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.

Exoplanets!

 I did a lot of citizen science observations during my sabbatical last fall. I was especially interested in trying to use my time to make observations of exoplanets.

My exoplanet observations were all made using the transit method. These planets are impossible to see directly but they can still be detected. As an orbiting exoplanet passes directly in front of (transits) across the face of its star it makes a mini-eclipse and blocks a small percentage of the star’s light. This can be measured even with small telescopes, making this technique the most successful method for studying exoplanets. A typical exoplanet observation lasts from four to five hours, though some are shorter, and others are longer.

Over the course of the semester, I attempted to observe sixteen exoplanet transits. Due a variety of factors (weather, equipment failure, etc.), not all of them were successful. All of my observations were made with a Unistellar eVscope2. A summary of my exoplanet observations is included below along with other findings about these exoplanets.

A note about exoplanet names. Most of them are terrible acronyms of the survey the first discovered the exoplanet, followed by a letter, which indicates the order of discovery within that particular system (starting with the letter b). As an example WASP stands for Wide Angle Search for Planets. WASP-33b refers to the first planet (b) within the 33^rd system discovered by that survey. Some exoplanet names are acronyms within acronyms. TOI is TESS Object of Interest. TESS is the Transiting Exoplanet Survey Satellite.

XO-7b               Observed August 23/24, 2024 & October 5-6, 2024

A graph of the science results is generated for each exoplanet observation. The graph for one of my two observations of XO-7b is above. Note that the dates are given in Universal Time (essentially, the time in Greenwich, England) which is why these graphs don’t always agree with the local date.

XO-7b is a gas giant planet that orbits a spectral type F star that is larger and hotter than the Sun. It is located 764 light-years from Earth in the constellation of Draco, the Dragon. It is an example of a “hot Jupiter” type planet, as are the majority of exoplanets that can be observed with a small telescope. It is located very close to its parent star, at a distance that is just 4.421% of the distance Earth is from the Sun. It orbits its parent star every 2.9 Earth days! The planet is smaller than in mass (0.709 times Jupiter’s mass or 225 times Earth’s mass), but larger than Jupiter in size. Its larger size is because the tremendous heat that it receives from its star essentially inflates the planet giving it a radius that is almost 1.4 times that of Jupiter’s. The calculated temperature for the planet is 2,678^oF. 

TOI-1518b                     Observed August 27/28, 2024

Note: there were clouds at the end of the observation.

TOI-1518b is a gas giant planet that orbits a rapidly rotating F-type star, which is larger than the Sun (1.95 times the Sun’s radius) and 2,750^oF hotter than the Sun’s surface temperature. It is located 737 light-years from Earth in the constellation of Cepheus, the King. The planet has a mass 2.3 times that of Jupiter and a radius that is 1.9 times that of Jupiter. More massive gas planets tend to be smaller as the extra mass causes more compression from gravity. The fact that TOI-1518b is so large indicates that it is inflated due to the temperature caused by how close it is to its star. It orbits its star every 1.9 days in an orbit that is just 3.89% the size of the Earth-Sun distance. The planet is considered to be an ‘ultra-hot’ Jupiter. Its dayside temperature has been measured to be 5,367 ^oF! It is believed to have ionized iron vapor in its atmosphere.

TOI-1259 Ab                 Observed September 24/25, 2024

The TOI-1259 is a binary star system. The system is located 385 light years from Earth in the direction of the constellation of Draco, the Dragon. TOI-1259 A is a spectral type K star that has a radius 71% of the Sun’s and is about 2,000^oF cooler than the Sun. The other star, TOI-1259 B, is a white dwarf. The white dwarf is a distant companion, being 1648 times farther from A than the distance between Earth and the Sun. White dwarfs are essentially dead stars. In this case TOI-1259 B would have begun as a star that was more massive than A (1.59 times the mass of the Sun) and burned through its hydrogen fuel at a faster rate. It now has a mass of 0.56 times the mass of the Sun. Astronomers have determined the age of the white dwarf, and thus the age of the system, which is thought to be 4.8 billion years (Our solar system is 4.6 billion years old.).

The exoplanet is named TOI-1259 Ab. It is a gas giant planet with a mass is 0.44 of Jupiter’s but it is slightly larger than Jupiter in size (1.02x Jupiter’s radius). It orbits star A every 3.5 days at a distance of 4.07% of the Earth-Sun distance.

Observations at Palomar and Keck suggest that the planet receives extreme heating on its dayside which is both causing some of its atmosphere to escape to space and also driving extreme winds that blow from the dayside to the night side of the planet. The equilibrium temperature of the planet is estimated to be 1,190 ^oF. 

WASP-33b                    Observed September 25/26, 2024

WASP-33b is a gas giant exoplanet 398 light years in the direction of the constellation of Andromeda. It orbits a variable star which is larger (1.5 times the Sun’s radius) and nearly 3,000^oF hotter than the Sun. It orbits the star every 1.2 Earth days (!) at a distance that is just 2.39% of the distance between the Earth and Sun. Unlike most planets, WASP-33b has a retrograde orbit, meaning that it does not revolve in the same direction that its star rotates. It has a mass that twice that of Jupiter and is about 1.9 Jupiters in radius. The temperature of the exoplanet is 5,790^oF. Researchers using the Hubble Space Telescope have detected titanium oxide, a major component of sunscreen, in the atmosphere of this planet. Iron and silicon have also been detected in its atmosphere.

WASP-2b                      Observed September 27, 2024

WASP-2b is a hot Jupiter-type gas giant planet that orbits a K-type star located 500 light years from Earth in the direction of the constellation of Delphinus, the Dolphin. The planet’s host star has a mass that is 85% of the Sun’s, it is 82% of the Sun’s radius. It is 1,154^oF cooler than the Sun. The planet has an orbital period of 2.2 Earth days at a distance that is just 3.1% of the distance between the Earth and Sun. Its mass is 93.1% of Jupiter’s and it is slightly larger than Jupiter in size. The planet has a density similar to that of water. The temperature of the exoplanet is 1,855^oF. Spectroscopic observations suggest that it has a cloudy atmosphere. 

WASP-93b                    Observed September 28/29, 2024

WASP-93b is a hot Jupiter-type gas giant planet that orbits an F-type star located 1,208 light years from Earth in the direction of the constellation of Cassiopeia, the Queen. This star is both larger and hotter than the Sun.

The planet has an orbital period of 2.7 Earth days and orbits at a distance that is just 4.2% of the Earth-Sun distance. It has 1.47 times Jupiter’s mass and is 1.7 times Jupiter’s radius.  The planet’s equilibrium temperature is estimated to be 3,000^oF.

HAT-P-32b                    Observed October 4/5, 2024

HAT-P-32b is a gas giant planet that orbits a type F star located 943 lights from Earth in the direction of the constellation of Andromeda, the Princess. The planet has a mass that is just 68% that of Jupiter. It orbits its star at a distance that is just 3.3% of Earth’s distance from the Sun. Its close distance to its star has inflated the size of the planet making it nearly twice Jupiter’s radius. This in turn means that the planet has a low density. All of the “hot Jupiters” observed so far have densities lower than water’s 1 g/cm³, meaning that they are made of light materials (in our Solar System only Saturn, which has a density of 0.69 g/cm³ has density lower than water). HAT-P-32b has a density of just 0.1085 g/cm³  this is low enough to almost put it into the category of “super-puff” (yes, that’s a real thing) exoplanets, which have densities less than 0.1 g/cm³.

TIC 362220946.01     Observed October 10/11, 2024

TIC 362220946.01 is a possible exoplanet that was first observed by NASA’s TESS satellite. It was thought that this planet has an orbital period of 8 days and a mass that is 23 times that of Jupiter. I was one of nine observers from the U.S. and Mexico who looked this system in an attempt to confirm its existence and the possible orbital period of the planet. The results were inconclusive but there are suggestions that this could perhaps be a binary star system instead of a planetary system. Further observations may help to solve this puzzle.

WASP-77 Ab                Observed October 24/25, 2024

WASP-77 Ab is another “hot Jupiter” type gas giant planet. It is located 343 light years from Earth and orbits a Sun-like star in the constellation of Cetus, the Whale. The star is part of a wide binary system, where the other star is a spectral type K star that is smaller and cooler than the Sun.  has a mass 1.67 times that of Jupiter and is 1.23 times Jupiter’s radius. It orbits its star every 1.4 Earth days at a distance of 2.3% that of the Earth-Sun distance. The planet has a calculated temperature of just over 2,600^oF.

TOI 6881.01                 Observed October 31, 2024

The exoplanet known as TOI 6881.01 orbits a star that is 2,559 light years from Earth in the direction of the constellation of Perseus, the Hero. Its star is larger, hotter and more massive than the Sun. The planet orbits its star every 1.9769 days. The planet has a calculated equilibrium temperature of almost 3,100^oF. The planet has a mass that is essentially the same a Jupiter’s and a radius 1.44 times that of Jupiter, making it another “hot Jupiter” gas planet that has expanded from the extreme heat from being right next to its star.

TOI-5571.01                 Observed December 4, 2024 & December 18, 2024

TOI-5571.01 was initially detected by NASA’s TESS satellite, but its observations were widely spaced in time and so the orbital elements of this exoplanet were highly uncertain. Early observations suggested that the exoplanet could have an orbital period of 731 days (2 years) but was more likely to be something shorter. My observation was part of a campaign by Unistellar to help pin down the exact orbital period of the planet. My observations the night of December 4 (my birthday!) did seem to catch the exoplanet transiting in front of its star (though it was low in the sky), which may indicate that the planet’s orbital period is potentially 66 days, but further observations are needed. 

Disco Sunspots!

 Back in October I posted about using a disco ball to observe a solar eclipse. It turns out that you can also use a disco ball to safely observe sunspots too. Here's how I did so earlier today.

Really all you need is a disco ball, a place to secure it in the sunlight and a shadowed area to project the image of the Sun. Here I have my disco ball sitting on a tripod for a Unistellar telescope. I aligned the disco ball so that it reflected an image of the Sun into my house and nearly 70 feet down a dark hallway on to a sheet of white paper. Here's the result:

It's not a great image, but you should notice a definite gray smudge-like area on the projected image of the Sun. That's a big sunspot that is visible on the Sun today. I also imaged the Sun with a Unistellar Odyssey Pro telescope and solar filter. I got this image which I rotated to match the orientation of the projected image above.

As you can see, that's the same sunspot group in both images. This is another confirmation that a disco ball is an excellent tool for safely observing the Sun.

Jupiter's Moons: Himalia, Elara and Pasiphae Too

It's no secret that I like to use my Unistellar telescopes to track down obscure things and to create animations of them moving in the sky. Back in August I managed to track down Saturn's faint moon Phoebe (on my blog here). 

Now that Jupiter is in opposition its time once again for me to take a look at it and some of its family of moons. The four Galilean moons are bright and easy to see with any optical magnification - even binoculars will work if you can hold them steady enough. 

Here's a shot of them taken in late October when Jupiter was also near enough to a background star that was almost as bright as one of the moons.

Jupiter has 96 (!) known natural satellites, but most people only ever see the four pictured above. Back in 2021 (when there were only 80 known moons of Jupiter) I first blogged about trying to extend my view to include Jupiter's moon Himalia. I found it, but wasn't very happy with my results, so I revisited finding that moon again last year (on my blog here) and now that I have just seen it again, I suppose that it has become an annual thing for me.

The animated gif below is from two images taken 58 minutes apart on 9 November 2023. Himalia can be seen moving pretty close to dead center and the glow of Jupiter is on the left. I circled it to make it easier to see.

That worked out pretty well. Well enough that I wondered if there were any other Jovian moons that I might be able to catch. 

Moons like Amalthea are bright enough, but far too close to the glare of Jupiter for me to ever be able to see. Some of them are just too small and faint, but Elara is just bright enough and far enough from Jupiter for me to be able to photograph it with my 4.5" telescope.

Elara and Himalia are in the same group (the Himalia group) of Jovian irregular satellites. With a diameter of 105.6 miles Himalia is larger than tiny Elara, which is just 53 miles across. As you can see from the graphic above (which I created using the SkySafari app), Elara is a bit farther away from Jupiter. It takes 260 days (8 1/2 months!) for it to complete an orbit around Jupiter. Himalia orbits just a bit faster, swinging around Jupiter ever 251 days (That's still a long time.).

I was a little worried because I had some cirrus clouds in the way and SkySafari (by far my favorite astronomy app) doesn't always have the best coordinates for these faint irregular moons. I pointed my telescope at the position listed and saw this:

There's a moving object in the lower right corner which at first I thought was Jupiter's satellite Elara. It was only later (after I put up an earlier version of this post) that I realized that I hadn't checked to see if there were any known asteroids in the area. Sure enough, that's the asteroid known as (933) Moultona.

Well, rats. What I needed was more accurate coordinates. Thankfully, JPL's Horizons System is an easy resource for getting accurate coordinates for small solar system objects.

I pointed my 4.5" telescope at the right place and gave it another shot. Was I able to spot a moon that's just 53 miles across from a distance of over 376 million miles?  Yes, though the glare from Jupiter was far worse than it was for Himalia (and strangely red too).

It's pretty tough to spot in the full frame, so I have posted a cropped animated gif version with Elara in a circle.

According to JPL's Horizons System Elara has an apparent magnitude of 16.625, just over half a magnitude fainter than what SkySafari listed. There's one other irregular satellite of Jupiter that is near to that magnitude: Pasiphae, with a magnitude of 16.877, it's only a bit fainter than Elara. With a diameter of 36 miles it is smaller but, thankfully, it is also farther away from the glare of Jupiter. In fact it is a lot farther from Jupiter. 

Here it is: 

Pasiphae has a retrograde orbit (meaning it orbits backward relative to the orbits of all of Jupiter's regular moons) that takes 764 days to complete. Yes, it takes just over two Earth years to circle Jupiter! Since Pasiphae and even Elara and Himalia take so very long to circle Jupiter, what we are seeing here isn't much of any of their orbital motions. Instead, most of their motion in the sky is because Earth itself is a moving object. During the hour or sow between images Earth moved much more in its orbit around the Sun than Jupiter and its family of moons did, allowing them to be seen against the much further background stars.

Solar Eclipse!

On October 14, 2023 along a line from Oregon through Texas there was an annular eclipse. The rest of the continental U.S. got to see a nice partial solar eclipse. 

I observed the partial eclipse along with about 50 others at Palomar College where I teach astronomy.

The eclipse crowd at Palomar College (that's my shadow in front)

As you can see from the photo above we had perfect weather and the eclipse did not disappoint. 

Here's a photo taken when the Moon had maximum coverage over the Sun from our vantage point:

Image captured using a Unistellar eQuinox 2 telescope

Thanks to the dedication of Palomar student Tomas Chester we were able to capture a time-lapse video of the entire event. Here's what it looked like: 

About two weeks before the eclipse I learned of a very cool outreach tool that helps to make eclipse viewing safe and fun - a disco ball. (See the paper: Why every observatory needs a disco ball). I immediately purchased a disco ball and set it up on the day of the event.

Above left is a standard disco ball. Each of the mirrors acts like a pinhole camera and reflects an image of the sun. The image on the right shows many images of the partially eclipsed Sun projected by the disco ball during the eclipse. It was very popular with our crowd and gave an almost magical view of the event. I highly recommend using a disco ball for every eclipse outreach event.

This eclipse was sort of a preview for an even better one - a total solar eclipse that will take place on April 8, 2024. Weather permitting it will be visible along a path from Mexico, up through central Texas and up toward the northeast U.S. and into Canada. I plan on observing that one and I will bring my disco ball with me.