The most distant Novae observed so far

ESO PR Photo 18b/00 [Preview - JPEG: 400 x 452 pix - 83k] [Normal - JPEG: 800 x 904 pix - 224k]
Caption: Images of two of the novae in NGC 1316 that were discovered during the observational programme described in this Press Release. Both composites show the blue images (B-filter) obtained on January 9 (upper left), 12 (upper right), 15 (lower left) and 19 (lower right), 2000, respectively. The decline of the brightness of the objects is obvious.

An analysis of the images that were obtained in blue light (B-filter) resulted in the detection of four novae. They were identified because of the typical change of brightness over the observation period, cf. PR Photos 18b-c/00, as well as their measured colours.

Although the time-consuming reduction of the data and the subsequent astrophysical interpretation is still in progress, the astronomers are already now very satisfied with the outcome.

In particular, no less than four novae were detected in a single giant galaxy within only 11 days. This implies a rate of approximately 100 novae/year in NGC 1316, or about 3 times larger than the rate estimated for the Milky Way galaxy. This may (at least partly) be due to the fact that NGC 1316 is of a different type and contains more stars than our own galaxy.

The novae in NGC 1316 are quite faint, of about magnitude 24 and decreasing towards 25-26 during the period of observation. This corresponds to nearly 100 million times fainter than what can be seen with the naked eye. The corresponding distance to NGC 1316 is found to be about 70 million light-years.

Moreover, the discovery of four novae in one galaxy in the Fornax cluster was possible with only 3 hours of observing time per filter. This clearly shows that the new generation of 8-m class telescopes like the VLT, equipped with the new and large detectors, is able to greatly improve the efficiency of this type of astronomical investigations (by a factor of 10 or more), as compared to previous searches with 4-m telescopes.

The road is now open for exhaustive searches for novae in remote galaxies, with all the resulting benefits, also for the accurate determination of the extragalactic distance scale.

Notes

[2]: A graphical illustration of the nova phenomenon can be found at this website.

[3]: For example, in 1987, Canadian astronomers Christopher Pritchet and Sidney van den Bergh, in an heroic tour de force with the 4-m Canada-France-Hawaii telescope, found 9 novae after 56 hours of monitoring of 3 giant elliptical galaxies in the Virgo cluster of galaxies.

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