Archive for the ‘Variable Stars’ Category

Possible Nova in Sagittarius

April 6, 2021

Western Australian amateur astronomer Andrew Pearce has discovered a possible nova (PNV J17581670-2914490) in Sagittarius on April 4. At that time its visual magnitude was around 8.8.

Andrew reported in a message to Variable Stars South today that the object has been classified via spectroscopy as a classical nova.

The nova’s visual magnitude is currently around 8 or a little brighter. As always with these objects, it will be interesting to see how bright it gets.

Here is a finder chart suitable for binoculars (something of a challenge at the current brightness in 7x50s):

Rotating this finder chart a bit more than 90 degrees anti-clockwise will roughly match this image from Stellarium at around midnight AEST.

Zooming out gives more positional context:

Further out still shows even more familiar landmarks in Sagittarius and Scorpius.

I have yet to observe or image the nova but hope to do so over the next few days.

EDIT: After writing this I went out and had an initial look at the area. It was after midnight and the nova was in a good position from my backyard. I was just able to glimpse it in 7×50 binoculars but not well enough to make an estimate. So I took a few quick untracked shots of the region from which it appears that it’s probably around magnitude 7.8 (visual) which is consistent with what I glimpsed through binoculars.

I’ll keep an eye on it over the next few nights and hopefully take some better images.

EDIT: the weather did not improve early enough while the nova was still bright enough for me to observe.

Dad’s old Mac and DSLR photometry

September 29, 2020
Photo by Junior Teixeira on Pexels.com

After upgrading my MacBook to macOS Catalina, WINE stopped working, because 32-bit applications were no longer permitted to run. I had been using WINE to run the Windows IRIS program for image processing and DSLR photometry as part of my minimalist approach.

After my father died in January this year, his older MacBook was passed on to me. It still has Yosemite as the OS, so WINE & IRIS work fine on it!

Given all the times we spent talking about astronomy, the special time we shared watching the 2001 Leonids under a dark country sky, and the “help desk” support I tried to give him over the phone, I know that dad would approve of my use of his old computer in this way.

Certainly better than having it sit idle.

Thanks dad.

Photo by David Besh on Pexels.com

Nova Ret 2020 Update #2

July 24, 2020

As of July 24 2020, there are more than 100 Nova Ret 2020 observations, most visual, with a handful of CCD submissions. Mine (visual) are shown in purple.

Most observers are from Brazil (10), then Bolivia and Australia (5 each), with one from Italy and South Africa.

The southerly declination of the target and comparison stars in Reticulum (almost -55o degrees) makes northern hemisphere observations difficult.

A linear fit shows an overall decline of around 0.17 magnitudes per day, but there’s a lot of spread in the data and novae are unpredictable.

Nova Ret 2020 Update

July 18, 2020

The sky was largely cloudy at 5:45 this morning but a short-lived clear patch permitted a quick observation. The nova’s magnitude was between the 4.6 and 5.0 comparison stars in Reticulum (X25537DR chart), so around magnitude 4.8.

The AAVSO alert notice was issued a couple of days ago.

In my last post, I included a Stellarium screenshot of the field around the nova and Reticulum. Here’s a couple more for better context:

An hour later, I took another quick shot of the dawn NE sky showing the Moon, Venus and cloud (0.6 sec, ISO 200, f 2.0, unprocessed):

Nova in Reticulum!

July 17, 2020

Rob McNaught at Siding Spring, Coonabarabran, NSW found a magnitude 5.3 object in the constellation Reticulum on July 15 2020.

MGAB-V207’s pre-brightening magnitude was 15.8 (Johnson V). Just before I wrote this, it was designated N Ret 2020 in VSX and the AAVSO International Database.

I observed the nova at around 5:30am this morning (July 17) in 7×50 binoculars. My estimate, based upon 4.95 and 5.45 visual magnitude comparison stars, was 5.2.

It may have been brighter but that was my best estimate, given the seeing quality at the time, and a lack of coffee. Having said that, I’m confident that it was reasonable.

At the time of my submission to AAVSO this morning, there were 6 observations, including mine. Andrew Pearce in WA submitted his second observation (brighter) soon after mine.

This is the first bright nova since 2018! So I’m a little bit excited.

To get familiar with the field, I started with Stellarium:

and this AAVSO finder chart, which needs to be rotated by about 45 degrees anti-clockwise to match the Stellarium view:

In general, the sky was lovely this morning. After estimating the nova’s brightness, when the dawn became evident, I took this quick shot of a conjunction of the crescent Moon, Venus, and Aldebaran (alpha Tauri) low in the NE sky (1/5 sec, ISO 200, f 2.0, unprocessed) with our recently pruned walnut tree (thanks Karen!) visible at upper right:

Between the nova, satellites passing through my binocular field while observing it and the stars of Reticulum, a stray meteor, the Luna-Venus-Aldebaran conjunction, Orion rising in the east, and the general beauty of the sky, it was an uplifting start to the day.

I was again reminded that there is a hidden sky, waiting for all to see.

Variable stars and novae in particular, always reinforce to me the dynamic, constantly changing universe of which we are a small part. In what often feels like a dystopian world, especially in 2020, I find it oddly comforting that the Universe just keeps doing its thing, irrespective of us. Astronomy is a great way to get some perspective.

Current Betelgeuse Dimming Event

December 29, 2019

The semi-regular late-type variable supergiant star alpha Orionis, better known as Betelgeuse, pulsating with a period of around 420 days at a distance of 640 light years, one of the largest stars visible to the unaided eye and normally in the top 10 list of brightest stars in the sky, is currently undergoing a rapid dimming event.

betelgeuse-size-comparison-with-the-solar-system

source: ESO

If Betelgeuse was located at our sun’s position, it would engulf all the inner planets and extend out to the vicinity of Jupiter’s orbit.

When this star ends its life in a supernova explosion it will be visible in daytime and cast shadows at night.

There have been recent questions about the possibility of Betelguese going supernova (or having done so already) and whether the current dimming may be a sign of it.

ATel 13365 has this to say about the dimming event:

The current faintness of Betelgeuse appears to arise from the coincidence of the star being near the minimum light of the ~5.9-yr light-cycle as well as near, the deeper than usual, minimum of the ~425-d period.

It’s interesting to look at past observations of the star.

Here are the last 2 years of visual and Johnson V observations:

alfOri2yrs

The last 5 years of observations:

alfOri5yrs

The last 10 years of observations:

alfOri10yrs

The last 25 years of observations:

alfOri25yrs

In this and the next plot you can see the transition to image-based photometry about 50 years ago in the form of Johnson V data points.

The last 50 years of observations:

alfOri50yrs

The last 100 years of observations:

alfOri100yrs

It’s apparent that there have been similar dimming events over the last 100 years, e.g. in 1947, 1985 and other years.

alfOri100yrsWithFilterGT1.3.png

It’s not obvious that the current dimming event is significantly more rapid than others that came before it, at least by looking at the slope of a linear fit of dimming events.

Alpha Orionis is a bright star, varying between around magnitude 0 and 1.3. It’s easily observable in the north-eastern late evening sky at the moment, along with comparison stars such as Aldebaran and Pollux.

You can create a finder chart via the AAVSO website. An easier way to get started is to see pages 2 and 3 and the chart on the last page of the AAVSO Citizen Sky southern “10 star” tutorial.

The submission of observations to the AAVSO is encouraged and there’s no need for binoculars or a telescope.

AAVSO Merit Award

November 9, 2019

I was humbled recently to be a recipient of the 2019 Merit Award from the American Association of Variable Star Observers (AAVSO), having previously received The Director’s Award in 2011 and the Bill Bradfield Award from ASSA in 2012.

IMG_4406

fdf8d7ca-b612-4850-964d-671d55a5cc4f

Receiving the Merit Award at Melbourne University from AAVSO Director, Stella Kafka, Dec 10 2019

Patrick Wills also received the AAVSO Merit Award this year for his work on the AAVSO Variable Star Index, a database that VStar also uses, including the web services Patrick has created.

500 visual variable star observations

June 11, 2019

Last night’s binocular observation of eta Carinae was my 500th visual observation submission to the AAVSO International Database (AID).

eta Car BDJB 2019

An extremely modest number really, compared with other observers over a similar timeframe.

But still, somehow a nice milestone.

500th

I’ve also submitted more than 100 DSLR photometry observations to AID. Again, not many in comparative terms.

eta Car LC BV

The light curve shows the last ten years of visual and B band data along with the 169 (in purple) visual and DSLR eta Carinae observations I’ve made during that time. The red trend line shows the steady rise in eta Carinae’s brightness that has been going on for decades now.

Between VStar, work, and life in general, I don’t get a lot of time to observe these days, but I try to make each observation count.

For anyone following Strange Quarks, you will have noticed my preoccupation with other things in recent months.

Indeed, my last variable star blog post was regarding a southern nova  in March 2018.

This pre-occupation is taking its toll in various ways on me and those around me.

On Food Choices: a summary (tl;dr)

March 31, 2019

…but what is not possible is not to choose…if I do not choose, that is still a choice. (Sartre, Existentialism is a Humanism)

Given the length of the previous seven posts, here’s a summary.

The right road lost

  • The criteria we apply to food choices are: our desires, our health, what’s good for the food producer (e.g. Fair Trade), environmental impact (climate change, resource usage/degradation), and what’s good for non-human animals (animal welfare).
  • Other than our health, without which nothing much matters to us, I consider this list to be essentially in order of increasing importance.
  • Large scale animal farming is environmentally unsustainable in terms of land and water use and the resulting waste and emissions (carbon dioxide and methane). This will only get worse as the human population continues its exponential growth. A plant-based diet could significantly reduce emissions and waste.

But is it healthy?

The 2013 Australian Dietary Guidelines say that:

  • “Appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthy and nutritionally adequate.”
  • “Well-planned vegetarian diets are appropriate for individuals during all stages of the lifecycle. Those following a vegan diet should choose foods to ensure adequate intake of iron and zinc and to optimise the absorption and bioavailability of iron, zinc and calcium.”
  • “Supplementation of vitamin B12 may be required for people with strict vegan dietary patterns.”

The elephant in the room

  • It took a long time for me to accept the idea that we’re not at the centre of the universe, that there is no compelling evidence for gods of any sort, of a higher plan, of an afterlife.
  • The idea that we have a higher moral status, a greater right to be happy — to be free — than other animals is widespread, even though most of us would not be inclined to say so.
  • This idea is called speciesism. It is as if racism had been applied beyond the borders of homo sapiens.
  • Raising livestock for food involves billions of sentient animals worldwide per year being born into servitude and living lives that are nasty, brutish, and short, to borrow from Leviathan (Hobbes).
  • We need to widen our ethical circle to include other species. We do so when thinking about species loss through habitat degradation and climate change, but not necessarily when thinking about the animals we exploit.

Cultural relevance?

  • Do the desires (e.g. cultural, religious) of one or more humans outweigh the welfare — the life — of even a single non-human animal?
  • For example, it’s hard to see how the live export of cattle or sheep can be defended on cultural, religious or other grounds when we know the harm caused to individual animals.
  • And what of the shorter yet no less harrowing trip from farm to abattoir, to say nothing of what happens upon arrival?

Surplus to requirements #1

  • Caged hens as a source of eggs can’t be ethically justified unless you think that having an area no larger than a sheet of printer paper to live in, standing on wire, beak cutting to stop pecking of other hens, not being able to engage in natural behaviours are okay.
  • According to the RSPCA:
    • “In the egg industry, the sex of day-old chicks is determined at the hatchery. Sexing chicks…is done at this very early stage to determine their fate.”
    • “If strong and healthy, the female chicks remain in the hatchery, they are grown to a suitable size and then transferred to a laying facility — which could be a caged, free-range or barn set up.”
    • “Male chicks are considered an unwanted byproduct of egg production and are killed and disposed of shortly after birth.”
    • “A hen is declared ‘spent’ when her egg production drops at around 72 weeks of age. At this point she is considered less profitable and removed from the production system… Spent hens are either killed on farm and composted, or transported to an abattoir for slaughter.”
  • The treatment and fate of so-called broiler chickens and other birds such as turkeys is not something I have written about so far.

Surplus to requirements #2

  • As the RSPCA says:
    • “For cows to produce milk, they have to give birth to a calf. Most calves are separated from their mother within 24 hours of birth to reduce the risk of disease transmission to the calf, and most do not stay on the farm for long.”
    • “Separation within 24 hours of birth interferes with the development of the cow-calf bond and thus reduces separation distress. Cows will show a strong response (calling) if their calf is separated at an older age.”
    • “The term ‘bobby calves’ refers to newborn calves that are less than 30 days old and not with their mothers. Essentially, they are surplus to dairy industry requirements as they are not required for the milking herd.”
    • “Products from processed bobby calves include young veal for human consumption, valuable hides for leather, calf rennet for cheese making, and byproducts for the pharmaceutical industry.”

Asymptotic vegan

  • I would say now that I’m asymptotically approaching veganism: moving towards a plant-based diet on ethical and sustainability grounds.
  • There’s “low-hanging fruit” like meat. Then dairy and eggs. Once I got over a few psychological hurdles, leaving these behind turned out to be easier than I expected.
  • Yet there are shades of grey…
  • I have shoes with leather uppers that I purchased before my thinking changed. Should I discard them? Will that help the animal now? No. Will I buy shoes with leather uppers in future. No.
  • Last Christmas we had a turkey in the freezer with a long expiry date that had not yet been eaten. Would the “right action” have been to not consume it? If so, wouldn’t that have been a waste and wouldn’t that mean the turkey’s demise was pointless?
  • Do you care about herd immunity? You should. Will you get the yearly flu vaccine to protect the vulnerable in our society as well as yourself? Eggs are used in the process of making the flu vaccine. Having the flu vaccine involves a compromise, perhaps one we will not have to make forever if research bears fruit.
  • Do you use sweetener in your coffee? Does it contain lactose? Some do, some don’t.
  • Do you drink almond milk or otherwise consume almonds? I have not dealt with the question of bees and honey in the first seven posts, but irrespective of your thoughts on that, how are the flowers of almond (and other) trees pollinated? By bees. Do the bees just fly in and out of the orchard, or under some circumstances are they brought there, in man-made hives?
  • Do you drink wine? The fining process often uses animal products (such as milk or eggs), but there are alternatives.
  • We need to cease deliberately enslaving and killing animals, treating them as means to our ends, instead of acknowledging them as sentient creatures who like us, do not wish to suffer and moreover, who wish to be free.
  • The point is to think. To ask questions. To cast doubt on long held beliefs. To intend change, to do better. To find alternatives, to say no more often.
  • It should never be about dogma. I sometimes hear vegan activists using the phrase “convert to veganism”. That way lies religion and unjustified ideology.

On Food Choices, part 5: surplus to requirements #1

January 30, 2019

source: https://tinyurl.com/yc4vrbrh

Caged hens as a source of eggs can’t be ethically justified unless you think that having an area no larger than an A4 sheet of paper to live in, standing on wire, beak cutting to stop pecking of other hens, not being able to engage in natural behaviours, physical pain, injury and death are all okay.

Read the RSPCA’s short article Why battery cages are cruel if you think otherwise:

If you already buy cage free eggs in the supermarket, either barn or free range, you will be surprised to know that more than 11 million hens, or 70% of Australia’s hens, are still confined to a battery cage.

Hens in battery cages are constantly frustrated that they can’t do the things that come naturally to hens – spread their wings, walk freely, dust bathe, forage, lay their egg in a nest.

Battery cages cause physical pain, injury and death.

Australia is falling behind. Battery cages were phased out in the EU by 2012, and will be phased out in New Zealand from 2012. Canadian egg farmers have committed to an industry-led phase-out, while in the US, several states have either ended battery cage farming, stopped construction of further cages, or begun a phase-out.

They conclude that:

Battery cages are indefensible from a welfare point of view. The science is in, consumers and many major businesses are making the switch. It’s time for the Australian egg industry to stop clinging to the past, and catch up.

As mentioned in part 1, Karen and I have been choosing free range eggs for quite awhile now with the help of apps like CluckAR. Determining what constitutes free range and what doesn’t can be tricky though. As we’ve discovered, the number of birds and the conditions under which they are kept vary wildly under the “free range” or “cage free” banners, e.g. in a barn, out in the open.

But whether caged, barn, free range, there are two remaining problems: male chicks and “spent” hens.

Male chicks

From this RSPCA KnowledgeBase page:

In the egg industry, the sex of day-old chicks is determined at the hatchery. Sexing chicks (determining whether they are a hen or a rooster) requires considerable skill and is done at this very early stage to determine their fate.

If strong and healthy, the female chicks remain in the hatchery, they are grown to a suitable size and then transferred to a laying facility — which could be a caged, free-range or barn set up. Male chicks are considered an unwanted byproduct of egg production and are killed and disposed of shortly after birth.

Male chicks are killed for two reasons: they cannot lay eggs and they are not suitable for chicken-meat production. This is because layer hens — and therefore their chicks — are a different breed of poultry to chickens that are bred and raised for meat production. Layer hens are bred to produce eggs whereas meat chickens are bred to grow large breast muscle and legs.

It concludes with this:

The RSPCA continues to urge the egg industry to invest in alternatives…For example, research into alternatives to allow chick sex to be determined in the early egg incubation phase should be urgently progressed.

New Australian gene technology aims to do exactly that:

Recent advances in gene technology mean that it is now possible to differentiate between male and female chicks pre-hatch. This discovery provides an opportunity to improve animal production, reduce costs and eliminate ethical dilemmas in the egg laying and related industries.

An additional benefit of this technology is the potential to use the male eggs to protect people from influenza viruses. For example, human influenza vaccines are generally grown by vaccine manufacturers in fertilised chicken eggs. The pre-hatched male eggs that are no longer required by the layer industry could then be used to help produce seasonal flu vaccines.

“Spent” hens 

From this RSPCA frequently asked questions page about layer hens:

A hen is declared ‘spent’ when her egg production drops at around 72 weeks of age. At this point she is considered less profitable and removed from the production system.

The process of removing ‘spent’ hens is known as ‘depopulation’ where hens are manually caught by human ‘catchers’ (up to 5 hens per hand) and placed into crates ready for transport.

There can be welfare issues during depopulation. For example, time pressures and rough handling often lead to injuries such as bone fractures.

Spent hens are either killed on farm and composted, or transported to an abattoir for slaughter. Some of the meat from spent hens may be exported, while other options may include pet food, and lower-quality processing meat for human consumption (for example in soups and stocks.)

For these reasons, and the more general argument about animals-as-means-to-our-ends from part 3 I choose not to consume eggs anymore, where possible.

There is always the option of keeping your own hens or sourcing them from a local community that raises them ethically. For poor communities there’s a lot of sense in this.

Part 6: surplus to requirements #2