Stargazing Live announcement
The first episode of the fourth series of Stargazing Live with Brian Cox and Dara O’Briain will air on Tuesday (7th Jan) at 8pm, on BBC 2. See the boys chat to fabulous scientists in Hawaii, NASA HQ and in the air over the Northern Lights while they’re stuck in Stockport.
Don’t forget to watch this!!
The change of sky colour at sunset (red nearest the sun, blue furthest away) is caused by Rayleigh scattering by atmospheric gas particles which are much smaller than the wavelengths of visible light. The grey/white colour of the clouds is caused by Mie scattering by water droplets which are of a comparable size to the wavelengths of visible light.
An electron microscope image of a human foetus.
Pictured here at 8 weeks, with a length of just 3cm, the nose, eyes and hands are easily visible.
(Science You Can Love, Neurons want food)
Zooming into the constellation Sagittarius.
1. A region of the Milky Way
2. A large portion of the sky very rich in nebulae and star clusters. For example the Lagoon, Trifid, Eagle and Omega nebulae are seen.
3. The field around the Lagoon and Trifid nebulae
4. The finest details of the Lagoon and Trifid nebulae. M8, an emission nebulae, lies at the left.
5. Close-up look of M20 where the three different types of nebula can be seen.
Credit: the members of the IAC astrophotography group.
Here are some asteroids viewed in a rotating frame of reference where Jupiter almost stands still. The Trojans, in green, are asteroids that stay near the Lagrange points 60° ahead or behind Jupiter. They go around the Sun once each time Jupiter orbits the Sun. But the Hildas, in purple, go around the Sun 3 times while Jupiter goes around twice. We say they’re in a 3:2 resonance with Jupiter.
The Hildas seem to be moving in a triangular pattern. But actually each one takes an elliptical orbit around the Sun. There are three kinds of ellipses. Two go farthest from the Sun near the Lagrange points, while one goes farthest from the Sun opposite Jupiter. Although the whole triangle of Hildas is nearly equilateral, it’s not quite. The side between the two Lagrange points is a bit different from the two other sides. You can also see the whole triangle pulsing as Jupiter moves in and out!
These animated gifs were made by Petr Scheirich, and you can have hours of fun looking at his website: http://sajri.astronomy.cz/asteroidgroups/groups.htm
There’s a lot to say about Trojans and Lagrange points, but let me talk about Hildas. Over 1,100 Hildas have been found, the being Hilda, named after the discoverer’s daughter. It’s big - 175 kilometers in diameter - but not very bright, because it’s made of ancient stuff containing lots of carbon, similar to the nucleus of a comet.
The Hildas don’t form a ‘true’ asteroid family, because they aren’t fragments of a single parent object. Instead, they’re a ‘dynamical’ family: they’re defined by having similar orbits. Any Hilda’s orbit has an eccentricity less than 0.3, an inclination less than 20°, and a semi-major axis between 3.7 AU and 4.2 AU. Remember, the semi-major axis of an ellipse is half the distance between the farthest points.
So, the Hildas are outside the main asteroid belt, which lies between the 4:1 resonance with Jupiter at 2.1 AU and the 2:1 resonance at 3.0 AU.
The density of Hildas near the triangle’s corners is more than twice the density on the sides. The reason is that the Hildas move more slowly when they’re farther from the Sun! So, they stay near the corners for an average of 5.0-5.5 years, but move along the sides of the triangle more quickly, for 2.5 to 3.0 years. The overall period of the Hildas is about 7.9 years, which is 2/3 the period of Jupiter.
Ten years ago today in 2004, NASA’s robotic exploration rover Spirit touched down on the surface of Mars. Consisting of two rovers, the Mars Exploration Rover Mission (MER) received reinforcements three weeks later when robotic exploration rover Opportunity made a successful landing on Martian soil. Opportunity is still exploring the Red Planet to this day, paving the way for the eventual landing of Curiosity years later in 2011.
"We succeeded beyond my wildest dreams, clearly both Spirit and Opportunity succeeded in their missions and have left a big impact for future study," stated Ray Arvidson, deputy principal investigator for the Mars Exploration Rover Mission.
Arvidson continues, “We will be analyzing data from the Spirit rover for years to come; we have a lot of information so we have a lot more to learn from its mission. These rovers set the bar really high in terms of robotic exploration. They were well tested and well designed.”
One of the groundbreaking geological discoveries was the observation of bright, white soil near Home Plate, a low plateau NASA identified for Spirit to explore upon landing on Mars. After the data was analyzed with the rover’s on board X-ray spectrometer, scientists determined that the material was nearly 100% pure silica; positive evidence that the Red Planet once was the home of ancient steam vents and hot springs, similar to those found here on Earth.
“The data from Spirit show us that Mars was a very different place in the past from what we see today. This surface area that Spirit explored had a lot of explosions as it was a hot, wet, watery place,” concluded Steve Squyres, principal investigator for MER.
Both designed for short, three-month long exploratory missions, Spirit and Opportunity have far surpassed NASA’s wildest dreams. Bruce Banerdt, NASA project scientist for the Mars Exploration Rover Mission, stated the following:
"Spirit faced a lot of challenges on Mars. When the wheel went out, we had to relearn how to drive the rover. It is truly remarkable what we were able to achieve with this rover with only five wheels."
Watch this short video, “The Legacy of Mars Rover Spirit”
The Legacy of Mars Rover Spirit
With a Penny4NASA, urge Congress to honor the legacy of Spirit with the continued exploration of Mars:
Let me Explain you a thing - T shirt - http://hereticwear.com/product/neil-degrasse-tyson-cosmos-t-shirt/
The Golden Ratio is Everywhere
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