Jump to content

548140465_Animationchallenge.jpg.32379dfa6f3bf4bba537689690df680e.jpg

Spectacular Conjunction of Io with a red star in Taurus!


Starfleet
 Share

Recommended Posts

In my Sky Diary for 2013, I have for the night of 3rd January (this coming Thursday) a fascinating conjunction of Jupiter’s Galilean satellites with a 6th mag red star in Taurus! This is what I wrote in my self-compiled list of interesting forthcoming conjunctions:

“January 3rd 2013 – Jupiter and its four Galilean satellites pass the sixth magnitude red star Hip 20417 later tonight. Compare the colours of Jupiter’s moon Io and this star at midnight tonight, to see if Io looks as red as the star or perhaps even redder?”

I have previously noticed the colour of Io, just comparing it to the other Galileans and it always seemed a darker shade of yellow. I won’t have my Tal-1 scope to hand for this rare event (the red star Hip 20417 is genuinely quite red, with a B-V colour index of +1.86 - from Stellarium).

Should be fun to watch in my 10x50 binoculars though - weather permitting!

Has anyone noticed Io’s colour through binoculars? Must be a challenge...

  • Like 1
Link to comment
Share on other sites

Happy New Year Tim, hope you're having a good one.

I think Io's colour would be hard to discern just with the binos as you say, but maybe if Io is at its widest away from Jupiter's disk, who knows?

You know, I just re-did my simulation and it turns out that it may be more favourable to view this on the evening of 5th Jan (this Saturday), when Io and the red star are both isolated away from the crowd:

post-2629-0-98353600-1357042039_thumb.jp

Link to comment
Share on other sites

Hi Abdul,

Thanks for your message. I've joined Stargazers Lounge - I didn't realise it was so popular and extensive. My CCD camera is black and white so I won't be able to make an objective comparison between Io and the star but I'll certainly view visually.

Best wishes,

John

  • Like 1
Link to comment
Share on other sites

I’m sure you’ll enjoy it here John, it’s a great forum.

Well on Thursday night it was the clouds in our own atmosphere that stole the show and not the ones on Jupiter, unfortunately. Forecasts for tonight aren't much rosier.

I did e-mail this to a couple of friends across the Atlantic, so I’m hoping they’ll have better viewings under clearer skies.

The Astronomical Almanac of 1988, on page F3, gives a photometric B-V colour index for Jupiter’s moon Io as +1.17. Based on its B and V magnitudes from Simbad, the colour index of HIP20417 comes out at +1.66, so a bit redder.

Considering that the brightnesses of both Io and this star are quite similar, it is a pretty outstanding chance alignment of the two for us to make direct colour comparisons between them, whether it be simply by eye or by CCD photometry.

I’d love to see some colour pics! :laugh:

Regards,

Abdul

Link to comment
Share on other sites

In my Sky Diary for 2013, I have for the night of 3rd January (this coming Thursday) a fascinating conjunction of Jupiter’s Galilean satellites with a 6th mag red star in Taurus! This is what I wrote in my self-compiled list of interesting forthcoming conjunctions:

“January 3rd 2013 – Jupiter and its four Galilean satellites pass the sixth magnitude red star Hip 20417 later tonight. Compare the colours of Jupiter’s moon Io and this star at midnight tonight, to see if Io looks as red as the star or perhaps even redder?”

I have previously noticed the colour of Io, just comparing it to the other Galileans and it always seemed a darker shade of yellow. I won’t have my Tal-1 scope to hand for this rare event (the red star Hip 20417 is genuinely quite red, with a B-V colour index of +1.86 - from Stellarium).

Should be fun to watch in my 10x50 binoculars though - weather permitting!

Has anyone noticed Io’s colour through binoculars? Must be a challenge...

I did eventually get to observe the star and Io when the clouds cleared here using the Apollo 15x70's. The star appeared darker-oranger than Io which looked yellowish to me.

Hope you were also able to view.

Cheers,

Steve

Link to comment
Share on other sites

Glad you could see it, Steve. The clouds were horizon to horizon on both nights of conjunction where I am, so no such luck I'm afraid.

Still, from your report and also similar reports over on Cloudynights we can safely say Io was less red visually than the star. Which I'm told, incidentally, is a close double star, well worth attempting to split if you have a small scope geared up to a high magnification.

Staying on the subject of the ruddy colour of Io, because of its pizza-like surface covered with sulfur, it is quite an orangey/reddish colour in close up photographs. However, it is not the reddest satellite in our solar system. That top spot is occupied by Jupiter's tiny inner moon of Amalthea (14th magnitude, so not for the faint hearted! :grin: )

Saturn's moon Titan is apparently a bit redder than Io, with a B-V colour index of +1.28, though it is of course much fainter at mag 8.5-ish...

Link to comment
Share on other sites

The clouds cleared tonight for about an hour (although not great seeing - a lot of moisture in the air I think), and as per usual the last few months, I started off with Jupiter. It confused me as to why I could see what appeared to be five Galilean satellites, with four of the moons to one side of Jupiter and the fifth on it's own on the other side. A quick check on Stellarium reveals that at the time I looked (about 20.30 UTC), it was indeed HIP 20417 on it's own, in a similar, but opposite position to Callisto.

It made for quite an interesting view, especially when I wasn't expecting it!

Link to comment
Share on other sites

I too was viewing Jupiter last night and spotted an orange coloured object , I too used stellarium to find that the object is hip 20417 . Not bad for my first night out with the 200p dob. Kevin

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.