Antares, is super red giant that is one of the most glittering in the sky in the constellation Scorpius.
So much of its brightness and color, at night can be confused with Mars (the red planet appears red to the naked eye).
Located 500 light years (next door), its size makes it so great, it believes it or not, this is not as hot as we thought … little more than our sun. But yeah, it is about 700 times larger .. . something like that about 4 astronomical units (an astronomical unit is the distance from the Sun to Earth, so let down calculations).
Like all Super red giant, basically is nothing more than “air inside”, ie, albeit very large, gravity is very small (until it collapses) being the mass about 20 times that of our Sun (compared the size …). The outer layers of the star are very volatile and therefore in itself is more helium and hydrogen (gas going to be, not mass, which is smoke) than anything else. The core is not dense and therefore has few heavy metals and mainly consists of helium.
What you see in the picture is the star, Antares, and a cloud of gas that is nothing but hydrogen is escaping from the low density … let the smoke that I comment above.