JB — yes, there was a time when they thought they had detected first one and then two planets of Barnard’s star.

There were two previous waves of exoplanet finds prior to the one we’re having now. They used astrometric techniques (wobbles in star sky paths, essentially). The first was in the 1940s, when Kaj Aa. Strand found an 8-Jupiter-mass planet of 61 Cygni, and I think a couple other such planets were found as well. The second wave was in the 1960s, when people working at Sproull Observatory in PA (Sarah Lee Lippincott, Peter Van de Kamp, and others) discovered a whole host of exoplanets, including one of Barnard’s star that was just 1.5 Jupiter masses in 1963. In 1968 the Barnard’s data was revised to a 1.6 Jupiter mass planet in a highly eccentric orbit, and the same year another interpretation came out which had two planets in coplanar, nearly circular orbits.

People suspected these finds might be spurious. For one thing, the Sproull people kept finding planets with periods of about 24 years. In 1973, George Gatewood and a colleague I can’t remember offhand did an astrometric analysis of Barnard’s Star and found nothing. They also discovered that the lens plate and photographic emulsion had been changed at Sproull in the ’40s, just enough to be finding 24-year periods in the 1960s.

All the early discoveries — 61 Cygni, Lalande 21185, Barnard’s Star, 18 Epsilon Eridani, etc. — are now considered mistakes. Not useless work, because astronomers were able to sharpen their techniques and learned how to avoid making certain types of mistakes. But all the findings were spurious. This is one reason there was so much suspicion of Mayor and his colleague’s 1995 find of the 51 Pegasi planet.

You can still find a lot of old astronomy books which mention the planets of 61 Cygni and Barnard’s Star.

Anyways, I wanted to comment on the middlingly boring subject of determining what is a planet. I had a discussion with a astrophysicist tonight (I am traveling overseas, so it is night for me) and he mentioned that it looks as though there is a linear relation between star mass and planetary mass. That I think lends to the idea of a terrestrial planet of 5 earth masses around a M star being dynamically similar to Jupiter in the sense of “clearing the orbit”.

I’ll try to report as accurately as possible what he said. I’ll start by saying that this is a guy who models planet formation and dynamics of exoplanets, so far more of an expert than I.

Basically, his take is that dwarf planet is a meaningless term. This is because “dwarf planets” are in the same dynamical class with asteroids, KOB’s and comets, none of which are present in a mature system unless trapped there, such as the asteroid belt by Jupiter and Mars. As for the KBO’s and comets, that region of the solar system hasn’t reached full maturity, ie not enough time has passed for the m to be deflected or for a collision to occur.

The issue of “what is a planet” is more yawn inducing than planet-finding itself.

If as you imply you find planet-finding boring, why bother commenting on this post?