Cepheid variable stars in spiral galaxy NGC 3021

This is a NASA/ESA 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).

Credit:

NASA, ESA and A. Riess (STScI/JHU)

About the Image

NASA press release
NASA caption
Id:opo0908a
Type:Collage
Release date:7 May 2009, 15:00
Size:2400 x 3000 px

About the Object

Name:NGC 3021
Type:• Local Universe : Star : Type : Variable
• Local Universe : Galaxy : Type : Spiral
• X - Stars Images/Videos
Distance:90 million light years

Colours & filters

BandWavelengthTelescope
Optical
V
555 nm Hubble Space Telescope
ACS
Infrared
I
814 nm Hubble Space Telescope
ACS
Infrared
H
1.6 μm Hubble Space Telescope
NICMOS

Image Formats

Large JPEG
1.5 MB
Screensize JPEG
373.0 KB

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