A Solar “Twin” and Its Planet

What’s it Like?

We live in an age of planetary exploration beyond our solar system. Ever since 1995, when the first extrasolar planet was discovered, astronomers have been finding distant worlds in ever greater numbers. What was once a science fiction idea is now reality: planets around other stars.

The  most recent discovery was made by the European Southern Observatory using the HARPs planet hunter instrument, in conjunction with other telescopes. This one was in a star cluster, which is a difficult environment for a star to exist in.  Interestingly, stars that are born in clusters don’t always stay in the clusters.  So, that makes finding a planet around a star in a cluster quite a rare treat. What’s even MORE rare is that one of the stars with a newly found planet is a solar twin. That is, it is nearly identical to the Sun. It has a similar mass, spectral class, and chemical composition to our own star. And, now we know there’s a planet orbiting it.

What’s that planet like?  Very likely NOT Earthlike. This is because it orbits much closer to its star than the star’s habitable zone. That’s the area around a star where liquid water could exist on the surface of a planet orbiting there. If the planet is too close, it’s likely getting baked by its star. So, not a good candidate for E.T.

The fact that this planet, and two others, show up around stars in clusters is providing an interesting conundrum for astronomers to solve: star clusters are not particularly welcoming places for planets, so why are these cluster stars blessed with worlds?  The cluster these stars and planets live in (Messier 67) is a type of open cluster that stays together as a cluster longer than many other such groupings because it has a higher density of stars than other clusters. Perhaps that provides a clue to the existence of planets around cluster stars. It also tells me that planets are really much more common in the galaxy than we used to think. That’s science at work: as we improve our techniques for observation, we’re seeing things that were out there all along—just waiting for us to find them. I can’t wait to see what kinds of worlds astronomers find next!