Feeds

How far can the naked eye see?

Star gazing

Intelligent flash storage arrays

Also in this week's column:

How far can the naked eye see?

The human eye can see an almost unlimited distance. Looking up into the sky on a very clear night, the Triangulum Galaxy can sometimes be seen. This is a distance of 3.14 million light years. The Andromeda Galaxy is also sometimes visible. This is a distance of 2.5 million light years.

However, it must be pointed out that when we see these galaxies what we actually "see" is something at a somewhat lesser distance. What we "see" is light from the far away object rather than the object itself. What happens is that light coming from the object strikes our optic nerve. The optic nerve signals the brain. The brain then interprets this message and forms an image. The brighter the object, the farther away it can be from us and still be "seen".

The star, Rigel, is many times brighter than another star, Alpha Centauri, yet Alpha Centauri is many times closer.

According to Dr Brent Archinal of the Astrogeology Team of the US Geological Survey in Flagstaff, Arizona writing in the May, 1997 issue of Astronomy, the human eye can see about 2,500 stars in the clearest of night skies. But usually only about 1,500 to 2,000 stars can be seen due to weather, pollution, etc, and fewer still in night skies of cities due to the additional factor of city lights.

Five planets can be seen from earth with the naked eye under the best of circumstances: Mercury, Venus, Mars, Jupiter, and Saturn.

Stephen Juan, Ph.D. is an anthropologist at the University of Sydney. Email your Odd Body questions to s.juan@edfac.usyd.edu.au

Intelligent flash storage arrays

More from The Register

next story
MARS NEEDS WOMEN, claims NASA pseudo 'naut: They eat less
'Some might find this idea offensive' boffin admits
LOHAN crash lands on CNN
Overflies Die Welt en route to lively US news vid
Comet Siding Spring revealed as flying molehill
Hiding from this space pimple isn't going to do humanity's reputation any good
Experts brand LOHAN's squeaky-clean box
Phytosanitary treatment renders Vulture 2 crate fit for export
No sail: NASA spikes Sunjammer
'Solar sail' demonstrator project binned
Carry On Cosmonaut: Willful Child is a poor taste Star Trek parody
Cringeworthy, crude and crass jokes abound in Steven Erikson’s sci-fi debut
Origins of SEXUAL INTERCOURSE fished out of SCOTTISH LAKE
Fossil find proves it first happened 385 million years ago
prev story

Whitepapers

Cloud and hybrid-cloud data protection for VMware
Learn how quick and easy it is to configure backups and perform restores for VMware environments.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Three 1TB solid state scorchers up for grabs
Big SSDs can be expensive but think big and think free because you could be the lucky winner of one of three 1TB Samsung SSD 840 EVO drives that we’re giving away worth over £300 apiece.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.