Astronomy – Page 19 – Cosmic Reflections

Next Generation Beginner’s Telescope

Let’s start with an 8″ f/4.5 Newtonian in an alt-az Dobsonian mount (remember the wonderful Coulter Odyssey?). Give it “push to” rather than go-to capability, and motorized tracking. The next generation part? Have a built-in imaging camera that can be moved in and out of the light path and the on-board smarts to look at the relationships between the stars in the image to determine where the telescope is pointing. Think of the enjoyment a beginner (or experienced astronomer, for that matter) would have pointing the telescope around the sky, finding an object of interest, and then turning a knob to take an image and having the telescope tell them what they’re pointed at! Or, alternatively, once the telescope knows where it is pointing using the imaging technique, it could show the observer how much to push in altitude and azimuth to reach a known object of interest. Oh, and a built-in laser collimator would be nice, too.

As a professional computer programmer, I would love to have the opportunity to write the software for such a system, and meeting the challenge of making this telescope far more “beginner friendly” than the current generation of go-to telescopes.

Satellite Crossings 2016-2017

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but since October 4, 1957 another “species” of sky vermin made their debut: artificial satellites. In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my ~¼° field of view.

I’ve put together a video montage of satellites I’ve recorded between December 14, 2016 and August 5, 2017. The component events are presented chronologically as follows:

UT Date
12-14-2016
1-15-2017
5-5-2017
6-7-2017
6-19-2017
7-25-2017 (2 satellites)
8-5-2017

Target Star
UCAC4 538-7253
Tycho 586-1051-1
Tycho 1422-911-1
Tycho 4997-136-1
Tycho 6799-309-1
Tycho 666-190-1
UCAC4 548-7392

Asteroid
2485 Scheffler
19807 (2000 SE₁₆)
71612 (2000 EH₁₂)
11133 Kumotori
68112 (2000 YC₁₄₃)
491 Carina
151 Abundantia

In all cases, the asteroids were too faint to be recorded. And, in all cases, the target star was not occulted by the asteroid (a miss). In the final event, the satellite passed right over the target star (9:40:11.679 UT) during the period of time the event would be most likely to occur (9:40:10 ± 3 s)! Fortunately, the seeing disc of the target star was never completely obliterated by the passing satellite, so I was able to determine unequivocally that the asteroid missed passing in front of the star from my location on Spaceship Earth.

Here’s a graph of the brightness of UCAC4 548-7392 during the last video clip. You can definitely see the close appulse of the satellite with the star!

In general, the slower the satellite is moving across the field, the higher is its orbit around the Earth. One must also consider how much of the satellite’s orbital motion is along your line of sight to the satellite. In the following montage of two video clips, the first satellite is very slow moving and thus most likely in a very high orbit. The second video clip shows a satellite that is quite faint. Again, the asteroids are too faint to be recorded and no asteroid occultation event occurred.

UT Date
5-14-2017
6-8-2017

Target Star
Tycho 5011-133-1
Tycho 5719-308-1

Asteroid
190471 (2000 DG₂₇)
321656 (2010 BM₉₀)

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Yellow LED Astronomy Flashlights

Back when I had my astronomy-friendly outdoor lighting business, I used to sell yellow-LED flashlights that I bought from Robert D. Mantell in North Hollywood, California, under the trademark Lo-Glo™.

The Houston flood Memorial Day weekend 2015 wiped out the remaining inventory I had and, sadly, these wonderful flashlights are no longer available.

It is not rocket science. You need to start with a well-made flashlight, replace the regular bulb with a yellow LED and the appropriate current-limiting resistor, and voila!

Yellow may be better than red. See the article by Robert Dick, “Is Red Light Really Best?”, in the June 2016 issue of Sky & Telescope.

There’s a great business opportunity here. It wouldn’t take much to make a better astronomy flashlight than what Orion and others sell. Besides, I have found these yellow-LED flashlights to be most useful for moving around the house after bedtime (such as a bathroom trip) to avoid being exposed to any bright light at night which would affect your night vision and even your circadian rhythm.

If you know of any astronomy-friendly yellow LED flashlights or would like to manufacture some, please post a comment here or contact me directly.

Bob Mantell’s wonderful yellow LED / amber LED astronomy flashlight

These flashlights are also perfect for getting around the house at night without having to turn lights on, the glove box of your car, reading at night, and many other uses as well.

Eclipse Weather – IL, MO, KS, NE, and WY

I’ve written a SAS program that pulls National Weather Service zone forecasts for the 49 counties along the eclipse centerline in Illinois, Missouri, Kansas, Nebraska, and Wyoming. During the week leading up to the Monday, August 21, 2017 total solar eclipse, I will be frequently updating this page:

Eclipse Weather

I hope you will find this weather resource useful as you plan for a cloud-free view of this wondrous event. Clear skies!

Constants of Nature

We continue our series of excerpts (and discussion) from the outstanding survey paper by George F. R. Ellis, Issues in the Philosophy of Cosmology.

The constants of nature are indeed invariant, with one possible exception: the fine structure constant, where there is claimed to be evidence of a very small change over astronomical timescales. That issue is still under investigation. Testing such invariance is fundamentally important, precisely because cosmology usually assumes as a ground rule that physics is the same everywhere in the universe. If this were not true, local physics would not guide us adequately as to the behaviour of matter elsewhere or at other times, and cosmology would become an arbitrary guessing game.

The fine structure constant (α) is a unitless number, approximately equal to 1/137, that characterizes the strength of the electromagnetic force between electrons. Its value is the same no matter what system of measurement one chooses. If the value of α were just a little smaller, molecular bonds would be less stable. If the value of α were just a little larger, carbon—which is essential to life—could no longer be produced inside of stars.

Do constants of nature, specifically dimensionless physical constants such as α, the fine structure constant, and μ, the proton-to-electron mass ratio¹, vary with time? This is an active topic of investigation. If constants of nature change at all, they change so slowly that it presents a formidable challenge to measure that change. But if they do indeed change, it would have profound implications for our understanding of the universe. A lot can happen in 13.8 billion years that might not be at all obvious in the infinitesimal interval of a human life or even human civilization.

“Despite the incessant change and dynamic of the visible world, there are aspects of the fabric of the universe which are mysterious in their unshakeable constancy. It is these mysterious unchanging things that make our universe what it is and distinguish it from other worlds we might imagine.” – J.D. Barrow, The Constants of Nature. (Vintage, 2003).

I’d like to conclude this discussion of constancy and change with a poem I wrote about the possibility of sentient life having a very different sense of time than we humans do.

Life On a Cold, Slow World

Life on a cold, slow world
On Europa, perhaps, or even Mars
On distant moons and planets of other stars.

A minute of time for some anti-freeze being
Might span a year for us human folk
(A greeting could take a week, if spoke.)

How fast our busy lives would seem to pass
Through watchful eyes we cannot see
Curious about our amative celerity.

The heartbeat of the universe runs slow and deep
We know only violent change, the sudden leap
But that which is most alive appears to sleep.

David Oesper

¹μ = m_p / m_e ≅ 1836

References
Barrow, J.D., Webb, J.K., 2005, Scientific American, 292, 6, 56-63

Ellis, G. F. R. 2006, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
[http://arxiv.org/abs/astro-ph/0602280]

Apparent Magnitude, Absolute Magnitude, and Distance

A simple equation relates apparent magnitude, absolute magnitude, and distance. Know any two, and you can calculate the third.

Known: Apparent Magnitude (m), Absolute Magnitude (M)
Unknown: Distance (d), in parsecs

Known: Apparent Magnitude (m), Distance (d)
Unknown: Absolute Magnitude (M)

Known: Distance (d), Absolute Magnitude (M)
Unknown: Apparent Magnitude (m)

If this were a perfect universe, the known quantities could always be measured as precisely as one desires. But, of course, that isn’t the case.

Apparent Magnitude – if the observations are made from the surface of the Earth, atmospheric reddening and extinction (atmospheric r/e) must be taken into account to determine the apparent magnitude above the Earth’s atmosphere. Even above the Earth’s atmosphere, cosmic reddening and extinction (cosmic r/e) must also be quantified. Both atmospheric r/e and cosmic r/e¹ cause the observed apparent magnitude to appear fainter than it otherwise would be, and bluer wavelengths are more severely affected than redder wavelengths. The net result is to make objects appear fainter and redder than they would be if there were a perfect vacuum between source and observer.

Absolute Magnitude – is a measure of the intrinsic brightness of a celestial object, and this can only be measured indirectly for objects outside of our solar system.

Distance – is difficult to measure for objects outside of our solar system. Trigonometric parallax gives the most accurate results for nearby stars, but uncertainty increases rapidly with increasing distance.

Apparent magnitude is the only one of these quantities that is a direct instrumental measurement: absolute magnitude and distance are determined indirectly and thus are subject to greater uncertainty.

¹Atmospheric reddening and extinction (atmospheric r/e) is traditionally called atmospheric extinction, and cosmic reddening and extinction (cosmic r/e) is traditionally called interstellar reddening.  Since in both cases light is both reddened and diminished in intensity, and because "cosmic" encompasses both interstellar and intergalactic matter between source and observer, I suggest here that atmospheric r/e and cosmic r/e might be an improvement in terminology.

Milky Way Supernova Candidates

There is a supermassive binary star in our own Milky Way Galaxy that has the potential to create a super-supernova (hypernova?). It could go off tomorrow—or a million years from now. The star system’s name is Eta Carinae. Currently 4th-magnitude and located some 7,500 ly away in the direction of the southern constellation Carina (“The Keel”), Eta Carinae consists of a 100-200 M_☉ star and a 30-80 M_☉ star in a highly-eccentric 5.54^y orbit with the more massive star undergoing prodigious mass loss. Eta Carinae never rises above the horizon unless you’re south of latitude 30° N. So, if Eta Carina ever does go supernova while humans still walk the Earth, you’ll have to travel at least as far as southern Texas or southern Florida to see it. And it will be an impressive sight, easily visible during the daylight hours.

Closer to home, there are seven prime candidates for the next relatively nearby supernova. The nearest of these currently is IK Peg. Keep in mind that over hundreds of thousands of years, stars move quite a lot, so what is close to us now will not necessarily be close to us when a supernova event finally does occur.

IK Pegasi, a binary system comprised of a white dwarf already near the Chandrasekhar limit, and a close-by soon-to-be-giant main-sequence star, lies just 147 to 155 ly away in the direction of the constellation Pegasus, the Winged Horse. IK Peg appears to us visually as a 6th magnitude star located roughly ⅓ of the way from Delphinus to the Square of Pegasus. As the giant star expands into the vicinity of the white dwarf, the white dwarf will accumulate enough material to put it over the Chandrasekhar limit, and a Type Ia supernova will ensue.

Spica (α Vir), located at a distance between 237 and 264 ly, is a massive binary system (10 M_☉ and 7M_☉), with the two stars orbiting each other every four days.

Alpha Lupi (α Lup) is a massive star (~10 M_☉) located between 454 and 476 ly from our solar system.

Antares (α Sco) is a massive star (~12 M_☉, the supernova progenitor) orbited by another massive star (~7 M_☉). However, their orbital period is at least 1,200 years. The Antares system lies between 473 and 667 ly from our solar system

Betelgeuse (α Ori) is a massive star (~12 M_☉) between 500 and 900 ly away. Incidentally, there is a lot of uncertainty about the distance to Betelgeuse, primarily because it’s angular size (44 mas) is an order of magnitude larger than its parallax (4.5 mas) (Harper et al. 2017).

Rigel (β Ori) is a massive star (~23 M_☉) between 792 and 948 ly distant.

Gamma² Velorum (γ² Vel) is a binary system 1,013 to 1,245 ly distant containing two stars which will go supernova in the not-too-distant future. The system consists of a 28.5 M_☉O7.5 giant star and a 9.0 M_☉Wolf-Rayet star (the nearest, incidentally) orbiting each other every 78.5 days. The Wolf-Rayet star will be the first to supernova, followed later by the O giant star.

Tomorrow—or a million years from now? We have no way of accurately predicting. But rest assured, in the unlikely event that any one of these stars goes supernova during our lifetimes, none will be close enough to harm us. Instead, for a time, we will be treated to a object comparable to the Moon in brightness and visible both day and night.

References
Firestone, R.B., 2014, ApJ, 789, 29
Harper, G.M., Brown, A., Guinan, E.F., et al., 2017, AJ, 154, 11
Richardson, N.D., Russell, C.M.P., St-Jean, L., et al., 2017, MNRAS

Brightest Event Ever Observed

On June 14, 2015, perhaps the intrinsically brightest event ever recorded was detected at or near the center of the obscure galaxy APMUKS(BJ) B215839.70−615403.9 in the southern constellation Indus, at a luminosity distance of about 3.8 billion light years.

ASASSN-15lh (All–Sky Automated Survey for SuperNovae), also designated SN 2015L, is located at α₂₀₀₀=22^h02^m15.45^s, δ₂₀₀₀=-61° 39′ 34.6″ and is thought to be a super-luminous supernova—sometimes called a hypernova—but other interpretations are still in play.

Let’s put the brightness of SN 2015L in context. Peaking at an absolute visual magnitude of -24.925 (which would be its apparent visual magnitude at the standard distance of 10 parsecs), SN 2015L would shine as bright as the Sun in our sky if it were 14 light years away—about the distance to van Maanen’s Star, the nearest solitary white dwarf. SN 2015L would be as bright as the full moon if it were at a distance of 8,921 light years. SN 2015L would be as bright as the planet Venus if it were at a distance of 333,000 light years. Since the visible part of our galaxy is only about 100,000 ly across, had this supernova occurred anywhere in our galaxy, it would have been brighter than Venus. If SN 2015L had occurred in M31, the Andromeda Galaxy, 2.5 million light years away, it would take its place (albeit temporarily) as the third brightest star in the night sky (-0.47^m), after Sirius (-1.44^m) and Canopus (-0.62^m), but brighter than Alpha Centauri (-0.27^m) and Arcturus (-0.05^m).

The Open Supernova Catalog (Guillochon et al. 2017) lists three events that were possibly intrinsically brighter than SN 2015L. Two events were afterglows of gamma ray bursts GRB 81007 and GRB 30329: SN 2008hw at -25.014^m and SN 2003dh at -26.823^m, respectively. And the other event was the first supernova detected by the Gaia astrometric spacecraft, Gaia 14aaa, 500 Mly distant, shining perhaps as brightly as -27.1^m.

References
Chatzopoulos E., Wheeler J. C., Vinko J., et al., 2016, ApJ, 828, 94
Dong S., Shappee B. J., Prieto J. L., Jha S. W., et al., 2016, Science, 351, 257
Guillochon J., Parrent J., Kelley L. Z., Margutti R., 2017, ApJ, 835, 64

The Beginning

We continue our series of excerpts (and discussion) from the outstanding survey paper by George F. R. Ellis, Issues in the Philosophy of Cosmology.

Thesis D1: An initial singularity may or may not have occurred.
A start to the universe may have occurred a finite time ago, but a variety of alternatives are conceivable: eternal universes, or universes where time as we know it came into existence in one or another way. We do not know which actually happened, although quantum gravity ideas suggest a singularity might be avoided.

If we imagine, for a moment, running the clock of the universe backwards to earlier and earlier times, its size gets smaller and its density gets larger until we reach a moment—even earlier than the putative inflationary era—when classical physics at the macroscopic level no longer applies and some (as yet unknown) quantum physics must apply to everything—even gravity. Therein lies the problem, because if you run the clock backwards just 5.39 x 10^-44 second from this time, you reach the purported moment of the Big Bang—the initial singularity. But whoa (or perhaps woe)! How can we say anything about the Big Bang—or even if it occurred at all—since the laws of known physics completely break down 5.39 x 10^-44 second (the Planck time) after the Big Bang! See the problem?

Perhaps the universe came into existence through a process analogous to radioactive decay where an alpha particle leaves a nucleus through quantum tunneling. Perhaps our universe “tunneled” into existence from somewhere else, and thus our beginning isn’t really the beginning. This is just one of many possibilities.

This is a key issue in terms of the nature of the universe: a space-time singularity is a dramatic affair, where the universe (space, time, matter) has a beginning and all of physics breaks down and so the ability to understand what happens on a scientific basis comes to an end. However eternal existence is also problematic, leading for instance to the idea of Poincaré’s eternal return: everything that ever happened will recur an infinite number of times in the future and has already occurred an infinite number of times in the past. This is typical of the problems associated with the idea of infinity. It is not clear in the end which is philosophically preferable: a singularity or eternal existence. That decision will depend on what criteria of desirability one uses.

While infinity is a highly useful mathematical device, one can make a strong argument that infinities do not exist in the physical universe (or even multiverse). Quantum physics already gives us a possible clue about the infinitely small: we appear not to be able to subdivide space or time any further than the Planck length (1.616 x 10^-35 meter) or the Planck time (5.39 x 10^-44 second). We would not be able to distinguish between two points less than a Planck length apart, nor two moments in time less than a Planck time apart. While harder to envision, might not there also be an upper limit to size? And time?

Thesis D2: Testable physics cannot explain the initial state and hence specific nature of the universe.
A choice between different contingent possibilities has somehow occurred; the fundamental issue is what underlies this choice. Why does the universe have one specific form rather than another, when other forms consistent with physical laws seem perfectly possible? The reasons underlying the choice between different contingent possibilities for the universe (why one occurred rather than another) cannot be explored scientifically. It is an issue to be examined through philosophy or metaphysics.

Metaphysics is the part of philosophy that deals with existence, space, time, cause and effect, and the like. Metaphysics begins where physics necessarily ends due to observational limitations.

Did anything exist before the Big Bang?

Was there a Big Bang?

What are the physical properties of the very early universe, when energy densities existed that are far beyond our ability to recreate in the laboratory?

What lies beyond our particle horizon?

Are there other universes?

Why does anything exist at all?

References
Ellis, G. F. R. 2006, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
[http://arxiv.org/abs/astro-ph/0602280]

Liddle, A.R. 2015, An Introduction to Modern Cosmology, 3rd ed., Wiley, ISBN: 978-1-118-50214-3.

Meteor Watching Site Needed Near Dodgeville

Meteor activity is starting to ramp up as we enter the second half of the year, and once again I am frustrated by those of us who live in Dodgeville not having a good location nearby for watching meteors. All that would be needed is a 12 x 12 ft. patch of ground that is kept mowed, has a good view of most of the sky, is not too near any cities or towns, and where no dusk-to-dawn insecurity lights are visible to spoil the view. Within about 10 miles of Dodgeville would be good, too, to minimize the late-night drive time home (and sleepy driving), especially on nights during the work week.

The Twin Valley Lake picnic area at Governor Dodge State Park is a perfect location for deploying a reclining lawn chair to watch meteors, but state park regulations prohibit such activities after 11:00 p.m. Most meteor showers are best after midnight, and this time of year when we’re on daylight saving time, 1:00 a.m. is really midnight.

I would even be willing to pay a monthly or per-use fee to a rural landowner for the privilege to set up my lawn chair on their land to watch meteors from time to time. Please add a comment here or email me at oesper at mac dot com to contact me about this.