In my mind, using our smart telescopes is all about observing the enduring, rather than the ephemeral. Sort term phenomena or glimpses of the nearby Solar System is not possible or even the best way to spend our smart scope time.
One of the first astronomers to stumble into our new world was William Herschel in the late 18th Century. He was then, as was Charles Messier, interested in ephemeral comets. But Herschel quickly learned that he was seeing nearly countless unchanging galaxies, star clusters, and ionized regions thorough his large aperture reflectors. Astronomers called them nebulae (clouds) and star clusters back then. And, seeing that it’s now spring time as I write this post, Herschel's following quotation seems particularly appropriate:
“The heavens are now seen to resemble a luxuriant garden, which contains the greatest variety of productions, in different flourishing beds.”
Sometimes I feel like that’s what is going on and that as our galaxy presents seasonally different regions of itself or windows into extragalactic space, that we are looking at different “beds” of nebulae, some near and some far. Compared to our human timescale all the objects are enduring. So much of the popular press on the sky and astronomy deals with ephemeral, brief time scale occurrences or phenomena. When I’m grumpy I call announcements of planetary conjunctions or oddly named full moons, “astrology.” Not that it’s nice to see groupings, but they have little meaning to me because they tell no real scientific story. The nebulae, however, do tell stories.
Sometimes I hear my smart telescope colleagues complain about the weather ruining their chance to observe -- especially just after they've received their new scope. I sometimes tell them what we can observe best will endure and we will have plenty of chances to image the objects.
One of my first lessons in graduate school was to learn the time scales of different astrophysical objects and processes. Here are some typical time scales of objects from William Herschel’s “garden”:
> Galaxies — Take hundreds of millions of years to rotate once and billions of years for their stellar populations to evolve. There can be occasional supernovae, so I guess those are ephemeral, but if you missed one, just wait. A supernova goes off every second somewhere in the observable universe. There are always new ones we can see, if we can see spiral galaxies. (I’ll write a posting sometime on how to best keep up with them.)
> Star Clusters — The ancient ones, the globulars, are even older than most of our Milky Way Galaxy’s stars. Globulars won’t ever change for billions of years. Open clusters, or sometimes called galactic, clusters like the Pleiades, change on much quicker time scales — hundreds of millions of years — still too long for use to see any changes with our instruments in our lifetime.
> HII Regions — Here I’m thinking of M42, the Orion Nebula, which is a stellar nursery. HII means it is primarily ionized hydrogen. It’s only a few million years old, I think. That’s because this ionized gas is 10,000 degrees Celsius and expanding quickly. Nevertheless, objects that change in millions of years will seem unchanging to us and our small scopes.
> Planetary Nebulae — These are dying stars and their glowing regions are HII regions too, though they are much smaller and expanding quickly. The Ring Nebula is the best known. It’s only 7,000 years old. On about the same time scale — tens of thousands of years — it will become invisible. Still, planetaries are not going to change in our lifetimes.
> Supernova Remnants — Here we might just see some “rapid” changes. M1, the Crab Nebula, is probably the best example. It wasn’t even visible before its progenitor star exploded in 1054 AD. Large telescopes have seen photographic changes on the order of tens to hundreds of years. We won’t at our image scale. Nevertheless, if there were a nearby supernova, that would be quite spectacular. These nebulae straddle the fence with ephemeral I guess.
Although these nebulae all present themselves on such long time scales that we shouldn’t worry about cloudy nights spoiling our fun, we can nevertheless become anxious about seeing all that we might like to experience. Unlike the 8 (or to some people, 9) planets, the nebulae come in legions: the Messier Catalog contains 110 objects; the New General Catalog (NGC) was based upon Herschel’s observations of nebulae and star clusters, but ballooned to 7,840 objects by the end of the 1880s. In principle our smart telescopes can image them all and then some.
A more practical list, I’ve found, was published by Orion Telescopes. It’s called “Deep Map 600,” which contains the Messier Catalog and many of the best NGC objects as well as some double stars. Even so, I’m not sure when I will be able to find the time to image them all.
For what it’s worth, here is my strategy when confronted with this cornucopia of targets. I make a careful list and go after them one by one or a few at each observing session. The Messier Catalog took me almost a year observing through my light-polluted, narrow eastern sky window in my back alley. (On a half marathon from a dark site I imaged have the catalog in just a few hours). Then after observing I sit inside with the new images on my iPad, grab a glass of wine and read an entry from one of Stephen James O’Meara’s “Deep Sky Companion” books while looking at the image I just captured. I believe we can’t really “see” what we don’t understand.
My big take away is that, when using smart telescopes, we and our audiences aren’t condemned to chase the ephemeral. We can explore much deeper mysteries on any night that is clear.
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Thanks to my floral design, sculptor, anatomist and artist friend, Melinda Whitmore, for the picture in this posting.
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