# Tag Info

69

The problem with finding a new planet in our solar system is not that it is too faint, but knowing where to look in a big, big sky. This putative planet 9 is likely to be in the range 20-28th magnitude. This is faint (especially at the faint end), but certainly not out of reach of today's big telescopes. I understand that various parts of the sky are ...

24

The reason why we can see exoplanets 13,000 light years away but not a planet 200 AU away (about 30 light-hours) is because these planets are found using different techniques. The planet discussed in the article I linked was discovered using a technique known as "microlensing," which requires a star to pass behind another star with a planet around it. The ...

22

To address your last point, there are several stars of which we have been able to resolve images i.e. see the star as more than just a featureless point. There is a list of these stars on Wikipedia (I love that they put the Sun at the top of the list - true but pedantic :-). The farthest away of the stars in the list is Epsilon Aurigae at about 2000 light ...

19

I'll add a theoretical limit to the actual record put forward by John Rennie. To image an object as more than a featureless "point source", it must be resolved by the telescope. The angular resolution $\theta$ of a telescope is: $$\theta\sim1.22\frac{\lambda}{D_{\rm aperture}}$$ $\lambda$ is the wavelength of light, $D_{\rm aperture}$ is the diameter of ...

16

Because there are so many planets out there! There just happens to be an entire web page dedicated to calculating that answer. Transits can only be detected if the planetary orbit is near the line-of-sight (LOS) between the observer and the star. This requires that the planet's orbital pole be within an angle of $d_*/a$ (part 1 of the figure below) ...

16

The reason is electron degeneracy pressure. The cores of giant planets are dense enough that the electrons in the gas occupy about $h^3$ of phase space each. The Pauli exclusion principle means that they cannot all occupy low energy/momentum states. This means that even at relatively cool temperatures the gas can still exert considerable pressure due to the ...

15

New research is suggesting that solar systems may be inherently unstable. You may have read recently that wandering inter-stellar planets may be more common than stars. The prediction is that planets frequently become ejected from their solar systems early in their formations, and wind up wandering deep space forever. There is a complicated interaction ...

14

There are a couple of resources for you to look over the list of CONFIRMED extra-solar planets. Wikipedia is always a nice starting point. Here is a list of the currently 53 known planetary SYSTEMS. And from that page, you can check out numerous other exoplanet details. This article from August 2010 Space.com lists 5 candidates. The definitive site ...

14

Yes. I'm not going to list all the stars here but it's easy to compile such a list. Wikipedia has a list of exoplanetary host stars. If you sort the table by ascending apparent magnitude and decide how bright "naked-eye stars" need to be, you can take as many as you like from the list by taking all the stars with smaller magnitudes. I think magnitude 6 is ...

13

Almost all exoplanets observed are near F, G, and K stars. In part, this is because astronomers are looking for earth-like planets, so they look at stars similar to our Sun, but there are also some physical reasons. Sahu et al (2006) have provided some evidence that red dwarfs (class M) are more likely to have planets than other spectral types, though it is ...

10

Given what we know about planetary formation (Link 1, Link 2, Link 3 and Link 4), and the theories around it, it would probably be a safe bet to say that ALL stars end up having some left over material that might become planets. I think the bigger question is how many of those planetary orbits stay stable enough throughout the life of the star? All these ...

10

(I just performed a bit of an edit on your question to have it align more with what I think you are asking as opposed to the overly speculative sentences you had. I hope you don't mind. :) And I will build on Andrew's answer (I hope he doesn't mind).) This is probably related to the question What are the prerequisites for considering any other planet to be ...

10

Stars are divided (this is only an approximate distinction) into Population I, Population II and Population III. Population I stars are the relatively young stars like the Sun that we see around us today, while Population II are older stars that have a low but non-zero metal content (in this context a metal is any element heavier than Helium i.e. those ...

8

The earliest stars did not have planets primarily due to a lack of metals. Metals in this sense is an element (with some extra properties that are not relevant in this context) heavier than helium. The very article that you linked to references this. This leads to the following: Stars without metals tend to not last very long. Metals in a star act to slow ...

8

Unfortunately, it's highly highly unlikely. We're barely even capable of identifying individual stars within the Andromeda galaxy (and the ones we can identify, if any, are almost all supergiants - these are pretty much the only stars we can identify in the Local Magellanic Clouds, which are closer than Andromeda). Even if we were able to identify individual ...

7

http://en.wikipedia.org/wiki/Methods_of_detecting_extrasolar_planets#Direct_imaging A shade used to block out a bright source in order to image a dim source right next to it is called a coronagraph. They are [EDIT: modestly sized] screens attached to the telescope itself, not [EDIT: huge] devices deployed far from the telescope. These are being used already,...

7

This is by no means a settled question; rather it is at the forefront of exoplanet research. There are several ideas out there, and I'll list a few. Migration via drag: In young stellar disks, there may be a bunch of leftover gas that can produce a drag force on planets. By the way, there is a subtle reason this works at all. Because gas will have some ...

7

You are correct that the standard for naming exoplanets is normally the lower-case letter after the star name in the order of discovery. So in our system, Earth would be Sol b. If there are multiple stars in the system, like 16 Cyg (which has 16 Cyg A and B), then the planet's lower-case letter would be appended to the star's, such as 16 Cyg Bb. So the ...

7

"Host star", or "host" for short, seems to fit the bill.

7

The plot below shows a model of how an isolated mass of gas (planet, brown dwarf) cools down with time, taken from Baraffe et al. (2003). The cooling tracks are labelled with mass in Jupiter masses. The time axis is logarithmic in years, the luminosity axis is lograrithmic in units of solar luminosities. Young brown dwarfs and giant planets are governed by ...

6

This question was asked a couple of years ago and things have changed since then. We now know that small planets are found around stars across a broad range of metallicities and that it is only the existence of giant planets that are affected by low metallicity. Nature article here. It was previously thought that small planets were more common around small ...

6

Not having been at the meeting, here's my take on it. It's becoming saturated in that it's the hot topic right now where there is a lot of funding so everyone is trying to get involved to some level. There is a lot of people competing for limited resouces and there is only so much that can be done with current technology.My wife was recently on a grant ...

6

I did some research and I think I can answer my question myself now, after all. I hope you find it interesting. As it turns out, the technology of the Kepler space telescope would indeed allow detection of all Solar system planets except Mercury and probably Mars, i.e. all of them are big enough to be seen by it from a distance of about 2,000 ly. However, ...

6

I'm not an expert but I believe the following is correct. The object PSO J318.5-22 is referred to as a "young L dwarf." An L dwarf is a type of brown dwarf, meaning a mass of hydrogen and other elements that is not large enough to fuse hydrogen. PSO J318.5-22 is Jupiter-sized, but I guess there is no particularly important difference between "failed stars" ...

6

We haven't detected planets millions of light years away. Right now the most distant is less than 20,000 light years away. Even for the planets we have detected, they are for the most part not "seen" or imaged directly. Instead they are found by the effect they have on the parent star (usually gravitational wobble or transit detection). In both cases, ...

5

Scientists can image exoplanets today, using coronagraphs and other techniques: The major difference from Sagan's speculation are the advances in adaptive optics that allow terrestrial observatories to perform in ways that vastly exceed the expectations of Sagan's time. Space-based observatories are awesome, but the sheer size of these instruments is ...

5

There is mounting evidence from the Kepler mission that these hot Jupiters migrated in by scattering other planets out. Of the 400-odd systems with multiple planets, almost none of them have a hot Jupiter. Statistically quite significant.

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