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View Full Version : Exoplanets that weren't (or, Mourning for Barnard's Star b)



Roger E. Moore
2016-Dec-30, 10:37 PM
To start with, I am 61 years old, so I remember a lot of junk that others here might not, such as all the exoplanets discovered by astronomers from the 1940s through about 1975. I loved those planets. Then, as if my evil magic, they suddenly all went away. I was dumbfounded. Where was 61 Cygni C? Barnard's Star b (and c)? YOU CAN'T DO THIS TO AN ASTRONOMY NERD! But they were gone and never came back, except for epsilon Eridani, thank heaven.

I am doing some deep research lately to find out how many exoplanets (once called astrometric binaries, unseen companions, planetars, variable proper motion stars, and similar names) were once believed to have existed, and to locate those astronomy papers "proving" those planets existed (or did not exist). Attached is my little cheat sheet so far. I've saved many papers I found online and will soon give links to them and much more information.

A few odd things: Many of these last-century exoplanet papers have Dr. P. van de Kamp's name (vdK) attached to them, not just ones about Barnard's Star. Also, many of the writers were using the same altered telescope as vdK, or worked in association with him at Sproul Observatory, or were even related to him. (Reuyl is one.) Very strange stuff. And VB8b's "discovery" about 1985 served to expand the study of brown dwarfs.

Also, 70 Ophiuchi was thought to have had planets back in the 1700s and 1800s. I was amazed.

Take a look at the JPG pic of my Excel database (greatly in need of expansion) and toss in your thoughts. Anyone else remember 70 Ophiuchi having planets besides myself? :)

The Backroad Astronomer
2016-Dec-30, 10:55 PM
The entire history of Bernard's star planet was discussed in the book Looking for Earths by Alan Boss, it also discusses a lot of theory and history of looking for planets upto 1998. Bernards Stars planet planet go dismissed because they telescope used to take the measurements had a couple of faults that led to Van de Kamp to thinking there was at first one planet, then 2 and 3 planets around the star. That is the nature of science.

Roger E. Moore
2017-Jan-02, 08:10 PM
This topic is much more complicated than I had thought. I am still collecting research papers online for the star systems named in the earlier attachment.

What is most interesting is that many of these stars have had documented suspicions they had planetary systems dating back decades before the "definitive"papers announcing their (incorrect) discovery. Barnard's Star, for instance, had attracted Dr. van de Kamp's attention long before his 1963 announcement of a super-Jupiter planet orbiting it. 70 Ophiuchi and 61 Cygni have very long histories of planetary "discoveries" and refutations of same.

Hal Clement, the SF author of Mission of Gravity, wrote a follow-up novel called Star Light, which was set in the same story universe as the first novel. Both involved giant planets thought to orbit 61 Cygni A and Lalande 21185. Would have liked to see the story arc continue with stories about other (disproven) giant planets. Excellent work on the background making them very realistic.

Just came across reports of Sirius C, too.

Roger E. Moore
2017-Jan-02, 08:13 PM
Quick note: one valuable method for researching old astronomy papers is to use this format for Google:

site:adsabs.harvard.edu/ [insert keywords here, separated by commas, without the brackets]

The "site:" bit targets that one websiter and gives you much better results than the search engine for the website itself.

Roger E. Moore
2017-Jan-02, 08:40 PM
Here is an example of the early publication of "unseen companions" to nearby stars from 1945, in which Dr. van de Kamp says Barnard's Star and Lalande 21185 have such companions.

http://adsabs.harvard.edu/full/1945PASP...57...34V

The detail of the 1963 paper is not there, but the star is targeted as giving off signs it was an astrometric binary. Disproven later, yes, but still pretty early on.

antoniseb
2017-Jan-03, 12:24 AM
I don't have much to add here, but I am amused and entertained by the topic, and appreciate your efforts here.
Also, thanks for picking up the Fun Papers thread.

Roger E. Moore
2017-Jan-03, 03:26 AM
I don't have much to add here, but I am amused and entertained by the topic, and appreciate your efforts here.
Also, thanks for picking up the Fun Papers thread.

You are most welcome. The Era of Planets That Weren't is one of hobby-horses. It's always bugged me that what I had so counted on being real turned out not to be, though many scientists like Dr. Asimov and A.C. Clarke included mention of them in their works.

Working on a table showing planetary stats as they were thought to be. 70 Ophiuchi C, for instance had very specific stats as far back as 1932.

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1932LicOB..16...24B&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf

KaiYeves
2017-Jan-03, 03:31 AM
What a fascinating research topic. The "dead-ends" and mistakes in science are often just as fascinating as the stories of how the truth was discovered!

George
2017-Jan-03, 10:37 PM
You are most welcome. The Era of Planets That Weren't is one of hobby-horses. It's always bugged me that what I had so counted on being real turned out not to be, though many scientists like Dr. Asimov and A.C. Clarke included mention of them in their works.

Working on a table showing planetary stats as they were thought to be. 70 Ophiuchi C, for instance had very specific stats as far back as 1932.

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1932LicOB..16...24B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf Astro history is indeed fun. Though this article doesn't seem to suggest something other than a dwarf star at high inclination, I wasn't clear if 70 Ophiuchi was a binary so I went to Wiki and the fun began. Look at the planetary claims dating back to 1855 here (https://en.wikipedia.org/wiki/70_Ophiuchi). Fun stuff!

loglo
2017-Jan-04, 12:07 AM
Here is an example of the early publication of "unseen companions" to nearby stars from 1945, in which Dr. van de Kamp says Barnard's Star and Lalande 21185 have such companions.

http://adsabs.harvard.edu/full/1945PASP...57...34V

The detail of the 1963 paper is not there, but the star is targeted as giving off signs it was an astrometric binary. Disproven later, yes, but still pretty early on.
It is ironic that George Gatewood, who had put the nail in the coffin of van de Kamp's planet at Barnard's Star in 1973, published his own detection of planets at Lalande 21185 in 1997 after twice refuting vdK's earlier detection of a planet there as well.

If you have not read it I recommend Mayor and Frei's "New Worlds in the Cosmos". It has a fair bit of history of the search for exoplanets in the run up to Mayor and Queloz's discovery at 51 Pegasi.

Roger E. Moore
2017-Jan-04, 03:08 AM
Astro history is indeed fun. Though this article doesn't seem to suggest something other than a dwarf star at high inclination, I wasn't clear if 70 Ophiuchi was a binary so I went to Wiki and the fun began. Look at the planetary claims dating back to 1855 here (https://en.wikipedia.org/wiki/70_Ophiuchi). Fun stuff!

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1855MNRAS..15..228J&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf

There is the actual article. An 1854 article mentions difficulty figuring out the orbit of 70 Oph.

Here is a later article, 1895, about a third "dark body".

http://adsabs.harvard.edu/full/1895AJ.....15..180S

Roger E. Moore
2017-Jan-04, 03:18 AM
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1974AJ.....79..491V&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf

Above is the 1974 false alarm about a planet around epsilon Eridani, which does indeed have at least one planet but NOT this one.

The jury is still out of Lalande 21185, as Gatewood thought he found a giant planet there in the 1990s.

dtilque
2017-Jan-04, 09:21 AM
You may (or may not) want to add PSR B1829-10 to your list.

antoniseb
2017-Jan-04, 02:08 PM
Hmmm. I hadn't heard that PSR B1829-10 had been retracted. Knowing that would have saved some time during an ATM argument I was having here 12 years ago. Thanks dtilque!

grapes
2017-Jan-04, 06:15 PM
There are long conversations that we are having, it's just that simple

dtilque
2017-Jan-04, 09:08 PM
Hmmm. I hadn't heard that PSR B1829-10 had been retracted. Knowing that would have saved some time during an ATM argument I was having here 12 years ago. Thanks dtilque!

It was retracted about half a year after it was reported. However, it was immediately replaced by the discovery of two planets around a different pulsar: PSR B1257+12. That discovery has not been retracted, and in fact, a third planet has since been discovered there.

Roger E. Moore
2017-Jan-05, 03:36 AM
http://www.slate.com/blogs/bad_astronomy/2016/12/09/an_astronomer_claimed_to_have_found_an_exoplanet_1 60_years_ago.html

Someone we know got the same idea I did. :) Much more eloquent writer, and I tip my cap to him.

(See if you can find the misspelling in the illustration caption.)

Roger E. Moore
2017-Jan-05, 03:42 AM
Here's part of what I've been working on: a list of 61 Cygni C resources with dates and data. It is not finished and the links don't work (PNG of an Excel file) but maybe it helps. Enjoy, and note the Russian contributions!

thoth II
2017-Jan-05, 07:55 PM
I'm 60 on my birthday, so I also remember a lot of these first-supposed exoplanets, I remember especially Barnard's Star. From my research, Kepler telescope has already confirmed discovery of 2000 earth-like planets, but it estimates there might be as many as 40 billion earth like planets in the Milky Way alone.



To start with, I am 61 years old, so I remember a lot of junk that others here might not, such as all the exoplanets discovered by astronomers from the 1940s through about 1975. I loved those planets. Then, as if my evil magic, they suddenly all went away. I was dumbfounded. Where was 61 Cygni C? Barnard's Star b (and c)? YOU CAN'T DO THIS TO AN ASTRONOMY NERD! But they were gone and never came back, except for epsilon Eridani, thank heaven.

I am doing some deep research lately to find out how many exoplanets (once called astrometric binaries, unseen companions, planetars, variable proper motion stars, and similar names) were once believed to have existed, and to locate those astronomy papers "proving" those planets existed (or did not exist). Attached is my little cheat sheet so far. I've saved many papers I found online and will soon give links to them and much more information.

A few odd things: Many of these last-century exoplanet papers have Dr. P. van de Kamp's name (vdK) attached to them, not just ones about Barnard's Star. Also, many of the writers were using the same altered telescope as vdK, or worked in association with him at Sproul Observatory, or were even related to him. (Reuyl is one.) Very strange stuff. And VB8b's "discovery" about 1985 served to expand the study of brown dwarfs.

Also, 70 Ophiuchi was thought to have had planets back in the 1700s and 1800s. I was amazed.

Take a look at the JPG pic of my Excel database (greatly in need of expansion) and toss in your thoughts. Anyone else remember 70 Ophiuchi having planets besides myself? :)

Roger E. Moore
2017-Jan-07, 01:15 AM
[let's try this one more time]


In 1867, the star Vega was a triple star. At least, some people said it was. Curious reports of Vega having one or more "companions" ran up to 1897, so far as I can tell.

Here are the two pages of the magazine. The link I had does not work here for some reason.

Roger E. Moore
2017-Jan-07, 01:28 AM
More companions of Vega from 1897. Unseen planets and bizarre multiple stars, oh my.

Roger E. Moore
2017-Jan-07, 04:48 AM
Another update of my chart showing disputed exoplanets. I cut off the chart at 1995, just as real exoplanets were starting to be found. More updates coming. Enjoy.

swampyankee
2017-Jan-07, 03:38 PM
Searching for extra-terrestrial planets was, if I remember, motivated by competing theories of planetary formation, one of which relied on low-probability events (near collisions), and one which predicted planets as a side effect of stellar formation. The latter, the nebular hypothesis, was, I believe, more popular, but with a sample size of one, the former remained a mainstream, but minority, position.

Finding extra-solar planets would be evidence supporting the nebular hypothesis, which was why people were looking. In retrospect, I suspect that the technology of the time was insufficient.

Roger E. Moore
2017-Jan-11, 01:41 AM
This table rounds out my look into this topic for the moment. Too much else to get into. There were a LOT more false positives than I had thought, half again as many as I had recalled. I will contribute to this thread when I can find more oddball information on the topic.

The JPG table shows the most detailed examples of every major claim for exoplanet discovery (or "unseen companions) at least), up to the most recent one, which I could not ignore: alpha Centauri B b. Boy, I hated for that to go flat. I do notice in some papers that people are still looking for that one, hoping it will show up again.

This would make good fodder for an alternate-universe novel in which the false claims were the ones that proved true, sort of like a latter-day Mesklin series by Hal Clement.

If nothing else, it warns us to be careful.

ngc3314
2017-Jan-11, 03:55 AM
There was such a long history of reports that did not pan out in the early 1980s (incorrect evidence for disks, minute astrometric shifts) that the sample file for LaTeX reports at Kitt Peak used the fill title "Yet Another Solar System" and the author address of a nearby institution which had produced a number of those.

publiusr
2017-Jan-13, 08:23 PM
I seem to remember a recent documentary--where a 3D computer graph was turning--and there was something listed 2 light years out. I can't even remember the program.

Roger E. Moore
2017-Jan-14, 03:54 AM
2 LY.... got me.

lpetrich
2017-Jan-14, 04:09 AM
As I understand it, the largest observed effects on Barnard's Star were when PVdK's telescope went through some maintenance.

Also, it would be interesting to track down the data and try present-day orbit-determination software on them. Even amateur orbit-determination software should suffice, given how fast desktop computers now are. One can even use some random starting point by using a solution technique like simulated annealing. There are a variety of algorithms for doing nonlinear optimization, and I will discuss them if anyone is interested.

Hornblower
2017-Jan-14, 04:17 AM
As I understand it, the largest observed effects on Barnard's Star were when PVdK's telescope went through some maintenance.

Also, it would be interesting to track down the data and try present-day orbit-determination software on them. Even amateur orbit-determination software should suffice, given how fast desktop computers now are. One can even use some random starting point by using a solution technique like simulated annealing. There are a variety of algorithms for doing nonlinear optimization, and I will discuss them if anyone is interested.My bold. It is my understanding that the objective was disassembled and then reassembled in a new cell, and its imaging characteristics were changed in a way that was difficult to reconcile with the old plates. Perhaps the spacing of the lenses was changed a bit. I think that episode made astronomers reluctant to disassemble the objectives of other large refractors for any reason.

Roger E. Moore
2017-Jan-18, 12:52 AM
Fixed some errors, added new info.

OMG, did I say "disputer"? OMG OMG OMG

publiusr
2017-Jan-20, 09:38 PM
The entire history of Bernard's star planet was discussed in the book Looking for Earths by Alan Boss, it also discusses a lot of theory and history of looking for planets upto 1998. Bernards Stars planet planet go dismissed because they telescope used to take the measurements had a couple of faults that led to Van de Kamp to thinking there was at first one planet, then 2 and 3 planets around the star. That is the nature of science.

Did anyone ever think Barnards star was a planet or second sun of our system?

Roger E. Moore
2017-Jan-21, 12:38 AM
Did anyone ever think Barnards star was a planet or second sun of our system?

Um, no. Too far away. Alpha Centauri is closer.

The Samoan Dicer
2018-Aug-17, 09:04 PM
Roger I have wondered about this too. There is a conspiracy going on with Astronomy. Actually a lot of this gets into the realm of the haves and have nots. They know that most of us can't afford to buy and own good telescopes and that we do not have clearance to go to Observatories, like professor or faculty clearance of like a University. So they are a feeding us bull. Stars like Trappist 1 that is only like 10 percent the size of the sun and forty light years away. Or this Kepler 452B. They actually published some article in the dummy news (that's what I call all news) about this. An earth-like planet potentially around Kepler 452B. And guess what that star is only 1400 light years away. What is this? What is going on. We have no hope of sending a human or a probe to any star that is hundreds of light years away. So why even mention it? It's bull news. But that is astronomy. And that is how Astronomy is getting their funds and grants.

Yeah and in the meantime stars that are close to Earth like Barnard's or Tau Ceti. They are redacting the finds of potential planets around those stars. That scientists published in the 1940 and the 1950s and the 1960s. And scientists back in the 1940s and the 1950s were a heck of a lot sharper than the so called scientists today. Scientists today don't even know how to name a crater or a mountain. And they are all into demoting. The are clowns. You are right they CAN'T DO THIS, but they are doing it. It is a conspiracy. Any star that we humans could conceivably go to in perhaps the not too far future, and perhaps even in the immediate reality these scientists and astronomers are now saying don't bother. Because there is nothing there. How do they seriously know that? Have these clowns been to these stars? What you have to understand Roger is that these clowns don't care if the subject is more complicated than you thought. Because they are trying to shut it down. And totally make it the realm of the haves and the have nots. You want to use our Observatory and do some parallax observing and wobble and shadows . Then you have to bend over and do what we say and do this to accept the research and funding grants. Look at this other one, Wasp12 B, orbiting a star 1400 light years away. What kind of crack are these people on? They are calling it the Asphalt planet or the pitch dark planet. Asphalt is a good word to describe where most Astronomers and scientists today faces are stuck on.

The Backroad Astronomer
2018-Aug-18, 12:47 AM
Roger I have wondered about this too. There is a conspiracy going on with Astronomy. Actually a lot of this gets into the realm of the haves and have nots. They know that most of us can't afford to buy and own good telescopes and that we do not have clearance to go to Observatories, like professor or faculty clearance of like a University. So they are a feeding us bull. Stars like Trappist 1 that is only like 10 percent the size of the sun and forty light years away. Or this Kepler 452B. They actually published some article in the dummy news (that's what I call all news) about this. An earth-like planet potentially around Kepler 452B. And guess what that star is only 1400 light years away. What is this? What is going on. We have no hope of sending a human or a probe to any star that is hundreds of light years away. So why even mention it? It's bull news. But that is astronomy. And that is how Astronomy is getting their funds and grants.

Yeah and in the meantime stars that are close to Earth like Barnard's or Tau Ceti. They are redacting the finds of potential planets around those stars. That scientists published in the 1940 and the 1950s and the 1960s. And scientists back in the 1940s and the 1950s were a heck of a lot sharper than the so called scientists today. Scientists today don't even know how to name a crater or a mountain. And they are all into demoting. The are clowns. You are right they CAN'T DO THIS, but they are doing it. It is a conspiracy. Any star that we humans could conceivably go to in perhaps the not too far future, and perhaps even in the immediate reality these scientists and astronomers are now saying don't bother. Because there is nothing there. How do they seriously know that? Have these clowns been to these stars? What you have to understand Roger is that these clowns don't care if the subject is more complicated than you thought. Because they are trying to shut it down. And totally make it the realm of the haves and the have nots. You want to use our Observatory and do some parallax observing and wobble and shadows . Then you have to bend over and do what we say and do this to accept the research and funding grants. Look at this other one, Wasp12 B, orbiting a star 1400 light years away. What kind of crack are these people on? They are calling it the Asphalt planet or the pitch dark planet. Asphalt is a good word to describe where most Astronomers and scientists today faces are stuck on.
Speaking as a person who "had clearance" to a couple of scopes mostly used for teaching is you really don't have to have clearance to see them. A lot of them actually they do have tours for the general public to go and see things thru them. Of course it is handled by a staff member who has training in how to use the scope. Some of these scopes can ran from something from a hundred thousand to a million for smaller ones to billions for larger ones. There this plenty of science that amateur astronomers do because space is such a large place and there are only so many professionals and scopes. About 10 years a 8 year old found a super nova in a galaxy. The first super nova found in Canada was found by a group of amateurs, actually one of them helped the 8 year old girl. (I knew him years ago.) There is some specialize training you have to do analyze the images for some objects. You can not just look at an object and say there is a planet. First you have to use a program like IRAF (there are probably other suites more modern and more specialized ). These programs allow to detect how bright a star is and how the brightness changes over time. Then you have to do some statistical analyzes to make sure that is a planet orbiting a star. If you can can get good resolution of the star you can do this for stars for real distance off. You can do this if you take the time to learn the software and math. Their have been studies that have taken a few planets of the list of planets we know for sure because they are not sure they are planets or errors in the observations or analyses. If a scientists is not sure to a certain magnitude they will retract the conclusion until more data comes in. The reason why some scientist don't know every crater is that most of them are highly specialized into their specialization, it is like asking a zoologists what kind of orchid you have in your hand. Their are a plenty of resources out there for anyone with a laptop to tap into the information and resources. Most astronomers will be more than helpful if you ask them unless they are some kind of recluse or stuck up.

Swift
2018-Aug-18, 01:46 PM
Roger I have wondered about this too. There is a conspiracy going on with Astronomy. Actually a lot of this gets into the realm of the haves and have nots. They know that most of us can't afford to buy and own good telescopes and that we do not have clearance to go to Observatories, like professor or faculty clearance of like a University. So they are a feeding us bull. Stars like Trappist 1 that is only like 10 percent the size of the sun and forty light years away. Or this Kepler 452B. They actually published some article in the dummy news (that's what I call all news) about this. An earth-like planet potentially around Kepler 452B. And guess what that star is only 1400 light years away. What is this? What is going on. We have no hope of sending a human or a probe to any star that is hundreds of light years away. So why even mention it? It's bull news. But that is astronomy. And that is how Astronomy is getting their funds and grants.

The Samoan Dicer

Because you are new here, I will go a little easier on you. But you need to know this post is not appropriate. A rant against astronomy and scientists is not an appropriate topic for the Astronomy sub-forum and a serious discussion of Barnard's Star.

If you wish to discuss some alleged conspiracy, you can ONLY do that in the Conspiracy Theory sub-forum.

If all you want to do is call astronomers and other scientists bad names, an astronomy and science forum is probably not a good place for it. You might consider taking these rants elsewhere.

If you are not familiar with our rules (link in my signature) I suggest you review them.

Swift
2018-Aug-18, 08:13 PM
Further CT posts from The Samoan Dicer have been moved to this thread (https://forum.cosmoquest.org/showthread.php?169596-The-Samoan-Dicer-s-Conspiracy-Ideas&p=2457907#post2457907).

Roger E. Moore
2018-Aug-19, 10:55 PM
if I had to pick a nonexistent exoplanet as the one I regret being nonexistent the most, I'd have to go with.... 61 Cygni C. That one really bummed me out. Mesklin, where are you?

Roger E. Moore
2018-Oct-25, 03:51 PM
Went back to this topic, decided to do some research on various suspected/disproven planets and companions. Found some entertaining things. Hope you enjoy.

===============

Is Sirius a triple star? We know it's a double, but the triple-star idea was a controversy that would not die until the 21st century, enjoying a over a century of intellectual distraction.

Here's one early paper on a third component. People have wondered about "Sirius C" since before the start of the 20th century, after Bessel discovered Sirius was a double star; topic keeps cropping up. This one is in French (can't fully translate, sorry), appears to discuss third body in Sirius system. 2 pages, scanned PDF


http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1929GazA...16...47D&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf

Sirius C

Dermul, Am. (Gazette Astronomique, vol. 16, pp. 47-48) 08/1929

===============================

Short bit, a meeting note in a conference schedule, concerning a suspected x-ray source in Sirius system from 1979. 1 page, left column near top


http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1979BAAS...11..465B&data_type=PDF_H IGH&whole_paper=YES&type=PRINTER&filetype=.pdf

Is "Sirius C" the X-ray Source?

Böhm-Vitense, E. (Bulletin of the American Astronomical Society, Vol. 11, p. 465) 03/1979

===============================

The paper that ignited the most recent campaign to search for a third component to the Sirius AB system, this time a brown dwarf and not a tiny star. This paper has many older references of value to anyone wishing to dive into this topic further. A good read.


http://adsabs.harvard.edu/abs/1995A%26A...299..621B (abstract)
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1995A%26A...299..621B&data_type=PDF _HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf (PDF scan of actual paper, short)

Is Sirius a triple star?

Benest, D.; Duvent, J. L. (Astronomy and Astrophysics, v.299, p. 621) 07/1995

ABS: Sirius has been discovered as double more than 130 years ago. From the beginning of our century up to now, observational as well as physical and dynamical indications lead to the hypothesis of the existence of a third body in the system. In this paper, we present recent orbital analysis of the binary Sirius A-B which, helped by numerical simulation of triple systems, strengthens the idea for the triplicity of Sirius: a tiny star could revolve in about 6 years around Sirius A. Finally, we discuss the possibility of direct detection for this suspected Sirius C.

===============================

The paper that buried Sirius C for good... almost (see last quotes). 6 pages, diagrams.


https://arxiv.org/abs/1104.1427

Piercing the Glare: Direct Imaging Search for Planets in the Sirius System

Christian Thalmann et al. (Submitted on 7 Apr 2011)

ABS: Astrometric monitoring of the Sirius binary system over the past century has yielded several predictions for an unseen third system component, the most recent one suggesting a 50 MJup object in a ~6.3-year orbit around Sirius A. Here we present two epochs of high-contrast imaging observations performed with Subaru IRCS and AO188 in the 4.05 \mum narrow-band Br alpha filter. These data surpass previous observations by an order of magnitude in detectable companion mass, allowing us to probe the relevant separation range down to the planetary mass regime (6-12 M_Jup at 1", 2-4 M_Jup at 2", and 1.6 M_Jup beyond 4"). We complement these data with one epoch of M-band observations from MMT/AO Clio, which reach comparable performance. No dataset reveals any companion candidates above the 5-sigma level, allowing us to refute the existence of Sirius C as suggested by the previous astrometric analysis. Furthermore, our Br alpha photometry of Sirius B confirms the lack of an infrared excess beyond the white dwarf's blackbody spectrum.

QUOTES: One and a half centuries ago, Sirius was found to host a faint binary companion (Bond 1862). The orbital motion of this pair has been monitored ever since, leading to a number of publications that claimed to find periodic perturbations indicative of the presence of an unseen third system component, Sirius C. The most recent analysis predicted a substellar companion in a ~6.3-year circumstellar orbit around Sirius A (Benest & Duvent 1995, and references therein). While the amplitude of the purported astrometric signal, 56mas, would suggest a companion mass of 72 MJup, these authors imposed an upper limit of .50 MJup on the basis of system stability considerations. Since no measure of confidence is given, we assume a conservative lower limit of half the measured amplitude, 28mas, on the basis of their plotted periodograms, resulting in a minimal mass of 36 MJup. This would place Sirius C in the so-called brown dwarf desert, the range of orbital parameter space around stars in which brown dwarfs are found to be scarce (e.g. Marcy & Butler 2000; Grether & Lineweaver 2006).

Sirius A is an A1V-type star at a distance of 2.64 pc, a mass of 2.02 M⊙ and an age of 225–250 Myr, whereas Sirius B is a white dwarf of 0.98 M⊙ with a cooling age of 124 ± 10 Myr orbiting Sirius A with a 50-year period (e.g. Liebert et al. 2005). The combination of youth and extreme proximity (cf. a median target distance of 22 pc in the Gemini Deep planet survey, Lafreni`ere et al. 2007b) allow us to explore unusually small orbital radii, with planetary-mass detection limits down to separations of 2.5 AU in projection.

Our high sensitivity to substellar companions around Sirius A allows the first thorough test of the hypothesis of a .50 MJup body, “Sirius C”, in a 6.3-year orbit around Sirius A as proposed by Benest & Duvent (1995). As these authors point out, though, a single negative detection does not prove the non-existence of such an object. Even though the semimajor axis of such an orbit is a = 4.3 AU, corresponding to 1.′′6 at the distance of 2.64 pc, both projection effects and eccentricity can leave the companion at an apparent separation below the inner working angle of 0.′′7 at the time of observation.

We find that coplanar companions down to 6 MJup can be excluded at the 5 level at 100% completeness. The completeness remains above 50% down to 2–3.5 MJup, depending on eccentricity. If no constraints are imposed on the inclination, edge-on orbits emerge that can hide Sirius C behind Sirius A’s glare. As a result, the completeness values for masses above 12 MJup drop to 97–99%for certain eccentricity ranges, and down to 90% for masses of 5–7 MJup. The astrometric signal reported by Benest & Duvent (1995), 56mas, implies a companion mass of 72 MJup. The authors furthermore impose an upper mass limit of .50 MJup on the basis of system stability considerations. While no lower mass limit is given, we derive a conservative estimate of half that value, 36 MJup, from their published periodograms. Given our much lower detection limits, our three combined epochs of high-contrast imaging can therefore decisively reject their Sirius C hypothesis.

One thing to keep in mind is the fact that Sirius B was originally a ~5 M⊙ progenitor star that expanded into a supergiant ~125 Myr ago, with potentially dramatic consequences for the system architecture (Liebert et al. 2005). Accretion of ejected material from Sirius B may have caused planets around Sirius A to gain mass and heat, migrate, or form in the first place as second-generation planets (e.g. Perets 2010). Since these processes would leave the planets hotter and brighter than their unperturbed 250 Myr-old counterparts, our detectable planet mass curves in Figure 3 are conservative for such objects.

However, we note that our observations leave open the possibility for Jupiter- and Neptune-sized planets around Sirius A, especially at short angular separations.

[[emphasis mine -- REM]]

Roger E. Moore
2018-Oct-25, 07:31 PM
A few things I've noticed about the "Sirius C" issue, which also apply to many other claimed/refuted exoplanet detections.

1. It's almost always more than one astronomer who thinks an "unseen companion" is there. Sometimes it's whole teams, different ones, battling it out over long periods of time, either advocating for or refuting the existence of the companion. In a few cases, the same astronomer might advocate against, then later for the existence of a companion (George Gatewood and Lalande 21185 b).

2. The issue is almost never resolved with one paper. Often the issue of a companion's existence is "resolved" then reopened and argued in later papers. Wiggle-room is often left whether confirming or denying a world. Many people hedge their bets, apparently not wishing to be proven wrong.

3. Disputes can literally stretch over centuries (e.g., 70 Ophiuchi C).

4. It's almost never a single source of information in long-term disputes; astrometry might be supplemented by other methods of determining if a companion exists, such as the detection of an x-ray source for "Sirius C".

5. Even disproven claims of unseen companions might provide unexpected benefits (van Biesbroeck 8 b and the surge of interest in brown-dwarf astronomy).