What is Nemesis?

[Loren Pechtel]

Yeah--I know it's not at all certain that it exists at all. Assume that it does.

Is it a planet? No--planets are defined as clearing their orbital. Nemesis is too far out to have accomplished this within the current life of the solar system.

The lesser bodies are called dwarf planets. So what is it, a giant dwarf planet???

 

[repoman]

Well, there is Nemesis the whack job's talk about and then there are possible fairly large objects that have just not been found yet. But they also must be small enough and/or far enough away that their gravitational influence is not detectable with our current accuracy.
http://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)

Maybe you are thinking about Nibiru, which is a truly barking mad idea. http://en.wikipedia.org/wiki/Nibiru_cataclysm

So, maybe with each increase with the size range of objects there is a corresponding type of search that is done that can exclude these objects. Brown dwarfs as cool as 150K temperature have supposedly been excluded out to 10 light years as an example.

Also each size of object can do different things to the objects it encounters. How big of a body would it take to throw a mass extinction object our way?

I would just say, keep to the science journals and somewhat decent websites (space.com is the low bar) about this topic. It is more accurate and more interesting. Conspiracy theories about this are so tiresome and boring.

 

[repoman]

What new telescopes or probes are coming down the pipeline that could have a better chance of finding one of these comet flingers?

 

[fromderinside]

It's a bump, capture, kind of sling (the flinger) and it is right there probably emitting light in your face right now.

 

[dystopian]

Nemesis, as I've heard it, is supposed to be a brown dwarf; which is essentially an object too big and massive to be considered a planet, but not quite massive enough to undergo fusion and become a proper star either. Of course, modern observations have made the idea of a brown dwarf companion to our sun ridiculous.

 

[skepticalbip]

Yeah--I know it's not at all certain that it exists at all. Assume that it does.

Is it a planet? No--planets are defined as clearing their orbital. Nemesis is too far out to have accomplished this within the current life of the solar system.

The lesser bodies are called dwarf planets. So what is it, a giant dwarf planet???

As I understand it, Nemesis was a proposed brown dwarf companion star to our sun in an elliptical orbit about 1.5 LY away (about a 26 million year orbital period). It was proposed to explain the apparent periodic mass extinctions. The idea was that it gravitationally disrupted bodies from the Oort cloud sending comets into the inner system that impacted the inner planets. The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

 

[Loren Pechtel]

Yeah--I know it's not at all certain that it exists at all. Assume that it does.

Is it a planet? No--planets are defined as clearing their orbital. Nemesis is too far out to have accomplished this within the current life of the solar system.

The lesser bodies are called dwarf planets. So what is it, a giant dwarf planet???

As I understand it, Nemesis was a proposed brown dwarf companion star to our sun in an elliptical orbit about 1.5 LY away (about a 26 million year orbital period). It was proposed to explain the apparent periodic mass extinctions. The idea was that it gravitationally disrupted bodies from the Oort cloud sending comets into the inner system that impacted the inner planets. The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

Yeah--but my question is what to call it if it's found.

 

[skepticalbip]

Yeah--but my question is what to call it if it's found.

Yeah--I know it's not at all certain that it exists at all. Assume that it does.

Is it a planet? No--planets are defined as clearing their orbital. Nemesis is too far out to have accomplished this within the current life of the solar system.

The lesser bodies are called dwarf planets. So what is it, a giant dwarf planet???

As I understand it, Nemesis was a proposed brown dwarf companion star to our sun in an elliptical orbit about 1.5 LY away (about a 26 million year orbital period). It was proposed to explain the apparent periodic mass extinctions. The idea was that it gravitationally disrupted bodies from the Oort cloud sending comets into the inner system that impacted the inner planets. The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

It would depend on its mass, if it exists and is found. If not massive enough to be a brown dwarf but still massive enough to be a planet, they may add the qualifier "extra-Oort" to the designation "planet".

 

[dystopian]

The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

People are, but scientists aren't really among them. I suppose it depends on your definition of 'large' I suppose. If something like Sedna falls into that definition, then sure. But the idea of there being anything substantially larger out there isn't taken very seriously anymore.

 

[dystopian]

Yeah--but my question is what to call it if it's found.

We started out naming all of the solar system's planets (and planet-like things) except Earth after Roman gods; with the addition of the likes of Sedna and Ixion, we're just calling them after deities and demigods period. We have a lot of those; so take your pick.

 

[skepticalbip]

The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

People are, but scientists aren't really among them. I suppose it depends on your definition of 'large' I suppose. If something like Sedna falls into that definition, then sure. But the idea of there being anything substantially larger out there isn't taken very seriously anymore.

NASA is still looking. They are still analysing the images from their WISE satellite... but are calling the hypothetical planet 'Tyche'.

http://www.nasa.gov/mission_pages/WISE/news/wise20110218.html


ETA:
Oops!! Just re-read. The final analysis of that data was due to be released in 2012.

 

[Loren Pechtel]

Yeah--but my question is what to call it if it's found.

We started out naming all of the solar system's planets (and planet-like things) except Earth after Roman gods; with the addition of the likes of Sedna and Ixion, we're just calling them after deities and demigods period. We have a lot of those; so take your pick.

It's amazing how people aren't getting the question here.

We have three classes of bodies:

1) Planets. Big enough to be shaped by gravity, they clear their orbit of other matter. (You can still get trojan point asteroids, though.)

2) Dwarf planets. Big enough to be shaped by gravity, they have not cleared their orbit of other matter.

3) Asteroids. Too small for gravity to have made them into balls.

Something far out in the cometary zone will not have cleared it's orbit, period--out there the process is simply too slow. Thus there can be no planets out there. Calling an ice giant a dwarf planet makes no sense, though.

Are we going to make up a new category??

 

[repoman]

If the object is bigger than at least as big as Mars and has a fairly circular orbit, I would think that it would be considered a planet by much of the general public.

The further you go out into the Oort Cloud, the slower everything orbits, so it would not have the time to clear the orbit. Earth has has around 4+ Billion circuits and Jupiter tens of millions of circuits to clear their orbits.

 

[Jokodo]

The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

People are, but scientists aren't really among them. I suppose it depends on your definition of 'large' I suppose. If something like Sedna falls into that definition, then sure. But the idea of there being anything substantially larger out there isn't taken very seriously anymore.

There's a lot of room for objects substantially larger than Sedna. The data from NASA's  Wide-field_Infrared_Survey_Explorer (WISE) at this time only rules out objects as large or larger than Jupiter at distances below 0.4 light years (but the paper ruling them out was only published a couple of months ago). A super-Jupiter sized object at e.g 0.6 lighyears (which would still put it within the Sun's zone of gravitational control), or a Neptune sized one at much closer distances cannot be ruled out. Not that it's particularly likely or anything.

Here's a quote:

I have used multi-epoch astrometry from the Wide-field Infrared Survey Explorer to perform a search for a distant companion to the Sun via its parallactic motion. I have not found an object of this kind down to W2 = 14.5. This limit corresponds to analogs of Saturn and Jupiter at 28,000 and 82,000 AU, respectively, according to models of the Jovian planets by Fortney and coworkers. Models of brown dwarfs by Burrows and coworkers predict fainter fluxes at a given mass for the age of the solar system, producing a closer distance limit of 26,000 AU [i.e., 0.4 light years - J.] for a Jupiter-mass brown dwarf.

Note, though, that this is only for objects with the age of the solar system. If we allow for the possibility of an object that hasn't formed along with the rest of the solar system (e.g., a much older rogue planet the sun has captured over the course of its existence), those limits could be substantially smaller since WISE is measuring the heat flow from an object - and at those distances, warming due to solar radiation is negligible. Since objects this size don't do fusion, what it really measures is the leftover heat from the aggregation + warming from radioactive decay - both of which an older object will have substantially less of. Of course, that's even less plausible - an object originating from outside the solar system is much more likely to be re-ejected in a parabola than permanently captured, due to high relative velocities.

(Incidently, in 2013 they found a binary brown dwarf system at 6.6 light years (the closest system to our Sun after Alpha Cen and Barnard's star), and another brown dwarf or possibly rogue planet at 7-ish light years just a couple of weeks ago. We really don't know our neighbourhood all that well yet.)

 

[dystopian]

Oops!! Just re-read. The final analysis of that data was due to be released in 2012.

Exactly, the most recent stuff I've read on the WISE planethunt says it came up empty; from the wikipedia article on Tyche: "in 2014, NASA announced that the WISE survey had ruled out any object as they had defined it."

 

[dystopian]

We have three classes of bodies:

1) Planets. Big enough to be shaped by gravity, they clear their orbit of other matter. (You can still get trojan point asteroids, though.)

2) Dwarf planets. Big enough to be shaped by gravity, they have not cleared their orbit of other matter.

3) Asteroids. Too small for gravity to have made them into balls.

Actually, we have a significantly larger number of classes than that.

Any new object we find at that distance that is not big enough to be a star, and not small enough to be an asteroid or comet, would instead fall under the category of 'Trans-Neptunian Object' (Assuming it doesn't fall outside the oort cloud, I suppose):


"A trans-Neptunian object (TNO; also written transneptunian object) is any minor planet in the Solar System that orbits the Sun at a greater average distance (semi-major axis) than Neptune.

The first trans-Neptunian object to be discovered was Pluto in 1930. It took until 1992 to discover a second trans-Neptunian object orbiting the Sun directly, (15760) 1992 QB1. Now over 1,200 trans-Neptunian objects appear on the Minor Planet Center's List Of Transneptunian Objects.[1] As of November 2009, two hundred of these have their orbits well-enough determined that they have been given a permanent minor planet designation.[2][3]

The largest known trans-Neptunian objects are Eris and Pluto, followed by Makemake and Haumea. The Kuiper belt, scattered disk, and Oort cloud are three conventional divisions of this volume of space,[4] though treatments vary and a few objects such as Sedna do not fit easily into any division."

 

[dystopian]

The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

People are, but scientists aren't really among them. I suppose it depends on your definition of 'large' I suppose. If something like Sedna falls into that definition, then sure. But the idea of there being anything substantially larger out there isn't taken very seriously anymore.

There's a lot of room for objects substantially larger than Sedna. The data from NASA's  Wide-field_Infrared_Survey_Explorer (WISE) at this time only rules out objects as large or larger than Jupiter at distances below 0.4 light years (but the paper ruling them out was only published a couple of months ago). A super-Jupiter sized object at e.g 0.6 lighyears (which would still put it within the Sun's zone of gravitational control), or a Neptune sized one at much closer distances cannot be ruled out. Not that it's particularly likely or anything.

Fair enough, I thought the WISE survey was searching for smaller planets than Jupiter/Saturn as well, but it seems I was wrong.

(Incidently, in 2013 they found a binary brown dwarf system at 6.6 light years (the closest system to our Sun after Alpha Cen and Barnard's star), and another brown dwarf or possibly rogue planet at 7-ish light years just a couple of weeks ago. We really don't know our neighbourhood all that well yet.)

Fun fact; Luhman-16 is actually the location of a hidden space station in a sci-fi novel I'm writing.

 

[Jokodo]

The idea of a brown dwarf that close has pretty much been dropped but people are still searching for a large planetary sized body at that distance.

People are, but scientists aren't really among them. I suppose it depends on your definition of 'large' I suppose. If something like Sedna falls into that definition, then sure. But the idea of there being anything substantially larger out there isn't taken very seriously anymore.

There's a lot of room for objects substantially larger than Sedna. The data from NASA's  Wide-field_Infrared_Survey_Explorer (WISE) at this time only rules out objects as large or larger than Jupiter at distances below 0.4 light years (but the paper ruling them out was only published a couple of months ago). A super-Jupiter sized object at e.g 0.6 lighyears (which would still put it within the Sun's zone of gravitational control), or a Neptune sized one at much closer distances cannot be ruled out. Not that it's particularly likely or anything.

Fair enough, I thought the WISE survey was searching for smaller planets than Jupiter/Saturn as well, but it seems I was wrong.<snip>

The way I understand it, the point is that it can only detect objects above a certain surface temperature (70–100 K according to Wiki). That's good enough for objects without an intrinsic heat source in the inner solar system (i.e., asteroids, indeed one of its main targets), but when it comes to the outer solar system, solar radiation isn't enough to warm an object beyond the threshold, and thus it'll only detect objects large enough to have retained a heat source.

 

[repoman]

When the James Webb Space Telescope goes up, what will it be able to see of Luhman-16 and WISE 0855–0714? Also, how cold can JWST see? I know that it is near infrared for the most part.

 

[Uwe]

http://iopscience.iop.org/article/10.3847/0004-6256/151/2/22

We find that the observed orbital alignment can be maintained by a distant eccentric planet with mass ~>10 m[earth masses]