Archive for the ‘Astronomy’ Category

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

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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.

Old photos of the 2001 Leonids from Malalla

January 3, 2019

I was looking through a bunch of old photos and slides today and came across these star-trailed pictures (film-based) I took of the 2001 Leonid meteor shower from Malalla, South Australia:

Star trailed images taken with a tripod-mounted Pentax K100D

Meteors radiate outward from a point in the sky in the constellation Leo (called the radiant) since the Earth is ploughing into left over sublimated material from comet Temple-Tuttle in that direction.

My father and I stayed up until the wee hours watching the meteors come thick and fast. I have good memories of that evening spent with dad. After he’d had enough, I stayed up to watch them until the sun came up.

July 2018 Lunar Eclipse from Adelaide

July 28, 2018

Apart from the “getting up at 4:15am” part, the total lunar eclipse on Saturday morning (July 28) was very enjoyable.

MidTotality

Luna 1 minute after maximum totality (f2.0, ISO 200, 1 sec). For reference, the right-most star is rho Capricorni, a double with a brightest component of magnitude 4.8.

I took a little over 200 images from our backyard starting a few minutes before totality began at 5am ACST until just after the end of totality at around 6:45am.

I also looked at the Moon through 7×50 binoculars from time to time, from which the impression of the Moon as a 3D ball of rock hanging in the sky was evident.

I had initially planned to use my 8″ telescope for imaging as well, but in the end, was happy with to take wide field shots, so left the scope inside.

All images were taken with a tripod-mounted Canon 1100D and 100mm fixed lens controlled using Canon EOS Utilities.

EclipseMontage

A montage showing Luna 5 minutes before the start of totality (f2.0, ISO 400, 1/8 sec), 1 minute after maximum totality (f2.0, ISO 200, 1 sec), and 9 minutes before the end of totality (f2.0, ISO 200, 1 sec).

Along with most images I’ve seen, these present a vividness not evident only by eye. The following images are perhaps closer to what was seen without aid of imaging equipment.

MarsMoonTotality2

Moon and Mars 20 minutes before the end of totality (f2.8, ISO 200, 1 second).

MoonLowOnHorizonJustBeforeEndOfTotality

The Moon and Mars 8 minutes after the end of totality (f2.0, ISO 100, 1/10 sec), just above our SW fence line.

The final image shows an incidental image of the International Space Station passing “near” our lemon tree when I noticed it passing above the Moon.

ISS

ISS trail (f2.0, ISO 100, 1.3 sec)

At least one image of the eclipsed Moon also ended up with a “stray” satellite in the field.

Nova Carina 2018 update #2

March 27, 2018

Shortly after my last post I observed the nova again. Within 24 hours it has dropped by a full magnitude after peaking at 5.7, a little higher than my binocular estimate of 5.8 from last night.

My two observations are in purple, as usual, with the observation an hour ago under the cross-hairs.

ASASSN-18fv-2018-03-27

 

Nova Carina 2018 update

March 27, 2018

A “happy snap” (with iPhone) of the sky over my backyard rooftop, with Luna peeping through cloud. The nova’s location is behind me from this vantage point.

After being away for a week and a cloudy sky on Sunday, I caught my first glimpse of Nova Carinae 2018 (ASASSN-18fv) in 7×50 binoculars minutes before the sky started clouding out.

I estimated it to be 5.8 (purple, at top right) at just after 11pm Adelaide time.

Note also the upward trend-line.

I had hoped to subsequently image the nova to carry out DSLR photometry for better accuracy but that didn’t pan out due to cloud.

At the time of submission to AAVSO the last observation before mine was 6.5, several hours earlier. Since then, others have submitted observations up to 5.9. So, I appear to have caught Nova Car 2018 on the rise and at its peak so far.

Nova in Carina

March 23, 2018

Nova Car 2018 or ASASSN-18fv was discovered by the ASAS Supernova network on March 21st and has so far reached around magnitude 6.5 from a progenitor magnitude of 19.9 within a couple of days.

Below is a Stellarium view of the location of ASASSN-18fv, very close to the 5.1 magnitude comparison star near the Eta Carina nebula and star, a variable whose brightness I often estimate.

A binocular finder chart with a slightly different orientation from the Stellarium screenshot is shown below:

This is a crowded area of the sky, and being so close to the 5.1 star, it may be tricky in a low power binocular field.

Rob Kaufman posted this image of the nova, with yet another different orientation:

asassn-18fv2c202120mar20201820text2030-sec

I have not yet had the opportunity to observe the nova; hopefully in a couple of days.

The AAVSO alert notice has more details.

Nova Cir 2018 Gamma-ray Space Telescope observations

February 3, 2018

AAVSO alert notice 613 for the nova in Circinus requests visual, DSLR, CCD and spectroscopic observations, with multiple observations each night if possible, in support of the Fermi Gamma-ray Space Telescope’s observations that are currently underway:

 

spacecraft

Source: https://fermi.gsfc.nasa.gov/inc/img/spacecraft.jpg

Target-of-opportunity observations requested by Dr. Mukai are taking place now through February 6 UT with the NASA Fermi Gamma-ray Space Telescope. To support these observations, observers are asked to make several observations per night.

I’m processing DSLR observations of the nova from last night and plan to continue observing over the next few nights. Its visual magnitude is currently at around 7.2.

Here’s a spectrum taken by Rob Kaufman on January 31:

ncir201820spectrum2c203120jan2020182c2012-5420ut20text

Total Lunar Eclipse from Adelaide

February 1, 2018

Adelaide was largely clouded out for the eclipse but the cloud thinned at times well enough to get some reasonable images, especially after midnight. Taking more than 100 images also helped.

I used a Canon 1100D at the prime focus of my 8″ Schmidt-Cassegrain Alt-Az (Meade LX-90) telescope.

Here are some images I thought were interesting enough to show. These are straight off the camera with no processing except RAW to JPEG conversion.

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Pre-totality umbral shadow through cloud. ISO 100, 1/10 second.

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Totality. ISO 800, 2 seconds.

IMG_0006-low

Not long before end of totality. ISO 800, 2 seconds.

IMG_0027-low

Soon after end of totality. ISO 800, 1 second.