Giant Star AG Carinae in Carina | Hubble

Giant Star AG Carinae in Carina | Hubble

AG Carinae (AG Car) is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. It shines with the brilliance of 1 million suns. AG Carinae is a few million years old and resides 20,000 light-years away. This giant star is waging a tug-of-war between gravity and radiation to avoid self-destruction. The star is surrounded by an expanding shell of gas and dust—a nebula—that is shaped by the powerful winds emanating from the star. The nebula is about five light-years wide, equal to the distance from here to our nearest star, Alpha Centauri.

AG Carinae is formally classified as a Luminous Blue Variable because it is hot (blue), very luminous, and variable. Such stars are quite rare because there are not many stars that are so massive. Luminous Blue Variable stars continuously lose mass in the final stages of their life, during which a significant amount of stellar material is ejected into the surrounding interstellar space, until enough mass has been lost that the star has reached a stable state. 

AG Carinae is surrounded by a spectacular nebula, formed by material ejected by the star during several of its past outbursts. The nebula is approximately 10,000 years old, and the observed velocity of the gas is approximately 70 kilometers per second. While this nebula looks like a ring, it is in fact a  hollow shell rich in gas and dust, the center of which has been cleared by the powerful stellar wind travelling at roughly 200 kilometers per second. The gas (composed mostly of ionised hydrogen and nitrogen) is visible to us in these images as a thick bright red ring, which appears doubled in places—possibly the result of several outbursts colliding into each other. The dust, here visible in blue, has formed in clumps, bubbles and filaments that are shaped by the stellar wind.

Scientists who observed the star and its surrounding nebula note that the ring is not perfectly spherical; it appears to have a bipolar symmetry, indicating that the mechanism producing the outburst may have been caused by the presence of a disc in the center, or that the star is not alone but might have a companion (known as a binary star). An alternative and simpler theory is that the star rotates very fast (as many massive stars have been found to do).

Credit: European Space Agency (ESA)/Hubble and NASA, A. Nota, C. Britt

Release Date: Sept. 13, 2021

#NASA #ESA #Hubble #Astronomy #Space #Science #Star #AGCarinae #AGCar #HD94910 #LBV #LuminousBlueVariable #Carina #Constellation #MilkyWayGalaxy #Cosmos #Universe #HST #SpaceTelescope #GSFC #STScI #UnitedStates #Europe #STEM #Education