I hope many of you saw auroras (northern lights) last night! I briefly saw the strongest steady red glow I myself have ever observed, visible even amid street lights and my neighbors’ house lights.
The skies, shown only slightly brighter than to the naked eye, as seen at 8pm Boston time. Credit: Matt Strassler
Then, after a break as some clouds rolled in, we were graced with a few hours of mostly diffuse green glow with patches of dim but distinct red that would come and go. All these colors were visible with the naked eye, albeit much less bright than shown in photos. It was quite a storm, not as violently active as the one earlier this year, but very persistent.
The storm lasted all night, though the auroras varied greatly in brightness. Data from https://www.swpc.noaa.gov/
I also tried to find Comet A3 just after sunset, but failed, even with the help of binoculars. Apparently the brief spike in its brightness, due to “forward scattering” as it passed between us and the Sun, may have died off too quickly, leaving it impossible to see in early twilight. It will become dimmer day by day, but it will also be visible later each evening, and at some point should become easy to see in dark skies. Let me know when you first observe it!
A powerful solar flare (an explosion on the Sun) about 36 hours ago created a large and fast coronal mass ejection (a cloud of subatomic particles heading away from the Sun) that is due to arrive at Earth in the next few hours (it will show up less than an hour before it arrives as chaos in this data.)UPDATE: IT HAS ARRIVED; IF IT’S DARK WHERE YOU ARE, GO LOOK. That could mean problems for the electrical grid. It could also mean strong auroras (northern and southern lights) far from the poles. The timing, if correctly predicted, is such that Asia and Europe may have the best chances, but the auroras could potentially last until it is dark in the Americas too.
Also, just after sunset tonight, we may with difficulty be able to see Comet A3 (short for Comet C/2023 A3 Tsuchinshan-ATLAS ). The comet is bright — some reports give it a brightness comparable to the planet Venus, although more diffuse — but so is twilight. UPDATE: I HAVE BEEN WARNED THAT THE RAPID BRIGHTNING PERIOD, DUE TO A LIGHT SCATTERING EFFECT, MAY ALREADY BE OVER. IF SO, THE STATEMENTS HERE MAY BE TOO OPTIMISTIC. The comet is roughly ten Sun-widths above and slightly to the right of the Sun, and should be visible 15-30 minutes after sunset if you have a low and mostly cloudless horizon. Best bet is to bring binoculars and scan the sky; you’ll notice it much more easily, even if it is visible to the naked eye.
Each day following, the comet will be higher in the sky at sunset, making it more visible in late twilight, but it will also become intrinsically dimmer. Experts seem to disagree about when it will be at its best, but this weekend should be good, if not before.
Added 5pm NYC time : Here’s what the data looked like showing the arrival of the coronal mass ejection, a few hours ago, at the ACE satellite, which gives us about an hour’s warning here on Earth:
Added 5pm NYC time: Here’s what the data looks like showing an ongoing geomagnetic storm and likely auroras; warning, the data is delayed 3 hours, so it’s not showing you what’s happening right now. “UTC” is 5 hours ahead of New York (i.e. Eastern) time, one hour behind Central European time.
A busy news week: a Nobel prize, another chance of auroras, and… a comet. It’s probably not the comet of the century, but comets like this one show up only about once every ten years. This one has already been visible in early morning skies. This week it enters our evening skies, and will likely be a lovely sight after dark for the rest of October.
Thursday, Friday and Saturday this week, immediately after sunset and just to the right and above the Sun, comet A3 MAY be at its most spectacular. BE READY! You will need a low and rather flat horizon, and you have less than an hour to see it before it sets, too.
Day by day, the comet will move up and to the left, beginning at the Sun’s right. Look there once the Sun is significantly below the true horizon and the sky has darkened a bit.
Later in the month it will be visible longer into the evening, but much less bright.
In fact, it’s already here. Oh yes, it seems that 2024 may not just be the year of a terrific solar eclipse and spectacular outbursts of northern lights (and maybe, just maybe, a nova.) In morning twilight, if you live in the right latitudes, an ever-brightening comet can apparently be spotted right now. I haven’t seen it yet, but I’m hoping to get a chance.
Nothing in cometary life is guaranteed; comets can fall apart unexpectedly, or fail to brighten as expected. So far, though, Comet C/2023 A3 Tsuchinshan-ATLAS is looking promising; its tail may soon be longer than its name.
Today I’m looking for insights from readers on two issues that were nagging me over the weekend.
The first issue has to do with the Fukushima nuclear accident and subsequent radiation fears, which I first brought up on this blog last week. I’ve been thinking about how to write articles that explain radioactivity and radiation in rather plain language, and about what we know is dangerous and what we know is not. One of the challenges is to confront the extreme irrationality of people’s fear of radioactivity. I’d like to hear my readers’ opinions of where this fear really comes from. One explanation of this fear that you’ll commonly read is that “radioactivity is scary because you can’t see or smell or feel it”. But that makes no sense; you can’t see, smell, or feel viruses either, or low levels of chemicals, so why aren’t people equally afraid of those things? Especially since the average person is far more at risk of getting cancer or other potentially deadly diseases from viruses (such as papilloma) or from chemicals (asbestos, benzene, etc.) then from radioactivity, despite all the atmospheric nuclear tests in the 1950s and 1960s and the Chernobyl and Fukushima nuclear plant accidents. So I don’t think this explanation is correct; there are plenty of invisible scary things in the world, and people’s fears are totally out of proportion to the true risks. I have my own suspicions as to the real causes, but I am wondering what my readers think.
The second issue is more technical. Comet ISON, dubbed, as is typical of our sensationalist age, “comet of the century” before it has even become easily visible [and it might still be a dud, or it might be the best of the year or even the last twenty years; but of the century? check back in 2099!]) is approaching the sun. There is indeed the tentative possibility, if it survives its very close encounter with the sun on November 28th, that it will give us a spectacular early morning display in December. In preparation, I’m wanting to read more details about the properties of cometary tails, which are generated by the physics of particles and fields (photons, ions, magnetic fields, momentum conservation, etc.). [Here’s a nice video of ISON’s tail and its interaction with the solar wind, the stream of charged particles emanating from the sun; also visible to its upper right is Comet Encke, which by chance is also near the sun. By the way you can also see, watching Encke, that its tail is not a trail; it does not point along its direction of motion but instead points away from the sun.] But I’ve been unable to find anything online other than vague descriptions with no technical information, or references to books or review articles from several decades ago. Do any of my readers know of a roughly up-to-date technical introduction to the physics of comets’ tails?
I’m pleased to say that last night I found comet Pan-STARRS, which is gracing the western sky just after sunset, and so I can recommend now that you all give it a try. Binoculars will definitely make it easier to find, and allow you to see more of it. It looks great! Here are some thoughts on how to find it, appropriate if you’re in a country at roughly the same latitude as the United States. (If you live far to the north or far to the south, you’ll need to get advice from someone who found it in a latitude similar to yours. I don’t believe people in the southern hemisphere can still see it.) (more…)
