How long does a supernova last?

 


The other night, I thought I discovered a supernova in NGC 3621. When I checked online for supernova discoveries, there were none reported for galaxy NGC 3621. Weird. I've always assumed that any supernova that I come across will have already been discovered by the pro's. Wow! Maybe my discovery is legit! Or maybe, I thought, all of the pro teams hadn't yet reported their discoveries.

But the following morning, when there were still no reports of supernova discoveries in NGC 3621, I began to have doubts. I continued to check in all day long and there were still no reports for NGC 3621. Weirder. 

I haven't yet figured out how to report a possible supernova, but I sent an email to David Bishop of the Rochester Astronomy website. He said there weren't any reports of a supernova in NGC 3621, but that there was a supernova in that galaxy last year: 2024ggi.

Hmmm. That jogged my memory. Back in April of 2024, supernova 2024ggi was so bright that it caught the attention of Sky & Telescope editors who sent out a report in an email newsletter. Ah! Yes. Now I remember that from last spring! So, I looked at my images from 2024 and indeed, the position of the supernova in NGC 3621 then is exactly where it is in my images from the other night.

When I joined the supernova hunting sport in 2016, my interest was merely to experience the thrill of discovery. I didn't care if I wasn't the official discoverer of a supernova. It seemed impossible to me that, in a world of 8 billion people, I could be the first person to spot a supernova. All of the other many thousands of amateur and professional supernova hunters out there with bigger and better telescopes than mine would surely beat me to the punch. Right? 

Therefore, the only way for me to experience the thrill of discovery was to try and avoid looking at any news regarding supernova discoveries. My practice has been to stay away from the Rochester Astronomy website until I come across something that could be a supernova. I don't want spoilers. It's kind of like knowing that you're going to miss an upcoming NFL game, so you set your DVR to record it and you don't want to know the outcome until you watch your recording. That way, you can watch the game just as if it were happening live. After all, why watch a football game if you already know who's going to win? But nowadays it can be difficult to avoid seeing news reports of football scores.

Last April, after the discovery of supernova 2024ggi, Sky & Telescope reported it in an emailed newsletter. I remember my regrets over that headline because NGC 3621 is a galaxy that's on my 11-hour list for supernova searches. They spoiled it for me! I wished I hadn't looked at that email! I took some images of 2024ggi in NGC 3621, but I couldn't claim its supernova as one of my "discoveries" because Sky & Telescope tipped me off to it.

That was nine months ago! My last pictures of the supernova in NGC 3621 were from May of 2024. Not long after that, the Realm of the Galaxies at 11 - 13 hours of Right Ascension was lost to the glare of the sun and I forgot all about NGC 3621.

So, the other night when my sidereal clock was showing 10 o'clock, I decided to shoot galaxies at 11 hours of Right Ascension. NGC 3621 is on that list. And after shooting it, I noticed a dim star that wasn't in my reference image. Hmmm. My first thought was to check for asteroids in the vicinity and there were none. Must be a supernova! But when I checked the Rochester Astronomy website, there were no discoveries reported in NGC 3621.

Like I said, I don't want to get spoilers about current supernovae, so I try not to spend much time looking around on the Rochester Astronomy site. Without paying attention to any of its contents, I did a Ctrl+F to see if there were any hits on 3621. There were none. I didn't scroll down and see how far back the list went. If I had, I would have noted that it only went back as far as September 2024! I should have clicked on a link to the previous page to go back farther. I just didn't think I needed to.

From my experience of taking pictures of them, supernovae remain visible for about 6 months or so. But it depends on the galaxy. The farther away a galaxy is, the fainter its supernovae will be, and it follows, then, that for the more distant galaxies, their supernovae may disappear from my images in less than 6 months. NGC 3621 is a rather small galaxy, and thus pretty far away, I assumed. I wouldn't expect to find a supernova in it that was discovered more than 6 months ago. But I was wrong!

The truth is supernova 2024ggi is still visible! I had completely forgotten about 2024ggi until last night when I shot NGC 3621 for the first time since May of 2024 and found a star that wasn't in my reference image.

David Bishop's email jogged my memory. If I hadn't sent him an email, I wouldn't have remembered last May's email from Sky & Telescope and taking pictures of NGC 3621 with a supernova in it. So, I have to wonder, "If I were a younger man, would I have remembered that experience after nine months?"

The famous visual supernova hunter, Rev. Robert O. Evans from Australia (look him up on Wikipedia), did all of his nightly supernova searches from memory. He had memorized the appearance of about 1500 galaxies, that is, how they looked in his telescope eyepiece. Each night, armed with only his memory, he aimed his telescope at some of his target galaxies and inspected them for new stars. Using this method, he discovered or co-discovered more than 30 supernovae throughout the 1980's and 1990's. 

I cannot do that! I haven't memorized the appearance of all the galaxies in my targets lists. I made over 9,000 galaxy comparisons in 2024, and I don't remember what all of those galaxies looked like! Perhaps a handful of them, yes. But I can't even remember all of the NGC numbers that are in my comparable (to Evans') list of about 1500 galaxies. In fact, I think I made my 22nd supernova discovery in December of 2024, but I am not certain of that date. And I cannot tell you for certain which NGC galaxy it was. I think it was NGC 681. But I'd have to look at my notes to be sure. I made five supernova discoveries in 2024, and I can't rattle off from the top of my head all of their respective NGC numbers.

Does that make me normal? Or should I be worried about my failing memory?

Maybe I am only making excuses, but I would say that the internet, PC's, and smartphones have allowed us to free our minds of cluttered memories. I don't need to remember anything because I can Google it or search Wikipedia for it, whatever it is, any time I want. Before we had PC's and the internet, we relied on our memories much more than we do now. If we couldn't remember something, it was painful to go and find that thing we couldn't remember, in a library or on a bookshelf in our homes. It was best to keep as much as possible in our heads.

I was reminded again of how quickly I now forget about things when I received the March 2025 issue of Sky & Telescope in the mail the other day. On the cover was a beautiful picture of Comet Tsuchinshan-ATLAS taken in October of 2024. Wow. The printed version of Sky & Telescope has always been 3 months behind. Normally, an astronomical event in October would take till December for us to read about it on the pages of Sky & Telescope. So why it took until the March 2025 issue for Comet Tsuchinshan-ATLAS to make the cover is already beyond me! But that doesn't matter. What does matter is that when I saw that cover photo, I had to admit that I had already completely forgotten about Comet Tsuchinshan-ATLAS! 

The odd part for me is that I don't think I would have forgotten about a comet like that so quickly in the old days, before the internet. We amateur astronomers in the 1980's wouldn't get to see pictures of comets unless we took them ourselves or we subscribed to an astronomical magazine that specialized in those things. There might be one story about it on a brief segment of the TV evening news, but if we missed that episode, we wouldn't see it anywhere else. So, if we even knew about a comet like Tsuchinshan-ATLAS, we looked forward to being able to see pictures and reader reports in an upcoming issue of Sky & Telescope. 

These days, we are bombarded with news about celestial events in the media. We're so sick and tired of seeing "Bright Comet to Light up the Skies" or "Comet Amazes Amateur Astronomers Around the World" headlines on the internet that these spectacular visitors to the inner solar system come and go with a yawn. Is that why I forgot about it? I can only hope so!

But whether I am a victim of the information age or just an old guy with a failing memory, I still find it astonishing that a supernova can remain visible in my backyard telescope for nine months! If I can't remember a comet from last October, then surely it follows that I would not remember a supernova from last May! Especially a supernova that I did not "discover" myself but merely read about in the news. And the reason this one lasted so long is that NGC 3621 turns out to be a fairly close galaxy to us at 22 million light years. Supernovae are essentially "standard candles" in the universe. The closer they are to us, the brighter they are. SN2024ggi was the closest supernova to earth since the supernova in galaxy M 51 back in May of 2023. Wait. You don't remember that one? You're scaring me!

Anyway, below is an interesting perspective of the supernova in NGC 3621. The animated GIF is comprised of three images I took of the galaxy. The first one was taken on January 6, 2024, before the supernova could be seen. The second image was taken on May 2, 2024, at nearly maximum brightness, after I read about it in Sky & Telescope. And the third image was from the other night, when I "discovered" SN2024ggi's fading light again for the first time!



Comments

Post a Comment

Popular posts from this blog

The life of a supernova hunter

Image
  Supernova in galaxy NGC 2146 I found a supernova in NGC 2146 last night. No, I was not "the discoverer" of the supernova. That would be the Japanese astronomer Koichi Itagaki. He discovered it 5 days earlier. But I didn't know it. I came across it on my own during my nightly search for supernovae in the distant galaxies. Supernova hunting has been my hobby since 2016, and supernova 2024abfl is the 21st supernova I've come across. You can look up supernovae on Wikipedia, so I won't waste your time by describing them here. What I would like to talk about, however, is the sport of supernova hunting.  Supernova hunting falls under the umbrella of backyard astronomy. If you were to purchase a telescope to get a closer look at the stars and planets, there are a number of astronomical activities you might eventually become interested in. Like most people, you'll probably be disappointed in the dull-gray eyepiece views of nebulae and galaxies, after seeing brilliant...
Read more

My first photograph of Pluto

Image
The year was 1987. I had been a backyard astronomer since 1980. During those 7 years, I felt like I had made good progress in the hobby. I was on my 4th telescope, a Meade 8-inch Schmidt-Cassegrain. I had tracked down nearly half of the Messier objects. I had seen the moons of Jupiter and the rings of Saturn. I was practiced at the art of astrophotography with color negative film, having shot a lunar eclipse in 1982, Halley's Comet in 1985 and 1986, and numerous deep-sky objects at the prime focus of my 8-inch f/5 Newtonian reflector. So, when I received the May issue of Astronomy magazine in 1987, and saw the article on page 100, titled "Where to Find Pluto[:] Spring and Summer 1987," I felt ready to accept the challenge to take a photo of the most distant planet in the solar system.  To be honest, before reading that article, I had never given any serious thought to hunting down Pluto. I didn't know much about it. Nobody did. I knew that it wouldn't look like m...
Read more

The Herschel 2500

Image
  H27-4, "The Ghost of Jupiter" In the final decades of the 1700's, the German-British astronomer William Herschel and his sister Caroline conducted a survey of the heavens. Together they discovered and produced a list of 2500 star clusters and nebulae that they published in three separate catalogs. Night after night, using a telescope of 18.7 inches in aperture and 20 feet in length, William, making his discoveries at the telescope eyepiece in the garden, called out the positions and descriptions of his celestial objects to his sister through an open window of their house, and she wrote down all the details by candlelight. It was a colossal effort that took them 19 years to complete, and meanwhile, William continued to build telescopes and conduct other scientific experiments in the daylight hours.  You can read all about the Herschels on Wikipedia, so I needn't repeat any more of their story here. However, in modern times, their 2500-object survey still manages to a...
Read more