Skip to comments.Astronomy Picture of the Day 5-08-02
Posted on 05/08/2002 5:09:37 AM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2002 May 8
Explanation: It was a quiet day on the Sun. The above image shows, however, that even during off days the Sun's surface is a busy place. Shown in ultraviolet light, the relatively cool dark regions have temperatures of thousands of degrees Celsius. Large sunspot group AR 9169 is visible as the bright area near the horizon. The bright glowing gas flowing around the sunspots has a temperature of over one million degrees Celsius. The reason for the high temperatures is unknown but though to be related to the rapidly changing magnetic field loops that channel solar plasma. Sunspot group AR 9169 moved across the Sun during 2000 September and decayed in a few weeks.
This beautiful image is courtesy of the Transition Region and Coronal Explorer. TRACE is a mission of the Stanford-Lockheed Institute for Space Research (a joint program of the Lockheed-Martin Advanced Technology Center's Solar and Astrophysics Laboratory and Stanford's Solar Observatories Group ), and part of the NASA Small Explorer program.
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old inside joke, hehe
Apologies to 'tunia! &;-)
Beautiful picture of the Sun.
Beautiful picture! Did you know that some insects can see well into the UV range? I wonder if that was ever a useful ability on Earth.
This is a comparison of wavelengths visible to humans and bees.
The range of vision for the bee and butterfly extends into the ultraviolet.
The petals of the flowers they pollinate have special ultraviolet patterns
which guide the insects deep into the flower.
This doesn't contradict my earlier assertion that UV imaging must be done from orbit; obviously a little UV gets through. It's what gives you a tan (or sunburn). It's just that 99% of "soft" UV is blocked, and higher-energy "hard" UV is 100% blocked, as are X-Rays.
Same daylilies in UV light.
Although we can't be sure exactly HOW UV light appears to bees, it seems that the UV image above shows dark central regions in the flowers which guide the bee to the nectar.
To be honest, I had wandered off track and into a supposition about the stable atmosphere we enjoy today.
I vaguely remembered reading about a theory of Fred Hoyle's on the ability of Drosophila (I think) to see the very short (980 A)wavelengths of UV which, according to him, could never have penetrated the atmosphere during the time that insects have been present on Earth. Therefore, he believed they were under no selective pressure to develop such an ability. He also thought the insects could not have survived the light's mutagenic effects.
These assertions always seemed a little over-the-top to me since we've witnessed how much the atmosphere can change in just the few years scientists been studying it. The constant change of the "hole" in the ozone, for example. And although UV light is a mutagen, all organisms have some ability to repair the damage. It seems possible that, at one time, shorter UV rays were able to penetrate the atmosphere and the ability to see these wavelengths was used by those insects.
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