Astronomy Picture of the Day 7-06-02

NASA ^ | 7-06-02 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

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 July 6

Io: Moon Over Jupiter
Credit: Cassini Imaging Team, Cassini Project, NASA

Explanation: How big is the Jovian moon Io? The most volcanic body in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite. Gliding past Jupiter at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view of active Io with the largest gas giant as a backdrop, offering a stunning demonstration of the ruling planet's relative size. Although in the picture Io appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter. That puts it nearly 350,000 kilometers above Jupiter's cloud tops, roughly equivalent to the distance between Earth and Moon. The Cassini spacecraft itself was about 10 million kilometers from Jupiter when recording the image data.

[petuniasevan]

Astronomy fun fact:

Excluding the sun, Jupiter contains more mass than the rest of the Solar System combined!

Get on the APOD PING list!

[petuniasevan]

APOD PING!

[MeekOneGOP]

Beautiful picture. Thanks!

[dansangel]

Truly breathtaking....thanks for the wonderful eye-opener this morning!

[sleavelessinseattle]

P7, you've outdone yourself! If ever anyone needed a reminder of how beautifull the Universe was...I'd send them to APOD, and then Baskin and Robbins! 2T Czech it OUT!

[MozartLover]

Incredible. Thank you!

[MozartLover]

"If ever anyone needed a reminder of how beautifull the Universe was...I'd send them to APOD, and then Baskin and Robbins! "

LOL! I'll share this one with my son. He's over at BR at this very moment, scooping up double-dips and blending smoothies.:)

[Sock]

I love these pictures.

On the first day of summer (the longest day of the year) the weatherman in Chicago announced that on that day there would be 24 hours of sunshine at the North Pole. I apologize if this question has been asked before and I know it's off topic, but does that mean that instead of rising in the East and setting in the West, at the North Pole the sun would make a complete circle in the sky at some small angle above the horizon?

Thanks in advance.

[petuniasevan]

Yes, exactly.

At the North Pole (90 degrees north) the axial tilt of the Earth is at its greatest extent facing the Sun on June 20/21.
The Sun will appear to circle the horizon at an angle of 23.5 degrees above the horizon there.

The opposite applies at winter solstice December 21/22.

At various latitudes, the apparent solar track is shown below for equinox and northern summer solstice..

[petuniasevan]

But also your weatherman didn't give you QUITE enough information. At the North Pole you wouldn't have just 24 HOURS of daylight, you'd have 6 MONTHS of sunshine. Sunrise there is about March 21, and sunset is about September 21. Night prevails after a couple of weeks of twilight, until March comes and the first faint light appears again.

[petuniasevan]

On the Arctic Circle, 67.5 degrees north latitude, June 21 is the only day the Sun stays up 24 hours. Technically. Actually, the solstice and refraction through the Earth's atmosphere combine to make the Sun appear - several days in a row - to be up 24 hours.

At this location, the Sun will be at an angle of 47 degrees above the horizon at local noon, and dip to the horizon at midnight.

[petuniasevan]

Dang! Make the Arctic Circle 66.5 degrees north latitude. Sheesh.

[Joan912]

I am utterly speechless.