, he pointed out that we were not supposed to be there, without express permission from the owner; we could only agree. But, he said, since our activity was benign - and possibly even useful, and since the ground was frozen solid (being February, our tires didn't mess with them, normally, immaculate grass) - that it would be OK, though, he suggested we try golfing there some time, instead.

Some of the finest - and loneliest - hours of my life were spent on that golf course, scanning the universe with my telescope and witnessing, first-hand, many of its mysteries, free of charge. It is where, one night, for the first time, with the use of my Skalnate-Pleso Observatory star atlas, I had experienced a keen awareness of my bearings and my relative position on the Earth, and its position within the solar system, and the solar system's position within the Milky Way galaxy. At that moment, I simply felt like, for the first time, I knew exactly where I was.

It was there, throughout the year, that I did several Mars and Saturn observing sessions, and was witness to a global sandstorm, one night on the red planet. I also made note of any changes, over time, in growth or shrinkage in Mars' south polar ice cap, as Mars progressed through its seasons throughout the Martian year. I've seen Saturn's rings, both in an edge-on aspect and wide open. The interval between those two extremes is about three decades long. Yup, I've been around folks.

Maybe, someday, I'll take that officer's suggestion and play a game of golf there... after I learn how to play, of course... “Fore!”

Dale Alan Bryant
Senior Contributing Science Writer

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Astronomy Questions and Answers

I'd like to thank Mike Petrasko for inviting me here to share some of my experiences in astronomy, which, more often than not, included Mike himself! I'm an Amateur Astronomer with something like 35 years of experience being bent over the eyepiece of a telescope (and boy is my neck sore!) Mike and I have had, probably some of the most interesting, sometimes bizarre (but usually entertaining) experiences in the history of observational astronomy. I will share them with you here as I recall them...

M66 Imaged by Adam Block.

After having read my recent article on supernova SN1989B, my brother (not an astronomer!), texted me the following questions one night, included here with my answers:

Q: In your article, you talked about a star going supernova. If there was a planet with life orbiting the star, how much warning would their scientists have to save their civilization?

A: Scientists would know about the star’s condition long before it went supernova and would have had time to prepare—that is if there were actually any other place to go. However, after the explosion, the ejected material from the star would be traveling toward the planet at 10% of the speed of light and would reach the planet within just a few hours. The planet would be vaporized instantly.

Q: So, what could happen to our Sun to cause us a problem here on Earth?

A: The Sun has done nothing out of the ordinary in its entire history. It is a very stable star. It has an 11-year sunspot and solar flare cycle which occasionally causes us electrical problems here on Earth, but that’s about it. Its internal nuclear forces are able to balance its gravitational forces which will not allow it to collapse in on itself and then explode.

Q: So the Sun will never go supernova?

A: No, the Sun is not massive enough. Only stars 3 solar masses and more can go supernova. A supernova explodes after it uses up its nuclear fuel and collapses under its own weight. What’s left, if it has enough mass, will collapse even further to the point of no return and become a black hole—with a gravitational pull so strong that not even light can escape. If the star doesn’t have enough mass to become a black hole, it may become a sphere of carbon under pressure. We all know what happens to carbon under extreme pressure—it becomes a diamond! Yes, there are stars out there that are pure diamonds. "Up above the world so high, Like a diamond in the sky” was more accurate than anybody knew, at the time! But if it continues to collapse, it will become a neutron star; literally, a ball of neutrons packed so tightly together that a teaspoonful would weigh millions of tons!

Q: So, just what will happen to the Sun?

A: The Sun, being a rather small star (specifically, a type G2 Yellow Dwarf), will begin to swell as it ages and move off the Main Sequence of stellar evolution to become a red giant star—a very slow process so no surprises here. Its edges will reach out to almost the orbit of the Earth. This is not good news for anybody sticking around as the Earth will be burned to a cinder! But there will be plenty of time to prepare; it will not happen for another 4.5 billion years.

Q: How are we related to all of this, supernovae I mean?

A: Well, the heavy elements such as iron, nickel, copper, magnesium, zinc, beryllium and the rest of the metals that make up terrestrial planets like Earth, and even our own bodies, were forged in the interiors of supernovae. That’s the only place in the universe these elements are created, along with minerals and silicates that become rock, sand, and dust. They travel across space together to cool and condense into planets - and people! So, the atoms in our bodies once existed in the interiors of stars! To quote the late Cornell University professor of astronomy, Carl Sagan - “We are all star stuff.”

Dale Alan Bryant
Senior Contributing Science Writer

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