Cosmic dance of fire and ice
The European Space Agency has left netizens in awe after sharing a glimpse of the ‘mysterious’ Mira HM Sge star system on Friday. The symbiotic star is located 3,400 light-years away in the Sagitta constellation and comprises of a red giant and its white dwarf companion. The ESA dubbed it a ‘cosmic dance of fire and ice’ with the star becoming increasingly hotter and dimmer.
“Material bleeds off the red giant and falls onto the dwarf, making it extremely bright. This system first flared up as a nova in 1975. The red nebulosity is evidence of the stellar wind. The nebula is about one-quarter light-year across,” its profile on the NASA website explains.
The bridge of gas connecting the giant star to the white dwarf must presently span about 3.2 billion kilometres.
According to ESA, the enigmatic stars had surprised astronomers with a ‘nova-like outburst’ in 1975 — growing some 250 times brighter. Unlike most novae however, it has not faded in the ensuing decades. Recent observations indicate that the system has gotten hotter, but paradoxically faded a little.
“Thanks to Hubble and the retired SOFIA telescope, we’re piecing together the puzzle. Hubble’s ultraviolet data reveals scorching temperatures around the white dwarf, while SOFIA detected water flowing at incredible speeds, hinting at a swirling disk of material,” the ESA wrote in its Instagram post.
Ultraviolet data from the Hubble indicates that the estimated temperature of the white dwarf and accretion disk has increased from less than 220,000 degrees Celsius in 1989 to greater than 250,000 degrees Celsius.
The NASA team also used the now retired flying telescope SOFIA to detect the water, gas, and dust flowing in and around the system. Infrared spectral data shows that the giant star, which produces copious amounts of dust, returned to its normal behaviour within only a couple years of the explosion but dimmed in recent years. SOFIA helped stronomers see water moving at around 28 kilometres per second, which they suspect is the speed of the sizzling accretion disk around the white dwarf.
