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Astronomy Picture of the Day 6-05-02
NASA ^
| 6-05-02
| Robert Nemiroff and Jerry Bonnell
Posted on 06/05/2002 5:02:54 PM PDT by 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 June 5

NGC 3621: Far Beyond the Local Group
Credit: F. Bresolin, R.-P. Kudritzki, R. Mendez (Institute for Astronomy, Univ. Hawaii)
Explanation: Far beyond the local group of galaxies lies NGC 3621, some 22 million light-years away. Found in the serpentine southern constellation Hydra, the loose spiral arms of this gorgeous island universe are loaded with luminous young star clusters and dark dust lanes. Still, for earthbound astronomers NGC 3621 is not just another pretty face-on spiral galaxy. Some of its brighter stars have been used as standard candles to establish important estimates of extragalactic distances and the scale of the Universe. This color picture was constructed from astronomical image data recorded with the Very Large Telescope Antu, at Paranal Observatory in Chile. At the original resolution, individual, hot supergiant stars can be identified and studied across NGC 3621.
TOPICS: Astronomy; Astronomy Picture of the Day; Science
KEYWORDS: astronomy; distant; dust; galaxy; gas; image; photography; star; stars; telescope; universe
The most common way to measure the distance to a reasonably close galaxy is the "standard candle" method.
Some very luminous stars change in brightness at a rate which corresponds to their exact luminosity.
These stars are known as Cepheid variables, after the archetype discovered in 1912 in the constellation Cepheus.
The astronomer responsible for the breakthrough was
Henrietta Leavitt.
With the help of Miss Leavitt's breakthrough discovery, astronomer
Edwin Hubble in 1923-1924 provided proof that
"spiral nebulae" were really galaxies; island universes like our own Milky Way.
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To: petuniasevan
22 million light years!
3
posted on
06/05/2002 5:12:12 PM PDT
by
aomagrat
To: petuniasevan
Very interesting.
I always learn something from APOD.
To: petuniasevan
Some very luminous stars change in brightness at a rate which corresponds to their exact luminosity.That ring a bell. My memory's getting rusty so please correct me if I'm wrong, but didn't Milne later use this same light oscillation and the red shift to demonstrate that the nebulae were once confined to one region of space? Therefore, the most distant galaxies appear to be accelerating away from us.
5
posted on
06/05/2002 6:58:11 PM PDT
by
Helix
To: petuniasevan
The world sure has gotten complicated since Cepheid variables were discovered. That was the Golden Age of observational astronomy. Now raw data is coming in much faster than it can be analyzed and astronomers are losing ground. The new big telescopes are awesome, Hubble isn't the only big tube in town.
To: petuniasevan
'Gilligan's Island Universe' bump. ;^)
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