The first recorded supernova in our Milky Way galaxy (or anywhere else, for that matter) was seen to blaze forth in the constellation Centaurus by astute Chinese astronomers in 185 AD. Including that one, only seven confirmed supernovae have been observed in our Milky Way galaxy, though thousands are discovered each year in other galaxies.
Supernova light reached Earth in AD 185, 393, 1006, 1054, 1181, 1572, and 1604. All seven of these events occurred before the invention of the telescope. Are we overdue for another supernova? Well, given this ridiculously small sample, we can endeavor to do some simple “statistics”. The shortest recorded interval between two Milky Way supernovae was 32 years between 1572 and 1604. The longest interval has been 613 years, between the supernovae of 393 and 1006 (assuming none went unnoticed). On average then (such as it is), we “should” have seen a Milky Way supernova around 1841, and using the longest interval of 613 years, we might be expecting one by the year 2217. Undoubtedly, some supernovae in the Milky Way have escaped detection because they lay behind thick interstellar clouds.
The big mystery to me is why are there no recorded supernova events prior to 185 AD? The earliest extant records of astronomical events go back at least as far as 2316 BC (a comet in the constellation Crater was recorded by Chinese astronomers), but in the intervening 2,500 years there has been no mention of anything that could be attributed to a supernova. Or has there? Some writings before and after 185 AD suggest possible supernovae, but until a supernova remnant is identified, we need to look for other explanations.
Here follows a table of the known observed Milky Way supernovae. Of course, other supernova remnants have been discovered in our Milky Way galaxy, but no record has yet been discovered describing these events. Many of them predate recorded history.
In the table below, you’ll note that these supernovae tend to lie close to the galactic plane (galactic latitude b = 0°)—not at all surprising considering that’s where most of the stars are.
In 2021, the best dates and times for observing the zodiacal light are listed in the calendar below. The sky must be very clear with little or no light pollution. The specific times listed are for Dodgeville, Wisconsin (42° 58′ N, 90° 08′ W).
Here’s a nicely-formatted printable PDF file of the zodiacal light calendar:
The best nights to observe the zodiacal light at mid-northern latitudes occur when the ecliptic plane intersects the horizon at an angle of 60° or steeper. The dates above were chosen on that basis, with the Sun at least 18° below the horizon and the Moon below the horizon being used to calculate the times. An interval of time of one hour either before morning twilight or after evening twilight was chosen arbitrarily because it is the “best one hour” for observing the zodiacal light. The zodiacal light cone will be brightest and will reach highest above the horizon when the Sun is 18° below the horizon (astronomical twilight), but no less.
If you are interested in calculating the angle the ecliptic makes with your horizon for any date and time, you can use the following formula:
where I is the angle between the ecliptic and the horizon, ε is the obliquity of the ecliptic, φ is the latitude of the observer, and θ is the local sidereal time (the right ascension of objects on the observer's meridian at the time of observation).
Here’s a SAS program I wrote to do these calculations:
Why does the Earliest Sunset come before the Winter Solstice and the Latest Sunrise after?
Why does the Earliest Sunrise come before the Summer Solstice and the Latest Sunset after?
Ever wonder? I have. And aside from some hand-wavy explanations, I’ve never been able to explain this very well. Here’s the best explanation I have seen yet, provided in the December 2007 issue of Sky & Telescope, p. 55:
You’d think the earliest sunset would come on the shortest day (or longest night) of the year, at the winter solstice. But in fact, the day-night cycle shifts back and forth a little with the seasons, due to the tilt of Earth’s axis and the ellipticity of Earth’s orbit. At the beginning of December, sunrise, midday, and sunset all happen a little earlier than they “should”, and in January they run a little late. So the earliest sunset ends up being two or three weeks before the solstice, and the latest sunrise is two or three weeks afterward. The exact dates depend on your latitude.
Continuing along that same line of thought…
At the beginning of June, sunrise, midday, and sunset all happen a little later than they “should” and in July they run a little earlier. So the earliest sunrise ends up being about a week before the solstice, and the latest sunset is about a week afterwards. The exact dates depend on your latitude.
I know, I know. You still have a question. “Why are the dates of earliest sunrise and latest sunset closer to the summer solstice than the dates of earliest sunset and latest sunrise to the winter solstice?” Good question. I think it has everything to do with the fact that the Earth is near aphelion at the time of the summer solstice, and thus moving most slowly in its orbit around the Sun (the Earth’s orbit is slightly elliptical and not circular). That means that the Sun is moving slowest against the background stars and thus the accumulated difference between the sidereal day and solar day is the smallest at that time of year. That means the spread of days between earliest sunrise and latest sunset is less. Conversely, at the winter solstice, Earth is near perihelion, and therefore it is moving most quickly in its orbit around the Sun. That means that the Sun is moving fastest against the background stars and thus the accumulated difference between the sidereal day and solar day is largest at that time of year. That means the spread of days between earliest sunset and latest sunrise is more.
Here in Dodgeville, Wisconsin, where the latitude is just shy of 43˚ N and the longitude is just a tad over 90˚ W, the earliest sunset this year is today, Tuesday, December 8, 2020, at 4:25:49 p.m.
Latest sunrise in 2021 will be on both Saturday, January 2 and Sunday, January 3 at 7:31:51 a.m.
Pause to consider that if we were on year-round daylight saving time, latest sunrise wouldn’t be until 8:31:51 a.m.
Using the newly-invented telescope, French astronomer Nicolas-Claude Fabri de Peiresc (1580-1637) discovered the now-famous Orion Nebula (M42) when he was 29 years old, 410 years ago on this day.
November 26, 1610.
But wait a minute. You and I can see a nebulous “star” below the belt of Orion with our unaided eyes under a reasonably dark sky. Why wasn’t this object discovered long before the invention of the telescope?
Apparently, there is no known report of a “nebulous star” in the sword of Orion prior to Peiresc’s discovery. Is the Orion nebula brighter now than it was a few centuries ago? Is it possible an earlier observational report somehow got missed or was not properly interpreted?
There is speculation that the Maya civilization of Mesoamerica recognized the Orion Nebula long before Peiresc’s discovery, describing it as smoke from the smoldering embers of creation.
One can only stand in wonderment at the knowledge and experiences of hundreds of generations of men, women, and children who are utterly unknown to us today. Passed from person to person and generation to generation through oral tradition, never written down and eventually lost. Or written down on documents that later disintegrated or were purposefully destroyed.
Who hasn’t wished that they could could time travel back to the past? Have you ever wondered what your current location looked like a hundred years ago? A thousand years ago? Ten thousand or more years ago? Though sending humans into the past will probably never be possible, who’s to say that we won’t eventually figure out a way to view and perhaps even hear the past, without actually being there or having the ability to change it?
Pittsburgh telescope maker, optician, and educator John Alfred Brashear (1840-1920) was born 180 years ago this day. His world-renowned optical company made much of the astronomical equipment in use in the United States during the late 19th and early 20th centuries. His works included a 30-inch refractor for Allegheny Observatory in Pittsburgh, a 15-inch refractor for the Dominion Observatory in Canada, and the 8-inch refractor at the Drake University Municipal Observatory in Des Moines, Iowa.
My good friend, telescope maker Drew Sorenson in Jefferson, Iowa, has been a fan of John Brashear for many years. Not only does Drew make fine refractors as did Brashear, but there is more than a little resemblance between the two men. Drew introduced me to a delightful book entitled John A. Brashear: The Autobiography of A Man who Loved the Stars, which was first published posthumously in 1924. For anyone interested in the history of astronomy and the life of a scientist and humanitarian who struggled from near-obscurity to great success with only an elementary school education, this book is a must-read.
Here are three of my favorite passages from the book.
Somewhere beneath the stars is work which you alone were meant to do. Never rest until you have found it.
There is another yarn I cannot resist telling. The young farmer who had been bringing Mrs. Brashear her supply of vegetables asked her one day if I would let him look in the big telescope if he came up some clear evening. She encouraged him to do so, and I found him waiting one night to see the sights. I did not know whether or not he had any knowledge of astronomy, but I asked him what he would like to look at. He replied, “Juniper.” I told him that unfortunately that planet was not visible in the sky at the time. Then he expressed a desire to see “Satan.” But his Satanic Majesty was not around either. The climax came when he asked if I could show him the “Star of Jerusalem!” I ended it by showing him the moon and some clusters, and he went home very happy.
I remember, too, an old gentleman over eighty years of age who climbed the hill one moonlight night for a look in the telescope. The good man was utterly exhausted when he reached the house, and Ma and I had him lie down on the lounge to rest before climbing the stairs to the telescope. The views that night were fine, and I can hear the soliloquy yet of the dear fellow as he said, “For many years I have desired to see the beauties of the heavens in a telescope. I have read about them and heard lectures about them, but I never dreamed they were so beautiful.” We invited him to stay all night; but as it was moonlight, and much easier for him to go down the hill than to come up, he insisted on going home. I went part of the way with him to see that he got along all right; and all the way he expressed his delight at having the wish of a lifetime gratified that night.
Three weeks later the funeral cortège of that old man passed along the road on the opposite hillside that led to the cemetery, and it has always been a pleasure to remember that I was able to be of some service in gratifying one of his desires of a lifetime.
I think that all my life I have been partial to old people and children, and it has always been a source of genuine pleasure to contribute to their happiness.
John A. Brashear: The Autobiography of A Man who Loved the Stars (1924)
Obviously, this is going to be easier to do in a small community, and most likely one that is economically depressed.
What’s in it for them? What would the motivating factors be?
A commitment from X number of people that they would move to the community provided the community agrees to 1-3 above being done. Options for new residents would be to either purchase or rent an existing home/apartment/RV space/etc., or to build the same but land would have to be available.
The new residents would commit to working with the existing residents and businesses to improve the community and provide new opportunities, ensuring that this is a win-win situation for both existing and new residents.
The new residents would commit to doing some or all of the things outlined in the Mirador Astronomy Village specifications document, or something like it.
The influx of new residents and tourism will benefit all in the community, both economically and socially.
Does anyone know of a rural community that might be interested in putting their town “on the map” as an astronomy-friendly community for residents and visitors?
On this date 140 years ago, American physician and prominent amateur astronomer Henry Draper (1837-1882) made the first successful photograph of the Great Nebula in Orion, now usually referred to as the Orion Nebula. He used an 11-inch telescope (an Alvan Clark refractor!) and an exposure time of 50 minutes for the black and white photograph.
Draper continued to improve his technique, and a year and a half later he obtained a 137-minute exposure showing much more detail.
It really is amazing how image recording technology has improved over the past century and a half! At its best, film-based photography had a quantum efficiency of only about 2%, which means that only 2 out of every 100 photons of light impinging on the photographic medium is actually recorded. The rest is reflected or absorbed. The human eye—when well dark adapted—has a quantum efficiency of 15% or better, easily besting photography. Why, then, do photographs of deep sky objects show so much more detail than what can be seen through the eyepiece? The explanation is that the human eye can integrate photons and hold an image for only about 0.1 second. Film, on the other hand, can hold an image much longer. Even with reciprocity failure, photographic media like film can collect photons for minutes or even hours, giving them a big advantage over the human eye. But charge-coupled devices (CCDs) are a considerable improvement over older technologies since they typically have a quantum efficiency of 70% up to 90% or more. The CCD has truly revolutionized both professional and amateur astronomy in recent decades.
During the first half of 2020, I serendipitously captured a whopping nine meteors on my telescope’s 17 x 11 arcminute video field of view while observing potential asteroid occultation events. I used the method described in There’s a Meteor in My Image to determine the radiant for each meteor. Here they are.
The International Meteor Organization (IMO) identifies the antihelion source as “a large, roughly oval area of about 30˚ in right ascension and 15˚ in declination, centered about 12˚ east of the solar opposition point on the ecliptic, hence its name. It is not a true shower at all, but is rather a region of sky in which a number of variably, if weakly, active minor showers have their radiants.”
A sporadic meteor is any meteor that does not come from a known radiant.
Meteors enter the Earth’s atmosphere at a speed between 10 and 70 km/s, and burn up at an altitude of about 80 km. For a sight line perpendicular to the meteor’s path, the angular velocity should range between 7˚ and 41˚ per second. This means a meteor should cross the 17′ x 11′ field of my video camera in 0.03 seconds or less. Field traversal will take longer than this the closer the meteor is to its radiant or anti-radiant point.
The lowest stable altitude a satellite can orbit is about 200 km, where it will have an orbital velocity on the order of 8 km/s. This is slower than the slowest meteors. For a sight line perpendicular to the satellite’s path, the maximum angular velocity a satellite should have is about 2˚ per second.
Given these admittedly BOTEC calculations, one could reasonably conclude that if the object traverses the field in a single frame, it is probably a meteor. If not (and it is not an airplane), it is a satellite.
The object in the 8 May 2020 video does appear to be moving slow enough to be a satellite, but because it is traveling much faster than satellites usually do it must be orbiting quite low, close to re-entry. I was not able to identify the satellite, which is often the case for the fastest-moving satellites. My camera is sensitive enough to pick up tiny pieces of space debris orbiting at low altitude, and though these objects are no doubt catalogued by military organizations, they do not generally show up in the publicly-available orbital element datasets for satellites.
This one’s unusual in that there are two distinct “flare-ups” along the path. It is reasonably good match to the antihelion radiant for 12 May 2020, and though I have seen meteors experiencing outbursts along their paths, a more likely explanation for this event is that it is low altitude satellite with two “sun glint” events. What do you think?
I was surprised to record so many meteors during the first half of 2020, as there is generally much less meteor activity between January and June than there is between July and December.
The Mirador specifications document located in our Files section and here gives a lot of detail about our vision for an astronomy-friendly residential community and astronomy resort & learning center. But before any of this can be developed, we need to have land.
The next step for Mirador is to create a legal entity that can raise money for a land purchase.
Some challenges we face:
Mirador could be located in Arizona, New Mexico, or West Texas. We don’t want to limit our land search to one state, but incorporating in the state where land will be purchased is less complicated.
We need an attorney who is familiar with Arizona, New Mexico, and West Texas law, but especially with real estate law and corporate law.
Does anyone know an attorney who is interested in astronomy, might want to become involved with this project, and might be willing to do some pro bono work?
Does anyone know a fundraising professional who is interested in astronomy and might want to become involved with this project?
Our most immediate need is to find an attorney to help us create the legal entity that will be necessary to raise money for a land purchase. This legal entity will exist for one and only one purpose: to purchase land for Mirador Astronomy Village.
Here is what we currently envision for the land-purchase legal entity. Would appreciate your thoughts before we submit this to a prospective attorney.
Issuance of Shares
1 share = $1000
No limit on the number of shares that can be purchased
Initial shares and additional shares can be purchased at any time
Hold the money in an FDIC-insured interest-bearing account
Value of shares remains unchanged except for interest accrued
Shareholders can return shares and remove their investment (plus interest) at any time up through the point of the shareholders voting in favor of making an offer on a property but before an offer is actually made
1 share = 1 vote
Funds can only be used to purchase a property for Mirador Astronomy Village; any leftover funds will be returned to the shareholders proportional to the number of shares they own.
If there are insufficient funds to purchase the property without financing, the shareholders will not be a party to that financing arrangement.
It is possible we may acquire land that is “partially donated”, that is the land owner may agree to sell us the land for the amount of funds we have raised to date.
Shareholders will be known as Community Founders.
After the property is purchased, the monetary value of the shares goes to $0.
Benefits for shareholders after the property is purchased will include free RV, camping, and astronomy access to the property as soon as it is acquired; after development, no-additional-cost benefits such as free access to astronomy programs will be offered.
Benefits will be proportional to the number of shares owned.
If Mirador Astronomy Village isn’t established on the property within five years, the property will be sold and the proceeds returned to the shareholders in proportion to the number of shares they own.
Some Reasons Why I Want to Live in a Dark-Sky Community
Posted 13 July 2020
I drove 20 miles round-trip early Saturday morning to view Comet NEOWISE (C/2020 F3) for the first time. It is beautiful! Easily visible to the unaided eye and spectacular in binoculars. And now, in the more convenient evening sky!
I had to trespass onto private land (as I often do) because we are not allowed to be in any of our state parks here in Wisconsin during the hours of 11:00 p.m. to 6:00 a.m. (unless you are a paid camper at a campsite).
One of my motivations for living in a dark-sky community is having a great view of a comet like C/2020 F3 literally right outside my door night after night. The same goes for watching meteors. The visibility of comets and meteors are severely impacted by light pollution—both the general urban skyglow but also nearby lights. Along with just about every other aspect of observational astronomy.
All my adult life I have spent significant time and energy educating (and becoming educated myself) about light pollution, environmentally-friendly lighting, and, of course, astronomy. There have been small victories, yes, but overall I feel my contributions have been a drop in the proverbial bucket.
Living in a “regular community” (as I have all my life), there is always the trepidation with every new neighbor or lighting technology change that your view of the night sky will be degraded even further than it already has, and there is not a darned thing you can do about it if the perpetrator (be it a neighbor or the city) chooses to marginalize you and your kindly-presented concerns. Heck, this can even be a problem living in a rural area. When I had my Outdoor Lighting Associates, Inc. business in Iowa from 1994-2005, I can’t count the many times I got a call from a distressed rural resident that had a new neighbor who decided to light up their place like Las Vegas.
Sure, a lighting ordinance would help a lot, but in most cities and towns these days they’ll look at you like you’re from Mars if you try to make enacting one a priority.
There are many advantages to living in a small community, but where I live now (population 4,700) there is no community will nor interest in reigning in bad lighting or in protecting the night sky. However, in 1999 I was deeply involved with writing a lighting ordinance and getting it approved in Ames, Iowa, a university town of 50,000 (at the time). Being a well-educated university town had a lot to do with our success there. Those were kinder, gentler times then, too.
Lighting at Mirador
I’d like to take this opportunity to explain more about the outdoor lighting aspects of an “astronomy-friendly” community. Indoor lighting would have no restrictions except the amount of light shining outdoors at night would need to be controlled with some sort of window covering.
Ideally, an astronomy-friendly community would not allow any dusk-to-dawn lighting. Why have a light shining all night long when most of the night no one will be making use of its illumination? Modern light sources such as LEDs, occupancy sensors, and control electronics have advanced to the point (both in terms of technology and affordability) that dusk-to-dawn lighting is no longer needed, at least not in the kind of small community we are talking about here. I would like Mirador Astronomy Village to be an ongoing demonstration project for the wider world showing a better way to do outdoor lighting. By “better” I mean lighting that provides needed illumination where and when it is needed without adversely affecting the nighttime environment, including our view of the night sky. By “better” I also mean using passive reflective or light-colored materials where possible to reduce the need for—or brightness of—outdoor lighting.
There’s a lot to be said in favor of using “personal lighting devices”, also known as flashlights, when walking about at night.
The permanent outdoor lighting that is installed should be properly shielded and directed so that only what needs to be illuminated is illuminated, thus eliminating glare, light trespass, and direct uplight. The right amount of light for the intended task should be used, never more than is needed.
We certainly will need to be mindful of anyone visiting or living in our community with vision limitations. This is most likely going to be an issue in the areas open to the public at night. Observational astronomers, as a general rule, have learned to see better at low illumination levels through familiarity and experience, but the same is not true for the general public. Accommodations will need to be made with this in mind, and I would expect the public areas to have more illumination.
Getting this project off the ground has been challenging in the midst of a pandemic. There is at least one of several things you can do right now to help this project along.
Post a comment here!
Join the Dark-Sky-Communities discussion group at https://dark-sky-communities.groups.io/g/main. There are several subscription options for your convenience, and even if you subscribe to receive individual emails, the traffic on this moderated group is light and focused specifically on astronomy-friendly residential communities.