Archive for May, 2011

T Pyx on the way back down

May 31, 2011

The T Pyx light curve is certainly showing a downward trend since the last time I posted about it.

T Pyx light curve (visual and Johnson V bands) on May 31 2011

T Pyx light curve (visual and Johnson V bands) on May 31 2011

This AAVSO page about T Pyx mentions short-term variations in the 1966 outburst’s light curve, also evident in the current light curve.

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2011 AAVSO Director’s Award for little old me

May 27, 2011

I was very happy, and humbled, to be told this week that I’m the recipient of the 2011 AAVSO Director’s Award for leading the development of VStar, an open source variable star data visualisation and analysis tool. It’s humbling when you look at the predecessors of the award.

You can learn more about VStar, and the context in which it got started, at CitizenSky. I have not developed VStar alone. I’ve had help from domain experts, AAVSO staff, and other developers.

If you want to try VStar, just click the green Download button on the SourceForge page. If you have Java 1.6 or higher installed on your Windows, Mac, Linux, or OpenSolaris machine, the latest version of VStar will be downloaded and run (via Java Web Start technology).

VStar is still an active, ongoing project. There’s plenty left to do. One key area of focus right now is the addition of a modelling capability and more period analysis functionality. If you are a developer looking for an interesting Science-related project to contribute to, try it out and have a look at the SourceForge bug & issue tracker to see if anything interests you.

Data analysis (e.g. finding periods in variable star data) is a growth area for amateur astronomers. VStar is growing into a tool that makes that easier to get into.

Now, back to coding… 🙂

Outburst of recurrent nova T Pyx

May 8, 2011

The recurrent nova T Pyx is in outburst for the first time in 45 years. Prior to this it had been known to undergo an outburst roughly every 20 years from 1890 until 1966.

The faint southern constellation Pyxis is bordered by Vela, Antlia, Hydra, and Puppis.

There are only about 10 recurrent novae known in our galaxy.

These objects belong to a sub-class of cataclysmic variables, a binary star system in which a white dwarf accumulates matter from a companion star. This eventually sustains runaway nuclear fusion leading to a substantial increase in brightness.

The image below is an artist’s rendering of the cataclysmic variable, RS Oph, that last went into outburst in 2006, reaching naked eye visibility (similarly in 1985, 1967, 1958).  Another one, U Sco, went into outburst early last year.

Example of a Cataclysmic Variable (RS Oph) from http://apod.nasa.gov/apod/image/0607/rsoph_pparc_big.jpg

Example of a Cataclysmic Variable (RS Oph) (http://apod.nasa.gov/apod/image/0607/rsoph_pparc_big.jpg)

The 1966 T Pyx outburst reached magnitude 6. It will be interesting to see what its maximum brightness ends up being this time around.

The discoverer of T Pyx was Henrietta Leavitt of Cepheid variable fame. Michael Linnolt, in Hawaii, first reported the current outburst on April 14. Here’s the AAVSO alert notice.

Some of the early confirmation observations were visual estimates by Australian amateurs such as Alan Plummer and Steve Kerr. Photometric estimates appeared soon after, including some from former ASSA member, Peter Nation.

The following plot (using VStar) shows the current and 1966 outbursts along with the many fainter-than observations (in yellow) so commonly recorded in between outbursts. These are where the observer has said: “I can’t see T Pyx, but I can see a faint comparison star, so it’s fainter than that”.

T Pyx data back to 1920 showing visual and fainter-than observations

T Pyx data back to 1920 showing visual and fainter-than observations

The 1966 outburst started in early Dec 1966 and T Pyx’s magnitude didn’t reach maximum until early January 1967, then took about 6 months to fall back to pre-outburst levels. From the onset of that outburst, T Pyx took about 2 days to go from mag 13 to around mag 9.5, then around 2 weeks to climb to 7.5, and approximately two more weeks to reach around mag 6. The next light curve plot (visual and Johnson B bands) shows this:

T Pyx 1966 outburst

T Pyx 1966 outburst

The current outburst has been in progress for three and a half weeks. After an initial rapid rise of several magnitudes in the first few days from around 14.5 to 7.5, T Pyx has continued an overall upward trend (apart from a couple of brief dips) to a visual magnitude of around 6.8. This is easily visible in 7×50 binoculars.

What follows are three light curve plots showing AAVSO International Database observations from just before the start of the outburst up until May 11.

The first light curve shows only visual estimates.

T Pyx current outburst (visual band)

T Pyx current outburst (visual band)

The second light curve shows visual and Johnson V photometric bands.

T Pyx current outburst (visual and Johnson V bands)

T Pyx current outburst (visual and Johnson V bands)

The third light curve shows all bands that T Pyx is being observed in, including infrared.

T Pyx current outburst (visual and various photometric bands)

T Pyx current outburst (visual and various photometric bands)

It’s interesting to notice that the 1966 event was recorded in just a couple of bands, whereas the current one is being recorded in several. That’s a common trend when you look at AAVSO data in recent years, given the equipment now available to amateur astronomers, and the increasing number of telescopes that can be accessed via the Internet (e.g. global rent-a-scope).

Notice that the magnitude range varies with band, particularly relative to visual and Johnson V observations.

The visual estimate of magnitude 6.9 at the cross-hairs on May 2nd is my single contribution so far. Pyxis consists of fairly faint stars, so I spent a few nights just getting used to the binocular and low power telescopic fields before attempting an estimate.

It’s fascinating to watch this event unfold. Of course, given its distance, we are actually seeing an outburst that happened more than 3000 years ago.

Further reading:

The Square Kilometre Array (SKA)

May 6, 2011

Australia and New Zealand have together been short-listed, as has South Africa, to host a revolutionary new radio astronomy facility: the Square Kilometre Array (SKA). I attended two talks about SKA recently, one hosted by RiAus, another by the Australian Computer Society.

The SKA will provide a sensitivity that is about 50 times greater than any radio telescope before it. The sheer size and complexity of this thing is staggering. It will consist of 3000 dishes spread across a couple of thousand kilometres with a combined collecting area of about 1,000,000 square metres (i.e. 1 square kilometre).

There are plenty of technical challenges to solve in areas like data storage, database technologies, and the need for green energy to handle the SKA’s power requirements. A super-computer will be required on-site to process the signals collected by the SKA in real-time.

Here are some factoids from SKA publicity material:

  • The SKA will generate enough raw data to fill 15 million 64GB iPods every day.
  • The SKA will use enough optical fibre to wrap around the Earth twice.
  • The SKA will be so sensitive it could detect an airport radar on a planet 50 light years away.

Some questions the SKA will be help to answer, or provide more insight into, are:

  1. How were the first stars and black holes formed?
  2. How do galaxies evolve?
  3. What is the nature of Dark Energy?
  4. Are there Earth-like planets around other stars?
  5. What generates giant magnetic fields in space?

As mentioned at the RiAus talk, part of the excitement lies in what the SKA may be used to discover that we had no clue about in the first place, i.e. serendipity.

A true revolution of values…

May 6, 2011

A track on Linkin Park’s latest album (A Thousand Suns) includes excerpts from a Martin Luther King speech given during the Vietnam War. You don’t have to share King’s religious convictions (as an atheist, I don’t) to agree with this:

A true revolution of values will lay hand on the world order and say of war, “This way of settling differences is not just.” This business of burning human beings with napalm, of filling our nation’s homes with orphans and widows, of injecting poisonous drugs of hate into the veins of peoples normally humane, of sending men home from dark and bloody battlefields physically handicapped and psychologically deranged, cannot be reconciled with wisdom, justice, and love. 

I’m not sure why, but this came to mind when I heard about the killing of Osama bin Laden. Somehow I expected better of the Obama administration. Should governments really be in the business of assassination, no matter how hateful the target?

Granted, the Australian government has been party to some ethically questionable actions (think of the Baxter Detention Center), but I’m fairly sure that a random Australian plucked off the street would be a little shocked if Canberra suddenly ordered a targeted assassination of a terrorist. I realise that the scale of the Bali night club bombing was much smaller than 9/11, but Australia is not immune to terrorist acts any more than other nations.

The well-known Australian lawyer Geoffrey Robertson has called the killing of bin Laden a perversion of justice, making Osama a martyr and giving Obama the next election.

In the more than 40 years since King’s speech, we still seem to be totally clueless with respect to wisdom, justice, and love…

If we were the inhabitants of a planet seeking entry into something like Star Trek’s United Federation of Planets, we should expect to be ignored as the savages we still are.