Dear Friends,
An explosion that began just about a week ago continues to pour out energy at approximately ten thousand million million (10 to the 16th power) times the output of our sun. Luckily for us it is not near enough to vaporize us. In fact, it is a million million times as far from us as the sun is, so it is only a perfectly safe, faint point of light. This is a newly discovered supernova – exploding star – in the Fireworks Galaxy (also known as NGC 6946), about 22 million light years away from our own Milky Way Galaxy.
This exploding star, now known as SN 2017eaw, is what is known as a Type II supernova. That is, it was probably a red giant star at least 10 times as massive as our sun that eventually lost its ability to produce nuclear fusion, leading to sudden collapse under its own massive gravitation, raising it’s core temperature to 10,000 times the sun’s core temperature, resulting in an unimaginably immense explosion where bits of the star are moving at up to 1/3 the speed of light. In destroying itself the star brightens immensely in a matter of seconds, then gradually fades over months and years. This supernova was discovered by Patrick Wiggins, a Utah amateur astronomer who dedicates many hours to searching for these “new stars.”
A supernova like this occurs in our own galaxy about once every 100 years. Although the Fireworks Galaxy has only about half as many stars as The Milky Way Galaxy, this is the
tenth supernova explosion observed in this galaxy in the past century – more than in any other galaxy.
Fritz Kleinhans, a good friend and life member of the Silver Lake Astronomical Society, alerted me to this event. So I dug through the Lookout Observatory archival images to find a pre- supernova image of the galaxy to show you first. This is a composite from several different nights of imaging several years ago from the dark skies of Lookout Observatory. It is the result of 3 and ¾ hours of total exposure. This spiral galaxy shows the typical yellow of older stars in the center, blue of the hot, younger stars in the spiral arms, and red in the hydrogen-rich regions of active star formation.
The second picture was taken two nights ago from my backyard in heavily light-polluted Albany, CA, because I couldn’t get up to the observatory. Although it is a 3-hour exposure, it had to be taken through a special filter, and the quality is considerably worse. However, if you study the two images together, you will see they are virtually identical except for a fairly bright star that is completely absent in the first picture. (I have indicated it with the two green tick marks.) This is the supernova, now a 12th magnitude star visible in medium- to large-size telescopes. I find this exciting since most things in the astronomical universe change at slower than a glacial pace. My wife Anitra had a different view: “It’s just one more little dot among hundreds!” You can choose your own viewpoint, but.
Keep looking up,
Carter Mehl, (sometime) resident astronomer,
Lookout Observatory
