Tag: stars

Would you like to look at a Black Hole?

Obviously you won’t see the Black Hole itself. A Black Hole is, well, black. It’s gravity is so intense that not even light can escape it. But I can point you to a couple of places where there almost certainly is a black hole.

Every large galaxy (probably) contains a supermassive black hole at its centre, including our own. So you just have to look at any galaxy in the sky and you’ll be looking at a black hole. Our own galaxy’s supermassive black hole is called Sagittarius A*. It has a mass over 4 million times the mass of the sun. If you’re familiar with the “Sagittarius Teapot” then it’s an easy find.

https://earthsky.org/favorite-star-patterns/teapot-of-sagittarius-points-to-galactic-center/
https://en.wikipedia.org/wiki/Sagittarius_A*

Unfortunately this is too low in the sky for me to see from my back garden. However, there are much closer black holes to earth, some of which are on our cosmic doorstep.

https://en.wikipedia.org/wiki/List_of_nearest_known_black_holes

The one I’m going to point out was the first confirmed, stellar mass, black hole. Lying 7,000 lights years from earth, it’s very easy to find in the night sky, especially right now.

We begin with our friend, the Summer Triangle. The three vertices of the triangle are the stars Deneb, Vega and Altair. They all lie due south at midnight at the moment and dominate the summer sky in the UK. The Milky Way, if you’re lucky enough to be able to see it, runs along the line connecting Deneb and Altair.

Deneb is the brightest star in the constellation of Cygnus, the Swan. This constellation also goes by the name of the Northern Cross, for obvious reasons when you see the picture below. Here’s a picture of the Summer Triangle and Northern Cross, taken with my Panasonic GF7 and a wide angle lens.

Follow the cross down from Deneb to Sadr, the centre of the cross. Then keep going to Eta Cygni. This is the star we’re interested in.

In the 1960s, when they first sent rockets equipped with X-Ray scanners above the earth’s atmosphere, it quickly became apparent that there was a very strong X ray source somewhere in the constellation of Cygnus. This was labelled as “Cygnus X ray source number one”, Or Cygnus X-1 for short. As better and better satellites did more refined observations, the source was narrowed down to near Eta Cygni. The actual star where they seemed to originate was very nearby. The star doesn’t have a name, just a catalogue number, HD 226868.

HD 226868 is a very massive, very hot star, about 30 times the mass of the sun. However, it’s not that hot that it should be emitting the kind of X rays that are observed from it. Studies of the star’s spectrum revealed a wobble due to a hidden, equally massive, companion. This hidden companion lies about the same distance from the star as earth is from Venus’ orbit. Almost everyone agrees that this hidden companion is a Black Hole. Even long term sceptic, Stephen Hawking, eventually conceded the point. The solar wind from HD 226868 provides just enough material to feed this hidden companion and let it generate the X rays that we see above the earth’s atmosphere.

Here’s a picture of HD 226868 taken with my Seestar S50. The bright yellow star on the right is Eta Cygni. For scale, the distance between the two stars in this picture is about half a degree in the sky, the width of the full moon. That may sound like a lot, but the full moon isn’t nearly as big as many people think it is. It only spans about a tenth of the angular distance between Eta Cygni and Sadr at the centre of the Northern Cross.

So next time you’re looking up at the sky, see if you can find Eta Cygni. When you do, you’re looking almost directly at a Black Hole.

https://en.wikipedia.org/wiki/Cygnus_X-1

Have you Seen the Eagle Nebula?

It’s kind of a rhetorical question, since most people reading this almost certainly have seen the Eagle Nebula, also known as M16 (number 16 on Charles Messier’s list of things that aren’t interesting because they aren’t comets). It’s just that it probably wasn’t called that when you saw it.

First of all, some directions for finding it. If you look due south at about 2am you should see an unmistakable triad of stars that span most of the southern sky. These are the three bright stars Vega, Deneb and Altair, often referred to as the “Summer Triangle”. The Eagle Nebula can be found southwest of the lower star, Altair.

The nebula lies about 7,000 light years away. But as always, unless you have exceptionally dark skies and a large telescope, you’re unlikely to see very much. Point a camera at it and take a couple of hours exposure and you get this.

The “Eagle” refers to the dark silhouette at the centre. But that still might not look familiar. If I zoom in and crop then you should get a better clue where you’ve seen it before.

And if that still doesn’t ring any bells then it’s time to see it as Hubble sees it.

Yes, the justly famous “Pillars of Creation” form a small part of the Eagle Nebula. You can see more of these iconic images on NASA’s website.

https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-16/

Three degrees to the southeast of the Eagle Nebula, you can find the Swan Nebula, M17. I’ve been collecting a regular zoo this week.

Personally, I struggle to see a swan anywhere in this. I think the bright patch is meant to be one of the wings with the neck starting on the left and curving up to the right. But I’m not at all sure about that. Maybe you’ll have better luck?

More images on the Sky at Night web page.

https://www.skyatnightmagazine.com/astrophotography/nebulae/the-omega-nebula

And if you’ve read through all of that, or even if you haven’t, a very Happy Summer Solstice to you all!

The Dumbbell Nebula and Markarian’s Chain

M27, the Dumbbell Nebula, has made regular appearances on this blog. It’s a large “planetary nebula” blown off from the surface of a dead star, which now lies as a white dwarf at its centre.

https://www.skyatnightmagazine.com/space-science/planetary-nebula

White dwarf’s themselves are fascinating objects. They have a mass similar to our sun, but compacted down to something the size of planet earth. They no longer generate energy and are in the process of cooling down. Eventually, they will become black dwarfs: dense, burnt out cinders. But since the time taken for a white dwarf to cool is calculated to be longer than the current age of the universe, no black dwarfs are currently expected to exist.

https://en.wikipedia.org/wiki/White_dwarf

My previous best effort for the dumbell was limited by the use of a manual telescope and camera. The colours here are false.

The other night, for the first time, I pointed the smart telescope at it. I took two, 5 minute, stacked exposures. One with the telescope’s light pollution filter (which makes the nebula brighter) and one with it’s infra-red and ultraviolet filter (which shows more stars). The result is a combination of the two.

https://en.wikipedia.org/wiki/Dumbbell_Nebula

At about 1,000 light years distance, The Dumbbell Nebula is on our cosmic doorstep. This was a rather pretty distraction from the real effort this week though. That was Markarian’s Chain, a long string of galaxies about 50 million light years away. They’re named after the Armenian astronomer Benjamin Markarian, who demonstrated that they were all part of the same group, moving through space together.

This is too large an object to fit in most telescope and camera combinations. It takes multiple images, patched together as a mosaic to build the whole picture. Fortunately, the smart telescope knows exactly how to do this. The following image took it four hours to assemble fully. This took several attempts, but I’m fairly happy with the result.

https://en.wikipedia.org/wiki/Markarian%27s_Chain

I really recommend the full size version of this, seen on a big screen rather than a phone.

https://mega.nz/file/B9oxySBJ#bRNB8hOzvV-D8jSefOKfzTDKx-UQukrSghr6jZ1gxyc

I’m hoping to do even better some time soon. I’ve been experimenting with putting the smart scope on an “equatorial mount”. This allows it to track the apparent rotation of the sky by having a fixed axis that points at the north celestial pole. Initial efforts look good, but I need some clear, moon free, nights to really try it out properly. This would remove a lot of the rotation artifacts present in the above picture.

Which Moon Pic do you Prefer?

Here are two very similar pictures of the moon. One taken with my 6 inch Skywatcher reflector and a Lumix GF7 camera. The other taken with the Seestar S50 2 inch refractor.

Do you have a preference? It might not be easy to decide as I’ve tried to make their size, orientation, contrast and colour as similar as possible. Here’s a higher resolution version. (I recommend that the high res pics are viewed on something a bit bigger than a phone.)

https://mega.nz/file/Q5J0xZpJ#R3Cr1oE-uMUuLBEs7Z8XLaDz6fhTS8WcgRQT1k5Sfk0

I’ll come back to this later. To maintain the air of mystery and suspense, I won’t say yet which picture came from which telescope.

I was hoping to show some splendid pictures of the total lunar eclipse from Friday morning. It was a beautiful clear sky all night with the forecast to remain fine. The moon was full and looked absolutely glorious, all ready to move into the Earth’s shadow. I had both telescopes set up and ready to go (even though my back pain was giving me hell). The S50 was going to do time lapse movies, while the Skywatcher would record high resolution pics. Then, with ten minutes to go, this happened…

And here’s a short movie of the clouds doing their thing, getting in the way.

https://mega.nz/file/d94gEYAR#avI8f17wZWyNmsQcY_yk6zEAGqWwSyGBJx7U-8aRu_Q

I waited for about half an hour, hoping that the cloud was just temporary, but it just got thicker and thicker, until the moon was completely obscured. So I put all the equipment away and came back inside. Just after dawn, when the moon had set, the sky cleared again. If I was so inclined, I might suspect that someone was trying to tell me something.

Here are some pics from those who were more fortunate.

https://www.bbc.co.uk/news/articles/cr42k4qpr7go

Still, we had some lovely clear nights over the last week or so. I managed to enlarge my set of waxing moon phases. Adding in some from January, it now looks fairly complete.

On the night of the thinnest crescent moon, I also took an overexposed shot to reveal the part of the moon in shadow.

And on the night of March the 7th to 8th I took one of those comparison photos that shows the terminator moving overnight.

https://mega.nz/file/14Y0yZoZ#TN-ONWQ_APudub341L5jjr5Hnk73Yut0EyRSNqvYV8E

The waxing moon is the easy bit though. It appears from early evening and usually means going out either just before, or just after, tea. The waning moon is very different. It’s OK getting the initial stages, but the later crescents mean being out early in the morning close to dawn. Let’s see how dedicated I can be.

Now back to the telescope comparison at the top. Personally, I can’t tell a lot of difference between the two when viewed on a web page. However, when you zoom in, the difference becomes more obvious.

https://mega.nz/file/4lwjVDZS#s_2lEd2iIk4RbKo7wOeVH0gzIPrjMsW9db28WiYD1uA

In both cases, the right hand picture comes from the larger, six inch, scope. The close up illustrates the much higher resolution that the larger scope is capable of. This is what I’ve found using the smaller smart telescope over the last couple of months. It’s absolutely fantastic for just putting outside and telling it to go take a picture of something. Incredibly easy. It produces amazing results for publishing on the web. But take a closer look and its pictures are all a bit fuzzy. It wets the appetite, making you want to try to do something better.

The larger scope can produce much more detailed pictures, but it isn’t “smart”. It takes a lot of fiddling about to keep it on target and to keep taking images.

Oddly enough, the manufacturer of the smart scope also supplies a lot of higher resolution, and much more expensive, equipment. If this is a clever marketing strategy then I have to say it’s working. I’m looking at their more expensive gear. This little box of tricks, for example, can turn almost any scope into a smart scope.

https://www.firstlightoptics.com/zwo-cameras/zwo-asi2600mc-air-wireless-smart-camera.html

But just look at the price! I think I might have to save up my pocket money for that one.

And finally, this morning’s nearly full moon.

https://mega.nz/file/Z1oEAQya#CVKKdHK0V3Gy9I7Y2iSYfFg1eLB6xRdpuc5g1755iv8

A Cluster of Clusters

Look south just after sunset today and you’ll see the unmistakable constellation of Orion.

Follow Orion’s belt left and down and you find Sirius, the brightest star in the sky. Sirius is so bright for two reasons. First, it really is a bright star, shining some 25 times brighter than the sun. Second, Sirius is on our cosmic doorstep. At a mere 8 light years away it’s one our next door neighbours in space.

https://en.wikipedia.org/wiki/Sirius

Sirius is surrounded in our view of the sky by a bunch of light smudges. These are open clusters of stars. A closeup map from Stellarium shows a few of the brighter ones. Many of these are visible with binoculars.

And here are a few of the brightest ones: M46, M47 and M50.

I particularly like M46 because it includes a bright orange foreground star, 140 Pup, a red giant 700 light years away. This contrasts with the main cluster which is nearly 5,000 light years away.

https://en.wikipedia.org/wiki/Messier_46

Open star clusters tend to show mainly young, bluish stars. They’re usually regions of recent star formation where the constituents haven’t yet dispersed. We mostly see the brightest members which tend to be blue-white in colour. Their dimmer, yellow-red companions are outshone by these blue-white stars.

M46 has another surprise though. It also includes a planetary nebula, shown near the top left of this photo. It goes by the charming name of NGC 2438.

https://en.wikipedia.org/wiki/NGC_2438

Again, this is a foreground object about 1,300 light years away. It’s not a true member of the cluster. Planetary nebulae have nothing to do with planets. They just look a bit like planets. They’re the remnants of old stars that have blown off their outer atmosphere and are now illuminated by the remaining core at their center. Given that this is an older star, it should now be obvious that it can’t truly be part of the open cluster M46.

On the opposite side of the sky, I’m still stacking photos of M13, the Great Globular Cluster in Hercules. This is three night’s worth of photos stacked. I’m not sure if adding any more to this will improve the quality or not. Only one way to find out…

All photos taken with my Seestar S50.