Astronomy

Some of you probably have heard about discovery of extrasolar planet Gliese 587 C. If you don’t familiar with this term, extrasolar planets (exoplanets) refers to planet that orbiting any distant star, beyond our Sun.

So far, astronomers have found more than 200 exoplanets in our galaxy, and this number is still grown. What makes discovery of Gliese 587 C itself is so special among the other is that computer modeling suggests that Gliese 587 C may have liquid water on its surface. This is certainly good news for people who wondering about life on another planet. But is there any life in Gliese 587 C?

To discover Gliese 587 C, astronomer use special technique called radial velocity measurement. Basically, this method detect planets around stars, in the way that the movement’s measurement determines the planet’s orbital period, while the resulting size of the displacement allows the calculation of the lower bound on a planet’s mass. Radial velocity methods alone may only reveal a lower bound, since a large planet orbiting at a very high angle to the line of sight will perturb its star radially as much as a much smaller planet with an orbital plane on the line of sight.

This method is not visually detecting an exoplanet. What astronomers said about Gliese 587 C is, that the planet orbiting its host star on range of distance called “habitable zone”, while water in surface (if any) can be remains liquid. But, beside of water, there are several factors that had important role for life on the planet — we will discuss on this topic on another post.

So, does Gliese 587 C can harbor life on its surface? This question remains unanswered. To date, no spectral measurement had been conducted to Gliese 587 C. This means we know almost nothing about the planet: its atmosphere composition, surface elements, etc. The only we know about this planet, based on radial velocity measurement, is about its mass, orbital period, and distance to its host star.

The only exoplanet known with existence of water, in form of vapor on its atmosphere, is HD 209458 b. But HD 209458 b is typically “hot Jupiter” planet — an exoplanet whose it mass is close to or exceeds that of Jupiter (1.9 × 10²⁷ kg), but orbiting closer to its parent star — so that, can’t support life on its surface.

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