March 09, 2004

Story of a Stellar Eruption from a Newborn Star
Updated March 31, 2004

In images taken on Januray 23, 2004 with his small 3 inch telescope, amateur astronomer J. W. McNeil (USA)  noted the appearence of a new nebulous object near the  M78 nebula in Orion.  This part of the sky is an active stellar nursery, where new stars are being born even today. This unusual object did not appear in much deeper images obtained at the Palomar Observatory in the 50's and then during the 70's.
In the announcement of this discovery on February 9, 2004, astronomers suggested that it could be the outburst of a new born star, illuminating the gas and dust from which it was formed.

This event prompted great interest among both professional and amateur astronomers worldwide, because less than a dozen of this eruptions have been witnessed in the past, even thought their are thought to play a key role in the formation of solar like stars.

By a fortunate coincidence, a team of researchers from the Centro de Investigaciones de Astronomía (CIDA) in Mérida, Venezuela, integrated by astronomers César Briceño, Kathy Vivas, and graduate student Jesus Hernández, together with their colleagues Nuria Calvet, Lee Hartmann, Tom Megeath, Perry Berlind and Mike Calkins of the  Smithsonian Astrophysical Observatory (SAO) in the US, and undergraduate student Sergio David Hoyer from Universidad Católica de Chile, were monitoring since 1999 the part of the sky that included the region were the new nebula appeared.  They used a large format digital camera installed on the 1m Schmidt telescope of Llano del Hato National Astronomical Observatory, located high in the Venezuelan Andes, to secure an unique sequence of the eruption.

The team promptly obtained additional observations with telescopes in the US to better characterize this object. The results of this work, to appear in Astrophysical Journal Letters (along with another paper in which astronomers Bo Reipurth and Colin Aspin present Gemini observatory observations of this object), indicate that the event responsible for the appearence of the McNeil nebula is most probably an FU Orionis type of eruption, in which the gas and dust in an envelope obscuring the star accrete onto a circumstellar disk, until the pile up of material in the disk leads to a gravitational instability and the material is dumped onto the central star in a catastrophic event that releases a huge amount of energy. This energy produces the large rise in brightness of the object. The observations obtained from Venezuela show that this object increased its brightness by  a factor of almost 100 compared to its pre-outburst state between 1999 and January 2003, a behavior characteristic of FU Ori events. The data also indicate that the eruption started some time between Octiber 28 and November 15, 2003, almost 2 1/2 months before it was detected by McNeil; this shows the importance of monitoring large areas of the night sky with sensitive equipment, a type of study that currently can be undertaken by few instruments around the world, the Venezuela 1m Schmidt with its panoramic detector is one of
this few facilities that is well posed to explore the time domain in astrophysical phenomena.

The following image shows an animated sequence of the outburst, constructed from I-band observations obtained between October 24, 2003 and January 26, 2004 with the 1m Schmidt in Llano del Hato. Each image is aprox. 3.5 x 3.5 arcmin (1 arcmin = 1/60 degrees) and is roughly equivalent to 1/10 of the apparent size of the Full Moon on the sky.

           Click here for a sequence of the outburst in greyscale.