Summer's Greatest Hits

Well, it's Labor Day. Summer is officially over and the fall semester has begun. I got in a lot of telescope time over the summer, so I thought I would post a few of my favorite images taken during my break.

Comet 3I/ATLAS, the third ever interstellar object known to pass through our Solar System was discovered in early July. It is faint, but the Unistellar / SETI Institute citizen science program was interested in seeing if people could detect it with their telescopes. 

 

The image above shows 3I/ATLAS (circled). The individual frames were aligned on the comet, which means that the stars in the image appear as streaks. At that time the comet was about 17th magnitude, (translation: very faint!) but detectable. I am happy to be contributing to the science being collected on this mysterious visitor which, despite some claims, is indeed just a comet.

Of course, I continue to image some celestial objects just because they look pretty. Probably my favorite of the summer was this beautiful mix of stars, gas and dust known as the Elephant Trunk Nebula. 

It is located some 2,400 light years away in the direction of the constellation of Cepheus, the King. Like many nebulae, it is a region of space where new stars are forming. This was a 2-hour exposure taken with my Celestron Origin telescope. I honestly never imagined that I would someday be able to take images like this one and the others below, but I am happy to be living in the age of the smart telescope.

Much farther afield is the spiral galaxy known as Messier 33.

This is a 2-hour exposure of M33 which, at a distance of 2.7 million light years, is the second closest spiral galaxy to our Milky Way Galaxy. It is a galaxy that always challenged me when I tried to see it visually with a traditional telescope, so being able to capture it this way is wonderful.

Earlier in the summer I posted images of other nebulae, one of which was the fabulous Lagoon Nebula in Sagittarius. After further review, I thought that maybe the image I posted there, which was a 1-hour exposure, was perhaps overexposed. So, I decided to try something much shorter and I am even happier with the result. 

This image was just a 2-minute exposure! Even with this short exposure the nebula still reveals brilliant color, dark globules of dust and the young star cluster that has formed from the nebula.  

Just last night I pointed my Origin telescope at NGC 6729, a target that was new to me. It is located so far south that it never gets even 20-degrees above my horizon. Still, I managed to get a 70-minute exposure and am happy with how it came out. 

What you are seeing here are some stars that are embedded within opaque clouds of gas and just. A pair of bright, young stars are shining forth just above center while other fainter ones struggle to be seen at all. The nebula very much reminds me of the much more famous Messier 78.

At practically the other end of the sky is the more famous Bubble Nebula (NGC 7635):

The bubble at the center of the image is not a thin film of soapy water but rather of gas that has been blown off a massive supergiant star located thousands of light years away in the direction of the constellation of Cassiopeia, the Queen. Some day this star will explode forming a supernova.

Ten to twenty thousand of years ago there was a supernova explosion in the constellation of Cygnus, the Swan. It produced the Veil Nebula (a part of which is in my nebula post linked above), which is just a piece of the much larger supernova remnant known as the Cygnus Loop. 

The Cygnus Loop is about five full moons across, which means it is much, much larger than the field of view in my Origin telescope. Yet, I decided I wanted to capture it all. To do so I had to make a mosaic of 15 images. Here it is:

To me, it resembles a bubble that has just burst, but it is an expanding cloud of 'star guts' from the supernova explosion. 

I mentioned the size of the nebula above, but wanted to illustrate that with a correctly scaled image of the full Moon, so here it is: 

These were just a few of the many objects observed this summer. There's a whole lot of sky still to observe and I'll be back later with more.

A Supernova and Two Comets

We've had a wet and rainy winter and early spring. That gave way to an intense "May Gray" and a solid "June Gloom" during the first half of this month, so there hasn't been much time for astronomy this year. 

Thankfully, I had a short and fortuitous break in the clouds early in the evening of May 20th. Just one day earlier a new supernova had been discovered in M101, the Pinwheel Galaxy. I had imaged the Pinwheel last year, so I had an appropriate image to blink with the new one to show the appearance of the supernova.

That's the supernova blinking on and off on the right side of the galaxy. It is a Type II supernova, which marks the collapse and explosion of a massive star. M101 is located 21 million light years from our Milky Way Galaxy, meaning that the star exploded 21 million years ago and its light has only now just reached us. 

The rest of May remained cloudy and I wasn't able to see it again until June 15th. It's still visible. This type of supernova stays bright for many weeks, so it will be quite some time before it fades completely away.

Two faint comets have captured my attention recently. One of this is known as C/2023 E1 (ATLAS).

E1 ATLAS is a short period comet, with an orbit of 85 years. It is currently in the inner Solar System and crossing the orbit of Venus, but if you look at its orbit from the side (below) you can see that it is highly inclined (tipped) relative to the orbits of the planets.

It is a relatively faint comet, but has had an outburst recently which has made it an interesting target to observe. Below I have animated two images of the comet to show its motion against the background of the stars:

I captured the all  of images here with my Unistellar eVscope, which nicely reveals the comet's blue-green color. 

I recently targeted an even fainter comet, that *may*, in the fall of 2024, become one that will be very bright. It is known as Comet C/2023 A3 (Tsuchinshan–ATLAS). 

Here's where it currently is:

Yes, it is out past the orbit of Jupiter. Usually comets aren't observed until they get much closer to the Sun. Since A3 is at a much greater distance from the Sun than where comets can normally be observed that means that is it brighter than normal, which might mean that is will become a spectacular, dare I say, Great Comet --but not until it gets closer to both the Sun and Earth and that will not happen until the fall of 2024. 

However, it is faintly observable with a telescope right now. It's small and faint so I cropped and annotated the image so that it could be seen here:

That little dot is chunk of ice that is coming in from the Oort cloud and in about 16 months it will make a pass through the inner Solar System. As it gets closer to the Sun heating will vaporize parts of the comet which likely will give the comet a temporary atmosphere (known as a coma) and a tail or two. If it follows expectations the comet will become brighter than Venus and be easily seen without any optical aide, but comets are famously unpredictable, so only time will tell how it will really look. In the meantime, I'll be looking at it as often as I can.

Things That Go Bang in the Night

White dwarfs are hot glowing remnants of stars that were at least somewhat like the Sun. Over billions of years of time isolated white dwarfs gradually cool down (possibly crystalizing into Earth-sized diamonds!) and fade away. But white dwarfs that are located in binary star systems can have a much more spectacular time than just gradually dimming from view. 

Artist's illustration of a white dwarf (right) pulling gas from its companion star. Credit: NASA/CXC/M.Weiss

 

In some of these binary systems hydrogen gas is pulled off of the white dwarf's companion star which piles up on the surface of the white dwarf. Eventually there's enough gas there that it detonates producing a nuclear explosion on the surface of the white dwarf. This is what astronomers call a nova. 

The nova explosion does not destroy either star and can eventually repeat. There are 10 of these recurring novae that have been observed to repeat in our Milky Way galaxy. 

One of these recurring novae is known as U Scorpii (U Sco for short). Normally U Sco is too faint to observe with my Unistellar eVscope, but it is an easy target when a nova outburst occurs. On June 6th I got word that U Sco had an eruption underway so I decided to take a look. 

U Scorpii (bright star at center)

One characteristic of this nova is that it fades in brightness very rapidly. To record its fade I have been looking at it periodically since June 6th. Sure enough, it will soon be back to its normal too-faint-for-me-to-see status. The image below shows U Sco dropping in brightness by a factor of 100 in just 10 days. 

The nova is still dropping in brightness and will soon fade from my view entirely. 

A second type of explosion involving white dwarfs is known as a Type Ia supernova. This is a much bigger deal. Again we are talking about white dwarfs in binary star systems, only instead of an explosion on the surface of the star, the entire thing blows apart, most likely from the merger of two white dwarfs (although, maybe not - astronomers are working on that). 

These explosions are big enough for my little telescope to be able to see them from distances of tens of  millions of light years (whereas U Sco is just ~60,000 light years away). 

Last year I was able to observe one of these explosions, supernova 2021hiz, in an obscure galaxy known as IC 3322A. I followed up my observation a year later to produce this comparison showing the galaxy with and without the supernova:

The galaxy is just a faint smudge of a line (it's a spiral galaxy seen from the side) and the supernova is the bright dot on the upper edge that blinks on and off. Notice that the light of the supernova is actually brighter than the rest of the entire galaxy. 

Think about that. One supernova explosion can outshine all the light produced by hundreds of millions of stars. That's amazing.

Another bright Type Ia supernova (sn 2022hrs) took place this spring in a galaxy known as NGC 4647. NGC 4647 is conveniently in the sky next to one of the galaxies in the Messier Catalog, M60. Last year I photographed all of the objects in the Messier Catalog, which means that I had a before image to go with the new image of the supernova. 

Here's the before and during comparison:

This supernova exploded some 63 million years ago and light from it arrived on Earth in mid April 2022. I am happy to have had the opportunity to catch it. 

By the way, the last supernova observed in our Milky Way galaxy was also a Type Ia supernova. It was recorded by Johannes Kepler back in the year 1604.