WI Epsilon Indi B in Solar System

What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi A?

B is allegedly 1500 a. u. from A. Does someone know exactly how far in
front of or behind A, and on which orbit?

Anyway, imagine Epsilon Indi B orbiting on a circular orbit 1500 a. u.
from Sun.

Ba is allegedly 47 Jupiter masses and 1,3 milliards of years old. It is
known to have temperature of about 1000 Celsius.

Sun Ba at 4,5 milliards of years would be cooler... how much?

In any case, it would radiate no visible light.

It is about the size of Jupiter (maximum cold mass!). At 50 times the
distance to Pluto in perihelion, and roughly 60 times the diametre, it
would be slightly wider. And it would receive 2500 times less light...
meaning that in reflected light of Sun, it would be 8,5 magnitudes
dimmer. Much dimmer than Charon, Quaoar or Sedna, it would be
invisible.

Would anyone discover it as a modest source of infrared?

Or would an object spanning some 0,13 arc seconds disc and covering
some 270 arc seconds over the yearly parallax of the Earth, 20 seconds
per year on orbit, show up by occulting?

Or would it gravitationally lens the stars behind?

Also, what about Bb? Epsilon Indi Bb is known to be about 600 Celsius
at the age of 1,3 milliards of years and allegedly 27 Jupiter masses.
Would an object older than this, at 4,5 milliards of years, be
discovered in infrared?

"c" == chornedsnorkack writes:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A?

c B is allegedly 1500 a. u. from A. Does someone know exactly how far
c in front of or behind A, and on which orbit?

I haven't found anything in a quick search, other than that it might
lie nearly in the plane of the sky (McCaughrean et al. 2004).

c Anyway, imagine Epsilon Indi B orbiting on a circular orbit 1500
c a. u. from Sun.

c Ba is allegedly 47 Jupiter masses and 1,3 milliards of years
c old. It is known to have temperature of about 1000 Celsius.

c Sun Ba at 4,5 milliards of years would be cooler... how much?

c In any case, it would radiate no visible light.

Kirkpatrick (2005) summarizes various cooling curves from other
authors. There is some uncertainty, due to our lack of understanding
of dust and cloud formation in the atmospheres of these objects.
Nonetheless, from his curves, I estimate that a T dwarf with a
temperature of about 1000 K and an age of about 1 Gyr is expected to
have a temperature of order 500 K at an age of about 4.5 Gyr.


c It is about the size of Jupiter (maximum cold mass!). At 50 times
c the distance to Pluto in perihelion, and roughly 60 times the
c diametre, it would be slightly wider. And it would receive 2500
c times less light... meaning that in reflected light of Sun, it
c would be 8,5 magnitudes dimmer. Much dimmer than Charon, Quaoar or
c Sedna, it would be invisible.

c Would anyone discover it as a modest source of infrared?

Let's see. In the discovery observations, the combined system has an
infrared J-band magnitude of approximately 12. That's at a distance
of 3.6 pc. Move it about 500 times closer (to a distance of about
1500 pc). That means that it should become about 13.5 magnitudes
brighter. Its apparent J-band magnitude would be approximately -1.5.


Ah, but these calculations are for eps Ind Ba at its current
temperature. Suppose we consider a similar object but with a
temperature that is a factor of 2 lower, consistent with the notion
that it is 4.5 Gyr old. A factor of 2 in temperature should
correspond to a factor of 16 in luminosity which would be 3
magnitudes. So our hypothetical Sun Ba would be expected to have a
J-band magnitude of 1.5.

There have been all-sky surveys in the J band (e.g., 2MASS). I think
there's little chance that they would have missed either a -1.5 or 1.5
magnitude object. (Missing a -1.5 magnitude object would be like
conducting a survey at visual wavelengths and not seeing Sirius.)

Also note that the source of its infrared radiation cannot be
reflection from eps Ind A. That star has a spectral type K4.5, so
while a bit redder than the Sun, it is also dimmer.


c Also, what about Bb? Epsilon Indi Bb is known to be about 600
c Celsius at the age of 1,3 milliards of years and allegedly 27
c Jupiter masses. Would an object older than this, at 4,5 milliards
c of years, be discovered in infrared?

Without running the numbers, I'd still expect a hypothetical Sun Bb,
similar to eps Ind Bb but older, to still be detectable easily.

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Joseph Lazio wrote:
"c" == chornedsnorkack writes:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A?

c B is allegedly 1500 a. u. from A. Does someone know exactly how far
c in front of or behind A, and on which orbit?

I haven't found anything in a quick search, other than that it might
lie nearly in the plane of the sky (McCaughrean et al. 2004).

c Anyway, imagine Epsilon Indi B orbiting on a circular orbit 1500
c a. u. from Sun.

c Ba is allegedly 47 Jupiter masses and 1,3 milliards of years
c old. It is known to have temperature of about 1000 Celsius.

c Sun Ba at 4,5 milliards of years would be cooler... how much?

c In any case, it would radiate no visible light.

Kirkpatrick (2005) summarizes various cooling curves from other
authors. There is some uncertainty, due to our lack of understanding
of dust and cloud formation in the atmospheres of these objects.
Nonetheless, from his curves, I estimate that a T dwarf with a
temperature of about 1000 K and an age of about 1 Gyr is expected to
have a temperature of order 500 K at an age of about 4.5 Gyr.


c It is about the size of Jupiter (maximum cold mass!). At 50 times
c the distance to Pluto in perihelion, and roughly 60 times the
c diametre, it would be slightly wider. And it would receive 2500
c times less light... meaning that in reflected light of Sun, it
c would be 8,5 magnitudes dimmer. Much dimmer than Charon, Quaoar or
c Sedna, it would be invisible.

c Would anyone discover it as a modest source of infrared?

Let's see. In the discovery observations, the combined system has an
infrared J-band magnitude of approximately 12. That's at a distance
of 3.6 pc. Move it about 500 times closer (to a distance of about
1500 pc). That means that it should become about 13.5 magnitudes
brighter. Its apparent J-band magnitude would be approximately -1.5.


Ah, but these calculations are for eps Ind Ba at its current
temperature. Suppose we consider a similar object but with a
temperature that is a factor of 2 lower, consistent with the notion
that it is 4.5 Gyr old. A factor of 2 in temperature should
correspond to a factor of 16 in luminosity which would be 3
magnitudes. So our hypothetical Sun Ba would be expected to have a
J-band magnitude of 1.5.

There have been all-sky surveys in the J band (e.g., 2MASS). I think
there's little chance that they would have missed either a -1.5 or 1.5
magnitude object. (Missing a -1.5 magnitude object would be like
conducting a survey at visual wavelengths and not seeing Sirius.)

So, it would be noted in 2MASS. Would an near-IR object this bright
have been noticed before 2MASS survey?

Also note that the source of its infrared radiation cannot be
reflection from eps Ind A. That star has a spectral type K4.5, so
while a bit redder than the Sun, it is also dimmer.


c Also, what about Bb? Epsilon Indi Bb is known to be about 600
c Celsius at the age of 1,3 milliards of years and allegedly 27
c Jupiter masses. Would an object older than this, at 4,5 milliards
c of years, be discovered in infrared?

Without running the numbers, I'd still expect a hypothetical Sun Bb,
similar to eps Ind Bb but older, to still be detectable easily.

How cold objects would be detectable?

Jupiter, at 5 a. u. is about 120 K temperature and radiates twice the
heat received from Sun. So, if Jupiter were at 1500 a. u. it would
still have temperature of about 100 K.

Would it be seen in IR in absence of visible reflection showing where
to look for IR radiation?

"c" == chornedsnorkack writes:

c Joseph Lazio wrote:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A?
[...]
c Would anyone discover it as a modest source of infrared?

In the discovery observations, the combined system has an infrared
J-band magnitude of approximately 12. That's at a distance of 3.6
pc. Move it about 500 times closer (to a distance of about 1500
pc). That means that it should become about 13.5 magnitudes
^^
Clearly I meant 1500 AU.

brighter. Its apparent J-band magnitude would be approximately
-1.5.

Ah, but these calculations are for eps Ind Ba at its current
temperature. [...] So our hypothetical Sun Ba would be expected
to have a J-band magnitude of 1.5.

There have been all-sky surveys in the J band (e.g., 2MASS). I
think there's little chance that they would have missed either a
-1.5 or 1.5 magnitude object. (Missing a -1.5 magnitude object
would be like conducting a survey at visual wavelengths and not
seeing Sirius.)

c So, it would be noted in 2MASS. Would an near-IR object this bright
c have been noticed before 2MASS survey?

There were the IRAS surveys. The shortest wavelength survey was at 12
microns. One would have to run the numbers, but, again, a 1.5 J-band
magnitude object is bright, really bright. I don't see how IRAS could
have missed it (short of extreme molecular absorption in the object's
atmosphere).

c Also, what about Bb? Epsilon Indi Bb is known to be about 600
c Celsius at the age of 1,3 milliards of years and allegedly 27
c Jupiter masses. Would an object older than this, at 4,5 milliards
c of years, be discovered in infrared?

Without running the numbers, I'd still expect a hypothetical Sun
Bb, similar to eps Ind Bb but older, to still be detectable easily.

c How cold objects would be detectable?

c Jupiter, at 5 a. u. is about 120 K temperature and radiates twice
c the heat received from Sun. So, if Jupiter were at 1500 a. u. it
c would still have temperature of about 100 K.

Above, I concluded that a 500 K object at a distance of 1500 AU would
have a J-band magnitude of 1.5. A 100 K object would be about 7
magnitudes dimmer, or magnitude 8.5. A quick check of the 2MASS
documentation indicates that, at J band, it should be complete down to
15.8. Even a 100 K object should still be detectable.

(Of course, I've made a few assumptions, such as ignoring any effects
due to molecular line absorption, that the radius of the various
objects are all about the same. To zeroth order, these seem reasonable.)


c Would it be seen in IR in absence of visible reflection showing
c where to look for IR radiation?

Yes. One doesn't need to see something via visible reflection in
order to look for IR radiation from it. One can observe the sky at IR
wavelengths without regard to how the sky looks at visible
wavelengths. That was part of the point behind IRAS, 2MASS, and other
surveys in the IR. I encourage you to visit the 2MASS site at URL:
http://www.ipac.caltech.edu/2mass/ .

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

Joseph Lazio wrote:
"c" == chornedsnorkack writes:

c Joseph Lazio wrote:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A?
[...]
c Would anyone discover it as a modest source of infrared?

In the discovery observations, the combined system has an infrared
J-band magnitude of approximately 12. That's at a distance of 3.6
pc. Move it about 500 times closer (to a distance of about 1500
pc). That means that it should become about 13.5 magnitudes
^^
Clearly I meant 1500 AU.

brighter. Its apparent J-band magnitude would be approximately
-1.5.

Ah, but these calculations are for eps Ind Ba at its current
temperature. [...] So our hypothetical Sun Ba would be expected
to have a J-band magnitude of 1.5.

There have been all-sky surveys in the J band (e.g., 2MASS). I
think there's little chance that they would have missed either a
-1.5 or 1.5 magnitude object. (Missing a -1.5 magnitude object
would be like conducting a survey at visual wavelengths and not
seeing Sirius.)

c So, it would be noted in 2MASS. Would an near-IR object this bright
c have been noticed before 2MASS survey?

There were the IRAS surveys. The shortest wavelength survey was at 12
microns. One would have to run the numbers, but, again, a 1.5 J-band
magnitude object is bright, really bright. I don't see how IRAS could
have missed it (short of extreme molecular absorption in the object's
atmosphere).

c Also, what about Bb? Epsilon Indi Bb is known to be about 600
c Celsius at the age of 1,3 milliards of years and allegedly 27
c Jupiter masses. Would an object older than this, at 4,5 milliards
c of years, be discovered in infrared?

Without running the numbers, I'd still expect a hypothetical Sun
Bb, similar to eps Ind Bb but older, to still be detectable easily.

c How cold objects would be detectable?

c Jupiter, at 5 a. u. is about 120 K temperature and radiates twice
c the heat received from Sun. So, if Jupiter were at 1500 a. u. it
c would still have temperature of about 100 K.

Above, I concluded that a 500 K object at a distance of 1500 AU would
have a J-band magnitude of 1.5. A 100 K object would be about 7
magnitudes dimmer, or magnitude 8.5.

Does this logic hold? Yes, the total bolometric magnitude of a body 5
times colder would be 7 magnitudes lower. But one would expect that a
very much biger portion of the radiation would be in far IR, nor in
near IR like J-band.

A quick check of the 2MASS
documentation indicates that, at J band, it should be complete down to
15.8. Even a 100 K object should still be detectable.

(Of course, I've made a few assumptions, such as ignoring any effects
due to molecular line absorption, that the radius of the various
objects are all about the same. To zeroth order, these seem reasonable.)


c Would it be seen in IR in absence of visible reflection showing
c where to look for IR radiation?

Yes. One doesn't need to see something via visible reflection in
order to look for IR radiation from it. One can observe the sky at IR
wavelengths without regard to how the sky looks at visible
wavelengths. That was part of the point behind IRAS, 2MASS, and other
surveys in the IR. I encourage you to visit the 2MASS site at URL:
http://www.ipac.caltech.edu/2mass/ .

But are the detection thresholds for weak objects identical for general
all-sky surveys and searching for a specific location?

In article ,
Joseph Lazio writes:
Kirkpatrick (2005) summarizes various cooling curves from other
authors. There is some uncertainty, due to our lack of understanding
of dust and cloud formation in the atmospheres of these objects.
Nonetheless, from his curves, I estimate that a T dwarf with a
temperature of about 1000 K and an age of about 1 Gyr is expected to
have a temperature of order 500 K at an age of about 4.5 Gyr.

I got slightly higher, maybe 600 K, but there's a lot of uncertainty.
According to Sterzik et al. (2005), there's also a lot of uncertainty
about the actual effective temperatures of both components of epsilon
Indi B.

Let's see. In the discovery observations, the combined system has an
infrared J-band magnitude of approximately 12. That's at a distance
of 3.6 pc. Move it about 500 times closer (to a distance of about
1500 AU). That means that it should become about 13.5 magnitudes
brighter. Its apparent J-band magnitude would be approximately -1.5.

Indeed.

Ah, but these calculations are for eps Ind Ba at its current
temperature. Suppose we consider a similar object but with a
temperature that is a factor of 2 lower, consistent with the notion
that it is 4.5 Gyr old. A factor of 2 in temperature should
correspond to a factor of 16 in luminosity which would be 3
magnitudes. So our hypothetical Sun Ba would be expected to have a
J-band magnitude of 1.5.

While the luminosity drops by a factor of 16, the drop in flux
density is larger at shorter wavelengths. For 500 K, J band is well
on the Wien side of the Planck curve, and the actual drop is more
like 12 magnitudes. That makes a "4 Gyr eps Indi Ba" at 1500 AU
about magnitude J=10.5.

Things are a lot better at K, where the aging drop is only about
7 mag. And at 12 microns, the drop is only about 1.6 mag. The
actual 12-micron flux density is about 6 mJy for each component, so
either one even after aging would be around magnitude -4 at 12
microns. That would make it one of the brightest objects in the sky,
easily visible to IRAS unless located in the 5% of the sky IRAS
didn't survey.

There have been all-sky surveys in the J band (e.g., 2MASS). I think
there's little chance that they would have missed either a -1.5 or 1.5
magnitude object.

Right. A 1 Gyr "eps Indi Ba" would have been one of the brightest
objects in the original Two Micron Sky Survey unless its declination
was south of -33 degrees. At 4 Gyr, it would have been below the
survey limit but easily visible to 2MASS, which covered the whole
sky. The one limitation I can think of would be if the proper motion
is large, 2MASS data-processing might have rejected the object. I
don't know enough about the catalog construction to say whether this
is possible or not.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

"c" == chornedsnorkack writes:

c Joseph Lazio wrote:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A? [...]
c Would anyone discover it as a modest source of infrared?

[What about Jupiter?]
c Jupiter, at 5 a. u. is about 120 K temperature and radiates twice
c the heat received from Sun. So, if Jupiter were at 1500 a. u. it
c would still have temperature of about 100 K.

Above, I concluded that a 500 K object at a distance of 1500 AU
would have a J-band magnitude of 1.5. A 100 K object would be
about 7 magnitudes dimmer, or magnitude 8.5.

c Does this logic hold? Yes, the total bolometric magnitude of a body
c 5 times colder would be 7 magnitudes lower. But one would expect
c that a very much biger portion of the radiation would be in far IR,
c nor in near IR like J-band.

Steve Willner corrected my post on this point. Yes, J band is not the
best band, but one would not have to go into the far IR. At 12
microns, one of the bands surveyed by IRAS, our hypothetical object
would still be one of the brightest objects in the sky.

[...]
c Would it be seen in IR in absence of visible reflection showing
c where to look for IR radiation?

Yes. One doesn't need to see something via visible reflection in
order to look for IR radiation from it. One can observe the sky at
IR wavelengths without regard to how the sky looks at visible
wavelengths. That was part of the point behind IRAS, 2MASS, and
other surveys in the IR. I encourage you to visit the 2MASS site
at URL: http //www.ipac.caltech.edu/2mass/ .

c But are the detection thresholds for weak objects identical for
c general all-sky surveys and searching for a specific location?

I don't understand your reference to "weak objects." A hypothetical
solar companion, similar to eps Ind Ba or eps Ind Bb, would be one of
the brightest objects in the IR sky. A Jupiter-mass companion would
be somewhat fainter, but I suspect far above the IRAS detection
threshold.


--
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No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

Joseph Lazio wrote:
"c" == chornedsnorkack writes:

c Joseph Lazio wrote:

c What would happen if Epsilon Indi B orbited Sun, not Epsilon Indi
c A? [...]
c Would anyone discover it as a modest source of infrared?

[What about Jupiter?]
c Jupiter, at 5 a. u. is about 120 K temperature and radiates twice
c the heat received from Sun. So, if Jupiter were at 1500 a. u. it
c would still have temperature of about 100 K.

Above, I concluded that a 500 K object at a distance of 1500 AU
would have a J-band magnitude of 1.5. A 100 K object would be
about 7 magnitudes dimmer, or magnitude 8.5.

c Does this logic hold? Yes, the total bolometric magnitude of a body
c 5 times colder would be 7 magnitudes lower. But one would expect
c that a very much biger portion of the radiation would be in far IR,
c nor in near IR like J-band.

Steve Willner corrected my post on this point. Yes, J band is not the
best band, but one would not have to go into the far IR. At 12
microns, one of the bands surveyed by IRAS, our hypothetical object
would still be one of the brightest objects in the sky.

[...]
c Would it be seen in IR in absence of visible reflection showing
c where to look for IR radiation?

Yes. One doesn't need to see something via visible reflection in
order to look for IR radiation from it. One can observe the sky at
IR wavelengths without regard to how the sky looks at visible
wavelengths. That was part of the point behind IRAS, 2MASS, and
other surveys in the IR. I encourage you to visit the 2MASS site
at URL: http //www.ipac.caltech.edu/2mass/ .

c But are the detection thresholds for weak objects identical for
c general all-sky surveys and searching for a specific location?

I don't understand your reference to "weak objects." A hypothetical
solar companion, similar to eps Ind Ba or eps Ind Bb, would be one of
the brightest objects in the IR sky. A Jupiter-mass companion would
be somewhat fainter, but I suspect far above the IRAS detection
threshold.

Then where is the threshold for such surveys, in respect to gas giants?

There are the small, roughly 2000 km in diametre (and cold) objects
Xena and Sedna, at about 90 a. u. They were discovered in visual
surveys - not IR surveys - but once found, they could, with difficulty,
be seen in IR.

Sedna has aphelion at 900 a. u., so there can be large bodies so far
out...

At 1500 a. u.... Jupiter radiates a lot in IR. So does Saturn, with
luminosity something like a fourth of Jupiter. Neptune radiates, too -
though I think its luminosity is something like 50 times smaller than
Saturn.

But Uranus, very close to Neptune in mass and density, does NOT
radiate, except of course because of solar heating.

Would an Uranus-like giant at 1500 a. u. be visible in IR? What about
Neptune?

wrote:
Ba is allegedly 47 Jupiter masses and 1,3 milliards of years old.

Is "milliard" a generally accepted English term for "billion" now?

That would be interesting - I'm from Denmark, and in Danish the word
for "billion" is in fact "milliard"...

- Tue

"Tue Sorensen" wrote in message
ups.com...
wrote:
Ba is allegedly 47 Jupiter masses and 1,3 milliards of years old.

Is "milliard" a generally accepted English term for
"billion" now?

No it is not. People in the UK might understand it but North Americans will
not.


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