Who hasn’t tried to replace an article of clothing when it finally wears out, only to find that it is no longer available? When I find something I like, I like to stick with it—or at least something quite similar. Increasingly, I am having a harder and harder time finding clothing I like. Is it my age?
Take, for example, long sleeve shirts. I like button-down dress casual shirts, but if you’re looking for a pattern shirt that doesn’t include blue, good luck. Look at the shirt below. It goes well with tan or brown pants, but I can’t find anything like it anywhere! For such a basic style, this really surprises me.
Here’s a close-up showing the pattern:
So, the moral of the story is if you find an article of clothing you like, purchase another two of them right away, because there’s no guarantee it will be available (or of the same quality) in a couple of years when you’ll be wanting to replace it with something comparable.
After years of searching and hypothesizing, we have finally discovered a macroscopic object passing through our solar system that came from interstellar space! An elongated rocky object with approximate dimensions 755 × 115 × 115 ft. entered the solar system from the direction of the constellation Lyra at a velocity (v∞) of 26 km/s (16 mi/s or 58,000 mph), and will exit the solar system at essentially the same speed in the direction of the constellation Pegasus, within the Great Square.
This interstellar object (ISO) is called 1I/2017U1 ‘Oumuamua. What’s in a name? A lot! Let’s separate the three different parts of this designation, discussing each in turn.
1I – “I” stands for “interstellar” and “1” indicates that it is the first interstellar solar system visitor discovered.
2017U1 – indicates that it was the first object discovered during the half-month October 16-31 in the year 2017.
‘Oumuamua [pronunciation] is a Hawaiian word for “scout”, reflecting how this object is like a scout or messenger reaching out to us from the distant past.
‘Oumuamua Enters the Solar System
Here’s a brief timeline of the encounter.
September 9, 2017 – Closest approach to the Sun (0.26 AU)
October 14, 2017 – Closest approach to the Earth (0.16 AU)
October 19, 2017 – Discovered by Robert Weryk with Pan-STARRS
It is very difficult for us to discover objects coming towards us from the inner solar system and the glare of the Sun, so it is not surprising that ‘Oumuamua was discovered after it had passed by the Earth on its way out of the solar system.
‘Oumuamua in the Inner Solar SystemNASA Animation Showing ‘Oumuamua’s Journey Through the Inner Solar System‘Oumuamua Exits the Solar System
Rob Weryk, a post-doc at the University of Hawaii Institute for Astronomy, discovered ‘Oumuamua in images taken by the Pan-STARRS1 1.8-meter Ritchey–Chrétien telescope at the summit of the dormant volcano Haleakalā on the island of Maui. Pan-STARRS is an acronym for “Panoramic Survey Telescope and Rapid Response System” and is primarily used to search for Near Earth Objects (NEOs). It has been estimated that Pan-STARRS should be able to detect an interstellar object like ‘Oumuamua passing through our solar system about once every 5 years.
But the 8.4-meter Large Synoptic Survey Telescope (LSST) in Chile, which will see first light in 2020, is expected to be able to detect at least one interstellar object passing through our solar system each year.
While we don’t know ‘Oumuamua’s place of origin, we do know that it originated outside our solar system, and that is exciting. Was it ejected from a binary system? Or through a chance encounter with a giant planet in its outer solar system? Is it an “extinct” interstellar comet? Perhaps it is a former asteroid of a dying star. Even our own Sun, which is expected to reach a peak luminosity of 5200 L☉ as a red giant star in a few billion years, will lose mass and transition to a white dwarf, causing a dynamical reshuffling that will eject a large number of asteroids, trans-Neptunian objects, and comets from our solar system (Seligman & Laughlin 2018). Perhaps ‘Oumuamua long ago suffered a similar fate.
A detailed astrometric study (ground-based and HST) of ‘Oumuamua’s trajectory through the inner solar system has revealed a small non-gravitational acceleration component directed radially away from the Sun (Micheli et al. 2018). After ruling out other known gravitational and non-gravitational accelerators, the authors conclude that the most probable explanation is cometlike outgassing, though ‘Oumuamua displayed no detectable coma during its all-too-brief apparition. Furthermore, no change in the rotational state of ‘Oumuamua occurred during the month-long interval over which it was observed. If the anomalous acceleration away from the Sun was caused by cometary activity, a measurable effect on ‘Oumuamua’s rotation should have been seen (Rafikov 2018).
‘Oumuamua wasn’t discovered until 40 days after perihelion, and Zdenek Sekanina, JPL, argues that it is a dwarf interstellar comet that disintegrated before perihelion, so that during the period of observation it was an extremely low density debris plume whose orbital motion was affected by solar radiation pressure and not outgassing (Sekanina 2019). As such, he notes the difficulty in trying to reconstruct its original shape and place of origin.
Could there be some other cause of the anomalous acceleration? It is worth considering that ‘Oumuamua might be of artificial origin (Bialy & Loeb 2018) . It could be a lightsail that long ago was ejected from its solar system of origin, and this interstellar debris just happened to encounter our solar system. Or, perhaps, it is (or was) an operational space probe purposefully directed towards Earth’s vicinity by an alien civilization. Incidentally, no radio emissions were detected from ‘Oumuamua (yes, we looked).
There may yet be some other explanation for the acceleration ‘Oumuamua experienced during its journey through our solar system. Our experience with the Pioneer anomaly (now explained), or the still unexplained flyby anomaly, might lead us towards new insights. The possibility that ‘Oumuamua is a highly elongated or flattened object only adds to the mystery.
References
Bialy, S., Loeb, A. 2018, ApJL, in press (arXiv: 1810.11490)
McNeill, A., Trilling, D. E., Mommert, M. 2018, ApJL, 857, L1 (arXiv:1803.09864)
Micheli, M., Farnocchia, D., Meech, K.J., et al. 2018, Nature, https://www.nature.com/articles/s41586-018-0254-4
Rafikov, R. R. 2018, arXiv preprint 1809.06389
Sekanina, Z. 2019, arXiv: 1901.08704)
Seligman, D. & Laughlin, G. 2018, AJ, in press (arXiv:1803.07022)
I first became familiar with British composer, musician, and music presenter extraordinaire Howard Goodall on August 7, 2017, when his documentary Sgt. Pepper’s Musical Revolution aired on Wisconsin Public Television. As a lifelong Beatlephile who knows a thing or two about the Beatles and their music, I was immensely impressed with the quality and content of this documentary. I especially liked his detailed analysis (vis-à-vis Alan W. Pollack) of what makes the music of the Beatles so extraordinary, and his obvious enthusiasm for the subject. After watching this wonderful hour-long (yes, no commercials!) programme, I vowed to do two things:
Purchase an official DVD copy of Sgt. Pepper’s Musical Revolution
Find out more about Howard Goodall and his work
#1 Sad to say, periodic searches have only turned up bootleg copies from questionable sources. When will the DVD finally be released?
#2 Somehow I missed it when it was originally broadcast on PBS, but I was delighted to find Howard Goodall’s Big Bangs available through Netflix, so I recently ordered it.
First broadcast in the UK in the autumn of 2000, Howard Goodall’s Big Bangs is a series of 50-minute documentaries on five transformative developments in the history of Western music. They are
Notation
Equal Temperament
Opera
The Piano(forte)
Recorded Sound
I just finished watching this series, and would highly recommend it for anyone interested in music history.
I enthusiastically look forward to other music documentaries by Howard Goodall. After watching Sgt. Pepper’s Musical Revolution, I believe that he may well be the best person in the world to develop an entire documentary series on the music of The Beatles. Here’s hoping!
There are those who say that if music has mass appeal it can’t also be music of great significance or depth. What The Beatles proved once and for all is that this idea is hopelessly and absurdly wrong. – Howard Goodall
There are very, very few composers in history whose work changed all the music that followed it: Beethoven was one, Wagner was another. I believe that posterity will add to their select ranks The Beatles. – Howard Goodall
The galaxy pair M81 and M82 in Ursa Major must rank near the top of the list of best-loved objects for any Northern Hemisphere amateur astronomer. So, to see such a familiar object as these in breathtaking Hubble Space Telescope detail is thrilling indeed:
Messier 81 from the Hubble Space Telescope – click on the image for a larger viewMessier 82 from the Hubble Space Telescope – click on the image for a larger view
M81 and M82 lie little more than a moon-width apart in the constellation Ursa Major, 11.8 million and 11.5 million light years, respectively, from Earth. Check out this pretty pair with either binoculars or a telescope any clear evening during the next few days. Both galaxies transit the meridian on April 14 at the end of evening twilight, so this is the perfect time to observe them at their highest in the sky. You can find Bode’s Galaxy (M81) and the “Silver Sliver” (M82) by drawing an imaginary diagonal across the bowl of the Big Dipper, opposite (rather than along) the handle, and extending the diagonal beyond the bowl almost as far as the two bowl stars are apart. Or, using the chart I created below, draw an imaginary line between Dubhe and 24 UMa, then go about four-fifths of the way to 24 UMa. M81 & M82 lie about 0.4° (a little less than a moon-width) perpendicular to that line on the Polaris side. Bingo, you’ve got ’em!
Saturn’s third largest moon, Iapetus (eye-AP-eh-tuss), was discovered at the then-new Paris Observatory in 1671 by Italian-French astronomer (and observatory director) Giovanni Domenico (Jean-Dominique) Cassini (1625-1712). Upon further observation, Cassini noted that he could only see Iapetus when it was on the west side of Saturn, never the east. His telescope was not large enough to detect Iapetus on the east side of Saturn because it was much fainter then. He correctly reasoned that, “it seems, that one part of his surface is not so capable of reflecting to us the light of the Sun which maketh it visible, as the other part is.” He also must have realized that Iapetus was locked in synchronous rotation—as is our Moon—with the same side facing Saturn all the time, with its rotation period being equal to its orbital period. Today we know these periods to be 79.3215 days.
The leading hemisphere of Iapetus has a visual albedo of only about 5%, whereas most of the trailing hemisphere is much brighter, having an albedo around 25%. Thus, when Iapetus is on the west side of Saturn, its apparent visual magnitude is around 10.2, but on the east side of Saturn Iapetus is 1.7 magnitudes fainter at 11.9. Without a doubt, Iapetus is one of the most outlandish places in the solar system, and the Cassini Saturn orbiter flybys certainly amplified the strangeness.
Cassini made one close targeted flyby of Iapetus on September 10, 2007, passing within 762 miles of the surface. Here are a few of the best photos of Iapetus from Cassini.
The first high-resolution glimpse of the bright trailing hemisphere of Saturn’s moon IapetusThis is a raw, or unprocessed, image taken by the Cassini spacecraft during its close flyby of Saturn’s moon Iapetus on Sept. 10, 2007 showing its prominent equatorial ridge—still a mysteryThe “Himalayas” of IapetusThe Transition ZoneClosest View of IapetusDark material splatters the walls and floors of craters in the surreal, frozen wastelands of IapetusMay 30, 2017 – Cassini bids farewell to Saturn’s yin-and-yang moon, Iapetus
The dark material appears to have been deposited from elsewhere in the Saturnian system, but sublimation of water ice may also play a role. In any event, the dark material is a relatively thin veneer, significantly less than a meter thick in many places.
The warm day on Iapetus sees a surface temperature of -227° F on the dark terrain and an even colder -256° F on the bright terrain. Inhospitable, to say the least!
Currently, Polaris (Alpha α UMi) shines at magnitude 2.0 and lies just 0.7° from the North Celestial Pole (NCP). Precession of the Earth’s rotation axis will bring the NCP to within 0.5° of Polaris in March 2100, its minimum distance.
The situation for the South Celestial Pole (SCP) is not such a happy circumstance. The nearest naked-eye star to the SCP at present is neither near nor bright. Sigma Octantis at magnitude 5.5 is not easy to see with the unaided eye, and being 1.1 degrees away from the SCP doesn’t win it any awards. Besides, precession is moving the SCP farther away from Sigma Oct, not nearer.
One wonders, will precession someday bring us a south celestial pole star worthy of the name? Even, perhaps, comparable to Polaris? Here’s what our stargazing descendants can look forward to:
Cha = Chamaeleon; Car = Carina; Vel = Vela
So, around 8100 A.D. Iota Carinae and around 9220 A.D. Delta Velorum will serve admirably as southern pole stars every bit as good as Polaris does now in the northern hemisphere.
Now, for the northern hemisphere…
Cep = Cepheus
Up until the year 10,000 A.D., no northern pole star will be as good as Polaris is now, though 4.8-magnitude 9 Cephei will be very close to the north celestial pole around 7400 A.D.
Thought you might enjoy seeing what deep sky objects will come close to the celestial poles, so those are listed in the above tables as well.
I am so very proud of what hundreds of thousands of Americans of all ages did today, marching in hundreds of anti-gun-violence rallies all across our nation. I’m especially proud of the students. We had a huge group of marchers in Mineral Point, Wisconsin (students included), and I was glad I participated.
I do not want to live in a country where everyone is armed to the teeth. You know, you have to decide what kind of a world you want to live in and then work towards that goal, no matter how difficult.
Paul McCartney at a March for Our Lives event in New York City
I was devastated and angry when John Lennon was shot to death in New York in 1980 outside his apartment building by a very disturbed man (it is almost always a man, isn’t it?). I mean, who the hell would kill a musician? I will never get over it. On that day (and many times since), I decided “enough is enough”. Gun ownership should be a privilege that has to be earned, not a right. And weapons of war do not belong in the hands of private citizens—ever. If that involves repealing the Second Amendment to the United States Constitution, then so be it. But “we the people” never get a chance to vote on gun issues, do we?
If gun owners in this country can’t support much stricter and sensible gun laws, then maybe we should peacefully go our separate ways. Gun lovers can have their country (a dystopia, really), and the rest of us can live somewhere else. I would support a civil separation, but never a civil war. (Besides, we know which side has most of the guns.)
“The young do not know enough to be prudent, and therefore they attempt the impossible, and achieve it, generation after generation.”
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 physical explanatory power of inflation in terms of structure formation, supported by the observational data on the fluctuation spectra, is spectacular. For most physicists, this trumps the lack of identification and experimental verification of the underlying physics. Inflation provides a causal model that brings a wider range of phenomena into what can be explained by cosmology, rather than just assuming the initial data had a specific restricted form. Explaining flatness (Ω0 ≅ 1 as predicted by inflation) and homogeneity reinforces the case, even though these are philosophical rather than physical problems (they do not contradict any physical law; things could just have been that way). However claims on the basis of this model as to what happens very far outside the visual horizon (as in the chaotic inflationary theory) results from prioritizing theory over the possibility of observational and experimental testing. It will never be possible to prove these claims are correct.
Inflation is one compelling approach to explaining the structure we see in the universe today. It is not necessarily the only one, but it currently has the most support. Basically, a tiny fraction of a second after the Big Bang, the universe expanded dramatically. Around 10-36 seconds after the Big Bang the universe had a diameter on the order of 1.2 × 10-27 meters. To put that size in perspective, the diameter of a proton is between 0.84-0.87 × 10−15 meters. So, when inflation began, the entire universe had a diameter almost a trillion times smaller than a single proton! 10-34 seconds later when the inflationary period was coming to an end, the size of the universe was a little over half the distance to Alpha Centauri!
The basic underlying cosmological questions are:
(1) Why do the laws of physics have the form they do? Issues arise such as what makes particular laws work? For example, what guarantees the behaviour of a proton, the pull of gravity? What makes one set of physical laws ‘fly’ rather than another? If for example one bases a theory of cosmology on string theory, then who or what decided that quantum gravity would have a nature well described by string theory? If one considers all possibilities, considering string theory alone amounts to a considerable restriction.
(2) Why do boundary conditions have the form they do? The key point here is, how are specific contingent choices made between the various possibilities, for example whether there was an origin to the universe or not.
(3) Why do any laws of physics at all exist? This relates to unsolved issues concerning the nature of the laws of physics: are they descriptive or prescriptive? Is the nature of matter really mathematically based in some sense, or does it just happen that its behaviour can be described in a mathematical way?
(4) Why does anything exist? This profound existential question is a mystery whatever approach we take.
The answer to such questions may be beyond the limits of experimental science, or even beyond the limits of our intellect. Maybe, even, these questions are as meaningless as “What lies north of the north pole?1” because of our limited intellect. Many would claim that because there appears to be limits to what science or human intellect can presently explain, that this constitutes evidence for the existence of God. It does not. Let’s just leave it as we don’t know.
Finally, the adventurous also include in these questions the more profound forms of the contentious Anthropic question:
(5) Why does the universe allow the existence of intelligent life?
This is of somewhat different character than the others and largely rests on them but is important enough to generate considerable debate in its own right.
Well, a seemingly flippant answer to this question is we wouldn’t be here if it didn’t, but that begs the question. Perhaps intelligent life is the mechanism by which the universe becomes self-aware, or is this just wishful thinking? In the end, I am willing to admit that there may be some higher power in the universe—in the scientific pantheist and humanist sense—but I will stop short of calling that “God” in any usual sense of the term.
The status of all these questions is philosophical rather than scientific, for they cannot be resolved purely scientifically. How many of them—if any—should we consider in our construction of and assessments of cosmological theories?
Perhaps the limitations of science (and, therefore, cosmology) is more a manifestation of the limitations of our human intellect than any constraint on the universe itself.
One option is to decide to treat cosmology in a strictly scientific way, excluding all the above questions, because they cannot be solved scientifically. One ends up with a solid technical subject that by definition excludes such philosophical issues. This is a consistent and logically viable option. This logically unassailable position however has little explanatory power; thus most tend to reject it.
Let’s call this physical cosmology.
The second option is to decide that these questions are of such interest and importance that one will tackle some or all of them, even if that leads one outside the strictly scientific arena. If we try to explain the origin of the universe itself, these philosophical choices become dominant precisely because the experimental and observational limits on the theory are weak; this can be seen by viewing the variety of such proposals that are at present on the market.
And let’s call this metaphysical cosmology.
1Attributed to Stephen Hawking
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]
Ryden, Barbara. 2003. Introduction to Cosmology. San Francisco: Addison Wesley.
We are all going to miss Stephen Hawking. His incredible intellect, and his even more remarkable determination to make something of himself despite a terrible affliction, has been a universal inspiration all over the world. Stephen Hawking was the individual equivalent of the Apollo lunar program. He raised the bar when almost everyone else we see nowadays is lowering it. He succeeded against all the odds.
Now would be a good time to watch (or rewatch) five extraordinary documentaries and films about Stephen Hawking and his ideas.
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 June 21, 2017 and October 20, 2017. The component events are presented chronologically as follows:
UT Date
6-21-2017
8-15-2017
9-4-2017
9-5-2017
9-12-2017
10-20-2017 (2 satellites)
You’ll notice that sometimes the satellite crosses the field as a moving “dash”. That’s because sometimes I used longer exposure times to record a fainter target 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 video clip, you’ll see a slow-moving “tumbler” satellite moving from right to left across the top of the field.
UT Date
8-25-2017
Target Star
Tycho 676-828-1
Asteroid
179462 (2002 AJ202)
On January 10th of this year, I figured out how to identify satellites crossing the telescope field of view using the amazing program Guide 9.1, which I use for all my observatory research work. On March 4th, I was hoping to be the first to record the asteroid 3706 Sinnott passing in front of a star. This asteroid is named after Sky & Telescope Senior Editor Roger Sinnott, whom I had the good fortune to work with in writing the article “A Roll-Down-Roof Observatory” in the May 1993 issue of Sky & Telescope, p. 90. Roger is amazing. He took an article that I had written and edited it in a way that only lightly touched my original text yet ended up saying what I wanted to say even better than I was able to say it myself. The mark of a great editor! Anyway, I’m sure Roger remembers me and I was looking forward to giving him the news that I had observed the first stellar occultation by “his” asteroid. Alas, it was not to be, because, as so often happens, the too-faint-to-be-seen asteroid passed either above or below the target star. The consolation prize, however, was recording a third stage Long March Chinese rocket booster (CZ-3B R/B; NORAD 43004U; International # 17069D) passing through the field. This rocket launched on November 5, 2017, and added two satellites to China’s Beidou positioning network. As you can see in the light curve below, the rotation period of the rocket booster is a bit longer than the 19 seconds of usable video I had.
UT Date
3-4-2018
Target Star
UCAC4 556-42881
Asteroid
3706 Sinnott
Once in a great while, I record a telescopic meteor. Here are two.
UT Date
7-15-2017
3-4-2018
Target Star
Tycho 6269-2747-1
UCAC4 561-14746
Asteroid
17136(1999 JE82)
6890 Savinykh
References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21
