Earth-sized planet around Alpha Centauri B discovered

[sorindafabico]

It looks like the nearer a Star is to us, the more difficult it is to detect planets around the star.
I wonder why?
Maybe it is something to do with it's glare.
The closer a star is, the more brilliant does it shine?
Well, it's time to run Space Engine again.........

If I understood well, this planet was only discovered now because it's proportionaly small (in mass) relative to the parent star - aparently, Alpha Centauri does not have gas giants. So, its gravitational pull on the star is very subtle.

But the glare of these close stars disturbs the search for planets there using the transit method, if I am not wrong.

 

[T.Neo]

Well, it's time to run Space Engine again.........

Ah, Space Engine! I was wondering when someone was going to bring that up.

There is discussion of it in this thread, including code to put into the config files for the planet to come up inside Space Engine.

 

[RisingFury]

This is interesting!

By the way, HARPS is the most or at least one of the most sensitive spectrographs we have that is dedicated to planet hunting. It can detect the velocity of the star to an accuracy of about 1 m/s.

 

[dgatsoulis]

I tried to calculate what kind of change in the wavelength ([math]\Delta\lambda[/math]) of the light from the star should HARPS be able to detect, in order to "catch" a 0.5 m/s radial velocity ([math]V_{\odot}[/math])

[math]\Delta\lambda[/math]=Change in wavelength [math]\lambda_o[/math] =resting wavelength (Orange light)[math]\approx 600 nm = 6 \cdot 10^{-7}m[/math]
[math]V_{\odot}[/math]= Star's motion = 0.5 m/s = [math]5\cdot 10^{-1}m/s[/math]
[math]c =[/math] speed of light [math]\approx 3\cdot 10^8 m/s[/math]



[math] \frac{\Delta{\lambda}}{\lambda_o}=\frac{V_{\odot}}{c} \Rightarrow \Delta{\lambda} = \frac{V_{\odot}\cdot \lambda_o}{c} = \frac{5 \cdot 10^{-1} \cdot 6 \cdot 10^{-7}}{3\cdot 10^8}=1 \cdot 10^{-15} m [/math]=1 picometers :blink:

If my calculation is correct, HARPS is able to detect a Doppler shift of one thousandth of a nanometer.

An Earth-sized planet in the habitable zone of a Sun-like star causes a radial velocity ~ 0.1 m/s
That means that the instrument must be able to detect a change of [math]0.2 \cdot 10^{-15} m[/math] (0.2 picometers) in wavelength.

 

[orb]

If you look at this image, you can see that they didn't exactly "detect" 0.5 m/s radial velocity directly, but instead they interpolated it from 4 years of observations:

(Source)​

SPACE.com: Nearby Earth-Sized Alien Planet Could Spur Interstellar Exploration

Discovery News: Alpha Centauri Bb: An Interstellar Target?

 

[N_Molson]

Smart. Just smart. :thumbup:

 

[Admiral_Ritt]

I wonder what kind of equiment you'd need to land on that world.

it's actually worse than DEMON :chainsaw: class planet.

It's a HADES class planet.

Land on the dark side,
Bring a suit with a 5000 KCAL Heat Sink.
Armored to withstand a Rock Hail.

If you want to land on the Sunnyside (as jock feat no doubt)
I wonder if there's any spacesuit that would allow you to walk/float
on the semi-liquid suface.

 

[Urwumpe]

DEMON class and HADES class planets are fiction. Try the reality, it is much more diverse.

The temperature will actually only raise by the fourth root of the energy input from the star. 16 times the energy means twice the temperature. Alpha Centauri B has only 0.5 solar luminosities, it means it produces only 1/2 of the energy per area at the same distance.

Ergo: 100 times closer to Earth means 10000 more energy per area (inverse square law), 0.5 luminosity makes this 5000. This means only 8.4 times the temperature as on the daylight side of the moon. This means about 1200°C - yes, that can mean liquid magma. But must not mean a liquid planet surface. Many minerals and materials will not melt at this temperature, others will directly sublime to gas.

 

[Gerdih]

I suppose it doesnt have atmosphere, maybe his rotation is locked? And what about tides on Alpha Centauri B? the planet is rising his orbit due to them or he have not enough mass? :hmm: this planet makes me wonder

 

[Urwumpe]

I suppose it doesnt have atmosphere, maybe his rotation is locked? And what about tides on Alpha Centauri B? the planet is rising his orbit due to them or he have not enough mass? :hmm: this planet makes me wonder

At this distance, it is very likely tidal locked.

 

[sorindafabico]

It is possible that this planet has migrated from the habitable zone to 0.06 AU due to perturbations from Alpha Centauri A? Imagine the possibility of ruins of an alien civilization there...

 

[MattBaker]

We already sent probes to seven other planets, no alien life found.
Although there is probably something living on another planet (everything from microbes to Vulcans...), it's highly unlikely you find something there. It's even hotter than Venus, if you drill 600-800 kilometer into the Earth you end up with the same temperature this planet has on his surface. If you want to search for aliens/ruins, look elsewhere, maybe Kepler 22-b, Gliese 581 g.

And keep in mind: As long as we can't travel with FTL-speed it's unlikely we send anything to another star/solar system, so until then you can speculate about alien ruins for years, you'll never know it...

 

[N_Molson]

FTL speed is not absolutely required for this one ; a near-lightspeed velocity would be enough. It would take several decades (and received data would be several years old), but the Voyager probes demonstrated it is possible to operate robotic spacecrafts on that timescale.

Still, accelerating an object like a space probe to 300.000 km/s requires an awesome lot of energy (remember, Earth escape velocity is only 11-12 km/s, which is ridiculous in comparison)...

And even worse, a braking burn is required as 1) it seems pretty useless to flash through the target system 2) emitted radiowaves would have a very low relative velocity and would take a near-infinite time to reach Earth. Which means you need to send much more than a "light" space probe...

So it seems pretty challenging...

 

[Izack]

2) emitted radiowaves would have a very low relative velocity and would take a near-infinite time to reach Earth.

The data would be severely redshifted, but the transmitter's velocity has no bearing on the velocity of its transmission, unless I'm misunderstanding.

 

[N_Molson]

The data would be severely redshifted, but the transmitter's velocity has no bearing on the velocity of its transmission, unless I'm misunderstanding.

Ah yes, probably. I guess that the radiowaves max. speed is the light of speed relatively to the observer. Relativity is not easy to figure. So yes the signal would be distorted but the velocity would still be c relative to us.

Now, does that mean that the transfer rates would be awful ? :hmm:

 

[Izack]

Now, does that mean that the transfer rates would be awful ? :hmm:

I can't imagine the transfer rates from Alpha Centauri could be anything but awful.

 

[Cairan]

hmm, tidaly locked so close...

Ok, so you'd have one side with a cooked-up, goey mineral soup on the dayside, transitionning to a solid olivine and pyroxene surface as you get closer to the terminator, finally getting plagioclase and quartz, and a lot of potassium feldspars and such on the nightside from the condensation of rock "vapor" deposited there over time... That's interesting!

 

[sorindafabico]

We already sent probes to seven other planets, no alien life found.
Although there is probably something living on another planet (everything from microbes to Vulcans...), it's highly unlikely you find something there. It's even hotter than Venus, if you drill 600-800 kilometer into the Earth you end up with the same temperature this planet has on his surface. If you want to search for aliens/ruins, look elsewhere, maybe Kepler 22-b, Gliese 581 g.

And keep in mind: As long as we can't travel with FTL-speed it's unlikely we send anything to another star/solar system, so until then you can speculate about alien ruins for years, you'll never know it...

Yes, yes, yes. But I'm not talking about life on a planet hotter than Venus. Just thinking - and it's not forbidden to imagine - if this planet could have migrated from a more human-friendly place to there due to perturbations and, from that point, imagining again about the possibility of an extinct alien civilization. Don't take it so seriously, I don't intend to write a paper about it...

---------- Post added at 05:39 AM ---------- Previous post was at 05:35 AM ----------

FTL speed is not absolutely required for this one ; a near-lightspeed velocity would be enough. It would take several decades (and received data would be several years old), but the Voyager probes demonstrated it is possible to operate robotic spacecrafts on that timescale.

Still, accelerating an object like a space probe to 300.000 km/s requires an awesome lot of energy (remember, Earth escape velocity is only 11-12 km/s, which is ridiculous in comparison)...

And even worse, a braking burn is required as 1) it seems pretty useless to flash through the target system 2) emitted radiowaves would have a very low relative velocity and would take a near-infinite time to reach Earth. Which means you need to send much more than a "light" space probe...

So it seems pretty challenging...

How about this?

 

[N_Molson]

How about this?

Well, I don't believe too much in the pulsed fusion concept... But that's another subject...

 

[RisingFury]

If you look at this image, you can see that they didn't exactly "detect" 0.5 m/s radial velocity directly, but instead they interpolated it from 4 years of observations:

(Source)​

SPACE.com: Nearby Earth-Sized Alien Planet Could Spur Interstellar Exploration

Discovery News: Alpha Centauri Bb: An Interstellar Target?

That's how it's always done. You need the planet's orbital period as well as the star's radial velocity in order to detect the planet.

Each of those dots with an error bar is a measurement of velocity, but velocity doesn't directly translate to a planet. The star could just happen to be flying towards or away from us. If, however, you detect a change of velocity in a sine pattern, you have your first hint that there's a planet there.


Not every sine pattern means a planet, though. Stars vibrate in all different manners. They can even contract and expand. In that case, the radius changes and the surface of the star can travel towards us or away from us, to create the illusion of a planet. There are methods to detect that, however.
Since not every part of the star's surface moves towards us at the same speed, the spectral lines broaden...


HARPS is so sensitive, that sometimes the many different vibrational modes of the star widen the spectral lines to the point where accuracy is lost because of that...