# Talk:55 Cancri

I can't find any source saying this is a binary star. The images at the lower end of the page show some planets circling one star, but the box on the right and the introduction say it's a binary star. What is it? \/ Thank you. Philip1201 (talk) 15:00, 16 November 2008 (UTC)

I'm not entirely sure how you could fail to find such a reference when several are present in the article. Check out references 4 (Marcy et al. 2002), 8 (Eggenberger et al. 2003), 9 (Raghavan et al. 2006), 16 (Fischer et al. 2008) the external link to SolStation and the one to a site on the Illinois University website.  Icalanise (talk) 14:29, 16 November 2008 (UTC)

Pronunciation of the name 55 Cancri needs to be added to the article. Is the second 'c' hard or soft? Non-scientists like myself want to know. 
128.138.108.183 21:55, 6 November 2007 (UTC)
in Latin it would be hard,regardless of how you pronounced it in the nominative Cancer.  In English it is hard. 'kankri' Richardson mcphillips1 00:27, 8 November 2007 (UTC)

I'll add a link to the pronunciations of the constellations & their genitive forms to the template at the bottom of these pages. kwami 01:24, 8 November 2007 (UTC)
Too many potential templates to modify. I suggested it at the project page. kwami 01:34, 8 November 2007 (UTC)
In English, "c" followed by "r" is always hard. Zaslav 06:56, 8 November 2007 (UTC)

I created the image 55Cancri System.jpg (in paint) I took some images from exoplanet.org and I change the color, order, size etc and finally I put all together, so basically I created, about the Nasa Images I know that those are free for use but I oould not find the category 1981willy 10:08, 6 June 2007 (UTC)

You can't take images from exoplanet - they own a copyright on the images which forbids this.  For nasa images, generically {{PD-USGov-NASA}} is an appropriate tag - you should include the URL where you obtained the image, as well as anything else that's pertinant (see how I've redone the NASA images you've uploaded - although I also grabbed higher res versions).  WilyD 13:17, 6 June 2007 (UTC)

We really need a better comparison image - the scale of the system is all wrong - there is a huge gap between planets c and d, whereas in the picture the planets look equally-spaced. Chaos syndrome 13:27, 30 June 2006 (UTC)
The statements "The system contains a yellow dwarf star (55 Cancri A) similar to our Sun and a red dwarf (55 Cancri B). The two components are separated by over 1000 times the distance from the Earth to the Sun." do not agree with the comparison image further down the page. I.e. 55 CnC B is shown well inside earth's orbit as opposed to 1000 times outside it.

Mu Arae has also got 4 planets now, so this is wrong:
"The 55 Cancri system is the first and so far only known extrasolar planetary system with four planets."
Look here: Mu_Arae —The preceding unsigned comment was added by 217.149.119.121 (talk • contribs).

Well 55 Cancri has three confirmed planets with one possible or challenged innermost planet; to prove if it does really exist, or if it was just an error. Also 55 Cancri is no longer the "only" star with 4 planets, but was the "first star" with 4 planets discovered. But Mu Arae has four confirmed planets and with Mu Arae e as a possible exteressial life planet, similar to Earth which could be very, very interesting. --§ Alastor "Mad-Eye" Moody (talk + contribs + userboxes) 03:42, 9 September 2006 (UTC)

Wait, the article says that the gap between c & d contains the habitable zone.  But 55 Cancri's luminosity is noticeably less than Sol's.  Wouldn't that put the habitable zone somewhere around or even inside the orbit of b?  -Tau 68.237.83.47 00:50, 29 September 2006 (UTC)
Oops, nevermind.  Misplaced the decimal.  -Tau 68.237.83.47 00:51, 29 September 2006 (UTC)

Looks like all the planets of 55 Cnc have relatively circular orbits. Individual planet pages should be updated.--— JyriL talk 23:33, 6 November 2007 (UTC)

I've updated the orbit diagram on Wikimedia Commons. Chaos syndrome 00:32, 7 November 2007 (UTC)

As mentioned before, this article still says 55 Cancri is the only known system with four planets.  Also, 55 Cancri now has five planets.

http://www.guardian.co.uk/science/2007/nov/07/spaceexploration
http://www.sciam.com/article.cfm?articleID=16EEA019-E7F2-99DF-313BF41351A7B653&chanID=sa003
http://news.nationalgeographic.com/news/2007/11/071106-record-planet.html

I read this in the Daily Mail and wondered if this is new info. As i'm not really into science maybe one of you guys could field this one! See this article for me to see if i'm right, thanks! And please get back to me. From Pafcool2 20:21, 7 November 2007 (UTC)
Not that I'd really rely on anything Daily Mail says, they are not most reliable newspapers ;) Mic of orion (talk) 14:09, 11 January 2008 (UTC)

Yes, a large moon orbiting the 4th planet could be habitable for life as we know it. Normally you'd expect a moon around a gas giant to be constantly bombarded with asteroids drawn in by the giant, which would be problematic for life, but in 55 Cancri there's an even larger giant further out that might help deflect them. And with the abundance of heavy elements in the system, there's a good chance a large terrestrial body would still be warm enough to keep plate tectonics going, which is needed to recycle water and air. One caveat, though: the moon would have to be huge, earth-sized, to retain a thick atmosphere. Titan has a thick atmosphere only because it's so cold; it would lose it if it were as warm as Earth. Our giants don't have any moons that large relative to the planet. And to be habitable, the moon would need to be outside the giant's radiation belts.  —Preceding unsigned comment added by Kwamikagami (talk • contribs) 20:35, 7 November 2007 (UTC)

For planet to support life it must be in habitable zone, not knowing this is the case... 
Also if moon is of similar size of Earth it will need to be a fair distance from the gas giant, 1 million KM +, as such moon would exert massive gravitational pull on the gas giant, radiation could also be an issue if moon is any closer, we do not want to see IO effect on such potential planet. But in retrospect it would be nice to see worlds that could potentially be human considerd colonies way in the future. Mic of orion (talk) 14:09, 11 January 2008 (UTC)

In principle, it might be possible for an Earth-like Trojan planet to share 55 Cancri f's orbit, as well. Nik42 (talk) 16:24, 10 June 2008 (UTC)
It already says that in the article. However, it couldn't be very massive. I don't know if an Earth-mass trojan would be stable. (I added a request to have the mass limit added to the trojan article.) — kwami (talk) 16:47, 10 June 2008 (UTC)
I inserted an Earth-mass planet in f's leading trojan point in an orbit simulator, and ran it for 2,000 simulated years, and found no instability in that period (I also placed c and d in the simulation; I ignored the innermost two because they're so close to the central star).  So, the trojan points seem to be perfectly suitable.  It'd be an interesting situation.  From the perspective of someon on this theoretical planet, f would appear to be stationary relative to the sun, or at most, rotating around a fixed point ... I imagine any native culture's early astronomers would believe it to be different from the other planets, since it would move through the sky in sync with the sun.  In theory there could be an Earth-sized planet in *both* Trojan points. Nik42 (talk) 03:35, 11 June 2008 (UTC)
It would be like the Moon, but with a fixed phase, so wouldn't be a "planet" at all (except for the conception that makes the Sun and Moon "planets").
Good to know. I know it's thought that Theia may have collided with Earth after its mass grew to the point that its trojan orbit became unstable. But if that's Mars-massed for Earth, I suppose it would have to be much more than Earth mass for Cancri f. kwami (talk) 07:56, 11 June 2008 (UTC)
Yeah, but you'd need a telescope to view its phase, I believe.  Another potential problem would be that the trojan points tend to attract asteroids, so I imagine any planet located there would tend to suffer an exceptionally large number of asteroid collisions. Nik42 (talk) 04:45, 12 June 2008 (UTC)
I wonder. They'd have to be traveling relatively slowly, and once a large body formed, it would probably sweep them all up. My worry would be that a large body like f would sling asteroids out of the inner system, hitting the trojan. But if gas giants have migrated in as far as a and b, there might not be much material like that left. kwami (talk) 06:38, 12 June 2008 (UTC)

The article has a data box on the star.  For instance, luminosity is 0.61 / 0.0076 L☉.  What does this mean?  I know that L☉ means the luminosity of the sun (and it's linked to the article).  But what are the two numbers?  The same question applies to mass, etc.  There need to be explanations provided for those not in the know (and they should be where they can be accessed easily from all star articles).  I'm not in the know so I can't do it.  Please help! Zaslav 07:02, 8 November 2007 (UTC)

The first number is for 55 Cancri A, the second number is for 55 Cancri B (the red dwarf star, not the planet). The table does indicate that it is giving data for two stars, but I guess if you want it spelled out a bit more explicitly we could do something like what has been done for 40 Eridani and have a huge table. Chaos syndrome 23:21, 8 November 2007 (UTC)
Thanks for your helpful reply.  It looks like someone (you?) has done a bigger box already -- I like it.  I looked at 40 Eridani's box for comparison, and it is rather large, but very easy to read.  I also looked at Sirius.  Its infobox is organized more like the 1-column previous one for 55 Cancri, but with parenthetical (A) and (B) to identify the two stars.  That is, the data appears as xxx (A) / xxx (B).
My opinions:  It's true that once one knows what to look for, the data is comprehensible in any format, but less so if one is inexperienced.  The multicolumn format as at 40 Eridani (and now at 55 Cancri) is much the easiest to read.  The 1-column format is harder to read, but with the (A) and (B) it's somewhat easier to understand than without.  Zaslav 01:27, 9 November 2007 (UTC)

Looks like the parameters in the infobox have been updated to include citations (which is good). Unfortunately the text has not been, so we've now got conflicting estimates for quantities such as age and metallicity in the text and the infobox. If you're going to change the infobox, please make sure the article is still self-consistent (and vice-versa)! Chaos syndrome 00:02, 9 November 2007 (UTC)

To be blunt, your new layout looks absolutely hideous on my browser. It pushes all of the lead text down past the end of the table. I don't find this to be an acceptible solution. Also this is a page in work. Rather than complaining about a page in an intermittent stage, why don't you fix the issues yourself? It's been less than one day since the references have been added into the infobox. Good grief. Anyway, I find myself suddenly disinterested in putting in more work on this page. Bye. — RJH (talk) 19:00, 9 November 2007 (UTC)
If you have issues with it, why don't you fix it yourself? It's been less than one day since it was added into the infobox. Good grief. Now I remember why I keep leaving the Wikipedia for extended periods. Bye Chaos syndrome 00:24, 10 November 2007 (UTC)

From the intro:
"The 55 Cancri system   was  is  currently the only planetary system known to have five planets"
WAS or IS ?
the reference doesn't load in my browser.  —Preceding unsigned comment added by 207.237.232.74 (talk) 09:51, 30 July 2008 (UTC) 

According to an HST Search it looks like there are images of 55 Cancri taken by Hubble (which would be in the public domain). I don't have an account on their data retrieval system, but it seems like someone should make an effort to retrieve at least one actual image of the star system. Kaldari (talk) 23:12, 21 October 2008 (UTC)

As part of the WikiProject Good Articles, we're doing sweeps to go over all of the current GAs and see if they still meet the GA criteria. I'm specifically going over all of the "Planets and Moons" articles. I believe the article currently meets the criteria and should remain listed as a Good article. I have made several minor corrections throughout the article. Altogether the article is well-written and is still in great shape after its passing in 2006. Continue to improve the article making sure all new information is properly sourced and neutral. I would recommend going through all of the citations and updating the access dates and fixing any dead links. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. I have updated the article history to reflect this review. Happy editing! --Nehrams2020 (talk) 01:19, 3 March 2009 (UTC)

Is "yellow dwarf" a correct term for 55 Cancri A? Shouldn't it be "main sequence star"? Even as a layman, I've seldom encountered the former term.  —Preceding unsigned comment added by 193.105.85.4 (talk) 07:05, 4 May 2011 (UTC) 

Wasn't there a planet in this system found to have diamonds in it's crust or something?  — Preceding unsigned comment added by 72.67.17.49 (talk) 23:55, 16 November 2012 (UTC) 

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hi, 
I wanted to point out that the image at the right side, that displays the location of the star 55 Cancri in a small star-map is misleading. 
The legend says : "Location of 55 Cancri (circled)" but in that image there are more circles, as the one around M44. When the user clicks on the image, the svg image displayed in the navigator does not show the red circle that surrounds 55 Cancri.  158.169.150.18 (talk) 14:21, 7 June 2021 (UTC)

Unfortunately the image is just a map and the circle only displays in this article and on the thumbnail.  I have changed the caption to make it clearer which circle identifies this star.  Lithopsian (talk) 19:40, 7 June 2021 (UTC)

The redirect 55 Cancri i has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 October 2 § 55 Cancri i until a consensus is reached.  Edward-Woodrow • talk 19:58, 2 October 2023 (UTC)

the recently published paper on 55 Cnc A and B which refined the parameters of A's planets and discovered two around B has an issue in its summary, specifically in 55 Cnc A's section, with the summary acting as if it is definitive that Ag isn't correlated to stellar activity; the authors themselves are unsure of it's nature, and the possibility that it may be planetary is only proposed as a suggestion by them, they even say consensus on it (and 'these giant planets') may change. They never even directly state it does not appear to be correlated with 55 Cnc A's magnetic cycle.
with how it is currently worded it implies Ag is more likely to exist than Ad, the paper itself is too vague on the matter to draw such a definitive conclusion. 
tl;dr: the wording on Ag's summary should be changed to reflective the uncertainty of the authors, and as it is right now it doesn't leave it as up to interpretation as the authors did, and there are never even any direct statements that Ag isn't correlated; its 50/50. Ewsas Wjack (talk) 15:01, 20 October 2025 (UTC)

The paper states that There are indications that the RV signal at this period is less in phase with the S index over the last decade, and also that the amplitude of this signal may be too large to be attributed to the magnetic activity. In addition, the amplitude is not chromatic and the star is extremely quiet. in the conclusion, and At this point, the absence of chromaticity, the unmatching periods and the larger than-expected amplitude question the interpretation of the 3830-d signal as being due to the magnetic cycle only, rather than mostly due to another outer planet in the system. in section 5, supporting the claim that the signal does not appear to be correlated with stellar activity. Also, they mention the possibility of both the planet and the cycle being responsible for this periodicity, which could be addressed in this article (although i could not find a good wording...) 21 Andromedae (talk) 18:36, 22 October 2025 (UTC)
The authors choose their wording carefully when describing it: "there are indications", "may be too large", and they treat the idea that Ag might be a planet as opposed to a part of the magnetic cycle as a possibility rather than something they're entirely confident in. The state of the outer 55 Cancri A system is a mess, so definitive statements like "it does not appear to be correlated with the stellar activity cycle" don't do it justice. If another independent analysis is done on 55 Cancri A's outer system that gives further strength to the ~3800 d solution for Ag, then sure the wording can become more confident, but right now it should remain impartial and not opinionated. Also you're right that could do with being addressed in the article. Ewsas Wjack (talk) 15:13, 29 October 2025 (UTC)
What about "At this point, the absence of chromaticity, the unmatching periods and the larger than-expected amplitude question the interpretation of the 3830-d signal as being due to the magnetic cycle only, rather than mostly due to another outer planet in the system" and "In addition, the amplitude is not chromatic and the star is extremely quiet"? Doesn't this suggest that the variation does not appear to be correlated with the stellar activity cycle, as previously (and i my opinion, perfectly) summed up in the article? Furthermore, the paper's abstract does say that they "propose the existence of a sixth planet candidate, whose period falls close to that of the magnetic cycle, or half of it", hardly in agreement with the assertion that the signal may or may not be correlated with the stellar activity cycle. 21 Andromedae (talk) 15:49, 29 October 2025 (UTC)