New 'Earth-like' planet is not like Earth

[pmbryant]

Cross-posted from my blog:

The headlines are proclaiming: Earth-like planet discovered orbiting nearby star, Distant Object May Be a Planet Similar to Ours, 'Rocky' Earth-Like Planet Discovered, Earth-like planet without life discovered outside solar system, Found: Earth's Distant Cousin.

But once you get into the meat of the articles, you find that this planet is not terribly 'Earth-like' after all. (Blame the astronomers, not the press, for this one. Their press release is entitled "Astronomers discover most Earth-like extrasolar planet yet.")

This new planet is roughly seven and a half times more massive than Earth, which makes it more comparable to the small gas giants Uranus and Neptune, at roughly half of their mass. Also, it orbits a tiny red dwarf star, much dimmer than our own Sun. Finally, it is extremely close to that small star, so that it is still searing hot.

At such a close distance, the planet could be tidally locked, keeping the same face toward its star at all times. Dr. Marcy said the temperature on the side of the planet facing the star would be 400 to 700 degrees, like "chicken roasting temperatures."

That is too warm for liquid water or ice, but it could be cold on the backside of planet, which, as Dr. Marcy said, "faces the darkness of the universe.

We wouldn't be particularly comfortable if Earth were anything like that.

If the speculation that it is rocky, and not a gas giant, is correct, it would be a bit more accurate to label it a Mercury-like, or perhaps Venus-like, planet. But, as with many of the extrasolar planets discovered to this point, our solar system has no comparable objects. The current means of detecting planets is geared, of necessity, to finding either very massive ones, like Jupiter and Saturn, or ones extraordinarily close to their parent star. Our system has no planets of the latter type, so one of the big surprises of this research since the mid-1990s is the large number of such planets being found.

Of course, this particular discovery is still fascinating. Its discoverers have every right to brag, since they are pushing current technology to its limits in detecting planets so small. But someday, perhaps within another decade, with new space-based instruments, we actually will discover Earth-like planets. So let's not get ahead of ourselves.

Peter

[hobbit709]

1. I think they mean

"earthlike' in terms of a rocky planet insted of a gas giant. Mercury, Venus, Earth and Mars have more in common with each other than with the outer gas giants.

[pmbryant]

6. Yes

But Mercury and Pluto are both rocky, and no one describes them as "Earth-like".

I'm afraid that overhyped headlines like this will get people jaded by the time we actually do discover planets much like Earth.

--Peter

[MoveOn90]

12. Mercury is a terrestrial planet,

which puts it in the same general group as Earth. Compared to the gas giants, it's very Earth-like.

The problem with Pluto is that many astronomers don't think it's an actual planet, but rather an escaped moon of Neptune, and/or just another Kuiper Belt object. Its dubious origins prevent it from being identified as a terrestrial planet.

[pmbryant]

13. Of course.

Welcome to DU, MoveOn90.

I have to disagree. The day Mercury is considered Earth-like is the day the phrase Earth-like ceases to have any meaning.

[Salviati]

2. To be fair though...

... if the speculation is correct, by a long shot it would be the most earth like planet discovered to date. And if it is tidally locked, then there would potentially be a longitudinal ring around the planet where conditions would be balanced between the searing heat of the starward side, and the bitter cold of the shadow side.

[BlueJazz]

4. So you mean the front side would be like Texas in Summer...

...and the Back side like Minnesota in Winter. :)

[smitty]

3. Earth-like?

I suspect that the astronomers mean "earth-like" in that it's a rocky planet--similar to Mercury, Venus, Earth and Mars. When you read the details its obvious that the planet is very different from the planet we live on. Still, it's a start; I'm impressed that they've found so many planets orbiting stars close (relatively speaking) to us.

[aeolian]

5. "earthlike mass"

They're physicists detecting orbiting bodies. All they can think of is mass, mass, mass, 'cause it's the key in all their equations. The planet is earthlike to them.

Pity them, the physicists, and donate generously when you see them on the street. Really. Especially to me. ...here, just give me your credit card numbers...

[pmbryant]

7. Well, its mass and orbit is about all we know about it now

So I can forgive them for not thinking beyond those quantities.

But I do see your point. Venus's mass is very similar to Earth's, and it, too, is far from "Earth-like."

--Peter

[aeolian]

8. Exactly. :)

[Kraklen]

9. Seems like the astronomers were perfectly correct.

A hot rocky planet 7 times the mass of Earth would be the most Earth-like planet found yet. Same order of magnitude and everything. Certainly not the behemoths several times the size of Jupiter they've been finding before.

[pmbryant]

11. perfectly

is a dog more "fish like" than a whale?

in this case the phrase "earth like" is rather meaningless i think

[phantom power]

10. I propse we name it Mesklin

in honor of Hal Clement.