April 16th, 2014

Blue Martian Sunset

The long-awaited moment when the Curiosity rover took some time away from science to admire the scenery is finally here. We are now able to enjoy the marvelous sunset on Mars.

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Martian sunset is remarkable because it is blue. The reason for this unusual color is the same as for red sunset on the Earth and is called Rayleigh scattering. There is a misconception that the blue sky on the Earth is due to the presence of oxygen in the air or even the ozone layer. In fact, the composition of the atmosphere here is less significant than its density. It is the gas density that leads to the scattering of white sunlight and coloring of the sky.

The difference between the color of the sky at noon and at sunset is in the volume of the atmosphere that sunlight travels through. Martian atmosphere is a hundred times thinner than on Earth, but when the Sun is near the horizon, the light overcomes a layer of atmosphere that is thirty times thicker than at noon.

 

 

Additional coloring of Martian sky is given by the dust that is constantly hanging in the atmosphere. Apparently it was that orange color plus the blue that gave the slightly greenish tint on the photo. Although, I have to say that the weather is quite clear, and this is the best visibility I have seen in all time of Curiosity working on Mars. For the first time we can see the stones on the hillside nearly 30 km away from the rover.

 

However, there is still a lot of dust in the sky. You can see how a mountain ridge gets lost in the haze.

 

At best, it is visible from 50 kilometers. Current clear sky explains why the top of the sunset panorama is almost black. When the Sun is at the zenith, it should be as black as the sky on the Moon or on the Earth at an altitude of 30 km and higher.

Observations made by Viking program show how the color of the sky changes depending on the amount of dust.

 

Let’s go back to the color of the sunset. Thanks to modern technology, we can see the dawn from space. You can clearly see the orange color of the clouds on the border of the day and night on the last image from Electro-L.

 

Looking at Mars with the Hubble telescope, we can similarly see a blue band that encircles Mars at the edge of the illuminated disk.

 

Interestingly enough, that blue band is not always visible on shots of Mars. Apparently the reason for that is in the seasonal variations of the atmospheric density. Depending on time of the year, the reserves of the Martian ‘air’ may fall to 1 /150 of the Earth’s reserves. The rest freezes to the state of dry ice at the poles.

Curiosity had already taken a few shots of sunset on Mars, but did it in black and white with its navigational camera. I had to borrow the colors from another shot made by Spirit for this video, but in the end I think it turned out ok.

 

 

The blue sky doesn’t come as much of a surprise to us. But what is really incredible, it’s the blue setting Sun. As we know from our experience on the Earth, at dawn both the sky and the disk of the Sun change color.

 

Unfortunately, Curiosity does not risk taking images of the Sun directly, so as not to damage the camera matrix, but it was able to capture the solar flare, which was blue.

 

Post by zelenyikot.


April 14th, 2014

April 15 Total Lunar Eclipse

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A total lunar eclipse will take place on April 15, 2014. It will be the first lunar eclipse this year. A lunar eclipse occurs when the moon passes within Earth’s umbra (shadow). As the eclipse begins, the Earth’s shadow first darkens the moon slightly. Then, the shadow begins to “cover” part of the moon, turning it a dark red-brown color (typically – the color can vary based on atmospheric conditions).

On April 15, 2014, the moon will pass through the southern part of the Earth’s umbral shadow. It will be visible over most of the Western Hemisphere including east Australia, New Zealand, the Pacific ocean, and North and South America. In the western Pacific, the first half of the eclipse will occur before moonrise. In Europe and Africa, the eclipse will begin just before moonset.

Image Credit: NASA/JPL-Caltech.


April 11th, 2014

Stargazing Notes: Catch Venus Passing Neptune

 

One of the closest planet-planet conjunctions of 2014 is happening this Saturday, Apr 12th, when Venus and Neptune will come just 40 arc minutes apart, which is a little larger than the apparent size of a full Moon.

 

solar walk iphone app

From the US, you should be able to spot Venus early in the morning,  looking to the East, shining at magnitude -3.8. Neptune is 30,000 times fainter than Venus, so you may want to bring out a telescope.

 

star walk iphone

Star Walk will help you find them in the night sky.


April 9th, 2014

Your work in Star Walk app

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If you want to have your astronomy picture appear in Star Walk app, follow these guidelines:
1. Choose a name for your picture.
2. Write a small paragraph about the celestial object on your picture (its peculiarities,
details).
3. Write your full name and link to your website (if any) for credit.
4. Make sure your picture is at least 2048×1536 and send it to apod@vitotechnology.com.


April 3rd, 2014

Stargazing Notes for Tonight

The Moon is still Waxing Crescent so this is a great opportunity to see the fainter objects in the sky. An interesting sight for tonight is Aldebaran, the brightest star in the constellation of Taurus, the bull. This star takes the position of the bull’s eye, and is gazing upon the Moon at sunset. Aldebaran is an orange giant, one of the brightest stars on the nights sky, located 65 ly away from us. It is 44 times larger than the Sun in diameter and it shines with 425 times the Sun’s luminosity so we can still see it from the Earth.

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Star Walk will help you spot Aldebaran and find your way across the sky.

 

Important announcement: We are now available on Windows Phone devices, so make sure to shoot an email to your Windows Phoning friends and let them know they are very welcome in our stargazing community.