Archive for the ‘Astronomy’ Category

Astrology Ontology

October 22, 2022

Astronomy uses people to explain the stars.

Astrology uses the stars to “explain” people.

(Anon)

Many amateur astronomers, myself included, have enjoyed Quasar Publishing’s annual Astronomy publication. Astronomy 2023 includes an article titled Astrology – the First Astronomers which at least in some forums, has generated some discussion.

The one page article talks a bit about the historical context of astrology as predating astronomy, its focus on the constellations that the Sun appears to pass through – the zodiacal constellations – due to the Earth’s annual trek around the Sun, and that the Earth’s slow wobble about its axis leads to the so-called precession of the equinoxes that has changed the zodiac’s constellation-occupying date ranges.

The article also talks about some well-known figures in the history of Science have practiced astrology including Galileo, Tycho Brahe, Ptolemy. As did Kepler, who also believed that there was some relationship between the platonic solids and planetary spacing. Today, we revere him for his Three Laws of Planetary Motion, investigations into optics, measuring the volume of wine barrels, and an early Science Fiction story (Somnium). He, like many early scientists, was on the cusp of the old and new ways. Think also of Newton, who was an alchemist. It’s easy for us to see the many ways in which they were in error now, given our historical perspective and educational good fortune.

The Astronomy 2023 authors comment on the aspect of the day of a person’s birth in relation to the Sun’s position at that time as used in “newspaper horoscopes”, and follow on with this:

Astrologers have clearly defined methods on how to create such charts, but the problem is the validity of their initial assumptions to start with. From a scientific basis, it has never been demonstrated how the arrangement of these distant bodies can influence individual’s characteristics.

So far, so good.

Earlier in the article we have this:

This article is not a criticism of astrology, but more spelling out the differences between astronomy and astrology.

That’s also fine as far as it goes. They continue with:

A bit like how science cannot be used to disprove God (whichever version) or in this case, astronomy disprove astrology.

It’s true. The existence of gods is not susceptible to proof or disproof. I’m not going to lose sleep over this or the infinity of other things we can’t prove or disprove. As an aside, the word prove shouldn’t be bandied around so much. The only things that can be proven are mathematical theorems. Science doesn’t prove things: it gathers more and more evidence in favour of a particular hypothesis or against some other.

The article follows on with:

They are just different. Astrology and religions are belief systems which are effectively non-falsifiable…this means there is no test known (or perhaps even possible?) that would disprove a concept. By religions, we include all the gods, including those that used to be worshiped by the ancient Mediterranean and Middle East cultures, responsible for the mythological figures immortalized in today’s constellations.

To be honest, by the time I had tossed around the content of the article, the initial knee-jerk reaction of “why the heck is there anything about astrology in Astronomy 2023?” had given way to: “how could the article be improved?”

My main feedback to the authors is that we need to be careful not to encourage the perception that all forms of knowledge are equal. Having an opinion isn’t enough, especially for things that matter in some important way. It’s okay to criticise ideas and systems of belief. More than that, we must criticise ideas because otherwise no progress can ever be made! Sometimes ridicule is also valid, in the case of truly toxic belief systems. Kinder, constructive criticism is better. Let’s face it: we’ve all had bad ideas.

The authors do make the point that belief of the astrological and religious kind are not falsifiable. They also mention that astrological assumptions and mechanisms are suspect.

Perhaps the case could have been made even more clearly by saying that systems of belief such as astrology and religion have no predictive or explanatory powers, whereas Scientific theories do, and further that the latter are open to question and revision. That’s not to say that Science is not a human process. There’s ego and politics aplenty. But the Method wins in the end.

I would also suggest that if all someone does when reading their daily horoscope is to have a laugh, then there’s nothing to worry about. If astrology or religion leads to important life decisions, then I think it is more than reasonable to apply a bit more scrutiny.

To prefer the hard facts over our dearest illusions, that is the core of Science. 

(Carl Sagan commenting upon Johannes Kepler)

Waiting for Artemis 1…

August 29, 2022
source: nasa.gov

I’m currently watching NASA TV waiting for the launch of Artemis 1, the first test of NASA’s Space Launch System (SLS) and the Orion crew capsule, albeit unmanned this time with “crash test dummies”, mannequins that will be used to measure forces and radiation, and the first mission to the Moon of its kind for 50 years, since Apollo 17 in 1972.

There was an unplanned hold at 40 minutes before launch due to an operating temperature problem in engine #3.

There are a couple of launch opportunities in early September if today’s launch is cancelled.

This is an important precursor test mission for Artemis 2, a crewed mission scheduled for 2024 that will orbit the Moon and return its astronauts to Earth, Apollo 8 style, before the first crewed landing mission, Artemis 3, in 2025, 53 years after Apollo 17 and 56 years after Apollo 11.

I must admit that life keeps me pre-occupied enough that I wasn’t thinking about this much again until recently. For someone who remembers being sent home from school, even as a 5 year old boy, to watch Apollo 11 on the family B&W TV along with the blurry pictures of Neil Armstrong on the ladder of the LEM, and as a lifelong fan of spaceflight, manned and robotic, the fact that Artemis (the twin of Apollo) is happening seems just a bit special.

NOTE: While writing this, the Artemis 1 launch was scrubbed for today. The next earliest possible launch date is September 2nd, pending the outcome of the analysis of test data from today’s engine problem. Here’s hoping!

EDIT: More than 2.5 months after I wrote this post (Aug 29 2022), Artemis 1 has finally launched!

VStar Citations and other References

August 14, 2022

The purpose of this post to maintain a list of publications and other direct references to VStar.

At the time of writing, 23 papers in the following journals cite the use of VStar:

  • The Journal of the American Association of Variable Star Observers
  • Research Notes of the American Astronomical Society
  • Publications of the Astronomical Society of Australia
  • Open European Journal on Variable stars
  • Acta Astronomica
  • arXiv (open-access archive)

The 2012 Algorithms + Observations = VStar” JAAVSO paper is currently the suggested way to cite use of VStar (as per the main AAVSO VStar page), although a CFF citation entry on GitHub or software publication DOI may be recommended as an alternative in future.

In the videos section, John Percy is author of the 2007 text book, Understanding Variable Stars.

Web

Publications

Videos

U Sco update

June 8, 2022

Within a day, the nova reached a peak magnitude of 7.8, then dropped two magnitudes, becoming around 5 times dimmer in actual brightness (magnitude is logarithmic).

The AAVSO Alert Notice details the decline of the last outburst over a few months and flares with an amplitude of around half a magnitude that began several days after the peak, for which the mechanism is unknown.

Outburst of the Recurrent Nova U Sco

June 8, 2022

In late September 2021, I wrote about the recurrent nova U Scorpii: Waiting for U Sco and Waiting for U Sco: nearby gamma ray transient detected.

The last image I took of the region around U Sco in September showed no sign of it, but within the last day it has undergone an outburst, and appears to have quickly peaked, as per previous events (the last being in January 2010) before declining again. The nova reached a visual magnitude of 7.8 on June 7 2022 up from its usual magnitude 18 or thereabouts, a difference in brightness of around 25 times (each magnitude being a factor of 2.512 brighter than the whole number magnitude on either side of it). As I write, U Sco has declined to around magnitude 8.4.

The light curves show the current and 2010 outburst, and a close up of the current outburst. It’s interesting note that there appears to have been some evidence of an increase in magnitude in the few months leading up to the outburst.

I took a DSLR image of the region around the nova tonight. U Sco is marked with a red arrow.

While I don’t have images that are suitable for DSLR photometry from tonight (the sky was less than ideal), nor did I have the chance to make a visual (binocular or telescope) observation, from the image I estimate the nova’s magnitude to be around 8.4 (magnitude 8.3 and 8.6 comparison stars are marked with green arrows), which is consistent with the current photometry in the AAVSO International Database.

The following images show the U Sco region tonight (June 2022) and late last September for comparison, in different sky conditions and positions on the sky. The second image has been rotated to match the current event’s sky rotation. Flicking up and down between the images will help reveal the nova, aided by the arrowed image above if necessary.

June 2022 outburst (5 seconds, ISO 800, f2.0, Canon 1100D)
U Sco region in late September 2021 (3 seconds, ISO 800, f2.0, Canon 1100D)

For more information about recurrent novae, I gave a talk in early September 2021 to ASSA about another recurrent nova RS Oph. See also this AAVSO forum page regarding the current outburst.

EDIT: Here is the AAVSO alert notice: https://www.aavso.org/aavso-alert-notice-779

Making sense of variable star observations

February 23, 2022

I recently gave a talk via ASSA@Home about making the connection between variable star observations (from the AAVSO International Database and Kepler mission) with the processes in the star systems themselves.

I gave examples of pulsating variables (Chi Cyg, RS Pup, RR Lyr, T Umi), an Algol type eclipsing binary (ASAS J035812+1629.7), the enigmatic luminous blue variable eta Car, and the recurrent nova RS Oph, showed videos linking light curves with stellar processes, inspected time series observations, created phase plots and carried out analyses such as period search and time-frequency analysis using VStar.

While not as polished and more ad hoc and exploratory than last year’s RS Oph recurrent nova eruption talk for ASSA, it was fun and seemed to be appreciated, despite less than best audio and video at times. It’s also not easy watching yourself give a talk. 🙂

Waiting for U Sco: nearby gamma ray transient detected

September 29, 2021
The Fermi Gamma-ray Space Telescope (source: NASA)

Two days ago I wrote Waiting for U Sco. Today, here are a few excerpts from ATel #14941 (The Astronomer’s Telegram):

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has detected a new transient gamma-ray source, Fermi J1623-1752.

A possible counterpart to the LAT transient is the recurrent nova U Scorpii with position offset by 0.18 deg from the LAT position, thus just outside the 95% confidence error circle, but within the 99% confidence error circle. U Sco has a known recurrence interval of 10.3 years (Schaefer 2010, ApJS, 187, 275) prior to its outburst in January 2010, thus a new outburst from U Sco could be anticipated. The last observation of U Sco in the AAVSO lightcurve database was on 2021 Sep 19.

Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source, we encourage multi-wavelength observations, particularly optical follow-up of U Sco.

ATel #14941

I read about this in a post by Alexandre Amorim (Brazil) in the AAVSO novae forum. Robert Fidrich (Hungary) soon followed up with an iTelescope observation to say that there was no eruption visible.

Given that U Sco almost certainly had an outburst in its “seasonal gap” (unobservable due to position on the sky), probably in 2017, what this current gamma ray event means seems pretty uncertain.

I’ll continue imaging the U Sco region until it’s too low tonight (in between the clouds) and, consistent with my last post, whenever I can thereafter.

Waiting for U Sco

September 27, 2021

When the recurrent nova U Sco goes into outburst again, the image below shows where it will appear (see cross-hair style position marker), with the bright star Antares, and those bracketing it, shown for reference:

source: Stellarium

Zooming in shows two stars to the right of the nova position marker. Looking at previous outbursts, U Sco’s peak brightness should be somewhere between these two (around magnitude 7.5 to 8, so a binocular or small telescope object).

source: Stellarium

I’m taking images from my backyard of the U Sco region when I can. The image below (click it to enlarge) was taken on Sep 10 2021. I’ve taken a few since but want to step up the regularity. The red arrow shows where U Sco will appear and the green arrow shows the two stars pointed to above.

In any case, I won’t have the same cause to complain about missing the next outburst of U Sco that Leslie Peltier did about missing the T CrB outburst in 1946 (as related near the end of a recent talk I gave about RS Oph), given that my observing frequency is likely to be less and over a much shorter timeframe.

Addendum: Having said all this, given that there was almost certainly an unobserved eruption in the 2017 seasonal gap, as announced in a March 2019 AAVSO forum post, what does this imply for the prediction made by Brad Schaefer of 2020+/-0.7 in a paper published in June 2019? And yet, see the next post…

The Crab Nebula

September 25, 2021

We live only a few conscious decades, and we fret ourselves enough for several lifetimes.

(Christopher Hitchens)

I recently gave a 5 minute talk to a non-technical group about the Crab Nebula (M1, the first object in Charles Messier’s catalog) that related to a sense of wonder in Science. I thought the brief content was worth sharing here.

Chinese astronomers in 1054 witnessed a “guest star”, an explosion that gave rise to a remnant several light years wide called the Crab Nebula.

The object is several thousand light-years distant from earth, yet visible in a small telescope, although with nothing like the detail shown in the Hubble Space Telescope image of Figure 1!

Figure 1: The Crab Nebula, a Hubble Space Telescope image mosaic (source: NASA)

At the heart of the nebula is an object composed only of neutrons, a spoonful of which would weigh a billion tonnes, spinning 30 times per second, energising the nebula, wave-like rings expanding outward from the centre like ripples in a pond (Figure 2).

The original star ran out of the elements that had sustained its nuclear fusion for millions of years, its core collapsing then rebounding in a fraction of a second, ending as a supernova explosion.

Figure 2: The central region of the Crab Nebula (source: NASA)

The event synthesised elements heavier than iron that spread out into the space between the stars, to be incorporated into new stars and their planetary systems, some perhaps going on to develop life.

The iron in our blood, along with trace elements like zinc and iodine, come from such stars.

So, not only are we star-stuff, as Carl Sagan liked to say, but in fact we owe our existence to massive stars that burned bright and lived short lives (millions vs the billions of years our sun will last) then died, so that we could live for just a few decades.

RS Ophiuchi Decline Continues

August 16, 2021

The expected decline of the recurrent nova RS Oph continues, almost 3 magnitudes in 7 days. I’ve managed only 5 observations with a couple of cloudy nights between the last two. Luna at 60% illumination in nearby Scorpius tonight made estimating its magnitude (7.2) in 7×50 binoculars a little trickier tonight.