by Ann » Fri Apr 29, 2016 5:08 am
APOD Robot wrote:
Why is the gamma-ray Moon so bright? High-energy charged particles streaming through the Solar System known as cosmic rays constantly bombard the lunar surface, unprotected by a magnetic field, generating the gamma-ray glow. Because the cosmic rays come from all sides, the gamma-ray Moon is always full and does not go through phases. The first gamma-ray image of the Moon was captured by the EGRET instrument onboard the Compton Gamma-ray Observatory, launched 25 years ago.
Okay.
Sorry. I couldn't resist. It's not that I don't find the gamma-ray bright Moon interesting, even though I already knew about its gamma-ray brightness and the reason for it (the Moon's lack of a magnetic field). But most people probably haven't heard about the gamma-ray bright Moon, and it is a good thing if the Astronomy Picture of the Day can educate people.
It's just that I'm underwhelmed by the picture. Yes, I know that this is what scientific pictures look like, except that this one has been colorized yellow and red, for the benefit of people who like to look at yellow and red. (And possibly for clarity, though I'm not so sure about that.)
I guess the message of this APOD is that it is good that the Earth has global magnetic field, and since a magnetic field may also be the prerequisite for a healthy atmosphere, it is good that the Earth has a magnetic field that gives our favorite planet a robust atmosphere. (Of course, Venus has a whopper of an atmosphere, which is so thick that it prevents the habitality of life as we know it on our sister planet. Yet Venus does not have much of a magnetic field, or at least I don't think so, so it's a mystery why it has such an enormous atmosphere.)
Oh well. I guess the lesson that can be learned from today's APOD is that it is good that the Earth is the Earth.
Okay.
Ann
[quote]APOD Robot wrote:
Why is the gamma-ray Moon so bright? High-energy charged particles streaming through the Solar System known as cosmic rays constantly bombard the lunar surface, unprotected by a magnetic field, generating the gamma-ray glow. Because the cosmic rays come from all sides, the gamma-ray Moon is always full and does not go through phases. The first gamma-ray image of the Moon was captured by the EGRET instrument onboard the Compton Gamma-ray Observatory, launched 25 years ago. [/quote]
Okay.
Sorry. I couldn't resist. It's not that I don't find the gamma-ray bright Moon interesting, even though I already knew about its gamma-ray brightness and the reason for it (the Moon's lack of a magnetic field). But most people probably haven't heard about the gamma-ray bright Moon, and it is a good thing if the Astronomy Picture of the Day can educate people.
It's just that I'm underwhelmed by the picture. Yes, I know that this is what scientific pictures look like, except that this one has been colorized yellow and red, for the benefit of people who like to look at yellow and red. (And possibly for clarity, though I'm not so sure about that.)
I guess the message of this APOD is that it is good that the Earth has global magnetic field, and since a magnetic field may also be the prerequisite for a healthy atmosphere, it is good that the Earth has a magnetic field that gives our favorite planet a robust atmosphere. (Of course, Venus has a whopper of an atmosphere, which is so thick that it prevents the habitality of life as we know it on our sister planet. Yet Venus does not have much of a magnetic field, or at least I don't think so, so it's a mystery why it has such an enormous atmosphere.)
Oh well. I guess the lesson that can be learned from today's APOD is that it is good that the Earth is the Earth.
Okay.
Ann