Adopting a Star

Whenever the holiday shopping season rolls around, I consider the idea of setting up an "Adopt a Star" website to help fund scientific research. A quick Google search persuades me to abandon the idea -- the Internet is already full of such sites, and most of them are far more sophisticated than anything I would have time to create. Anyone who cares to fork out $19.95 can name a star "Lula", after their cute Bichon Frise puppy -- they even get a certificate with a star map and the vital statistics of their stellar namesake. But what are they really buying?

The International Astronomical Union (IAU) is the only "internationally recognized authority for naming celestial bodies... and names are not sold". In fact, with the exception of a few bright stars that have ancient traditional names, most of the stars in the sky only have boring old catalog numbers. The IAU does name comets after the discoverers, and astronomers who find new planets or asteroids in our solar system are allowed to suggest names for them (though they can only be named after people who have been dead for more than 100 years, which obviously limits the commercial possibilities). None of the websites that allow you to "buy" or "adopt" a star are affiliated with, or endorsed by, the IAU. So what are these businesses selling?

It's important to distinguish between companies that allow you to "adopt a star" and those that say you can "buy a star name". Although both are engaged in essentially the same business, the representation of the transaction as an "adoption" is more intellectually honest. When you "adopt a highway" it's understood that you do not thereby own a section of a public road. Instead, you agree to keep the adopted stretch free from garbage in exchange for a blue sign on the roadside acknowledging your effort (and possibly persuading drivers to stop at your coffee shop). In the case of stars, your only responsibility is to pay the $19.95 -- the company then lists your name beside the chosen star on their website, and maybe sends you a glossy certificate. One of the best operations I discovered recently is actually run by scientists to support their research. The website resembles the vision I had for "Google Sky", which I wrote about last December, and cleanly separates the commercial portion of the site from the main section that is meant to be a tool for astronomers and the general public.

Allowing anyone to adopt a star is fairly harmless, and most people probably realize that astronomers around the world do not subsequently publish scholarly articles detailing their in-depth decades-long study of "Lula" the puppy star. For those who don't realize that it's just a novelty gift, I have some very nice real estate on the Moon that promises to be really hot property in a few years...

Alien Solar Systems

Last week a team of scientists in California announced the discovery of the fifth planet orbiting a distant star similar to our sun. The star is known as "55 Cancri", and is located 41 light years away in the constellation Cancer. This star now holds the record for hosting the largest known planetary system outside of our own. Only one other star (called mu Arae) is known to host four planets, while triple-planet systems have been documented around another half-dozen stars.

Since 1995, more than 220 planets have been discovered in orbit around other stars. The overwhelming majority of these planets have been found by their gravitational influence on the star that they orbit. We tend to think of a planet as simply moving around its star -- but even small planets exert a gravitational tug on the star that causes it to wobble around slightly in space. Astronomers can measure this wobble, essentially by passing the light from the star through a prism to spread it out into all of its colors (think of the famous Pink Floyd album cover) and then carefully measuring the positions of dark lines that appear where different chemical elements like hydrogen and helium absorb light near the surface of the star. The color corresponding to the position of these dark lines moves around as the star wobbles -- basically for the same reason that the pitch of an ambulance siren sounds different when it is moving towards you or speeding away (the effect is known as the Doppler shift).

The team has been monitoring 55 Cancri for more than 18 years. Since the wobbles caused by the five planets are all happening at the same time, and with different orbital periods, it took a long time to isolate the wobbles caused by each planet individually. The outermost planet in the system is about four times the size of Jupiter, and it takes 14 years to orbit the star. The other previously known planets are similar in size to Neptune, Jupiter, and Saturn, but they orbit the star relatively close in -- circling every 3, 15, and 44 days (all much faster than Mercury orbits the Sun). The newly discovered planet falls somewhere in between, orbiting the star in about 260 days. Since 55 Cancri is a little fainter than the Sun, this places the new planet inside an Earth-like "habitable zone" where liquid water can theoretically exist. Although the planet is roughly the size of Saturn, it could have large Earth-like moons where water and potentially life could survive (Saturn's largest moon "Titan" is bigger than the planet Mercury).

It's only a question of time before astronomers discover more and larger planetary systems around distant stars. The longest running surveys have been operating for less than 20 years, so even in the best case we would not be able to detect Saturn, Uranus, or Neptune if we were watching the Sun from a distance. As the technology improves we should also begin finding smaller planets, closer to the size of the Earth. In the future, people might wonder what all the fuss was about over this little five-planet system around 55 Cancri.