A Bit More Detail

Canadian? Well, at least by a Canada-based team.

The recent discovery of the planet CoRoT-7b, a planet discovered by the European Space Agency's CoRoT space telescope which discovers planets by checking for dips in the luminosity of their parent star caused by the planet's blocking the line of sight between Earth and said star, is hugely impressive. A rocky planet with a diameter almost twice that of Earth and perhaps five times as massive as our homeworld, orbiting a main-sequence yellow-orange dwarf star roughly 490 light years away, this planet is one of the more Earth-like world found, notwithstanding that a year of just 20 Earth-days has almost certainly given the world a surface of lava. This might not be as astonishing as the discovery of a planet with a mass six times that of Jupiter in the Andromeda Galaxy 2.3 million light years away (yes, you read me correctly), but still, the hunt for extrasolar planets has progressed at a remarkable speed. Soon, using one (or more) of any number of detection methods, astronomers will be able to find worlds similar to Earth or smaller; soon, we'll be able to get some data, at least, on the frequency of life.

All this is momentous. But are the other firsts? There's a few.

When were the first claims to have found extrasolar planets?

The first was in the mid-19th century, when various observers observed the binary star 70 Ophiuchi and believed to have found a planet of Jupiter's mass or greater. These claims have been disproved, a pity I suppose since both stars of 70 Ophiuchi are relatively Sun-like and close to Sol. In the middle of the 20th century, astronomer suggested Peter van de Kamp suggested that the dim nearby red dwarf of Barnard's Star had its own system, but these claims have been disproven.

When were the first planets roughly of Earth's mass found?

These were worlds found in orbit of the pulsar PSR B1257+12, starting with two worlds in 1992 and ending up with three worlds and one dwarf planet by 2007. These worlds, belonging to a selected group of pulsar planets formed around rapidly rotating neutron stars, are confusing. No one knows how they could exist in orbit of stars which recently exploded, since--as Steven Dutch notes--it would take only a day to melt the Earth if our sun blew up. The common explanation is that they formed after the explosion.

What, you might ask, was the first discovery of a planet that was confirmed to actually exist?

It was the planet Gamma Cephei Ab, a world with a mass approximately 160% that of Jupiter orbiting the orange giant star Gamma Cephei A some 45 light years away. As one observer notes, "[t]he planet, with a mass of at least 1.59 times that of Jupiter, is one of the few known to lie within a double-star system, and orbits the main star Gamma Cephei A with a period of 2.47 years at an average distance of 2.03 Astronomical Units (304 million kilometers, 189 million miles), or 2.03 times the distance between the Earth and the Sun. A modest eccentricity brings the planet as close as 1.62 AU to its parent star and takes it as far as 2.43 AU."

When was it first suspected to exist?

The initial announcement was made in July 1988.

Who was it made by?

The announcement was made in the paper "A Search for Substellar Companions to Solar-Type Stars", submitted to The Astrophysical Journal by Bruce Campbell, George Walker, and Stephenson Yang, all three working out of British Columbian academic institutions and making use of the Dominion Astrophysical Observatory in the British Columbian capital of Victoria.

In their 1988 paper, Campbell et al made use of the radial velocity technique to study 16 Sun-like stars, examining to see whether or not an orbiting planet was tugging on its parent star, using a hydrogen fluoride mixture to help "steady" the spectrum of the star so as to measure more precisely. Of all these stars, Gamma Cephei A returned the strongest signal of a planet. Alas, these claims weren't very widely publicized.

To be fair, there was some uncertainty. In the 1992 paper by Walker et al. "Gamma Cephei - Rotation or Planetary Companion?", the claim was retracted, on the grounds that Gamma Cephei A's post-main sequence fluctuations in luminosity were probably responsible for the signal of Gamma Cephei Ab. Later in 1995, the aforementioned French team of Mayor and Queloz announced the 51 Pegasi b, a gas giant planet half the mass of Jupiter orbiting a main-sequence yellow dwarf broadly similar to Sol in a tight orbit, using a refined version of the radial velocity method pioneered by Campbell et al.

More than 200 exoplanets have been discovered since, all but a handful using variations on the precision radial-velocity technique pioneered at the University of Victoria. One of these planets orbits Gamma Cephei, just as Campbell and Walker suspected.

"Everyone in the field recognizes that Campbell and Walker were the first ones to see evidence for a planet around a Sun-like star in 1992," said UBC astronomer Jaymie Matthews. "Bruce and Gordon could have legitimately gone out and told everybody they'd found a planet." He sighs. "But being good scientists -- and maybe maybe being conservative Canadians -- they didn't make the proclamation that it was definitely a planet."

Their 1988 discovery was vindicated, happily, with the 2003 paper "Planet around [gamma] Cephei A", which definitively excluded the possibility that the signal of a planet orbiting Gamma Cephei A was spurious and concludes that the "most likely explanation of the residual radial velocity variations is a planetary-mass companion with 1.7M_J and an orbital semimajor axis of 2.13 AU." The authors note that the discovery of this planet, located in a a binary star system where the two stars approach each other quite closely, suggests something about the ease of forming planets. They also note that it's important to study stars for extended periods if one's planet-hunting, in order to come up with the best possible data.

We did it. Canadians managed to make a major technological advance and in so doing helped to expand our species' knowledge of the universe around us immensely. What, I ask you, isn't very nice about that?