April 21, 2014 - Variations on a Star

Variations on a Star This spectacular group of young stars is the open star cluster NGC 3766 in the constellation Centaurus. Observations of more than 3,000 stars in this cluster over the course of seven years have shown that thirty-six of them are of a new and unknown class of variable star. The stars in question vary their brightness by a slight amount—one-tenth of one percent—for periods of between two and twenty hours. The stars are somewhat hotter and brighter than our Sun, but otherwise are apparently unremarkable. The new class of stars has not been named, nor is it known yet just why these variations occur. One clue may lie in the fact that some of these stars spin at speeds that are more than half of their critical velocity, the threshold at which stars become unstable and throw material off into space.

Image Credit: ESO

Weekly Calendar

April 21-27, 2014

Holidays - Sky Events - Space History

 

Monday 21

Easter Monday (Canada)

Lyrid meteor shower

1997: Cremated remains of 24 people launched into orbit aboard Pegasus rocket in first space funeral

Tuesday 22

Last Qtr Moon 3:52 AM ET
Moon at perigee
Lyrid meteor shower

2010: X-37B spacecraft launched

Wednesday 23

1858: Max Planck born
1962: Ranger 4 launched
1963: M2-F1 lifting body first free flight
1996: Priroda module launched to Mir space station

Thursday 24

Neptune 5° south of Moon

1970: China becomes fifth nation to launch its own satellite
1990: STS-31 Discovery launched

Friday 25

Venus 4° south of Moon
Mercury in superior conjunction

1962: Second Block I Saturn C-1 (SA-2) launched
1990: Hubble Space Telescope deployed
2003: ISS Expedition Seven crew launched on Soyuz TMA-2

Saturday 26

1920: Shapley-Curtis debate on the nature and distance of spiral nebulae
1993: STS-55 Columbia launched

Sunday 27

Uranus 2° south of Moon