Image Credit & Copyright: NASA/ESA Hubble Space Telescope.
When the light from the galaxy in this image left and headed our way, the dinosaurs were still happily grazing on trees….and each other (depending on who you were). In fact they had roughly 35 million years of blissful feeding ahead of them before they observed an asteroid too closely about 65 million years ago. In fact, the 100 million years that it takes light to travel from this galaxy to Earth spans more than half of the 165 million years that the dinosaurs existed. So much has changed here in that time and one can only fantasize of the changes that have taken place on that island in that time as well.
This galaxy is cataloged as New General Catalog 3021 (NGC 3021) and it resides in the constellation Leo Minor and as I stated above, it’s roughly 100 million light years away. The two bright stars in this image aren’t stars in that galaxy but stars in our own Milky Way that we have to look beyond as if we’re observing something outside through a screen door.
This galaxy also boasts Cepheid variable stars which are widely utilized as the cosmic measuring sticks in astronomy and cosmology for their precise brightness and clock-like pulses. They also serve to calibrate the brightness to Type-1a supernovae which can allow us to measure objects even more distant than what Cepheid variables allow. The last Type-1a in NGC 3021 was SN 1995 al back in 1995. That supernova data was actually used in 2009 to help redefine the Hubble Constant and thus helps us understand more accurately how fast the universe is expanding away from us.
One final thought. In this image you not only see two bright Milky Way stars but you also see what looks like NGC 3021 shedding off material. That material is actually thousands of individual galaxies, millions to billions of light years beyond NGC 3021. If we could look at this patch of sky today in real time none of the galaxies in this image would be there. Even when this image was captured, if you were on NGC 3021 those background galaxies looked very different to them than they do to us in the image. The layers of time and distance that we see here from a couple of Milky Way stars right on past NGC 3021 to what appear to be young galaxies is staggering. Then again, what we see as young galaxies are actually today fully developed galaxies and they see us as toddlers and themselves, as we see ourselves.
NAME: NGC 3021.
WHAT IS IT?: Spiral galaxy.
HOW FAR AWAY IS IT?: Roughly 100 million light years.
HOW BIG IS IT?: Roughly 40,000 light years in diameter.
APPARENT MAGNITUDE: Pretty dim 12 or +12.
DISCOVERY?: December 7, 1785 by Sir. William Herschel.
WHERE IS IT? (General): Constellation Leo Minor.
WHERE IS IT? (Exact RA/DEC J2000): RA 09h 50m 57.2s / DEC +33d 33’ 13”.
European Space Agency (ESA) Hubble page for this image: https://www.spacetelescope.org/images/potw1513a/
NASA page for this image: https://www.nasa.gov/content/goddard/hubble-view-of-a-cosmological-measuring-tape