Browsing the Hubble Legacy Archive, I was intrigued by a small ring shaped nebula NGC 6369. It is also known as the Little Ghost. Discovered by 18th century astronomer Sir William Herschel, it lies over 2000 lt-yrs away in the constellation Ophiucus. The sun-like star at the center explosively blasted away its outer layers creating the ring of glowing gases. The star radiates strongly in ultraviolet causing the glow of the nebula. The blast also reduced the star to a white dwarf. For this color image, I combined three blue, green, and red filtered grey-scale Hubble images. The colors illustrate the presence of ionized oxygen, hydrogen, and nitrogen atoms.
Fellow amateur astronomer Roger captured an image of his own recently of a different ring-shaped nebula NGC 7293 in his southern hemisphere sky. It is published here in his blog Cosmic Focus.
Astronomy fans are likely familiar with Messier 57 high in the summer sky of the northern hemisphere. It is another fine example of a ring nebula. Follow the link for a beautiful image and description.
Much of the excitement has settled now that Mars 2020 Perseverance Rover is safely on the surface of Mars after the 18 Feb 2021 landing. I gathered images and links to a collection of things I feel tell the story of this rover in a not too complicated way. The mission is very challenging. A primary goal is to find evidence that microbial life may have existed on the Martian surface in the past.
You might wonder where Perseverance landed and why is that place is important. Landing took place in Jezero Crater. The crater is about 49 km (30 mi) across. It is believed to have once been filled with water. This image shows a dried riverbed and delta of a water source that once flowed left-to-right and filled the crater. The colors are indicators of various types of mineral deposits and not actual colors. The rover landed in the lower right quadrant of this image just below the two side-by-side small craters on the flat plain and not far from the delta formation.
Ancient river delta into Jezero Crater | MRO | NASA
Scientists and space enthusiasts are excited about the upcoming landing of the exploration rover Perseverance on the surface of Mars on 18 Feb 2021. The NASA-TV broadcast from Mission Control starts at 11:15 am PST/2:15 pm EST.
The mission is designed to look for bio-signatures in a river delta of an ancient lakebed. It will harvest rock-core samples for analysis and possible return to Earth in a future mission. The rover will be joined by a small helicopter to extend its vision and reach around the area. This video (< 3 min) shows the basics of the rover design and plans for the mission. You are invited to explore more about the mission at this link.
Perseverance helicopter being examined by NASA engineers
Perseverance was launched in July of 2020. It took 7 months to coast to this meeting with Mars. On a collision course, it will enter the thin atmosphere at over 12,000 mph. The challenge is how to safely slow the vehicle and land it. This following graphic illustrates the overall plan, but not to scale.
The fast-moving craft in coast phase enters the atmosphere at upper left. A heat shield protects it and slows it down from 12,000 to 950 mph. A parachute deploys and the heat shield falls away. The craft scans the terrain to find the landing site.
At 180 mph and 1.3 miles altitude, the parachute is detached letting the vehicle fall. Rocket engines control the descent and slow it down to less than 2 mph and 60 ft. above the surface. The rover is lowered about 20 ft more by cables to touchdown on the surface. The cables detach and the rocket assembly flies far out of the way.
Lowering of rover by cables for touchdown | NASA
The technique has been done before in 2012 when the Curiosity rover landed on Mars. It was described then as 7 minutes of terror. Mars is far from Earth. By the time radio signals reach us more than 11 minutes later, events will already have played out, successfully or not. All actions are programmed. Curiosity is still functioning well on Mars today. Here is a recent selfie.
What will the Moon look like on any date in 2021? What will it look like on your birthday? Find out at NASA Dial-a-Moon. The example pictured below is for 16 January 2021. Set dates and see views for northern hemisphere and for southern hemisphere readers by following either link. Enter any month and day to see a high definition image. You may leave the universal time (UT) at the default value. If you wish, your local-to-Universal time conversion can be done at this link. Or, type ‘universal time’ into Google. Go back to Dial-a-Moon to enter the UT.
After visiting Dial-a-Moon, scan down that web page for a wealth of additional information about the Moon’s motions and appearance. The images of Dial-a-Moon are made from those of the Lunar Reconnaissance Orbiter (LRO) in low altitude orbit around the Moon since 2009.