Asteroid Encounters

This year I have observed more asteroids than ever before with 29 detected so far. Some them have been as a part of the Unistellar Citizen Science campaigns, but most of them have just been for fun. For instance, earlier this week I looked at the asteroid 626 Notburga which was in the constellation of Cassiopeia.

The image above is an animated gif of two images taken 75 minutes apart showing Notburga's motion though the sky. The individual exposures were short so it wasn't easy spot the nebula that was nearby it in the sky. So in between these two images I took a longer one to try to bring out a part of the Heart Nebula.
 

Here the asteroid appears as a line and there's some hint of the red hydrogen gas of the Heart Nebula across much of the upper right portion of the image. 

Since asteroids look like moving dots or streaks it is sometimes more interesting to catch them when they are near some other astronomical object in the sky. A great resource to find out when as asteroid will be near a bright star, a deep sky object or even another asteroid are the observing guides at MinorPlanet.info. I've used that to find all of the close encounters on this page.

Here are asteroids 712 Boliviana (top right) and 89 Julia (below center) from back in October:

Just this week asteroids 1 Ceres and 1140 Crimea have been passing the bright star Aldebaran.

Aldebaran is the bright star at center. Asteroid (and dwarf planet) 1 Ceres is the bright moving object to its lower right. Much fainter is 1140 Crimea. It is the faint moving dot in the upper left. At the time of the images Crimea was actually 25 million miles closer to Earth than Ceres. That doesn't help it much in brightness though because it is much smaller. 1146 Crimea is just 17 miles across while Ceres is 587 miles across!

In early October asteroid 27 Euterpe passed directly in front of one of my favorite globular star clusters: Messier 22. I caught the event on two nights as the asteroid was near the cluster, but it was cloudy the night it passed in front of it.

Euterpe is to the right of the cluster. At the time it was 21 light minutes from Earth, while the star cluster is some 10.600 light years away.

An even bigger disparity in distance was back in March when asteroid 70 Panopaea passed directly in front of spiral galaxy NGC 3344. 

That night asteroid 70 Panopaea was 17 light minutes from Earth while the spiral galaxy is more than 22 million light years from our Milky Way Galaxy.

In the coming weeks and month I will be looking for more interesting asteroid encounters and posting some of them here.
 

The Messier Catalog

I don't know about you, but I finally kept a New Year's resolution. What was it? To use my Unistellar eVscope to observe and photograph all 110 objects of the Messier Catalog. Yes, I know some people do Messier marathons and catch them all in just one evening, but it takes time if you want to take a photograph each and every one of them. Besides, I do like to sleep. 

I caught my first Messier object this year, the famous Orion Nebula (M42), on January 3rd. The last one that I observed was on October 9th: the galaxy known as M77.

I will certainly be revisiting each and everyone of these objects in the future (especially since I'll will soon have the eVscope2), but for your visual enjoyment here are a few mosaics of the objects of the Messier Catalog.

Messier 1 through 20: 

Messier 21 - 40:

Messier 41 - 60:

Messier 61- 80:

Messier 81 - 100:

 and finally Messier 101 - 110:

I've previously blogged about the globular star clusters and the nebulae of the Messier Catalog and I've still got a few things left to say about the whole thing, but I'll save those thoughts for another time.

Andromeda and Her Attendants

Our galaxy the Milky Way is one of several dozen galaxies that make up the Local Group of galaxies, which itself is on the outskirts of the much larger Virgo Cluster of galaxies. The largest and most dominant member of the Local Group is the famous Andromeda Galaxy (M31). M31 is thought to be bigger than our Milky Way in just about every way. It is physically larger, more massive and has more stars than the Milky Way.

If you have dark skies and know where to look on these fall evenings you can see M31 with your own eyes as a fuzzy smudge. It is worth making the effort to see it, especially knowing that this galaxy is far enough away that its light travels for 2.5 million years to reach us, making it the farthest thing that humans can usually see without a telescope (Some have claimed to see galaxy M33, which is farther, but spotting that is much more rare and difficult).

A telescope will reveal M31 as a much larger and brighter fuzzy smudge that more than fills up the field of view. It is only through photography that details such as its dark dust lanes become visible. 

The image above is a partial mosaic (that I really need to finish) of the Andromeda Galaxy that I made with my Unistellar eVscope. It reveals two of Andromeda's many companion galaxies. The round, fuzzy object to the upper left of the central portion of M31 is the dwarf elliptical galaxy known as M32 and in the lower right is M110, another dwarf elliptical galaxy that orbits M31. 

To give you a sense of depth, M32 is about 110,000 light years farther from us than M31 is, while M110 is around 400,000 light years past M31.

But M31 has more companions that can be photographed with the eVscope. One of them is NGC 147, the faint smudge at the center of the image below:

 It's not immediately obvious the NGC 147 is a companion to M31, especially since it lies some seven and a half degrees from it in our sky, but they are together in space separated by some 300,000 light years.

NGC 147's nearest neighbor in the sky is NGC 185, another satellite galaxy of M31 (below, center).

These two galaxies are both found in the constellation of Cassiopeia nearly one degree apart from each other. Of the two, NGC 185 is closer to us by some 500,000 light years, which helps to explain why it is the brightest of the two. 

Wikipedia lists more than two dozen other galaxies that are companions of M31 and I believe that all of them are out of reach from my 4.5" telescope, except possibly for one of them. Aside from M31 and the Milky Way Galaxy there is one other spiral galaxy in the Local Group, M33 in the constellation of Triangulum. It's the smallest of the three and might be in orbit around M31, we aren't certain.

At a distance of 2.73 million light years M33 is farther away than M31 and it has a much lower surface brightness too, but it has some interesting structure to it, with both star clusters and nebulae visible within it making it possibly a fine attendant of the princess Andromeda.

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. 

Globular Star Clusters of the Messier Catalog

Globular star clusters are collections a few hundred thousand old stars that are gravitationally bound together. There are 29 globular star clusters in the catalog of objects that might be mistaken for comets made by French comet hunter Charles Messier in the 1700s. Globular star clusters make up just over 26% of the the 110 on the list. Other objects in the Messier Catalog include open star clusters, nebulae, galaxies and a few odds and ends. It makes sense that globulars would be well represented as a globular star cluster can very much resemble a comet that does not have a tail.

Summer evenings in the Northern Hemisphere are the best time to see globular star clusters as so many of them are in the sky at once. Have a look at this image from the SkySafari app:

The graphic is just over 50 degrees wide and mainly shows the constellations of Sagittarius, Scorpius and Ophiuchus (alas, headless here). Marked on the image are the locations of 16 of the 29 (55%) globular star clusters on Messier’s list. Also marked on the image (up and right from the tip of the arrow of Sagittarius) is the location of Sagittarius A*, the black hole at the center of the Milky Way Galaxy. Sagittarius A* is invisible to our eyes and in optical telescopes, but it is no coincidence that so many globular star clusters are in the area surrounding the center of our galaxy. They are there because they are in orbit around the center of our galaxy. 

Over the last several months I have used my Unistellar eVscope to photograph the Messier globulars. Here is a mosaic I made that shows the first 15 globulars in the catalog:

Row 1: Messier 2, 3, 4, 5, 9. Row 2: Messier 10, 12, 13, 14, 15. Row 3: Messier 19, 22, 28, 30, 53.

 

Here are the rest:

Row 1: M54, 55, 56, 62, 68. Row 2: M69, 70, 71, 72, 75. Row 3: M79, 80, 92, 107.

For some reason I initially felt it was necessary for me to rank the clusters, but as I got started it began to seem like writing about each and every one of them was a far more daunting task than observing them was. So instead, here are a few things that I think are interesting about some of them. 

M107

M107 is the eighth closest globular star cluster in the Messier Catalog, yet it is the faintest of all 29. This cluster wasn’t officially added to the Messier list until 1947, some 130 years after Messier’s death. M107 was discovered by Pierre Méchain in 1782 a year after Messier compiled his “final” list. Méchain, who collaborated with Messier, often shared his discoveries with Messier who then confirmed them and then added them to his list. So why is M107 on the official list? Because it is, though if you ask me these late addition objects (M104 - 110) are on shaky ground. The cluster is not amazing and when combined with the dubious nature of it being on the list it ranks as my least favorite.

M3

M3 is 33,900 light years away in the direction of the constellation of Canes Venatici. It has half a million stars and is 90 light years across. M3 is one of the first globular star clusters to appear in the evening as summer season of globular star cluster observing begins.

M4

Located just over a degree west of the bright star Antares in Scorpius makes M4 an easy target to find in the sky. The cluster is relatively close to us with a distance of just 7,200 light years. It is 75 light years across and has just 44,000 stars, which is kind of low for a globular star cluster. Clouds of interstellar dust lie between us and M4. The dust gives it a distinct orange color and if the dust weren’t there M4 would be much brighter in our skies, as it is it is it is the third brightest on the list.

M13

M13 is widely considered the best globular star cluster of the bunch. It is often referred to as the “Great Hercules Cluster.” What makes it so great? It is the 2nd brightest of the globular star clusters in the Messier catalog. It is also the 2nd most northern of the globulars, putting it much higher in the sky for observers in the Northern Hemisphere. It’s not amazingly close, in fact it is some 22,000 light years away from us. Unrelated, but back in 1974 the now defunct Arecibo radio telescope was used to beam a brief message (the most powerful signal ever sent from Earth) to this cluster. Finally, M13 is an easy target to find because of its location in the “Keystone” asterism within the constellation of Hercules. Is it the best globular on the list? Almost.

M15

M15 is 33,600 light years away from our Solar System. It is seen in the direction of the constellation of Pegasus, which makes it one of the few globular clusters to see in fall evenings (for observers in the Northern Hemisphere). It sports an intermediate mass black hole at its core which weighs in at 4,000 times the mass of our Sun.

M22

At a distance of around 10,000 light years M22 is the 2nd closest of the globular star clusters. It is 97 light years across and shines with a brightness of over 200,000 Suns. It’s visual magnitude is 5.1, making it the brightest of the Messier globular star clusters (Two other globular star clusters are brighter, but they are located too far south for Messier to have observed them). Like M4, there’s dust between us and the cluster, so it would be even brighter if the dust were not obscuring some of its light. Still, it is a beautiful looking star cluster. For most people it loses points for being so far south in the sky, but M22 more than makes up for it by looking so great and giving us stars all the way down to its center. 

Above is a screen grab from SkySafari showing the location of M54 and at right is an image of it. It isn't an impressive globular star cluster, unless you know its story. M54 lies some 87,000 light years from our Solar System, making it the most distant globular on the list by a whopping 20,000 light years! In fact you could even say that M54 is extra galactic, as in it doesn’t even belong to our galaxy, the Milky Way, making it the only globular in the Messier Catalog that lies outside of our galaxy. It belongs to the faint Sagittarius Dwarf Elliptical Galaxy (SDEG). The SDEG is the big (7.5 degrees in length) oval in the image above left. It is possible that M54 might be the core of the SDEG instead of a true globular star cluster. There’s evidence that there’s a black hole at its core. It is one of the most luminous globular star clusters known, shining with a brilliance 850,000x times that of the Sun. There’s just one globular star cluster that exceeds that, Omega Centauri, a cluster too far south for Messier to have seen.

M55

Finally, here's M55. For some reason M55 is one of those star clusters that I tend to forget about, but it is a really nice one. It is one of the seven Messier globulars in Sagittarius. It lies 17,600 light years away and it a beautiful sight to see.

I could go on, but I think that perhaps instead I'll start planning my next observing session.

Going Dark

It all began back in early June when I took a look at the globular star cluster known as Messier 9 in Ophiuchus. I didn’t realize it until I pointed my Unistellar eVscope there, but in the sky very near to M9 is a dark nebula, specifically the dark nebula known as Barnard 64 (The name comes from its entry into a catalog of dark nebulae compiled by Yerkes Observatory astronomer E.E. Barnard in 1919.).

Messier 9 (left) and Barnard 64 (upper right)

Sure, I realized that dark nebulae where out there. You can see them when you look at photos of the Triffid Nebula or the Lagoon Nebula (see my post on Messier Nebulae). The most famous dark nebula of them all is the Horsehead Nebula (Barnard 33)—a dark cloud that is silhouetted against a faintly glowing red emission nebula near the Belt of Orion.

B33, the Horsehead Nebula in Orion

 But to me Barnard 64 is something different than those examples. It’s a dark cloud that is blotting out the light of stars behind it and not a dark cloud seen in front of a bright one. Seeing Barnard 64 started me on a journey to look for more dark nebulae, so I thought I would share a few of the dark things that I’ve recently been looking at.

Also in the constellation of Ophiuchus is Barnard 72, commonly known as The Snake.

The photo above is a mosaic of images that I made with my Unistellar eVscope of The Snake (the big "S"), but also visible in the image are other dark nebulae. To the right of The Snake is Barnard 68 and below that is Barnard 69.

There are plenty of dark nebulae in other constellations too. The center of our Milky Way Galaxy lies in the direction of the constellation of Sagittarius where more members of Barnard's catalog can be found. 

The image above shows dark nebula Barnard 86 next to a small, brilliant open star cluster (NGC 6520). They make a striking contrast. That's a red giant star visible on the upper edge of the nebula. 

Finally, (for now) let me show you three more dark nebulae in Sagittarius.

There's a lot in this image. I made it by taking 11 different exposures to produce this mosaic that covers about 1.3 degrees x 0.9 degrees. 

The amazingly dense field of stars seen here on the left half of the image forms Messier 24, the Sagittarius "Star Cloud."  

In the lower left you'll notice a trio of bright stars. The topmost of those is a red giant star. To the right of the red giant is a hot blue star that is vastly more luminous than our Sun. Above the red giant is the open star cluster known as NGC 6603. Near the center there's another little cluster of stars known as Collinder 469. To the right of Collinder 469 is the dark nebula known as Barnard 92. Up and left from Barnard 92 is the somewhat squid-shaped Barnard 93. In the upper left of the image is the smaller Barnard 307. Barnard 307 is one of the many dark nebulae in Barnard's catalog that were added to an expanded version to the catalog that was published in 1927, several years after his death. 

I've got more dark nebulae on my list. Hopefully in the not too distant future I'll post images of some of them here.

Long Distance Voyagers

The 1970s saw the amazing beginning of our explorations of the outer Solar System. Pioneer 10 launched in 1972. It became the first space probe to fly through the asteroid belt and past the giant planet Jupiter. About a year later Pioneer 11 was launched on a journey to both Jupiter and Saturn. The exploits of these two probes are forgotten by many but they paved the way for their successors, Voyager 1 and 2.

Voyager 1 flew past Jupiter and Saturn, while Voyager 2 visited these two gas giant planets and the ice giant planets of Uranus and Neptune.

Their flybys past these giant planets put the Pioneer and Voyager probes on trajectories that propelled them out of our Solar System and into interstellar space. The Pioneer probes functioned until the early 2000s. The Voyagers are still in operation and have been returning data on the region of space just beyond the influence of our Sun.

The four probes are completely invisible to our telescopes, but it is possible to look at where they are in the sky. I’ve spent some time this year looking at three of the four probes. Voyager 2 left the plane of the Solar System after its flyby with Neptune in 1989. As a result its position in the sky is too far south to be seen from my location on Earth.  

In late February I pointed my Unistellar eVscope at the location of the Pioneer 10 probe. It’s in the direction of the constellation of Taurus, the Bull, along one of the Bull’s horns At the time its distance from us was 127.7 times Earth’s distance from the Sun (127.7 astronomical units). That’s almost 12 billion miles. At that distance, if we could still receive radio messages from it, it would take almost 18 hours for them to cross the gulfs of space to reach Earth. That's 18 light hours. While that is quite far, keep in mind that the nearest star to the Solar System is more four light years away.

You can’t see Pioneer 10 in this image, but it is there, somewhere near the middle, alone and drifting outward as it will do forever.

Knowing exactly where to look is simplified by use of a planetarium program such as SkySafari Pro. Here’s how I used it to track down my next target, Voyager 1. It is in the huge constellation of Ophiuchus, near to its border with Hercules.  SkySafari Pro gives me its coordinates and a visual image of its location against the starry sky. Next I point my trusty eVscope to the coordinate and take an image. Remember, the probe itself is completely invisible, but for me just knowing that Voyager 1 is out there somewhere in that field of stars is enough for me to stop and wonder.

In the image above I've blinked my photograph with the SkySafari Pro finder chart which marks the location of  Voyager 1. 

How far is Voyager 1 from Earth? 153 astronomical units. That’s over 14 billion miles. Its feeble radio signals that reach back to Earth take more than 21 hours to get here. 

My final target isn’t as far away as Voyager 1, but it is in a more visually interesting position of the sky. Pioneer 11 is only 105 astronomical units from Earth. It is in the direction of the small constellation of Scutum, the Shield. More importantly it is just under 8 arc minutes (a minute of arc is 1/60 of a degree) from the globular star cluster known as NGC 6712. This means that if you ever observe the star cluster with a wide-field telescope there’s a good chance that you’ll also be seeing the location in the sky of Pioneer 11, and just maybe a photon or two of reflected light from the spacecraft. 

Pioneer 11 is somewhere near the middle of this image. The light of the stars in the cluster take more than 26,000 years to reach Earth while any reflected light off of Pioneer 11 takes 14.5 hours to reach Earth. 

Here's the finder chart from SkySafari pro marking its location in the sky.

 There’s one other object made by humans that is speeding out of the Solar System. That’s the New Horizons spacecraft which flew past dwarf planet Pluto in 2015 and then to the small Kuiper Belt Object known as Arrokoth three and a half years later. I haven’t targeted that region of the sky yet. Maybe I’ll do so sometime soon on a clear summer night.