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).
Credits
NASA, ESA, and A. Riess (STScI/JHU)| About The Object | |
|---|---|
| Object Name | NGC 3021 |
| Object Description | Spiral Galaxy |
| R.A. Position | 09h 50m 57s.13 |
| Dec. Position | +33° 33' 12".71 |
| Constellation | Leo Minor |
| Distance | 92 million light-years (28 megaparsecs) |
| Dimensions | This image is roughly 1.5 arcminutes (41,000 light-years or 12.5 kiloparsecs) wide. |
| About The Data | |
| Data Description | Data from several HST proposals were used for this science. These include: , , , , and , PI: A. Riess (STScI/JHU). Data specific to observations of NGC 3021 are from HST proposals and 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). |
| Instrument | HST>NICMOS and HST>ACS/WFC |
| Exposure Dates | November 2005 - November 2006, Exposure Time: 23.8 hours (ACS), and October 2006 - March 2007, Exposure Time: 18.4 hours (NICMOS) |
| Filters | ACS: F555W (V) and F814W (I) NICMOS: F160W (H-band) |
| About The Image | |
| Compass Image |  |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
