40 Eridani - a great triple!

[Merlin]

I've seen the Omicron2 white dwarf in a Prinz 60mm/f.11 refractor some years ago; it was more obvious with averted vision. The White dwarf orbits the red dwarf in 240 years and the pair orbit the primary in 8000 years. There' s all the time in the world in astronomy.

As you say, this is an interesting trio, showing three stars in different stages of stellar evolution.

[Mr Spock]

It's a nice triple. Well worth a revisit.

[Martthebass]

I'll have to revisit this one, the last time I looked was in the early 2000s with a 8" SCT.  Sadly the murk was a little too thick so I couldn't catch the red dwarf, I was very happy with seeing my first white dwarf though. 

[lenscap]

I've put this on my list, in case we ever get another clear night here! 😀

Astonishing that the white dwarf can be seen at all - it is 16 light years away and only about twice the diameter of the Earth!

[Captain Scarlet]

On my list. Very glad I stumbled on this thread.

M

[Captain Scarlet]

... looked up White Dwarf on Wiki. Discovered that Sirius B is also a White Dwarf. Makes my mission to observe it for the first time all that much richer...

M

[John]

17 minutes ago, Captain Magenta said:

... looked up White Dwarf on Wiki. Discovered that Sirius B is also a White Dwarf. Makes my mission to observe it for the first time all that much richer...

M

Apparently, Sirius B is a little smaller than the Earth but it's mass is very nearly that of the Sun !

 

 

 

[aderyn]

On 24/12/2020 at 20:02, Hyperion76 said:

very interesting triple I often bump this topic 

Thanks for the bump, I wouldn't have known about it otherwise. Now just need some clear skies.

[Captain Scarlet]

I found it last night, this thread is what brought it to my attention. Thought-provoking and a very nice sight.

M

[skyhog]

Yes, a very good bump. Reminded me to have a look at this again after many years. I must have forgotten the significance of this triple, so I slewed the scope over to it last night and had a good look. Amazing to think how small that white dwarf actually is and what distance we are observing it. It probably took me a while to learn about this star as it doesn't get a mention in what was for me 'the bible' of observing back in the early 70s, Patrick Moore's 'The complete Amateur  astronomer'. Odd really as he does talk about white dwarfs and mentions this triple in the constellation guide at the back of the book, but fails to mention it. It was the first to be observed, and its relatively easy with modest scopes. And one of the largest super earths known was found to be orbiting eridani A back in 2018, a great target, and a well timed bump. 

Edited January 30, 2021 by skyhog
spelling!

[Nik271]

Enjoyed reading this thread! I will try to have a look at 40 Eridani next time the sky is clear.

[Space Hopper]

Me too..........🙂

[domstar]

Wow, I've found it. I couldn't find it last night and after many attempts I saw it tonight. Rigel is just too far to star-hop confidently from. The white dwarf was clear but it took me quite a while before I could hold it in direct vision. I tried 50x, 90x and 150x but couldn't be sure about the red dwarf. I had a little look at Orion and came back with my Vixen plossl. It shouldn't be better than my BCO but it did the trick at 90x. I'm really pleased. A tough challenge for me but so rewarding.

Thanks to everyone who has contributed to this thread. This is what SGL is all about. I wouldn't have known anything about it without this thread.

[Nik271]

I'm pleased to report that I managed to see the three stars in 40 Eridani last night.

The seeing started excellent and around 6:30pm I could even make the E and F stars of the Trapezium: E with direct vision and F with averted.

I was using a 180mm Mak with 20mm EP giving x135.

So I pointed at 40 Eridani and the white dwarf (B) was immediately obvious. With averted vision I could tell it was a double star. I put a towel over my head and dark adapted for 10 minutes, and was able to see the red dwarf (C) with direct vision! Very pleased about it, especially since the seeing went downhill from then on. 

I made this sketch from memory:

 

Thanks to all people who contributed to this thread, this is where I learned about this interesting triple star!