An Abhainn

Tá **an Abhainn** (**Eridanus** as Laidin) ar an séú réaltbhuíon is mó de na 88 réaltbhuíon a nglacann an tAontas Réalteolaíoch Idirnáisiúnta leo. Bhí sé freisin ar cheann de na 48 réaltbhuíon ar chatalóg Tholamaes. Tá an réaltbhuíon seo suite ar an leathsféar neamhaí theas.

## Príomhghnéithe
* α Eri, dá ngairtear freisin Achernar: tá sé ar amharcmhéid 0.50 agus is é B3&nbsp;Vpe a aicme speictreach. Is réalta an-aisteach é Achernar: tá sé ar cheann de na réaltaí is leacaithe sa spéir. Is cosúil go bhfuil trastomhas a mheánchiorcail 50% níos mó ná a thrastomhas polach. Is é is cúis leis seo ná go bhfuil Achernar ag casadh go han-tapaidh. 

* β Eri (Cursa): A3&nbsp;III a aicme speictreach agus soilsíonn sé le gile dhealraitheach ar méid 2.79v.

* γ Eri (Zaurak): den aicme speictreach M1&nbsp;IIIb, agus ar amharcmhéid 2.98v. Is réalta athraitheach é Zaurak, agus réalta dhúbailte optúil chomh maith.

* ε Eri: Tá an réalta athraitheach seo ar an tríú réalta is cóngaraí don Ghrian; níl sé ach 10.5 solasbhliain i bhfad uainn. K2&nbsp;V a aicme speictreach agus 3.78v a amharcmhéid. Is réalta athraitheach BY Draconis é, agus is cosúil go bhfuil pláinéad eachtarghréine in aice leis.

* θ Eri (Acamar): is A-réalta bán an réalta dhúbailte seo ar amharcmhéid 3.4, in éineacht le A-réalta eile atá ar méid 4.5; 2.9 an amharcmhéid chomhtháite. Is furasta an péire optúil seo a scoilteadh le teileascóip bheaga. Ar chatalóg Tholamaes, is réalta den chéad mhéid í seo!

* ο<sup>2</sup> Eri (Keid): is tríréalta shuntasach é seo. Tá an príomhréalta ar méid 4.43 agus ar aicme speictreach G9. Is abhac bán é an dara comhbhaill, ar méid 9.52, agus is bladhmréalta an tríú comhbhaill, ar méid 11.17.

* 32 Eri: réalta dhúbailte.

## Réada suntasacha domhainspéire
* NGC 1300: réaltra bíseach barrach

* NGC 1535: réaltnéal pláinéadach, ar méid 9.6, a d'aimsigh Wilhelm Herschel sa bhliain 1785. Tá an lárréalta ar amharcmhéid 12.18; 8.7 an gile dhromchla.

* Grúpa Eridanus: tá a lán réaltraí le feiceáil ar réaltbhuíon na hAbhann. **Grúpa Eridanus**, nó **Fornax II**, a thugtar ar bhraisle réaltraí a chuimsíonn réaltraí ón dá thaobh den teorainn idir an Abhainn agus an Fhoirnéis.

## Miotaseolaíocht
Tá baint speisialta ag an Abhainn le dhá mhiotas na Gréige, agus is dócha go mbaineann an dá cheann acu le cruth na réaltbhuíne seo (.i. slí an-chasta). Uaireanta d'fheictí ar Eridanus mar abhainn a rith as uiscí an Uisceadóra; sa chás seo, caithfidh go samhlaítear an tUisceadóir agus é ag tabhairt a aghaidhe ar an Abhainn, rud nach féidir a dhéanamh gan dealramh an Uisceadóra a athchum i gcaoi go scairdeann an t-uisce amach ar an taobh céanna den Abhainn.

Go coitianta baineann réaltbhuíon na Abhann le miotas Faetón, mac Héilias (.i. na Gréine), a bhain triail as carbad a athar a thiomáint lá amháin, ach ní raibh an méid sin nirt aige na capaill a smachtú, agus sciurd an carbad i ngach treo. Deireadh an scéil ná gur tháinig an carbad ró-ghar don domhan; chlaochlaíodh ranna den domhain go gaineamhlach agus dódh craiceann na daoine a bhí ina gcónaí sna ranna úd (agus is é sin is cúis le craiceann gorm na nAetóipeach, de réir na seanghréagach). Chuir Séas isteach ag an bpointe seo; leag sé Faetón marbh le saighneán, agus thit sé isteach in abhainn Pó san Iodáil.

Ar dtús ionannaíodh an réaltbhuíon leis an slí a bhreac Faetón ar an spéir, ach ina dhiaidh sin chonacthas uirthi mar an abhainn ar thit Faetón isteach inti.

## Réaltaí
:**Réaltaí a bhfuil ainmneacha dílse orthu:**
:* α Eri 0.45 **[[Achernar]]** cawjat[u] an-nahr* = Cam na hAbhann
:* [[Upsilon Eridani|υ Eri]]
:** [[52 Eridani|52/υ¹ Eri]] 4.49 *'Theemin** [''Beemin'']
:** [[52 Eridani|52/υ² Eri]] 3.82 **Beemin** [''Theemin'']
:* [[53 Eridani|53/l Eri]] 3.86 **Sceptrum**, mar ba é seo an réalta is gile ar **Sceptrum Brandenburgicum**, réaltbhuíon caillte.

:**Réaltaí a bhfuil ainmnithe Bayer orthu:**
:: [[Achernar|α Eri]] 0.45; [[Beta Eridani|67/β Eri]] 2.78; [[Gamma Eridani|34/γ Eri]] 2.97; [[Delta Eridani|23/δ Eri]] 3.52; [[Epsilon Eridani|18/ε Eri]] 3.72; [[Zeta Eridani|13/ζ Eri]] 4.80; [[Eta Eridani|3/η Eri]] 3.89; [[Theta1 Eridani|θ<sup>1</sup> Eri]] 3.89; [[Theta2 Eridani|θ<sup>2</sup> Eri]] 4.35; [[Iota Eridani|ι Eri]] 4.11; [[Kappa Eridani|κ&nbsp;Eri]]&nbsp;4.24; [[Lambda Eridani|69/λ&nbsp;Eri]]&nbsp;4.25; [[Mu Eridani|57/μ&nbsp;Eri]]&nbsp;4.01; [[Nu Eridani|48/ν&nbsp;Eri]]&nbsp;3.93; [[Xi Eridani|42/ξ&nbsp;Eri]]&nbsp;5.17; [[38 Eridani|38/ο¹&nbsp;Eri]]&nbsp;4.04; [[40 Eridani|40/ο²&nbsp;Eri]]&nbsp;4.43; [[Pi Eridani|26/π&nbsp;Eri]]&nbsp;4.43; [[Rho1 Eridani|8/ρ<sup>1</sup>&nbsp;Eri]]&nbsp;5.75; [[Rho2 Eridani|9/ρ<sup>2</sup>&nbsp;Eri]]&nbsp;5.32; [[Rho3 Eridani|10/ρ<sup>3</sup>&nbsp;Eri]]&nbsp;5.26; [[Tau1 Eridani|1/τ<sup>1</sup>&nbsp;Eri]]&nbsp;4.47; [[Tau2 Eridani|2/τ<sup>2</sup>&nbsp;Eri]]&nbsp;4.76; [[Tau3 Eridani|11/τ<sup>3</sup>&nbsp;Eri]]&nbsp;4.08; [[Tau4 Eridani|16/τ<sup>4</sup>&nbsp;Eri]]&nbsp;3.70; [[Tau5 Eridani|19/τ<sup>5</sup>&nbsp;Eri]]&nbsp;4.26; [[Tau6 Eridani|27/τ<sup>6</sup>&nbsp;Eri]]&nbsp;4.22; [[Tau7 Eridani|28/τ<sup>7</sup>&nbsp;Eri]]&nbsp;5.24; [[Tau8 Eridani|33/τ<sup>8</sup>&nbsp;Eri]]&nbsp;4.64; [[Tau9 Eridani|36/τ<sup>9</sup>&nbsp;Eri]]&nbsp;4.62; [[50 Eridani|50/υ¹&nbsp;Eri]]&nbsp;4.49; [[52 Eridani|52/υ²&nbsp;Eri]]&nbsp;3.82; [[Upsilon4 Eridani|41/υ<sup>4</sup>&nbsp;Eri]]&nbsp;3.55; [[Phi Eridani|φ&nbsp;Eri]]&nbsp;3.56; [[Chi Eridani|χ&nbsp;Eri]]&nbsp;3.69; [[Psi Eridani|65/ψ&nbsp;Eri]]&nbsp;4.80; [[Omega Eridani|61/ω&nbsp;Eri]]&nbsp;4.36; [[62 Eridani|62/b&nbsp;Eri]]&nbsp;5.50; [[51 Eridani|51/c&nbsp;Eri]]&nbsp;5.22; [[43 Eridani|43/d&nbsp;Eri]]&nbsp;–&nbsp;dúbailte&nbsp;3.97,&nbsp;5.85; [[82 Eridani|82/e&nbsp;Eri]]&nbsp;4.26; [[f Eridani|f&nbsp;Eri]]&nbsp;–&nbsp;dúbailte:&nbsp;4.30,&nbsp;4.73; [[g Eridani|g&nbsp;Eri]]&nbsp;4.17; [[h Eridani|h&nbsp;Eri]]&nbsp;4.59; [[i Eridani|i&nbsp;Eri]]&nbsp;5.11; [[p Eridani|p&nbsp;Eri]]&nbsp;–&nbsp;dúbailte&nbsp;5.76,&nbsp;5.76; [[q1 Eridani|q<sup>1</sup>&nbsp;Eri]]&nbsp;5.52; [[q2 Eridani|q<sup>2</sup>&nbsp;Eri]]&nbsp;5.04; [[17 Eridani|17/v&nbsp;Eri]]&nbsp;4.74; [[32 Eridani|32/w&nbsp;Eri]]&nbsp;–&nbsp;dúbailte:&nbsp;4.79, 6.14; [[y Eridani|y&nbsp;Eri]]&nbsp;4.57

:**Réaltaí a bhfuil ainmnithe Flamsteed orthu:**
:: [[Tau1 Eridani|1/τ<sup>1</sup>&nbsp;Eri]]&nbsp;4.47; [[Tau2 Eridani|2/τ<sup>2</sup>&nbsp;Eri]]&nbsp;4.76; [[Eta Eridani|3/η Eri]] 3.89; [[4 Eridani|4 Eri]] 5.44; [[5 Eridani|5 Eri]] 5.56; [[6 Eridani|6 Eri]] 5.82; [[7 Eridani|7 Eri]] 6.11; [[Rho1 Eridani|8/ρ<sup>1</sup>&nbsp;Eri]]&nbsp;5.75; [[Rho2 Eridani|9/ρ<sup>2</sup>&nbsp;Eri]]&nbsp;5.32; [[Rho3 Eridani|10/ρ<sup>3</sup>&nbsp;Eri]]&nbsp;5.26; [[Tau3 Eridani|11/τ<sup>3</sup>&nbsp;Eri]]&nbsp;4.08; [[Zeta Eridani|13/ζ Eri]] 4.80; [[14 Eridani|14 Eri]] 6.14; [[15 Eridani|15 Eri]] 4.86; [[Tau4 Eridani|16/τ<sup>4</sup>&nbsp;Eri]]&nbsp;3.70; [[17 Eridani|17/v&nbsp;Eri]]&nbsp;4.73; [[Epsilon Eridani|18/ε Eri]] 3.72; [[Tau5 Eridani|19/τ<sup>5</sup>&nbsp;Eri]]&nbsp;4.26; [[20 Eridani|20 Eri]] 5.24; [[21 Eridani|21&nbsp;Eri]]&nbsp;5.97; [[22 Eridani|22 Eri]] 5.53; [[Delta Eridani|23/δ Eri]] 3.52; [[24 Eridani|24 Eri]] 5.24; [[25 Eridani|25 Eri]] 5.56; [[Pi Eridani|26/π&nbsp;Eri]]&nbsp;4.43; [[Tau6 Eridani|27/τ<sup>6</sup>&nbsp;Eri]]&nbsp;4.22; [[Tau7 Eridani|28/τ<sup>7</sup>&nbsp;Eri]]&nbsp;5.24; [[29 Eridani|29&nbsp;Eri]]&nbsp;7.10; [[30 Eridani|30&nbsp;Eri]]&nbsp;5.48; [[32 Eridani|32/w&nbsp;Eri]]&nbsp;–&nbsp;dúbailte:&nbsp;4.79, &nbsp;6.14; [[Tau8 Eridani|33/τ<sup>8</sup>&nbsp;Eri]]&nbsp;4.64; [[Gamma Eridani|34/γ Eri]] 2.97; [[35 Eridani|35&nbsp;Eri]]&nbsp;5.28; [[Tau9 Eridani|36/τ<sup>9</sup>&nbsp;Eri]]&nbsp;4.62; [[37 Eridani|37&nbsp;Eri]]&nbsp;5.44; [[38 Eridani|38/ο¹&nbsp;Eri]]&nbsp;4.04; [[39 Eridani|39/39&nbsp;Eri]]&nbsp;4.87; [[40 Eridani|40/ο²&nbsp;Eri]]&nbsp;4.43; [[Upsilon4 Eridani|41/υ<sup>4</sup>&nbsp;Eri]]&nbsp;3.55; [[Xi Eridani|42/ξ&nbsp;Eri]]&nbsp;5.17; [[43 Eridani|43/d&nbsp;Eri]]&nbsp; 3.96; [[44 Eridani|44&nbsp;Eri]]&nbsp;5.53; [[45 Eridani|45&nbsp;Eri]]&nbsp;4.91; [[46 Eridani|46&nbsp;Eri]]&nbsp;5.71; [[47 Eridani|47&nbsp;Eri]]&nbsp;5.20; [[Nu Eridani|48/ν&nbsp;Eri]]&nbsp;3.93; [[49 Eridani|49&nbsp;Eri]]&nbsp;5.32; [[50 Eridani|50/υ¹&nbsp;Eri]]&nbsp;4.49; [[51 Eridani|51/c&nbsp;Eri]]&nbsp;5.23; [[52 Eridani|52/υ²&nbsp;Eri]]&nbsp;3.82; [[53 Eridani|53/l Eri]] 3.86; [[54 Eridani|54&nbsp;Eri]]&nbsp;4.32; [[55 Eridani|55&nbsp;Eri]]&nbsp;5.98; [[56 Eridani|56&nbsp;Eri]]&nbsp;5.78; [[Mu Eridani|57/μ&nbsp;Eri]]&nbsp;4.01; [[58 Eridani|58&nbsp;Eri]]&nbsp;5.49; [[59 Eridani|59&nbsp;Eri]]&nbsp;5.76; [[60 Eridani|60&nbsp;Eri]]&nbsp;5.03; [[Omega Eridani|61/ω&nbsp;Eri]]&nbsp;4.36; [[62 Eridani|62/b&nbsp;Eri]]&nbsp;5.50; [[63 Eridani|63&nbsp;Eri]]&nbsp;5.39; [[S Eridani|64/S&nbsp;Eri]]&nbsp;4.74; [[Psi Eridani|65/ψ&nbsp;Eri]]&nbsp;4.80; [[66 Eridani|66&nbsp;Eri]]&nbsp;5.12; [[Beta Eridani|67/β Eri]] 2.78; [[68 Eridani|68&nbsp;Eri]]&nbsp;5.11; [[Lambda Eridani|69/λ&nbsp;Eri]]&nbsp;4.25; [[82 Eridani|82/e&nbsp;Eri]]&nbsp;4.26

:**Réaltaí suntasacha eile:*'
:* [[EF Eridani|EF Eri]] 14.5 - <17.5 – [[réalta athraitheach mhórchorraíola]]
:* [[Alfa Fornacis|12 Eri]] = Alfa Fornacis

== Féach fosta ==
* [[Sonraí réaltmhéadracha ag baint leis an Abhainn]]

== Naisc sheachtracha ==
* [http://www.alcyone.de/SIT/bsc/ Yale Bright Star Catalog]
* [http://homepage.ntlworld.com/robin.gatter/data/Eri.htm an Abhainn ar shuíomh Robin Gatter] 
* [http://www.ianridpath.com/startales/eridanus.htm *Star Tales'' de chuid Ian Ridpath]
* an Abhainn agus Miotaseolaíocht an Domhain 
* an Abhainn ar shuíomh Richard Dibon-Smith
* Peoria Astronomical Society: an Abhainn 
* The Deep Photographic Guide to the Constellations: an Abhainn

## Tagairtí
* 

Abhainn