Catalogues in Chromoscope

Astronomers love to catalogue the sky. We've been doing it as long as astronomy has existed. Perhaps the most famous astronomical catalogue is the Messier catalogue - compiled by Charles Messier so that he didn't mistake nebulae and galaxies for comets - but many thousands of catalogues now exist.

In the (not so) old days, catalogues were printed in books or journals. You'd visit the library, find the volume you needed, and go through transcribing the data for the objects you wanted. That was hard work and prone to transcription errors after staring at rows and rows of data. It makes your eyes go funny. I know that from experience.

These days, most important catalogues and data sets are compiled digitally, are published digitally, and end up on Vizier run by Centre de Données astronomiques de Strasbourg. The service is great because you can search specific catalogues and limit the search by position, magnitude, flux density or others parameter in the data set. It saves lots of time. Vizier even has web services and a set of command line tools to let power users interact with it.

This evening I decided to see if I could use those tools to help me convert Vizier catalogues into KML (the format used for Google Sky) so that I could pipe them into Chromoscope. It turns out that it isn't too tricky so I've added it to the development version of Chromoscope for testing.

My first test was my table of measurements of Compact Jodrell-Caltech Flat-spectrum (CJF) radio sources. Plotting the CJF sources in Chromoscope shows how the sample is limited by position on the sky (amongst other things). The limits are to objects above Declination 35 degrees (B1950) and Galactic latitudes greater than 10 degrees from the plane of The Galaxy.

Here are some other examples:

Thanks to Paul Woods and Chris Tibbs for helping me to test it this evening with some nice examples.

Posted in astro blog by Stuart on Monday 20th Jun 2011 (23:46 BST) | Permalink

Super Sweet APOD

The very first Astronomy Picture of the Day entry was posted on 16th June 1995. From those extremely humble beginnings, in the pre-CSS/pre-HTML 3.2 days, APOD has gone on to post 5842 daily images missing only a few days in all that time. I think it has become an Internet institution.

On its 16th birthday APOD doesn't look much different to that first entry. The biggest design change probably happened on September 22nd 1995 - when it became center-aligned - and it has looked pretty much the same ever since. The design may be basic but it has certainly been consistent. It has also consistently shown us fantastic images of the Universe along with great descriptions to explain what we are seeing.

Congratulations to Rob Nemiroff and Jerry Bonnell for all the great work over the years. Many happy returns APOD and here's to another 16 years!

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Posted in astro blog by Stuart on Thursday 16th Jun 2011 (10:06 BST) | Permalink

Supernova in M51

Last week I spotted an Astronomer's Telegram about a discovery of a potential supernova in M51 - the Whirlpool Galaxy.

A supernova is what happens when a massive star reaches the end of its life and for a short time that exploding star can appear as bright as an entire galaxy. In a galaxy like ours you might expect as many as two or three supernovae per century but this is the third seen in M51 in the past 17 years.

The discovery was made by the Palomar Transient Factory (PTF) and the Galaxy Zoo Supernovae project. Since then, many amateur and professional telescopes around the world have been watching supernova SN2011dh fade. In fact several people I know have been observing it: astronomer George Privon has seen it with the LBT and Megan is hoping to catch it at radio wavelengths this week. The 2m diameter Faulkes Telescope North had some bad weather at the end of last week so the first public image from FTN since the supernova was taken this morning. That image can be compared to this image of M51 from April 28th.

Supernovae can be discovered by anybody and you don't need fancy equipment. The main things you need are a familiarity with the night sky and the time to keep looking at the skies. The Galaxy Zoo Supernovae project even makes it really easy to find them from the comfort of indoors.

Posted in astro blog by Stuart on Monday 06th Jun 2011 (13:10 BST) | Permalink
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