Finding Himalia

 You probably already know this but Jupiter has a lot of moons. At last count there are 80 of them.

The orbits of Jupiter's moons shown in SkySafari Pro

Four of the 80 are big, famous and easily seen in just about any telescope. Galileo saw them back in 1610 and they are often referred to as the Galilean Moons. 

From left to right: Europa, Jupiter, Callisto, Io and Ganymede.

Those four moons of Jupiter are often viewed by amateur astronomers, but what about the others? Can they be seen? As it turns out, yes they can. They are small, faint and difficult targets because they are also located somewhat close to the glare of Jupiter.

The largest of Jupiter's moons that isn't one of the famous four Galilean ones is Himalia. Himalia has never been seen from close range by spacecraft, but it is thought to be possibly over 100 miles across.

Himalia's orbit is located far outside the orbits of the Galilean Moons

Himalia is so far from Jupiter that it takes about 250 days for it to complete an orbit. Compare that to Earth's Moon which takes 27 1/3 days or Jupiter's Moon Io which circles Jupiter in just 42 hours. 

While Himalia is far from Jupiter it is still a difficult target to see. The best time to catch Himalia is when Jupiter is closest to Earth. This means that Himalia will be somewhat brighter and there will be a larger apparent gap between it and Jupiter.

I took a look for Himalia about a week after Jupiter's most recent closest approach and found two things. 1) SkySafari, which is an otherwise excellent app, doesn't accurately plot Himalia's position. That's okay, there are other ways to get accurate coordinates for a planetary moon. 2) The glare from Jupiter is excessive. Take a look:

That's an image from August 27th taken with my Unistellar eVscope. Himalia is easily bright enough to be seen with the telescope, but the glow of Jupiter complicates things. When I took a close look at the image I found one star-like object that wasn't where a star should be. To make sure I had the right thing I needed to look again to see if it moved. Himalia's distant orbit around Jupiter means that it is moving pretty slowly through space, but Jupiter itself is moving around the Sun, as is Earth, and means that looking again the next night would place the moon in a different location against the background of the sky. 

Here's my image on August 28th:

The glare from Jupiter is different, but I do have overlapping stars. To see if I caught Himalia I just needed to align and blink the images. Here is the result:

Can you spot it? Yeah, it's difficult. Look on the leftmost third of the image, or, better yet just look below where I cropped and zoomed the images and circled Himalia:

I checked its relative location and relative brightness and I'm confident that I actually bagged it, but I confess that it was trickier than I thought it would be. 

I'll give this a shot next year when Jupiter again is in the proper position to find Himalia.

In And Out The Window

Here's a photo I took recently of the Milky Way with the constellations of Sagittarius and Scorpius over the rocks of Joshua Tree National Park:

It was taken with my iPhone using a new, free app for iOS called Nocturne. 

Above those majestic rocks you can see the light of countless stars and the dark silhouettes of cosmic dust clouds. The exact center of the Milky Way is in this general direction, but we can't actually see it. There's so much gas and dust there that the center is invisible to everything except telescopes that can see into the infrared and longer wavelengths (such as radio waves). 

Yet there is an area known as Baade's Window that is somewhat clear of dust and gas allowing us to see objects that are almost as distant as the center of our galaxy. This window is roughly centered on a globular star cluster known as NGC 6522, which is one of two globular star clusters that can be seen in the image below:

This image, which was taken with my Unistellar eVscope, shows globular star cluster NGC 6522 (right of center) and a somewhat smaller globular star cluster known as NGC 6528 (on the left). Even though this view is looking through Baade's Window notice that there are some dark nebulae visible here, especially on the left side of the image.

Determining distances is a somewhat inexact science. Current estimates put the center of the Milky Way at around 26,000 light years from us while NGC 6522 is around 25,000 light years away. That puts it somewhat in the same neighborhood as the center of our galaxy.

Of course within the constellation of Sagittarius we can see things that are farther than the center of the Milky Way, but you have to look in a somewhat different direction. The Milky Way's gas and dust blocks our view across much of Sagittarius which is why astronomers interested in other galaxies have referred to the disk and center of our galaxy as the Zone of Avoidance. 

The image below shows something that is not just on the other side the center of our galaxy, it is actually outside of it.

Can you spot it? It is Barnard's Galaxy (NGC 6822), the large fuzzy area near the middle of the image. Barnard's Galaxy is a dwarf irregular galaxy that's located about 1.6 million light years away. Like the globular star cluster it is also in the constellation of Sagittarius, but it is not seen in the same direction as the plane of our galaxy and the Zone of Avoidance.

 Here's the same image as before, but cropped on the galaxy itself. Notice the two blue regions near the top of the galaxy. Those are vast gas clouds of gas (nebulae) within the galaxy. I am still impressed that I can catch them with a 4.5" telescope.

Sagittarius is a big constellation. This view from SkySafari Pro shows the locations of these objects. The globular star cluster is on the edge of the spout in the Teapot of Sagittarius and very much in the heart of the Milky Way. While Barnard's Galaxy (top, left) is well outside the Zone of Avoidance. If it were in a different part of Sagittarius we might not even know that it was there at all.

Recent Shots of the Cosmos

I've  got a few projects that I am working on right now that I will eventually blog about, but they're not quite finished, so I thought I would just drop some of my recent astrophotos here instead.

Last weekend I was at Joshua Tree National Park for their Night Sky Festival. I was running a telescope for Unistellar and showing off the coolest astronomical objects of the night sky. I was also on a secret mission to show a few objects that were part of a theme that led up to a successful marriage proposal. The final object just before the question was popped was NGC 6781, the Little Ring Nebula:

The Little Ring Nebula is a planetary nebula which is a bubble of gas that is being given off by a dying star. It is located a few thousand light years from our Solar System in the constellation of Aquila, the Eagle.

Also, located in Aquila is the dark nebula known as Barnard 143, which, along with Barnard 142, makes up what is sometimes called Barnard's E. 

Like with the other dark nebulae I've blogged about it is a dense cloud of cosmic dust that is blocking the light of the stars behind it. 

Our Milky Way galaxy is dusty, which is typical of spiral galaxies. We can see these dust clouds in our own galaxy and we can see them in other galaxies too, such as this one:

NGC 891 is a spiral galaxy that we are seeing from the side, which make its dust lanes easy to spot. It is located nearly 30 million light years away in the direction of the constellation of Andromeda. 

Here's another galaxy located in Andromeda. It is both closer and smaller than NGC 891.

The really bright thing is a red giant star in our own galaxy known as Mirach (aka Beta Andromedae). It's about 200 light years from us. The galaxy in this image is the fuzzy smudge that is up and left from Mirach. It is cataloged as NGC 404 and often referred to as Mirach's Ghost, because it almost looks like a reflection of the brighter star. Mirach's Ghost is a dwarf galaxy that's around 3 times closer to us than NGC 891 is. 

That's all for now. I've got an elusive object to try to hunt down.