Arcturus, or Alpha Bootis, the big orange brightness in the Eastern sky at Spring is only 36.7 light-years from Earth and appears huge at Mag -0.05.
So bright and huge, light from Arcturus opened the Chicago World Fair of 1933 via a photocell in the eyepiece of a telescope. Why? Because that light left Arcturus during the last World’s Fair in Chicago, the 1893 Exposition…or close enough.
Much of the EM radiation from the star is in the infrared. An off-sequence K0III red giant that fuels itself primarily through helium core-fusion ending in carbon (C) and hydrogen shell-fusion. It is calculated to be over 7.1 BILLION YEARS OLD (WoW! Think about that for a second). It is slightly variable and oscillatory, having buried it original corona underneath its atmosphere, we suspect.
As it evolves, Arcturus expands and oscillates. Is this normal? Hmmm. What’s normal?
From Wikipedia- “Arcturus is moving rapidly (-122 km/s or -270,000 mph: the minus sign representing radial velocity towards Earth) relative to the Sun, and is now almost at its closest point to the Sun. Closest approach will happen in about 4,000 years, when the star will be a few hundredths of a light-year closer to Earth than it is today. (In antiquity, Arcturus was closer to the centre of the constellation.) Arcturus is thought to be an old-disk star, and appears to be moving with a group of 52 other such stars, known as the Arcturus stream.”
“This Arcturus stream is a group of stars first discovered in 1971 not to be in the plane of the Milky Way galaxy. It has been proposed as a remnant of an ancient dwarf satellite galaxy, long since disrupted and assimilated into the Milky Way. It consists of old stars deficient in heavy elements.However, Bensby and colleagues, in analysing chemical composition of F and G dwarf stars in the solar neighbourhood, found there was no difference in chemical makeup of stars from the stream, suggesting an intragalactic rather than extragalactic origin. …”
We’ll get back to Arcturus at a later date.