Deep fields & lensing
Cepheid Variable Stars in Spiral Galaxy NGC 3021
May 7, 2009 · NASA · Leo Minor
Zoom to full resolution See where it is in the 3D sky Original on NASA ↗
This is a Hubble Space Telescope photo of the spiral galaxy NGC 3021. This was one of several hosts of recent Type Ia supernovae observed by astronomers to refine the measure of the universe's expansion rate, called the Hubble constant. Hubble made precise measurements of Cepheid variable stars in the galaxy, highlighted by green circles in the four inset boxes. These stars pulsate at a rate that is matched closely to their intrinsic brightness. This makes them ideal for measuring intergalactic distances. The Cepheids are used to calibrate an even brighter milepost marker that can be used over greater distances, a Type Ia supernova. The supernova was observed in the galaxy in 1995. The images in the boxes were taken with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).
About the data
Data from several HST proposals were used for this science. These include: 9352 , 9728 , 10189 , 10339 , and 10802 , PI: A. Riess (STScI/JHU). Data specific to observations of NGC 3021 are from HST proposals 10802 and 10497 PI: A. Riess (STScI/JHU).
The science team includes: A. Riess (STScI/JHU), L. Macri (Texas A&M University), S. Casertano and M. Sosey (STScI), H. Lampeitl (STScI/University of Portsmouth, UK), H. Ferguson (STScI), A. Filippenko (University of California, Berkeley), S. Jha (Rutgers University), W. Li and R. Chornock (University of California, Berkeley), and D. Sarkar (University of California, Irvine).
