Update: Second date of views (4 Jan 2019) is at the bottom of this post.
The largest asteroid Ceres has been orbited by the ion-engine powered DAWN spacecraft since early 2015. DAWN ran out of fuel to maneuver in October 2018 and will remain silent in orbit at Ceres for decades. Previous to Ceres, it visited the second largest asteroid Vesta. This fly-over video gives a close view of Ceres.
The asteroid is far away and quite small and dim. It is not something most people have ever seen with the naked eye or in a telescope. I’ve been tracking Ceres with desktop planetarium software with hopes to see it. I am happy to report success.
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The New Horizons spacecraft was launched in January 2006. It coasted by Pluto 14 July 2015 giving us our first close views of the dwarf planet and its moons. Previous posts highlighting events of the mission are found here.
After that flyby of Pluto, the mission gained a new challenge. It is headed for a flyby of a Kuiper Belt object called Ultima Thule. The flyby occurs late on New Year’s Eve about 11:30 pm CST. The closest approach distance will be about 2200 mi (3540 km) which is 1/3 the distance it was in the flyby of Pluto. I invite you to read remarks by Principal Investigator Alan Stern as New Horizons makes its final approach. Quoting Stern:
“What will Ultima reveal? No one knows. To me, that is what’s most exciting—this is pure exploration and fundamental science!”
From the New Horizons web site:
We will only know what Ultima Thule’s surface looks like once New Horizons has sent back the first pictures after it has flown by, although based on observations of similar-sized Solar System objects, it will almost certainly display impact craters. The lighting environment at its surface is very dim, as it receives only about 0.05% of the light from the Sun that Earth does. We do know that Ultima Thule has a reddish color, probably caused by exposure of hydrocarbons to sunlight over billions of years. The flyby will also reveal whether it has any moons, or even a ring system. Ultima Thule belongs to a class of Kuiper belt objects called the “cold classicals”, which have nearly circular orbits with low inclinations to the solar plane, and which have not been perturbed since their formation perhaps 4.6 billion years ago. Ultima Thule will therefore be the most primitive planetary object yet explored, and will reveal to us what conditions were like in this distant part of the Solar System as it condensed from the solar nebula.
I will be monitoring the progress of New Horizons at this site for the latest update news and images.
Movement of Vesta and Saturn
I posted recently about my first view of the protoplanet and 2nd largest asteroid 4 Vesta. Later, on 23 Aug 2018, I managed to get an image of dim Vesta. With a magnitude of +6.5 at this time, it is not quite visible to my naked eye even under the best viewing conditions. It does show in binoculars. For comparison, Jupiter and Mars now have magnitudes of -1.8, and -1.2 respectively. They are bright. Here is a table of magnitudes of other objects.
At about 8 pm on 23 Sep, 26 Sep, and 4 Oct, the sky was dark with good seeing. Saturn was in a pattern of stars I could easily see. I knew Vesta was somewhere below Saturn. Below is the broad view using desktop software. South and southwest are labeled along the horizon at the bottom. Scorpius is at lower right. Sagittarius is in the center. The 2nd image is the zoomed-in view of the box in the center. Click for more detail.
Discussion in a previous post centered on getting to space and into an orbit near Earth. This post is about how spacecraft return from orbit. Some returns are under control and some are not.
Launch to orbit requires giving a spacecraft a large amount of kinetic energy of motion (KE) and a large amount of gravitational energy (PE) due to its altitude. The large amount of work done to gain those energies comes from the potential energy released by an engine(s) as fuel burns. Once in orbit with engine(s) off, the total of those two energies (KE+PE) stays constant except for the small decrease due to the small atmospheric drag at high altitudes. If the orbit is a circle the two energy quantities are unchanging.
If the orbit is an eccentric ellipse, the quantities do change but not their total. The next graphic shows an eccentric orbit of an Earth satellite. When it passes closest to Earth (perigee), the KE is at its maximum value and the PE is at its minimum. Font size was changed to illustrate their inequality. When at its farthest point in orbit (apogee), it is going slowest with minimum KE and is at its highest altitude with maximum PE.
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Take a time-out from the news of the day or your busy routine. Tour some of the interesting features of our Moon as presented by the NASA Goddard Space Flight Center/David Ladd. Best viewed in HD by using the gear button at the bottom right of the video window.
The concepts are simple to place a satellite or a manned space capsule into orbit near the Earth. But, they are very difficult to achieve.
- Engines must exert a lot more upward force than the downward force of the weight of the fueled rocket.
- After lift-off, gradually point the rocket more horizontally as it moves faster.
- Jettison the empty 1st stage. The 2nd stage engine(s) continues to speed up the payload horizontally.
- Shut down the engine(s) to allow the payload to coast in circular orbit when at altitude of about 120 miles (~200 km) and speed of about 17,500 mph (~ 28,200 kph).
The orbit drawn here to scale in yellow allows the spacecraft to coast for some time above most of the atmosphere. But it will not coast forever. The thin atmosphere will gradually bring it down.
Earth image from NASA
The U.S. started launching rockets from Cape Canaveral Florida in 1950. The European Space Agency launches from Guiana Space Centre northwest of Kourou in French Guiana. France established that space port in 1964. Each site has open water to the east avoiding the danger to populated areas. Each site uses the speed boost from the eastward rotation of the Earth to assist launch speeds. Guiana is near the equator and moves east about 1000 mph. Cape Canaveral moves east over 900 mph. With the better technologies today, rockets can be launched to orbit from about anywhere and in non-east directions such as for polar orbits.
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The sun’s output in the visible spectrum peaks around yellow. Our eyes are most sensitive to that part of the visible spectrum. The sun also radiates in a broad range of other wavelengths invisible to our eyes. Each comes from dynamics taking place on the surface and in the atmosphere of the sun.
I’ve written about NASA’s Solar Dynamics Observatory (SDO) earlier in a previous post. SDO observes and images the sun several times a minute at ten different wavelengths to give a more complete picture of the activity at and near the surface. A description of those wavelengths is available here. I used the images from the SDO site to render this image of the sun at those ten wavelengths. The yellow center represents the sun’s surface. Each ring of color is at a higher altitude and temperature in the atmosphere of the sun.
Original images used from: NASA/GSFC/Solar Dynamics Observatory
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