Observing report 5 April 2020, Hunting red giants in Carina.

Observing report for 5^th April 2020

For the first time in months I was able to take advantage of clear skies, this was also day 9 of 21 for the lockdown here in South Africa. Almost halfway through and I get a lucky break with a near full Moon thrown in for good luck!

There was no real plan for this session until a chance look at Beta Cruxis and the beautiful red variable star DY Crucis that lies nearby. I then decided to swing over to the Carina Nebula and have a look at one of my favourite red stars there. From there I used sky Safari to pinpoint a few more and made a session of it.

I have observed and logged many of the open clusters both in and around the nebula but never the red super giant stars, of which there are many more than I logged in this session!

After that I surfed about and looked at many familiar favourites before closing up shop for the night as high thin clouds started to degrade the eyepiece views. There was a small amount of dew settling but not enough to ruin things.

The Carina Nebula at first magnitude is a diffuse nebula with the largest regions of HII  in the Milky Way. It is also far larger than the Orion Nebula. It was first discovered by Nicholas Louis de Lacaille while in South Africa at the Cape of Good Hope in 1751-2, it fell within part of the much larger and now defunct constellation of Argo Narvis and is now part of the modern Carina constellation.

de Lacaille was responsible for the dismantling of the huge Argo Narvis constellation, he noted over 160 stars visible to the naked eye in it.

He broke it down into the three new constellations that were adopted by the International Astronomical Union in 1930.

These are Carina, the Keel.

Puppis, the poop deck or stern.

Vela, the sails.

The Nebula lies at an approximate distance of 6500 to 10 000 light years from Earth.
You can read more on this nebula HERE.

The kit used for this session was my Orion XT 8 and a 25mm eyepiece.

Also had SkySafari 6 Pro on a tablet with me at the scope. The link to SkySafari can be found in the right column of this page.

All images below are taken from SkySafari.

First two images show a wide field of the area and then a closer look.

RT Carinae, 8^th magnitude variable star.

This is another deep red star that easily stands out from the surrounding stars. This star lies within the Carina nebula and is also part of the Trumpler 15 Open Cluster.

RT Carinae is a red super giant of the spectral type M2la-0. It’s surface temperature is 3370 Kelvins, it’s total luminosity is 203 times that of the sun. It has a mass of 19 Solar masses.
RT Carinae lies at an approximate distance of  1431 light years from our sun.

 BO Carinae, 7^th magnitude variable double star.

This appears more orange in the eyepiece and once again stands out easily from the surrounding field of stars. It also thought to be a part of the Trumpler 15 Open Cluster.

BO Carinae is a red super giant of spectral typeM4(lb), it has a surface temperature of 3043 kelvins and it’s luminosity is 191132 times that of the sun. It has a mass of 23 Solar masses.
BO Carinae distance is uncertain along with it's grouping, if we assume it belongs to the Trumpler 15 Open Cluster then we estimate a distance of 8500 light years. 

Eta Carinae, 6^th magnitude variable double star.

This shows as a nice bright orange colour in the eyepiece and is also located within the Trumpler 16 Open Cluster.

This star has a unique and interesting history and every time I see it I am reminded of the power that lies within the cosmos. Eta Carinae was also formely known as Eta Argus.

Around 1840 this star ejected a large bi-lobed cloud of material, with another, although smaller, ejection in 1890.

This cloud of material is now almost a light year in diameter and known as the “Homunculus Nebula”.

The stars brightness has also varied significantly over the years, in the 1840’s it was brighter than Canopus and was the second brightest star in the night sky, almost rivaling Sirius.

Eta Carina Carinae is of the spectral class BO and has a surface temperature of 30,000 Kelvins. The luminosity is difficult to determine, could be as much as 5 million suns!

It has a estimated mass of between 100 and 150 Solar masses.
More on the star can be found HERE.

IX Carinae, 7^th magnitude variable star.

This is the first star that lies just outside the Carina Nebula. It is another deep red star that is easily picked out from the field.

IX Carinae is a red super giant of spectral type K5/M0lab with a surface temperature of 3999 kelvins and a luminosity 5360 times that of the sun. It has a mass of 13 Solar masses.
IX Carinae is approximately 5224 light years from our Sun.

w Carinae, 4^th magnitude variable star.

Back in the nebula this is a very bright and distinctive orange star, stands out very well from the surrounding star field!

wCarinae is a red giant of spectral type k4III. It’s surface temperature is 4136 kelvins and a luminosity 3316 times that of the sun. It has a mass of 1.2 Solar masses.
w Carinae is approximately 1140 light years from the Sun.

We now leave the Nebula and find our last remaining targets surrounding it.

HR 4177, 4^th magnitude variable double star.

Another reasonably bright orange star that is easily picked up from the surrounding field.

HR 4177 is a red giant of spectral type K4-5III with a surface temperature of 4163 kelvins and a luminosity 11893 times that of the sun. It has a mass of 1.2 Solar masses.
HR 4177 is approximately 2346 light years from our Sun.

HR 4179, 5^th magnitude double star.

Another bright orange star in a slightly less cluttered star field.

HR 4179 is a red giant of spectral type M1III and a surface temperature of 3615 kelvins and a luminosity 529 times that of the sun. It has a mass of 1.2 Solar masses.
HR 4179 is approximately 682 light years from our Sun.

r Carinae, 4^th magnitude variable star.

For this we move slightly further away from the nebula.

A very bright orange star presents in the eyepiece here.

r Carinae is a red bright giant of spectral type K3-4III with a surface temperature of 4390 kelvins and a luminosity 3041 times that of the sun, with a solar mass of 1.2 Solar masses.
r Carinae is approximately 1177 light years from our Sun.

q Carinae, 3^rd magnitude variable double star.

Another bright orange star in the eyepiece and substantially further away from the Carina Nebula.

q Carinae is a red bright giant with a surface temerature of 4390 kelvins and a luminosity 2565 times that of the sun.

It has a mass of 1.2 Solar masses.
q Carinae is approximately 658 light years from our Sun.

And that concludes this brief trip through the Carina Nebula in search of red giants.

As mentioned there were several other targets during the 4 hour session but these were worth a full report on their own.

Some of the other targets included NGC 5139, NGC 4755, IC 2391, IC 2602, NGC 2516, NGC 6231, NGC 6322, NGC 6388, NGC 6475 and NGC 3532 along with a few others I did not note down.

Thank you for reading.